Topic: Digital Room Correction: Convolver filter? (Read 7047 times)

Zoner · « **on:** August 28, 2003, 05:55:44 am »

Today on the AVS Forum, I came across this amazing thread, about digital room correction:

http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=283878&perpage=20&pagenumber=5

It's a really long thread, all about this guy's attempt to use a freeware program to implement 2-channel digital room correction with his HTPC. After a lot of messing around, it was a spectacular success.

The freeware program he uses records signals in order to generate a file that can then be used by something called a "convolver filter" to implement the correction. I don't even know what a convolver filter is, but now I want one.

So - my question: is there a convolver filter available for MJ9?

crowfan · « **Reply #1 on:** August 28, 2003, 06:00:47 am »

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I don't even know what a convolver filter is, but now I want one.

A true technophile

Just like me

TimB · « **Reply #2 on:** August 28, 2003, 06:01:39 am »

LOLOL

PhatPhreddy · « **Reply #3 on:** August 28, 2003, 06:26:02 am »

The thread referenced is a very exciting field in PC audio... DRC and also to a lesser extend digital speaker correction is very expensive in standalone units (TACT etc) but proponents swear by it...

Being able to implement room correction in the PC really brings PC audio to the next level...

JimH · « **Reply #4 on:** August 28, 2003, 07:14:55 am »

Here's what I said in another similar thread that is now locked:

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I took a look at the thread on AVS and, if what you need is DirectX support, try MC 9.1 (9.0 might work, too) and our DirectX Host plug-in from this page:

http://www.musicex.com/cgi-bin/downloads/mcplugins.pl?type=5&start=0 &end=10&page=1

Please let us know what you find.

Tangoman · « **Reply #5 on:** August 28, 2003, 09:19:51 am »

Hi Zoner,
Acoustic Mirror is a type of Convolving programme which will work in MC with the DX plugin installed. It is made by Sonic Foundry http://www.sonicfoundry.com

Also available at http://www.knufinke.de/sir is a free ware VST programme which convolves. This one would be more tricky as you need to use a VST to DX wrapper to make it work in MC available here
http://www.spinaudio.co To make all this stuff work you need a decent sound card and speakers to make the signal your are going to use for the DRC. I use to be more into this stuff but now I am a little fussy. I had the good fortune to be able to listen to music on a system with a THX wall and about 2000 watts of audio power.
Have fun
Cheers Gerry

loraan · « **Reply #6 on:** August 28, 2003, 10:11:29 am »

I tried to download the DX Host plug-in and got the error, "Invalid plugin file, cannot continue". Suggestions?

Media Center Registered 9.1.224

Joshua

(BTW--thanks for pointing out that this was on the plug-ins page. I've been wanting this since I first heard about it, but it was taken out of the MC 9.1 install and I haven't been able to figure out how to get it since).

loraan · « **Reply #7 on:** August 28, 2003, 10:49:42 am »

Well, I tried saving the mjp file to my desktop and running it from there and it seems to be working, so it might have been a problem on my end (with my browser or something...).

MachineHead · « **Reply #8 on:** August 28, 2003, 03:41:40 pm »

More info on a convolver plugin (and it's free):

HERE.

Flobalob · « **Reply #9 on:** August 28, 2003, 04:57:24 pm »

I have the Tact RCS 2.0S and I can tell you the results can be stunning when set up properly.
One problem I foresee doing it on PC is how can you accurately measure your room in the first place as there is no such thing as a microphone with a linear frequency response (or even a known response).
The Tact comes with its own mic and a unique calibration file.

PS - I drive an '82 Toyota. I just have weird priorities :-)

PhatPhreddy · « **Reply #10 on:** August 28, 2003, 07:33:57 pm »

If you check the AVS thread they seem to have settled on a suitable Mic and Mic preamp...

If no mic exists to do the job... What is the Tact using ?

Flobalob · « **Reply #11 on:** August 28, 2003, 07:54:48 pm »

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If no mic exists to do the job... What is the Tact using

No, no, no, silly, of course ANY microphone (with full range response) will work. But you have to know the exact characteristics of the microphone and the only way you can do this is by having an anechoic chamber at your disposal and some very expensive instrumentation!

Mastiff · « **Reply #12 on:** August 31, 2003, 04:14:43 am »

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More info on a convolver plugin (and it's free):

HERE.

This stuff is getting scarily advanced! Is it possible to use this on MC9, or only on foobar? I just can't change my very well functioning whole house audio system (haven't had a glitch since April or May, I think) that drastically, so to run another player is not an option. And how would this react to multi-zone sound? Will I get the convolve effect on everything, or just on the zone I assign it to? And why did kamikaze pilots wear helmets? I'm sooooo confused! ?

MachineHead · « **Reply #13 on:** August 31, 2003, 05:33:32 am »

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This stuff is getting scarily advanced! Is it possible to use this on MC9, or only on foobar?

At this time only foobar. But...there is the possibility of a port to MC. Shorten plugin was ported to MC from foobar. I don't see why this one couldn't be either.

Best bet would be to contact Garf over there and grovel like a peasant.

He may be willing, but I won't stake the farm on that.

Zoner · « **Reply #14 on:** September 02, 2003, 08:39:57 am »

Can someone post the exact link for "Acoustic Mirror"? I couldn't find it in Sonic Foundry's product list. Or is it bundled with another product?

Has anyone gotten this plug-in to work with MC?

escaflo · « **Reply #15 on:** September 02, 2003, 09:07:35 am »

It comes with Sonic Foundry Sound Forge as a plugin. To get it, you must install Sound Forge 6.

