Hi all,
This is actually a follow-up from an earlier thread I had started in this forum, about active XO designs. That discussion went into using digital active XO+eq like the Behringer or the Driverack, and taught me a lot. Can't thank all of you guys enough. (I guess you are getting tired of receiving all this adulation...
)
While absorbing and digesting all that, I strayed into other forums, and chanced upon discussions elsewhere where people were trying to build high-end CD players using $20 computer CD-ROM drives. Thorsten's evil twin was posting there, and many other very experienced people. The thread at some point fragmented into two, pursuing two different approaches to the same goal. Most interesting, both the threads. But that's where I learned about BruteFIR. And this brought me right back to active XO for speaker building.
BruteFIR allows me to use an ordinary Intel computer to do real-time digital filtering on digital audio data. This means that I should be able to take digital or analog inputs into my PC, use BruteFIR to create the equivalent of Driverack or Behringer units, and then pump the sound out through a decent multi-channel sound card (many pro audio cards have six to eight analog output channels).
Will this be a good idea? This sounds like a great way to do active filter prototyping, and then when the design is frozen for a particular box, you can build a hard-wired analog active XO+eq for the box using (low-tech, I know) NE5532 and passives, at very low cost. And then move ahead with your PC to the next speaker design project. To my newbie brain, this sounds like the ideal DIY speaker building tool, at low cost, with high flexibility, allowing oodles of tweaking, and building a sub-community of BruteFIR users exchanging tweaks in terms of config files.
Will this work? It's possible to build a PC with no fans for cooling... that's a known problem with known solutions. So adding the PC to the chain will not add ambient noise. And it's possible to eliminate drives from a PC, thus removing still more noise. You can build a PC which boots from a CD-ROM and works entirely out of ramdisk. Such a PC probably can be powered by a conventional transformer+bridge+filter caps combo instead of the noisy fan-cooled SMPS. (Just Google for "low noise PC" and "silent PC" for lots of links.) Also, the RFI in the PC should not affect the sound too much if you use good sound cards... most pro audio workstations are built around them nowadays, I'm told, even in recording studios. And the threads I mentioned earlier (CD-players using CD-ROM drives) are discussing such hardware already.
(All my software-related comments are related to Linux. I'm somewhat computer-challenged; I can't seem to get anything done easily with Microsoft operating systems, other than MS-DOS. My laptop runs Linux.)
Please, what do you guys think? My goal is to get active-XO speakers designed and built quickly without having to invest in a Behringer. Steve and others have already said in my earlier thread that it's quite easy to translate the settings of a Behringer/Driverack into an equivalent hard-wired analog circuit design. Such a circuit will be as complex as SL's eq circuit for his Phoenix or Orion, I guess.
Tarun
This is actually a follow-up from an earlier thread I had started in this forum, about active XO designs. That discussion went into using digital active XO+eq like the Behringer or the Driverack, and taught me a lot. Can't thank all of you guys enough. (I guess you are getting tired of receiving all this adulation...
)While absorbing and digesting all that, I strayed into other forums, and chanced upon discussions elsewhere where people were trying to build high-end CD players using $20 computer CD-ROM drives. Thorsten's evil twin was posting there, and many other very experienced people. The thread at some point fragmented into two, pursuing two different approaches to the same goal. Most interesting, both the threads. But that's where I learned about BruteFIR. And this brought me right back to active XO for speaker building.
BruteFIR allows me to use an ordinary Intel computer to do real-time digital filtering on digital audio data. This means that I should be able to take digital or analog inputs into my PC, use BruteFIR to create the equivalent of Driverack or Behringer units, and then pump the sound out through a decent multi-channel sound card (many pro audio cards have six to eight analog output channels).
Will this be a good idea? This sounds like a great way to do active filter prototyping, and then when the design is frozen for a particular box, you can build a hard-wired analog active XO+eq for the box using (low-tech, I know) NE5532 and passives, at very low cost. And then move ahead with your PC to the next speaker design project. To my newbie brain, this sounds like the ideal DIY speaker building tool, at low cost, with high flexibility, allowing oodles of tweaking, and building a sub-community of BruteFIR users exchanging tweaks in terms of config files.
