375 and 2440 mid drivers

[Earl K]

Hi Alex

I put (8) Radian replacement diaphragms into a batch of 2426 drivers a few years ago. They have that characteristic "Aluminum" sound of being a little bit "duller" ( or better damped ) when compared to a stock 2425/6 titanium diaphagm. IMO, this metal is better used in a near to mid field setup. In my world that means 10' to 30'. After 35', the titanium is my first choice for the metal type for the diaphagms' dome .

Quality: Their build tolerances closely match JBLs' for gap fit - but - I find the plastic used in the ring that holds it all together is a little soft. ie : one has to be very careful to not "strip" the plastic when securing the wiring to the terminal strips.

I also purchased a single Altec 802/902 replacement diaphragm. Its' a very close acoustic approximation of the older 808 diaphragm - meaning - since I prefer the 802/902 - I wouldn't ever pursue buying those.

I'll eventually buy a pair of the Radian large format diaphragms for my 2482s - based on the above impressions.

regards <> EarlK

[aust-ted]

Earl

Thanks for the advice on Al diaphragms for 2482s. It appears Radian is the only supplier of a drop in unit for this driver

I was also very interested in your comment about the sound of the Al as "of being a little bit "duller" ( or better damped ) when compared to a stock 2425/6 titanium diaphagm" .

I assume this is simply an outcome of the Al diaphragm being heavier than the Ti ones and being used in the same motor assembly.

Regards
Aust-Ted

[Unison845]

I have a single JBL 375H in blue and bakerlite sign, swimming in rain water!

Does anybody know how I can clean this driver, or take it apart? Any assembly diagram would help.

Thanks!

This is one that was on eBay awhile back.Its a JBL consumer version 375.The differences are obvious.What has not been discussed are the 375H versions.These came out during the era that JBL was painting there componets blue.So there are a few of these 375H units floating around in blue color.Rare but not much interest-yet!!! And don"t forget the other versions such as 375AB,375FH,375EX,375HP.These were the true mid range 375 assembles that had a larger coil gap at .043.These were similiar to the 2482 driver.
I measured the earliest humpback that I have against the early grey 375 (rounded endcaps) a while back.They were both close with a 3 db down on both units at 10.5K.

The lore of the old drivers is that supposedly the dura-aluminum material was recycled from skins of WW 2 aircraft.This was hi quality salvaged material and is the preferred diaphragm material in the golden ears crowd.The material apparently was not availiable for a long period of time and seemed to dissapear with the black 375 drivers introduction

Oldmics

[Oldmics]

Take the diaphragm out.Either use a non-magnetic screwdriver or be very careful unscrewing those phillips screws.

Then drain out the water and see how bad the damange is.

If there is rust scaleing up in the voice coil gap,its probably gonna have to go back to the factory for repair.

Oldmics

[Unison845]

The diaphragm is damaged. There is some rust in the voice coil gap, also in the throat there is some rust.

Is there any way that I can take it apart?

Take the diaphragm out.Either use a non-magnetic screwdriver or be very careful unscrewing those phillips screws.

Then drain out the water and see how bad the damange is.

If there is rust scaleing up in the voice coil gap,its probably gonna have to go back to the factory for repair.

Oldmics

[Oldmics]

Is there any way that I can take it apart?


Not really.To do it correctly you need a gaussing and de gaussing machine.

If its trashed-Put it on ebay as is and get a coupla bucks for it.

Oldmics

[John]

Well I could tell you how to do it without de-gaussing the magnet but I am afraid you could end up crunching your fingers and you would have to get a new throat for it for sure as it would be toast by the time it was disassembled
The magnetic power contained in that driver is beyond belief

[ralphs99]

Hi Aust-ted,
Good to hear from you!
I've been dreaming of buying various 2" parts on Ebay, and have noticed that you've been picking up same. 2397's and some drivers.....
Please let us know what you're building. I for one am very curious.
My 2 cents on the Al vs Ti debate: I had a pair of 2420's that were sounding ragged. I spent a lot of time trying to find replacment Al diaphragms. Finally Mike Caldwell at Vintage Audio Sales sold me a pair of lightly used 2426's at a good price. Big improvement! The new parts sound so much softer and more detailed. I can't say that it's definitely the Ti diaphragms that are the cause of the improvement. But I can recommend anyone with with older comperssion drivers replacing their diapragms either with Ti or Al. New is Good!

