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Post by mtl777 on Sept 18, 2022 20:39:56 GMT
Hey guys, I have a very small home studio (7.5'L x 15'W x 8'H). Due to furniture and gear placement considerations in this limited space, I am forced to use the 15'W side as the front wall where my monitors are placed, and so, I only have 7.5' distance from front wall to back wall. I am upgrading my monitors and have placed an order for the Tyler Acoustics T1. This monitor has a passive radiator on the back, so it needs to be distanced at least 1' away from the wall to avoid it coupling with the wall (bass frequencies 45 to 250 Hz would be enhanced the more it's placed closer to the wall). Unfortunately, the most I can have it placed is 7" away from the wall, so I'm thinking of putting an absorber behind each speaker to help reduce the coupling issues. Could someone please help me with suggestions on how to build a DIY absorber for this specific purpose? Please include choice of materials (OC 703 vs rock wool vs other materials), dimensions of the absorber that I should make (length, width, height, thickness), and placement of the absorber (how it should be placed on the wall whether flush or distanced from the wall). BTW the monitor itself is 16"H x 9"W x 12"D and its frequency range is 45 Hz to 20 KHz. With all these considerations, please keep in mind that I have only 7" distance to work with from the wall to the monitor. Thanks in advance for your much appreciated help!
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Post by rock on Sept 19, 2022 13:13:39 GMT
Sorry to say but clearly, your monitor choice is not consistent with your room and set up; if this is temporary, maybe your next room will be better suited for you new monitors but hopefully an absorber will solve your problem and all will be fine. I'll share my best guesses.
What I'm describing below is basically a standard LF porous absorber that will fit between your monitor and mounted flush to the wall:
Using 3" thick mineral wool or OC 703 doubled in thickness to 6" is probably the best you can do. Sandwich two pieces together to get 6", no glue (if you can purchase it 6" thick, go for it!). Use kraft paper, thin plastic or foil on the front lightly glued with spray glue. Cover with you choice of acoustically transparent, breathable fabric. Frame or no frame, your choice. Typical size is 2 feet by 4 feet and at that short distance (1 inch), a 2x4 panel should be enough. If you want overkill, you could enlarge the panel to 4x4 and add a surrounding thickness of another 6 or more inches. If you do this, you'll want to leave some airspace of about an inch on the sides. I'm really not sure if and inch is enough behind and on the sides but a thinner absorber will be less effective at lower freqs.
If you want to optimize this, you may need to try this idea using various thicknesses with corresponding distances for space from the speaker. If you're going to experiment, you don't need fabric or a frame
For this project, I would certainly make before and after acoustic measurements especially if you're going to experiment with different thicknesses etc. For starters, measure 2 foot, 1 foot and 7" from the wall without an absorber just to confirm mfg. specs and to get a baseline.
Let us know how it goes!
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Post by mtl777 on Sept 19, 2022 19:47:10 GMT
Using 3" thick mineral wool or OC 703 doubled in thickness to 6" is probably the best you can do. Sandwich two pieces together to get 6", no glue (if you can purchase it 6" thick, go for it!). Use kraft paper, thin plastic or foil on the front lightly glued with spray glue. Cover with you choice of acoustically transparent, breathable fabric. Frame or no frame, your choice. Typical size is 2 feet by 4 feet and at that short distance (1 inch), a 2x4 panel should be enough.
Thank you so much, Rock!
Just to be sure I got you correctly, please see the image. The absorber is 6" thick, 1" away from the back of the monitor, and flush to the wall. Is that correct?
I'd like to know what the distance from top of the monitor to top of the absorber should be (shown as Y = ? in the image).
If I use OC 703-FRK (three 2" thick panels to make 6"), I would have the FRK foil layer three times, the first on the front, the second 2" from the front, and the third 4" from the front. Would this still be ideal or should I have one foil layer on the front only?
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Post by rock on Sept 19, 2022 20:31:24 GMT
Hi mtl,
First I should warn you that I have never tried this with a speaker like yours so I really can't say how well it will work at all. I'm just using the info I've learned here about passive absorbers. My lack of hands on experience with a situation like yours makes me suggest that you take acoustic measurements with software like REW to determine how well it improves your speaker response.
