Correction of room acoustics. E-traps?

I get your point but think you are too liberal in saying it is "in the signal path." That definition might include everything in the room, including us.

Also, note that a room mode at 30Hz is usually accompanied by submodes at all the harmonics, as well. That suggests that any out-of-phase harmonics from the E-trap might even have a salutary effects. (Wild thought, no?) I thought the E-trap quite effective but very subtle in its action and it was accompanied by no noticeable negative effects, in practice.

Now, I am not suggesting that the E-trap is panacea but it is one of many tools, each useful when appropriate.

I do agree with your preference for physical room treatments as the first and foremost way to deal with room acoustics but, where one cannot (for any reason) accomplish enough that way, electronic devices can be very helpful.

Kr4,

Perhaps I am a bit overzealous compared to most people on distortion. For example, I would like an acoustic drum set or a double bass to sound like well er actually an acoustic drum set or a double bass - and not something else altogether different. I mean what you get with a lot of ultra LF audio reproduction these days is impressive and sounds very nice but it sure isn't very accurate - a lot of it is due to the transients that don't sound right but it is also a function of added harmonics which changes the timbre. I guess you could say I am in the very small minority camp of "no sub" or "no ultra-LF" being preferable a bunch of distortion. I am serious when I say that it is hard to build something that goes as low as bag end requires with less than 10% distortion at a useful volume level - so if you are aiming to tackle room problems - what else might an active device like this be inadvertently doing?

How can the E-trap add audible distortion at higher frequencies when (1) it is not in the signal path and (2) it is sharply frequency limited by design?

Good question.

(1) It is in the signal path in the sense that it is making acoustically audible signals in your room (although these are 'corrections' or 'damping' there is every possiblity that other detrimental audio is generated)

(2) The amplifier circuitry is no doubt sharply frequency limited by design....however a transducer is NOT. Most of what you hear from an impressive subwoofer is harmonic distortion...that is the intended signal at 30 Hz is actually nigh close to inaudible (due to fletcher Munson curves our hearing is pretty insensitve there) but the 20% harmonic distotion at 60, 90, 120 and 150 Hz is absolutely impressively deafening!!!

Think twice next time you hear an impressive subwoofer - with the majority of them you are simply hearing huge amounts of distortion.

So lets assume the bag end has an impressive 10% harmonic distortion and you use it to fix a 30 Hz ringing problem....what happens at 60 Hz and at 90 Hz (where you might have a NULL and need a boost not a cancellation)....that is my point!!!

The nice thing about broadband passive absorbers is that they add NO harmonic distortion...

Shadorne-

How can the E-trap add audible distortion at higher frequencies when (1) it is not in the signal path and (2) it is sharply frequency limited by design? I take your point about potential THD in the low bass but the ear is more tolerant to that and its contributions are at frequencies which are already 'distorted' by room acoustics.

Kal

This can be much more effective than passive traps ( at least 10 and probably around 100 times more effective than passive broadband absorbers for equivalent size ). Special specific tuned tubes traps with helmoholtz tuned resonance will not be able to compete either. Looks like a great product but I have not seen this before - thanks for bringing it up.

One caveat, however, this is a speaker and like all speakers it can add lots of audible distortion (most subwoofers have terrible distortion levels of 20% and much more at the low frequencies below 40 Hz - only the very biggest subwoofers and with the most expensive drivers will approach audiophile distortion levels of 1%) So it would be great to knock out a room mode but not so great if it adds audible harmonic distortions at higher frequencies...

Based on what Bag End say it appears that this is recommended after regular passive acoustic treatments have been added. (i.e it is not the "one-stop answer to all needs" but is part of an overall solution which might also include a PARC and plenty of bass traps and wall treatments.)

FWIW - one Daad bass trap is not enough - unfortunmately size matters. I have four massive GIK tri-traps ( corner traps that are similar to DIY "Superchunks" ) and while it makes a big difference in the mid bass and lower mid range even four of these monsters does little to tackle the sub 50 Hz frequencies although I believe the biggest benefit is the NULLS.

I use a PEQ on my sub to tame the worst humps and it is not necessary to go for a flat bass response - often this sounds plain wrong and lacks life, IMHO. It is the improvement from taming 10 to 20 db peaks to within about 6 db of flat which is were the most imporvement comes from electronic notch filtering. I think the big problem for people who use ONLY electronic filtering to tame peaks is those nasty pesky persistent NULLS. Only broadband acoustic treatments distributed all around the room (all four corners) seem to work. The NULLS are actually the worst nightmare as the sound disappears...a particular bass note on a riff can nearly disappear - completely changing the sound of the music. IMHO the more andf different type iof treatments you can throw at it the better.....remember that in order to hear a note you just need to ensure some of the harmonics make it through clearly and the worst case is when all the harmonics of a note are simultaneously supressed...for exampe a null at 36 Hz and again at 72 Hz. The more varied your approach to tackling the room modal issue the better chance that nothing knocks a particular note dead!

It works well. See: http://www.stereophile.com/hirezplayers/708mitr/index1.html and it make no compromise at all of your electronics.

The PARC/subPARC are more universal and general solutions.

You might consider learning to do some simple measurements to determine the nature of your problems before trying to cure them.

Kal