Alesis Computer Monitor M1 Active Mk2 User Manual

REFERENCE MANUAL  
©2001 ALESIS CORPORATION  
 
Contents/Safety Warnings  
CONTENTS  
Introduction  
2
IMPORTANT SAFETY INSTRUCTIONS......................................................3  
Safety symbols used in this product  
3
5
Instructions de Sécurité Importantes (French)  
Information to the User for Class A Digital Device (FCC Part 15, Class A) 7  
CE Declaration of Conformity  
8
ABOUT THE M1 ACTIVE MK2 ...............................................................9  
Unpacking and Inspection  
Inside your new speakers  
About Nearfield monitoring  
9
10  
15  
SPEAKER INSTALLATION.................................................................... 17  
Avoiding reflections in the studio  
Stereo nearfield placement of the M1 Active Mk2  
Connections  
17  
20  
26  
28  
Setting the Input Level control  
SURROUND SOUND ............................................................................ 31  
About surround sound  
31  
32  
33  
34  
Center speakers in music mixes  
Placement of the center M1 Active Mk2 speaker in the studio  
Placement of rear surrounds  
Mixing for discrete six channel reproduction: matched vs. specialized speakers  
37  
TROUBLESHOOTING ...........................................................................39  
Troubleshooting Index  
Maintenance  
39  
40  
SPECIFICATIONS ................................................................................42  
Enclosure  
42  
42  
43  
43  
43  
43  
Transducers  
Crossover section  
Amplifier Section  
Acoustic Section  
General  
INDEX.............................................................................................. 44  
ALESIS LIMITED WARRANTY..............................................................45  
M1 Active Mk2 Reference Manual  
1
 
Contents/Safety Warnings  
INTRODUCTION  
Thank you for purchasing the Alesis M1 Active Mk2 Biamplified Reference  
Monitors. To take full advantage of the M1 Active Mk2’s operation, and to  
enjoy long and trouble-free use, please read this user’s manual carefully. We  
value any comments you may have about this monitor system, this manual,  
your Alesis dealer or our factory service. Please take a minute now to fill out  
your warranty card and tell us what you think.  
HOW TO USE THIS MANUAL  
This manual is divided into the following sections describing the various  
features of the M1 Active Mk2. Though we recommend you take time to read  
through the entire manual once carefully, those having general knowledge  
about monitors should use the table of contents to reference specific  
functions.  
Chapter 1: About the M1 Active Mk2. Engineering specifications and  
reasons why nearfield monitors have become so popular.  
Chapter 2: Speaker Installation. This chapter explains how to connect the  
M1 Active Mk2s to a mixer or other line-level source and discusses proper  
speaker placement for stereo operation.  
Chapter 3: Surround Sound. If you are using the M1 Active Mk2 speakers in  
a multichannel surround sound setup, you’ll find helpful setup and operation  
information here.  
Chapter 4: Troubleshooting. This chapter contains troubleshooting tips and  
service information should problems occur.  
When something important appears in the manual, an icon (like the  
one on the left) will appear in the left margin. This symbol indicates  
that this information is vital when operating the M1 Active Mk2s.  
2
M1 Active Reference Manual  
 
Contents/Safety Warnings  
IMPORITNASNTTRUSCATFIOENTYS  
SAFETY SYMBOLS USED IN THIS PRODUCT  
This symbol alerts the user that there are important operating and  
maintenance instructions in the literature accompanying this unit.  
PLEASE FOLLOW THESE PRECAUTIONS WHEN USING THIS  
PRODUCT:  
1. Read these instructions.  
2. Keep these instructions.  
3. Heed all warnings.  
4. Follow all instructions.  
5. Do not use this apparatus near water.  
6. Clean only with a damp cloth. Do not spray any liquid cleaner onto the  
speakers or rear panel, as this may damage the speakers, controls or cause  
a dangerous condition.  
7. Install in accordance with the manufacturer's instructions.  
8. Do not install near any heat sources such as radiators, heat registers,  
stoves, or other apparatus (including amplifiers) that produce heat.  
9. Do not defeat the safety purpose of the polarized or grounding-type plug.  
A polarized plug has two blades with one wider than the other. A  
grounding-type plug has two blades and a third grounding prong. The  
wide blade or the third prong are provided for your safety. When the  
provided plug does not fit into your outlet, consult an electrician for  
replacement of the obsolete outlet.  
M1 Active Mk2 Reference Manual  
3
 
Contents/Safety Warnings  
10. Protect the power cord from being walked on or pinched, particularly at  
plugs, convenience receptacles, and the point where they exit from the  
apparatus.  
11. Use only attachments or accessories specified by the manufacturer.  
12. Use only with a cart, stand, bracket, rack, or table designed for use with  
professional audio or music equipment. In any installation, make sure  
that injury or damage will not result from cables pulling on the apparatus  
and its mounting. If a cart is used, use caution when moving the  
cart/apparatus combination to avoid injury from tip-over.  
13. Unplug this apparatus during lightning storms or when unused for long  
periods of time.  
14.  
Refer all servicing to qualified service personnel. Servicing is  
required when the apparatus has been damaged in any way, such as when  
the power-supply cord or plug is damaged, liquid has been spilled or  
objects have fallen into the apparatus, the apparatus has been exposed to  
rain or moisture, does not operate normally, or has been dropped.  
15. This product may be capable of producing sound levels that could cause  
permanent hearing loss. Do not operate for a long period of time at a high  
volume level or at a level that is uncomfortable. If you experience any  
hearing loss or ringing in the ears, you should consult an audiologist.  
4
M1 Active Reference Manual  
 
Contents/Safety Warnings  
INSTRUCTIONS DE SÉCURITÉ IMPORTANTES (FRENCH)  
SYMBOLES UTILISÉS DANS CE PRODUIT  
Ce symbole alèrte l’utilisateur qu’il existe des instructions de fonctionnement et  
de maintenance dans la documentation jointe avec ce produit.  
Ce symbole avertit l’utilisateur de la présence d’une tension non isolée à l’intérieur de  
l’appareil pouvant engendrer des chocs électriques.  
VEUILLEZ SUIVRE CES PRÉCAUTIONS LORS DE  
LUTILISATION DE LAPPAREIL:  
1. Lisez ces instructions.  
2. Gardez ces instructions.  
3. Tenez compte de tous les avertissements.  
4. Suivez toutes les instructions.  
5. N’utilisez pas cet allareil à proximité de l’eau.  
6. Ne nettoyez qu’avec un chiffon humide. Ne pas vaporiser de liquide nettoyant sur l’appareil,  
cela pourrait abîmer les contrôles de la face avant ou engendrer des conditions dangeureuses.  
7. Installez selon les recommandations du constructeur.  
8. Ne pas installer à proximilé de sources de chaleur comme radiateurs, cuisinière ou autre  
appareils (don’t les amplificateurs) produisant de la chaleur.  
9. Ne pas enlever la prise de terre du cordon secteur. Une prise murale avec terre deux broches  
et une troisièrme reliée à la terre. Cette dernière est présente pour votre sécurité. Si le cordon  
secteur ne rentre pas dans la prise de courant, demandez à un électricien qualifié de  
remplacer la prise.  
10. Evitez de marcher sur le cordon secteur ou de le pincer, en particulier au niveau de la prise,  
et aux endroits où il sor de l’appareil.  
11. N’utilisez que des accessoires spécifiés par le constructeur.  
12. N’utilisez qu’avec un stand, rack ou table conçus pour l’utilisation d’audio professionnel ou  
instruments de musique. Dans toute installation, veillez de ne rien endommager à cause de  
câbles qui tirent sur des appareils et leur support.  
13. Débranchez l’appareil lors d’un orage ou lorsqu’il n’est pas utilisé pendant longtemps.  
14. Faites réparer par un personnel qualifié. Une réparation est nécessaire lorsque l’appareil a  
été endommagé de quelque sorte que ce soit, par exemple losrque le cordon secteur ou la  
prise sont endommagés, si du liquide a coulé ou des objets se sont introduits dans l’appareil,  
si celui-ci a été exposé à la pluie ou à l’humidité, ne fonctionne pas normalement ou est  
tombé.  
15. Cet appareil produit de la chaleur en fonctionnement normal. Si cet appareil est utilisé dans  
un rack, veillez à sa bonne ventilation lors de son utilisation. Ne pas faire fonctionner dans  
un rack fermé. S’il y a d’autres appareils dans le rack générant beaucoup de chaleur,éloignez  
les. Ne pas intercaler cetappareil entre deux appareils produisant beaucoup de chaleur.  
16. Ce produit, utilisé avec un amplificateur et un casqueou des enceintes, est capable de  
produite des niveaux sonores pouvant engendrer une perte permanente de l’ouïe. Ne  
l’utilisez pas pendant longtemps à un niveau sonore élevé ou à un niveau non confortable. Si  
vous remarquez une perte de l’ouïe ou un bourdonnement dans les oreilles, consultez un  
spécialiste.  
M1 Active Mk2 Reference Manual  
5
 