Will this work? It's possible to build a PC with no fans for cooling... that's a known problem with known solutions. So adding the PC to the chain will not add ambient noise. And it's possible to eliminate drives from a PC, thus removing still more noise. You can build a PC which boots from a CD-ROM and works entirely out of ramdisk. Such a PC probably can be powered by a conventional transformer+bridge+filter caps combo instead of the noisy fan-cooled SMPS. (Just Google for "low noise PC" and "silent PC" for lots of links.) Also, the RFI in the PC should not affect the sound too much if you use good sound cards... most pro audio workstations are built around them nowadays, I'm told, even in recording studios. And the threads I mentioned earlier (CD-players using CD-ROM drives) are discussing such hardware already.
(All my software-related comments are related to Linux. I'm somewhat computer-challenged; I can't seem to get anything done easily with Microsoft operating systems, other than MS-DOS. My laptop runs Linux.)
Please, what do you guys think? My goal is to get active-XO speakers designed and built quickly without having to invest in a Behringer. Steve and others have already said in my earlier thread that it's quite easy to translate the settings of a Behringer/Driverack into an equivalent hard-wired analog circuit design. Such a circuit will be as complex as SL's eq circuit for his Phoenix or Orion, I guess.
Tarun
The answer is yes. I think more than one person here is working on similar project. I am using a strip down Window 98SE booted from a compact flash disk. I am still debating on the software. Most likely, WaveWarp from
http://www.soundslogical.com/
http://www.soundslogical.com/
Another thread, another approach
I've checked an earlier thread started by NappyLady, about using Creative Soundblaster Live with special device drivers for something like this. My asking this in a separate thread was with the hope that we could look at a solution which was independent of a particular sound card. That Soundblaster solution was tied to the device drivers of that card's DSP chip. I thought I'd just explain...
And if we can go open source with the software, and make it totally sound-card independent, then different members can actually try various different sound cards without affecting the (complex) software at all, and get solutions at different price points. Some of you can also make products out of such work and offer them for sale without software licence fees.
And Agent.5, thanks for the pointer. Will take a look at the software you've mentioned. How small is the practical lower limit of your flash RAM with your approach?
Tarun
I've checked an earlier thread started by NappyLady, about using Creative Soundblaster Live with special device drivers for something like this. My asking this in a separate thread was with the hope that we could look at a solution which was independent of a particular sound card. That Soundblaster solution was tied to the device drivers of that card's DSP chip. I thought I'd just explain...
And if we can go open source with the software, and make it totally sound-card independent, then different members can actually try various different sound cards without affecting the (complex) software at all, and get solutions at different price points. Some of you can also make products out of such work and offer them for sale without software licence fees.
And Agent.5, thanks for the pointer. Will take a look at the software you've mentioned. How small is the practical lower limit of your flash RAM with your approach?
Tarun
You may find this site interesting:
http://home.pacbell.net/donwm/
The only issue that might rear its head is if you incorporate room EQ into your analog units, then move the speakers or the lsitening position significantly. This will stuff up the EQ.
Cheers
Steve
http://home.pacbell.net/donwm/
The only issue that might rear its head is if you incorporate room EQ into your analog units, then move the speakers or the lsitening position significantly. This will stuff up the EQ.
Cheers
Steve
It's probably workable, but I think it would cost quite a bit more than a decent Behringer X/O anyway, so I'm not sure what the point is. I mean, a suitable sound card alone will probably run upwards of $150. And that's not even taking into account the cost of the PC (which will be pretty hefty if you want it to be silent, use a linear power supply, and be completely RFI-shielded) or the time involved in building a boot image for it.
Additionally, correct me if I'm wrong, but aren't crossover points properly determined mathematically anyway?
It's not a bad idea, but I don't think as a stand-alone device the price/performance ratio doesn't even come close to beating that of a traditional commercial or DIY X/O. Of course, as an addition to a home theater PC, I think it would certainly have some use.
Additionally, correct me if I'm wrong, but aren't crossover points properly determined mathematically anyway?
It's not a bad idea, but I don't think as a stand-alone device the price/performance ratio doesn't even come close to beating that of a traditional commercial or DIY X/O. Of course, as an addition to a home theater PC, I think it would certainly have some use.
sfdoddsy said:
Thanks, Steve. I checked that site quickly; it's very interesting. Have bookmarked it. And you're right about that room eq bit. Don't know how to get over it, unless I leave that PC+BruteFIR in circuit permanently.