I have tried to use it, but I have no idea how it is suppose to work.

Bartabedian · « **Reply #16 on:** September 02, 2003, 09:50:11 am »

Acoustic Mirror is really an advanced room simulator, used mostly for recreating a space for FX purposes (very handy in post-production where ambience needs to added back into a visual scene).

There might be a convovler in Acoustic Mirror, but I've never used it for that function. I think what Tangodude may have meant was Acoustic X:

http://www.pilchner-schoustal.com/old/acoustic-x/software.htm

Tangoman · « **Reply #17 on:** September 02, 2003, 12:15:12 pm »

Hi Warrenpeace,
I actually meant Acoustic Mirror but as pointed out it does not seem to be sold stand alone any more. I think it could be used to DFC a room your right though it's main purpose is recreating different sounding envoirments in Post Production.
Cheers Tangodude

kiwi · « **Reply #18 on:** September 03, 2003, 04:51:39 pm »

What I would be really interested in, is the ability to use my computer as a digital crossover, to biamp my speakers.

Is there any way to get MC to do this? I guess that the problem is increasing the number of outputs, from 2 (stereo) to 2 sets of 2 (or 3). I was wondering if this could be done using the "Output Format" options in MC.

kiwi

Zoner · « **Reply #19 on:** September 05, 2003, 02:15:05 am »

kiwi: if you can find a DirectX plug-in which does that, it should work with MC9.1. If so, let me know, since I would be very interested in this, too.

Unless you're really short of power, I think DRC will improve sound much more than bi-amping your speakers, though.

kiwi · « **Reply #20 on:** September 06, 2003, 09:43:15 am »

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kiwi: if you can find a DirectX plug-in which does that, it should work with MC9.1. If so, let me know, since I would be very interested in this, too.

If/When I find this, I will definitely let you know. I think that there may be a technical issue with increasing the number of channels in the output, though, that might just be from w/i the MC DSP plugin environment.

Quote

Unless you're really short of power, I think DRC will improve sound much more than bi-amping your speakers, though.

What I would really like to do is a combination of the two. I think that both are important. The big advantage to bi-amping the speakers is removing the crossover from the speakers and driving them directly from the amps. (Luckily, my speakers have external crossovers, so I can remove them and plug directly into the speakers themselves.)

I'm only just learning about all of the filtering stuff, but I would imagine that it would be easier to perform RCS if you didn't have to worry about the crossovers that were in the speakers.

kiwi

Zoner · « **Reply #21 on:** November 09, 2003, 07:05:35 am »

Does anyone have any news to report on this?

kiwi · « **Reply #22 on:** November 09, 2003, 05:25:06 pm »

Not a lot that's new. I found another company that has an interesting program, but it's a bit expensive:

Sounds Logical WaveWarp 2.0
http://www.soundslogical.com/products/wavewarp/wavewarp20.html

It looks to be extremely powerful.

At $199, it's expensive, however, when you think about how much some people spend on HiFi equipment, this isn't that expensive and it has the potential to drastically improve sound quality.

kiwi

Zoner · « **Reply #23 on:** November 10, 2003, 01:46:12 am »

Will that give me a convolver filter in MC9?

kiwi · « **Reply #24 on:** November 10, 2003, 01:38:02 pm »

I haven't experiemented with it. I'll download the demo today and see what options it has. You can create DX plugins, so I imagine that you can throw one into MC and have your filter. It looks to be a flexible tool.

On of the options it has allows it to be integrated into MatLab, which generally is aimed at more scientific/high end products.

Hopefully the demo will be informative.

kiwi

kiwi · « **Reply #25 on:** November 10, 2003, 03:17:01 pm »

What exactly is a convolver filter?

These are some of the filters that they talk about:

Quote

Recursive (IIR) digital filters including Butterworth, Chebyshev, Inverse Chebyshev, & Elliptic designs; generalized 2nd order highpass, lowpass, bandpass, bandstop, peak & notch designs; all-pass designs; non-recursive (FIR) digital filters including windowed lowpass, highpass, bandpass, bandstop designs, in both direct and fast (FFT-based) implementations. Most filters include an ASCII file interface for implementation of off-line filter designs (e.g. via MATLAB, with m-files included).

Don't know whether anything listed here would do it... and/or whether they have any ways to extend it to perform a filter of your own.

kiwi

kiwi · « **Reply #26 on:** November 10, 2003, 03:18:33 pm »

Just found this:

Quote

Spectral Transformers : Frequency-domain algorithms such as convolution, spectral cross-synthesis, spectral shaping, etc.

Edit: I won't repeat all the stuff that's there, but it looks like it can generate signals too... that could be used for doing the initial setup/calibration. Poke around on the website. It actually looks pretty cool. It might even allow for 1 to multiple input conversions. Now I just have to see whether MC will allow for that.

kiwi · « **Reply #27 on:** November 10, 2003, 03:40:01 pm »

Some more information:

Convolver
http://www.wavewarp.com/faq/5.3.html

Performing Different filters on each channel
http://www.wavewarp.com/faq/5.1.html

At the moment, it looks like it uses the WAVE outputs. I don't know exactly how this works with MC (hopefully their ASIO support will be coming along soon.):
http://www.wavewarp.com/faq/4.9.html

INTERACT FORUM

Author Topic: Digital Room Correction: Convolver filter? (Read 7047 times)

MachineHead

Flobalob

Flobalob

MachineHead