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Re: Foo_Xover plugin answers. All of them. At once. (Long)

Posted by Presto (A) on January 12, 2007 at 12:39:41

In Reply to: Foo_Xover plugin questions. posted by Frank25 on January 12, 2007 at 08:44:15:

Hey Frank:

I spend quite a bit of time doing different active setups using three different DSP based crossovers for Foobar. One also works in Winamp.

1. Do you have to use a 7.1 surround sound card?? Or can a card like the M-audio Delta66 series work, it has 6 analog outputs.

With the foobar kernel streaming output plugin, you can use practically any 4, 6 or 8 channel soundcard - I've even made 8 channel onboard sound codecs work. (Of course, 4 gets you two way, 6 gets you three way and 8 gets you four way). You don't *need* an 8 channel souncard if you are only doing a 2 way for example, in which case a 4 channel card would work fine - and only four out of 8 crossover "poles" would be in use.

Just remember that only kernel streaming or ASIO will get you past the Windows Kmixer and provide for non-resampled bit-perfect playback. Foobar can play back 32/192 files if set up properly, whereas Winamp is only good up to 24/96. Be aware that for either program, your plugins (crossover included) will likely be the limiting factor in sample rate and bitdepth

2. If it doesnt have to be a 7.1 card, can a card with multiple digital outputs work?? For example if the soundcard has 3 seperate digital outs, could you use a seperate dac for the lows, mids and highs?

The best solution for digital is the AES16 (as Dawnrazor said) or perhaps a simlilar RME card that has multiple digital outputs. Beware of the prosumer cards with multiple optical outputs. Sometimes they are SPDIF in, SPDIF out, ADAT, and other functions and are NOT outputs for each set of stereo channel pairs. Three way digital out is a good way to go... but spending all that money and still using SPDIF/AES? I'd say you'd be better off getting the Lynx 2B and using it's analog outs. Going with a Lynx AES16 and three DACS is going to cost a lot - and to get better DACS than those in the Lynx2B you're looking at about $1000 per DAC at least. This would mean $3K to $6K in dacs and you have not even bought three stereo pre-amps yet! Digital might be marginally better, but its going to cost 3 times as much when bi/tri-amping using the Lynx 2B.

3. Is the Xover ASIO compatible?

All DSP plugins are inherently ASIO compatible because they have not much to do with the final output. Only output plugins need to be ASIO compliant if you want to use an ASIO compliant soundcard. There are good ASIO output plugins available for both Foobar AND Winamp from our friends at www.otachan.com.

4. How is the sound quality of the Xover plugin? Does it degrade the sound or is it transparent?

4a) Xover is very sonically transparent. I'd say it's almost as transparent as the Thuneau Allocator - and it only fails in comparison because as nice as it is it's still rather limited in it's functionality. You can only select "textbook" filters (Butterworth, Bessel and Chebyshev) which are "fixed Q" filters. No Linkwitz/Riley is a total bummer as well - since LR2 and LR4 are extremely popular. Delay control is awesome with this plugin, and so is channel mapping - but channel mapping is not always intuitive - ALWAYS test tweeter output using a midrange first. Be aware that XOVER is designed to work with 44.1 kilohertz sample rate. If you play back 48, 88.2, 96, or 192 material, your crossover frequencies are going to shift upward according to the sample rate ratio. Not good, but you won't blow a tweeter either. You *could* theoretically create a special settings file for each sample rate... but this is a rather convoluted approach if you ask me. Maybe creator Francois Bourdon will implement multiple sample rate support one day - maybe he won't. He's basically giving us access to HIS project for FREE so who knows where he will go with it.

4b) The Aedio Japan FIR based crossovers are totally different animals. They come in up to four-way, but use FIR crossover filters with adjustable filter and delay "taps". These are linear phase crossovers and thus transient perfect, but there is no "phase correction" for the loudspeakers themselves, so although the filters themselves are transient perfect, the system will most likely not be. On the standard version, you must select one crossover slope setting (40 to 400db/ocatve) [!] which will automatically use the right tap for each filter based on crossover points. There is another version I have which is slightly different - you can enter custome filter taps for each filter, but one disadvantage: for the midband you can only select ONE tap for both highpass and lo-pass. This is a dead end if you are trying to do a "real serious" FIR crossover setup that would require separate lowpass and highpass tap values. The Aedio crossovers are not sample rate dependent however, which is a nice touch. Steep slopes like this are the cats meow for getting ribbon tweeters down as low as they will go as well. Shallow slopes + ribbow tweeters = bad news.

