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Old 19th January 2012, 12:19 PM   #11
oublie is offline oublie  United Kingdom
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That's my plan the advantages of such a cheap implementation of active crossovers and the possible power of drc etc could lead to an even cheaper active crossover solution than what is currently available. £25 per speaker for active crossovers sounds pretty good to me. And of course another raspberry used to hold and control all my music or video would be a godsend.
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Old 19th January 2012, 01:27 PM   #12
elizard is offline elizard  Canada
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Originally Posted by planet10 View Post
Bluetooth doesn't have the bandwidth for decent fidelity

dave
Not necessarily true. BT 2.0 + EDR has a theoretical peak or 2/3Mbps at short ranges. I'm assuming that also includes overhead which is some 30% or so. Most of my lossless music is around 1000-1200kbps, but that is both channels. Assuming you were able to send the channels individually, you should be fine.

That being said, I'd never try it. You are bound to run into issues such as latency differing between the two channels (remember, the transmission isn't real time and as such the latency and bandwidth are not guaranteed). I'm sure I could think of other reasons why BT is a bad idea
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Old 26th January 2012, 09:59 PM   #13
ChrisPa is offline ChrisPa  United Kingdom
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Originally Posted by oublie View Post
That's my plan the advantages of such a cheap implementation of active crossovers and the possible power of drc etc could lead to an even cheaper active crossover solution than what is currently available. £25 per speaker for active crossovers sounds pretty good to me. And of course another raspberry used to hold and control all my music or video would be a godsend.
it's got to end up costing considerably more than that per speaker. The final digital sound quality is in the dac, so you'll need a good quality dac per driver.

So maybe good value for dsp but only part of total cost
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Old 27th January 2012, 09:05 AM   #14
phofman is offline phofman  Czech Republic
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Originally Posted by oublie View Post
That's my plan the advantages of such a cheap implementation of active crossovers and the possible power of drc etc could lead to an even cheaper active crossover solution than what is currently available. £25 per speaker for active crossovers sounds pretty good to me. And of course another raspberry used to hold and control all my music or video would be a godsend.
How would you plan on distributing the input data to multiple raspberries which each running independent clocks? I am afraid you would have to use ASRC (e.g. libsamplerate) on the front, e.g. using the jackd2 network plugin. Quality resampling plus quality filtering - I do not know if the ARM CPU of RP (no GPU accelleration) could handle the load..
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Old 27th January 2012, 10:25 AM   #15
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It would be absolutely fantastic. No wires, active crossover, drc, etc.. I am tuned.
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Old 31st January 2012, 12:37 PM   #16
oublie is offline oublie  United Kingdom
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Originally Posted by phofman View Post
How would you plan on distributing the input data to multiple raspberries which each running independent clocks? I am afraid you would have to use ASRC (e.g. libsamplerate) on the front, e.g. using the jackd2 network plugin. Quality resampling plus quality filtering - I do not know if the ARM CPU of RP (no GPU accelleration) could handle the load..
ATM clocks would be my biggest concern it may be that i actually do analogue digital to analogue conversion but of course time will tell. Early days, I'll know more once I get my hands on a few raspberries.
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Old 31st January 2012, 01:36 PM   #17
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ATM clocks would be my biggest concern it may be that i actually do analogue digital to analogue conversion but of course time will tell. Early days, I'll know more once I get my hands on a few raspberries.

What is 'analogue digital to analogue conversion'?

Also, how would multiple separate software (or hardware for that matter) ASRCs solve the clock distribution issue either for that matter? If you want master clock sync between the RPi mounted at left/right speakers you'd need to force that issue more directly imo.

Is the clock sync between the DAC for each speaker a big issue? As long as there is a matching amount of audio signal buffered at each localised RPi/DSP module AND you have a properly implemented network with very low packet loss/latency tehn you should negate any time delay between audio from L/R speakers. The phase noise and jitter on the digital signal leaving the RPi for digital to analogue conversion is then mainly dependent on the implementation of audio source/DAC after the RPi surely?

Maybe I'm miles off target but I didn't think that jitter or phase noise of digital signal for left signal relative to data for right signal was critical. In my mind this is a constant time delay that could be fixed simply and also likely totally swamped by room interaction issues.

It's all in theory till we get one in our hands and there are a lot of opportunities we're going to get by having this type of hardware available at such an accessible price point!
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Old 31st January 2012, 03:35 PM   #18
oublie is offline oublie  United Kingdom
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As this is planned for a home theatre environment, take the analogue feeds from the av processor feed them into an analogue input on the raspberry and the filter the signal to provide the relevant frequencies and adjustment before outputting as an analogue signals to the amps.
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Old 31st January 2012, 09:59 PM   #19
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As this is planned for a home theatre environment, take the analogue feeds from the av processor feed them into an analogue input on the raspberry and the filter the signal to provide the relevant frequencies and adjustment before outputting as an analogue signals to the amps.
Ah ok. I can understand what you're trying to do.

I would look for an adc designed for audio rather than the one onboard the RPi. I am sure the results would be less than satisfactory feeding line out straight into the GPIO port of the RPi.

Honestly the minidsp devices have all of what you're after, already on a single board. To have ADC -> RPi -> DAC and the associated power supplies you'll have a pretty complex system with non trivial amount of work involved in the hardware implementation, before you can even try to set up the software on the RPi.
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Old 31st January 2012, 10:20 PM   #20
oublie is offline oublie  United Kingdom
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I've been doing something similar for quite some time under windows with a single machine, I'm aware of mini dsp and other similar solutions but I'd like to try.

There really isn't any difference between this and what a minidsp does apart from the facility for more channels
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