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General discussion/planning for "fully digital" DIY speaker - DAC boards, protocols, interfaces etc

Shefffield

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Hello forum,

given all the available DIY boards and modules, it should be possible and not overlay complicated to build a DIY speaker that's pretty much fully digital. With that I mean: You connect it to a computer and you're done.

Picking good options out of the vast selection is quite a challenge though.

Background about the speaker concepts I play around with: They are generated using Acourate software, they use digital crossovers and therefore need a dedicated signal line for every single channel. I'm currently planning a 4-way concept, so we're talking 8 DAC channels and 8 amplifier channels.

Wondom seems to have a comprehensive selection of DAC boards, volume control boards and class D amps. Even DSP is available, but not necessary for my concept. For amps the choice is also massive, as already discussed here in other threads.

With amplifier modules and DAC boards integrated into the speakers, what's a good way to get the digital signal from the head unit (PC) to the speaker? I'd rather not run some 3-5 m long USB connections with their badly designed plugs. How about I2S? (https://www.boomaudio.de/wondom-s/pdif-i2s-audio-signal-konverter) Or is a simple SPDIF connection easier to handle - given that I equip the PC with a sound card that can supply enough outputs?
 

voodooless

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If you don't want long cables, consider wireless. If you're willing to go all-in, adding a streamer is basically trivial. That leaves syncing up the speakers. Usually, this is done using SPDIF between the speakers, either via AES or optical. You can also op for SPDIF input if you still want to use a cable. I2S is definitely not recommended. It's made for short distances only. Even better would be DIY modules with WISA support.

Look at something like Hypex Fusion. It gets you up to 3 high-quality channels of amplification and DSP.
 
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Shefffield

Shefffield

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I don't trust wireless since I read that Bluetooth uses a lossy compression algorithm. A streamer is out of the question because I run my own digital crossover and room correction filters. A PC as head unit is fine for my anyway, I just don't see a need for a streamer. That's just a piece of audio hardware that aims to make life a little easier and is prone to getting obsolete in a very short time.

I'm fine with long cables, but would like to find a well suited type. Like MADI or AWB/Dante like solutions from the pro audio world, just not as much overkill.

DSP is also something I don't consider any more, because the digital filters that Acourate generates are so much more powerful. We're talking about linear phase, subtractive 200 dB/oct crossovers that include time alignment and room correction. Generic DSP boards can't come anywhere near that.
 

voodooless

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So you just want 8 channel DAC and amps? The rest you do on the PC? And then one cable into each speaker?
 

LightninBoy

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Curious, would a given speaker get all channels but know its only supposed to play a certain channel? Or would there be some device directing only its channel info to it. If its the latter, how will you connect it to the PC? Will you need a USB for each speaker?
 

voodooless

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Curious, would a given speaker get all channels but know its only supposed to play a certain channel? Or would there be some device directing only its channel info to it. If its the latter, how will you connect it to the PC? Will you need a USB for each speaker?
I would actually connect them using CAT6/7. Each cable pair can act as one AES channel. You can loop one speaker to the other. On the PC side you’ll need some 8 channel thing with adapter to RJ45.
 
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somebodyelse

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I'd probably go the FusionAmp route too - the digital connection options are covered in their manual.

HifiBerry'd BeoCreate and Amp100 plus DSP board can use toslink input and between the speakers, and optionally a Pi for network streaming.

There are a couple of standards for connecting multiple AES digital channels using DB25 connectors if you're happier with those. I think Meridian used AES over RJ45 as @voodooless suggests too. There are also the multichannel network audio protocols from the pro side - Dante, AVB, AES67 - which you could use to send audio to the speakers if you can find a receiver that meets your needs. Dante's proprietary but the others have had exaple implementations on the BeagleBone using its TDM interface to connect to the ADC/DAC chips.
 

voodooless

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I think the OP does not want any of these options due to use of software DSP to create his ring-machines (aka brickwall filters for speaker crossovers)
 

LightninBoy

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Since the OP titled this "general discussion" for fully digital speakers - let me throw out what I think would be the ideal digital speaker solution.

I believe we are too locked into the idea of splitting the audio upstream and sending a dedicate channel stream to each speaker via a dedicated wire. Instead, I think the ideal digital speakers should be networked via ethernet or wireless. The entire signal (all channels) is streamed to each speaker. You configure each speaker to a role (Front left, Front right, Center, LFE etc.) and the speaker plays back the appropriate channel. Onboard DSP enables crossover, PEQ, and timing adjustments.

