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Are my bass traps reasonable or am i doing something wrong?

caught gesture

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So you also agree in disassembling them, so they are fully "open" without any wood at all? ;)
Asking because its a heck of work. No idea how many screws i used, but it was a lot.
You don’t need to remove the wood from all sides, just the sides facing the room.
 

Geert

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Unfortunately i am somehow not able to get 20..200hz in the RT60 Decay. But what i can do, i upload the measurement file. maybe someone with REW is able to tell me, if the bass traps do something "good" to the decay.

sidenote: i changed the volume level a little bit during these measurements as they took couple of hours and i was watching a movie between them. but i guess that does not change anything in the decay
Before.jpg

After.jpg

RT30.jpg


Major resonance at 22Hz.
 
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slacki

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Major resonance at 22Hz.
Ok but this has nothing to do with the wood, right? When i interpret that correctly, this is in both diagrams, with wood and without.
 

Geert

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Ok but this has nothing to do with the wood, right? When i interpret that correctly, this is in both diagrams, with wood and without.

Indeed, it's just something that's very obvious now that you have the waterfalls.
 

goat76

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The 22Hz problem is probably not anything to be concerned about, it will get triggered in the measurement but not that much by normal music signals.
 

Holmz

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Yep to a small degree. What they do is reduce reflectivity of hard surfaces. Floors, tables, walls, glass, certain furniture like leather couches. Tossing rugs on the floor right in front of the subs will help, big fluffy pillows in Corners and throw blankets over reflective furnishings. All little improvements that can add up and help make the room less reactive to sound bounce.


I thought that we were talking about a bass trap, and bass, or at least that is in the title.
While agree that a rug, curtains, and plants absorbe and scatter sound in the higher frequencies… those things are not known to be good at bass trapping.

Secondly the pressure zone is against the surfaces of the room, like walls, ceiling or floor.
The zone where velocity absorbers work are well away from the boundary condition where the velocity, by definition must be zero.

A rug is in the pressure zone, and it is truely not intruding upon the velocity region when it on the orderr of a centimetre think, and the wavelength is 10-25, long.

I agree blanket or a pillow is thicker, and will start to actually work in the upper bass. Especially if it a bit off the wall like on a bookself or curtain rod.


I have never seen plots of RT60 of room with and without a rug, and noted seeing subwoofer freqs shorten.
The physics are against it in the subwoofer region where the OP is working.

I believe that we are doing a disservice to suggest to the OP to use a rug for subwoofer bass.
But a rug is a good idea in general… just not as main treatment for sub freqs. (IME).
 
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Holmz

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The 22Hz problem is probably not anything to be concerned about, it will get triggered in the measurement but not that much by normal music signals.

^In general yeah^… but if it was triggered often by music or HT, then maybe it would be worthwhile to go after that one mode with a pressure trap, like a tympanic membrane style?

I can picturing the OP playing movies with a strong bass as they mentioned a Marantz HT unit in the first post.
I don’t know if it is getting trigger, but it seems possible.

I thought there was some rating of bass in movies? Or some quantified lower freq that was in the content??
 

goat76

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^In general yeah^… but if it was triggered often by music or HT, then maybe it would be worthwhile to go after that one mode with a pressure trap, like a tympanic membrane style?

I can picturing the OP playing movies with a strong bass as they mentioned a Marantz HT unit in the first post.
I don’t know if it is getting trigger, but it seems possible.

I thought there was some rating of bass in movies? Or some quantified lower freq that was in the content??

Yes, some kind of tuned bass traps could be used, but I have never seen a commercially available bass trap tuned that low.
In that low-bass region, I think most people would be as happy taming that with EQ.

It would have been interesting to see how the bass energy is for movies in general. Do they high-pass the soundtracks just like they do for music, or do they generally leave it flat for the LFE channel?

For most releases of music, it usually looks like in the "Normalized average spectrum" graph in the picture below, with a steep high-pass filter somewhere between 30Hz to 50Hz. So if music listening is the main thing, I think the frequency region under 50Hz is the last thing to be bothering about.

