Krix MX-20 Modular Portable Speaker System Instruction Manual

MX-20, MX-30 & MX-40
INSTALLATION MANUAL

Congratulations on choosing Krix
Krix have been providing audio solutions for commercial cinemas for over 35 years, with loudspeakers being installed in over 3,000 cinemas in more than 30 countries worldwide. A large part of the success Krix has enjoyed in the commercial cinema market is due to the development of the infinite baffle wall concept.

The infinite baffle wall concept provides a solid wall or half-space that is continuous with the front face of the loudspeakers. This alleviates any sound leakage into the space behind the screen, which can affect sound clarity by mixing reflected sound with the direct sound from the loudspeakers. Chris has also undertaken extensive research and development on horn and waveguide loudspeakers, leading to improvements in efficiency, directivity, and distortion characteristics. Krix’s innovation has resulted in several patents in the area of constant directivity horns and has placed Krix at the forefront of technology and design in commercial cinema.

Both the infinite baffle wall and horn design technologies have been successfully combined in our Series MX range of dedicated home cinema loudspeaker systems. The MX loudspeakers are designed to be flush mounted into a false wall, with an acoustically transparent screen placed over the front, replicating the proven concept as used in commercial cinemas. The Series MX modular systems feature the left, center, and right screen loudspeaker modules and two passive subwoofer modules, all of the same height and depth. This modular concept not only simplifies the design and construction of the false wall at the front of the home cinema but also minimizes the depth required from the room. The front of each speaker is covered with acoustic absorbent material to absorb sound reflections off the back of the screen. This also assists with the acoustic treatment of the room to ensure better intelligibility and overall sound performance. The Series MX range delivers the visual experience and dynamic impact of real cinema at home.

Wallis Cinema, Noarlunga, South Australia. Commerical cinema installation featuring a ‘Baffle Wall’, Krix Commerical 4-Way loudspeakers, and dual 18” subwoofers.

ACOUSTIC CONSIDERATIONS

The acoustics of the room has a major influence on the overall performance of any audio system in a home cinema installation. Reflections off walls and ceilings, slap echo, and uncontrollable bass can all be detrimental to the overall clarity and intelligibility of the experience and therefore the overall enjoyment for the listeners. A room with mostly hard surfaces and glass can sound too “lively” with a reverberation time that is often excessively long. In such environments, the dialogue and soundtrack, in general, can lack definition and clarity. Conversely, a room that has an excess of heavy acoustic treatment around every wall can sound flat and unnaturally dead.

The ideal scenario is to create a balance between absorption and diffusion by adding sufficient soft material to reduce the reverberation time of the space, and strategically placed diffusion to maintain a natural sound and give the room a larger sense of space. Untreated, hard surfaces adjacent to the loudspeakers are not ideal. To get the best performance from your home cinema, it is recommended that you consult with an acoustic engineer to assist with the acoustic treatment of the space. Some suppliers of acoustic treatments offer a design service when using their products. A detailed plan of the room with all dimensions is generally required, which should also include the seating layout and speaker positions. As the Series MX loudspeakers are capable of producing much higher sound pressure levels (SPL) than conventional home entertainment systems, it is recommended that allowances are made in the room design and construction for soundproofing or isolation. Sound isolation is generally required to reduce or eliminate.
Note :- Soundproofing or isolation is very different from acoustically treating a room. It is a common mistake to concentrate on room isolation and not consider room acoustics.

AMPLIFICATION

To deliver Dolby®’s reference sound pressure levels (SPL) in the home cinema, three main design elements are critical to this outcome. The size of the room, the sensitivity of the speakers, and the power output of the amplifiers. The Series MX speakers and subwoofers have much higher sensitivity than typical hi-fi speakers. This means that the amplifier power requirements are not excessive, even when installed in larger than average room sizes. When used in a room of recommended size, the MX-20 Main speakers can be powered successfully with a mid to top-tier AV receiver.

The MX-30 system is best utilized in larger home cinemas and it is recommended that all speakers are driven with a separate processor and power amplifiers, rather than an all-inone AV receiver. Separate power amplifiers (including ones with multiple channels) have the capability to deliver more current and therefore produce the dynamics and impact desired for a true cinematic experience.

The MX-40 LCR modules require the use of an active crossover and bi- amplification. This configuration is also employed in commercial cinemas so that the low-frequency and high-frequency elements can be driven optimally. The recommended active crossover settings are stated on page 14. Under no circumstance should an MX-40 LCR loudspeaker be connected without the use of an active crossover, otherwise damage to the high-frequency element may result. It is recommended that the low and high elements of each speaker are driven by the same model of the amplifier to ensure the gain is identical. If different amplifiers are used please refer to the note on page 14. As the subwoofers in the Series MX systems are passive (not self-powered), an independent power amplifier, connected to the LFE channel(s) of the AV receiver or processor, is required to drive these units.

