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cjloker
11-05-2007, 09:27 PM
Hi,

I need some help determining the cabinet dimensions to put my pair of LE-8's in. I am going to run them as a full range speaker without a tweeter, midrange or any crossover network. If someone has the cabinet dimensions with the size of the port I would really appreciate your sharing this information with me.

speakerdave
11-05-2007, 10:06 PM
You mean the LE8T with the aquaplased cone and metal dome or the earlier LE8 with the light cone and the whizzer cone or the LE8T-2/2115 with the light cone and the metal dome?

David

cjloker
11-05-2007, 11:41 PM
Hi,

I'm looking for cabinet dimensions for the LE8 with no other designations.

Thanks,

Chuck

speakerdave
11-06-2007, 12:25 AM
That would be the early one with the whizzer cone.

Z-man was right, although I don't know what happened to his post. JBL put that driver in a number of enclosures from the L33 up to the C38. If you have good woodworking skills you could make Minigons for them. See the library. Check out the 1962 catalogue.

http://www.lansingheritage.org/html/jbl/catalogs/1962.htm

It has dimensions for a number of enclosures for which this driver was an option, although there are no details for porting (the cabinets were being sold too).

In the Plans part of the library you can find building details for the C36 and C38, the difference being orientation only.

http://www.lansingheritage.org/html/jbl/plans/c35-c39.htm

That is probably the largest suggested cabinet for that driver. There doesn't seem to be any tuning instruction specific to the drivers (the LE8 is not even mentioned), but rather just a general tuning for the enclosure.

Good luck with that project.

David

cjloker
11-06-2007, 12:34 AM
Hi Dave,

Thanks for the information. This is at least a good start.

Chuck

Earl K
11-06-2007, 07:54 AM
- Below is the original le8 ( black cone / including a whizzer cone which is barely discernable in this old photo ) .

http://www.lansingheritage.org/images/jbl/catalogs/1962/page08-09.jpg

- The next model ( the le8t, ) quickly succeeded it ( with no whizzer cone ) . As a result of that quick turnaround, all the recommended cabinet info ( construction & tuning ) is for this slightly later model .

http://www.lansingheritage.org/images/jbl/specs/home-comp/le8t/page1.jpg

http://www.lansingheritage.org/images/jbl/specs/home-comp/le8t/page2.jpg


- Make note ( in the included info above ) that way back then in the early 60s / JBL recommended using the ( newly introduced ) PR8 as the best way to get more "robust bass" ( when using this model ).

http://www.lansingheritage.org/images/jbl/catalogs/1962/page22-23.jpg




http://www.lansingheritage.org/images/jbl/catalogs/1964/page35.jpg



from the Original Thread (http://audioheritage.csdco.com/vbulletin/showthread.php?t=7170)

Hi,

I'm in the process of re-edging two LE-8s that my father had in his stereo system while I was growing up. I removed them many years ago from the cabinets that he had built as they were in need of repair. Unfortunately I did not record the dimensions of the original cabinets. I believe they were ported and he ran the LE-8's as a full range speaker. I would like to build some new cabinets and possibly add a tweeter to the design. I'm guessing there is plenty of recorded information that would be of help in this project. I plan to utilize the JBL's with the Dynaco Mark III's that he alos bulit that I have kept running over the past twenty years. My father was a huge HiFi buff and it would be quite rewarding to have his speakers back in operation.

If you would be kind enough to direct me toward the resources needed to complete this project it would be very much appreciated.

Thanks,

Chuck


My inclination, given my experience with the LE8, would be to use a cabinet of similar size as the Lancer 33... around 1.6 to 1.75 cubic feet air volume, with about 2" to 4" thick fiberglass insulation on the inner walls. If you use a 1.75 cubic foot volume, a 3" diameter port, about 7 inches long will be about right (tuning frequency of around 33-34 Hz). Should give solid bass response down to around 33 Hz!!

As for using the LE8 in a 2-way- one suggestion that comes to mind, is to use an LE25 type cone tweeter (LE25/LE25-2/LE26/etc), and the crossover from an L19. The DCR for the LE8 is fairly similar to that of the 116A 8" in the L19... that crossover might well do the trick. Should be pretty easy to duplicate that crossover schematic, using off-the-shelf parts...

Regards,
Gordon.http://audioheritage.csdco.com/vbulletin/attachment.php?attachmentid=9994&stc=1&d=1126756823

- Gordons' advice was spot on in my view ( assuming that the Fs of your unit is around the stock 35 hz figure ). You should pop back into your original thread and ( belatedly ) thank him and all who responded for their time & effort .
- Here's more cabinet size ( & tuning ) info from an old ( 1960s ) JBL manual on speaker construction .
http://www.lansingheritage.org/images/jbl/plans/1960s-manual/page11.jpg

- Confused by too much info ? Here's more ;
- Do you know the Free Air Resonance ( Fs ) of your refoamed drivers ? If not, you should find someone to measure them for you.
- If they are similar to the old le8t they'll be around 35 hz .
- If they are, follow GordonW(s)' advice and call it a day .
- If the Fs of your refoamed drivers is higher than 35hz ( this is quite possible with todays surrounds ) then you'll want to choose a tuning that is right around the frequency they measure at .