Also, although linear phase filters are by themselves transient perfect, some claim the "pre-ringing" associated with FIR filters is audible. Others claim it's not audible. And I definately don't want to debate that here. That's a topic for Propeller Head Plaza!! :P

4c) The Thuneau Allocator is by far the best DSP based crossover plugin available. It's not free... but it's a far more comprehensive crossover AND it can be ordered with a phase correction section that compensates not only for filter and driver phase shifts, but phase shifts associated with low frequency enclosure alignments. It's a VST plugin and comes with it's own VST host, but will work will other VST hosts as well. The Arbitrator works with free 2-channel VST hosts for Winamp, but 2in/8-out VST hosts for Winamp are only on the breadboard at this time - so you need to use ASIO output plugins to use the Allocator. Using multile bi-quad filters with FULLY adjustable Q, you can tune filters to have any Q value (and also create the standard Linkwitz/Riley, Butterworth, Chebychev and Bessel filters if you desire). Channel delays are a snap. The trick with the Allocator is that you NEED an ASIO based card. Also, if you are using a media player and not an external sound source, you *may* need to use two output channels to stream the player output (using an ASIO output plugin) onto the ASIO bus, and use the remaining crossover channels as filtered outputs. This way, an 8 channel card (4 stereo pairs) is only good for THREE way operation (6 stereo pairs). The Thuneau Allocator and Arbitrator work with both Foobar AND Winamp, provided you use the right output plugin(s) and have the right sound card(s). This is the case with the Creative X-Fi that I just got working with the Allocator this week. Sound? For $99 it can't be beat. But the analog outputs of the X-fi pale in comparison to the $999 Lynx 2B - as you would expect for 1/10th the price. But for 1/10 the price they don't sound 10 times as bad by any means! (Only maybe half as bad... wink wink). The Xfi is really only good for it's bitperfect and ASIO compliant spdif output, which is truthfully why I bought it. The analog outputs are "not bad" though, and definately beat my M-Audio Revolution 7.1 for high end detail, sizzle and shimmer. I think the M-Audio has a somewhat fuller bass though. PCI card analogue outputs on inexpensive cards just don't cut it truthfully.

The Allocator is not sample rate dependent - it will output the same sample rate as what is put in. It's output, however, is always 24 bit regardless of input bitdepth. The Allocator *for sure* uses 64-bit processing, where I am not sure what the XOVER and Aedio crossovers are doing (likely 32 bit?). This could also be why the Allocator sounds better to my ears. IIR filters are known to have no "pre-ringing" like FIR filters, are moreso approximate real-world passive filters, but also suffer from the same phase response of these filters... until now. The Arbitrator gives you the transient perfect nature of FIR filters, but uses IIR filters with no "pre-ringing". Brilliant actually.

My advice?

Go with the Lynx 2B with the Thuneau Allocator and Phase Arbitrator.

It's PROVEN to work with the Thuneau products, and is probably the best sounding PCI soundcard out there. It's expensive, but not as expensive as buying MID-FI CARD after MID-FI CARD (like I have) to find out that they all basically sound mediocre to good at best. With the Lynx 2B, if you DON'T like the sound, at least you can sell it (as it should hold a fair bit of value) and NEVER look back at PCI solutions - since there is likely nothing better out there in the PCI arena.

USB solutions are the talk of the town in the PC Audio Forum these days, and some folks have built some real dandies - but you would need three of the darned things to tri-amp, and there are no reports out as of yet that confirm whether or not you can use multiple instances of the same USB sound device and manage to map the crossover channels (low/mid/hi etc.) sucessfully.

There you go. Everything (and more) that you ever wanted to know about DSP crossover plugins. Hope this helped. Lucnh time is over and now I gotta do some *real* work really fast...

Thanks again to Francois Bourdon (Xover), the folks at Aedio Japan (Foobar FIR crossovers), the Otachan folks (Foobar and Winamp ASIO output Plugins), Jan at Thuneau (TOP product support - thanks Jan), Chun Yu for the original Winamp kernel streaming output plugin and Steve Monks for improving it. But most of all - the creators of Winamp and Foobar - for making this whole PC playback (with or without DSP crossovers) a possibility for all of us in the FIRST PLACE! :o)

Cheers,
Presto

Now here's where to get all the goodies!!

Foobar/Winamp/External Source IIR crossover with Phase Correction:
www.thuneau.com

Foobar FIR crossovers:
http://www.aedio.co.jp/download/

Foobar X-over (you have this already)
http://xover.sourceforge.net/

Foobar ASIO Output Plugins:

foo_output_asio(dll).dll (dll version) Ver. 0.51 (2006/2/25)
http://otachan.com/foo_output_asio(dll)_051.7z

foo_output_asio(exe).dll (exe version) Ver. 0.54 (2006/2/25)
http://otachan.com/foo_output_asio(exe)_054.7z

*************************************************************

Winamp Kernel Streaming Output Plugins:
http://www.stevemonks.com/ksplugin/

Winamp Otachan ASIO output plugin (dll)
http://otachan.com/out_asio(dll)_067.7z

Winamp Otachan ASIO output plugin (exe)
http://otachan.com/out_asio(exe)_070.7z

Have Fun! :o)

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Schiit Audio

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