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I'm trying to find replacement foam lining for a pair of horn-loaded speaker cabinets. The original stuff was dark gray, not particularly dense, flat (not corrugated or dimpled), w/o adhesive backing, about 1" thick.I've tried searching for 1" thick "speaker cabinet foam", "acoustic foam", etc.., and so far I haven't come up with a product that looks like the original stuff that I'm trying to replace. I've also tried emailing the manufacturer but this obscure Italian company is owned by a guy who would seem to be a bit obscure and/or eccentric himself, so I've gotten no response from him so far.
The closest thing I've found so far is called "Sonic Barrier", which uses an adhesive backing and is sold at Parts Express. However, that stuff does not really resemble the original stuff I'm trying to replace. Any help is appreciated, thanks.
Edits: 12/16/14 12/16/14 12/16/14Follow Ups:
take a sample to a foam store they can easily match (close enough) the PPI and sell you what you need. Best regards Moray James.
moray james
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Hey Winston:
I was going to email you regarding Arthritis but your email addy is not available though AA. You can email me: et"at sign"econotweaks"dot"com
and I'll email you back. I still feel better but not quite as good as when I was drinking the tea AND eating a lot of smoked fish (which is all gone for over 4 days) which was probably the most omega-III in me in a year or more.
E
T
You don't provide much information about the speaker: what frequencies are horn loaded, the size of the enclosure, density of the foam, where it's located, etc. I think the effects of horn loading will far outweigh the effect of 1" thick foam damping/absorption in determining overall sound. The type of foam is probably not as critical as how many surfaces are lined with it. The stuff from PE is perfectly adequate for most enclosure lining. Use a staple in each corner and center in addition to the adhesive backing, which rarely holds reliably. It doesn't need to be especially tightly mounted, as long as it isn't free to flap around. Apply the same amount of new foam wherever it was applied originally, and nowhere else unless you want to risk changing the sound.
I seriously doubt you can wreck the speaker by using slightly different foam.
By the way, I've studied and built speakers for 45 years, but there is always more to learn. Please let us know how it works out.
Peace,
Tom E
The speaker cabinets are the tall, triple-folded enclosures of a horn loaded design. There are two foam slabs per speaker, both are 9" wide. One is about 24" long while the other is about 18" long. The originals were not stapled or glued in, instead they slide into the bottom of the cabinet and rest against the slanted vertical walls of the interior.
In the link to Royal Device provided below, take a look at the photo that is fourth from the top. On the right hand side of that photo, you can see the end of one slab of dark grey foam peeking out of the bottom of that speaker cabinet. You can also view the the ends of two internal chambers or folds. Two foam slabs per speaker, one for each internal chamber.
In these latest photos, the manufacturer has chosen to show the speakers mostly without foam inserts, which leads me to believe that he designed the foam inserts as optional, removable "tuning" devices. I would need foam slabs for both speakers for balanced sound and/or experimentation purposes, and presently I am missing one set of foam slabs.
Pretty cool speakers, definitely worth fussing over. I would buy new foam for both speakers to match.
I expect that the foam is present to absorb higher frequencies of the back wave of the driver. In that case, it is important whether the foam is open or closed cell, and its density is secondary. Open cell foam is expensive to make and much harder to find. There is a simple test to determine which is which. I think if you can easily blow through a layer of foam, it's open cell, but a closed cell will be more resistant. Better check on that. I'm willing to bet the PE stuff is closed cell. If the original is open cell, you do NOT want to change to closed. If the original is closed cell, nearly any similar foam will work.
If it sat free in the enclosure, then I'd guess that's what will work for the replacements. Sometimes the foam works more efficiently when both sides are exposed. You might at least make a trial with two-sided tape or something easily removed.
Peace,
Tom E
Thanks for the great advice.I'm not sure if the foam is open cell or closed cell, I'll have to check when I get the pieces out of storage. I will ask Parts Express about the composition of their stuff.
I've been running both speakers without the foam liners, and so far I haven't noticed any ringing or unusual resonances. Mine are the MK II model with sturdy cabinets made of nicely finished Birch ply, rather than the solid Pearwood of the newer models. If you scroll about 2/3 of the way down on the photo page I linked above, you can see several speaker cabinets identical to mine "stacked" against the back wall of the listening studio. The openings on the bottoms of the cabinets are normally covered by removable black screens.
I am hesitant to use adhesives of any kind because the foam slabs must be coaxed upward into place from the bottom of the cabinet. There is no way to press down evenly on them once they've been inserted because of the depth of the cabinet. Besides, I like having the option of removing the foam slabs at will.
Edits: 12/17/14 12/17/14
I am a retired builder and insulated between floors and around plumed rooms many times. The insulation does not stop sound (hold up a piece of insulation and notice it hardly affects sound transfer at all). What it does is to "deaden" the sheetrock or flooring which lessens sound transmission. I think shat your goals should be are to stop reflective sound (from opposing walls ) and reduce cabined vibrations. Not to stop sound. Another thing to consider is are the speakers ported or not? And also consider this...is there sound inside the cabinets from a sealed horn?
Thanks for pointing out the fact that there are many things to consider when it comes to sound transmission and reflection control. I'm simply trying to duplicate, as much as possible, the implementations of the manufacturer.
The cabinets in question are a folded horn design so they do have an opening by which LF sound can escape.
.... decades ago, the acoustic foam I bought was sold by its density, i.e., its weight per cubic measure (i.e., foot, yard, meter, or whatever), and that was also how you determined it's frequency attenuation in the lower octaves, by its density, e.g., weight/volume. The greater the density, the lower the frequencies attenuated. (At least, that was the theory way back when.... )
I'm sure things have changed a lot for acoustic foams in 20+ years, but I suspect that the basic issue is still weight/volume/density. Thus, if you can get a piece of the stuff and weigh it to figure out its weight/volume, that would likely give you the type of density of material you need to be looking for if you want to match the original designer's choices.
In short, I'd just cut a 1" cube and weigh it out, multiply by 1728 and that should be your approximate weight per cubic foot. Once you've got the weight/volume nailed, you should be in a better position to get what you need to match what was originally installed. However, I would err on the side of more weight per volume being needed than what you measured, as the foam may have dried out and lost weight with time.
As for the exact type of foam employed, I am not sure that is such a big deal (others can chime in if not so) compared to getting the density correct, as the foams I looked at so long ago were all pretty much VERY similar stuff to Sonex, and basically 100% fungible. I went with the Sonex knock-offs, as they were MUCH cheaper and looked/felt basically indistinguishable from the real deal at far less price.
Sonex products currently employ foams that are either urethane or melamine (depending on fire safety requirements, it appears), and claims both are functionally equivalent sonically.
So if you find some cheap acoustical foam of the same density as your old stuff, and it is a urethane or melamine, you are looking at essentially a Sonex clone. Your old foam, being dark, may have been the urethane type, as these are dark brown or charcoal-colored in the Sonex line-up (melamine is usually light/white, but can be dyed darker, BTW.)
Gosh, I hope this helps and does not mislead. Of course, there are REAL speaker mavens out there who are up to date and current on all this stuff, and if they say different, GO WITH WHAT THEY SAY! ;-)
Best of luck, genungo! Let us know how it all works out for you.
Cheers,
WS
Very helpful, Winston! Thanks for taking the time to respond in such a thorough manner.
The sonic barrier foam from Parts Express looks mighty interesting. I'm going to find out more about it's density.
Hi folks,
Ive used bubblewraps as the lining of the inside of my speaker boxes and have fkund them to be very good... I like them better, than rubber, foam or any sound absorbing materials.
Thanks
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