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Massive bass reverberation

dasdoing

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Yes, but AFAIK there is no consensus that 40Hz ringing is problematic at all and things like the AVAA may be of less value than one might think. I say this having paid close to 5000 for 2 AVAAs myself ;-)

Edit: See this post for studies about audibility of low bass ringing: https://www.audiosciencereview.com/...eq-also-passive-absorbtion.12264/#post-360270

thanks, I will study those studies later,

but I can tell you 2 things from personal experience after +10 years of treating rooms:

1) is hard to describe. I like to say that I "feel the pressure". It totaly got away after I brought the ringin down

2) even if you play a steady sine wave in a room at a mode frequency you can identify it. I am not sure why.....but it sounds like other frequencies are excited by it or something like that. it just sound bad. And I totaly believe when someone says they can't hear it. But once you hear it you can't unhear it
 

bo_knows

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You could also try to contruct the panel (diaphragmatic) absorber with the plywood.

More detail could be found in Master Handbook of Acoustics by F.Alton Everest and Ken C. Pohlmann.

You should be able to find the copy on the net, if not ping me and I will put the copy on my google drive.

1663435438884.png
 

bo_knows

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If I were pushing higher SPL on the low limit of the drivers, 32 Hz and 300 Hz for woofer and mid, then the excessive excursion could potentially damage them. But I thought it safe to push the upper range of the woofers since this is a low excursion range. Don't you think?

But point taken on the psychoacoustic versus var smoothing. I will definitely give it a try.

As for positioning, I put the speakers quite away from the front wall to reduce the 40 Hz mode (played around with the REW room simulator moving the speaker around and checking the predicted modes). This current position is roughly an equilateral triangle of 2.4m between speakers and the recliner chair, on axis.
I wouldn't go more than 1 meter from the front wall. It's enough with the room treatments to achive good sound stage depth and width. The further you go into the room, to lower the SBIR frequencies. IMHO, 40Hz wave is too long for you to move the seat/speakers and "excape" it.


1663438227513.png
 

Thomas_A

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Subs extend and distribute bass, and EQ I already use. Both do nothing to absorb long decays.
Check this out. Might give some ideas.

 

MAB

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No persistent LF noise. When the room is closed it is dead silent. Plus I live in a very silent street in a residential neighborhood, so as good as it gets.
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Is this your floor and/or ceiling vibrating? As you described in your original post:
walls made of concrete blocks, wood on the floor.
I am thinking of the wooden floor acting as a membrane attached to the rigid walls. Can this be???

I guess you could qualitatively estimate by creating an impulse to the floor (stamping around), and comparing to other rooms you have known. This seems pretty coarse, but gosh you have quite a peak there.... So if your floor was acting like a big drumhead, you should be able to excite the same with your feet.
Ceiling might be harder to do...
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Perhaps you have already considered this. Just wondering given the size and the persistent duration of the resonance.
 
OP
Matias

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I guess I can record the RTA while stomping around the room in silence. Better do this when no one is watching or else they may think I have lost my mind or something!
 

goat76

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To me, it looks like the frequency response is a little strange. I would expect the room response from the listening position to have a tilt down. And it clearly misses energy from 300Hz down to 80Hz, and that probably amplifies the impression of a boomy bass when listening to music.

I think you should try different positions for your speakers in the room to reduce the lost energy in the 80-300Hz region, and by doing that I think the sense of that bass boom will be reduced.

And another thing, the 40Hz and the 51Hz problems are room modes, therefore, they can never be reduced by moving the speakers because those problems are connected to the room and got nothing to do with the placement of the speakers.


When looking at the frequency response, it's pretty clear that the biggest problem is the lack of energy in the 80Hz to 300Hz region, and some of that is probably caused by the distance to the wall behind the speakers.

Matias Frequency Response Left Speaker.jpg
 
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Matias

Matias

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You could also try to contruct the panel (diaphragmatic) absorber with the plywood.

More detail could be found in Master Handbook of Acoustics by F.Alton Everest and Ken C. Pohlmann.

You should be able to find the copy on the net, if not ping me and I will put the copy on my google drive.

View attachment 231553
I have the physical book, I suppose I should study it further.
 
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FeddyLost

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Personally I'd recommend you to think about multi-sub configuration.
Because I also have smallish dedicated room with similar problems.
I've used a lot of fluffy rockwool, wood wool panels, some polyesther matts and decent amount of tuned limp membrane absorbers.
I've sacrificed 40 cm of room height and around 30% of floor area.
Anyway, the only one good solution below 100 Hz was a pair of sealed subs in the middle of side walls and MLP in the middle of room's transverse axis. So, subs are placed in zeros of first axial mode and MLP is placed in zero of first transversal mode.
I've lost the feeling of "pressurization" in lows and bass become "agile and flexible".
Still not a mastering studio grade, but better than i've ever achieved.
 
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Matias

Matias

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Truth be told that the psychoacoustic smoothing of my measurement and EQ was mixing both 40 Hz and 50 Hz as being the same thing when they were not. EQing to Var treated each peak separately and the muddiness is a lot better now. @DjBonoBobo thanks for catching that mistake.

