(MOVED) - FIR discussion spinoff

[Arthur Skudra]

Re: (MOVED) - FIR discussion spinoff

Keep in mind the FIR filter implementation in the context of the MiniDSP and similar products is geared towards those who wish to develop their own custom inverse room curves (typically for auto-eq setups in home theatres). You know, and I know, that in live sound, auto-eq is a lame attempt to appease beginners into thinking they can equalize their systems and not worry about positional anomalies.

FIR implementation in live sound has it's applications, however you'd want to do this carefully under very controlled circumstances, not with the speaker hung 40 ft up in the air, in a giant shed (though I've done that before with some limited success with a simple 2 pole all pass filter). The type of FIR implementation that some loudspeaker manufacturers are doing for loudspeaker correction is more a result of some serious math calculations based on computer simulations and modeling, not something that they stick a mic in front of the speaker and presto, out comes a FIR filter that's "just right." This is not to say they don't use FFT analysis to fine tune the resulting speaker optimization.

 

[John Roberts]

Re: (MOVED) - FIR discussion spinoff

I am always apprehensive about letting punters play with sharp knives.. These sound like useful tools for OEM engineers and very advanced users, not billy the beater.

JR

 

[Jeff Babcock]

Re: (MOVED) - FIR discussion spinoff

The type of FIR implementation that some loudspeaker manufacturers are doing for loudspeaker correction is more a result of some serious math calculations based on computer simulations and modeling, not something that they stick a mic in front of the speaker and presto, out comes a FIR filter that's "just right." This is not to say they don't use FFT analysis to fine tune the resulting speaker optimization.

Very true and well noted Arthur. The modeling and related math legwork that goes into this is the part that is beyond the means of the average person at this point in time. Determining and accounting for the stuff that is "linear time invariant" is the goal, but a measurement mic is not really the weapon of choice here.

Nevertheless, just creating brickwall crossover filters along the lines of the lake processors is of benefit in some circumstances, and this is achievable in DIY FIR with a little effort. You could make "flat phase" presets using FIR brickwall filters and traditional allpass filters that might not be in the same league as a FIR preset by companies like Fulcrum, but they would certainly have potential for high quality and very affordable processing for a user with the right know-how.

 

[Langston Holland]

Re: (MOVED) - FIR discussion spinoff

I am always apprehensive about letting punters play with sharp knives..

Another keeper!

Remember the Thermos!

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For those interested in the effective limits of small room acoustics "correction", a wonderful intro is included in the REW v5 manual beginning with the section on minimum phase (pp. 50ff.).

 

[Tim McCulloch]

Re: (MOVED) - FIR discussion spinoff

I am always apprehensive about letting punters play with sharp knives.. These sound like useful tools for OEM engineers and very advanced users, not billy the beater.

JR

Billy Vera and the Beaters, or Billy and the Boingers (Bloom County)?

 

[Silas Pradetto]

Re: (MOVED) - FIR discussion spinoff

But have they designed a tool that lets Joe Schmoes like me actually build FIRs? There are plenty of DSPs that you can stick a several millisecond FIR into, but making one (and doing it smart) in the first place is beyond most mere mortals.

Yeah. Most people can barely set up a decent phase-coherent crossover, nevermind something that probably only 10 people in the world can do.

 

[Jeff Babcock]

Re: (MOVED) - FIR discussion spinoff

Yeah. Most people can barely set up a decent phase-coherent crossover, nevermind something that probably only 10 people in the world can do.

Actually, while the world of FIR designers is small, it would certainly be much larger than 10. FIR is making significant inroads into other audio markets, such as HiFi. Look at how many companies just in the pro audio market have gotten into FIR....

I can list more than 10 pro audio companies off the top of my head..... EAW, Fulcrum, JBL, EV, Mackie, Yamaha, D&B, L-Acoustics, Turbosound, KSAudio, Duran, Renkus Heinz etc, etc.

My point is simply that FIR is here to stay and I fully expect its use to grow exponentially as DSP costs are reduced. FIR is certainly not trivial, but is not a "holy grail" either. It is within reach for companies with bright minds willing to put in the R&D effort.

 

[Mark DeArman]

Re: (MOVED) - FIR discussion spinoff

Well I'm pretty sure the Camco people at the university up there in Germany have been doing inverse filtering research for a while. They had some point-and-shoot tools even four years ago which worked pretty well for Nexo two way boxes when I saw them.