Contents/Safety Warnings  
BEIM BENUTZEN DIESES PRODUKTES BEACHTEN SIE  
BITTE DIE FOLGENDEN SICHERHEITSHINWEISE: (GERMAN)  
1. Lesen Sie die Hinweise.  
2. Halten Sie sich an die Anleitung.  
3. Beachten Sie alle Warnungen.  
4. Beachten Sie alle Hinweise.  
5. Bringen Sie das Gerät nie mit Wasser in Berührung.  
6. Verwenden Sie zur Reinigung nur ein weiches Tuch. Sprühen Sie keine flüssiger Reinigerauf  
die Oberfläche, dies könnte zur Beschädigung der Vorderseite führen und auch weitere  
Schäden verursachen.  
7. Halten Sie sich beim Aufbau des Gerätes an die Angaben des Herstellers.  
8. Stellen Sie das Gerät nich in der Nähe von Heizkörpern, Heizungsklappen oder anderen  
Wärmequellen (einschließlich Verstärkern) auf.  
9. Verlegen Sie das Netzkabel des Gerätes niemals so, daß man darüber stolpern kann oder daß  
es gequetscht wird.  
10. Benutzen Sie nur das vom Hersteller empfohlene Zubehör.  
11. Verwenden Sie ausschließlich Wagen, Ständer, Racks oder Tische, die speziell für  
professionelle Audio- und Musikinstrumente geeignetsind. Achten Sie immer darauf, daß  
die jeweiligen Geräte sicher installiert sind, um Schäden und Verletzungen zu vermeiden.  
Wenn Sie einen Rollwagen benutzen, achten Sie darauf, das dieser nicht umkippt, um  
Verletzungen auszuschließen.  
12. Ziehen Sie während eines Gewitters oder wenn Sie das Gerät über einen längeren Zeitraum  
nicht benutzen den Netzstecher aus der Steckdose.  
13. Die Wartung sollte nur durch qualifiziertes Fachpersonal erfolgen. Die Wartung wird  
notwendig, wenn das Gerät beschädigt wurde oder aber das Stromkabel oder der Stecker,  
Gegenstände oder Flüssigkeit in das Gerät gelangt sind, das Gerät dem Regen oder  
Feuchtigkeit ausgesetzt war und deshalbnicht mehr normal arbeitet oder heruntergefallen  
ist.  
14. Bei normalem Betrieb des Gerätes kommt es zu Wärmeentwicklungen. Wenn Sie das Gerät  
in einem Rack eingebaut haben, sollte während des Betriebes die Zufuhr von Kühlluft stets  
gewährleitstet sein. Arbeiten Sie nie beigeschlossenem Rack. Bei mehreren Rackgeräten  
sollten diese mit einem geringen abstand voneinander eingebaut werden. Stapeln Sie dieses  
Gerät nicht zwischen Geräten mit hoher Wärmeentwicklung.  
15. Dieses Produkt kann in Verbindung mit einem Verstärker und Kopfhörern oder  
Lautsprechern Lautstärkepegel erzeugen, die anhaltende Gehörschäden verursachen.  
Betreiben Sie es nicht über längere Zeit mit hoher Lautstärke oder einem Pegel, der Ihnen  
unangenehm is. Wenn Sie ein Nachlassen des Gehörs oder ein Klingeln in den Ohren  
feststellen, sollten Sie einen Ohrenarzt aufsuchen.  
6
M1 Active Reference Manual  
 
Contents/Safety Warnings  
INFORMATION TO THE USER FOR CLASS A DIGITAL  
DEVICE (FCC PART 15, CLASS A)  
This equipment has been tested and found to comply with the limits for a  
class A digital device pursuant to Part 15 of the FCC Rules. These limits are  
designed to provide reasonable protection against harmful interference when  
the equipment is operated in a commercial environment. This equipment  
generates, uses and can radiate radio frequency energy and, if not installed  
and used in accordance with the instructions, may cause interference to radio  
communications. Operation of this equipment in a residential area is likely to  
cause interference in which case the user will be required to correct the  
interference at his own expense.  
The user is cautioned that changes and modifications made to the equipment  
without the approval of manufacturer could void the user’s authority to  
operate this equipment.  
Use only shielded and grounded cables with this equipment to ensure  
compliance with FCC Rules.  
INDUSTRY CANADA (DIGITAL APPARATUS)  
INTERFERENCE-CAUSING EQUIPMENT STANDARD  
ICES-003 ISSUE 2  
This Class A digital apparatus meets all requirements of the Canadian  
Interference-Causing Equipment Regulations.  
M1 Active Mk2 Reference Manual  
7
 
Contents/Safety Warnings  
CE DECLARATION OF CONFORMITY  
This product conforms to current applicable CE standards for safety. For a  
detailed description of the standards used, please see the web site Alesis.com.  
8
M1 Active Reference Manual  
 
About the M1 Active Mk2  
CHAPTER 1  
ABOUT THE M1 ACTIVE MK2  
UNPACKING AND INSPECTION  
Your M1 Active Mk2 Biamplified Reference Monitors were packed carefully  
at the factory, and the shipping carton was designed to protect the speakers  
during shipping. Please retain this container in the highly unlikely event that  
you need to return the speakers for servicing.  
The shipping carton should contain the following items:  
• This instruction manual  
• M1 Actives with the same serial numbers as shown on the shipping  
cartons  
• Two AC power cords (NEMA to CEE type)  
• Alesis warranty card  
• Two pieces of adhesive-backed non-skid foam  
It is important to register your purchase; if you have not already  
filled out your warranty card and mailed it back to Alesis, please  
take the time to do so now.  
The M1 Active Mk2s are designed as mirror-imaged pairs. If you have  
received a pair where the tweeters are both on the same side, contact your  
dealer immediately.  
M1 Active Mk2 Reference Manual  
9
 
About the M1 Active Mk2  
INSIDE YOUR NEW SPEAKERS  
If you’re in a hurry to get started, skip ahead to Chapter 2,  
“Speaker Installation”, for connection and placement tips.  
ABOUT POWERED MONITORS  
The M1 Active Mk2s combine a speaker and amplifiers in the same compact  
cabinet. Powered monitors are growing in popularity over the traditional  
separate amplifier and speakers for a number of reasons, convenience and  
ease of hookup being only one of them. You can connect a powered speaker  
directly to any line-level source (normally, the control room output of a  
mixer) simply by connecting a patch cord.  
Another benefit is improved sound quality. With careful design, the speaker,  
amplifier and electronic crossover can be optimised for each other. The M1  
Active Mk2s are biamplified, meaning that low frequencies and high  
frequencies are handled not only by separate speakers (the tweeter and the  
woofer), but by separate amplifiers. A pair of M1 Active Mk2s contain a total  
of four power amplifiers. Because of the increased efficiency of  
biamplification, these are much louder than a single-channel power amplifier  
of the same wattage feeding a passive crossover, as in other designs. New  
technology makes it possible to make these high-wattage amplifiers small  
enough to fit inside the speaker cabinet, with very little weight or size gain.  
Since the M1 Active Mk2s are self-powered, DO NOT connect them to  
the speaker output of another amplifier (such as a powered mixer or hi-  
fi receiver). Connect them only to the line-level outputs of such devices  
(+4 dBu nominal, +24 dBu maximum).  
10  
M1 Active Reference Manual  
 
About the M1 Active Mk2  
TONE  
Tonally, every effort has been made to create a powered monitor that is as  
linear as possible, representing a flat frequency response from 50Hz to 20KHz  
2dB. (see p. 21) Additionally, the use of electronic crossovers within the  
critical upper midrange frequencies has reduced phase and time delay  
anomalies often associated with passive crossovers. By including discrete  
woofer and tweeter amplifiers and application-specific electronic high and  
low pass crossover filters in the same enclosure the tonal accuracy of the M1  
Active Mk2 will always remain constant.  
ABOUT THE DRIVERS  
The M1 Active Mk2’s 6.5” woofer cone is made of proprietary non-woven  
carbon fiber. This material is 25% lighter than polypropylene with twice the  
stiffness for quicker transient response in the low-to-midbass region and  
vastly improved midrange intelligibility (over polypropylene at 2000 Hz).  
The non-woven carbon fiber cone, along with the closed cell synthetic rubber  
surround, are both nearly impervious to ozone, direct sunlight, heat and  
humidity. Therefore, after an initial break-in period, the sound should remain  
virtually unchanged for the life of the product.  
Alesis’ proprietary-design tweeter features a special wave guide baffle to  
improve polar response, a silk dome, and low viscosity ferrofluid formulated  
specifically to retain the best balance of transient response to power handling.  
The shielded tweeter utilizes a vented pole piece with a separate rear  
chamber to lower the free air resonance. The low 2000Hz crossover point of  
this tweeter produces a very widely dispersed, low-distortion signal within  
the critical midrange frequencies. It is these frequencies which are often the  
most problematic to get “right” during a mix. The tweeter is designed for an  
optimal response for non-fatiguing, long term, high level, nearfield  
mixdowns. This design results in a flat, linear mix when played back on home  
or car systems from appropriate distances.  
MAGNETIC SHIELDING  
Your M1 Active Mk2s are at home in recording environments wherein video  
is a major component. They are magnetically shielded for use in fairly close  
proximity (3” minimum) to a computer monitor or video screen. (Non-  
shielded components can make the colors of a screen “smear” or appear out  
of focus if the speaker is too close.) Magnetic shielding was designed into  
both the woofer and the tweeter from the beginning so that the system  
exhibits about low magnetic leakage. Shielding of both the woofer and the  
tweeter is accomplished by the use of a second opposing-field-oriented  
“bucking” magnet.  
M1 Active Mk2 Reference Manual  
11  
 
