AsioXO - New Digital crossover for the windows platform

[Henckel]

Patrick Cazeles has kindly contribute a program to the community that can do digital cross over and convolution ( for digital room compensation)

The program and step by step procedure for installation and operation can be found at;

http://www2.gol.com/users/pcazeles/asioxo.htm

Enjoy

Morten

[Petter]

Since nobody else is posting, let me provide some encouragement!

Also, does this work with other media players such as Windows Media 9 Series and Windows media files?

Petter

[jwb]

A related bit of software that I get lots of use from is BruteFIR. You can find it here:

http://www.ludd.luth.se/~torger/brutefir.html

-jwb

[Henckel]

Originally posted by Petter
Since nobody else is posting, let me provide some encouragement!

Also, does this work with other media players such as Windows Media 9 Series and Windows media files?

Petter

No it is a standalone application that only can play back Wave files i.e ripped Cd´s

It contains also an upsampler.

To some extend this program can be compared to the functions of the Behringer DCX and the TACT room compensation unit - not bad for a free piece of software.

[jkeny]

Thanks for the reference Morten - excellent. Exactly what I am looking for and fits my needs as I suspect the needs of many here who contributed avidly to the threads on PC as CD player and "DIY CD drive based on a computer CDROM"

Morten, Have you implemented any of this yet?

I tried to install the software and get error "mscoree.dll could not be found" when trying to launch eacPlayer. This dll is a file from Micosoft .NET framework. This implies (but is not clear from the documentation) that .NET needs to be implemented even though webEAC is not being used.

Other problem which may be fundamental is that it uses IIR filters and not FIR filters which are apparently more accurate. (I haven't heard either so this would act as a first intro to digital filters and I don't know how big the quality difference between filters. FIR filters seem to require a llot more processing power that IIR so older less powerful PC's may suit.

Anyway thanks for the ref
John

[Henckel]

Originally posted by jkeny


Morten, Have you implemented any of this yet?

I tried to install the software and get error "mscoree.dll could not be found" when trying to launch eacPlayer. This dll is a file from Micosoft .NET framework. This implies (but is not clear from the documentation) that .NET needs to be implemented even though webEAC is not being used.

You need to install IIS prior to installing .NET

it is runing on my machine - but i can not verify with measurement the cross over function.

This is because the Asio driver is sset to record form Asio device #1 and my input on my soundcard is on Asio input #2

Originally posted by jkeny

Other problem which may be fundamental is that it uses IIR filters and not FIR filters which are apparently more accurate. (I haven't heard either so this would act as a first intro to digital filters and I don't know how big the quality difference between filters. FIR filters seem to require a llot more processing power that IIR so older less powerful PC's may suit.

Anyway thanks for the ref
John

It acually uses FIR for the room compensation part ( i.e convolution) and is using IIR for the cross over function ( after the convolution).

and I agree with you that this is a starting point - FIR would be the "best" implementation.


Morten

[Thunau]

Originally posted by Henckel






It acually uses FIR for the room compensation part ( i.e convolution) and is using IIR for the cross over function ( after the convolution).

and I agree with you that this is a starting point - FIR would be the "best" implementation.


Morten

I didn't download the application and only looked at the pages. I think that it is a cool step toward the music PC. I have one gripe though. From what I see the choice of crossover curves is limited to only one or two 2nd order (what Q?) filters per output. To make it more usefull in constructing crossovers, the user should be able to insert/stack multiple first and second order (with adjustable q) filters per output. A few bands of parametric EQ and one delay per output would be great too. All this could be acomplished relatively easilly with textbook IIR filters. A user could design a very good crossover in lspCAD or similar loudspeaker software and just type in the frequencies and q's in the ASIO XO. This would turn a regular version of lspCAD into the pro version ($375.00 saving). I do have the pro version but it lacks the cool playback features found in ASIO XO .
So, how about some more sophisticated filtering?

[jwb]

IIR is a poor choice for crossover because it is not phase coherent. Best to stick with FIR. Even an 8-year-old PC can do 1000-tap FIR filters on 24 channels simultaneously. Normal 2-6 channel 2 or 3-way crossover setups should be possible on nearly any computer still running today.

BTW, I use Matlab to generate FIR filter coefficients. It works great.

[Thunau]

Originally posted by jwb
IIR is a poor choice for crossover because it is not phase coherent. Best to stick with FIR. Even an 8-year-old PC can do 1000-tap FIR filters on 24 channels simultaneously. Normal 2-6 channel 2 or 3-way crossover setups should be possible on nearly any computer still running today.

BTW, I use Matlab to generate FIR filter coefficients. It works great.

And how do you derive "phase coherent" filters for individual drivers in your loudspeakers? I don't see where you insert the coefficients in the legs of the crossover.
BTW, what does "phase coherent" mean?

[jwb]

Originally posted by Thunau
And how do you derive "phase coherent" filters for individual drivers in your loudspeakers? I don't see where you insert the coefficients in the legs of the crossover.

Simply choose your crossover frequency and find two same-order FIR filters, one high-pass and one low-pass, with 3dB corners at that frequency. As I said, I let the Matlab Filter Deisng Toolbox do the heavy lifting for me. I don't know how to pick filter coefficients. And, not having used this particular program, I really don't know how you would feed the coefficients into it.

BTW, what does "phase coherent" mean?

I hope this isn't a test, because I'm not a DSP expert and I can't give you the formal definition. But, with a FIR all frequency components experience the same delay. If you have a FIR filter high-pass and low-pass of the same order, you can add the resultant signals together and reconstruct the original signal, including phase, to within a fraction of 1dB. This is not possible with IIR filters, which have lousy phase response. Most analog filters also have lousy phase response. By constract a FIR filter can have as high an order as you desire, with perfect phase response.