For best results with all MX series subwoofers, it is strongly suggested that a professional style power amplifier is employed which has a selectable output limiter and highpass filtering options. For more information regarding the configuration of these options, see the Equalisation section on Page 14.

The main speaker and subwoofer graphs on pages 6 and 7 show the recommended amplifier power for each Series MX model in relation to room size. The minimum power line denotes the amplifier power required to provide cinema Dolby ATMOS® reference levels (105dB mains, 115dB LFE). Anything above this will allow additional headroom.

MX SUBWOOFER AMPLIFIER POWER

SYSTEM DIMENSIONS

MX systems are designed to fit into a niche or cavity in the front wall. This cavity is located directly behind the screen (shown in Figure 1). Overall dimensions The choice of MX system needs to be considered in conjunction with the screen size. Spacer modules are available to increase the distance between the left and right modules to accommodate wider screen formats and improve left and right channel separation. The tables in Figures 2 & 4 show the overall dimensions along with recommended cavity size for each MX system. Use these dimensions as a guide to match up to your selected screen size:

| Minimum Screen Size
---|---
System| System Width| System Height| System Depth| Cavity Width| Cavity Height| Cavity Depth| 16:09| 21:09
MX20| 2210 mm| 1220 mm| 295 mm| 2260 mm| 1270 mm| 320 mm| 105″| 130″
MX30| 2865 mm| 1220 mm| 335 mm| 2915 mm| 1270 mm| 400 mm| 135″| 130″
MX40| 3165 mm| 1220 mm| 335 mm| 3215 mm| 1270 mm| 400 mm| 145″| 140″

SYSTEM POSITIONING

Vertical positioning

When planning a dedicated home cinema, consideration should first be made for seating locations followed by the screen size and position. Once these have been decided, the listening axis of the speaker should be considered (MX20 and MX30 500mm from base of speaker module or MX40, 750mm, figure 3). Try to position the speaker cavity behind the screen so that the listening axis of the speaker is within 10 degrees of the listener’s seated ear level. For secondary viewing rows, it is recommended to keep this angle within 20 degrees.
Care should also be taken to ensure the first ow of viewers do not obstruct the sound path for viewers behind them. Raising the platform height for subsequent rows can help to alleviate these issues.

| | | | | | | Minimum Screen Size
---|---|---|---|---|---|---|---
System| Spacer Width| System Width| System Height| System Depth| Cavity Width| Cavity Height| 16:09| 21:09
MX20| 200 mm| 2610 mm| 1220 mm| 295 mm| 2660 mm| 1270 mm| 120″| 130″
| 325 mm| 2860 mm| 1220 mm| 295 mm| 2910 mm| 1270 mm| 135″| 130″
MX30| 200 mm| 3265 mm| 1220 mm| 335 mm| 3315 mm| 1270 mm| 150″| 145″
| 325 mm| 3515 mm| 1220 mm| 335 mm| 3565 mm| 1270 mm| 160″| 155″
MX40| 200 mm| 3565 mm| 1220 mm| 335 mm| 3615 mm| 1270mm| 165″| 155″
| 325 mm| 3815 mm| 1220 mm| 335 mm| 3865 mm| 1270 mm| 175″| 165″

SCREEN WALL CONSTRUCTION

The construction of the false wall to suit the MX system is fairly straightforward. It is recommended that the designer should consider the need for sound isolation into adjoining rooms as applicable. For example, if the wall adjoins a utility room such as a laundry or garage then it may be deemed that sound leakage into these spaces is not an important consideration. Alternatively, if the wall adjoins a living space such as a bedroom or lounge room area then it may be beneficial to build the wall in such a way to reduce the sound transmission into the neighboring space. There are two recommended methods of constructing the screen wall depending on building constraints and budget. Extra care should be taken to ensure fixings have been properly anchored and that plasterboard sufficiently adheres to stud work. Any loose construction increases the chance of unwanted resonance.

Fixing the cavity directly to the rear wall is the simplest method, although increases the likelihood of sound transmission through to the adjoining rooms. This technique is outlined under the section Fixed directly to the rear wall.

To reduce the sound transmission as much as possible, it is recommended to create a stand-alone screen wall. This particular technique is outlined under the section Isolated from the rear wall.

Fixed directly to the rear wall

Using this construction method, the shelf studwork supporting the MX modules is fixed securely with construction adhesive in conjunction with screws or nails to the baffle wall and also to the rear wall of the adjoining room.