The_Wall_Hey_You.gif
 

FeddyLost

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^In general yeah^… but if it was triggered often by music or HT, then maybe it would be worthwhile to go after that one mode with a pressure trap, like a tympanic membrane style?
I'd notch it out with EQ if this is a REAL problem.
Pressure trap tuned to 22 Hz or Helmholtz trap would be extremely big to work well and such frequency is not a problem at home usually unless LP is near the wall.
I doubt if any home user will notice some elevated decay time at 22 Hz when the peak is flattened with EQ.
 
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slacki

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i have now my marantz cinema 50 and i am somehow quiet unhappy with my home cinema now. i dont know why but ... it feels like there is much wrong - in general.
it should be an auro 3d setup, but the angles are wrong (e.g. FHL and FHR have ~17°). So i am wondering now if i should "start from scratch" and do some more things to improve the situation. first i would remove the wood from the traps and do some measurement, if the wood help in any way. maybe i should start a new thread, especially with the height speakers, because i have no idea how to mount them to get a 30° angle. anyway, just to have something to start with: should i measure, then remove the wood and only have the isobond in the corners, measure again, and see if it does something? my noob guess is, there will be no difference. if there is no difference, i could easily test what happens when i remove them at all (its only some light foamed material). then i could start with the next part (speaker location/angle)
 

Holmz

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i have now my marantz cinema 50 and i am somehow quiet unhappy with my home cinema now. i dont know why but ... it feels like there is much wrong - in general.
if there was a speaker out of phase it could be a problem.

it should be an auro 3d setup, but the angles are wrong (e.g. FHL and FHR have ~17°). So i am wondering now if i should "start from scratch" and do some more things to improve the situation. first i would remove the wood from the traps and do some measurement, if the wood help in any way. maybe i should start a new thread, especially with the height speakers, because i have no idea how to mount them to get a 30° angle. anyway, just to have something to start with: should i measure, then remove the wood and only have the isobond in the corners, measure again, and see if it does something? my noob guess is, there will be no difference. if there is no difference, i could easily test what happens when i remove them at all (its only some light foamed material). then i could start with the next part (speaker location/angle)
Dunno, but some measurements as the treatments go in make sense.
Sort of an iterative approach…

I'd notch it out with EQ if this is a REAL problem.
Pressure trap tuned to 22 Hz or Helmholtz trap would be extremely big to work well and such frequency is not a problem at home usually unless LP is near the wall.
I doubt if any home user will notice some elevated decay time at 22 Hz when the peak is flattened with EQ.

Yeah... it doesn’t fix the cause, but it acts like it fixes it enough… so I agree.
 

goat76

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i have now my marantz cinema 50 and i am somehow quiet unhappy with my home cinema now. i dont know why but ... it feels like there is much wrong - in general.
it should be an auro 3d setup, but the angles are wrong (e.g. FHL and FHR have ~17°). So i am wondering now if i should "start from scratch" and do some more things to improve the situation. first i would remove the wood from the traps and do some measurement, if the wood help in any way. maybe i should start a new thread, especially with the height speakers, because i have no idea how to mount them to get a 30° angle. anyway, just to have something to start with: should i measure, then remove the wood and only have the isobond in the corners, measure again, and see if it does something? my noob guess is, there will be no difference. if there is no difference, i could easily test what happens when i remove them at all (its only some light foamed material). then i could start with the next part (speaker location/angle)

The speakers and the listening position are the first steps to getting right. After that, you should deal with the room's acoustics because many of the acoustic problems will be dependent on where the speakers are placed, and which of those reaches your ears at the listening position. The remaining problems that you find hard to solve can be dealt with by applying EQ as a last-step resort.

In the end, it's all about a series of compromises. You find the least compromising speaker and listening positions, you try to solve the room problem by fixing the room's acoustics to the extent that it doesn't compromise other things (like using the room for things besides being a listening room).
EQ the rest. :)
 

AdamG247

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This time let’s please try to focus on my questioning the ideas, so as that I can avoid attracting a ban.


I thought that we were talking about a bass trap, and bass, or at least that is in the title.
While agree that a rug, curtains, and plants absorbe and scatter sound in the higher frequencies… those things are not known to be good at bass trapping.