About the M1 Active Mk2  
THE M1 ACTIVE MK2 BI-AMPLIFIERS & ELECTRONIC  
CROSSOVERS  
The M1 Active Mk2 uses a 75W woofer amp and a 25W tweeter amp along  
with 4th order high and low pass electronic crossover filters centered at  
2000Hz. Electronic crossovers, which separate the frequencies before being  
sent to the amplifiers, have fewer phase problems and less power loss than  
the traditional passive crossover used after the amplifier. Fourth-order filters  
are steep (24 dB per octave), which minimizes the interaction between woofer  
and tweeter near the crossover point. Additionally, the high pass (tweeter)  
section of this system employs an electronic time alignment circuit. Thus the  
“launch” of frequencies from both the woofer and the tweeter will originate  
at exactly the same time.  
There are several advantages to using built-in amplifiers and active  
(electronic) crossovers versus a passive network system, most of which have  
been previously enumerated in Vance Dickason’s “Loudspeaker Design  
Cookbook”:  
Lower intermodulation distortion due to amplifier operation over a more  
narrow bandwidth. Also, clipping caused by low frequency overload is  
reduced, being limited to only one driver within a two driver system.  
Increased dynamic range. The M1 Active Mk2’s 75W and 25W amplifiers  
in their bi-amp setup will clip at about the same levels as one 200W  
amplifier operating into a passive crossover.  
Improved transient response.  
Better amplifier/speaker coupling for woofers.  
Better crossover performance working into a constant impedance load.  
Better subjective sound quality than high level (passive) networks.  
Easier control over driver sensitivity differences.  
Easier manipulation of phase, time delay, resonance, and various kinds of  
shaping, contouring and equalization.  
Specifically in the case of the M1 Active Mk2, the wide, mid-frequency  
polar response of the tweeter can be utilized down to a low 2000 Hz  
thereby mating more cohesively with the 6.5" non-woven carbon fiber  
(NWCF) woofer. This low crossover point is only possible through the use  
of a steep, electronic fourth-order (24 dB per octave rolloff) high pass filter.  
12  
M1 Active Reference Manual  
 
About the M1 Active Mk2  
THE M1 ACTIVE MK2 POWER SUPPLY  
The M1 Active Mk2 employs a regulated switching power supply. This type  
of supply has previously only been available in amplifiers sold at the very  
high end of the Pro Audio market.  
Most power amp customers are familiar with the large transformer and  
output capacitors in high quality amplifiers. These large components are  
used to keep the amplifier’s supply rails as close to DC as possible. For  
traditional supplies, bigger is better.  
But by using Pulse Width Modulation (PWM) and output voltage feedback in  
the M1 Active Mk2, we have the equivalent of near-infinite transformer and  
output capacitors, but at a fraction of the cost. PWM provides protection  
from line voltage surges that would otherwise destroy the amplifier. No  
user-replaceable fuse is required because nuisance tripping is eliminated.  
And finally, PWM practically eliminates hum because the line frequency (60  
Hz) transformer is replaced with a very high frequency (130,000 Hz)  
transformer.  
The regulated supply rails increase the amplifier dynamic range and reduce  
clipping distortion under heavy loading. The compact size of the supply does  
not significantly reduce the internal air volume of the speaker cabinet. And  
lastly, full power can be maintained even with low or “flat-topped” line  
voltages.  
Note, however, that this switching supply is NOT a universal voltage  
type that may be used with any input voltage in any country simply by  
changing the cord. If you wish to use the M1 Active Mk2s in a country  
whose line voltage is other than 120 volts AC, they must be internally  
modified or used with a step-down transformer.  
THE CABINET AND PORT DESIGN  
The M1 Active Mk2 cabinet construction employs vinyl composite material  
laminated to a .625” MDF (medium density fiberboard) core for the four sides  
and the rear. The front panel is 1” thick MDF, to withstand the greater  
demands of the drivers mounted on it. The entire cabinet is braced  
extensively in random fashion to dissipate intramodal vibration.  
M1 Active Mk2 Reference Manual  
13  
 
About the M1 Active Mk2  
WHY THE TWEETERS ARE OFFSET  
The M1 Active Mk2 speakers have been developed as a mirror-imaged pair  
with dual front mounted ports and an offset tweeter. In some applications,  
an extremely wide dispersion tweeter, such as used in the M1 Active Mk2,  
will exhibit response dips if mounted exactly on center. Wave-guide style  
tweeters, used in other products, purposely limit dispersion and thus can be  
center mounted. But as hi-end audiophile speaker companies have found, a  
high quality dome tweeter, offset in the cabinet toward the stereo “image  
center” (between the left and right speakers) will have a flatter characteristic  
frequency and power response. This (flat power response) more closely  
characterizes the way humans hear.  
On a horizontal polar response curve of the M1 Active Mk2, with the cabinet  
placed vertically, the tweeter response at one meter stays essentially  
symmetrical on either side of the cabinet’s centerline. This is because the  
angle subtended between the cabinet-centerline-to-tweeter-centerline (.5”),  
and the nominal nearfield listening distance (1 meter or 39.375”), is only 1.27  
degrees. Thus, acoustically speaking, the offset tweeter design has no  
negative effects, only the positive of smoothing the frequency response in the  
2KHz-4KHz range.  
In the tradition of the Alesis Superport design, which uses the energy from  
the back of the speaker to enhance bass performance, the M1 Active Mk2s use  
dual, front baffle mounted, long folded ports. The dual ports on the M1  
Active Mk2 are also non-symmetrical with relation to their distances from the  
woofer. In developing the M1 Active Mk2, Alesis engineers determined that  
dual ports, offset to the outside of the stereo image center gave the most  
coherent and extended low bass augmentation. The ports are flared on the  
front baffle to provide smooth and quiet exit airflow while inside they are cut  
with a 45° angle and faced toward the amplifier’s internal heat sink. This  
arrangement aids in keeping the internal amps working at a more constant  
temperature. At the same time, this 45° angle increases the port’s air entry  
efficiency.  
14  
M1 Active Reference Manual  
 
About the M1 Active Mk2  
ABOUT NEARFIELD MONITORING  
In the early days of recording, most recording studios used big monitor  
speakers almost exclusively. Unfortunately, they also required high powered  
amplifiers and expensive acoustic treatment (often poorly done) of the entire  
control room. Still, a well-constructed big monitoring system really was  
impressive to listen to, a fact not overlooked by the studio owners who  
wanted to impress the record company executives who paid for the big  
studio's time. These big systems had big level control knobs, and clients  
enjoyed "cranking-up" the volume. Fortunately, recording engineers and  
producers eventually learned that this was not the best way to accurately mix  
music because it wasn't the way most people listened to their radios, cassettes  
and CD players. Also, big monitor systems and the costs for the required  
control room acoustic treatments were going through the roof (no pun  
intended), particularly beyond the budget limits of smaller project and home  
studios which were growing in numbers. A new way of accurate monitoring  
was needed: nearfield monitoring.  
Nearfield monitors, by their definition, are intended for mounting close to the  
listener. The idea here is to improve the direct acoustic path between the  
speaker and the listener by making it shorter, thereby giving less opportunity  
for the always present indirect (reflected) sounds to get back in and muddle  
things up. With nearfield monitoring, the surrounding acoustic environment  
becomes a much less significant factor in establishing the monitor system's  
sound character.  
A good set of small monitors properly placed in a reasonably non-reverberant  
room and properly powered will yield surprisingly accurate results at budget  
prices. Carried to another studio, the same monitor should also provide  
repeatable results. In fact, some recording engineers carry their own speakers  
around because they know how they will sound in almost any room. Now,  
even the big studios use smaller speakers to augment their big monitoring  
systems, and nearfield monitors have become proven tools in the recording  
business.  
M1 Active Mk2 Reference Manual  
15  
 
