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DBA (Double Bass Array) audio processing (TPF, delay, invert)

Former Member

Like most hifi enthusiast, i have problems with bass reflection of the walls of my listening room, resulting in standing waves.

A solution would be to drive a loudspeaker near the back wall with an delayed, inverted signal of the original fron speakers, to cancel the bass.

Maybe a Raspberry Pi with the Wolfson Audio Card is able to do that.

The card must be configured to filter out all frequenciey below 200Hz, delay the signal about 1ms (must be adjusted exactly accoring to the travel time of the sound through the room, invert it and drive a loud speaker.

 

Is there anyone out there who could give some information on how to do that?

Especially the programming of the integrated DSP for the delay seems to be complicated.

 

The only "professional" solution i found is the "E-Trap", an US product which costs around $2000.-

If this could be made with a pi, i think a lot of people would pimp there listening rooms with such a solution.

Parents
  • 0

    So far I haven't seen any public access to Wolfson tools to programme the DSP in the WM5102 chip.

     

    The data sheet includes this not very enouraging pragraph:

     

    DSP firmware can be configured using Wolfson-supplied software packages. A software programming

    guide can also be provided to assist users in developing their own software algorithms - please

    contact your local Wolfson representative for further information.

     

    My suspicion would be that the design tools are not really intended for use by the general public (it's pretty expensive to develop nice friendly tools for DSP development).

    Unless you are an experienced DSP developer I doubt if it would be worth your while attempting to get Wolfson to provide the tools.

     

    Mind you - if you are interested in a better sound I reckon you will gain far more by using physical room tuning methods (bass traps, curtains, second hand sofas etc) than processing the signals. To my ears the best sound comes from the least processing.

     

    MK

Reply
  • 0

    So far I haven't seen any public access to Wolfson tools to programme the DSP in the WM5102 chip.

     

    The data sheet includes this not very enouraging pragraph:

     

    DSP firmware can be configured using Wolfson-supplied software packages. A software programming

    guide can also be provided to assist users in developing their own software algorithms - please

    contact your local Wolfson representative for further information.

     

    My suspicion would be that the design tools are not really intended for use by the general public (it's pretty expensive to develop nice friendly tools for DSP development).

    Unless you are an experienced DSP developer I doubt if it would be worth your while attempting to get Wolfson to provide the tools.

     

    Mind you - if you are interested in a better sound I reckon you will gain far more by using physical room tuning methods (bass traps, curtains, second hand sofas etc) than processing the signals. To my ears the best sound comes from the least processing.

     

    MK

Children
  • 0 in reply to michaelkellett

    Why do you think it would be so difficult to program that DSP? I have some experience with Soundblaster Audigy DSP (using the opensource "kX" drivers). If there is a instruction reference, compilator and a tool to load the compiled data into the DSP, you don't need anything more image. All audio DSPs work in a similar way, just the possibilities, instructions and registers are little different.

  • 0 in reply to Marki555

    The problem is that the manufacturer (Wolfson) does not seriously support user programming of the DSP and the "instruction reference, compilator and a tool to load the compiled data into the DSP" are not readily available.

     

    If you know how to get hold of the tools for this device perhaps you would be kind enough to share.

     

    MK

  • 0 in reply to michaelkellett

    Have anyone actually tried to request the required information from Wolfson?

    In the meantime I have gone through all 300 pages of the datasheet... The DSP microcode is loaded just by writing into registers, so that should be possible from RPi. Ideally driver should have a function to load a binary firmware there but if not, we should be able to do it via i2c/spi as that is available to the linux.

    The only missing thing is the instruction reference, or "Programming guide" as referenced from the datasheet. I will try to write them an email if it is possible to get it. I tought that for my project (3-way stereo crossover) I should be OK with 4x EQ and 4x LHPF, but it seems these are not suitable as are only 6 dB/octave.