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Digital interface to handle connections between source and powered, active, DSP speakers

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#1
I was thinking about my dream setup just days after making an upgrade, as we often do here, and I ran realized something I’d never thought of.
A setup that I’ve dreamt up would have 5-7 custom two-way speakers with a two channel amp and DSP built into the speaker for crossovers. This much so far is all straightforward to me. What I don’t understand is what one would put between those speakers and the source, let’s say a computer. Lets also say this setup is a 7.1 surround sound system with four subwoofers, each of which is fed the same mono signal.
Put another way, what device would allow you to carry up to eight digital signals into 11 (7+4) enclosures from a computer or other device feeding it digital audio?
This may ultimately be an incredibly simple question, but I don’t exactly know what to call the device I’m looking for, making it difficult to find. The device should not have to have any DACs in it at all, as that conversion happens after DSP crossover that is integrated with each speaker.
 

digitalfrost

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#3
RME Digiface https://www.rme-audio.de/digiface-usb.html They're bit misleading calling it a "66-Channel 192 kHz USB Audio Interface".

From the manual:

Standard: 32 channels 24 bit, up to 48 kHz
Double Speed (S/MUX): 16 channels 24 bit 96 kHz
Quad Speed (S/MUX4): 8 channels 24 bit 192 kHz

Obviously ADAT devices are kinda expensive/hard to come by I guess. You can configure the Digiface to use an external clock signal, so I guess you could combine multiple interfaces if you have a digital external clock source.
 
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#4
Thanks for the replies. Not cheap but there are options out there... are there any threads I’m missing about the wisdom of putting your DAC/amp into a speaker as opposed to having a traditional “stack” where analog of traveling to speakers? I can see benefits of both.
 
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#5
It also occurred to me that a computer could potentially handle all of the DSP, leaving only DAC and and amplification external to a PC or source. This would require an interface with 18 channels in and out. Could an interface like the ones above be connected to achieve infinite channels? How would a PC manage to output the correct channels to the correct device if multiple interfaces are required?
 
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#6
Linux & Mac allow combining multiple output devices. Windows requires one of the Voicemeeter apps or similar. Either way, you'll need to do the config manually.

We should also note the high-end option, good for at least 32 channels: Dante/AES67.
 

Arnandsway

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#7
Take a look at the Okto Dac8 or the Motu Ultralite MK4. The Okto has been reviewed here and the Motu somewhere as well by @March Audio but I can't find the thread so quickly (on mobile)
 

digitalfrost

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#8
Linux & Mac allow combining multiple output devices. Windows requires one of the Voicemeeter apps or similar. Either way, you'll need to do the config manually.
I would not trust this to work.

You need to clock sync multiple cards, especially if you're using asynchronous USB. Also, depending on your DSP solution, you need a working WDM or ASIO driver that presents a single >= 18 channel interface to the DSP software. I think WDM is limited to 8 channels anyway.

Maybe @UliBru can tell us how we can do computer based DSP with 18 channels in/out?
 

somebodyelse

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#9
Using the PC for all the DSP is possible, but probably making trouble for yourself. Only pro audio interfaces can handle the necessary channel counts while keeping them in sync. ADAT and MADI interfaces usually come in blocks of 8 or 16 channels, while you only want 2 or 3 at a time. The networked interfaces @HammerSandwich mentioned (Dante, AES67, AVB) are probably the best fit as there are a few interfaces with low channel counts. Have a look at Dante AVIO adapters and virtual soundcard for something that might fit the bill - you'll need a network router with PoE for them, but not the specialised one you'd need for AVB. This probably rules out linux.

I think I'd stick the crossover DSP at the speaker for reliability if nothing else.
 

Krunok

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#10
Thanks for the replies. Not cheap but there are options out there... are there any threads I’m missing about the wisdom of putting your DAC/amp into a speaker as opposed to having a traditional “stack” where analog of traveling to speakers? I can see benefits of both.
You may want to check these links:

https://www.minidsp.com/applications/plate-amplifiers/pwr-ice-for-2way-speaker

https://www.minidsp.com/applications/plate-amplifiers/pwr-ice-for-subwoofer
 
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#11
This is actually exactly what I had in mind when posting. The trouble here is that most of audio components become tied to each other, replacing an amp means replacing the DAC and perhaps even worrying about changing DSP software, plate size, etc.

@somebodyelse make me think that perhaps solving this problem is more trouble than its worth for home audio.
 

somebodyelse

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#12
This is actually exactly what I had in mind when posting. The trouble here is that most of audio components become tied to each other, replacing an amp means replacing the DAC and perhaps even worrying about changing DSP software, plate size, etc.

@somebodyelse make me think that perhaps solving this problem is more trouble than its worth for home audio.
I think digital to (close to) the speaker's a pretty good idea, and not that much trouble. It's doing 18+ channels of DSP on Windows and finding a way to distribute it that I think is problematic, not least because I don't trust the WIndows audio subsystem to do it reliably.

The plate amps aren't actually that tightly tied when you look at them. They tend to keep the amp boards separate from the DSP/DAC, at least in the case of the MiniDSP ones @Krunok linked, and the Hypex FusionAmp range. If you're DIYing you can strip the boards from the plate and put them in a separate box, then just upgrade the amp or DSP as needed later. At the lower end you could use the BeoCreate or DAC+ DSP and a suitable amp.

It's a shame JBL didn't include digital inputs on the 305/308 as an alternative to their internal ADC.
 

pierre

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#13
It also occurred to me that a computer could potentially handle all of the DSP, leaving only DAC and and amplification external to a PC or source. This would require an interface with 18 channels in and out. Could an interface like the ones above be connected to achieve infinite channels? How would a PC manage to output the correct channels to the correct device if multiple interfaces are required?
there are plenty of interface with 24 (or more) channels out. Most of them have an integrated mixer than can route any entry to any other. RME or MOTU does that for sure. You can also mix in a DAW on your computer (you can also do the crossover in the daw).

I do all in a daw (reaper), mixing, crossover, upmixer and then convolution for room correction. I then send all channels to my rme and then analog to speakers.

this works very well but it not completely easy to setup.

be carefull that the number of channels claim by audio interfaces usually sum inputs and outputs counts You may also need to loopback from your interface and that could also divide by the number of useful channels.
let’s say you send a 7.1 to your interface. Get in back (+8) then split signals and generate 18 outs, that make it 34 channels already and you likely wants a few extra for microphone or headsets.
 

ernestcarl

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#14
there are plenty of interface with 24 (or more) channels out. Most of them have an integrated mixer than can route any entry to any other. RME or MOTU does that for sure. You can also mix in a DAW on your computer (you can also do the crossover in the daw).

I do all in a daw (reaper), mixing, crossover, upmixer and then convolution for room correction. I then send all channels to my rme and then analog to speakers.

this works very well but it not completely easy to setup.

be carefull that the number of channels claim by audio interfaces usually sum inputs and outputs counts You may also need to loopback from your interface and that could also divide by the number of useful channels.
let’s say you send a 7.1 to your interface. Get in back (+8) then split signals and generate 18 outs, that make it 34 channels already and you likely wants a few extra for microphone or headsets.

I suppose you mean something like this?

https://www.bhphotovideo.com/c/product/1087412-REG/motu_9335_usb_avb_audio_interface_with.html
 

somebodyelse

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#15
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#16
If this is for movies your DAC will need at least a Dolby surround decoder. Finding a DAC with that and 7 xovers may be a problem.
 
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