One other problem that's coming up with my own idea as I write, is that I probably cannot get decent sound quality using separate inexpensive two-channel sound cards... I'll need one card to output at least six analog outputs. This is because I'll need all outputs to be clock-sync'd. If I want to do external clock-sync, then the sound cards will probably become more expensive than the Behringer. And multi-channel cards cost a fair packet... the Delta 1010 (the one in the site you referred me to) lists at $799, and will probably sell for $400-500. Once again, the Behringer is cheaper.
You're right about the sound cards, so I'm having doubts myself. But a PC can be quite inexpensive, specially if you take a PC motherboard which is a couple of years old. The other tweaks to make it quiet don't cost much money.r0cket- said:
I didn't understand this point. Can you explain?
I'm having doubts too... the sound card cost will be the determining factor, no doubt. I had been dreaming of using a set of three inexpensive stereo cards, but NappyLady's thread already talks of clock drift problems... Sigh.
Tarun
Well, my understanding of crossovers of any sort is that you determine the crossover points and slope and whatnot mathematically via the TS parameters of the drivers involved and the cabinet dimensions, etc. So I guess I just don't really understand why you would necessarily want an active X/O that allows you to "experiment," as you say, when the optimal values are easily determined on paper or via software simulation. An EQ, sure, but not an X/O.
The thing with the sound cards is that in order for any of it to be effective, you need something with 4 or 6 analog channels that each have perfectly flat frequency response from like 10Hz-40KHz. That's going to be very expensive.
The thing with the sound cards is that in order for any of it to be effective, you need something with 4 or 6 analog channels that each have perfectly flat frequency response from like 10Hz-40KHz. That's going to be very expensive.
Hi!
I AM already using my PC this way, however not with BruteFIR (which I am aware of), but with the also mentioned Emu10k1 combined with kxProject-drivers solution.
The big advantage is that the sound processing is done in the DSP that way, and not by the cpu. And since I use my media box not only for music, but also for movies and emulators, I need all the cpu power I can get (with high-res mpeg4 (DivX / XVid) movies and postprocessing in ffmpeg turned all the way up, the 1 Ghz Pentium III used in my box is at it's limits ).
I have to admit that i seem to lack the magic hearing abilities most board users here claim to have (but let's not start another discussion about that here), but for me I just don't hear anything distorted (shielding) out of my equipment. And for me it also makes no difference whether I hook up a cd player or my media box to my P3A (or GC) and End Millenium, both sounds well to me, with the exception of the cd player not having any active XO / EQ enabled...
And I just love the simplicity of virtually cabling your system with the kxProject. Simply add all effects you need to your DSP, then connect all input/output pins with virtual cables...
Under Linux you can do something similar with the arts-Builder, but I have to admit that I could not get arts do any good real-time-processing so far - and again, it is the cpu which is doing the computations, so the DSP is wasted on that setup, as well.
One good and cheap 7.1 soundcard is the MAudio Revolution, but I thing it's linux capabilities are very limited so far, and for Windows I don't like it since (so far) all drivers for all commercial soundcards restrict the user from freely accessing the DSP of the soundcards, thus preventing me to actively setup my system...
Just try it once (if you have a computer at hand) with an Creative Audigy 1 (Audigy 2 still isn't supported as well by kx) and kxProject, you can get the soundcard at ebay for sure!
Bye,
Arndt
I AM already using my PC this way, however not with BruteFIR (which I am aware of), but with the also mentioned Emu10k1 combined with kxProject-drivers solution.
The big advantage is that the sound processing is done in the DSP that way, and not by the cpu. And since I use my media box not only for music, but also for movies and emulators, I need all the cpu power I can get (with high-res mpeg4 (DivX / XVid) movies and postprocessing in ffmpeg turned all the way up, the 1 Ghz Pentium III used in my box is at it's limits
).I have to admit that i seem to lack the magic hearing abilities most board users here claim to have (but let's not start another discussion about that here), but for me I just don't hear anything distorted (shielding) out of my equipment. And for me it also makes no difference whether I hook up a cd player or my media box to my P3A (or GC) and End Millenium, both sounds well to me, with the exception of the cd player not having any active XO / EQ enabled...