- Do you know the dcr ( DC resistance ) of your drivers ? ( measure using a multimeter, set to the impedance scale ). Your old model may measure somewhat like the very obscure le8TX model . This model had a dcr of 11 to 13 ohms ( like the original 2115 vs the 2115a ) . OTOH, those coils might measure in the the 5.6 ohms range ( making this an 8 ohm model , regardless of what it says on the back ).


:)

4313B
11-06-2007, 09:43 AM
I'd have to recommend staying in the 3/4 to 1-1/2 cubic foot volume range. Too mechanically limited in larger volumes. They go down deep in the larger vented boxes but it's a tease because you can't listen to them very loud or you risk hanging the coils.

Earl K
11-06-2007, 03:14 PM
I'd have to recommend staying in the 3/4 to 1-1/2 cubic foot volume range. Too mechanically limited in larger volumes. They go down deep in the larger vented boxes but it's a tease because you can't listen to them very loud or you risk hanging the coils.

Good advice !



I posted this on the newly revised "single driver" forum, but I think there may be little overlap so I am repeating it here. Hope that's OK.

I had some LE8Ts re-coned, so I am posting my experience in case others are in need of this. I just picked them up today.

I had heard that the recone kits are often not available, or "on back order" for extended periods. But when I emailed JBL about a month ago, they had just made up 30 kits. I assume many of them are still available.

An LE8T frame can also be reconed as a 2115, which is a little more efficient but not quite so flat. (The D208, which is even more efficient and even less flat, is on a different frame.) Since I had four frames, I had a pair done in each version. It may be some time before they are all mounted and broken in, but I'll report on what I hear eventually.

The problem is that the foam surround on old drivers gets the foam rot. The surround is not available separately, so you have to spring for the whole kit - cone, dome, voice coil, etc. - it runs about $200, installed. The surround is an unusual size, and as far as I have been able to learn there is only one non-JBL foam kit that fits. It is widely sold by reputable shops, but it is far too stiff for this speaker. Caveat emptor! A friend used it, and found the resonance frequency was twice the spec value after extensive breakin - over 80Hz. IIRC it was over 100Hz initially. My newly coned drivers are 57Hz, with zero breakin, so I have reasonable hope that they will meet the 45Hz spec after they "meet the music" for a few hundred hours.

4313B

- If it turns out that Chucks' le8s have been turned into midbass units due to having overly stiff surrounds ( resulting in a highish Fs, as warned by Paul Joppa ) , do you have more advice to add into this thread ?

regards :)

4313B
11-06-2007, 03:28 PM
- If it turns out that Chucks' le8s have been turned into midbass units due to having overly stiff surrounds ( resulting in a highish Fs, as warned by Paul Joppa ) , do you have more advice to add into this thread ? Recone them? Didn't Gordon have a whole bunch of correct surrounds for JBL LE8's and LE10's?

Earl K
11-06-2007, 04:13 PM
Recone them?

- I suspect the sentimentality factor ( that these were originally Chucks' dads ) may override the desire to get them fully functional by using up to date cone kits ( that'll also change the looks ).


Didn't Gordon have a whole bunch of correct surrounds for JBL LE8's and LE10's?
- I do remember him talking about having the correct 10" foam surrounds / 8" surrounds draws a blank . If they're actually necessary, Chuck would need to ask him .

- David Weems ( in his books ) makes mention of; adding small incisions to surrounds to loosen up their compliance . Have you ever had to resort to such drastic measures ?

:)

grumpy
11-06-2007, 04:49 PM
... hmm... a bit like not changing the original tires on a car...
some folks are into that, but I don't think they'd cut slits in them.

Earl K
11-06-2007, 05:50 PM
.. hmm... a bit like not changing the original tires on a car...
some folks are into that, but I don't think they'd cut slits in them.

- I think we've read the info within this thread, differently.

- As far as I know, Chuck replaced the foam ( tires ) in his le8(s) 2 years ago .
- I'm concerned ( based on Paul Joppas old post ) that those surrounds ( now 2 years old ) are too stiff ( making a quest for an appropriate enclosure size, a bit of a moot point ).

:)

Robh3606
11-06-2007, 06:36 PM
Can he measure the Fs on them??

http://sound.westhost.com/tsp.htm

Rob:)

4313B
11-06-2007, 06:53 PM
- I think we've read the info within this thread, differently.

- As far as I know, Chuck replaced the foam ( tires ) in his le8(s) 2 years ago .
- I'm concerned ( based on Paul Joppas old post ) that those surrounds ( now 2 years old ) are too stiff ( making a quest for an appropriate enclosure size, a bit of a moot point ).

:)Oh, well, then buy the Woofer Tester 3 from PE and measure them.

cjloker
11-08-2007, 09:00 AM
Hi,

Thanks to all of you who have shared information on this topic. You are correct in that it has been about two years now since I put new surrounds on these speakers. I purchased the kit from Orange County Speakers specificly for the LE8 model not the T. I hope that they are the right surrounds to be as a full range speaker which is what I intend. I believe that I am going to use a 1.0 cubic foot ported cabinet based on the information I have received. I will let you know how they turn out.

Chuck