Did you know that M/S-2150 X can be used to design a multi way loudspeaker system?

M/S-2150 X internal floating point processor is so powerful that it can design low-pass, high-pass and band-pass crossover filters on the fly while you listen to your favorite track. This is the only amplifier on the market that can, in a split of a second, adjust crossover filters and allow you to instantly perform a listening test to evaluate the effects of the change made to crossover filters.

Eliminate your loudspeaker passive crossover filters and connect your drivers directly to the power source for perfect power transfer and control. Passive crossover filters are built with components whose parameters change with time and temperature. These passive crossover components are placed between your power source and your loudspeaker drivers. They interfere with the power transfer and therefore they significantly affect the quality of your sound reproduction system.

To further enhance your multi way loudspeaker system design, each M/S-2150 X comes with built in 12-band parametric Eq on each channel.

Two way or bi-amplified systems require four channels of amplification or two stereo amplifiers. There are two basic ways of powering a two way system:

1.      Horizontal
2.      Vertical

In a horizontally powered two way system one amplifier is used to power left and right channel low frequency drivers (woofers), and another amplifier is used to power left and right channel high frequency drivers (tweeters).

In a vertically powered two way system one amplifier is used to power the left channel woofer and tweeter, and another amplifier is used to power the right channel woofer and tweeter.

In a multi way system, including a two way system, audio signal has to be connected to all amplifiers. M/S-2150 X digital audio signal connection is shown in Fig.1. AMP-1 is selected to be M-2150 X and is configured as master unit. AMP-2 is selected to be S-2150 X and is configured as slave unit. Digital audio signal, usually CD player output, is connected to AMP-1 digital input 1. AMP-1 digital output is connected to AMP-2 digitalinput 1. In this way both amplifiers receive the same audio signal.

Fig.1. Audio signal and control signal connection.

AMP-1 RS232 AUX has to be connected to AMP-2 RS232 Input connecter. This connection allows AMP-1 to control AMP-2. All master level, mute and standby functions are passed from AMP-1 to AMP-2. In this way user can use only the master amp to change systems level, mute and to toggle standby mode on and off. For this purpose AMP-1 has to be configured as master unit and AMP-2 has to be configured as slave unit. To set an amp to master or slave mode go to COM menu and select MASTER or NORMAL (slave) setting (Fig2). For AMP-1 set MASTER mode and for AMP-2 set NORMAL mode.

Fig. 2. COMM menu

Connections and COM menu configuration, as described in this section, have to be implemented for both horizontal and vertical bi-amplification.

Horizontal bi-amplification example

In this example M-2150 X is used to power the tweeter section on both channels and S-2150 X is used to power the woofer section on both channels. M-2150 X should be configured as master unit and S-2150 X should be configured as slave unit (see previous section).

   We assume the following system parameters:

1.      Crossover cutoff frequency of 1000 Hz.

2.      6th order Butterworth Squared crossover filter

3.      Tweeter section delayed for 0.12 msec – driver time alignment

4.      Woofer section attenuation of -1.4 dB – driver level balancing

5.      Parametric Eq can be used to adjust certain frequency range.


Connecting M/S-2150 X amplifiers to your loudspeaker system

In this example M-2150 X is used to power high frequency drivers (tweeters) and S-2150 X is used to power low frequency drivers (woofers). Connection diagram is shown in Fig. 3 and 4.

Fig. 3. M-2150 X as master unit and S-2150 X as slave unit in horizontal bi-amping

Fig. 4. Loudspeaker connection in horizontal bi-amping

Audio Signal Routing

Make sure that InOut menu is set as shown in Fig. 5. In this way both amplifiers will output left and right audio signal to their respective output channels.

Fig. 5. InOut menu of AMP-1 and AMP-2 for horizontal bi-amping.

Setting AMP-1 Crossover Filter parameters

Since AMP-1 (M-2150 X) is connected to tweeter section of both loudspeakers, crossover filter has to be set to high-pass for both left and right channel. Crossover frequency and filter slope is loudspeaker dependent. In this example we assume crossover frequency of 1000 Hz and filter slope of 72 dB/octave or equivalent to 6th Butterworth Squared filter order.

To access the CRO option on AMP-1 use IR controller to enter the main menu screen and scroll to the right to place the cursor on CRO and then press enter. This action will display the CRO menu as shown in Fig.6.

Fig. 6. CRO menu

This screen shows that there is no crossover filter selected therefore both Left and

Right channel will output full frequency range signal. Place the cursor next to field 2 and use UP and DOWN buttons to scroll through all possible CRO presets. Note that when this field displays Bypass edit control (field 3) is not visible. To select/engage displayed preset press ENTER button. Selected CRO preset will be displayed in field 1.

