40hz room mode RPG Modex Corner trap?

Nik,

I think most DSP's have digital notch filters.

I have an Anthem AVM 20 (second hand of course) which I feel is great value considering all the features and XLR outs. Good enough for me anyway. There are many other DSP's and some with more expensive DAC's than the AVM 20...so look around...maybe a Krell or Classe.

Myself I am not so worried about DAC quality and have not tested a lot of high end DAC's. I have never heard a TACT 2.2 for example - so I am not sure I can advise which DSP has the best. I am far from an expert on the various DAC's. It seems to be a whole area that I can't fathom....once distortion + noise figures get close to one hundredth of 1% then I feel well satisfied. (as my speakers put out 100 times that level of distortion.)

All I can say is that my AVM 20 helped clean up a nasty 40 Hz bump I had from room standing wave....no doubt other DSP's can do the job just as well....after all digital filters are just software programs. And I am almost certain that I could not achieve the same sharp notch with an analog EQ (at least not at a reasonable cost)

Nik--sorry been away from the gon for a while. The Modex has not been effective in our practical experience. It wasn't even an issue of how many. As to the Helmhotz--these are very tricky. Alton Everest does a nice write-up on them in Master Handbook of Acoustics. The issues become how rigid to make the box (determines Q factor) and how large (determines db drop).

I'm trying to learn about this stuff, too. So, my comments are those of a seeker, not an expert. I think the Behringer goes between pre-amp and amp, operates in the digital domain, and its output must be converted back to analog. So, it's not the best approach for someone using an analog (vinyl) front-end. The Rives PARC is all analog, which IMHO is a better hi-fi approach. The trade-off is that Behringer offers something like 32 bands, while PARC offers three. But I think three bands is enough, because this allows you to flatten the first three room peaks, and multiples thereof. And, whether with Behringer or PARC, you still need bass traps for the nulls. At any rate, I wouldn't use Behringer in my system. I'm saving my pennies for Rives PARC.

Jburidan...The PARC is by all accounts a fine piece of equipment, and if you can afford it and buy it I am sure you will see a big improvement in your system.

However, for other readers, if not you, I do want to correct several comments and misconceptions about the Behringer.
1..Unlike the PARC it can boost as well as cut. (Word on the street is that a future version of PARC will do this also).
2..It includes a 61 band specteum analyser (or Real Time Analyser, RTA) so you can easily see what is wrong and how it gets fixed.
3...It has a completely automatic equalization process that eliminates a lot of guesswork. (And is fun to watch).
4...As you say, it has many (31) bands, with bandwidths adjustable from 1/3 octave and up. But it also has several bands of parametric equalization, and several notch filters (cut only like PARC) with bandwidth as small (sharp) as 1/60 octave. There are a bunch more things it can do, but with the possible exception of delay (to compensate for speaker locations) you probably would not use them in the home audio application.
5...It is digital. IMHO, to reject it simply for this reason, without ever actually listening to it is stupid. The A/D and D/A are modern 24 bit modules run at 96KHz. FWIW, 24 bits gives resolution 256 times better than a CD, and the bandwidth is more than double. The actual digital processing is done by a 32 bit Floating Point processor, so there is no issue of resolution for this function. Of course these are all words, and one should not accept them as a garantee of good sound any more than one should accept your suggestion that the sound must be bad. Please reserve judgement on how the Behringer sounds until you hear one.
6...Finally, it costs about 1/10 of a PARC. This is a good deal for a spectrum analyer (to help with your PARC setup) even if you are never curious enough to put the Behringer in your signal path.

Probably should pick up a copy of the Master Handbook of Acoustics to learn a bit more about the basics.

The basic school of thought that I have got off several forums is that Broadband bass trapping is the simplest acoustical method of dealing with room modes with my situation. I guess what people are telling me is that with increased broadband bass trapping I can bring up the nulls around 40hz and cut a bit on the 40hz hump. I think that the idea is that while I may not get a huge cut at 40hz if things are over all smoother my ears will fixate less on the problem area. I'm going to give this a try and then may explore other options.

As to the Behringer, it really seems to be a smoking deal in terms of features/price and as noted the spectrum analyzer function alone could be very useful. I think that many people are suspicious of adding another set of A to D to A to their system. I guess it is simple to try it with all settings flat and see what it does to the analog input. If it doesn't adversely effect inputs from vinyl or SACD then a suppose then hey there you go. I actually have few doubts about the digital side of the Behringer, but would be shocked if the analog output circuity cost more than a $1 ... it may sound pretty good but no matter how good your source you are now limited by the Behringer's output quality. For myself if I was running a transport / DAC set up like I was a couple years ago I would jump on trying it between the two. In that situation I would have all the benefits and still have my DAC's analog stage in line with the preamp.

Eldartford, in your system is the Behringer transparent with everything flat and using an analog input signal?

Thanks