JBL speaker rattling

sanderic · #1 08-03-2011, 11:24 AM

I own a Peavey TNT 130 that I just installed a JBL k140 in. Since Peavey uses MDF for its baffleboards, two of the recieving mounts were unable to be reused due to crumbling baffleboard, thus the speaker is mounted using two less screws than required. Problem is the speaker rattles on a low A when the volume is way up. Is there any way to fix this, such as using caulk to place the old speaker mounts back in, or some type of foam ring the speaker might rest on to absorb vibrations? If anyone has had this type of problem, please let me know how you fixed it.

sanderic · #2 08-03-2011, 11:26 AM

Also, do any of your recomend putting insulation in this cabinet? It did not come with it.

RickenBoogie · #3 08-03-2011, 12:06 PM

I would have the cabinet re-built, using proper plywood. Not sure about the insulation.

edbass · #4 08-03-2011, 12:10 PM

Often a "rattle" is actually an air leak, they can make a variety of sounds in speaker enclosures.
Does it use T-nuts? Is the baffle OK where the speaker gasket contacts it, will it seal when the speaker is in place?
If so, and if the crumbling mounting will allow for it, just use 4 mounting bolts that are opposed to each other; such as North, South, East, and West.
Every other mounting hole in your K series.
None of my old JBL's use more than 4 bolts, as was recommended to me by a JBL factory tech during an installation 40 years ago.
Also, avoid the natural tendency to crank them down hard; "snug" is good and what you are looking for, also using a cross tightening pattern (like lug nuts on a car) is a good idea.
If you crank them down you can distort the frame and cause an air leak, or in extreme cases even cause a VC to rub.

I'm not familiar with the Peavey cab you are referring to, but on general principle some sort of insulation is good.

billfitzmaurice · #5 08-03-2011, 12:14 PM

Quote:

Originally Posted by edbass

on general principle some sort of insulation is good.

On general principle cabinet damping is an absolute necessity. Visit the fEarful thread to see how it should be done.

nashvillebill · #6 08-03-2011, 12:20 PM

Rebuilding the entire cab is probably not cost-effective for the OP. And tons of cabs are made of MDF so this type of problem is common.

So here's a couple of easy fixes. If the MDF is just stripped out a little at the holes, then you can get little inserts called T-nuts that go in from the back side. You'd drill the hole out just a tad for the body of the T-nut to press in. Then you use the appropriate machine screw, rather than a wood screw, with the T-nut.

If the MDF is a little too crumbly for that, you can cut a few pieces of 1/2 inch plywood, maybe 1 inch by 2 inches, and glue them (with wood glue) to the backside of the MDF right at the hole. Then use a longer wood screw, or better yet T-nuts in the plywood.

And you can also rotate the speaker half a hole, to have fresh material for the screws to go in to. T-nuts in the new spot would be best.

Even small circular sections of the baffle cutout could be replaced, with backing pieces of plywood. Or the entire baffle could be replaced, but some woodworking tools would be required. And I doubt that would be required.

I'd glue or staple some sound deadening material in the box.

sanderic · #7 08-03-2011, 12:30 PM

T nuts are what peavey used in the construction of this cabinet, and there is not enough "wood" for the t nut to secure.
Edbass, thanks for your reply, (as well as all others), I will consider your suggestions. As far as rebuilding goes, used TNTs of this age are often found for around $100 on Craigslist, so that is not a good economic proposition.

billfitzmaurice · #8 08-03-2011, 12:38 PM

Quote:

Originally Posted by sanderic

As far as rebuilding goes, used TNTs of this age are often found for around $100 on Craigslist, so that is not a good economic proposition.

+1. I'd bag the cab, put the K140 in a decent box and do the same with the amp.

dhsierra1 · #9 08-03-2011, 12:49 PM

Quote:

Originally Posted by billfitzmaurice

+1. I'd bag the cab, put the K140 in a decent box and do the same with the amp.

absolutely +1, in the middle of tearing apart a TNT 130 and making lightweight separates, though just using the original Scorpion driver. Got the T/S from Peavey, made the cab 3 cu ft, and lined and tuned it (using WinISD). The new piggyback version weighs less than half what the original did and sounds a lot better, and that's just w/the Scorpion.

sanderic · #10 08-03-2011, 02:15 PM

I am always on the lookout for another K140 to be paired with the one in the TNT. At that point the TNT will be history (although it is a good little amp).

dhsierra1 · #11 08-03-2011, 02:22 PM

yeah, they are good amps, the only reason I'm doing this is to help a friend's 16 y/o son out as he's been playing bass for awhile and is ready to step up from his Fender Rumble 25 amp.

If you have two K140s you could certainly pair them up w/a lot of great amp choices in the 50-200 watt range both ss and tubes and have a fantastic sounding rig