Cabinet stuff (stuffing)

[John Y.]

Does anyone know what sound deadening material is used in JBL cabinets, such as the 4648A? Appears to be fiberglass insulation coated with some resin. Is this commercially available?

Thanks, John

[jblwolf]

YOU MAY WANT TO CHECK RADIO SHACK,THEY STOPPED MAKING IT BUT IN MY AREA I FOUND A FEW STORES THAT STILL HAD [email protected] A BAG!,THIS WAS THE CLOSEST STUFF THAT MATCHED JBL'S PRODUCT(THAT YOU COULD STILL BUY TODAY)-WOLF

[Mr. Widget]

JBL is using a "non-sheading" fiberglas insulation material. The brand that I buy is "Wrap-on" it comes in roll that is 1" thick by 24" wide. I usually buy it by the box, but many hardware stores carry it by the foot.

[boputnam]

I'll second Mr. Widget. But locally, I've only been able to find batting in the desired reasonably small quantities (versus pickup truck sized bundles) as the pipe wrap for plumbing. Rolls are something like 7-in wide, at least 3/4-in thick and 17-ft long.

I cut lenths double the needed size, fold in half and spot-attach with a staple-gun. As with JBL craftsmanship, I line the entire cabinet (not the baffle). Easy enough and works great.

Wear gloves.

[Mr. Widget]

Wear Gloves!!!!!!!

I wear a respirator too!

The stuff may be called non-shedding, but that is a relative term. It is not much fun to work with, but it is sonically superior to dacron, foam, even that old wool stuff that was popular pre 60's.

[Tom Loizeaux]

All of my vintage JBL studio monitors had 1" fiberglass insulation in them. JBL glued these to the interior walls and then spray painted the front baffles, getting a fair amount of paint on the fiberglass around the cutouts.
I actually replaced a few of the panels of fiberglass today in my pair of 4343s as they were getting frayed.
Some people suggest spraying a dusting of clear lacquer on the fiberglass to hold down shedding.

Tom

[Charley Rummel]

Has anyone ever heard of using the material (whatever it's called) available from fabric shops that's used for stuffing cushions and pillows? This was recomended in a DIY websight I came across once.

Also, how about going over exposed fibreglass insulation in a cabinet with a spray adhesive? I've never done it, but are there any thoughts to share?

Regards,
Charley Rummel

[4313B]

"Has anyone ever heard of using the material (whatever it's called) available from fabric shops that's used for stuffing cushions and pillows? This was recomended in a DIY websight I came across once."

If you're referring to polyfill that's fine but I wouldn't retrofit it into existing JBL enclosures as it doesn't add virtual volume which JBL designs depend upon. Fiberglass is a real pain but if you use gloves and a respirator it is manageable. Hitting it with a very light coat of clear spray paint helps. I asked G.T. last year during a "Citation 7.4" conversation if he had ever found anything better than fiberglass and his response was "nope".

[John Y.]

I am planning to restore a C37 as a subwoof - more later in a separate posting.

Looking at my JBL (official) drawing of the C37 enclosure, which I built in 1956, I see that they recommended cheese cloth stapled over the 1" fiberglass, and I did just that. I recently opened up this cabinet after almost fifty years and found that the fiberglass was intact, but not as fluffy as I remembered.

I plan to reline with fiberglass and I appreciate the help in determining how to go about it. The insulation in my 4648A's look like they are sprayed - probably after installation. Could be lacquer. Seems to be quite a heavy application. Maybe I should call JBL to find out exactly what they use.

Mr. Widget, I shall try to find some "Wrap-On." Thanks.

John

[4313B]

Yeah, I'd call them at see what they are spraying on it.

In your case, since you are starting from scratch, you will have to tune the volume anyway so use whatever fill you want. Be aware though that only fiberglass adds virtual volume. So, if you measure the net physical volume and come up with 4.5 cubic feet but want 5.0 cubic feet add 1" of fiberglass on every panel except the baffle. If you want 5.5 cubic feet then add something like 2" of fiberglass. When you tune the volume you will see just what effect no fiberglass, and then adding fiberglass, has.

[Mr. Widget]

Hi Charley,

The white filler material used in pillows is frequently called Dacron. That is the trademark of the fiber patented by Dupont. There are many speaker companies that use it, even some of the high end brands. It does not have the same sonic properties as fiberglas. In my opinion it does not sound as good. It will not absorb the midrange that can reflect back through the woofer cone as well as fiberglas.

I sometimes spray hair spray inside the cabinet to augment the non shedding fiberglass.

You can contact the folks at Wrap-on through their web site.

http://www.wrap-on.com/

Mr. Widget

[4313B]

"In my opinion it does not sound as good. It will not absorb the midrange that can reflect back through the woofer cone as well as fiberglass."

I've got two LE14H-1 subs that prove you right Mr. Widget. The original Citation 7.4 came lined with polyfill. I built two LE14H-1 subs and tried one with polyfill and the other with fiberglass. When using higher crossover frequencies, and no crossover at all, the fiberglass lined system sounded significantly better.

Hair spray is a good idea, never thought of that

Thanks for the link

[Earl K]

Hi All
You know, I'm just not sure that Dacron info (having no effect ) is accurate. I was just inside one of my test boxes (S99/ le14a), & added a pile of the white stuff ( local version of Dacron ) and lowered the Fb of the box about 4 or 5 hz.
I don't doubt that it's a lot less effective than good old fiberglass. I think it's about half as effective for virtual volume increase.
Now mind-you, we have a change in weather about to occur ( with / maybe thunderstorms ) and this does effect these types of measurements. But , the other untreated/stuffed box still measures where it has all winter ( low 40's Fb ) . When I finally build permanent boxes for my Vertical Twin project , I'll probably start with a 1" lining of the high density fiberglass ( like a stiff wafer board used in insulating skyscrappers ) / cheese-cloth to seal in those pesky glassfibers and finish up with a second layer of something loose like Dacron . Also just tried silicon winter/boot/no-salt spray on the exposed fiberglass - worked quite nicely ( left a slippery film instead of the dreaded itch ) . Thanks for the suggestion !

Regards <. Earl K

[John Y.]

Well, after looking through the construction drawings of the 4648A, the JBL Pro guy told me that the only thing that he could see was a parts list containing 1" fiberglas with nothing said about coatings. I suspect one would have to contact a shop person to find out what they do. It's possible that this is all done by an outside contractor, at least on the production cabinets.

I like the idea of spraying with lacquer. Hair spray is a form of lacquer, so it should do.

[4313B]

"You know, I'm just not sure that Dacron info (having no effect ) is accurate. I was just inside one of my test boxes (S99/ le14a), & added a pile of the white stuff ( local version of Dacron ) and lowered the Fb of the box about 4 or 5 hz."

Well that's a lot of hertz

I was going to take some measurements with a test box but now I will just wait until I finish a new pair of subs since I have to measure them anyway.