JBL 044Ti Tweeter Repair... well, almost

So I was having a near religious experience listening to my 240Ti's one night when I started hearing distortion in one channel. I pulled the midrange and tweeter, ran sweeps through them with the iFrequency app on my iPhone (thanks Zonker) and sure enough, it was the 044Ti. Sounds like something between a "bee buzz" and high pitched "honk" and is most apparent at ~440 Hz. Applying pressure to various places on the face plate lessens the buzz, but it doesn't go away.

I was reluctant to dive in, but after reading some others' posts I adopted the attitude "Its already broken, so what do I have to lose?"

First, off came the heavy aluminum mounting plate:


Then I pried the phenolic plate off the magnet with a putty knife. It was affixed with double-sided tape. Tough to pry while trying to be delicate and avoid damaging the dome or voice coil! Eventually it popped. Everything looked good with the voice coil wire and former


The dome damping foam had deteriorated and crumbled a bit. I've heard about this before. I removed the foam and cleaned up the adhesive with a Q-Tip loaded with orange solvent


Cleaned the back of the dome as well


Noticed some metal shavings in the voice coil gap. I worked folded paper around the pole piece, and vacuumed the gap clean


I read somewhere (probably Troels Graveson's site) that replacing the foam isn't an exact science. Its there to damp and support the dome, and I did my best to cut a new piece out of soft, open cell foam. As is apparent - not precision die cut!


Affixed the new foam and phenolic face plate with - wait for it - Shoe Goo! I threaded the faceplate bolts loosely, then tightened while running a 440 Hz tone with iFrequency.


The operation had all the hallmarks of one of my successful electronic world endeavors (I've had lots of bad ones too... and usually know it). No broken parts, no duct tape... only problem is, even with the VC apparently well aligned, I still get the buzz. Time to take apart again, and maybe start looking around with a magnifying glass.:sigh:

Anybody have any advice or ideas? I'm thinking now that if a finger on the dome lessens the buzz, maybe my foam damping piece needs to be larger and exert more pressure on the dome.

I don't think the foam is actually supposed to touch the dome at all. IIRC, it's in there to damp any reflections from the metal pole piece.

Might try simply removing the foam, test again. If you still hear buzzing, look for any breaks in the metal dome surface esp. along the creases, or loose voice coil windings. If the buzzing stops, reshape your foam to clear the dome and try it again.

John

The adhesive backed foam pad in the kits is roughly 10mm high x 22mm dia. You can imagine that the phram will mash this pad down a bit.

I also took a look at the 035tia kit.
The pad is exactly the same size. There is also a small pad that sticks on top measuring ~3mm high and 5mm dia.

Someone on the LH forum used soft wool sheet to replace the pad in a CD driver. Seems like a better idea than foam that finds it's way in the gap and the driver destroys itself.
There are foam filters in plenty of their woofers too. This filter will probably cause the same problem if it's not replaced.

Grey, thanks. So in my world, about an inch around by 1/2" high. This would definitely place some pressure on the dome. I'll make a new damping pad and check for tears as jdurbin suggested. Didn't see any the first time - maybe I need a jeweler's loupe

Round 2

OK, went back in with my wife's reading glasses. Upon some poking and prodding, I found that the voice coil former had separated from the Ti dome for about 1/2 of the circumference. I took a fine brush and some Zap a Gap glue (a.k.a. Super Glue Gel) and laid down a good stripe inside and out. I could see the line of the original glue swipe from the factory.



Thanks to Grey and his spec, I went to work cutting a new foam damper. Still Stone Age methodology - scissors and a block of open cell, egg crate foam - but I did a better job of approximating the dome shape with a single piece



Now to let the glue dry, then back to test tones...

For future reference, working folded paper around the magnetic pole is most likely not going to effectively clean debris out of the channel. What you want to do is fold a piece of packing tape (paper backed) over so that it has two sticky sides, and work that around the gap carefully so as not to rip it and leave a piece behind. The adhesive should be tacky enough to overcome the strength of the magnet, grabbing onto and ultimately pulling out any crap that may have accumulated in the channel.

Something else to consider is the inner edge of the voice coil. Is it malformed in anyway? Sometimes the VC coating comes from the factory with a slight drip which can cause rubbing and audible distortion. I imagine the drip could also happen if the VC heats up enough to allow the coating to melt. If the inside of your VC is not perfectly smooth you can use a razor blade to gently scrape away the offending drip. Be careful not to go through to the wire itself!

man hope this works for you but excellent try either way!

