Alesis 7-51-0092-D User Manual

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REFERENCE MANUAL

©2001-2005A LESISCORPORATION

Alesis M1 Active Mk2 Reference Manual

© Copyright-200,15AlesisStudio Electronics, Inc. All rights reserved. Reproduction in whole or in part is prohibited. “M1 Active Mk2” and “Superport” are trademarks of Alesis Studio Electronics, Inc.

ALESIS CONTACT INFORMATION

Alesis Studio Electronics, Inc.

www.alesis.com

Do not use this address for repair service.

E-Mail:info@alesis.com

Website: http://www.alesis.com

Contents/Safety Warnings

CONTENTS

Introduction

2

ABOUT THE M1 ACTIVE MK2 ...............................................................

9

Unpacking and Inspection

9

Inside your new speakers

10

About Nearfield monitoring

15

SPEAKER INSTALLATION....................................................................

17

Avoiding reflections in the studio

17

Stereo nearfield placement of the M1 Active Mk2

20

Connections

26

Setting the Input Level control

28

SURROUND SOUND ............................................................................

31

About surround sound

31

Center speakers in music mixes

32

Placement of the center M1 Active Mk2 speaker in the studio

33

Placement of rear surrounds

34

Mixing for discrete six channel reproduction: matched vs. specialized speakers

 

37

TROUBLESHOOTING ...........................................................................

39

Troubleshooting Index

39

Maintenance

40

SPECIFICATIONS ................................................................................

42

Enclosure

42

Transducers

42

Crossover section

43

Amplifier Section

43

Acoustic Section

43

General

43

INDEX..............................................................................................

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M1 Active Mk2 Reference Manual

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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-freeuse, 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 otherline-levelsource 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.

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M1 Active Reference Manual

About the M1 Active Mk2

CHAPTER1

ABOUT THEM1 ACTIVEMK2

UNPACKING ANDINSPECTION

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

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-imagedpairs. If you have received a pair where the tweeters are both on the same side, contact your dealer immediately.

M1 Active Mk2 Reference Manual

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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-levelsource (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 asingle-channelpower amplifier of the same wattage feeding a passive crossover, as in other designs. New technology makes it possible to make thesehigh-wattageamplifiers 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 hifi receiver). Connect them only to theline-leveloutputs of such devices (+4 dBu nominal, +24 dBu maximum).

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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-specificelectronic 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-wovencarbon fiber. This material is 25% lighter than polypropylene with twice the stiffness for quicker transient response in thelow-to-midbassregion and vastly improved midrange intelligibility (over polypropylene at 2000 Hz). Thenon-wovencarbon fiber cone, along with the closed cell synthetic rubber surround, are both nearly impervious to ozone, direct sunlight, heat and humidity. Therefore, after an initialbreak-inperiod, the sound should remain virtually unchanged for the life of the product.

Alesis’ proprietary-designtweeter 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-distortionsignal 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 fornon-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. (Nonshielded 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

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About the M1 Active Mk2

THEM1 ACTIVEMK2 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-orderfilters 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-inamplifiers 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-ampsetup 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-frequencypolar response of the tweeter can be utilized down to a low 2000 Hz thereby mating more cohesively with the 6.5"non-wovencarbon 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.

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M1 Active Reference Manual