Cheers,

Ralph.

[aust-ted]

Hi Ralph

>I've been dreaming of buying various 2" parts on Ebay, and have noticed that you've been picking up same. 2397's and some drivers.....
Please let us know what you're building. I for one am very curious.

I have built a pair of dual bass boxes each using a pair of 2235Hs. Currently I am using them with 2450/ 2380 CD horns and 2404 baby bums, tri-amped and have been reasoably happy with them. However I have acquired a pair of 2441s which I intend to try out with the Smith horns which I have heard good reports on. Will try both 2440 and 2441 diaphragms.

>My 2 cents on the Al vs Ti debate: I had a pair of 2420's that were sounding ragged. I spent a lot of time trying to find replacment Al diaphragms. Finally Mike Caldwell at Vintage Audio Sales sold me a pair of lightly used 2426's at a good price. Big improvement! The new parts sound so much softer and more detailed. I can't say that it's definitely the Ti diaphragms that are the cause of the improvement. But I can recommend anyone with with older comperssion drivers replacing their diapragms either with Ti or Al. New is Good!

Suspect the improvement you got was mainly related to replacing worn out diaphragms with new ones. I am a novice on this forum but my reading is that most members seem to prefer the Al diaphragms for home Hi Fi over the Ti ones but I must admit my 2450 ones sound pretty good.

You might like to pick up a pair of 2420 or 2421 diaphragms when new ones come up on eBay. Not sure what others say but the Radian ones with the mylar surrounds might also be worth a punt. Then you will have a spare pair of drivers for another project.

Regards
Ted

[Unison845]

If it is that difficult, well anybody knows how much JBL would charge to rebuild it?
Thanks!

Well I could tell you how to do it without de-gaussing the magnet but I am afraid you could end up crunching your fingers and you would have to get a new throat for it for sure as it would be toast by the time it was disassembled
The magnetic power contained in that driver is beyond belief

[Unison845]

I also have a pair of JBL 150H, one of the driver has the dome pushed in, does anybody know how to fix it without damaging the cone? I figure using a small pin I can poke through and start pulling out, but may be somebody can show me a better way. Thanks!

Well I could tell you how to do it without de-gaussing the magnet but I am afraid you could end up crunching your fingers and you would have to get a new throat for it for sure as it would be toast by the time it was disassembled
The magnetic power contained in that driver is beyond belief

[Mr. Widget]

I also have a pair of JBL 150H...

It is very likely your speakers came from this or a similar setup...

http://audioheritage.org/vbulletin/s...ead.php?t=6856

...one of the drivers has the dome pushed in, does anybody know how to fix it without damaging the cone?

Domes are replaceable, or you may try wetting it and applying light suction through a hose or tube.

I would guess if the rust in your HF driver is extensive JBL will not repair it, if it is mild it will cost around $350 to get it fixed.


Widget

[Dave Zan]

I was also very interested in your comment about the sound of the Al as "of being a little bit "duller" ( or better damped ) when compared to a stock 2425/6 titanium diaphagm" .

I assume this is simply an outcome of the Al diaphragm being heavier than the Ti ones and being used in the same motor assembly.

The Al dome is not heavier than the Ti. It's nominally 10% less.
Ti is denser than Al so the Ti part is thinner to (almost) compensate.
The mass difference is probably within production tolerances anyway - it's about 5% of the total dome + Voice coil mass. .
The differences in response are mainly due to resonances in the suspension itself.

[pelly3s]

if you get the driver bead blasted its gonna be about $25 or $30 then the cost of a new dia. the dust cap if you are gentle you can pop it back up with the approach widget said, if that doesnt work cut it off and put a new one on.

if there is rust in the gap you can send it to any nut job speaker shop (like mine) and they should be more than happy to restore it for you.