About the M1 Active Mk2  
16  
M1 Active Reference Manual  
 
Speaker Installation  
CHAPTER 2  
SPEAKER INSTALLATION  
Like any speaker system, your M1 Active Mk2 speakers will work best when  
properly positioned in a suitable acoustic environment. Achieving proper  
speaker placement is usually straightforward, but even with nearfield  
monitors, speaker placement and the acoustics of the listening room itself are  
too often overlooked and can become significant contributors to an inaccurate  
and uninspiring monitoring environment.  
AVOIDING REFLECTIONS IN THE STUDIO  
While nearfield monitors are more forgiving of the surrounding room  
acoustics, it is always prudent to optimize the listening environment  
whenever possible. First, the user should be aware of the effect that the size  
of the listening room can have on low frequency response. In general, the  
smaller the room, the stronger the bottom end will be, although placement  
within a larger room can also make a difference. This has to do with the way  
low-frequency waves travel in closed spaces. If you find your monitor  
system to be either light or heavy on the bottom, try moving them around  
within your listening room.  
You should avoid locating your M1 Active Mk2s near reflective surfaces such  
as glass, tile, large open walls or table tops. Still, many rooms used for  
recording have these surfaces, so the best way to deal with them is to place  
the monitors out in the room away from reflective walls, windows and  
sizable objects. Even with these reflective surfaces separated from the  
monitoring position, typical mixing situations usually still have the top  
surface of the mixing board to deal with.  
Unfortunately, the board itself can be a major source of reflections and the  
additional acoustic conduction into the board can affect your monitor's  
amplitude and phase response. Speaker placement on the console's meter  
bridge allows two different acoustic paths between the speakers and the  
recording engineer, which results in undesirable comb filtering effects and  
poor imaging. The first path is the direct one, and the second is via a  
reflection off the mixer main control panel:  
M1 Active Mk2 Reference Manual  
17  
 
Speaker Installation  
Direct Path  
Monitors placed on the console’s meter bridge can directly radiate  
back onto the console control panel causing a strong delayed  
reflection at the listening position  
This kind of speaker placement also couples acoustic energy from the  
speaker's cabinet more readily into the console's chassis. Both conditions  
should be reduced by placing the speakers on their own stands acoustically  
detached from, and slightly behind, the console as shown below. In this  
location, the reflective path off the console's control panel is now blocked by  
the meter bridge.  
Random  
Reflections  
Moving the monitors to a position behind the meter bridge causes  
the bridge to block the offending reflective path  
18  
M1 Active Reference Manual  
 
Speaker Installation  
Careful consideration should also be given to the physical spacing between  
the speakers. Alesis recommends that the distance between the speakers for  
stereo applications equal the distance between the listener and either speaker.  
In other words, the listener and the two speakers are at the three corners of a  
triangle having equal- length sides. The illustration below shows this  
concept. Note that both speakers are turned in somewhat, so that the prime  
listening position is directly in front of each speaker. Applications that  
require monitoring by more than one engineer are accommodated by a  
smaller rotation of the cabinets. This will widen the prime listening position  
somewhat.  
Right Monitor  
Left Monitor  
The speakers and  
listener should be at  
the three corners of  
a triangle having  
equal length sides  
Prime Listening Position  
NOTE: On some mounting surfaces the vinyl finish of the M1 Active  
Mk2’s cabinet may cause it to slip too easily. Included with this  
reference manual packet are two pieces of adhesive backed non-skid  
foam. If necessary, apply the pad to either the bottom (for vertical  
placement) or cabinet side nearest the ports (for horizontal placement).  
If you plan on using the M1 Active Mk2s in both modes, simply cut the  
pad in half and apply to both the bottom and the side nearest the  
ports).  
M1 Active Mk2 Reference Manual  
19  
 
Speaker Installation  
STEREO NEARFIELD PLACEMENT OF THE  
M1 ACTIVE MK2  
NOTE: We recommend that the M1 Active Mk2 speakers be placed with the  
tweeters to the inside, not the outside, of the listening triangle.  
The “classic” studio monitor layout used to be that the tweeters be placed to  
the outside of a horizontally-oriented speaker. In the past, this configuration  
was actually beneficial in time aligning the tweeter with the woofer if the  
cabinets were not toed-in toward the listener. However, this configuration is  
highly prone to comb filtering effects if the listener’s head is moved from  
side-to-side while mixing. This “comb filtering” causes the mid-to-high  
frequency tones to get louder, then softer, then louder again as you move  
your head from side-to-side, making it very confusing when trying to mix  
with precision.  
Some people still believe that stereo separation is “improved” with tweeters  
to the outside, but this is advice left over from the early days (the sixties) of  
stereo recordings when “correct” stereo often meant a complete hard right or  
hard left placement of an instrument (or singer). As stereo mixing techniques  
changed toward placing the vocalist (for example) in the center, the old  
“tweeters-out” orientation would indeed widen the image if one’s head were  
kept in the exact center position. But this set-up proves to be very tiring, very  
quickly for the recording engineer. And, to others who are listening to the  
mix from either side of the engineer, the sound will seem to be coming  
primarily from the speaker closest to them.  
Fortunately, recording techniques have changed radically since the sixties.  
Engineers have learned to how to “place” an instrument or singer within the  
mix so that an accurate re-creation of the actual instrument and vocal  
positioning (left-to-right and front-to-back) is achieved. In the M1 Active  
Mk2, advances in crossover design technologies and improvements in the off-  
axis response of tweeter domes and woofer cone materials and profile have  
made the requirement for tweeters to be placed to the outside of the cabinet  
obsolete. In fact, using a non-toed-in, tweeters-out orientation with a  
modern, wide dispersion design like the M1 Active Mk2 will increase the  
likelihood of hearing unwanted first reflections and a variety of phase  
anomalies in your mix.  
20  
M1 Active Reference Manual  
 
Speaker Installation  
HORIZONTAL PLACEMENT RECOMMENDATION  
Traditionally, proper horizontal placement of speaker systems slightly behind  
(not on) a meter bridge accomplished two purposes: it allowed both woofer  
and tweeter to be at ear level, and many times, it permitted the recording  
engineer to see over the speakers and into the studio.  
Horizontal placement is a recommended arrangement with the M1 Active  
Mk2 because the left and right mirror-imaged pair permits a symmetrical  
alignment of drivers and ports. This will be conducive to a balanced mix. See  
Figure 2 below.  
Proper tweeter orientation is toward the stereo image center (the middle) as  
shown. Ports are always faced toward the bottom side of the cabinet. This set-  
up will promote a strongly focused center image such as for the vocalist. And  
because the (vocal) image width will be narrower than if the speakers are  
placed vertically, it will be possible to place the vocalist with great precision  
at stage center. In this orientation there will be much less chance of first  
reflections from either sidewalls or the console coloring your mix.  
M1 Active Mk2 Reference Manual  
21  
 
Speaker Installation  
VERTICAL PLACEMENT RECOMMENDATION  
Vertical placement of the M1 Active Mk2 as shown in Figure 3 is highly  
recommended. This position will simulate the soundfield that will be heard in  
most consumers’ homes and (to a great extent) their cars. For this reason,  
even if the M1 Active Mk2s are positioned horizontally for all of the mixing,  
the vertical position should always be used in the final "playback check"  
mode. (See next section)  
There are a couple of possible drawbacks to vertical placement of a nearfield  
monitor relating mostly to room interaction effects. Vertical placement allows  
the M1 Active Mk2s to portray your mix with the widest and deepest  
soundstage possible, so many people in the control room have an image of  
the “sweet spot”. However, this wide a dispersion pattern in a control room  
with walls in too-close proximity to the speakers can add strong reflections to  
the sound you hear, muddying your mix. Page 29 shows the control room  
placement/ distance recommendations, which should help you determine if  
your available recording space would work well with the M1 Active Mk2s set  
up vertically.  
22  
M1 Active Reference Manual  
 
