[ccd]

I know of good convolution SW for DRC, but is there any good SW for doing digital crossovers?

 

[Jones_Rush]

Can't BruteFIR do it ?.

 

[dwk123]

BruteFIR can _run_ the xovers if that's the question. Also, there are a variety of LADSPA plugins that can be used to implement generic IIR filters as well. jack-rack in conjunction with jack is a good way to handle that.


If the question is how to _design_ the filters, then you're still on your own. I've been hoping to be able to write and contribute this kind of tool, but I just haven't had the time. Maybe soon, though, since I just found out that my employer is going out of business, so I'll be out of work in a month or so :-(

 

[ccd]

My thought is that I can have a Linux server and a Windows media client by using the software at www.videolan.org Ideally, I'd like the Linux server to handle both DRC and crossovers.


My understanding is that the DRC program will generate the filters to be run on ButeFIR and that the only question is how much processing power I need for the number of channels I want to have (in my case, 12-14). This is all well and good as long as your speakers have passive crossovers, but I want to go active so I need a way to generate those filters as well.


My question, which I believe one person has answered, is whether there is software out there to generate the crossover filters. Perhaps one solution might be to let ButeFIR deal with DRC but let a DSP card handle the crossover? If this is possible, how difficult would it be to get the card to do the crossovers?

 

[Jones_Rush]

ccd, which sound card do you have, that has so many output channels ?.

If I understand correctly, some of the channels will go to the same speaker (to different drivers), right ?.

 

[ccd]

Jones:


This is a viability exploration. I'm building a PC in an adult ed. class next month and I want it to be a HTPC, which should not be a problem since each student is responsible for buying his/her parts. I figured that this would be a great way to start as I'd have teachers to help me out, at least initially.


I was also going to build a HT system using two Behringer 2496DCXs which can be configured for 5.1. As the reputation of Behringer is mixed and I was going to build an HTPC anyway, the thought was why not put the money I'd spend on the Behringers into my HTPC. The Behringers can do crossovers for five 2-way speakers as well as EQ.


I am starting with what can be accomplished by a relative novice, once I'm convinced of the proper approach, I'd then turn to HW like soundcards. There seems to be soundcards which can do the job, like the Lynx AES16 which has 16 channels or I could double up on sound cards from M-Audio, for example.


As it turns out, I don't think many channels will be required. Based on comments here and elsewhere, short of doing my own programming, there are two choices:


1) KISS which while boring would leave me with two 2496DCXs doing Xover and EQ, and would keep the HTPC pretty straightforward; or


2) Use passive crossover for the speakers and do DRC thru the HTPC, which would only require 6-7 channels. The HTPC would be more complicated here with the Linux server and Windows media client, but the SW and HW to make this work is available. DRC can generate the filters to be run by BruteFIR and 6-7 channels should not require any particularly large amount of processing power.


I'm favoring (2) with an external passive crossover. This way, I could still easily implement an active crossover with minimal effort. The only avenue I haven't explored is some kind of DSP card with a DSP designed to do audio crossovers. AD has such a DSP card. The card would still have to be programmed and I just don't know how difficult that would be. I'm also not sure how all the pieces would go together or how easy it would be to obtain the cards.


Even (2) is a bit of a stretch as I don't know anyone who has actually done a Linux server with a Windows media client with videolan


Hope this answers your questions and lets you know what I'm trying to do.

 

[dwk123]

I'd forgotten about this resource, but it's a pretty good place to start, at least if you have access to a Windows box with excel

http://www.pvconsultants.com/audio/frdgroup.htm


There are a bunch of tools to create/manipulate response files. If you use the 'rect linear' format (stupid name IMHO) as used in the 'TFD' and 'DSP Tools' sections, you can convert them to BruteFIR compatible format simply by running them through and FFT stage.

 

[rrozman]

Hello,


could someone point me to more info or explain in few words what crossover is?


Thanks,


Robert.

 

[slehman]

Quote:

Originally posted by dwk123 If the question is how to _design_ the filters, then you're still on your own. I've been hoping to be able to write and contribute this kind of tool, but I just haven't had the time. Maybe soon, though, since I just found out that my employer is going out of business, so I'll be out of work in a month or so :-(

The formulas for filters found in basic crossovers are nothing all that amazing. The 4th order Linkwitz-Riley crossover commonly used for its phase coherence at the crossover point is really just two 2nd order butterworth filters in series. Some butterworth filter structures would take a heck of a lot less CPU power than BruteFIR too!


As for software that does it on Linux, I have nothing to suggest - I'm actually a Mac guy and audio programming hobbyist passing thru.


Scott