digital crossover w/digital output?

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I had this idea of using an external digital crossover to bi-amp speakers. This way, there would be no need for building crossovers into the speaker, and crossover settings could be readily changed to my own preferences. There are crossovers that have digital input (Behringer DCX2496), but no digital output. I would want to use a separate DAC (for example, Lavry Blue). To do this, I need a crossover that has digital inputs and digital outputs. I thought for sure there must be something like this out there, but alas, I'm posting here, so you can guess that I haven't found it yet. Is it me, or doesn't it seem like this kind of equipment should be out there?
 
Yes, I have, but actually I want to connect the digital output from my SqueezeBox to the crossover, not directly from the computer. Perhaps, I could build a very cheap "black box" with a CPU, Linux, soundcard with digital inputs/outputs, and DSP software to do the job. This is essentially what I was hoping I could find already out there. The other thing is how many soundcards have multiple S/PDIF outputs (for either a 2-way or 3-way xover)?
 
I have been looking at the DEQX myself, it seems that the most common version has single ended analogue outputs, but XLR analogue and AES / EBU options are listed on their website.

Don't know about availability though, maybe those options are available only on special order. It might be best to check with them.
 
I wouldn't need volume control, because the SqueezeBox already has volume control. Essentially, I just wanted to know if it is possible to separate the source signal digitally into different components. If I had all the money in the world, I would have a system like this:

SqueezeBox->DEQX->Lavry Blue (4-channel)->bi-amplification->DIY crossoverless speakers

It seems like this would be the most modular system possible, and could give essentially unlimited control over every aspect of the chain. Like I said, if I had all the money in the world...
 
I have been thinking about exactly the same - how to make XR-55 accept multichannel PCM digital input composed of signal for individual drivers. Maybe it would be a simple modification of Panny circuits. Another option is the coming XR57 that has HDMI but here I am not sure if the current PC soundcards (or graphics cards) can generate HDMI audio.
 
cph2000 said:
LineSource: how would you go about getting a multi channel digital signal from the PC to the xr55 ?

Search through the archives here - there are a couple folks that have done it to various models. The Equibit chips take I2S, and so by tapping into the right spots on the circuit board, you can feed multiple channels in digitally. The XR-10 is actually the easiest, but only has 5 amp channels. The newer amps that I've seen (I have XR25's and an XR55) have more convoluted/integrated boards, and I haven't traced the circuits - I suspect you might need the service manual.
The Delta 1010 card has I2S signals on the db-25 breakout to the external box, so I would assume it would be somewhat straightforward to adapt this to a modified Panasonic.

Panasonic does use HDMI to carry DVD-A signals, so in principle it should be useable for an xover. However, I am pretty certain there is no way to output such a signal from a PC at this point.

As for the original poster, the DEQX is the only xover I'm aware of with digital outputs. There might be a pro unit out there, but I'm not sure. The 'standard' approach to look at if you're using a PC is the Lynx AES-16 which has 8 stereo AES/EBU outputs; it's electrical only though, so you'd need a format converter for the Squeezebox optical output.. A cheaper approach if you're happy with 48kHz max is to use an Alesis AI4 with ADAT - this gives 4 stereo spdif outputs from an 8-channel adat stream. Any pro card should be able to send ADAT, although you might run into problems trying to mix optical spdif in with optical ADAT out.
Middle ground is what I'm doing - I have an Emu 1820M which has two digital outputs plus 8 analog outputs. I send the two digital outs to panny receivers, and run the analog out to a separate amp. I'm still in prototype mode, so I'm not sure whether I'll be driving the woofers or the tweeters with the analog amp - depends on several factors. Multiple Panny receivers actually works fine for this, as they will all respond in unison to a single remote for volume etc. You could also run one digitally for the midrange and run a second in 4-channel analog mode for bass/tweet without giving up too much quality IMHO.
 
Windows PC with RME HDSP9652

I'm having reasonable success with this setup

Sony CD JukeBox or PC out to
input #1 of RME HDSP9652 in to
Console (a windows VST plugin host from Japan for about $50)
Voxengo GlissEQ 24db/oct Butterworth IIR filter ($99) out the
RME HDSP 9652 ADAT output #2 (8channels) into
Alesis AI4 ADAT Breakout box ($400) to AES/EBU breakout box into
multiple Benchmark Media DAC1 or Panasonic XA-SR70's (this is where the volume control is currently, although I can do 10db on the PC side)
into 4 speakers per side

20-80 hz 10" Dayton sub
80-900 hz Scanspeak 21w/8554 tobe replaced with Seas Excel
900-10khz Bohelender Graebner RD40 quasi-ribbon
10khz - 20khz to be determined, currently BG Neo3PDR ribbon

The latency is about 250 millseconds with an AMD Athlon64 3500. I dont bother pushing the latency lower, but I give up audio/video synch with movies, so this is a stereo only system.

I wish the 24db/oct Butterworth's could do 24db/oct Linkwitz Riley. This is slightly better sounding that my previous Behringer DCX2496 system.
 
I'm having reasonable success with this setup

Pretty nice setup- much like what I was trying to do before I got relegated to rooms too small for full-range dipoles. I have the 60" Carvers rather then the BG's though.

I think you're the first person I've seen actually using an AI-4 - does it work as expected?

I wish the 24db/oct Butterworth's could do 24db/oct Linkwitz Riley. This is slightly better sounding that my previous Behringer DCX2496 system.