And I just love the simplicity of virtually cabling your system with the kxProject. Simply add all effects you need to your DSP, then connect all input/output pins with virtual cables...
Under Linux you can do something similar with the arts-Builder, but I have to admit that I could not get arts do any good real-time-processing so far - and again, it is the cpu which is doing the computations, so the DSP is wasted on that setup, as well.
One good and cheap 7.1 soundcard is the MAudio Revolution, but I thing it's linux capabilities are very limited so far, and for Windows I don't like it since (so far) all drivers for all commercial soundcards restrict the user from freely accessing the DSP of the soundcards, thus preventing me to actively setup my system...
Just try it once (if you have a computer at hand) with an Creative Audigy 1 (Audigy 2 still isn't supported as well by kx) and kxProject, you can get the soundcard at ebay for sure!
Bye,
Arndt
Thanks for the KX Project idea. On the site, I found a link to this: modifying a common Audigy to get 3 s/pdif
http://www.electricstart.de/travelrec/kx/
This should save me the time and $ to get everything done using ADAT.
http://www.electricstart.de/travelrec/kx/
This should save me the time and $ to get everything done using ADAT.
It seems to me that the advantage of this idea is not so much in doing it cheaper than the Behringer, but that it could perhaps do a lot more, in either quantity of speakers controlled or the features. You would not be limited to features included in the unit you buy. I wonder if you had the ability, you could perhaps come up with a sophisticated setup with features that may otherwise involve buying many units.
Suppose you used it with a set up like this:
2 subs
5 or 6 home theatre speakers
eq to the subs
crossover for all speakers so all drivers actively driven
digital delay to time align all the drivers
I wonder if you could also use it to help correct problems with phase (I'm far from getting my brain around all the issues involved with time alignment and phase).
Suppose you used it with a set up like this:
2 subs
5 or 6 home theatre speakers
eq to the subs
crossover for all speakers so all drivers actively driven
digital delay to time align all the drivers
I wonder if you could also use it to help correct problems with phase (I'm far from getting my brain around all the issues involved with time alignment and phase).
Doing a lot more...
However, I was also interested in what you've mentioned... use a general-purpose expandable base, so that you can add channels, play with choice of sound cards, and exchange BruteFIR config files. That way, an entire new dimension of DIY tweaking will be possible. And BruteFIR being open source, people can actually tweak the algos or add new algos. This seems attractive, given the fact that many experienced designers have said that the totally configurable active xo + eq is the way to go for future speaker designs. So why not free up this critical component from the limits of one or two manufacturers' black boxes and move it to a PC?
However, I'm beginning to feel that costs may become a stumbling block... I don't know. Good 6-channel sound cards may become expensive, and if you want to do what you've described (active loudspeakers for each driver of each of six or eight speakers), then you'll need half a dozen sound cards and will have no option but to do external word-clocking, I guess.
So it appears to me that the only people who will like this approach will be ones who want to have more analog outs than one Behringer gives you today, or those who have unusual digital filtering requirements which are not supported by the Behringers/Driveracks of today.
All said and done, I can't help feeling that inexpensive PCs need to be used much more widely as the key storage and playback component for very high-end music systems. I'm not just talking about "PC as CD transport" here... I'm talking of using the CPU power of the PC for digital filtering. The fact that the music itself can come from a (low-noise) HDD is a bonus. Finally, PCs are very inexpensive, specially if you pick up two-year-old rejects. And Linux/FreeBSD with packages like BruteFIR are the way to go. It's the cost of good sound cards which discourages one.
Tarun
I originally started trying to see if I could use this approach to build an inexpensive but not well packaged system for prototyping a new speaker design. Once I get it right, I can transfer the xo and eq to a hard-wired analog circuit.paulspencer said:
However, I was also interested in what you've mentioned... use a general-purpose expandable base, so that you can add channels, play with choice of sound cards, and exchange BruteFIR config files. That way, an entire new dimension of DIY tweaking will be possible. And BruteFIR being open source, people can actually tweak the algos or add new algos. This seems attractive, given the fact that many experienced designers have said that the totally configurable active xo + eq is the way to go for future speaker designs. So why not free up this critical component from the limits of one or two manufacturers' black boxes and move it to a PC?
