Old 03-07-2021, 12:53 AM   #1
Tubeguy
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Default Acoustic treatment increased my bass

I have placed 2m long corner strip on left and right walls where the wall meets the ceiling in attempt the clear up muddy low end. The foam goes from the back wall where monitors are and ends where I sit. To my surprise this not only tighten up the low end by about 50%, improved stereo image and made the sound more direct but also increased the bass and punch at around 60hz. If anything, I expected to have less bass since I figured out the foam will eat the bass up. I can actually hear kick on my NS10's :-). Any experiences like this?
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Old 03-07-2021, 02:20 AM   #2
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Perhaps you've been lucky enough to suppress a room mode (a resonance) that was causing a "bass hole" at your listening position.
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Old 03-07-2021, 09:22 AM   #3
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Bass traps CAN increase bass (as well as reduce the peaks/bumps) because they reduce the reflected bass which creates standing wave nodes (cancelation).

They smooth-out the bass both ways, making the bumps and dips smaller.

In fact killing the nodes and "increasing bass" is the most important thing they do... You can reduce a peak (antinode) with EQ but if you try to boost the dips/cancelation with EQ you need "infinitely big" amplifiers & woofers.
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Old 03-07-2021, 10:21 AM   #4
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Agree with Abraham L.
Another aspect of audio treatment often overlooked is reflections.
Not just controlling the mirror points, but also random or semi-random reflection treatments.

I have a cheap but effective AND practical system.
The rear wall in my studio has bookcases, cd cases and a number of other odd height/width storage solutions in place which also happen to break up reflections.
Worth thinking about.
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Old 03-07-2021, 10:02 PM   #5
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Quote:
Originally Posted by Abraham Liftin' View Post
"Foam" does almost nothing for treating bass
I have to disagree on that. I all ready have room treatment plus using the foam panels in strategic areas and it works well. This corner addition was more of a tune up. Off course If you use the cheap rubbish foam from fleebay than you get no results. Foam I have is the proper stuff with rubbery feeling to it, not light. When I talk to it it's like talking to a black hole, no reflection across the range that I can hear.
But I'll go with DVDdoug's idea of the cancellation. I never thought of that but it makes sense. The corner possibly reflected the bass directly back to the speaker canceling it. But I have way to measure it so it's just my guess and what my ears tell me.
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Old 03-08-2021, 06:45 AM   #6
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Quote:
Originally Posted by Abraham Liftin' View Post
Foam does not affect frequencies under about 160hz (Don't quote me on that exact frequency). That includes so-called "Acoustic foam" (LOL!)Do some research and pull up some actual scientific evidence. Bass traps and "foam" do not belong in the same sentence because "foam" does not affect bass frequencies. You heard it yourself and you still don't want to believe it.
This will depend on the depth (and flow resistivity) of the material. There's nothing that prohibits (apart from cost) making broadband absorbers from (polymer) foams.

50mm of any absorbent material won't do anything for low frequencies. But 500mm can.
That said, you'll find it difficult (impossible?) to find an "acoustic foam" with the lower resistivity you'd typically want for a very deep absorber. You're always going to be better off with something fibrous.

Although, you can do clever stuff with a couple of layers (of foam) separated by air gaps. But you're looking at deep assemblies. Like 1000mm deep
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Old 03-11-2021, 05:39 AM   #7
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Quote:
Originally Posted by Abraham Liftin' View Post
Your false perception that your bass increased is simply because you killed high's and high mids.
You have a point here with the loss of HF. I can see that happening. But I don't hear any loss, if anything, it's clearer. But what ever the foam did, it worked out well. Probably just by a lucky accident since I have no way of measuring it. I do have shelves on those walls as well, maybe they reflected to those corners and created mud. I just wanted to know some opinions.
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Old 03-11-2021, 06:21 AM   #8
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Old 03-11-2021, 06:34 AM   #9
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Quote:
Originally Posted by domzy View Post
Soundproofing is not room acoustics (and the improvement thereof).
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Old 03-11-2021, 06:50 AM   #10
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Quote:
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Soundproofing is not room acoustics (and the improvement thereof).
that's true, apologies for going off-piste
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Old 03-11-2021, 08:36 PM   #11
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Quote:
Originally Posted by Abraham Liftin' View Post
Foam does not affect frequencies under about 160hz (Don't quote me on that exact frequency). That includes so-called "Acoustic foam" (LOL!)Do some research and pull up some actual scientific evidence. Bass traps and "foam" do not belong in the same sentence because "foam" does not affect bass frequencies.
If it's what I think you're talking about Abraham, I agree with you. Perhaps you could show a picture of the foam you're talking about. It certainly has some affect on the upper frequencies but less on the bottom end. That's from the studies I've read not from experience. I personally used 701 fiberglass for all my acoustic applications.
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Old 03-12-2021, 06:52 AM   #12
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Flow resistivity for "acoustic foams" might be around 10k ... 20k Pa.s/m3
You can hunt this kind of info, but if the vendor isn't supplying it for their product, you have to wonder how serious they are about acoustics.

(this is in the same area as the middling density rockwool products)

If you plug this number (and the thickness) into a calculator
like this one

You'll get an idea of what you might expect.

Note that simply adding more thickness doesn't help unless the flow resistivity is fairly low.

i.e once you've got (say) 100mm of a typical foam (or a dense-ish rockwool), you don't get a lot more absorption at LF by adding more depth. Although you can by adding an air gap behind the absorber. Or alternating absorber/airgap layers.

100mm of 301 fibre glass (14k Pa.s/m3) will be rolling off by 300Hz & won't be doing much at 100Hz

Porous absorbers that go low - with significant absorbtion at 100Hz - will usually be deep (>500mm) and filled with stuff with lower resistivity (<4000 Pa.s/m3)

There's a nice table here

Of course, all these broadband porous absorbers will absorb high and mid frequencies really well. So that's something to think about.
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