Speaker Installation  
PLAYBACK CHECK MODE (VERTICAL MID-FIELD)  
After you’ve got your mix just right it’s always good practice to perform a  
“playback check” by standing the M1 Active Mk2s vertically and making the  
listening triangle larger. The purpose of the playback check is to simulate  
what your masterpiece will sound like in a “typical” home listening  
environment. It is in this configuration that the imaging specificity of your  
mix can best be evaluated. Generally, in the playback check mode you want  
to arrange the speakers in the same equilateral listening triangle that you do  
in a nearfield setup, but instead of each side of the triangle being about 3 feet  
long, the distances between stereo speakers and to your listening position  
should be between 7 and 12 feet.  
When setting the left and right speakers vertically, place the tweeters toward  
the center with the ports toward the outside. In this vertical position, the M1  
Active Mk2 becomes a “line source” speaker which is the most common  
home set up. (A 12” three-way with woofer on bottom, midrange in the  
center and tweeter at the top is a line source, as are most forms of tower  
speakers.) When the M1 Active Mk2 is set vertically in its “column”  
configuration, the horizontal dispersion (left and right) of the speaker is  
widest, and the vertical dispersion (up and down) is narrowest.  
Unfortunately a vertical setup will also increase room effects, so there are  
minimum recommended setup distances from side and back walls: the  
speakers should be a minimum of 2.5 feet from the side walls and 3 feet from  
the rear walls. See the illustration on page 26.  
After you’ve got the requisite distances from the side and back walls, it’s  
often helpful to adjust the 7 to 12 foot equilateral listening triangle distances.  
What you want to find is the maximum distance that you can separate the  
two speakers while still holding a solid center image. If you get this  
placement correct and you’ve done a good job in the mix, you should be  
rewarded with a soundstage that accurately places the musicians in the width  
and depth perspective in which they were recorded. The sound should be  
very similar to what you heard at your mixing board, with possibly a little  
more ambience contributed by the listening room.  
The “other” playback check mode, sometimes considered of greater  
importance than the home environment, is to listen to your mix over a car  
audio system. Bear in mind that an expertly designed car audio system can  
approach the imaging and soundstaging capabilities of an optimally setup  
studio or living room, but most times this is NOT the case. The inherent  
limitations of an always-off-axis listening position and the variables of  
speaker placement, bass coupling (boost) in the small interior and numerous  
other factors make the car environment highly suspect. So, understand the  
sonic capabilities (and deficiencies) of your (or other) car audio systems, and  
evaluate your mix accordingly.  
M1 Active Mk2 Reference Manual  
23  
 
Speaker Installation  
PLUGGING THE PORTS TO ADJUST FOR ROOM ACOUSTICS  
The low frequency response of the M1 Active Mk2s can be custom tailored by  
plugging the ports. If the speakers must be placed less than one foot from a  
front wall, or if they are too close to a corner, then the bass may become  
exaggerated and inaccurate.  
follows:  
The rules of thumb for these situations are as  
a) less than 1 foot from a front wall but away from any corner:  
plug one port  
b) less than 1 foot from a front wall and a corner:  
plug both ports  
The “plug” can be wad of cloth to completely block the port(s) or a more  
porous material like fiberfill which will give less bass attenuation. The bass  
output of the M1 Active Mk2 is thus easily variable depending on in-room  
positioning and/or personal preference.  
If the M1 Active Mk2s are to be used in a system with a subwoofer, the  
proper blend of the two systems is critical if low-bass accuracy is to be  
maintained. Here again, your ear is your most important piece of test  
equipment. If the subwoofer (such as the Alesis Point One) or preamplifier  
has 80Hz high-pass filters built-in for connection to the other amplifiers, then  
no port plugging is necessary. The proper match will have already been  
taken care of electronically. In the absence of an 80Hz high-pass filter feeding  
the M1 Active Mk2s, you’ll need to experiment with various degrees of port  
plugging to minimize the cancellations and nodes that can occur from bass  
sources placed several feet apart in a room. In practice we’ve found that a  
single port plugged with cloth is usually the best compromise. See Figure 5  
below. It shows the approximate bass attenuation that can be expected with  
one port plugged.  
24  
M1 Active Reference Manual  
 
Speaker Installation  
M1 Active Mk2 Reference Manual  
25  
 
Speaker Installation  
CONNECTIONS  
The M1 Active Mk2 has been designed to be as simple as possible to set up  
and use. However, please follow the instructions to ensure that you get the  
best possible performance from your monitors.  
Before connecting the speakers, make sure the power switches of the  
M1 Active Mk2s and any equipment they will be connected to are  
turned OFF.  
AC POWER CABLE  
READ ALL SAFETY WARNINGS IN THE PREVIOUS SECTION OF THIS  
MANUAL TO ENSURE SAFE OPERATION OF THESE UNITS. Connect the  
M1 Active Mk2s to the specified power using the AC cables supplied. The  
AC cables are removable. If the distance to your AC outlet is longer or  
shorter than the supplied cable, you may substitute an approved standard  
NEMA-to-CEE power cable of the correct length, available from most  
electronics stores.  
GROUNDING  
CONNECT THE M1 ACTIVES TO A PROPERLY GROUNDED OUTLET ONLY.  
DO NOT USE ADAPTERS WHICH REMOVE THE SAFETY GROUND  
PROTECTION OR CUT OFF THE GROUNDING PRONG ON THE POWER  
CORD. Proper grounding is essential for user safety and low noise. If  
you experience 60-cycle hum in your sound system as a result of  
different ground potentials between different units in your system,  
plug all units into the same AC circuit (if the total power load allows)  
and make sure other devices in the system are properly grounded  
themselves. The M1 Active features balanced inputs, so if it is properly  
connected to other balanced units, AC ground potentials will not affect  
the audio. If you cannot get rid of ground loops, consult a professional  
electrician familiar with sound system power designs.  
USE CLEAN POWER  
The M1 Active Mk2's internal power supply is designed to filter out most AC  
line noise. However, it is still good practice to plug your sound equipment  
into an AC circuit that is not shared with lighting dimmers, refrigerators, air  
conditioning units, or other appliances that may induce noise into the power  
system.  
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M1 Active Reference Manual  
 
Speaker Installation  
POWER SWITCH  
The POWER switch is located on the back panel. A blue power indicator  
lamp is on the front panel.  
INPUT CONNECTIONS  
Almost any conventional line-level source may be plugged into the M1 Active  
Mk2’s LINE INPUT jack. The Line Input jack accepts both XLR and 1/4”  
input plugs wired either balanced or single-ended (unbalanced). The best  
connection is to use a high-quality XLR-to-XLR “mic cable” between the  
output of the source (usually, the CONTROL ROOM OUTPUT of the console)  
and the speakers. A conventional 1/4” “patch cord" mono TS-type plug will  
also work for unbalanced sources which automatically ground the minus  
input.  
Polarity: Input connector wiring is printed to the left of the connector on the  
back panel and is as follows:  
+ Pin 2: tip (“hot”)  
- Pin 3: ring (“cold”)  
Shield Pin 1: sleeve (ground)  
A positive voltage on the “hot” connector will cause the drivers to move  
outwards.  
Unbalanced Line Input  
Balanced Line Input  
Signal  
Tip  
Hot  
Tip  
Cold  
Ring  
Sleeve  
Ground  
Tip  
Sleeve  
Ground  
Tip  
Sleeve  
Sleeve  
Ring  
Direct connection of unbalanced -10 dBV line level sources: Most  
synthesizers, drum machines, effect devices, cassette decks and CD players  
operate at this level. Their average signal level is about 1/3 of a volt. They  
have a 2-conductor output jack that is either a 1/4" phone or "RCA phono"  
type. These may be plugged directly into the M1 Active Mk2’s LINE IN jacks.  
M1 Active Mk2 Reference Manual  
27  
 
Speaker Installation  
But do NOT plug the speaker output of an amplifier, receiver, or similar  
device into the LINE INPUT jack. Use only line-level sources. Plugging  
too loud of a signal into the LINE INPUT jack may damage the  
electronics.  
Balanced +4 dBu line level sources: Professional recording and processing  
equipment typically provides a balanced, 3-conductor signal output that is a  
higher voltage (1.24 volts nominal level) than most synthesizers and stereo  
equipment. The LINE INPUT jacks are designed to handle these balanced  
inputs.  
Balanced sources often feature XLR outputs. Connect them with an XLR-to-  
XLR cable. Many consoles (such as the Alesis Studio series) feature balanced  
outputs on 1/4” jacks; you may use a TRS-to-TRS balanced phone cable, or an  
XLR-to-1/4 inch phone TRS (tip-ring-sleeve) cable, as shown below. The  
advantage of using an XLR on the speaker side is that it is a locking connector  
and cannot be accidentally disconnected.  
NOTE: Use high quality input connectors which conform to industry  
standard sleeve dimensions. Some off-brand connectors, particularly cheap  
1/4” TRS plugs, do not provide reliable connections because of slight  
dimensional differences.  
SETTING THE INPUT LEVEL CONTROL  
In most cases, the INPUT LEVEL control should NOT be set at full  
rotation. For best system dynamic range, follow the instructions  
below.  
The goal is to set the input level of the M1 Active Mk2s for the desired  
listening level, when all the rest of the system is at its nominal operating level.  
“Nominal” means its normal average level, expecting peaks from 8 to 15 dB  
above that on occasion. For the best signal-to-noise ratio, everything before  
the M1 Active Mk2 should be as loud as possible. The M1 Active Mk2s’  
INPUT LEVEL control, being last in the signal chain, is the worst place to  
make up gain lost earlier in the system.  
28  
M1 Active Reference Manual  
 
