Corner Bass Traps - Always beneficial?

[amirm]

I guess it depends on the context of the rest of your system. Rooms are IMO the largest influencers of what you hear after speakers. So it would be speakers --> room --> everything else a lowly third.

I will have to disagree Nyal . If you start with the wrong speaker you can do all you want and you still have a broken experience. Of course in low frequencies the room is control and something must be done to restore smooth response. Above there though, speaker design and performance is very important as it dominates the sound we hear. I have taken good speakers and put them in horrible places and you still get a nice experience. The reverse is not so true.

This is a nice graph that I borrowed from Alan Devantier (of Infinity/Harman fame):

I think the right answer is that sometimes one matters more than the other. So you would want to do both. Trying to assign priorities just gets one in trouble .

 

[dallasjustice]

About the only commercial thing that works properly down that low is RPG Modex Plates. You can build custom stuff that is very effective down that low too. Some other products have some absorption down at 50Hz but they are tapering off in effectiveness pretty fast.

Did you see Kal's article on page 59 of September Stereophile? He tested Grimani's MSR Springtraps and took measurements with XTZ. He only had two springtraps and they worked well down even around 30hz.

 

[Rutgar]

I guess it depends on the context of the rest of your system. Rooms are IMO the largest influencers of what you hear after speakers. So it would be speakers --> room --> everything else a lowly third.

I get what you're saying Nyal. One thing I will say that I find interesting about them, is that some models (such as the Modex Module) appear to effect targeted frequencies, which allows choosing ones for specific control of only the troublesome frequencies.

Edit: But I believe that brings up another question; Is it better to use lots of broadband bass trapping to smooth out the entire modal region? Or to go more with tuned devices, targeting just the most problematic nulls and peaks?

 

[Rutgar]

Did you see Kal's article on page 59 of September Stereophile? He tested Grimani's Sprintraps and took measurements with XTZ. He only had two springtraps and they worked well down even around 30hz.

I missed that Michael. I will have to check that out.

 

[Nyal Mellor]

I will have to disagree Nyal . If you start with the wrong speaker you can do all you want and you still have a broken experience. Of course in low frequencies the room is control and something must be done to restore smooth response. Above there though, speaker design and performance is very important as it dominates the sound we hear. I have taken good speakers and put them in horrible places and you still get a nice experience. The reverse is not so true.

This is a nice graph that I borrowed from Alan Devantier (of Infinity/Harman fame):

I think the right answer is that sometimes one matters more than the other. So you would want to do both. Trying to assign priorities just gets one in trouble .

Amir, we are in perfect agreement

 

[Nyal Mellor]

I missed that Michael. I will have to check that out.

I'm still waiting for mine to show up in the mail. Kal said he's going to get me the XTZ files before / after.

 

[Jeff Hedback]

broadband or tuned?

So Rutgar asks is it better to use broadband traps or tuned traps? Earlier in this thread I showed an example of corner trapping with Ethan's Mega Traps (front vertical corners) and GIK's Monster traps (along the sidewall to ceiling juncture, (4) per side).

Now I'll share some work that is in progress right now. The room is the recording studio control room for Indiana University. A small program with little support from the school, but doing excellent work in audio recording eduction. They had limited funds but endless "elbow grease". The basic room is concrete (all six surfaces) with a drop tile ceiling and R-19 fluffy insulation above. That is the starting point of the before resonance graph.

Based on in-room acoustical data and BEM predictive modeling, I designed three types of tuned traps. One with center freq 30Hz, another at 80Hz and the third at 140Hz. Their "Q" are lo/wide and intentionally are designed to work like you'd expect a crossover to perform so that they are at ~.8 efficiency at center frequency and ~.4 to .5 efficiency where they overlap.

These are Burst Decay's from ARTA, but I could have shown waterfall's from other programs just as easily. They are looking at 60dB range, so deep into the noise floor. I also included the T30 and 1/24th smoothed freq response which is excellent at this high resolution, +/- 5dB (both speakers being driven).

There are (7) of the 30Hz, (3) 80Hz and (4) 140Hz devices. Each is 18"x48" and the parts are simple: plywood boxes with seams sealed, 4" Rockwool glued to 1/4" hardboard facing. The facing boards have 1/4" drill holes at a very specific spacing to reach the above described center freq and Q. There is only one other change in the Before & After tuned traps, a plywood deck riser was designed and installed to hide cable runs...more on that below.

So you can easily see the improvement in the target ranges!! Good design and execution. We also now have a ghost in the closet exposed...the resonance at ~55-60Hz. Hmmmm. As this data just came in yesterday, I don't yet know what that is from. But it is not modal...why? Reference the freq response, there is no peak...as Dr. Toole wisely describes modal resonances and peaks in the LF range are tied together...can't have one without the other. Next, look carefully at the slope of the After...the resonance doesn't start until ~ 25-30dB down in the decay rate. That is shared by the T30 graph. It will be found, but my guess is that there is some structure up in the drop grid that is resonating. This is not a purpose designed space (quite the opposite). So the analysis process has exposed something that really couldn't be separated from the general clutter before the traps. More work to do!

 

[Jeff Hedback]

...but I didn't answer the question posed

And the answer is (in my opinion), either can work. However, broadband traps are much easier to grab and go. Tuned traps have to be designed, executed and located properly to work...but they certainly are great options.

On the MSR spring trap, I worked with a guy last fall who had two of them. We did before and after measurements and they really do seem to be effective.