1. Fix the cavity frame to the rear wall. (Figure 5)
2. Erect a frame for the screen wall and fix this to the floor, ceiling, and adjoining walls. (Figure 6)
3. Fix noggins in-between frames so that plasterboard or engineered timber board can be fixed. At this point, it is recommended to insulate the void around the speaker cavity as much as possible using bulk insulation or similar. The more material placed into the cavity, the better for sound energy absorption. (Figure 7)
4. Finish the wall off using plasterboard or timber board on the wall panels and timber board on the cavity floor. (Figure 8) It is important to use a timber board with a minimum thickness of 16mm for the cavity floor. A hole for the speaker cabling is best placed at the front corner of the cavity floor.

SUBWOOFER SETUP AND CONFIGURATION

All Series MX systems feature a dual subwoofer configuration. The subwoofers are deliberately orientated in an asymmetrical “up” and “down” configuration that will help balance the in-room low-frequency response.
It is possible to wire up the two subwoofer loudspeakers in the following ways:

Each channel of a stereo power amplifier is connected to each subwoofer separately.
Utilizing a stereo power amplifier in the bridged mono configuration, both subwoofers are wired in parallel across a single pair of output terminals. Not all amplifiers support bridge mode, check your amplifier manual for details.
Utilizing a single amplifier channel, both subwoofers are wired in parallel across a single pair of output terminals.
Note – By wiring, the subwoofers in parallel, the load impedance presented to the amplifier is halved to 4 Ohms, which consequently demands double the output current from the amplifier. Care should be taken to ensure that the specifications of the amplifier explicitly allow the increased loading of 4 Ohms, especially when used in a bridged mono configuration.
It is strongly recommended to run separate cabling for all channels in the MX modular loudspeaker system back to the central amplifier rack to permit future flexibility with the wiring configuration.

WIRING

The Series MX systems are installer friendlywith convenient terminal placement allowing easy installation of wiring along the bottom front edge of the loudspeaker enclosures(Refer Figures 9 or 14)
MX40 – Left, center, and right main speakers require active crossovers and two amplifiers per channel, therefore 2 x 2 core or 1 x 4 core cable is required to connect to each loudspeaker module.

MX20 and MX30 – Left, center, and right main speakers only require one length of 2 core speaker cables to connect to each speaker. Processors, amplifiers, and other components may be mounted remotely in equipment racks at considerable distances from the screen loudspeakers. Therefore, the use of high-quality, flexible, multi-stranded copper cables of the suitable gauge is recommended for best performance.

For cable runs up to 24m in length, a minimum 14AWG gauge cable should be specified. Refer to the table below for the maximum recommended cable lengths for each speaker wire gauge. Thicker, heavier gauge cables have a lower AWG number. For longer cable runs ensure heavier gauge cables are used. If in doubt, consult your Krix authorized dealer or system designer for recommendations regarding the gauge of cable.

MAXIMUM WIRE LENGTHS

EQUALISATION

Krix constant directivity horns and waveguides utilized in the Series MX systems have an advantage over conventional loudspeakers as they deliver more direct sound to the listener with less sound reflected off the walls and ceiling. The baffle wall design of the MX system also launches the sound from a flat plane, ensuring the frequency response is unhampered by acoustic diffraction effects and front wall reflections associated with conventional home theatre installations. The MX systems are therefore less influenced by the acoustics of the room.
Before attempting to perform equalization of your processor or receiver, please ensure that adequate attention has been given to the acoustics of the room and acoustic treatment options have been explored. Equalization can only partially compensate for a cinema room with poor acoustics.
As an initial step, Krix suggests configuring your AV receiver/processor with manual equalization settings to achieve a simple and faithful reproduction of the source material. Automated equalization procedures may also be employed, but the results will vary depending on the algorithms and microphone placement techniques.

Speaker distances and dB levels

Automated speaker configuration systems are very good at setting the speaker distances (delays) and setting dB levels for each speaker in a system. If using this approach, it is advised to check the settings manually for any anomalies. In some instances, increasing the center channel level by 1-3dB is preferred for increased dialogue intelligibility. Adjusting the subwoofer level manually is often required to suit the listener’s preferences. Boosting or cutting the subwoofer level by up to 9dB is not uncommon to achieve the desired result.

