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EVA foam for performance speaker enclosures
EVA foam for performance speaker enclosures
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Old Yesterday, 02:43 PM   #361
jeshi is offline jeshi  Japan
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Originally Posted by ewollowe View Post
Jeshi how effective do you think a sheet of eva would be between two drivers in a bipole design vs say just a thick wad of pillow stuffing (what I currently have in place)?
Are the two drivers attached to each other by the back side, or are they supported on each end by a front baffle? I would imagine that pillow stuffing has no structural support and is just acting as internal sound dampening.

If you want to physically have the dipole drivers touching each other and want a material to absorb vibration but also provide support then EVA is maybe the best. If you just want a dampening material, then maybe neoprene foam would be just as good. But neoprene foam is floppy and can not provide any structural shape.
If you want a sound absorbing layer to isolate the two dipole speakers from each other, then yes I think EVA (even the cheap floor panel type) would work nicely. You can pick up the cheap floor panel EVA at almost any store from Walmart to Target to HomeDepot type places (not sure what the Australian equivalent is), probably for $7-10 a pack. If you also find some neoprene, maybe from a well stocked fabric store, then a sandwich of EVA/neoprene/EVA would make an excellent sound isolation layer. Maybe like this from amazon.com.au 4 Tiles EVA Fitness Home Yoga Gym Interlocking Rubber Floor Puzzle Mat for Protection Portable Durable Lightweight- Black: Amazon.com.au: Sports, Fitness & Outdoors

The EVA seems to work best when used as structural material (front baffle for mounting drivers, enclosure walls, open baffle side panels) where the material will need to absorb vibrations and/or provide sound absorption (like front baffle reflection absorption)

Last edited by jeshi; Yesterday at 02:54 PM.
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Old Yesterday, 02:58 PM   #362
ewollowe is offline ewollowe  Australia
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Hi Jeshi,

They're currently mounted in a polystyrene foam box, initial results have been promising. I'm thinking of mechanically coupling them together with some wooden rod but with the eva between them as a way to clean up the sound but my concern was that the eva would be an inferior absorber of high frequencies vs traditional stuffing. I'm not looking to use eva for structural reinforcement just as an absorber.
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Old Yesterday, 03:24 PM   #363
jeshi is offline jeshi  Japan
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Quote:
Originally Posted by ewollowe View Post
Hi Jeshi,

They're currently mounted in a polystyrene foam box, initial results have been promising. I'm thinking of mechanically coupling them together with some wooden rod but with the eva between them as a way to clean up the sound but my concern was that the eva would be an inferior absorber of high frequencies vs traditional stuffing. I'm not looking to use eva for structural reinforcement just as an absorber.
Well have a look at some of the tests I did like some Panel resonance tests: here

Panel transmission tests: here
Click the image to open in full size.
Click the image to open in full size.

I think EVA absorbs sound (sound barrier, panel leakage) as good or better than neoprene especially in high frequencies. And I think neoprene is considered similar to felt for lining the walls of speakers for sound absorption. Look at the 10mmEVA+4mm neoprene, it has a -35db suppression of transmitted frequencies from 7khz and up. Even a simple 10mm EVA alone give -25db to -30db suppresion from 7khz up

I think for your application, you don't need the high-spec EVA that Mattes and I are using for structural support, so you can try the cheaper lower density EVA floor panel foam like I linked for $20au. It is cheap enough that it might be worth trying to experiment with it.

Last edited by jeshi; Yesterday at 03:46 PM.
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Old Today, 01:10 AM   #364
ewollowe is offline ewollowe  Australia
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Thanks for your input jeshi.

I have another question, this may be already answered in this thread? How porous is EVA? Does it have the same effect as polyester stuffing in an enclosure of increasing the perceived internal volume from the drivers point of view?
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Old Today, 01:48 AM   #365
jeshi is offline jeshi  Japan
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Originally Posted by ewollowe View Post
Thanks for your input jeshi.