Seriously? JBL put a foam that can disintegrate in their Titanium domes? Man, that's 'depressing'! Another failure, I can 'look forward to'!

cnh2

Maybe I'm missing something here but that driver should never be making 440hz tones in a 240ti. Maybe 4000 hz but not 400. I had a 093ti mid driver in my xpl 140 that did something similar and the only fix ( after 2 failed factory diaphragm replacements) was to slowly and carefully tighten the screws in a star pattern and even that took a lot of trial and error.

Still, that's too low a frequency for that driver...

Jblnut

You're absolutely right. Sweep it from 2K to 20K.

cnh2 said:

Seriously? JBL put a foam that can disintegrate in their Titanium domes? Man, that's 'depressing'! Another failure, I can 'look forward to'!cnh2

Click to expand...

Probably the same foam they used for their L-100 grilles.

Wired - I used the paper to get the big chunks out of the gap, then I the wand on my Dyson vac to suck the rest out. It was clear when I finished. I checked the inside edge of the VC former, seems smooth to me, but we are talking about fine tolerances here, so who knows.

Nut & Grey - yes, JBL says sweep 2K to 20K, but the 440 Hz made it quickly apparent what was and wasn't working with the tweeter.

Pretty amazing to hear exactly what each driver can do on its own. My hearing is gone above about 14.7K Hz, but I was surprised to find the 104H mid reaching up to ~13K Hz itself (yes, that's 1K above JBL's sweep frequency as well).

Last go around - seems like I fixed the break between the VC former and dome, everything appears fine, but I'm still getting the buzz. So... new tweeters inbound.

New tweeters? What options are there for replacing 044Ti? I'd like to know since I am using a pair of 250Ti and while I don't have a problem with my 044Ti tweeters right now, who knows what the future may bring?

Do what I did - pick up a pair of 120Ti's while they are still cheap and available. Use these for excellent sound in another room until you need one of their 044Ti's or 104h's for your big boys.

Put your spares to work I say

Seriously though, this is the end of the line for spare drivers and spare parts. I also bought a real 044Ti spare driver still in the JBL box when they were closing all that stuff out. It had to be 5 years ago now. Some of the guys on the JBL Heritage site have built 250TI clones with other tweeters with good success. I suppose when the 044Ti's all die and we have no more options, we'll have to cross that bridge when time comes.



jblnut

jblnut said:

Do what I did - pick up a pair of 120Ti's while they are still cheap and available. Use these for excellent sound in another room until you need one of their 044Ti's or 104h's for your big boys.

Put your spares to work I say

Seriously though, this is the end of the line for spare drivers and spare parts. I also bought a real 044Ti spare driver still in the JBL box when they were closing all that stuff out. It had to be 5 years ago now. Some of the guys on the JBL Heritage site have built 250TI clones with other tweeters with good success. I suppose when the 044Ti's all die and we have no more options, we'll have to cross that bridge when time comes.

jblnut

Click to expand...

Hmm, I guess I'll be on the lookout for 120Tis! In the meantime, I will also be looking for "unobtainium" 044Ti spares too, thanks!

The 044ti comes up fairly regularly on eBay. I bought a beautiful pair for around $250 in the past year or so, and a 3rd for something like $90. May have to be patient to get a good price on a replacement though.

Although I don't advocate gutting speakers for parts, if you're going to do it you might want to pick the entry model 18ti which also uses the 044ti. However, they also tend to sell for $250 or better because of the parts demand for the tweeter.

John

I was considering keeping mum (and saving a potential stash) but The Speaker Exchange in Tampa, FL is still selling 'real' JBL 035TiA's. I just ordered a pair, and hope to bolt the guts into my rear-mount, aluminum 044Ti housings.

http://reconingspeakers.com/products-page/tweeters/jbl-035tia-tweeter/

Not quite 044Ti's, but I think they'll be close enough. JBL recommended the 035Ti as the best replacement tweeter when they discontinued the 044Ti.

I will keep an eye out for 044Ti's, but would be seriously bummed if, after my stockers failed, I bought another pair of 25 year old tweeters for serious coin, and then they busted. Hoping the new 035Ti's will be good for the next quarter century.

Is there a substantive difference between the 035Ti and 035TiA?

Don't give up! Theoretical long shot here: is the height of your replacement foam causing imbalance within the path of the voice coil? Are you trying to cram so much foam in there that it's binding at the outer edge of the windings? Try the tape suggestion anyway! maybe it's the outside edge of the voice coil that has the distorted shape? Man, drag. Literally.