First, check out Jans stuff at www.thuneau.com . Full xover package in a single VST plugin, including adjustable Q xover stages and several parametric sections per band. Should work in Console. Still in beta (I'm testing it), but it should be GA relatively soon. He hasn't set pricing but the hints seem to be that it'll be pretty reasonable.

Second, are you being sarcastic, or is it only 'slightly' better sounding? I have a DCX as well, and while I've never had 'the same' system setup both ways with identical filters etc, my impression is that the PC system with the Emu is a big step up from the DCX.
 
dwk123,

Alesis AI-4: I am running about 60 feet of toslink from PC out to the living room. The toslink is supposedly the highest quality plastic fiber out there. I was worried that I'd hear noticeable prolems running that distance, but it sounds fine even through Sennheiser HD650's and an M3 headphone amp. One problem with using the PC as crossover is finding a sound card that can output 4/6/8 channels and keep them in synch. This isnt a problem with analog cards and maybe it would have been wiser to just use an analog out RME or Lynx card. The reason I went with RME was in case I switched from Windows to Linux Brutefir.
Having a single toslink cable made for a neater install than many XLR balanced cables I think.

Why not just have the music PC sit in the living room? I have yet to build a PC that is quiet enough for my tastes. Much easier to remote the noisy high performance PC in another room.

Another alternative to getting multi-channels over to the PC is to use a realtime DTS encoding capable sound card. This would be a CHEAP way to get the signals over to the PC -- maybe $100 or less. And then you could use a single 5.1 channel receiver and solve the volume control problem all at once.

I chose this route thinking that the sound quality would be better if I could swap DAC's in at will.

The stuff on www.thuneau.com looks promising. I believe the Voxengo IIR plugins sound very, very good. The FIR Voxengo EQ sounded "digital".

I am thinking of doing my own VST crossover plugin or using a sound library called "FMOD-EX" to write my own combination music player/crossover. I am commited to only using ASIO sound on the windows platform. The reading I've done seems to indicate that any sound that goes through the Windows Mixer isnt bit-perfect anymore.

DCX2496 vs. PC: Here's the four stages of my systems evolution....

1) PC to DCX2496. My DCX2496 was modded to have volume control and uses OPA2604 opamps
2) PC to AI4 to three Panasonic SA-XR70 receivers. Volume control using remote and with the volume of the 3 receivers generally tracking each other. Tweeter padding achieved through just setting the "starting" point volume to a certain known offset.

This has got to be the best bang for the buck especially if I had used a DTS encoding sound card.

3) PC to AI4 to Benchmark Media DAC's to Aleph30/Threshold T200 amps

Ok, at this point I've just added $2K in DAC and much better amps to the equipment budget. Not a fair comparison to the DCX2496 which cost $300 with the volume mod costing me another $300. ( Didnt do that one myself)

Without additional ears it's hard to avoid "proud papa" syndrome. But I think each change was an improvement. The DCX2496 operated as a DAC(no EQ or crossover functions enabled) with those opamps was inferior to an MAudio SuperDAC. And blown away by the Benchmark Media DAC1. So yes the DCX2496 is wasted on by the PC setup. BUT the DCX2496 does many different filter types, is dirt-cheap, is quiet, and probably much lower latency.

The problem I run into with the PC as crossover is that EQ is very difficult to do without running into digital clipping problems. If all you are doing is crossover functions, that works great. But take a modern compressed CD that is average -3db and try EQ'ing out a dip in response and you'll end up clipping the signal worse than it already has been. This doesnt sound good. So while the PC saved me countless dollars not trying to "tweak" the latest overpriced poly-cap and inductor it has limitations. You can cut frequencies, just not boost them. Strangely the DCX2496 never told me it was digitally clipping, but it HAD TO BE. I was boosting 6db in places and cutting 6db in other places.

My feeling is that if the DCX2496 offered digital outs I wouldnt have bothered with the PC at all. I hope the hardware DSP manufacturers(DBX/Behringer) are listening... we want digital OUTS!!!

So the money I spent to get to this point has got me down. But yes, it sounds good. Still it's maybe 80-90% as good as a commercial B&W 800 series speaker with it's simple analog filter. Proving that digital can buy you alot of ground, but it's no substitute for measurement tools and filter design experience.
 
dwk123 - thanks for your info.

dwk123 said:

Search through the archives here - there are a couple folks that have done it to various models.

I have - you seem to have been one of the most involved in the discussions - can you remember someone who has made it for XR55 that I have ?

dwk123 said:


The Equibit chips take I2S, and so by tapping into the right spots on the circuit board, you can feed multiple channels in digitally.

Yeah, I think I have identified the relevant paths on my Delta 410 card. But I would not like to do any transmitters and receivers like Brian Brown proposed. I2S can be sent over small distances so I would just like to do a direct connection. But I am not sure about the details - for instance - if I identify the right place in Panasonic can you safely link the I2S from the soundcard or it requires some changes to the existing connections so that they are not damaged. What about the ground - where and how to handle it ? Are there no differences in I2S formats between the 410 soundcard and Panasonic ?
But the idea is exciting, I am looking forward to making it real.
 
You should also have a look at XTA, based in the UK. They are the standard for digital speaker management in the pro/broadway theater sound world. Any of thier current models have aes in/out support. Thier control software, Audiocore, is also very cool. They are a bit pricey, but way better than the behringer units. (nothing against them guys)
 
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