However, I'm beginning to feel that costs may become a stumbling block... I don't know. Good 6-channel sound cards may become expensive, and if you want to do what you've described (active loudspeakers for each driver of each of six or eight speakers), then you'll need half a dozen sound cards and will have no option but to do external word-clocking, I guess.
So it appears to me that the only people who will like this approach will be ones who want to have more analog outs than one Behringer gives you today, or those who have unusual digital filtering requirements which are not supported by the Behringers/Driveracks of today.
All said and done, I can't help feeling that inexpensive PCs need to be used much more widely as the key storage and playback component for very high-end music systems. I'm not just talking about "PC as CD transport" here... I'm talking of using the CPU power of the PC for digital filtering. The fact that the music itself can come from a (low-noise) HDD is a bonus. Finally, PCs are very inexpensive, specially if you pick up two-year-old rejects. And Linux/FreeBSD with packages like BruteFIR are the way to go. It's the cost of good sound cards which discourages one.
Tarun
Why tweak the crossover points?
And somehow, doing all this experimentation using either an active line-level xo or a passive xo seems like a big pain.
Only digital seems attractive.
Tarun
From what I hear from designers much more experienced than me, it appears that you cannot decide the final crossover frequencies or slopes till you actually listen to the final products. It appears that xo fine-tuning requires literally months of listening sessions in one's spare time. Case in point: the story of the design of the Ariel xo. More recently, someone on one of the threads of this forum said that he loves the Peerless 146 10" woofer, but he had to shift the xo point from 300Hz to 150Hz because he was getting too much distortion at 300Hz. Frankly, I don't know much about all this; I'm just telling you what I've read.r0cket- said:
And somehow, doing all this experimentation using either an active line-level xo or a passive xo seems like a big pain.
Only digital seems attractive.Tarun
I can't see myself getting into messing with computers that much in the way you have described, and I'm not into programming, so I'm not likely to do this (although maybe at some time I might be able to find someone up to the challenge!!!) ... so that side of things is over my head ...
but I did have an idea how to make it cheap ... you mentioned 2 problems:
1. cost of a quiet running pc
2. cost of good sound cards
1. use an old pc that you want to upgrade but you won't get any money for - that is free. Put it in another room so you won't hear the fan.
2. use a low cost sound card and replace the preamp part of it - that is the part that controls sound quality, right? ... get a kit and build your own for next to nothing, something like you can find on Elliott Sound Products
If you have the ability to take care of all the programming and computer stuff, then wouldn't it be quite cheap doing it that way?
but I did have an idea how to make it cheap ... you mentioned 2 problems:
1. cost of a quiet running pc
2. cost of good sound cards
1. use an old pc that you want to upgrade but you won't get any money for - that is free. Put it in another room so you won't hear the fan.
2. use a low cost sound card and replace the preamp part of it - that is the part that controls sound quality, right? ... get a kit and build your own for next to nothing, something like you can find on Elliott Sound Products
If you have the ability to take care of all the programming and computer stuff, then wouldn't it be quite cheap doing it that way?
It's a nice theory but there are practical problems. I use an active 3 way digital xover and EQ for my main speakers.
That means I feed two channels in, and get six out, with EQ on each output.
Are there soundcards that will let you do this?
Assuming yes (if so), then we add the center and surrounds. You will then need a card that allows you to have 2-5 channels in, and 15 out.
I'm sure one day you'll be able to do it, but for less than a dedicated box...?
I'm not so sure about that.
Two Behringer DCX will do it now (almost) for $700.
Cheers
Steve
That means I feed two channels in, and get six out, with EQ on each output.
Are there soundcards that will let you do this?
Assuming yes (if so), then we add the center and surrounds. You will then need a card that allows you to have 2-5 channels in, and 15 out.
I'm sure one day you'll be able to do it, but for less than a dedicated box...?
I'm not so sure about that.
Two Behringer DCX will do it now (almost) for $700.
Cheers
Steve
Havent' checked in for a while - time for me to chime in.