In this example we use CRO preset #1. To edit CRO preset #1 scroll through field 2 until Preset #1 is displayed. Place cursor over EDIT (field 3) and then press ENTER button. The following screen will be displayed

Fig.7 CRO EDIT menu for AMP-1

Field 1 and 3 display left and right channel crossover filter assignment. To change this field place the cursor next to it and press ENTER button. This field can display BYPASS, BUTT and BUTTSQ options. When BYPASS is displayed EDIT filed (2/4) is not visible. When BUTT (Butterworth filter type) is displayed and when EDIT option is entered Butterworth filter design screen for selected channel will be displayed. When BUTTSQ (Butterworth Squared filter type) is displayed and edit option is entered Butterworth Squared filter design screen for selected channel is displayed. For this example select BUTTSQ filter type for both left and right channel.

Place the cursor over field 2 (Fig. 7) and press ENTER to edit left channel crossover filter parameters. The following screen will be displayed.

Fig. 8. Left and Right channel CRO parameters for AMP-1

Use LEFT/RIGHT buttons to place cursor over 1,2,3,4 and 5 fields.

Field 1. Use this field to assign filter type to selected channel. Place cursor over this field and by using UP/DOWN buttons scroll through all possible filter assignments. LP low-pass, HP high-pass, BP band-pass and “--” no filtering can be assigned to each channel. Set this field to HP high-pass option.

Field 2. This field is not enabled when HP or “--” option in field 1 was selected.

Field 3. Use this field to select high-pass filter order for selected filter type. If BUTT filter was selected this field could be set to any number between 1 and 12 (first and twelfth order) in increments of 1. If BUTTSQ was selected this field could be set to any number between 1 and 6. In BUTTSQ case two sections of Butterworth filter are cascaded to form Butterworth squared filter. Therefore BUTTSQ filter order of n corresponds to BUTT filter order of 2*n. For example, if BUTTSQ filter order is set to 6 then the slope of this filter would be the same as the slope of BUTT filter with filter order of 12. Set this field to 6.

 4. This field is not enabled when HP or “--” option in field 1 was selected.

 5. Use this field to set high-pass filter cutoff frequency. Filter cutoff frequency can be set to any value between 10 and 24000 Hz in increments of 1 Hz. This field is also used to set higher cutoff frequency of band-pass filters. This field is not enabled if LP or “--” option in field 1 was selected. Set this field to 1000.

Go back to the previous screen. Place the cursor over field 4 (Fig. 7) and press ENTER to edit right channel crossover filter parameters. Set the right channel crossover parameters to exactly the same values as for the left channel.

Setting AMP-2 Crossover Filter parameters

Repeat the same process for AMP-2 and set left and right CRO parameters to the following values:

Fig. 9. Left and Right channel CRO parameters for AMP-2

Note that both channels of AMP-2 are set to low-pass, 6th order Butterworth Squared filter.

Engage CRO filters

To engage designed CRO filters enter CRO menu screen, on both amps, and set field 1 to Preset #1.

Fig. 10. CRO Menu

As soon as Preset #1 is displayed in field 1, all crossover filters are inserted into audio signal path and system is ready for listening tests.
For more details on how to use CRO filter package please refer to M/S 2150 X Manual.

Time Alignment

M/S-2150 X offers system time alignment with a resolution of approximately 10 micro seconds. In this example we have assumed that, in order to have proper time alignment, tweeter section has to be delayed for 0.12 msec. To set system time alignment use DELAY menu option. Delay time settings for AMP-1 are shown in Fig. 11 and delay time settings for AMP-2 are shown in Fig. 12.

Fig. 11. AMP-1 DELAY menu

Fig. 12. AMP-2 DELAY menu

With these delay settings both left and right channel tweeters will be delayed for 0.12 msec with respect to both woofers. Delay times can also be changed on the fly for instant listening evaluations.

Level Balance

M/S-2150 X offers system level balancing with a resolution of 0.1 dB. In this example we have assumed that woofer section has to be attenuated for -1.4 dB. To set system level balancing use LEVEL menu option. Level settings for AMP-1 are shown in Fig. 13 and delay time settings for AMP-2 are shown in Fig. 14.

Fig. 13. AMP-1 LEVEL menu

Fig. 14. AMP-1 LEVEL menu

With these level settings both left and right channel woofers will be attenuated for -1.4 dB with respect to both tweeters. All system levels can also be changed on the fly for instant listening evaluations.

Final System

At the end of the design process we have created a two way system with perfect driver (woofer and tweeter) time alignment and perfect driver level balance.

If listening tests or acoustical measurement suggest that certain frequency range needs to be changed M/S-2150 X offers 12-band parametric EQ per channel. Any of the available filters can be tuned to specific frequency with user defined Q factor and filter gain/attenuation.

For more sophisticated approach to solving room acoustics problemsTact offers a range of processors such as: 2.0, 2.0 S, 2.2 XP and TCS MKII.

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