JBL LE14C Maintenance over time

[thrash099]

A photo of the crossover box - I mounted the new caps outside

[academia50]

Congratulations Matt ! I'm glad that the result is to your liking, good job!

"Smoke on the Water" (Deep Purple) and enjoy!

[hoschibill]

Hi
It's nice to see that other people loves the LE-14C. I see a lot of nice work here. Wonderful! Here's a link to my C53 Libra restoration.

http://www.diy-hifi-forum.eu/forum/s...ead.php?t=5882

And a picture of my LE-14C:



BR
Oliver

[academia50]

Hi hoschibil

On treatment with brake fluid (do not share the idea, because if you alter the parameters of the speaker softening the wing, to change the fs, you must also change the tuning of the box (fb) ....) changing the tube tune.
Do not forget that the ideal for balanced sound is that any measure acoustic box as flat as possible.
Moreover, the photo attached does not correspond to the same speaker, the cabinet is not the C-53, is very small .......



Regards

Rolo

[hoschibill]

Hi Rolo

On treatment with brake fluid (do not share the idea, because if you alter the parameters of the speaker softening the wing, to change the fs, you must also change the tuning of the box (fb) ....) changing the tube tune.

The treatment with brake fluid are only for collectors who want their speakers in original shape. For those who want to listen to their speakers it is imho better to replace the surrounds with new foam surrounds. Then the speakers have the correct parameters and a sound as close as possible to the original speaker as they were new.

Do not forget that the ideal for balanced sound is that any measure acoustic box as flat as possible.

Yes I know it .

Moreover, the photo attached does not correspond to the same speaker, the cabinet is not the C-53, is very small .......

The picture is from my LE14C after restoration. The enclosures are original C53 Libra.

LG
Oliver

[academia50]

Hi Oliver


Now I understand, thanks for the explanation, friend

They look great now! Congratulations !

I see you used my method of "painting" exlusiva rejuvenating , and the same wings, good job !

you've changed the original tweeters by any chance?



Please attach a picture of the speaker mounted in the cabinet C-53, !
You've built your?



Regards


Rolo

[hoschibill]

Hi Rolo
Thanks for your appreciation.

you've changed the original tweeters by any chance?

The tweeters are the original ones. Both tweeters were damaged due overload but both coil windings were intact so I could repair both tweeters.

Please attach a picture of the speaker mounted in the cabinet C-53, !
You've built your?

I will do that when they were restored. The restoration is still in progress. A friend do this for me. New veneer is not my specialty .

Have a nice week
Oliver

[academia50]

Back in 1978 I built the boxes for the JBL LE14C following the verbatim form of measures and armed with internal bracing, plywood panels and all gluing.
The only change was the design grid for web, but I thought was a nice aesthetically, I wanted to finish the job quickly and listen to boxes with the anxiety associated with my first job with high quality speakers and prestige. So were made simpler.
Argentina marks of those years had already passed through my hands, Ucoa, Audifiel, Leea, etc. .. The latter with designs copied from Altec Lansing expired patents the years 40/50.
The dimensions of the tube box tuned to 85 liters are:
4 inch diameter by 3 inches deep.
A friend "very knowledgeable" recommended me to lengthen the tube to achieve low with a little more "punch".
Willing to see if the sound would achieve my liking, I did some hearing tests once assembled the boxes, with various lengths of tubes, and indeed, the bass changed, "beat" a little more.
For my musical tastes at the time - mostly rock, Deep Purple, Pink Floyd, Led Zeppelin, Yes, etc. - I thought it was great advice and so enjoyed until a few months ago from them. With alternating periods with other brands, JBL sound always seemed more transparent and real, that's why I kept until today.
It was love at first sight .....
Continue, my apologies, I use the translator and a bit slow writing, but what a great help!

I return to the previous thread . My friend did not give me the best advice , I do not know as much as said or imagined ..... ami me the same sound like him.
The tube tuning than a long indicated on the drawings of JBL , acting on the grave so nice, not so deep , but had some punch .... Now , after so many years it occurred to me : And with the exact size recommended by the manufacturer , how to change the sound ?
So get to work . The cardboard tube 96 mm preferred . mm.de diameter and 138 deep, was replaced by a PVC as indicated by JBL , ( see previous flat wire ) or a diameter of 102 mm and 76 mm deep. The change was for the better, and much !
The serious down ( deeper ) , but more surprising , improved media ! Female voices charged a presence and lack of stridency that was not previously .
Here I emphasize two points :
1) I've tried for many years countless acoustic cabinets from the 70's and 80 's, I remember that we were one of the first houses in Buenos Aires audio to have a switching console to instantly be able to compare the sound of different pairs of speakers. Recall that no auditory memory, always difficult to describe the perceived sound, sometimes words are not enough, and often are ridiculously employed .... "Round sound" will sound "envelope" for example? Here there is no deception, the sound is present instantly revealing the strengths and weaknesses of the boxes. So I set up a simple set-top box signal source, two pairs of RCA output and an input. And to put a small switch in monaural signal and thus send exactly the same signal to both channels, left and right. We can use a balance going from left to right, or we can use two similar readers standart CD (44100 Hz 16 Bit) with the same material recorded and selected with the input key.
2) First Realize the modification of a single cabinet, did the tests and it convinced the remarkable improvement, I finished the other.
There was also another improvement I leave for the next thread. Now I upload pictures.
So, friends do not always give good advice, beyond good intentions.