Speaker Installation  
TO SET THE LEVEL WITH A MIXER:  
1. Turn on all system components (the M1 Active Mk2s last) and turn the M1  
Active Mk2’s INPUT LEVEL control all the way down.  
2. Play program through the mixer and raise the mixer’s fader levels until its  
meter averages around “0 VU”.  
3. Raise the Control Room Output to its nominal position (usually “2  
o’clock” or 3/4 of the way up).  
4. On one speaker, raise its INPUT LEVEL CONTROL for a comfortable  
level in the engineer’s seat (if you have a sound pressure meter, 85 dB SPL  
is a common standard for listening).  
5. Match the level for the other speaker. Note that the numbers on the back  
panel are only a rough guide; for precise left/right imaging, use pink  
noise or test tones and a sound pressure meter.  
The Input Level control has a 28 dB range with a center detent. The detent has  
no particular meaning, but helps in adding a mental “reference position”  
when attempting to set levels from in front of the speaker. With the control at  
a maximum clockwise rotation, 2.0 volt input will produce full amplifier  
output (102 dB SPL “A” weighted from two speakers at 1 meter).  
For the technically-minded, here is an approximate chart of SPL levels for  
various settings of the INPUT LEVEL control, measured at 1 meter from two  
speakers simultaneously (all settings, especially near the extremes of the  
range, are subject to a plus or minus 2 dB error):  
Mark  
-10 dBV  
nominal  
-- dB SPL  
--  
+4 dBu  
nominal  
-- dB SPL  
--  
0 (MIN)  
1
2
3
57.0  
63.5  
69.0  
75.5  
4
5
68.2  
71.0  
80.2  
83.0  
6
7
73.0  
78.0  
85.0*  
90.0  
8
9
83.5  
85.5*  
86.5  
95.5  
97.5  
98.5  
10 (MAX)  
* denotes recommended setting for control room use  
M1 Active Mk2 Reference Manual  
29  
 
Speaker Installation  
AVOIDING DAMAGE  
The best protection against speaker failure is to mix at a reasonable listening  
level. With a +4 dBu input and the input level control set to “6”, the M1  
Active Mk2 speakers produce a sound pressure level (SPL) of 85 decibels at 1  
meter, which is a good working level for mixing. At maximum output before  
clipping, they can generate peak levels 118 dB SPL at one meter – a level  
which may cause hearing loss after prolonged exposure. While the  
biamplified design of the M1 Active Mk2 avoids the common “blown  
tweeter” problem of conventional designs (when a broadband amplifier clips  
on a bass note, it sends unusually high energy to the tweeter, which tries to  
reproduce the square wave), it is not invulnerable. If you need higher power  
levels, you are not using the speaker in a near-field application. For  
extremely loud mid-field and far-field monitoring, we recommend the Alesis  
Monitor Two speaker with a 300-watt per channel amplifier. Many studios  
will check recordings on both systems, alternating to avoid ear fatigue and to  
gain perspective on the mix.  
30  
M1 Active Reference Manual  
 
Surround Sound  
CHAPTER 3  
SURROUND SOUND  
ABOUT SURROUND SOUND  
Surround sound is the term used for several different systems which use  
multiple channels of playback in the listening room to recreate a truly three-  
dimensional sound experience. The practice of recording music-only in  
surround sound is a fairly recent innovation. Surround sound for video,  
however, has been around for over ten years. With modern encoding  
methods, multichannel audio may be delivered to consumers on standard  
video tape, video discs, and even through broadcast, with the proper encoders  
(devices which take multiple channels of audio and combine them into two  
channels) and decoders (used at the receiving end to split the signal back into  
multiple channels).  
Systems are in use which use three (left, right, and surround), five (left,  
center, right, left surround, right surround, often supplemented by a sixth  
subwoofer channel), and more speakers. The original Dolby Surroundof  
the mid-eighties was a matrixed three-channel-only system. It had left, right  
and a mono surround (rear) track, which was usually played through two  
surround speakers. In 1987, Dolby Pro Logic, a four-channel matrix system,  
was introduced. Pro Logic added a dedicated center channel to which most  
dialog was assigned. The rear surround channel was still in mono. In 1996,  
Dolby Digital(AC-3) and DTS, fully discrete six-channel audio delivery  
platforms with separate left-rear and right-rear channels first became  
available to consumers on laserdisc and, more recently, on DVD (Digital  
Versatile Disc).  
With so many listeners hearing music through their multimedia systems, it is  
important for engineers to produce music on surround systems, even if  
they’re not working for film or video applications. Powered monitors like the  
Alesis M1 Active Mk2 Biamplified Reference Monitor have proven to be a  
simple, cost-effective way to add five-channel surround to control rooms.  
M1 Active Mk2 Reference Manual  
31  
 
Surround Sound  
CENTER SPEAKERS IN MUSIC MIXES  
In video applications, with left, center and right channels all set to deliver  
equal output, the ear tends to hear dialog as coming only from the center  
channel. (It’s a psychoacoustic effect because all right and all left channel  
signals are fed to the center.)  
In Dolby Pro Logic, the center channel information is derived from sum and  
difference information encoded in the left and right channels. The very  
attributes that make this matrix-type system viable for video application  
make it less desirable for music-only reproduction. In practice, there is a hard  
center dialog channel but there is also a sort of phantom mono channel  
developed between the left and center channel and the right and center  
channel. This between-channel phantom mono image exists because so much  
of the information contained in each channel (left and center or right and  
center) is identical. Hence, mono. In the few music-only recordings encoded  
in Dolby Pro Logic, the derived center channel could lead to some drastic  
changes in spatial perception.  
In developing the M1 Active Mk2s for use as left, center and right front  
channel sources, we wanted them to be useable in both audio/video and  
audio-only “matrix” type applications. We discovered two, already available  
solutions to the large “wall-of-mono” effect produced by Dolby Pro Logic  
when playing audio-only material. The first is easy. Most home audio Dolby  
Pro Logic receivers will let you take the center channel out completely by  
putting the receiver in the “phantom” (no center channel) mode. It preserves  
the classic stereo effect of the front channels while adding rear surround.  
This method works well with most stereo-only recordings which have no  
surround encoding. But it’s much better if the rear channels have true matrix  
(mono) surround (like applause) encoded in the mix.  
The second method of using Dolby Pro Logic gets the center channel back  
into the mix. Most of these same home audio receivers have an audio-only  
surround mode which significantly attenuates the output of the center  
channel in relation to the left and right. The audible benefit here is that the  
mix sounds like a stereo only recording but the center image (like a vocalist)  
becomes a hard center. There is no image wander, as the frequencies change,  
for instance. And the classic listening “sweet spot” expands dramatically,  
allowing for accurate soundstage and instrument placement when listening  
far off-axis. (This attenuating of the center channel for audio only is also  
employed by advanced professional matrixed decoders such as the Circle  
Surround, Miles Technology and Lexicon units.)  
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M1 Active Reference Manual  
 
Surround Sound  
PLACEMENT OF THE CENTER M1 ACTIVE MK2 SPEAKER  
IN THE STUDIO  
The left, center and right speakers should all be placed in an arc so that the  
distance of all drivers to the listener is identical (see page 29). The equilateral  
listening triangle as described earlier for stereo (two-channel) playback  
should be retained, with the center speaker placed vertically in the center,  
exactly between the left and right (vertical) M1 Active Mk2s.  
It does not matter what type of M1 Active Mk2 is used for the center speaker (tweeter  
in or tweeter out). Since M1 Active Mk2s are sold as pairs, a 5-channel system  
requires the purchase of a single speaker, breaking up a pair. Some dealers may  
request that you purchase in pairs only; others may be able to arrange purchase of a  
single unit. For the rear channels, we recommend a mirror-image pair, although this  
is less critical than in the front.  
As discussed above, for music-only recording the signal level to the center  
channel will be attenuated over the levels of the left and right speakers. As a  
starting point we would recommend that you set the center channel level  
–6dB below the left and right channels. To get these levels fairly accurate a  
white or pink noise source (such as from a test CD) is very helpful along with  
an inexpensive sound level meter (such as the Radio Shack cat. no. 33-2050).  
If you are recording audio-for-video, the center channel signal level should be  
the same as left and right channels. The left, center, right speaker layout  
configuration can remain the same as for an audio-only mix. With all front  
speakers operating at equal levels, the “sweet spot” listening area will  
become very large but the “wall-of-mono” effect mentioned above (in regards  
to music) will be of little consequence since most of the dialogue will be  
mixed specifically into the center channel.  
M1 Active Mk2 Reference Manual  
33  
 
Surround Sound  
PLACEMENT OF REAR SURROUNDS  
The following suggestions for optimal M1 Active Mk2 placement are derived  
from several sources: 1) Standard industry practice for home installations as  
recommended by the manufacturers of surround encoder/decoder units; 2)  
recommendations developed by Tom Holman for setting up THX surround  
theater sound systems, and 3) Alesis engineers’ experience fine-tuning the  
performance of the SMS Monitoring System in order to find the mounting  
configuration which results in the most natural and accurate surround  
placement. With the many different playback systems in use, there is room  
for interpretation of what the best placement is in a control room, but the  
following represents a good starting point which you are free to change to  
your taste.  
Vertically, the M1 Active Mk2s should be placed on the side wall of the  
control room, above your head, with the woofers on top, tweeters on the  
bottom. The ideal location is to have the center of the speaker (between the  
woofer and tweeter) at 80% of the floor-to-ceiling height. (For a standard 8  
foot ceiling height the center line would be at 96” x 80% = 76.8” from the  
floor.)  
Recommended positioning of surround speakers  
C
20%  
3min  
80%  
Horizontally, place the M1 Active Mk2s slightly behind the 90° position, at  
110° on each side. Make sure that at the position used, there is still at least 3  
feet to the back wall of your studio. If you do not have at least 3 feet to the  
back of your studio, then the speakers will work better if placed diagonally in  
the rear corner as shown on the next page.  
34  
M1 Active Reference Manual  
 
