jbl 375/diaphragma

[nrwjbl]

Hi to all of you,
I'm a newie here and this is my first mail.
Probably my question has been discussed earlier.

I would like to change diaphragmas of my 375's (from the 70s).
Do you think I can do it on my own as I could get the suitable ones.
Is it difficult to arrange and change them ? (i.e. opening of 375 etc.).
Would appreciate your opinion. I would prefer to change them on my own otherwise I had to send that heavy load by post that may cause some trouble if mishandled.
Thanks for assistance in advance.
peter

[Earl K]

Hi Peter

(A) Professional Approach ; approx cost $ ??? Euro ( without diaphragm purchase )

- I'd recommend that you get "JBL Germany" to test your 375 drivers for frequency response and general health of the driver.
- I'd do this test before jumping to the conclusion that you need new diaphragms.
- How much are the 375 diaphrams in Germany ?
- I can understand your reluctance to trust any "Postal" system with your drivers. Therefore, I'd recommend driving to wherever JBL Germany is located for a personal visit ( if they'll deal with you directly ). I think the gas and parking is a small insurance policy to pay .


(B) Do It Yourself ; approx cost $ 250 Euro ( not including any diaphragms )

- I'd still recommend that you test the frequency range of your drivers before opening them up. This means ;
- Buying some testing tools such as ;
(i)True Audios' "TRUE RTA" (http://www.trueaudio.com/) ( $ 100.00 USD )
(ii) A test mic from Behringer "ECM8000" (http://www.behringer.com/ECM8000/index.cfm?lang=ENG) ( $ 57.00 Euro ) and a preamp in the form of
(iii) A mini mixer from Behringer , the UB502 (http://www.behringer.com/UB502/index.cfm?lang=ENG) ( $ 45.00 Euro )
(iv) Of course, the above list assumes that your computer has a soundcard of some sort and that you can make or already have or are willing to purchase some cables/adapters. ( $ 50.00 Euro )
- What horns are these drivers mounted on ?
- If you go this route, you might want to "practice" your installation techniques on some "cheaper" aftermarket diaphragms - such as what P-Audio sell. There would be a bunch of benefits to doing this ( apart from adding to the cost of your education - this way, any magnet induced/screw-driver "mishap" wouldn't be such a tragedy )

regards <. Earl K

PS; Another approach is to buy a Behringer DSP 8000 or 8024 to do the RTA analyzing for you. The advantage here is that the unit is stand alone. It has a test mic input , as well as the ability to generate Pink Noise, White Noise and Sine Waves of various frequencies. Here's a link to some present auctions on Ebay Germany (http://search.ebay.de/Behringer-DSP_W0QQsocolumnlayoutZ3QQsosortorderZ2QQsosortpro pertyZ2) . You would still need the Behringer test mic and a microphone cable to make this setup work. Still, it might be cheaper to go this route. It also offers the flexibility of having a mobile tester not "tied" to your computers location .

[Hofmannhp]

Hi to all of you,
I'm a newie here and this is my first mail.
Probably my question has been discussed earlier.

I would like to change diaphragmas of my 375's (from the 70s).
Do you think I can do it on my own as I could get the suitable ones.
Is it difficult to arrange and change them ? (i.e. opening of 375 etc.).
Would appreciate your opinion. I would prefer to change them on my own otherwise I had to send that heavy load by post that may cause some trouble if mishandled.
Thanks for assistance in advance.
peterHi nrwjbl,

seems that your'e from NRW. ......It's easy to change the dias....but...pay attention of the polarity. You only have to lift of the backplate, fastened with four screws and then the diaphragma base with 8 screws. Clean the surfaces and the gap with nonmagnetic tools. Ready for the new one. The diaphragma for the 2440/2441 fits exactly on the two bolts. Don't forget to check the right centering with a sine signal of about 400Hz. Check the foam stuff on the inner side of the backplate and change it when i's changed to powder.
HP

[nrwjbl]

This seems to be an interesting place to find people with profund experiences with JBL/Altec products. Thanks a lot for different detailed advices.

I think I'll follow Earl and choose professional assistance by JBL/Harman
as problems may occur if I try it on my own and results may not be as intended.

I'll take out my 375's of my Paragon and pass it for service to JBL.
In the meantime I install two 2450 drivers with K-2-dias instead of 375's.
This was proposed by a senior member of German Harman staff.
Anyone around who tried this before ?
What about replacing 375's and use JBL...... instead of 375's ??
Would that make any sense ?
I appreciate your experiences.

peter

[scott fitlin]

Well, the JBL 2450 will work, and IS JBL, but will not sound like the 375! The 2450 is a good driver, but you will have to listen to it in your system and decide which you prefer!

As I said, 2450 will work, but will not sound like 375!

Only you can tell if its good for you. :)

[paragon]

Don`t change the 375 paragon drivers.This ultimate dream speaker must have his original drivers.

Eckhard

[Oldmics]

Hello nrwjbl

There are two points of opinions regarding replaceing the diaphragms in your 375 drivers.

First would be the sonic quality combined with listening pleasure and second, the value of the 375 drivers as unmolested collectables.

Since these 375 drivers are presently installed in a Paragon which is a hugely collectable statement speaker-I say leave em alone.

The value of these systems fluctuates wildly when the original red wax seals in the 375 drivers are violated to replace diaphragms.If the original componets are no longer included with the system (as in replacments for the 375s),the values again go down.

If the drivers are in working order and you are looking for better preformance in the midrange section-try swapping out the drivers with a pair of 2440s or 2441s.Then try replacing the diaphragms in those replacement drivers to suit your taste.The 2440 and 2441 assembles are the same magnetic motors as the 375 drivers.
I also believe that the 2450s end cap will not fit into the Paragons cabinet.

This way you can keep the virgin 375 drivers for posterity and listen to (and play with) the different diaphragms installed the 2440 or 2441 assemblys.

You will be glad you saved the original drivers containing the red wax seals if and when you ever decide to sell your Paragon.

Best regards

Oldmics

[scott fitlin]

I didnt even think about this! The " value " of your paragon is determined by its authenticity of original components!

And IF you should remove those Red Wax seals the value is diminished considerably!

I never thought of IF the 2450,s would fit, I assumed they would, since you say Harman/Germany recommended it, but Oldmics is probably correct, hes very knowledgable!

He does offer up a great alternative, though, sourcing some 2440/2441,s and trying different diaphragms!

:)

[Maron Horonzakz]

Value of unmolested virgin Paragon $10,000........once violated value drops to $2,000 Keep you,r filthy hands off my Paragon.

[scott fitlin]

Such high prices for Virgins these days!

And so few Virgins these days!

Whadda we gonna do? :confused:

[Don McRitchie]

I have deleted Ilf's shop manual excerpt since this is proprietary information.

[nrwjbl]

Hi folks,
well, your postings show me that it is better to leave my 375's untouched.

I appreciate Oldmics statements that impressed me by giving important views on the subject. In the meantime I decided to keep my Paragon unmodified.

Its a helpful idea to try different dias with 2440/41 instead of modifiying 375's. Hope I can get them. Two 2441 are offered on ebay-auction-Germany for today about 450 €.
Many thanks for helpful comments and good hints preventing me from silly actions.

best regards
http://audioheritage.org/vbulletin/images/smilies/smile.gif

.

[paragon]

This drivers have also their red wax seals , when i remember ??

Eckhard