I have an extreme null at about 95hz, and peaks around 52hz and 130hz. (See attached photo)
front and back walls completely covered with 1" pyramid and wedge foam. And small 4" corners in at the back corners.
2" wedges on ceiling above of my sitting position, about 6'x4' area.
I will be working in this room for a few years to come, so I'm willing to spend money on whatever sound diffusion/bass absorbers needed.
What kind of absorbing/diffusion material will help to smooth this out? What modifications can I do inside the room?
(sketch of a room attached)
How to smooth out extreme nulls & peaks ?
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ts-12
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- Joined: Fri Sep 26, 2008 1:47 am
- Location: Western Massachusetts USA
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Soundman2020
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Re: How to smooth out extreme nulls & peaks ?
Hi "ts-12", and welcome.
Please check the forum rules for posting: you seem to be missing something important!
Several comments:
1) You didn't provide enough information to give you a full answer: For example, you didn't say how high the ceiling is, what the walls, floor and ceiling are made of, what the closet is made of (doors, shelves, contents, etc), what type of speakers and mic you are using, etc. Please try to give more details, and also post some photos of what you have right now. The more you tell us, the better the answers will be.
But based on the little you did say:
2)
3) Your speaker geometry and setup is not optimal. There are several things I would change there: First, get the speakers off the desk and onto massive stands (VERY heavy ones) behind the desk, right up against the wall, and adjust the roll-off control to -6 dB. The reason for that is simple: You very likely have resonance and reflection issues going on there. Then, adjust your seating position so that your head is the same distance from the speakers as the speakers are from each other. So if the speakers are 4 feet apart, then your head should be in the middle, 4 feet from each speaker: Also, ensure that the speakers are both aimed at a point a few inches BEHIND your head, not aimed AT your head.
4) Your testing level was too low: you should run the tests at about 85 dB, which is the standard level, in order to make sure that you are exciting all of the room modes.
5) The room is square! Almost the worst possible shape. The first order mode for 11 feet is exactly 51.4 Hz, but since two of your room dimensions are both the same, that mode is multiplied, and increases by 6 dB. Your first two axial modes (0,1,0 and 0,0,1) both line up perfectly at 51.4 Hz.
And that big dip at around 90 Hz is very likely the pair of 1,1,0 and 1,0,1 tangential modes, which both fall exactly at 87.3 Hz.
Many other of those dips and peaks are most likely also related to modal issues.
Is there any chance you can move one of those walls? Even a couple of inches would make a difference.
You cannot eliminate modes: they are a function of the room dimensions. All you can do is damp them and treat them. Small rooms need a LOT of damping, much more than what you have right now: I'd try to put floor-to-ceiling superchunks in all four vertical corners, and also the horizontal corner (wall/ceiling) above the couch. Make them all as wide as possible, at least 24" across the front faces, more if you can. You might need to move the couch (or get a smaller couch) to fit those in.
I'd also put thick absorption on the rear wall, at least 4", for the entire section above the couch. I'd also put insulation on the front walls, behind the speakers, and at your first reflection points on the side walls. You already have some on your ceiling, but 2" isn't enough. I'd make that 4".
And forget the foam: If you didn't get it from a reputable acoustics company with published independent lab test data on how it performs, then it is useless. And if you DID get it from such a place, then it was expensive! Just buy ordinary home insulation, either fiberglass or mineral wool. The best stuff is OC-703, but there are plenty of good alternatives.
So I'd start by doing all that, then test the room again with the mic in the EXACT SAME POSITION, not even off by 1/2", and see how much effect it had. Based on that, we can figure out the next round of treatment.
- Stuart -
Please check the forum rules for posting: you seem to be missing something important!
Several comments:
1) You didn't provide enough information to give you a full answer: For example, you didn't say how high the ceiling is, what the walls, floor and ceiling are made of, what the closet is made of (doors, shelves, contents, etc), what type of speakers and mic you are using, etc. Please try to give more details, and also post some photos of what you have right now. The more you tell us, the better the answers will be.
But based on the little you did say:
2)
The room is too small to be able to use most types of diffuser. Those only have valid uses in much larger rooms. So your options are basically limited to absorptive and resonant devices. For that size room, I'd go with a LOT more absorption.I'm willing to spend money on whatever sound diffusion/bass absorbers needed
3) Your speaker geometry and setup is not optimal. There are several things I would change there: First, get the speakers off the desk and onto massive stands (VERY heavy ones) behind the desk, right up against the wall, and adjust the roll-off control to -6 dB. The reason for that is simple: You very likely have resonance and reflection issues going on there. Then, adjust your seating position so that your head is the same distance from the speakers as the speakers are from each other. So if the speakers are 4 feet apart, then your head should be in the middle, 4 feet from each speaker: Also, ensure that the speakers are both aimed at a point a few inches BEHIND your head, not aimed AT your head.
4) Your testing level was too low: you should run the tests at about 85 dB, which is the standard level, in order to make sure that you are exciting all of the room modes.
5) The room is square! Almost the worst possible shape. The first order mode for 11 feet is exactly 51.4 Hz, but since two of your room dimensions are both the same, that mode is multiplied, and increases by 6 dB. Your first two axial modes (0,1,0 and 0,0,1) both line up perfectly at 51.4 Hz.
And that big dip at around 90 Hz is very likely the pair of 1,1,0 and 1,0,1 tangential modes, which both fall exactly at 87.3 Hz.
Many other of those dips and peaks are most likely also related to modal issues.
Is there any chance you can move one of those walls? Even a couple of inches would make a difference.
You cannot eliminate modes: they are a function of the room dimensions. All you can do is damp them and treat them. Small rooms need a LOT of damping, much more than what you have right now: I'd try to put floor-to-ceiling superchunks in all four vertical corners, and also the horizontal corner (wall/ceiling) above the couch. Make them all as wide as possible, at least 24" across the front faces, more if you can. You might need to move the couch (or get a smaller couch) to fit those in.
I'd also put thick absorption on the rear wall, at least 4", for the entire section above the couch. I'd also put insulation on the front walls, behind the speakers, and at your first reflection points on the side walls. You already have some on your ceiling, but 2" isn't enough. I'd make that 4".
And forget the foam: If you didn't get it from a reputable acoustics company with published independent lab test data on how it performs, then it is useless. And if you DID get it from such a place, then it was expensive! Just buy ordinary home insulation, either fiberglass or mineral wool. The best stuff is OC-703, but there are plenty of good alternatives.
So I'd start by doing all that, then test the room again with the mic in the EXACT SAME POSITION, not even off by 1/2", and see how much effect it had. Based on that, we can figure out the next round of treatment.
- Stuart -