Crossover in digital domain?

[Also posted to music-dsp mailing list]

Hi,

I'm playing around with my bi-amping audio system [1] and an idea popped 
into my head: instead of feeding the same signal to both HF and LF 
drivers and relying on the crossovers built into the speakers, why not 
have a crossover in the digital domain and use two DACs each feeding a 
separate amplifier?

[1] Squeezebox -> Art DI/O DAC -> Rotel RA820A (modified)(HF) + Rotel 
RB850 (LF)

I had a quick google around and found several devices that have analogue 
inputs and analogue outputs, but I couldn't find anything that simply 
takes a digital input signal and filters it digitally, producing a LF 
and HF digital output.

Does anyone know of such a device? How easy would this sort of thing be 
to build?

Thanks,

R.
-- 
http://robinbowes.com

Robin Bowes wrote:

(snip)

> I had a quick google around and found several devices that have analogue 
> inputs and analogue outputs, but I couldn't find anything that simply 
> takes a digital input signal and filters it digitally, producing a LF 
> and HF digital output.

Motorola has an application note for the 56001 for a graphic 
equalizer.  I don't remember if the I/O was analog with 
appropriate A/D and D/A converters or digital.  It seems that 
the 56001 is fast enough for a stereo equalizer with a 
reasonably number of bands, so should easily be enough for a 
crossover.

-- glen

Robin Bowes <robin-news@robinbowes.com> wrote in news:JygHd.11$Jo6.0
@newsfe2-gui.ntli.net:

> [Also posted to music-dsp mailing list]
> 
> Hi,
> 
> I'm playing around with my bi-amping audio system [1] and an idea 
popped 
> into my head: instead of feeding the same signal to both HF and LF 
> drivers and relying on the crossovers built into the speakers, why not 
> have a crossover in the digital domain and use two DACs each feeding a 
> separate amplifier?
> 
> [1] Squeezebox -> Art DI/O DAC -> Rotel RA820A (modified)(HF) + Rotel 
> RB850 (LF)
> 
> I had a quick google around and found several devices that have 
analogue 
> inputs and analogue outputs, but I couldn't find anything that simply 
> takes a digital input signal and filters it digitally, producing a LF 
> and HF digital output.
> 
> Does anyone know of such a device? How easy would this sort of thing be 
> to build?
> 
> Thanks,
> 
> R.

You can do this with our dspstak family of boards. We have an S/PDIF 
board as well as analog ADCs & DACs. We are working with the Visual Audio 
group at Analog Devices that will allow you to create these kind of 
systems graphicalkly as well.

-- 
Al Clark
Danville Signal Processing, Inc.
--------------------------------------------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

It is pretty common to use digital crossovers in the installed sound market 
(think stadiums, sports arenas, etc.) and even in high-end home audio.  The 
filtering requirements are quite simple, but finding something with the right 
form-factor and price may be a challenge.

For a commercial product, check this out:
http://www.bss.co.uk/includes/product_list_include.aspx?header_id=6&archived_flag=0
but it may not be geared exactly to your market.

A DSP evaluation board with digital audio I/O may be the best bet if you like to 
program.  Or you may be able to find PC software that allows real-time 
filtering.

"Robin Bowes" <robin-news@robinbowes.com> wrote in message 
news:JygHd.11$Jo6.0@newsfe2-gui.ntli.net...
> [Also posted to music-dsp mailing list]
>
> Hi,
>
> I'm playing around with my bi-amping audio system [1] and an idea popped into 
> my head: instead of feeding the same signal to both HF and LF drivers and 
> relying on the crossovers built into the speakers, why not have a crossover in 
> the digital domain and use two DACs each feeding a separate amplifier?
>
> [1] Squeezebox -> Art DI/O DAC -> Rotel RA820A (modified)(HF) + Rotel RB850 
> (LF)
>
> I had a quick google around and found several devices that have analogue 
> inputs and analogue outputs, but I couldn't find anything that simply takes a 
> digital input signal and filters it digitally, producing a LF and HF digital 
> output.
>
> Does anyone know of such a device? How easy would this sort of thing be to 
> build?
>
> Thanks,
>
> R.
> -- 
> http://robinbowes.com 

Google for BruteFIR as a PC software that enables you to build a
digital crossover by yourself. BruteFIR is Open Source and free.
Uli Br=FCggemann