Surround Sound  
M1 Active Mk2 Reference Manual  
35  
 
Surround Sound  
WALL MOUNTING  
Once your have located the general area for the horizontal and vertical  
position, you need to find a wall stud. Attach shelving brackets or other  
commercial speaker-mounting device into the wall stud, then attach the M1  
Active Mk2s to the mount, allowing room for the rear-panel input and AC  
connections.  
The M1 Active Mk2s weigh 19.5 lbs., so it is vitally important that any  
stand they’re resting on be securely mounted through the wall material  
(usually 3/4” sheetrock, which by itself does not have the strength to  
support the speakers) and into a wooden stud using hardened screws  
or other fastener rated to hold at least two times that weight.  
36  
M1 Active Reference Manual  
 
Surround Sound  
MIXING FOR DISCRETE SIX CHANNEL REPRODUCTION:  
MATCHED VS. SPECIALIZED SPEAKERS  
While most speaker systems for monitoring music in surround use the same  
speaker cabinet in all positions, both front and rear, keep in mind that most  
consumer video surround installations use a different speaker in the rear  
channels. These rear speakers typically do not have the same directionality or  
wide frequency response of the M1 Active Mk2s. When mixing for film,  
speakers with a broad ambient, non-directional response are used to mimic  
the multi-speaker situation in most movie theatres. Keep this in mind when  
making music mixes with full-range high-power speakers like the M1 Active  
Mk2s as the surround speakers.  
The difference between music surround and video surround playback has a  
long history:  
Dolby Pro Logic, which works best with dipole (i.e., speakers splayed in  
different directions out of phase) surround speakers, has been the  
standard for surround sound in the home for 10 years.  
The most accepted home playback medium, VHS videotape, can only play  
back (mono) surround in Dolby Pro Logic. VHS will not support Dolby  
Digital or DTS.  
There are only two playback mediums, laser disc and DVD, that support  
Dolby Digital (discrete) and DTS (discrete). After 20 years in existence,  
laser disc has only a 2% market share. Some digital satellite broadcasters  
have started broadcasting in Dolby Digital, but these discrete broadcasts  
will be reserved for blockbuster movies initially.  
Discrete Dolby Digital, DTS and Sonys SDDS are most commonly mixed  
for theatrical release using surround, not monopolar (direct) monitors.  
Among the recording engineers who have recorded audio-only, the  
consensus seems to be that the role of the surround speaker is to give the  
listener a sense of immersion in the musical event. This is done by reserving  
the rear channels for audience sounds, in the case of a live recording, or  
perhaps by reproducing the reverberant acoustics of the recording  
environment itself. Other engineer/producers prefer using five identical  
full-range speakers and mixing primary instruments and vocals into the  
surround channels.  
So, our basic recommendation for mixing an audio-only six channel recording  
is to intentionally limit the frequency response of the rear speakers using a  
graphic equalizer or high-pass (100 Hz rolloff)/low pass (12 kHz rolloff) filter  
on your mixer. This will help you get a rough idea of what a home system  
playback will sound like.  
This arrangement will also allow your mix to sound best over a well set up  
car audio system. This is because professional installers have learned that a  
mobile system performs best when they concentrate on producing a  
soundstage across the front of the vehicle. They do this by placing high  
quality drivers in the front of the vehicle which produce frequencies from the  
M1 Active Mk2 Reference Manual  
37  
 
Surround Sound  
mid bass (about 80Hz) on up. In the rear go the subwoofers and sometimes,  
small full range drivers which provide fill. So, in essence, todays best car  
audio systems are designed to produce an enveloping environment very  
similar to that of a home theater.  
The use of M1 Active Mk2s (or any monopolar speaker) as full-range  
surrounds would be useful in the following cases:  
If the surround speakers are just as important as the fronts in achieving a  
specialized effect, such as completely mixing the sax in the left rear only  
and a flute in the right rear.  
If you know that your mix will always be played back on a monopolar  
surround system.  
If the control room is completely damped with sound absorption on all  
surfaces. (This renders the reverberant-field generating properties of a  
bipole/dipole speaker ineffective.)  
* Dolby Surround, Dolby Pro Logic, and Dolby Digital are trademarks of Dolby Laboratories, Inc.  
38  
M1 Active Reference Manual  
 
Troubleshooting  
CHAPTER 4  
TROUBLESHOOTING  
TROUBLESHOOTING INDEX  
If you experience problems while using the M1 Active/Surround systems,  
please use the following table to locate possible causes and solutions before  
contacting Alesis Technical Support for assistance.  
Symptom  
Hum or buzz  
Cause  
Solution  
Ground loop  
Use balanced cables.  
between source and Put M1 Actives on the  
speaker  
same AC power circuit  
as the mixer.  
No sound  
Speaker  
disconnected  
Check input cable  
connections  
INPUT LEVEL down Turn up input control  
on back panel  
AC power not on  
Blue LED on front  
should be on. Check  
switch and power  
input cable.  
Unfocused sound,  
bass frequencies  
muddy or missing  
Inputs out of phase  
Check + and -  
connections from mixer  
to input. Verify pin 2  
is hot.  
Subwoofer being  
used improperly  
Install port plugs when  
using a subwoofer  
Poor mix  
Compare to  
commercial CD of  
similar style: time to  
remix your track....  
Distorted output  
Power amp  
overloading  
speakers  
Turn down level  
Damaged speaker  
components  
Swap channel s to see if  
the problem follows the  
speaker; if so contact  
Technical Support  
M1 Active Mk2 Reference Manual  
39  
 
Troubleshooting  
MAINTENANCE  
CLEANING  
The cabinet surfaces of the M1 Active Mk2 are covered with a vinyl laminate.  
Clean these surfaces when necessary with a lint-free cloth dampened in warm  
soapy water. USE ONLY A DRY CLOTH ON THE BACK PANEL OF THE  
POWER AMPLIFIER. Do not attempt to clean the cabinet with a brush (which  
may damage the surface) or a sponge (which may leave small crumbs in the  
texture).  
Do not attempt to clean either of the drivers.  
The M1 Active Mk2/Surround speakers require no periodic maintenance.  
REFER ALL SERVICING TO ALESIS  
We believe that the M1 Active Mk2 is one of the most reliable powered  
monitors that can be made using current technology, and should provide  
years of trouble-free use. However, should problems occur, DO NOT attempt  
to service the unit yourself. Service on this product should be performed only  
by qualified technicians. THERE ARE NO USER-SERVICEABLE PARTS  
INSIDE.  
SERVICE  
Before sending the M1 Active Mk2s in for repair, make sure they are faulty  
and that the problem isn't being caused by something else in the system.  
Distortion or noise may be caused by a defective preamp, cable, equalizer etc.,  
or a loose connection in the system. Connect the speakers to a system that is  
known to be working properly to check whether the monitors have  
malfunctioned.  
OBTAINING REPAIR SERVICE  
Before contacting Alesis, check all your connections, and make sure youve  
read the manual.  
Customers in the USA and Canada: If the problem persists, call Alesis USA  
at 1-800-5-ALESIS and request the Technical Support department. Talk the  
problem over with one of our technicians; if necessary, you will be given a  
return order (RO) number and instructions on how to return the unit. All  
units must be shipped prepaid and COD shipments will not be accepted.  
For prompt service, indicate the RO number on the shipping label. Units  
without an RO will not be accepted. If you do not have the original packing,  
ship the M1 Active Mk2 in a sturdy carton, with shock-absorbing materials  
such as styrofoam blocks or bubble-packsurrounding the unit. Make sure  
40  
M1 Active Reference Manual  
 
Troubleshooting  
the drivers will not be pressed on by the packing in shipment. Shipping  
damage caused by inadequate packing is not covered by the Alesis warranty.  
Tape a note to the top of the unit describing the problem, include your name  
and a phone number where Alesis can contact you if necessary, as well as  
instructions on where you want the product returned. Alesis will pay for  
standard one-way shipping back to you on any repair covered under the  
terms of this warranty. Next day service is available for a surcharge.  
Field repairs are not normally authorized during the warranty period, and  
repair attempts by unqualified personnel may invalidate the warranty.  
Correspondence address for customers in the USA:  
Alesis Product Support  
1633 26th Street  
Santa Monica, CA 90404  
THIS IS NOT A SERVICE LOCATION. DO NOT SHIP UNITS TO THIS  
ADDRESS.  
Customers outside the USA and Canada:  
Contact your local Alesis distributor for any warranty assistance. The Alesis  
Limited Warranty applies only to products sold to users in the USA and  
Canada. Customers outside of the USA and Canada are not covered by this  
Limited Warranty and may or may not be covered by an independent  
distributor warranty in the country of sale. Do not return products to the  
factory unless you have been given specific instructions to do so.  
M1 Active Mk2 Reference Manual  
41  
 