A hub app (running on phone or web) enables speaker configuration. The only connection your computer or AVR needs is a a network connection (either wired or wireless).

If using wired network connect, speakers need two wires: power and ethernet. If using wireless, they only need power.

This is probably a pipedream for proprietary multichannel formats because of licensing, but its still an interesting thought exercise to image if those formats were open and what new speaker system topologies could arise by keeping everything in the digital realm until the last possible step.
 
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Shefffield

Shefffield

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Thanks, guys!

Correct, I want to use 'ring-machines' with FIR filtering. So the setup of the whole system is based around a PC host running a convolver software that splits the incoming stereo signal into individual channels for each driver. Currently I use a 3-way speaker, so the software puts out 6 channels (bass l+r, mid l+r and treble l+r) into an RME interface. The RME feeds three stereo amps, and each amp channel drives its own transducer.

The plan is to get rid of the RME Fireface and the amplifiers and integrate everything into a speaker that is only connected to the outside world via one or two digital lines. (Or by WiFi or bluetooth, if I dare to touch that can of worms some time in the future.) Plus 230 V supply, of course - but that can come from the nearest wall outlet.

Every single channel is supposed to contain the already filtered signal for its individual transducer. Low and or high pass, time and gain alignment and room correction included.

To make matters a little worse, a team of subwoofers is also on the list. And since I am leaning towards dipole subs, they would have to be placed somewhere in the middle of the room. That's why their connections are also not trivial. I wouldn't like an array of line level trip wires across my living room.

If you check what's available at, for example, audiophonics.fr, you'll see a vast choice of DAC and amp modules that should make this project possible without insane effort and investment.
 

voodooless

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If you want to go to more than 8 channels and have it distributed, then doing SPDIF over CAT would also not work very well anymore.

Networked audio would then be the best option. Something using AES67 would work. If you want to go cheap, have a Pi zero run G-streamer to receive an AES67 stream, and add a USB DAC or HAT to get the audio out. Then add an amp, and you should be good.
 

abdo123

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Using a PC to do crossovers is risky business.

you risk blowing a tweeter (or even damaging your hearing) if something crashes and random noise starts blasting through the speaker for god knows why.

At least with the plate amplifiers you have the option of selling a working product later or putting it to use somewhere else. With this sort of plan the speaker is obselate the moment something flashier catches your eyes.
 
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Shefffield

Shefffield

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AES67 over Gstreamer is fascinating stuff. I didn't know that Gstreamer can do that. Thank you for the hint!

I don't have the ambition to route everything over single cable. I'm perfectly fine with a ring type cabling starting at the convolved PC. Even multiple cables to each speaker can be acceptable, especially if we talk about thin (optical?) multi-channel lines.

Blown tweeters are a risk I'm well aware of. My RME UFX cost me a ribbon tweeter because of a misclick. But that can be solved with L-pads in the signal lines to the tweeter amps. (I've discussed this in another thread here in ASR.)

I have no intention of selling anything. This will be an audio system for me alone, and it's possible that it never leaves a prototype state.
 

somebodyelse

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If you want to go cheap, have a Pi zero run G-streamer to receive an AES67 stream, and add a USB DAC or HAT to get the audio out
Are you thinking of wifi, or using a USB dongle for wired ethernet? From what I've read PTP (as used for clock sync by AES67 among others) doesn't deal well with the variable delays with wifi, so wired is probably necessary for that. Gstreamer's old native network time sync handles wifi better, but I'm not sure if it's good enough to make wifi a viable option with a home brewed transport.
 

voodooless

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AES67 only works on wired networks
 

xplo5iv

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This probably a stupid suggestion, but can your software address multiple stereo usb sound cards, mapped in whatever way you choose?
If so each speaker could contain a USB hub and the required number of interfaces for the number of drivers.
 

DWPress

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The simplest way is with an 8 channel DAC like the Okto Pro but you can use far cheaper soundcards like Asus and Creative if SINAD not a huge concern. There are multiple ways to do the XO in software and there are threads here on ASR that explore these. Check out the link in my signature for one way. The X-MCFX convolver plugin takes a convolution file for each channel and combines them into one instance to be used in the signal chain.
 

somebodyelse

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This probably a stupid suggestion, but can your software address multiple stereo usb sound cards, mapped in whatever way you choose?
If so each speaker could contain a USB hub and the required number of interfaces for the number of drivers.
The problem with that is keeping the multiple cards in sync as they all have different clocks. Pro audio adapters often have master clock connections so that you can keep multiple adapters in sync, but you won't find them on many stereo devices.
 
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