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KCM
01-29-2010, 11:08 AM
I've got a spare 044ti for my 240ti's lying around. Curiousity got the best of me and I was able to get it apart without damage. As expected, the foam pad is mush. I would imagine the two in the speakers are in a similar condition, and that may explain why I found them rather dull sounding when I bought them last year. I have since reduced the resistor value from 5.1 to 3 ohms on the tweeter circuit, and they sound much better to my old ears.

On to my question: I have two pieces of 1/2" thick foam at my disposal. I have determined that the more open, filter media foam is easier to compress but it feels more "springy" and has an almost plastic quality. The other foam is also quite soft, albeit more firm and "damped" feeling than the media filter type. Does anyone have a suggestion as to which would be the better option to use as a replacement ? Looking at a pic of a diaghragm kit here as best I can, it almost seems as if the original foam was somewhere in between my two options......

Also, should I apply a signal to the tweeter when re-assembling to center the voice coil ? If so, at what frequency ?

Many thanks for any advice !

opimax
01-29-2010, 06:30 PM
I have been wondering somewhat the same thing. I have 14 044ti and 6 35ti or tia in service and a few spares. Some have been serviced most have not.

What are the choices for maintenance knowing that the foam will deteriorate over time? Change out the foam as suggested above or just leave it alone?
I would guess at some point doing something would be better then nothing.

Is there anything else I could do myself to these drivers? :blink:

Mark

Don C
01-29-2010, 09:09 PM
The foam on the right looks more like the foam that came with the 044ti diaphragm kits that I have installed. Unfortunately, the focus is poor on the picture that I have.

jbl_daddy
01-30-2010, 06:30 AM
How do you get it apart without damage? I have a spare, I removed the four screws and the front face came off, the rest is glued to the magnet.

KCM
01-30-2010, 07:02 AM
Thank you, Don !

I did the first one both ways, took a few measurements and listened for a bit. I can't tell any difference, but I did end up with your suggested foam. I then did the two originals, but the existing foam in those was in fairly good shape. Measurements afterward shows that the two supplied with the speakers measure similarly, while my ebay spare has ~ 2 db greater output.

jbl_daddy, it is glued and it is tricky to get off without damage. I used a screwdriver, being careful both not to insert it too far and damage the voice coil, and not stressing it too much while working my way around it's diameter.

rdgrimes
01-30-2010, 07:50 AM
Has it ever really been established whether that foam has any acoustic function? I guess I always assumed it was merely there to support the dome when/if it gets punched.

Earl K
01-30-2010, 08:06 AM
Has it ever really been established whether that foam has any acoustic function? I guess I always assumed it was merely there to support the dome when/if it gets punched.

- I assume the internal foam is supposed to lightly touch the backside of the Ti dome .
- Once touching, it'll provide some mechanical damping / helping control those nasty Ti "zinggggs" . Aged foam collapses & will pull away / possibly leading to an underdamped dome .
- Hence the somewhat paradoxal reports of older Ti domes sounding brighter ( than they should be ) .


- Anyways, that's my story & I'm willing to stick to it ( till proven otherwise ) .

<> cheers

rdgrimes
01-30-2010, 08:53 AM
- I assume the internal foam is supposed to lightly touch the backside of the Ti dome .
- Once touching, it'll provide some mechanical damping / helping control those nasty Ti "zinggggs" . Aged foam collapses & will pull away / possibly leading to an underdamped dome .
- Hence the somewhat paradoxal reports of older Ti domes sounding brighter ( than they should be ) .


- Anyways, that's my story & I'm willing to stick to it ( till proven otherwise ) .

<> cheers
No reason to doubt that, but of course the same foam is used on the soft dome tweets too, 044, 034, etc.



How do you get it apart without damage? I have a spare, I removed the four screws and the front face came off, the rest is glued to the magnet.

Heat might be a good start.

KCM
01-31-2010, 05:42 AM
To follow up, after listening to the speakers with the new foam for several hours ........... :applaud: