30 PPI foam for HOM absorption in waveguides - diyAudio
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Old 27th August 2009, 03:40 AM   #1
JLH is offline JLH  United States
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Exclamation 30 PPI foam for HOM absorption in waveguides

I was looking for sources of 30 PPI open cell foam to experiment with. The problem I found is few places sell it in thicknesses required to fill most waveguides. I really don’t like the idea of layering sections of foam to get the required depth. I did contact one place that was willing to order it from the manufacturer in thicker pieces. However, cost would be a problem unless a group buy is used. Is there any interest in getting a group buy for foam?

Right now it looks like 8” cubes can be bought for $16 each if a minimum of 25 are ordered. So, if we get people to buy in pairs, then we need at least 12 people with one person buying 3 cubes. I think $36 for a pair of 8” cubes was pretty reasonable. Size tolerance is +/- 0.25”.

12” cubes would run $67 a piece if a minimum of 9 are ordered. I thought that might be a bit rich for most people, so I did not pursue it.
Let me know if you are interested by replying to this thread. We have until the end of October to get the required numbers.

Rgs, JLH
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Old 9th September 2009, 05:50 PM   #2
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I have posted measurements of a horn with *and* without foam today. Here's the thread:

The HOMster! (or How I Learned How to Fix a Horn)

I am using 1/2" thick layers of 30 ppi reticulated foam, purchased from McMaster Carr.
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Old 9th September 2009, 06:42 PM   #3
JLH is offline JLH  United States
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Very nice work Patrick. I used to run Image Dynamics HLCDs in my truck. Back in the late 80's and early 90's I competed in sound offs and won a few shows. It was a fun time, but I'm a family man now and have settled for home audio only.

I too found the foam you mention at McMaster Carr. I just really want to avoid making layers. I would like one solid and continious piece of foam. Right now it looks like there is a lack of interest in these 8" cubes. If I don't get enough people interested, then I'll have to go it alone.

Rgs, JLH
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Old 9th September 2009, 08:01 PM   #4
Sheldon is offline Sheldon  United States
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Quote:
Originally Posted by JLH View Post
Right now it looks like 8” cubes can be bought for $16 each if a minimum of 25 are ordered. So, if we get people to buy in pairs, then we need at least 12 people with one person buying 3 cubes. I think $36 for a pair of 8” cubes was pretty reasonable. Size tolerance is +/- 0.25”.

12” cubes would run $67 a piece if a minimum of 9 are ordered.
My experience is that the most important area to cover is the first few inches from the phase plug of the horn. An 8" cube should do the trick for the large majority of applications. The hardest part is finding a good way to shape it cleanly. Earl uses a hot wire. I hacked away at it with a sharp knife, then final trim with scissors. That works okay for one offs.

Sheldon
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Old 10th September 2009, 02:10 AM   #5
FrankWW is offline FrankWW  Canada
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Quote:
I too found the foam you mention at McMaster Carr. I just really want to avoid making layers. I would like one solid and continious piece of foam. Right now it looks like there is a lack of interest in these 8" cubes. If I don't get enough people interested, then I'll have to go it alone.
I bought some @30 ppi foam from a foam shop in nice thicknesses at a decent price. He was selling it to pond owners for their filters. So you might inquire at a local fish pond supply house
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Old 11th October 2009, 06:16 PM   #6
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I'm interested in getting foam, too. However, I'll be starting with filling 12" round waveguides so 8" cubes won't be quite wide enough. I guess I'd need sheets I could cut out and layer.

The McMaster Carr site confused me a little. I see "psi" specifications, but no "ppi" specs. I think "ppi" refers to pours per inch and not pounds per square inch. Would Patrick or anyone else please post a specific part number for foam that works on HOMs?
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Old 6th November 2009, 09:00 PM   #7
boudy is offline boudy  United States
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Default I'd also appreciate this information...

Quote:
Originally Posted by TrickMcKaha View Post
Would Patrick or anyone else please post a specific part number for foam that works on HOMs?
Thanks.
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Old 6th November 2009, 11:09 PM   #8
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Quote:
Originally Posted by TrickMcKaha View Post
I'm interested in getting foam, too. However, I'll be starting with filling 12" round waveguides so 8" cubes won't be quite wide enough. I guess I'd need sheets I could cut out and layer.

The McMaster Carr site confused me a little. I see "psi" specifications, but no "ppi" specs. I think "ppi" refers to pours per inch and not pounds per square inch. Would Patrick or anyone else please post a specific part number for foam that works on HOMs?
Here's what I'm using

Geddes on Waveguides

Note that the "solid" pieces used by Geddes are superior.
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Old 12th June 2010, 03:11 AM   #9
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Any of you gentlemen have leftovers?

My application is a pair of QSC 152 waveguides.
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Old 13th June 2010, 01:17 AM   #10
JLH is offline JLH  United States
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Quote:
Originally Posted by Ed LaFontaine View Post
Any of you gentlemen have leftovers?

My application is a pair of QSC 152 waveguides.
Hi Ed,

The group buy never happened because nobody showed any interest in it at the time. Below is the place you can get it from.

Poret Foam
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