I have another question, this may be already answered in this thread? How porous is EVA? Does it have the same effect as polyester stuffing in an enclosure of increasing the perceived internal volume from the drivers point of view?
No it's the opposite, it will decrease the internal volume. It's a closed cell foam so non-porous and it will decrease the internal volume in the same way as adding MDF supports would. It is also water proof and air tight, so nothing physical gets through. You can think of the EVA foam like a foam version of MDF+bitumen+felt (the sound transmission blocking of MDF, the vibration dampening of bitumen, and the sound reflection/absorption of felt) with different efficiencies/characteristics at these measures. MDF is good at blocking sound (prevent leakage) but resonates and is reflective. Bitumen is good for vibration dampening but floppy so so can't be used as support and is also highly reflective. Felt is floppy and not good at vibration dampening, but excellent at absorbing sound reflections. So EVA is like combining the best of the MDF+bitumen+felt sandwich with a single material. But I still stuff my EVA sealed speaker enclosures with fill (usually I use a loose wool). But for open baffles, I can use the raw EVA and not need to do anything else.

If you want to create an isolation wall between your dipole drivers (what would normally be an MDF panel, covered in bitumen and felt) to create two sealed boxes, then I would say EVA could be a great replacement with better vibration dampening than the MDF+bitumen+felt. But for a poly-fill replacement, then I would say no, don't bother with the EVA. But if you said you wanted to use wood to internally support the drivers. That would be an excellent use for EVA (not wood) since it would provide support and excellent vibration dampening (better than wood)

If you ever had flipflop sandals or Crocs then you have probably seen EVA foam.

cheers
jeshi

Last edited by jeshi; Today at 02:07 AM.
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Old Today, 02:05 AM   #366
ewollowe is offline ewollowe  Australia
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I live in Australia Jeshi, flip flops are a way of life over here

Thanks for the excellent explanation.
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Old Today, 02:22 AM   #367
jeshi is offline jeshi  Japan
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Maybe this will help explain what EVA foam is. It is a strong foam. Here is a picture of my 70kg/m3 EVA yoga block supporting my 80+kg weight with minimal compression. The foam that I use for speakers is 110kg/m3 density so even stronger. But EVA is also used as a building material under floors for vibration dampening, in gyms as floor mats, under machines for vibration dampening, and within walls for sound isolation (covering whole internal space so no leakage around edges). So it was this combination of strength, vibration dampening, and sound isolation (absorption) which made me explore this (and fall in love with it) as a speaker enclosure/front-baffle material.
Attached Images
File Type: jpg P1130182.jpg (97.6 KB, 40 views)

Last edited by jeshi; Today at 02:33 AM.
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Old Today, 02:23 AM   #368
jeshi is offline jeshi  Japan
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Originally Posted by ewollowe View Post
I live in Australia Jeshi, flip flops are a way of life over here

Thanks for the excellent explanation.
you are very welcome.

ps: small correction, closed cell foam is porous. For some reason I thought porous meant that the cells are connected and air/water can get through. But I double checked the definition and it simply means a material with pores or cells filled with liquid or gas.

Last edited by jeshi; Today at 02:50 AM.
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Old Today, 10:44 AM   #369
Mattes is offline Mattes  Germany
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Hi Jeshi,

I donīt have any leftovers, used up all the material, as I had to rework one of the small flowers due to a little bit too enthusastic sanding... that used up exactly all spare material.

Hi Ewollowe,

Iīm not sure I understand your concept. Youīre talking about Bipole, or Dipole? Could you maybe post a sketch or photo of your arrangement?

Hi XRK,

yes, itīs expensive, but has different properties as BB ply. For a short moment, I thought about building the bass flowers from wood, due to the price of EVA. But imaginating the handling of a baffle of 930 mm diametre and maximum of 160 mm depth made from wood, together with the 18 kg of the AE Dipole 18, let me quickly alter the direction of thoughts.

All the best

Mattes
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Old Today, 11:03 AM   #370
ewollowe is offline ewollowe  Australia
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Hi Mattes,

It's just a VERY basic bipole, driver on front, driver on back. I'll post some pics when I've made a little more progress as I've pulled them apart at the moment.
I'm one of those people crippled by analysis paralysis so inspired by all the foam antics going on here I bit the bullet and glue gunned a couple of cheap 8" fullrangers into a standard polystyrene box. Lots of issues but also lots of promise.
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