That said, I'm really wondering if this is a good idea at all so you really need to see how close you can have the PR to your absorber without affecting the system response. But yes, I suggested a 1" space between the absorber and the PR... BUT I do want you to measure (with REW) at other distances to verify your response. The reason I suggested 1" is because you "gave me" a total of 7" to work with. I'm suggesting a 6" absorber for best LF performance if we can "get away with" as little a 1 inch space but IDK, 1" might not be enough! Maybe it's more like a 5" absorber with a 2" space...IDK.
My best guess is to center the absorber on the passive radiator.
My understanding is to use one membrane (foil) on the front.
Remember to measure. AFAIC, you're in uncharted territory. If you have not purchased your speaker yet, there's probably a better choice. Maybe someone here will have a better idea. If not, try other forums or better yet contact your speaker mfg. and see what they say about all this.
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Post by mtl777 on Sept 20, 2022 0:06:32 GMT
First I should warn you that I have never tried this with a speaker like yours so I really can't say how well it will work at all. I'm just using the info I've learned here about passive absorbers. My lack of hands on experience with a situation like yours makes me suggest that you take acoustic measurements with software like REW to determine how well it improves your speaker response. That said, I'm really wondering if this is a good idea at all so you really need to see how close you can have the PR to your absorber without affecting the system response. But yes, I suggested a 1" space between the absorber and the PR... BUT I do want you to measure (with REW) at other distances to verify your response. The reason I suggested 1" is because you "gave me" a total of 7" to work with. I'm suggesting a 6" absorber for best LF performance if we can "get away with" as little a 1 inch space but IDK, 1" might not be enough! Maybe it's more like a 5" absorber with a 2" space...IDK. My best guess is to center the absorber on the passive radiator. My understanding is to use one membrane (foil) on the front. Remember to measure. AFAIC, you're in uncharted territory. If you have not purchased your speaker yet, there's probably a better choice. Maybe someone here will have a better idea. If not, try other forums or better yet contact your speaker mfg. and see what they say about all this.
That's OK. Thank you so much, and I really appreciate your help even if you're not sure if it's a good idea. At the very least, I already have an idea of what solutions to try. And I will follow your advice on making measurements with REW.
I called the designer of the monitor and told him about my situation. His recommendation was the same as yours -- 2' x 4' x 6" absorber 1" away from back of monitor! He would have preferred 2" away but given my limitations, 1" away is the best I could do.
I have already purchased the monitor and it has already shipped. What is wrong with it for my room? Is it too big for my room?
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Post by rock on Sept 21, 2022 12:52:41 GMT
Great! I'm glad you got info from the designer so it confirms you're on the right path. In general, I don't think any given speaker is necessarily wrong for any given room but there are practical limits like the actual size and optimum positioning requirements like in your case. You could fit Klipsch Corner Horns in your room but there might not be much room for anything else (ha ha , not really but you get the idea).
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Post by Ethan Winer on Sept 21, 2022 16:54:39 GMT
If I use OC 703-FRK (three 2" thick panels to make 6"), I would have the FRK foil layer three times, the first on the front, the second 2" from the front, and the third 4" from the front. It's important to remove the FRK facing from all but the one layer that faces the room. Or use FRK for that layer and plain 703 for the other two closer to the wall.
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Post by mtl777 on Sept 21, 2022 17:37:30 GMT
If I use OC 703-FRK (three 2" thick panels to make 6"), I would have the FRK foil layer three times, the first on the front, the second 2" from the front, and the third 4" from the front. It's important to remove the FRK facing from all but the one layer that faces the room. Or use FRK for that layer and plain 703 for the other two closer to the wall.
Thank you so much, Ethan! Will do.
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Post by mtl777 on Sept 26, 2022 1:11:07 GMT
I did more research on the available insulation products to make bass traps and came up with an Excel worksheet to compare them.
The designer of the monitor said that the bass frequencies at the back of the monitor that I need to treat are centered at about 38 Hz. Looking at the data in my Excel worksheet, I find that 125 Hz is the lowest frequency nearest to 38 Hz for which sound absorption coefficient information is available. So I decided to use 125 Hz as my primary consideration for finding the best insulation product for my needs. The next higher frequency in the worksheet, 250 Hz, is still a low frequency and is my secondary consideration but it's not half as important as 125 Hz. And I don't care at all about the higher frequencies 500 to 4000 Hz in the worksheet.
