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View Full Version : 2426H diaphram change to 275nd



Bernard Wolf
09-29-2005, 01:49 PM
Hi everybody

A few of you may recall that a while ago I bought at auction one (1) 275nd driver complete and one (1) 275 diaphram. These were purchased with the goal of one day upgrading my S/3100 to a MKII model, which uses the 275nd in place of the original 2426H. Now, as it might take some time to find another complete 275nd, I am left with the tempting possibility of swapping out the diaphrams in the 2426 for the aquaplased 275. This would be a fun thing to try, and even though there may be difference in sensitivity I do have the option to bi-amp to get around this problem. It would be every interesting though,to see (hear) if there is much of a difference between the 2 diaphrams without going all the way to the complete drivers (275nd) which are quite a bit different than the 2426H. It would be good to know which part makes the biggest difference, no ?

My question is this :

Is there something special I should know about taking out and installing the diaphrams? I had once read somewere here that they need to be installed with an oscilliscope. Does anyone know if that is correct and is there anything else I should be aware of?

Any information would be much appreciated before I go and kill my speakers....:blink:..... that would not be a good thing as I rely on them constantly to curl up and relax with..:o:

Thanks - Bernard

Zilch
09-29-2005, 02:19 PM
Not an oscilloscope, a signal generator. You need to sweep through the frequency range to make sure there's no buzzing, i.e., that the voice coil is properly aligned in the gap.

Have you been following my recent "Mini-Everest" machinations over in the Q&D 4430 thread? Johnaec and myself have become "believers" in the controlled directivity of the S3100 horn. Very cool.... :cool:

Bernard Wolf
09-29-2005, 02:59 PM
Not an oscilloscope, a signal generator. You need to sweep through the frequency range to make sure there's no buzzing, i.e., that the voice coil is properly aligned in the gap.


Yes I have been watching that thread although most of it is way over my head... I'm not technicaly inclined although I can take things apart and put them back together again :D... usually..

can the diaphram not be aligned by eye ? I ask because I once aligned a Lowther PM2 that way and it worked... I could bounce the driver though, to hear any scraping.. guess that isn't an option with the 275nd.

Zilch
09-29-2005, 05:19 PM
The tolerances are quite tight, nothing you could see by eye.

Some of the drivers have alignment bosses, I forget which ones, tho.

In any case, I wouldn't play it without running a sweep to make sure the alignment is correct.

Have a pro put it in for you, maybe. If they mess it up, it's on them.... ;)

Guido
09-30-2005, 03:26 AM
One thing to take care of is the screwdriver!!!!!

The magnetic forces are STRONG and can suck the screwdriver THROUGH the dia when installing.

In all other points follow Zilchs advice.

Mike Caldwell
09-30-2005, 05:19 AM
Hello
On the 2426 drivers there are no alignment post instead there is a slight recessed area that the diaphragm seats into. There is not really much play side to side for alignment. A couple of times I have had luck roating the diaphragm one half turn, make sure the screw are evenly tightened.

Mike Caldwell

Bernard Wolf
09-30-2005, 07:38 AM
Hello
On the 2426 drivers there are no alignment post instead there is a slight recessed area that the diaphragm seats into. There is not really much play side to side for alignment. A couple of times I have had luck roating the diaphragm one half turn, make sure the screw are evenly tightened.

Mike Caldwell

You mean rotating it back and forth somewhat to get it to seat properly into the recessed area?

thanks - Bernard

edgewound
09-30-2005, 10:06 AM
Hello
On the 2426 drivers there are no alignment post instead there is a slight recessed area that the diaphragm seats into. There is not really much play side to side for alignment. A couple of times I have had luck roating the diaphragm one half turn, make sure the screw are evenly tightened.

Mike Caldwell

The ceramic and neo magnet drivers have a step machined into the top plate that the diaphragm rests in. Also on the top plate for the gap, is 2 reliefs notched 180 degrees apart to provide clearance for the voice coil welds where the diaphragm terminals are located. Make sure your diaphragm ring is aligned with these notches and the wires don't cross when installing the back cap.
In case you didn't already know;) .
Thanks

Bernard Wolf
09-30-2005, 02:03 PM
So your thinking is that I would not need to use a signal generator ?

Earl K
09-30-2005, 02:48 PM
Bernard,

- You need a signal generator do have any hope of properly centering a 2425/6/7 diaphragm.

- You are looking for the cleanest sine wave tone of between 600 hz to say 1200 hz ..

- Once that diaphragm is in the gap , don't rotate it ! If you want to try a different position / extract it up & out of the gap / then turn it /& place it into the new position . Turning the diaphragm while it's in the gap can "burnish" the insulating coating off of the voice coil wire / essentially shorting it out .

- I find the tolerances for this particular series ( which includes JBLs' replacement diaphragms ) dictates a signal generators usage. The older Alnico based 1" drivers were harder to misalign .

- There are PC based solutions for creating sinewaves .

- If you aren't willing to take the necessary steps then take it to a Pro and have it done right .

- In Montreal ;
(i) Solotech is one such location.
(ii) Belisle acoustic is another ( Transparence is their other name ) . They do remags / recones of every make / and they build their own woofers .



:)

edgewound
09-30-2005, 02:58 PM
So your thinking is that I would not need to use a signal generator ?

By all means...you should use a sweep generator.

Bernard Wolf
09-30-2005, 04:21 PM
Well, I certainly appreciate the information from all of you here. I am still at odds though with what to do. I had hoped I could do it myself but I see that it would be better to have a pro do it. That involves perhaps a bit more than I am prepared for right now - it would involve taking the 3100 apart, getting the drivers off to the shop and after having the swap done installing them back into the 3100 only to have to do the same process all over again when and if I find the second 275nd. All this to perhaps find that I don't really hear any difference with the diaphrams alone. I might be better off to just wait till I find another 275nd complete and then just change all at once.

The only thing is that if I do it that way I will have an extra 275 diaphram sitting around doing nothing...:blink:... me thinks I will need to ponder this a bit longer.

Thanks again - Bernard

Earl K
09-30-2005, 04:41 PM
Huhhh ??? Okay !

- Then Bernard,,, just install the 275nd driver on the one channel only, take a listen to see if you can hear any difference .
- This might motivate you to then take the 2426 to a Pro ( if you like what you hear ) .

<> earlK

ps ;

,,,,and if I find the second 275nd

- From my perspective, they come up used on eBay once every five years .

Bernard Wolf
09-30-2005, 04:51 PM
Huhhh ??? Okay !

- Then Bernard,,, just install the 275nd driver on the one channel only, take a listen to see if you can hear any difference .
- This might motivate you to then take the 2426 to a Pro ( if you like what you hear ) .

<> earlK

ps ;


- From my perspective, they come up used on eBay once every five years .

Well, yes, but then the x'over is not correct... wouldn't tell me much now would it... five years sure would give me plenty of time to get a x'over up and running though ..:D.... BTW, I did say this was a looooong term project didn't I ?

Bernard

Zilch
09-30-2005, 07:48 PM
The crossovers are pretty close, actually, just different approaches.

http://audioheritage.org/vbulletin/showthread.php?p=67205&highlight=S3100#post67205

Bernard Wolf
10-01-2005, 10:38 AM
The crossovers are pretty close, actually, just different approaches.

http://audioheritage.org/vbulletin/showthread.php?p=67205&highlight=S3100#post67205

thanks for that bit of info.. may help me diecide to give it a whirl although after what Earl said about a possible 5 year wait I may just bite the bullet and take it all to a pro for a dias change..... think I will pop the cap tonight and take a look see.

B