Specifications  
SPECIFICATIONS  
ENCLOSURE  
MATERIALS AND CONSTRUCTION  
Front baffle painted in metallic charcoal-gray, one inch (1) thick MDF with  
radiused edges to minimize diffraction. Sides and rear baffle covered in  
metallic charcoal-gray vinyl laminate, over five-eighths inch (0.625) thick  
MDF.  
Dual ports with 45° inlet and flared front baffle outlet allow precise, phase  
accurate woofer-to-port frequency transition. Ports also aid in cooling  
internally mounted primary amplifier heat sink.  
Flush mount, rubber woofer trim ring allows consistent power response  
characteristic at wide off-axis angles. Flush-mount tweeter plate assures  
smooth off-axis response.  
UL-approved fiberglass acoustical damping material damps internal mid-  
frequency reflections from rear of woofer cone before entering port, lessening  
IM distortion.  
TRANSDUCERS  
LOW FREQUENCY DRIVER:  
6.5(165mm) diameter dynamic driver with proprietary non-woven carbon  
fiber (NWCF) cone and 1.5diameter, long-wind voice coil.  
Dampened linear rubber surround with moderate internal damping and  
constant linear displacement Nomex spider. 5 mm X-max excursion  
capability.  
Dual magnet structure uses top magnet in opposed (bucking) configuration  
for magnetic shielding.  
HIGH FREQUENCY DRIVER:  
1silk soft-dome tweeter with special wave guide baffle.  
Low-viscosity ferrofluid cooling extends power handling while retaining  
impulse response capability.  
Dual magnet structure uses top magnet in opposed (bucking) configuration  
for magnetic shielding.  
42  
M1 Active Reference Manual  
 
Specifications  
CROSSOVER SECTION  
Crossover type:  
4th-order, 24dB/octave Linkwitz-Riley @ 2000Hz  
20kbalanced 10kunbalanced  
4th order optimal Q high pass filter at 48Hz with +3 dB  
equalization  
Input Impedance:  
Low Frequency Filter:  
AMPLIFIER SECTION  
LOW FREQUENCY AMPLIFIER  
Rated power output:  
Distortion:  
Slew rate:  
75 watts, 6load  
<0.02% THD @ 30 watts/820Hz-20kHz  
19V/µsec  
Signal-to-Noise ratio:  
>110dB referenced to 60 watts @ 8, Aweighted,  
1kHz  
HIGH FREQUENCY AMPLIFIER  
Rated Power Output:  
Distortion:  
25 watts, 4load  
0.025% THD @ rated power  
9V/µsec  
Slew rate:  
Signal-to-Noise ratio:  
>112dB @ rated output  
ACOUSTIC SECTION  
Free-Field Frequency Response:  
Lower Cutoff Frequency:  
Upper Cutoff Frequency:  
2dB, 50Hz to 20KHz  
40Hz -10dB  
23.5KHz 10dB  
Maximum Peak SPL per pair: 118dB SPL @ 1m  
Maximum short term SPL:  
80Hz to 3.0KHz 105dB SPL @ 1m  
GENERAL  
Power Consumption:  
120 watts with musical program, loud mix  
12 watts quiescent (idle)  
AC Dropout Voltage:  
120V AC version: 80V AC  
240V AC versions: 160V AC  
Weight:  
Dimensions (H x W x D):  
19.5 lbs. (8.9 kg) each  
15(38.1 cm) x 8.5(21.6 cm) x 10(25.3 cm)  
M1 Active Mk2 Reference Manual  
43  
 
INDEX  
1/4input plugs, 27  
AC cables, 26  
AC power, 13, 26, 43  
amplifiers, 10, 12, 43  
balanced, 27  
placement, 17  
horizontal, 21  
surround, 34  
vertical, 22  
Playback check mode, 23  
Polarity, 27  
biamplified, 10  
center channel, 32  
crossover, 11, 43  
frequency response, 43  
with ports plugged, 24  
front baffle, 42  
fuse, 13  
ports, 14  
plugging, 24  
power supply, 13  
reflections, 17, 20, 21  
Safety, 3  
service, 4, 40  
spacing, 19  
SPL, 29  
subwoofer, 24  
Surround sound, 31  
time alignment circuit, 12  
tweeter, 11, 42  
mirror to inside, 20  
offset, 14  
Ground loop, 39  
grounding, 26  
INPUT LEVEL, 28  
detent, 29  
interference, 7  
LINE IN, 27  
Magnetic shielding, 11, 42  
mounting, 19  
nearfield, 15  
warranty, 9, 45  
woofer, 11, 42  
XLR, 28  
noise, 26  
phase, 39  
44  
M1 Active Reference Manual  
 
ALESIS LIMITED WARRANTY  
ALESIS CORPORATION ("ALESIS") warrants this product to be free of defects in material and  
workmanship for a period of one (1) year for parts and for a period of one (1) year for labor from the date of  
original retail purchase. This warranty is enforceable only by the original retail purchaser and cannot be  
transferred or assigned.  
The purchaser should complete and return the enclosed warranty card within 14 days of purchase.  
During the warranty period ALESIS shall, at its sole and absolute option, either repair or replace free of  
charge any product that proves to be defective on inspection by ALESIS or its authorized service  
representative. In all cases disputes concerning this warranty shall be resolved as prescribed by law.  
To obtain warranty service, the purchaser must first call or write ALESIS at the address and telephone  
number printed below to obtain a Return Authorization Number and instructions concerning where to return  
the unit for service. All inquiries must be accompanied by a description of the problem. All authorized  
returns must be sent to ALESIS or an authorized ALESIS repair facility postage prepaid, insured and properly  
packaged. Proof of purchase must be presented in the form of a bill of sale, canceled check or some other  
positive proof that the product is within the warranty period. ALESIS reserves the right to update any unit  
returned for repair. ALESIS reserves the right to change or improve design of the product at any time without  
prior notice.  
This warranty does not cover claims for damage due to abuse, neglect, alteration or attempted repair by  
unauthorized personnel, and is limited to failures arising during normal use that are due to defects in material  
or workmanship in the product.  
THE ABOVE WARRANTIES ARE IN LIEU OF ANY OTHER WARRANTIES OR REPRESENTATIONS  
WHETHER EXPRESS OR IMPLIED OR OTHERWISE, WITH RESPECT TO THE PRODUCT, AND  
SPECIFICALLY EXCLUDE ANY IMPLIED WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR  
MERCHANTABILITY OR OTHER IMPLIED WARRANTIES. Some states do not allow limitations on how  
long an implied warranty lasts, so the above limitation may not apply to you.  
IN NO EVENT WILL ALESIS BE LIABLE FOR INCIDENTAL, CONSEQUENTIAL, INDIRECT OR OTHER  
DAMAGES RESULTING FROM THE BREACH OF ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING,  
AMONG OTHER THINGS, DAMAGE TO PROPERTY, DAMAGE BASED ON INCONVENIENCE OR ON  
LOSS OF USE OF THE PRODUCT, AND, TO THE EXTENT PERMITTED BY LAW, DAMAGES FOR  
PERSONAL INJURY. Some states do not allow the exclusion or limitation of incidental or consequential  
damages, so the above limitation or exclusion may not apply to you.  
THIS CONTRACT SHALL BE GOVERNED BY THE INTERNAL LAWS OF THE STATE OF CALIFORNIA  
WITHOUT REFERENCE TO CONFLICTS OF LAWS. This warranty gives you specific legal rights, and you  
may also have other rights required by law which vary from state to state.  
This warranty only applies to products sold to purchasers in the United States of America or Canada. The  
terms of this warranty and any obligations of Alesis under this warranty shall apply only within the country  
of sale. Without limiting the foregoing, repairs under this warranty shall be made only by a duly authorized  
Alesis service representative in the country of sale. For warranty information in all other countries please refer  
to your local distributor.  
ALESIS  
1633 26th Street  
Santa Monica, California 90404  
1-(800)-5-ALESIS  
PLEASE SEND IN YOUR WARRANTY CARD  
for more effective service and product update notices  
Alesis Corporation 1633 26th Street, Santa Monica, CA 90404  
© 2001 Alesis Corporation Specifications Subject To Change Without Notice 7-51-0092 2/01  
M1 Active Mk2 Reference Manual  
45  
 
46  
M1 Active Reference Manual  
 

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