Using 125 Hz as my guide, and looking for different thicknesses that I could combine to make a 6"-thick absorber, I find that the best product for my needs is the 3"-thick Roxul Rockboard 60 which has an absorption coefficient of 0.78 at 125 Hz. I'm thinking that two panels of this (to make 6") plus a thin plastic membrane on the front should give me the best DIY bass trap I could make out of the different insulation product options available.
Please let me know if you agree that I'm making the right choice for this, or please comment if you think there is a better choice and why.
Thanks!
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Post by Ethan Winer on Sept 26, 2022 17:53:34 GMT
Yes, that will be excellent.
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Post by mtl777 on Sept 27, 2022 7:07:40 GMT
Yes, that will be excellent.
Thank you, Ethan!
I posted this same question in the GearSpace forum and Andre Vare (user name Avare) replied that I would be better off with the Safe N Sound 6" which has good absorption of 1.11 at 125 Hz. He said the problem with doubling the Rockboard 60 is, and I quote, "You double the thickness, and you double the resistance. The Rockboard 60 reflects low frequencies internally."
What I'm getting from Andre's statement is that the absorption is not as good at 125 Hz for a 3" thick that is doubled vs a 6" thick of the same material because doubling the thickness doubles the resistance, so the absorption of the doubled 3" would be less than that of the 6".
But when I compare, for an apples-to-apples comparison, the 3" Rockboard 60 (0.78 at 125 Hz) vs the 3" Safe N Sound (only 0.52 at 125 Hz), I'm wondering if doubling the 3" Rockboard 60 which has much better coefficient than 3" Safe N Sound at 125 Hz will really end up with a lesser coefficient than the 6" Safe N Sound. I have no data to see this and neither has Andre. Is he just speaking from experience? What is your take on this?
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Post by Hexspa on Sept 27, 2022 8:15:49 GMT
Gearspace loves safe n sound. The way I learned here was that rigid can go up to 8" before reflectiveness becomes a problem. If you want thicker, typically you'd use fluffy but a good middle ground seems to be safe n sound. This semi-rigid material would probably also reflect at the very lowest frequencies and fluffy isn't as effective at low frequencies when, say, 4" thick like you'd typically use with rigid.
Maybe Avare has a more detailed analysis. You can ask what is the reflectiveness difference between safe n sound and rockboard 60 between 50-80Hz per thickness. I'll guess that with greater than 8" rigid, you might reflect from 32Hz (one octave down) but that it's negligible with 8" or less.
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Post by mtl777 on Sept 27, 2022 16:59:18 GMT
Gearspace loves safe n sound. The way I learned here was that rigid can go up to 8" before reflectiveness becomes a problem. If you want thicker, typically you'd use fluffy but a good middle ground seems to be safe n sound. This semi-rigid material would probably also reflect at the very lowest frequencies and fluffy isn't as effective at low frequencies when, say, 4" thick like you'd typically use with rigid. Maybe Avare has a more detailed analysis. You can ask what is the reflectiveness difference between safe n sound and rockboard 60 between 50-80Hz per thickness. I'll guess that with greater than 8" rigid, you might reflect from 32Hz (one octave down) but that it's negligible with 8" or less. Thank you! So for my 6" bass trap I don't have to worry about reflectivity?
An important question I've been wondering about is:
At 125 Hz, is the sound absorption coefficient of a 6" Safe N Sound the same as the sound absorption coefficient of a doubled 3" Safe N Sound?
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Post by Ethan Winer on Sept 27, 2022 17:16:43 GMT
In all honesty, I'd go by what Andre says. I know that 6-inches of ANY rigid insulation does a great job. But Andre follows the details more closely than I do. So do whatever he says. I am serious.
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Post by mtl777 on Sept 27, 2022 17:42:36 GMT
In all honesty, I'd go by what Andre says. I know that 6-inches of ANY rigid insulation does a great job. But Andre follows the details more closely than I do. So do whatever he says. I am serious.
So then I should shift my apples-to-apples comparison to the 6" absorbers only, and for that I find that OC Thermafiber Fire and Sound with absorption coefficient of 1.37 at 125 Hz is better than Safe N Sound with absorption coefficient of 1.11 at 125 Hz. Should I still follow Andre? I just want to be careful and get as much viewpoints as I can from other experts before deciding.
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