View Full Version : Need advice re getting debris out of rear vent.

02-23-2010, 10:23 AM
The shipper laid the back of a transducer on styrofoam in poor attempt at boxing and it of course moved around working styro bits through the vent screen into the vent itself. Anybody got any suggestions on how to get it out without removing the screen thereby ruining it and/or the foil sticker on back?

02-23-2010, 10:36 AM
pushed all the way through the screen? ... if gravity will get the pieces back
down to the screen, I'd try a vacuum tool smaller than the vent size (don't
want to suck in the voice-coil dome...). If static electricity is preventing the
bits from getting close enough to the screen to suck out, I'd try a needle with
sticky stuff on the end... failing that... very carefully using a solvent, very
judiciously applied, to melt the styrofoam (as a last resort, prior to opening
up the screen using a heat gun, if you're shy on that).

02-23-2010, 10:51 AM
pushed all the way through the screen? ...

Yes. And it appears as though they are a bit long/big to come back out by vacuuming when they are lying on their 'side'.

You have some other good ideas I will certainly try. Thanks.

02-23-2010, 01:11 PM
...or straighten out a small barbed fishhook. -Do- note that these are all
just things I thought of that -I- might try if faced with the same issue...
not tried/tested methods. Sounds like a tedious job, regardless. Good luck!

02-23-2010, 01:55 PM
What about a heat gun to heat the foilcal on the back, sliding a flat putty knife to lift as the heat allows. Remove the debris, and re-glue using a rubber contact cement.

Just a thought.


02-23-2010, 02:56 PM
There's a thought. ;)

02-23-2010, 04:41 PM
if you remove the foilcal use something like 3m 90 spray adhesive. Spray some into a bowl, add a little MEK to reduce the solids, and then use a cheap 1" brush to apply to the rear of the sticker. Allow the MEK to flash off, then apply to the speaker. type 90 spray is a high tack formula, better for long term adhesion than type 77 spray. however it sprays a thicker spray, not the atomized mist like type 77. the 77 is a good contact adhesive, but 90 will last the rest of your life.
you'll need MEK to remove the adhesive residue, test the speaker back to ensure color fastness before cleaning the residue off wholesale w/MEK.

this is the procedure I used to reapply my (home made) HP Indigo printed made foilcals for my 2385a horns. Be care, don't thin the type 90 too much, it'll work like a top.

Additionally if you want to ensure the foilcal adhesive surface is level, after the MEK flashes off you can use the silicone liner from a crack & peel label to level the adhesive (by transferring the surface finish of the label silicone liner surface to the adhesive surface).

Use a a low temp (warm not hot) piece of metal to heat the silicone liner up, allowing the adhesive to level.

Looks just like it came from JBL if you're careful & use good technique. (i.e. do a couple of practice labels to get your technique down b4 using the actual foilcal.

I use pieces of stainless 4x4", with brown tape on the rear, and measurement w/IR gauge to get ~ 165 to 170; and the adhesive will flow out perfectly against the silicone side of the sacrificial label liner.;)

02-23-2010, 05:06 PM
You guys are talking of heat and solvents without a thought of the styrofoam's properties.

I work with styrofoam and find that most solvents (even their vapors) and certainly heat will attack it and turn it into a gooey mess. It wouldn't be much good to get the screen off if the styrofoam were now stuck/melted to the inside of the speaker.

Just a word of warning.

I think if it was me, I would try to apply a light vacuum to the back to draw the foam to the screen and just poke at the pieces with something like a dental pick to break them up to where they will be sucked out.

02-23-2010, 05:11 PM
How about static electricity? What was it, a glass rod and cat fur that made static? Seems like those foam beads are more attracted to static than about anything else.

herki the cat
02-23-2010, 07:46 PM
=The shipper laid transducer on Styrofoam in box, working styro bits into the vent itself. Anybody got suggestions how to get it out?
Well, doyall;280139, Relax, you probably can safely remove the dust cap without damaging the cap-attachment to the cone to thoroughly inspect and clean out both the vent tube & the voice coil area. I have done this on four JBL 2245, 18 inch subwoofers in which the foam damping plug had already reverted to sticky liquid urethane goop in the vent tube & was proceeding over to the pole piece end into the voice coil gap.

Thirty Year Veteran Speaker Designer, Mr Bill Woods of the Yorkville Canadian firm passed on to me an excellent procedure for removing the dust cap safely, so you do not need disturb the foil/screen area back of the motor. It aint broke there any way. It is best to Clean out the vent tube at the voice coil area where you may find a more serious mess.

[ quote herki the cat ]=
'First off, My two cents worth regarding the removal solvent, "One more gem from the RCA Camden factory, Aka: " use only "MEK" Solvent , which is less toxic than Lacquer Thinner, Acetone, or Denatured Wood Alcohol Solvents. Do not use eye droppers to apply the MEK." [quote/]

[Quote Bill woods]=
Never allow any solvent to drift down towards the voice coil -former/cone interface; Apply the solvent "gracefully," only with a "que tip'' in small progressive steps __taking care not to saturate the cap edge with solvent__ and carefully lift the cap edge with a sewing needle as it comes loose from the cone, one small step at a time.

02-23-2010, 08:20 PM
So much to consider. Thanks everyone.

02-24-2010, 07:05 AM
You guys are talking of heat and solvents without a thought of the styrofoam's properties.:) That is precisely what I was thinking of... actually. If HtC's dustcap
removal process didn't require a good bit of practice and finesse, that'd
probably make the most sense... might also depend on what glue was
used on the dust cap. Mechanical extraction (no heat or solvents) does
seem 'safest'.

02-24-2010, 11:16 AM
Apparent success. I say apparent because I merely can't see any more styro. There is a little other type debris stuck to the foam in the motor that I couldn't get though. (Looks like grass? I can't help but think someone had this used in a car.)

Used a combination of methods suggested. With vacuum running some styro was repositioned with dental pick until enough of it was sticking out of mesh that it could be grabbed with tweezers. A few pieces that were stuck to the foam on the inside of the motor was retreived to the mesh using 22 or 24 AWG solid core wire with Aleene's tacky glue on the tip then fished out with pick and tweezers.

You guys are the best. You potentially saved a 121H from becoming a doorstop. I suppose I will find out when I test and put it into use.