128H Re-surround Problem-Advice needed

[evans224]

After doing maybe a dozen re-surrounds,I have run into my first problem (other than a messy job the first time around). I got a pair of 4412's cheap with bad surrounds on the 128H's. One of these came out just fine. The other I noticed had a rub in the voice coil area before I started. I figured that it would go away after re-surrrounding and centering the cone. While I was running the test tone after gluing it up, it was fine at the required volume. All good, right?

Wrong-I installed the drivers the next day, excited to fire up these things for the first time. I put in Blue Traveler's "Four", and turned it up-there was a rattle, big time at high volume. I could press on the surround to make it stop. Not good.

Well, what I did was use a blow dryer and a butter knife to gently pry up the surround from the frame. I commenced gluing it down again with the test tone playing, being as careful as I could to center the cone.

After everything dried, I could still feel a rub when I gently pushed up on the cone. So it was no surprise when I tried it out that at high volume, there was that rattle again.

Do I need a re-cone, or should I try to re-re-re-surround again? By the way, I really like these speakers! Even with the rattle, they are excellent. Very precise, excellent imaging, and they can move some air at the bottom end.

[Allanvh5150]

The last pair of these that I re-foamed and re-spidered, on one speaker there was a rub at first. When I took the cone out to put the new spider on I looked into the gap and there were some small peices of metal in there. I removed those and all was good again. The voice coil was in good condition.

[evans224]

I'm going to try to resurround and hope for the best. I may be looking for a 128H around here soon.

[boputnam]

I got a pair of 4412's cheap with bad surrounds on the 128H's. One of these came out just fine.

I'm going to try to resurround and hope for the best. I may be looking for a 128H around here soon.

I don't think it is the surrounds causing the problem.

Your first post indicated both woofs were affected. Do you know if the prior owner had them reconed, er, badly?

I suspect it is the spider that is misaligned. You need to loosen and reposition it. Proper surround positioning cannot compensate for a poorly aligned spider.

Do I need a re-cone...?

Yup. Sorry...

[evans224]

Thanks Bo. I have not had this problem before, and I suspect you're right. I'm going to try again, though. This is the second set of "deals" in a row that are going to turn out to be not such great buys. The L100T's I picked up for $85 are going to cost me around $400 if I want to do them correctly with new veneer, and the modified x-overs (I'm leaning toward parting them out. The wife is tired of looking at them with half of the veneer removed). These 4412's will run about the same if I recone for $200 or so.

[evans224]

Re-re-resurrounded-no go. Needs a recone. How would I know if the cone was rubbing before I bought them? Or is thqat for a different thread?

[grumpy]

Tough question. Assume the worst if the foam is gone... pay accordingly.

Sometimes you're pleasantly surprised. That's what I do.

[boputnam]

How would I know if the cone was rubbing before I bought them?

You've done too much to these to now go back and question their condition on sale to you. Sorry.

Just move on and get them serviceable!

[grumpy]

Ah, .. I read the question as being for future reference.

[evans224]

Ah, .. I read the question as being for future reference.

It was for future reference. I've purchased a half dozen pairs of speakers that had woofers in worse shape than these and had no problem. I just wondered if there was a way to check next time.

[grumpy]

If you have local access (vs asking a seller to test remotely), one
-could- carefully check for rubbing as well as looking for changes in
voice coil resistance while exercising the suspension while keeping care
to keep the cone 'flat' in relation to the moving axis (more difficult than
it sounds). Other suggestions have been made in other posts, e.g., looking
for sunk or asymmetric spiders (what centers the voice coil). ...

Still not a 100% guarantee, which is why I assume the worst.
Hope that helps some.

[boputnam]

I just wondered if there was a way to check next time.

Ah, it WAS for future!

Do a sweep, or at-least, get a 30Hz tone run into the driver at low voltage drive and listen. If the voice coil is ruint or out of shape in anyway, it will rub - you will be able to hear it.

[4343]

Ah, it WAS for future!

Do a sweep, or at-least, get a 30Hz tone run into the driver at low voltage drive and listen. If the voice coil is ruint or out of shape in anyway, it will rub - you will be able to hear it.

Usually, but:

I just refoamed a pair of 122A's that turned out to be a lot of fun.

The first one DID rattle with the tone, and I was able to get the still-wet glue apart before it hardened, then took the cone out to check the coil. It had a half turn of wire sticking out the back! I was able to unwrap the rest of the turn and fix it, so went on to the next one. No problems at all with the tone at low or medium levels, so after drying the two woofs go back into the 166's for some listening. About an hour in, I decide to test them at a "High" level for the first time, and heard a popping sound. Turned out the coil looked just like the other one, just the wire was not sticking out so far...

[delshadowrio]

I have refoamed many 128H woofers. I have had pairs where the vent foam broke down in the magnet vent hole and gummed up the voice coil. I was successful in cleaning them by using deoxit spray into the voice coil from the front with the dust cap removed and from the rear through the magnet vent. Spray and gently move the cone up and down. Be patient and do this as many times as it takes. Gently vacuum between sprays. It always seemed more on 128h with the white cones than the 128H1 with the black cones.

This is if that is the problem. You can see it when the dust cap is off. After that cleaning, I have not had a problem at any volume.

MM

[SMKSoundPro]

Is it just me, or does anyone else advocate removing the dust cap to refoam?

I see where the removal of the dust dome is important to assertain the quality of the VC, crap in the gap, blistering...etc.

In this manner, the VC can be properly shimmed and held in the proper level in realtion to the top plate, then new foam installed and left to dry. Do not fuss with it.

Then, when all is dry, sweep with sine wave test tone, if okay install dome, if not okay try again, or recone with new kit if available.

I understand the idea of Rick Cobb's style of 30 hz tone and not removing the dust dome, but I have seen too many blistered coils in my day to recommend this process to everyone.

Scotty.

Picture below from 2225 with a broken loose ferrite. Used as a view of a vc on pole piece.