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Acoustic properties of reticulated foam speaker grills?
Acoustic properties of reticulated foam speaker grills?
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Old 3rd August 2021, 04:51 PM   #1
cvanc is online now cvanc  United States
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Default Acoustic properties of reticulated foam speaker grills?

Do we know of any discussions on sonic properties of this? I haven't found much. Surely it does a little something, right?

And what about your PPIs? Seems 30ppi is readily available, is that considered good stuff for the high end crowd?

Examples:
Speaker Grill Foam Filter | Foam Factory, Inc.

The Foam Factory, Open Cell Foam, Speaker Foam, Filter Foam
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Old 3rd August 2021, 05:34 PM   #2
RogerGustavsson is offline RogerGustavsson  Sweden
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30 PPI will soak uo some high frequencies. I have had thin 10 PPI on some speakers and that made a difference over 20 PPI.
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Old 3rd August 2021, 06:20 PM   #3
Galu is online now Galu  Scotland
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The following information is taken from: Sound-Damping and Acoustic Materials in DIY Speakers

Quote:
Grille foams are, by nature, acoustically transparent. Also known as reticulated foam, the cell-like structure is of an open weave arrangement and easily permits the passage of air. Each cell is around 0.7mm in diameter and the number of cells per linear inch specifies the structure. For this application 35ppi, (particles per inch). Usually black in colour the open cell structure has little intrinsic strength and the material has to be supported on some type of frame. The material will not take to stretching as the restoring force is minimal and once stretched the original dimensions cannot be recovered. The minimum usable thickness is around 10mm. At 20 / 25mm the material becomes self supporting, (depending on area and hence avoids the effects of grille frames). Susceptible to UV light, sunlight, the material slowly crumbles and has a usable lifetime of 10 / 15 years before requiring replacement. Often used on designs of the 70's and 80's.
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Old 10th September 2021, 03:36 AM   #4
cvanc is online now cvanc  United States
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Quote:
Originally Posted by RogerGustavsson View Post
30 PPI will soak uo some high frequencies. I have had thin 10 PPI on some speakers and that made a difference over 20 PPI.
Exactly what I needed to know, sir. Thank you!

Do we know of a good source for 10PPI? I've only found one so far, with a steep minimum order.
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Old 11th September 2021, 05:04 PM   #5
bentoronto is offline bentoronto  Canada
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Acoustic properties of reticulated foam speaker grills?
Can't imagine any question that is easier to test. You stick your laptop in front of the speaker and do and before-and-after test. No special mic needed. You can do it in an audio store.

I have a thin synthetic paisley cloth over my ESL panels. I can double and quadruple the thickness for testing.

Here's a plot of with- and with-out. Maybe the 1 dB loss north of 13kHz is real if entirely inaudible. But any odd deviation might be due to a truck driving past at that moment. Or maybe dust since I've used those cloths on those panels for 45 years.

B.
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File Type: jpg cloth.jpg (126.3 KB, 61 views)
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Last edited by bentoronto; 11th September 2021 at 05:07 PM.
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Old 11th September 2021, 05:50 PM   #6
Galu is online now Galu  Scotland
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Quote:
Originally Posted by cvanc View Post
Do we know of a good source for 10PPI?
The industry standard for speaker grille foam appears to be R35 HIFI (35 ppi) and, consequently, many suppliers of the material don't indicate the ppi rating.

P.S. You don't say what thickness (mm) and area (mm x mm) you require.

Last edited by Galu; 11th September 2021 at 05:53 PM.
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Old 12th September 2021, 02:47 PM   #7
AVWERK is offline AVWERK  United States
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Does it have to be foam?
Stretched Spandex has always worked well and easily sourced
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Old 12th September 2021, 02:57 PM   #8
AllenB is offline AllenB  Australia
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Acoustic properties of reticulated foam speaker grills?
Aquarium filter foam.
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