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View Full Version : Thiele/Small on the LE14A, wrong?



Flodstroem
02-18-2016, 02:27 PM
In the list, JBL Thiele/Small-list I can read that the LE14-A have an Fs about 28Hz. If consider the variation in Fs specs to be 5-10% it could be approx 25.2 Hz at the lowest.

Now, I just have finished a refoaming of a pair of those LE14-Aś. After all refoaming was done, and the glue has dried I was able to measure the Fs on those woofers. My readings says 21 Hz on the woofer that had some 4-5 hours of braking in. The other one that had no braking in time measured Fs to be 22.5 Hz??

So my question is, did JBL use different types of foam surrounds, spiders or different amount of aqua-plas on the LE14-A? Or, is the Fs specs of the LE14-A in the list wrong

Or was it the wrong foam surround installed............. :banghead:

note, the foam surrounds came from Rick Cobb and they fitted perfectly on those speakers (old foam was originally fitted/glued on the rear of the cones, and the same did I).

Any suggestion why this miss-match has shown up would be great? :crying:

JeffW
02-18-2016, 03:28 PM
New spider?

Flodstroem
02-18-2016, 03:38 PM
New spider?

Nope! ;)

JeffW
02-18-2016, 04:25 PM
Reckon a floppy old spider might be your difference, then?

Flodstroem
02-18-2016, 04:44 PM
Thanks jeff for your reply,
However it doesnt seems to be that problems, the woofers looks like to be i new condition, cant even locate any marks from screws, nor gaskets and there is no scrape marks on magnets nor on the sticker on rear of the magnets.
My guessing is that the foam surround has rotten in the original factory boxes, but who knows............, so the question have not jet any god answer............so far

Flodstroem
02-22-2016, 01:29 PM
Finally I found some discrepancy between the JBL TS-list and the original LE14A catalog/specs. In the library:
http://www.lansingheritage.org/images/jbl/specs/home-comp/le-bass/page1.jpg

In the spec. list for the LE14A I can read the Fs to be 25 Hz. This is not the same as in the TS-list (28 Hz) so my thoughts for an error in the TS-list wasnt so bad........ :blink:

If taking into account that the specs may have some variables or tolerances of approx 5-10% my re-foamed woofers are not far from that eg. I would consider my test results as very good. Starting at an Fs of about, I think it was 23-24 H before the braking in. Here is a picture of one of the two LE14A, like in mint condition........ :)

remusr
02-23-2016, 03:19 PM
I would consider again the tired spider issue. I had a somewhat analagous situation with 4 2245's formerly used in a church for sound reinforcement. Foams appeared as new but mrasured fs = 14-15Hz for all vs spec of 20. Refoamed 2, same 14. Spiders look ok, are centred fine but are soft. I never realized the demands modern churches, with rock bands, place on sound systems.

Wagner
02-24-2016, 09:56 AM
In the list, JBL Thiele/Small-list I can read that the LE14-A have an Fs about 28Hz. If consider the variation in Fs specs to be 5-10% it could be approx 25.2 Hz at the lowest.

Now, I just have finished a refoaming of a pair of those LE14-Aś. After all refoaming was done, and the glue has dried I was able to measure the Fs on those woofers. My readings says 21 Hz on the woofer that had some 4-5 hours of braking in. The other one that had no braking in time measured Fs to be 22.5 Hz??

So my question is, did JBL use different types of foam surrounds, spiders or different amount of aqua-plas on the LE14-A? Or, is the Fs specs of the LE14-A in the list wrong

Or was it the wrong foam surround installed............. :banghead:

note, the foam surrounds came from Rick Cobb and they fitted perfectly on those speakers (old foam was originally fitted/glued on the rear of the cones, and the same did I).

Any suggestion why this miss-match has shown up would be great? :crying:
You're fine @ 22 Hz +/- 10%:
http://www.audioheritage.org/vbulletin/showthread.php?10664-LE14H

http://www.audioheritage.org/vbulletin/showthread.php?11317-LE14H-3

Zilch once told me that a bad spider on an LE14A was a rarity, that the hardening quality of the old Lans-a-loy versions may have actually helped to protect and preserve them (spiders)

I've never had any issues with them after re-edging (performance wise)

If this is the sheet that you are referencing, dated April 2 of 2012, I wouldn't; it's not in agreement with any of the other reference documents available:
http://www.jblproservice.com/pdf/thiele%20small%20parameters/theile%20parameters.pdf

From the Lans-a-loy days, 25 cps:
http://www.lansingheritage.org/images/jbl/specs/home-comp/le-bass/page1.jpg

Flodstroem
02-24-2016, 04:42 PM
Thanks Wagner for clearing this out. and for posting the links. :)
Yes that was the TS list I had as a reference. :crying:

It worried me that there was a more serious problem like demaged alnico magnets. A like new and strong magnet on a cone transducer will measure a higher Fs compared to same transducer with a weaker magnet. That was whats worried me

So, in the end those LE14Aś are in a perfect new condition, hehe