For now I am good. Maybe when po$$ible I will revisit tuned membrane absorbers, DIY or bought. Thanks for all replies.
 
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Matias

Matias

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I wouldn't go more than 1 meter from the front wall. It's enough with the room treatments to achive good sound stage depth and width. The further you go into the room, to lower the SBIR frequencies. IMHO, 40Hz wave is too long for you to move the seat/speakers and "excape" it.


View attachment 231573
Currently my speakers are about 1.5 m woofer diaphragm to the front wall. This was deliberate to reduce the massive 40 Hz peak. The closer to the front wall, the more the speakers excite this. At least is what I saw simulated in REW and the position of the standing wave in amroc.

amroc.jpg
 
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Matias

Matias

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goat76

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I'd definitely try to fix that huge null in the midbass. I've had a similar thing and it really sucks the enjoyment out of music.
As I said earlier, I see the lack of energy 80Hz to 300Hz as probably the most problematic area in the measurements. If that can solve with just a different position of the speakers, I also think the room mode problems at 40Hz and 51Hz will be less noticeable.
As it is now, the most fundamental part of the bass region is missing and is probably dominated by that sub bass boom caused by the room modes.

After that part is solved, tuned absorbers and EQ adjustments to take care of the room mode peaks will probably solve the rest of the bass problems.
 
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Matias

Matias

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I see the lack of energy 80Hz to 300Hz as probably the most problematic area in the measurements. If that can solve with just a different position of the speakers
I moved the speakers around with REW's room simulator and I did not see significant changes in that area... I really don't know how to boost this without EQ, which fortunately is far from the max excursion ranges of the woofer (as I wrote here).

Any ideas?
 

bo_knows

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Currently my speakers are about 1.5 m woofer diaphragm to the front wall. This was deliberate to reduce the massive 40 Hz peak. The closer to the front wall, the more the speakers excite this. At least is what I saw simulated in REW and the position of the standing wave in amroc.

View attachment 232141
Cool, I'm glad that worked for you. I would think the more you move the speakers towards the center of the room, the further you have to sit (to keep the distance from the speakers the same as before) and closer to the opposite wall. I would think bass issues would be worse the closer you sit to the room boundery.
 

goat76

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I moved the speakers around with REW's room simulator and I did not see significant changes in that area... I really don't know how to boost this without EQ, which fortunately is far from the max excursion ranges of the woofer (as I wrote here).

Any ideas?

If it can't be solved by moving the speakers it must be a listening position problem. And by looking at your measurements again that's probably the most likely cause, those nulls at 120Hz and 197Hz are deep and must be caused by the room.

With the luxury of the dedicated listening room you got and with all the flexibility that gives you, I think you should read up on Acoustics Insider's "Bass Hunter Technique". Jesco (the man behind Acoustics Insider) has come up with this technique where he puts a single speaker in one of the front corners of the room, then he plays a track with good bass content, and while doing that he uses an office chair with wheels (which keeps his ears at the right listening height) and moves slowly in a line in the middle of the room back and forth from the front wall to the back wall. The idea here is to find the point in the room where the bass sound most even, and when finding that spot you have also found the best possible listening position in the room.

After that, it's time to find the best possible position for the loudspeakers and how big the equilateral listening triangle should be. If the phantom center sounds don't sound as distinct as if a physical center channel was used, the speakers are simply standing too far apart. Try to fine-tune the speaker's position, without moving the listening position, and do this until you think you have found the absolute best possible representation of the stereo image.

In general, I think most listeners set up their speakers too far apart than what's optimal. A smaller triangle will also give a higher ratio of direct sound vs reflected sound, and the room will therefore have a lesser impact on the perceived overall sound.

Oh... and by the way, you should have a look at the Acoustics Insider's Youtube channel, Jesco got a lot of good information on room acoustics "without the voodoo". :)
 

bo_knows

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I moved the speakers around with REW's room simulator and I did not see significant changes in that area... I really don't know how to boost this without EQ, which fortunately is far from the max excursion ranges of the woofer (as I wrote here).

Any ideas?
I think you know the answer. It goes something like this. Run the REW from MLP and record 20-250Hz with no smoothing. Once you record the peaks or dips, play those frequencies (one at a time), and with the SPL meter (or smartphone with the SPL app loaded) in your hand, walk around the room. Using your room diagram, write down the highest SPL for that particular frequency and its location. Once you are done with mapping your room, depending on the frequency, place the absorbers in that location. Repeat the measurements and process until you get it under control. If anyone else knows a better solution, please share it, I'm all ears.

P.S. See if you can make your bass traps mobile by placing them on some kind of platform with wheels.
This way you will be able to move/slide them away from the wall or to different locations without much effort. Also, try to "straddle" the corners with the trap panels, adding more space behind them will increase their efficiency. The ceiling cloud will help as well.

I'm making an assumption that you have basic tools and time to work on it. If this is not the case, please disregard it.
 

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