User manual ALESIS 7-51-0092-D

TM REFERENCE MANUAL © 2001-2005 ALESIS CORPORATION Alesis M1 Active Mk2 Reference Manual © Copyright 2001-2005, Alesis Studio 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: Website: info@alesis.com http://www.alesis.com Contents/Safety Warnings CONTENTS Introduction Unpacking and Inspection Inside your new speakers About Nearfield monitoring Avoiding reflections in the studio Stereo nearfield placement of the M1 Active Mk2 Connections Setting the Input Level control 2 9 10 15 17 20 26 28 ABOUT THE M1 ACTIVE MK2 ...............................................................9 SPEAKER INSTALLATION.................................................................... 17 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 Maintenance Enclosure Transducers Crossover section Amplifier Section Acoustic Section General 39 40 42 42 43 43 43 43 SPECIFICATIONS ................................................................................42 INDEX.............................................................................................. 44 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 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 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 hifi 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. (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 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 Re flec tion 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. Direct Path le onso ids C h Avo t Pat Direc 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. r ito on ft M Le Ri gh tM on ito r 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 offaxis 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 setup 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