I'm actually using BruteFIR in my system, with a Delta 1010 sound card. It is IMHO the 'right' way to handle a primarily digital system, but that doesn't mean that it doesn't have problems/inconveniences.
First, why this rather than a Behringer etc. The main answers
1)flexibility in your filter topology (FIR or mixed vs IIR only)
2)"unlimited" expansion (within reason. Anders Torger who wrote BruteFIR is running something like 26 channels in his ambisonics rig, using RME cards and ADAT converters)
3) time-domain room correction. The DRC software package is the real deal in terms of bass correction.
4) multiple/switchable filter topologies. This might be more of a theoretical consideration, but the ideal filter for music might not be the same as for theater. eg linear phase w/ aggressive room correction for music where there is only one listener in the 'sweet spot' vs LR4 and more moderate correction for HT.
5) Quality (at a cost). Even a Delta 1010 should perform rather better in terms of analog output than a Behringer, and RME is reported to be even better. If you have mega-bucks, pro/studio grade ADAT rigs from Apogee etc can be used which will be truly state of the art. Since most of the higher end cards typically have a stereo spdif feed, you can also use your favorite DAC for your 'most important' channels.
the main problems with this approach center on convenience. Basically:
1) you need good measurements, particularly if you do room eq
2) *high quality* volume control is not easy, and it's important to keep your soundcard as close to max output as possible to maximize use of the wordlength.
3) home theater input. given the relative lack of multichannel decoders for linux (no DTS, no DPLII, no DTS NEO/Logic 7 etc) you will probably have to run your 5.1 etc signals in through an A/D stage
I don't see cost as being that big a big deal. An m-audio revolution 7.1 runs $100, and has analog performance WAY more than good enough to allow you to get a very good system up and running. In other words - it'll take you a while before the overall quality of your filters/xovers makes the Revo the limiting factor. When that happens, you will probably be more than happy to spend the $$$ for a top-end card.
I'm actually using BruteFIR in my system, with a Delta 1010 sound card. It is IMHO the 'right' way to handle a primarily digital system, but that doesn't mean that it doesn't have problems/inconveniences.
First, why this rather than a Behringer etc. The main answers
1)flexibility in your filter topology (FIR or mixed vs IIR only)
2)"unlimited" expansion (within reason. Anders Torger who wrote BruteFIR is running something like 26 channels in his ambisonics rig, using RME cards and ADAT converters)
3) time-domain room correction. The DRC software package is the real deal in terms of bass correction.
4) multiple/switchable filter topologies. This might be more of a theoretical consideration, but the ideal filter for music might not be the same as for theater. eg linear phase w/ aggressive room correction for music where there is only one listener in the 'sweet spot' vs LR4 and more moderate correction for HT.
5) Quality (at a cost). Even a Delta 1010 should perform rather better in terms of analog output than a Behringer, and RME is reported to be even better. If you have mega-bucks, pro/studio grade ADAT rigs from Apogee etc can be used which will be truly state of the art. Since most of the higher end cards typically have a stereo spdif feed, you can also use your favorite DAC for your 'most important' channels.
the main problems with this approach center on convenience. Basically:
1) you need good measurements, particularly if you do room eq
2) *high quality* volume control is not easy, and it's important to keep your soundcard as close to max output as possible to maximize use of the wordlength.
3) home theater input. given the relative lack of multichannel decoders for linux (no DTS, no DPLII, no DTS NEO/Logic 7 etc) you will probably have to run your 5.1 etc signals in through an A/D stage
I don't see cost as being that big a big deal. An m-audio revolution 7.1 runs $100, and has analog performance WAY more than good enough to allow you to get a very good system up and running. In other words - it'll take you a while before the overall quality of your filters/xovers makes the Revo the limiting factor. When that happens, you will probably be more than happy to spend the $$$ for a top-end card.
Soundcards as digital filters
Hi
The possibility of using a computer soundcard as a digital crossover is incredible and opens up many new possibilities. The problem is just as a non technical guy how do start to convert my Creative Soundcard to a active crossover and how do you set the crossover frequencies ?
Jozua
Hi
The possibility of using a computer soundcard as a digital crossover is incredible and opens up many new possibilities. The problem is just as a non technical guy how do start to convert my Creative Soundcard to a active crossover and how do you set the crossover frequencies ?
Jozua
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