time to retire the 044Ti....or what else to use in a 250Ti ?

[jblnut]

Hi All,

I have come - slowly - to the inescapable conclusion that the foam rot on the "damper" used in my 044Ti's is causing them to get less pleasant to listen to over time. I have been using the bus bars to diminish their output but this only goes so far. I have tried using all manner of expensive and well regarded tube equipment upstream but that too has stopped paying dividends.

So, seeing as I love the rest of the speaker, I am wondering a few things:

1) Does anyone out there "refoam" these? I've seen some DIY posts in that regard but I don't think I'm going to risk destroying mine personally. I would be willing to pay a pro to do it though, providing they have experience in this area.

2) What have other people used on their 250Ti clones or rebuilds ? I am leaning towards a nice textile dome for a slightly softer high-end and there are tons of choices out there. Just curious if anyone has some good first hand experience.

I'm really sad that this day has come, but I think I've been expecting it for some time. I can't keep dulling down my electronics to make up for an underdamped titanium diaphragm.

Thanks for any insight !

jblnut

[Robh3606]

Well why not get a pair of 052ti's and drop them in. Not so simple but at least it's a "close" replacement. I used 050ti golds in my clones. They sound great but I am sure sooner or later I may be in the same boat when their foam dampenng pad melts.

Rob:)

[rdgrimes]

Isn't it fairly straightforward to open them up and replace the foam?

035ti was used in some of the LE models weren't they?

[Robh3606]

035ti was used in some of the LE models weren't they?

Yes but I think they are now prohibitively expensive if you wanted to get a new pair. The 052 is supposed to be the replacement for the 035 and is much more resonably priced and avialable from JBL Pro in the current Transducer List.

http://www.jblproservice.com/pdf/Transducer%20List/Transducer%20List.pdf


Rob:)

[SEAWOLF97]

Isn't it fairly straightforward to open them up and replace the foam?

035ti was used in some of the LE models weren't they?

I got some 18Ti's (a good donor for 044Ti's) ..one had a crushed dome ....I was afraid of opening it up, but in hindsight, it wasn't really so hard ...grumpy had good suggestions on replacement foam

http://www.audioheritage.org/vbulletin/showthread.php?29325-044Ti-questions-Help-needed&highlight=044ti



Yes but I think they are now prohibitively expensive if you wanted to get a new pair. The 052 is supposed to be the replacement for the 035 and is much more resonably priced and avialable from JBL Pro in the current Transducer List.

http://www.jblproservice.com/pdf/Transducer List/Transducer List.pdf


Rob:)

around here you can get used 035Ti's for $100 a pair anyday. But then same old decaying foam problem again.

[Robh3606]

around here you can get used 035Ti's for $100 a pair anyday. But then same old decaying foam problem again.

Yeah me too but like you say you are going to end up with the same issue eventually. It's too bad we can't come up with an alterative material that won't shed and melt. Hell even a cotton ball might work. I can't measure out far enough to see the ultrasonic resonance you need a set-up that will go out to 30K or so. My CLIO set-up hits the wall at 22K.

Rob:)

[rdgrimes]

FWIW, "Cotton balls" are made from Dacron these days. The same material used to make the domes of the 033, 034, 066, 040. Can't say if it has appropriate damping qualities, but it lasts forever.

[rusty jefferson]

...2) What have other people used on their 250Ti clones or rebuilds ? I am leaning towards a nice textile dome for a slightly softer high-end and there are tons of choices out there. Just curious if anyone has some good first hand experience.

jblnut

Is the OP asking about other brands? I haven't DIYed any speakers (yet), but Seas makes great tweeters. They may have a model that would be a good replacement.

http://www.seas.no/index.php?option=com_content&view=frontpage&Itemid=1


(http://www.seas.no/index.php?option=com_content&view=article&id=54&Itemid=78)

[4313B]

You can use a little dot of felt glued to the pole piece instead of the foam and aquaplas damps the dome. There is no reason to use the foam anymore.

[jblnut]

You can use a little dot of felt glued to the pole piece instead of the foam and aquaplas damps the dome. There is no reason to use the foam anymore.

Are you saying the domes are aquaplas treated ? They don't look like it, but maybe I'm not sure exactly what it looks like (is it a clear coating) ? I'm more confused my the "there is no reason to use foam any more" statement. If the aquaplas coating was on there from the beginining, why did JBL use foam at all ? Didn't the foam initially make contact with the dome from the back and damp it somewhat ? If not, what was the purpose ?

Thanks a lot for all your responses everyone !

jblnut

[4313B]

The 035Ti and 044Ti were not aquaplased. I don't think JBL thought about the aquaplas solution until the LSR series.

[jblnut]

I'm not following you....if they don't have aquaplas then the foam is needed, right ?

My ears tell me they need it, as they have somehow gotten "brigher" over the past 10 years despite deliberate "softening" of the front-end eelctronics and a lowering of the bus bar levels.

I guess I need to man up and get out the putty knife....


jblnut

[4313B]

I'm not following you....if they don't have aquaplas then the foam is needed, right ?

