19's damping material application?

[Valveboy]

Hello folks... Newbie here. Just purchased an abused pair of 19's. $500 for the pair, excellent on the outside, not so on the inside. But hey, it was local and they delivered to my house, so I figured it was a decent deal. Anyway, GPA has the drivers for reconing/reconditioning. My question is can anyone tell me where the damping material needs to be applied, and how thick the damping material needs to be? They
just have the "stuffing" inside hanging from the "ceiling" of the cabinets. The rest has been torn out. Apparently, in an effort to keep his cat from using the grilles/fabric frames as scratching posts, the previous owner liked to use them without them attached. Problem was, the cat just hopped in through the port hole and consequently had his way with the damping material. Does it go on every surface inside? And does anyone know of a good source for replacement damping material for these? How thick? etc. Looks like this would also be a good time to add some additional bracing in the back, so I'll probably be doing that as well, but any advice on the damping material is appreciated.
Thanks!
Dave

[RonSSS]

Hi and welcome Dave!
The damping materail is simple Owens Corning home fiberglass insulation. It's about 3" thick and has no paper backing. I'm not sure what R rating that would make it.
The 19's have it on all inside surfaces. Sides, bottom, back on the lower half of the cab, and sides back and top of the upper cab. It is simply held in with staples, 3/4" work well.
I just had my 19's all apart for bracing to the sides and back.
Altec also covered the insulation that was visible through the port with a black lightweight cloth.
Hope that helps!
Ron

[gearjammer]

The origanel altec factory insulation was only about 1 inch thick!!! Man that cat must of had a narrow head to jump thru that port???

[RonSSS]

Not in mine. It was 3" thick and was most definitly original.
Ron

[Valveboy]

Originally posted by gearjammer:
The origanel altec factory insulation was only about 1 inch thick!!! Man that cat must of had a narrow head to jump thru that port???

<font size="2" face="Verdana, Helvetica, sans-serif">That's what he said, but I sort of wondered about it too. The only other explanation is he removed it for some reason but didn't want to tell me.

[Altec19]

Perhaps Altec changed the amount of material they used at some point in the production run?

[Adhoc]

Depending on the density of the used glass fibre you get different absorbtion factors = damping inside the cabinet. Amount of damping varies with the frequency but as a rule of thumb; double density = double damping for one and the same thickness. Also, if the glassfibre is "elevated" from the cabinet wall = you have air in front of and behind the glassfibre you improve the effectiveness. So, Altecs "hanging curtain" of glassfibre is a good idea. (In my thread "Optimized cab size for 416B", I included a table with absorbtion / damping factors for different thicknesses and densities. The lowest density type, is the one usually used for house insulation, also the one which itches the most)

[zelgall]

One other thing about the insulation in Altec boxes, it's the most irratating and itchy type of fibreglas known to man. My 620's and the 19's are truly a menace to my skin, I make an effort to stay on the outside.

[RonSSS]

I won't argue about the irritating part. Fiberglass insulation is just that way. Keep your arms out of the stuff.
It is possible Altec changed the type and thickness. The point is, it's cheap at Home Depot or wherever. One roll ought to suffice.
And depending on what thickness you use, you can tailor the bass to your liking.
There are also other substances that can be used.
Since I just had mine apart, I can say that it was approx. 3" thick. I can also say that Altec was sloppy in the installation.
Ron

[Carl Bill]

I can attest to the fact that Altec changed the insulation over the years. I worked in the Oklahoma City cabinet facility in 1980 and actually assembled some of the 14's & 19's (we did not make very many) We used a yellow 3" thick insulation in about 18" squares. Also put this in the 828 cabinets. We did use a thin black fabric to cover the insulation near the port on the 19.

I also own a pair of 19's that were built in 1978 in California. They have the red fiberglass insulation in larger pieces, but still about 3" thick. No black fabric at the port on these. I plan to overhaul these soon and I will be putting some black material over the insulation to hide the red stuff.

I built a lot of the 828 cabinets while I worked there. I have 4 that I plan to overhaul this summer.