Uploaded with ImageShack.us


Uploaded with ImageShack.us


Uploaded with ImageShack.us

Continue ......

[academia50]

Morephotos






Uploaded with ImageShack.us

Uploaded with ImageShack.us


Uploaded with ImageShack.us


Uploaded with ImageShack.us


Uploaded with ImageShack.us

[academia50]

Well, now I would like to ask ..... the change in sound, bass is understandable because different tube tuning moves the point of maximum SPL at low frequencies.

But why improved midrange???






Regards, friends



Rolo

[hoschibill]

Hi Rolo
It's done. Here as promised the pictures of my C53 Libra. Since yesterday they live again. Wonderful speakers, magnificent sound, dry bass.



It was a lot of work but it was worth it. It is amazing what these speakers were able to perform 47 years ago.

BR
Oliver

[hoschibill]

Hi Rolo
I forgot, your speakers are very nice. How much volume have the enclosure? 3ft³? Wonderful old style.

But why improved midrange???

If you move the tuning of the port to lower frequencies (longer port), the bass is deeper and quieter. If you move the tuning to higher frequencies (shorter port) the bass is less deep and louder. In relation to this, the mids are loud or quiet.

BR
Oliver

[academia50]

Well, now I would like to ask ..... the change in sound, bass is understandable because different tube tuning moves the point of maximum SPL at low frequencies.

But why improved midrange???


Rolo

The answer is to change the length and diameter of the tube, the Fb (tuning frequency of the box) moved below
The Fx, crossover frequency, 12 dB / octave is 2000 hz. Recall that the flat section of the cone is reproducing the mid / bass and tweeter upper mids. (Area surrounding the tweeter, which is flat and has no ripples)


There is an advantage in reproducing average critical frequencies for large cones, see:

http://www.troelsgravesen.dk/HES.htm

Post scriptum

I had a mail from a guy who had just heard a pair of vintage Pioneer speakers, actually the HPM-100. Below to the left:

The questions from the writer were these: Why does this speaker provide such a pleasant sound? Why is it so easy to listen to? What does it have that most modern speakers do not have?
Well, I have never heard the HPM-100s, but this speaker is a Japanese clone of the famous JBL L100 Century (speaker to the right above). The JBL was a three-way system not having the supertweeters these Pioneers have.
One important thing that may be part of the "pleasant" sound and an "easy to listen to" speaker is probably the fact that a major part of the midrange is handled by a large cone. The JBL 12" bass driver really handles all of the midrange and the Pioneer probably also. Large cones = minor cone movement and reduced distortion. Now, the L100 is (was) not the most respected speaker around when it comes to neutrality, three-dimensionality and a number of other parameters we take for granted these days. The mid had major trouble due to poor filtering but I wouldn't be surprised if Pioneer had made a decent crossover for this speaker - and probably used a middriver not as notoriously difficult as the JBL LE5-2. I guess the system sensitivity is around 90 dB like the JBL L100.

Regards.

Rolo

[academia50]

Hi Rolo
I forgot, your speakers are very nice. How much volume have the enclosure? 3ft³? Wonderful old style.

If you move the tuning of the port to lower frequencies (longer port), the bass is deeper and quieter. If you move the tuning to higher frequencies (shorter port) the bass is less deep and louder. In relation to this, the mids are loud or quiet.

BR
Oliver

Hi Oliver !

I had not seen your answer, and I answered myself ......
Correct reasoning, we agree 100%.
Thanks for the pictures.
Congratulations on the new box, I see other JBL speakers there!
You could tell what they are and your impression compared to LE14C ?
Indeed, my boxes are three cubic feet, you can see it in the DIY plans that I attached.
I think the C-53 Libra corresponds to this volume.

Regards

[academia50]

Hi Rolo
I forgot, your speakers are very nice. How much volume have the enclosure? 3ft³? Wonderful old style.

Correction, your cabinet is the C-53 Libra, and mine DIY would be 3 cubic feet equivalent commercial JBL model Dorian S-12, bears the same components as the driver LE-14C but not in coaxial mount. The LE-20 tweeter and mid-twofer LE-14A







Uploaded with ImageShack.us