My ears tell me they need it, as they have somehow gotten "brigher" over the past 10 years despite deliberate "softening" of the front-end eelctronics and a lowering of the bus bar levels.

I guess I need to man up and get out the putty knife....


jblnutGiven that you have to take them apart anyway you might as well just aquaplas them. I'll even send you a little bit of it. The foam should never have been used in the first place. It can be considered a manufacturing defect in the same spirit as lans-a-loy. JBL didn't fully understand the long term ramifications. Remember, all this crap was supposed to be built like a fine musical instrument lasting a lifetime. Human lifetime, not dog lifetime. :D If the aquaplas on the front bothers you, you can apply it on the back like I do. There is no phasing plug and millionths of millimeters of tolerance to worry about. You then take a little felt dot, like people place under chair legs to keep from scruffing up wood floors and glue that to the pole piece.

[4313B]

Here is what a proper Ti dome is supposed to look like. Greg was right in that "if it moves, coat it". :rotfl:

[berf]

Would the optimal size felt pad be the smaller 7/16" or the medium 3/4" from this set? They appear to be 1/8-3/16" thick. Would a poor quality light felt be preferable to a quality heavy felt? If you're only going to so this once per tweet to make them last forever you might as well use the right material.
http://ecx.images-amazon.com/images/I/51v7BNw6FyL._SY450_.jpg

[grumpy]

My thought is that between aquaplassing and replacing foam with a felt pad that
this enters the realm of redesigning (at least refining... or potentially ruining) a tweeter
and that some experimentation may be needed, network-wise as well...particularly
in regard to level.

Speculating that the aquaplas may help dampen some resonance that the foam
(which -pressed- back against the dome) most certainly did... perhaps in a similar
frequency range, perhaps not. Inserting a felt pad, presumably to absorb some of
the reflection off of the pole piece seems like a good idea... as with the foam, you
don't want crap in the gap, so a felt that was less likely to lose hairs would be good.
Maybe put a light coat of non-flammable hair spray on it :D (if there is such a thing).

It has been recently suggested to me, by one who should know, that there is a
frequency range (~4KHz) with this tweeter that can use a -little- deemphasis to
make it sound smoother... perhaps the proposed foam-replacement updates might
help... perhaps not. My point being that subtle voicing of the 250Ti was sweated
over at JBL and modifying the tweeter will almost certainly change that.

Perhaps I'm thinking too hard. It's just a tweeter... these are old speakers.
If it sounds good, report back... with comparison amplitude and impedance
measurements would be even better (stock/aquaplas/felt-A/felt-B/...) :)

[jblnut]

I will admit that there was a time when I was a "purist" and I would not have considered modifying my speakers or the drivers in any way. But I've left that by the roadside in recent years because, what matters most is - "do I like the sound". I've been trying a long time (you'll see it kind of danced around in many of my posts) to "tame" the high end of these speakers and it took hearing some modern ~$5-10k speakers to tell me all I needed to know. I am just not in love with the metal dome "sound" that these speakers have increasingly shown over the years. Yet I like everything else that they do, so a stab at tweeter modification or an outright replacement are both things on the table for me. Maybe it's my ears too, as I'm not the same as I was 10 years ago (who is?).

I recently bypassed the separate high-pass xover board that Giskard had made when I replaced the factory xovers, and I've gone to a fully active electronic crossover for the bass. The result was a huge imrpovement in bass speed and impact. It's not "factory correct" any more, but who cares - the result justifies the means.

So, now I'm taking on the other end of the spectrum. If I do go with a different tweeter, I'll be sure to share my experiences. Hopefully some aquaplas and fresh foam/felt will make that unnecessary though.

I haven't lost the faith, but maybe I'm looking for a more up to date interpretation if that makes any sense...

jblnut

[4313B]

Perhaps I'm thinking too hard.I think your points in your post are completely vaild.

I'm still irritated that JBL discontinued the D8R044Ti diaphragms.

As JBL continues to discontinue support we'll probably see more of these scenarios.

I have no solution for those with a toasted 104H.

[grumpy]

maybe I'm looking for a more up to date interpretation if that makes any sense...

Oh it does, speaking as one that participated in swapping out all of the drivers in a set of L250s and going completely active :)

I think you're on a good path... just might have a few (more) detours. I hope the aquaplas/felt experiment goes well!

[rdgrimes]

I'd guess that the departure from the original sound will be present regardless of whether you choose to re-build the 044 or replace it with a newer model.

Present day auto EQ routines in processors can easily deal with any introduction of peaks or dips of FR. I'm not sure that it should be assumed that modifying the XO is a requirement these days.

[Robh3606]

Perhaps I'm thinking too hard.

Hello Grumpy

You are making sense to me as well. You start doing modifications and there can be consequences that were not even considered. You are right about the voicing as well. It's too bad the kits are NLA. I understand jblnut's point as well. If you are not happy with them what's the point. It's one of those decisions you end up being forced into due to circumstances beyond your control.

Rob:)