I will need some cab insulation for my project cab I plan to build (eventually). I would like to use something similar to the insulation Kustom used so that I can make it as original as possible. Unfortunately, I haven't been able to find anything like it.
rodak Messages: 511 Registered: October 2001 Location: Georgia
Senior Member
Are you talking about that fiberglass insulation? What, exactly, is the purpose of it?
When I was a teenager, a friend took the back of his Bandmaster speaker cab off, and we saw a solid sheet of fiberglass insulation - it was apparently attached to the sides or something,and not the back itself. Well, looking at that, I thought the entire cabinet was full of the stuff. When I built my first cabinet (something the size of a Dual Showman cab, but with only two 12s in it) I went to the hardware store and bought a bunch of fiberglass batting, like you'd put into walls or attic, and literally stuffed the cab full of it. I think it sounded ok, but kind of dead. I really didn't know what I was doing.
Those Bandmaster and Bassman cabs were filled with fiberglass. The concept is called an infinite baffle where there is no output from the rear side of the speaker. Like the cabinet was infinitely large.
Later Kustom cabs were ported so they were only lined with the fiberglass batting.
You can use the type of fiberglass that is used for wall insulation, but it is rarely available in one inch thick unfaced rolls.
Kustom_Bart Messages: 601 Registered: October 2010 Location: Greenville, MichiGUN
Senior Member
I have a friend that owns a insulation company and he couldn't get me anything unfaced at all. He had some suggestions, but they would have been to much of a pain or would not have worked, like putting blown in insulation in a bag and smoothing it out and stapling it in there....it would have crackled really nice...lol!
I still find unfaced rolls that are used for adding on top of the existing attic floor insulation, but the minimum thickness is two inches, which will work fo Fender cabs. Three of four inches is much more common.
Are you talking about that fiberglass insulation? What, exactly, is the purpose of it?
That's what I'm talking about. Have you ever stood in a room with no furniture or carpet and listened to the echo? The sound just bounces all around off the floors and walls and ceiling. Same thing happens in the speaker cabinet and can make it sound hollow or boxy. The insulation absorbs some of the sound reflections and gives a cleaner, tighter sound.
As mentioned, there are all kinds of fibreglass insulation around, but it is all too thick. There are also all kinds of acoustic foam, but foam is awful expensive. It would cost about $60 - $70 to use foam in a cabinet that size. That's more than I care to spend.
vintagefan Messages: 166 Registered: March 2014 Location: Dallas
Senior Member
I ran a test on my K100C-8 4x10.....I took all the fiberglass insulation out, then put the back panel back on the amp. Without the insulation, the sound has some harsher echo, sort of a feedback harshness. However, leaving the back panel off the sound is ok. But best sound is when I put the fiberglass insulation back in. Bud Ross got it right.
oren hudson Messages: 274 Registered: March 2008 Location: Gastonia, NC
Senior Member
I realize that this is not your original question, but thought I'd throw it out to you. The general guide for insulating a cab is: If it's ported, line all sides and the back with about an inch or two. If it's not ported, stuff the open spaces, not so tight to interfere with speaker movement, but to fill up most of the open air. If your lining, like in Kustoms, I've used the backed stuff and of course, put the backing side up against the wood. Lots of folks have used mattress topers at Wal Mart, but I found those to be pretty expensive, so I went to the Lowes Home Depot type places and got the regular type insulation.
I found excellent speaker insulation and priced very reasonable. Poly foam........shaped like egg cartons and is used to cushion mattresses. $10 for a twin mattress and more than enough to insulate a (3) speaker cabinet. Very similar to the stuff they use in recording studio's. Acoustic rating is higher than fiberglass and won't make you itch. Not sure what the longevity is but at that price you can afford to change it out every ten years or so. Available at Walmart in the bedding section.