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Active home audio setup with software DSP

Home Theatre Systems


Well-Known Member
Jan 13, 2008
I don't know if something similar has been posted before.

May not be the most audiophile method, but provides for infinite tuning options.

I advice not to try this with any existing factory built/branded speakers by removing the passive crossovers. Any wrong setting can easily blow the tweeters and midrange drivers.

Source: Laptop
Software: JRiver Media Center with in-built software DSP functions or foobar with external plugins.
I prefer the jRiver

Any USB 7.1 Sound Card for 3-way and 5.1 for 2-way:
I used it with ASUS Xonar U7 soundcard.

Any 4/6-channel power amplifier with dedicated analogue inputs.
I used a custom designed 8-channel power amp.

3-way or 2-way

JRiver Media Center and foobar2000 are two versatile media players (though foobar is restricted to audio). Both offer support for multi-format playback including hi-resolution files, a number of in-built plug-ins and support for external plug-ins, including support for VST. Other features include WASAPI and ASIO support for both universal and hardware specific devices. All the processing is done in the digital domain.

Harnessing the DSP features:
JRiver Media Center: Its inbuilt DSP plugin offers a wide selection of effects including Parametric Equalizer

Foobar: You need external components for activating DSP features. Some of the components for foobar are, the free plugin xover which does not need VST support: foo_dsp_xover or Voxengo DSP plugins like Voxengo GlissEQ/Voxengo Parametric EQ etc.VST plugins, AU plugins, Pro audio plugins, Downloads - Voxengo

So how are these features useful for running an active setup.

I will at present explain with JRiver as the player and DSP, soundcard as the DAC for processing multi-channel analogue outputs and the multi-channel power amplifier for driving the speakers actively.

The connection chain is as follows:
1. Set the USB soundcard to 7.1 output in the windows sound properties.

2. Use 3 pairs of RCA cable to connect the sound card low level analogue outputs to the 3 stereo low level (RCA) analogue inputs of the power amplifier.

3. Connect the subwoofer/center channel output from the soundcard to the subwoofer amplifier if you have one, else leave it alone. In my case I will use it after getting a mono amplifier.

4. Connect each stereo channel output of the amplifier individually to the midbass, midrange and the tweeter drivers of the speakers.

JRiver settings:

1. Bypass windows sound mixer (direct sound) by selecting WASAPI or ASIO (soundcard, in this case Asus Xonar) as the audio playback device under Player Playback Options Audio Device

2. Next under Player DSP option select Output Format in the left window. In the right window (i.e Output Format properties, set Output Encoding to None and Channels to 7.1 and Mixing to No Upmixing or Downmixing. Also enable Clip Protection

3. Next in the left window, select Parametric Equalizer and this is where the fun starts.

4. Parametric EQ allows many features some of which includes.
a) Adding more channels and assigning the main left/right stereo channels to any of the added channels and passing the signal through the multi-channel outputs selected in Output Format which has been set to 7.1, meaning Left Channel, Right Channel, Left Surround, Right Surround, Rear Left Surround, Rear Right Surround, Center and Subwoofer.
b) Setting low pass/high pass/band pass filters for individual channels with slope and gain settings.
c) Polarity setting for each channel
d) Assigning any number of individual frequency bands within the assigned frequencies to set the Q.
e) plus features like time delay, individual gain control and more.

5. I have assigned the Left and Right channels to the midbass, Left and Right Surround to the midrange and Rear Left and Right Surrounds to the tweeters. At present as I do not have a subwoofer connected, I have not assigned any connection to the center and subwoofer.

7. There are many other DSP functions that JRiver offers.

So by doing the above, we essentially duplicate the stereo signal into multiple signals, in this case 3-pairs of stereo signals. We then digitally high pass/low pass or bandpass these stereo signals (i.e apply active crossovers) and use more filters/slopes etc before assigning them to soundcard via the USB connection for changing to analogue (DAC) and then outputting through the multi-channel output of the soundcard.

The low-level analogue signals are then received by the RCA inputs of the multi-channel power amplifier and sent as amplified analogue signals to the individual speakers.

Some pics of the custom made 8-channel power amplifier. A single transformer and 4 independent boards based on the TDA7294 class AB class audio amplifier IC.

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