Speaker size

Automated setup procedures may also be used to set the size of each speaker, but the results should be checked and adjusted where necessary. Although the MX-20, MX-30, and MX-40 main speakers are physically ‘large’, setting them to small allows the lower bass frequencies to be sent to the subwoofers that are better suited to reproducing the lowest frequency content.
MX-20 Main – recommended setting speakers to small with 60Hz crossover
MX-30 Main – recommended setting speakers to small with 40Hz crossover
MX-40 Main – recommended setting speakers to small with 40Hz crossover

Subwoofer power amp configuration

Limiter:

The use of a power amplifier’s soft limiter function is strongly recommended on MX subwoofers. If the power amplifier driving the subwoofers is inadvertently overdriven on program peaks, the use of an effective soft limiter will protect the loudspeaker driver against clipping damage and will also reduce the incidence of adverse distortion when the amplifier is faced with signals in excess of its peak rating.

High pass filter

The use of a high pass filter is advisable with MX subwoofers. By filtering out subsonic frequencies, the overall system power handling is improved. MX20 Sub – 25Hz high pass 24dB/Oct Butterworth MX30 Sub – 20Hz high pass 24dB/Oct Butterworth MX40 Sub – 20Hz high pass 24dB/Oct Butterworth

Dynamic Compression / Night Listening

The MX systems are capable of reproducing the full dynamic range of a movie, therefore it is recommended that dynamic compression or night listening mode settings are disabled in both the AV receiver/processor and blu-ray player configuration menus. This will allow the reproduction of the movie soundtrack’s full dynamic range, as the director intended.

Dynamic Equalisation / Loudness Controls

‘Loudness’ type settings adjust the equalization of the system by boosting the bass and treble due to the human ears’ lack of acuity over these frequency ranges at low listening levels. Unless you intend to do a lot of listening to low volume levels it is best to disable this setting to maintain a faithful reproduction of the source material.

Room equalization

The native response of the MX system is designed to be consistent across the frequency range, however, some room equalization is often beneficial in tuning the response of the system to the environment. Room equalization involves dealing with the somewhat complicated subject of room acoustics and to clarify this often-confusing subject it may help to consider the different characteristics of the room environment and system equalization separately.

Room size and ‘liveness’ / reverberation time

The reverberation time of the room is the time taken for reflected sound energy in the room to reduce to a low level. Highly treated rooms have lots of absorbing surfaces that are particularly effective at higher frequencies. This type of room can benefit from a lift in the treble to avoid the system sounding too dull or ‘soft’.

MX40 Active Crossover settings – The MX-40 LCR modules require the use of an active crossover. Please use the following crossover settings:

*Gain values assume that the same model of amplifier or gain matched amplifiers are used for low and high-frequency elements. If amplifiers with different gains are used, then the corresponding gain offset must be added to the active crossover gain values. Electrical or acoustic measurements may aid in determining the correct gain offset.

EQUALISATION

Alternatively, larger rooms may be perceived as sounding too bright when combined with speakers that have a flat frequency response so a gentle treble roll-off may be preferable. The MX systems have a slight treble roll-off and therefore will tend to sound most balanced in larger, moderately treated rooms. In smaller and/or well-treated rooms, some treble lift is recommended. Also, some treble lifts may be required to compensate for treble loss through perforated acoustic screens. Woven screens are acoustically superior and suffer from very little treble loss. Standing-wave issues Small to moderate- size rooms with standard height ceilings are prone to standing wave issues below 500Hz, resulting in peaks and dips in the system response. Automated DSP-based solutions can be good at addressing these issues but results will vary depending on the algorithms employed by the DSP and the number and positions of the microphone measurement points used during the equalization process. Small to moderate size rooms tend to skew the bass and mid-bass response of the system due to the close proximity of the sidewalls and ceiling to the speaker array. Applying some cuts to the mid-bass (100-250Hz) region in small to medium rooms can help to combat the issues mentioned above. Automated room correction and speaker equalization There are many room equalization products on the market that attempt to combat the issues highlighted previously, but these systems often target a flat frequency response which can sound too bright, forward, and harsh in an average home cinema environment. Some automated algorithms also cut too much energy out of the mid-bass region, resulting in a ‘thin-sounding system that lacks ‘warmth’ and ‘weight’. Listen for these issues when evaluating the results of an automated room correction system. Manual graphic equalization allows for a gentler equalization curve to be applied allowing the large ‘cinema sound’ of the MX system to be maintained. Below are some suggested equalization settings to use for the MX systems. Use these settings as a guide when manually equalizing an MX system without using an automated DSP, microphone-assisted setup procedure.

Highly treated room under 8m deep

Lightly treated room under 8m deep

Highly treated room over 8m deep

Lightly treated room over 8m deep

Krix Loudspeakers Pty Ltd
14 Chapman Road
Hackham SA 5163
Australia
T 61 8 8384 3433
F 61 8 8384 3419
listen@krix.com
krix.com

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