Secondly the pressure zone is against the surfaces of the room, like walls, ceiling or floor.
The zone where velocity absorbers work are well away from the boundary condition where the velocity, by definition must be zero.

A rug is in the pressure zone, and it is truely not intruding upon the velocity region when it on the orderr of a centimetre think, and the wavelength is 10-25, long.

I agree blanket or a pillow is thicker, and will start to actually work in the upper bass. Especially if it a bit off the wall like on a bookself or curtain rod.


I have never seen plots of RT60 of room with and without a rug, and noted seeing subwoofer freqs shorten.
The physics are against it in the subwoofer region where the OP is working.

I believe that we are doing a disservice to suggest to the OP to use a rug for subwoofer bass.
But a rug is a good idea in general… just not as main treatment for sub freqs. (IME).
We are now in agreement. I did say “to a small degree”. I got this thought process directly from Dr. Toole’s books. If you do a word/phrase search on any of his book versions you will get a dozen or so hit where he discusses how Curtains, Rugs and pillows and absorbent furniture can help tame room modes and decrease the amount of reflective energy. This taming then has a small effect on improving the quality of the bass in the room. Less muddy…Was my comment not completely clear? Sure, I give you that. We type out our thoughts and sometimes it makes sense in our heads but not to the reader. But I did say to a small degree and looking at his room. Seeing all the hard reflective surfaces I came away thinking every frequency probably sounds harsh and muddy. Cleaning up that reflective mess can help to improve the overall quality of sound in the room and clean up the higher bass frequencies can have a ripple effect. At least this was my take away from reading Dr. Toole’s book on Room Acoustics. Perhaps we are just talking past each other.

In some cases, and I felt this to be one of those instances. Too many people start giving advise at the same time making it more complicated for the OP to absorb it all. So, I stepped away from the conversation so as not to add more confusion. My job is to mostly stay out of the way of our Members and I felt I was getting in the way and not advancing the conversation.
 

Holmz

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We are now in agreement. I did say “to a small degree”. I got this thought process directly from Dr. Toole’s books. If you do a word/phrase search on any of his book versions you will get a dozen or so hit where he discusses how Curtains, Rugs and pillows and absorbent furniture can help tame room modes and decrease the amount of reflective energy. This taming then has a small effect on improving the quality of the bass in the room. Less muddy…Was my comment not completely clear? Sure, I give you that. We type out our thoughts and sometimes it makes sense in our heads but not to the reader. But I did say to a small degree and looking at his room. Seeing all the hard reflective surfaces I came away thinking every frequency probably sounds harsh and muddy. Cleaning up that reflective mess can help to improve the overall quality of sound in the room and clean up the higher bass frequencies can have a ripple effect. At least this was my take away from reading Dr. Toole’s book on Room Acoustics. Perhaps we are just talking past each other.

In some cases, and I felt this to be one of those instances. Too many people start giving advise at the same time making it more complicated for the OP to absorb it all. So, I stepped away from the conversation so as not to add more confusion. My job is to mostly stay out of the way of our Members and I felt I was getting in the way and not advancing the conversation.

^totally agree^
 
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slacki

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trapcram.jpg

so when the traps are now open, i have a drop in 70 and 85hz - guess i could get rid of them with a second sub?
now i can easily transport the foam myself. i will measure (maybe later or tomorrow) how it is without them at all
 
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slacki

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i was too excited to measure again, so i did the measurement now without traps, everything else is identical. please ignore the label, forgot to rename it ;)
so i think i could even remove the traps, sell the arendal sub, buy 2 new identical subwoofer and be happy?

Bildschirmfoto_2022-12-01_12-31-22.png
 

goat76

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What does the change look like in the time domain? Maybe you can post pictures of the Waterfall graphs, with and without the traps.
 
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slacki

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i have no idea how to get those data :/
attached are all 3 measurements

sorry, uploaded the wrong file, the new one has close to 200kb
with traps closed = traps in wood
traps open = traps without the wood
no traps at all - should be self explaining :)
 

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