 

[amirm]

Nice job there. When analyzing my room I also ran into ghosts. I was getting strange resonances in the 100 to 200 Hz. I thought it was the sub. So I played it alone and sure enough it would sound distorted if I did not heavily filter its highs. I thought the driver was resonating (a weakness in its design). Well, turned out it was the duct work that was doing it! From my listening position it sounded like it was the sub. I had spent a ton of money having low velocity duct work. But the contractor had never done this type of work before and it showed. It was a disaster once I took the grill down with loose couplings and ducts that resonated at those frequencies. A gallon of HVAC mud took care of 90% of it. It was uncanny how it sounded like it was the sub.

 

[Ethan Winer]

Is it better to use lots of broadband bass trapping to smooth out the entire modal region? Or to go more with tuned devices, targeting just the most problematic nulls and peaks?

One important reason to favor broadband absorption is it targets non-modal peaks and nulls cause by boundary interference. Not all peaks and nulls are modal. But broadband bass traps need to be very thick to target the lowest octave.

--Ethan

 

[NorthStar]

Amir, we are in perfect agreement

-----That was also exactly what I read. :b

1. The Speakers (first).
2. The Room (second).
3. Everything else (third).

________________________________

*** Invite several beautiful women to your home, and have a very nice glass of wine with them, but with only one of them at a time, and in your most 'cherished' (best sounding & perhaps best looking) room. Then talk with her (your guest, the speaker) and listen to her voice, attentively ...

Do the same with all the twenty gorgeous women you invited over a period of twenty days.
Listen very carefully each day to each one of them when she is talking, speaking.

Also, pay attention to the content of her message (what she is saying and how she is saying it).

Voila! :b

 

[NorthStar]

_When you find the right one(s), you'll know, she'll be following you to another room of your home; the bedroom.

 

[microstrip]

-----That was also exactly what I read. :b

1. The Speakers (first).
2. The Room (second).
3. Everything else (third).

Bob,

As you summarized I will express my disagreement answering to your post.

IMHO, this type of ranking is meaningless, and when expressed in three lines without comments somewhat bizarre.

In order to listen to music I choose a type of sound reproduction that maximizes my pleasantness and preferences, better enjoying the recordings. Focusing my main interest in both LPs or CDs I looked for source equipment that I really appreciated. In order to maximize the compatibility, I choose then the reminder of my electronics system and only after that I have chosen the speakers. Considering the quality of most current high-end speakers, I could have happily lived with any of the many speakers that entered my room. I would not say the same about all the electronics and sources I have tried.

I changed speakers recently and because of that move I am re-doing the acoustic treatment of my room.

So my order would be:

1. Source and electronics
2. Speakers and cables
3. Room
4. Everything else

All IMHO, of course!

 

[NorthStar]

I guess it depends on the context of the rest of your system. Rooms are IMO the largest influencers of what you hear after speakers. So it would be speakers 1st --> room 2nd --> everything else a lowly third 3rd.

I will have to disagree Nyal . If you start with the wrong speaker you can do all you want and you still have a broken experience. Of course in low frequencies the room is control and something must be done to restore smooth response. Above there though, speaker design and performance is very important as it dominates the sound we hear. I have taken good speakers and put them in horrible places and you still get a nice experience. The reverse is not so true.

This is a nice graph that I borrowed from Alan Devantier (of Infinity/Harman fame):

I think the right answer is that sometimes one matters more than the other. So you would want to do both. Trying to assign priorities just gets one in trouble .

Amir, we are in perfect agreement

-----That was also exactly what I read. :b

1. The Speakers (first).
2. The Room (second).
3. Everything else (third).

________________________________

*** Invite several beautiful women to your home, and have a very nice glass of wine with them, but with only one of them at a time, and in your most 'cherished' (best sounding & perhaps best looking) room. Then talk with her (your guest, the speaker) and listen to her voice, attentively ...

Do the same with all the twenty gorgeous women you invited over a period of twenty days.
Listen very carefully each day to each one of them when she is talking, speaking.

Also, pay attention to the content of her message (what she is saying and how she is saying it).

Voila! :b

Bob,

As you summarized I will express my disagreement answering to your post.

IMHO, this type of ranking is meaningless, and when expressed in three lines without comments somewhat bizarre.

In order to listen to music I choose a type of sound reproduction that maximizes my pleasantness and preferences, better enjoying the recordings. Focusing my main interest in both LPs or CDs I looked for source equipment that I really appreciated. In order to maximize the compatibility, I choose then the reminder of my electronics system and only after that I have chosen the speakers. Considering the quality of most current high-end speakers, I could have happily lived with any of the many speakers that entered my room. I would not say the same about all the electronics and sources I have tried.

I changed speakers recently and because of that move I am re-doing the acoustic treatment of my room.

So my order would be:

1. Source and electronics
2. Speakers and cables
3. Room
4. Everything else

All IMHO, of course!

-----Micro, that would also mean that you disagree with Nyal and Amir as well.

- And me I said it a million times before: the Music (software) is first. ...The recording quality.

 

[microstrip]

-----Micro, that would also mean that you disagree with Nyal and Amir as well.

- And me I said it a million times before: the Music (software) is first. ...The recording quality.

Bob,

I have agreed with all of you so many times that I can afford to disagree on this one!

BTW, my appreciation only applies to stereo listening. Perhaps it would be different for multichannel.

 

[NorthStar]

---We're cool then, as usually. :b

 

[Rutgar]

I would have to say the Room is first. Without it, your speakers and gear would be outside.
(surely I don't need to have to put one of those little smilely things after that remark)

 

[Bruce B]

Don't know if this has been posted yet.

 

[Bruce B]

And another...

 

[Nyal Mellor]

One important reason to favor broadband absorption is it targets non-modal peaks and nulls cause by boundary interference. Not all peaks and nulls are modal. But broadband bass traps need to be very thick to target the lowest octave.

--Ethan

Not necessarily, RPG Modex Plate is 4" thick...I would still call that broadband since it operates over a wide frequency range, not narrow like a tuned trap.