JBL Decade L36 restoration and upgrade project

[bobins08]

Great job. The cabinets especially look fabulous.

I noticed that you use one Jantzen and the rest Dayton. How did you arrive at that one cap being the Jantzen?

I can see it is in the signal path in series with the midrange driver .. is this cap considered more critical?

thanks, Bob

thanks, Bob

 

[Zonker92]

I just did a pair of L36's but recapped the L-pads and deoxited the pots with great results. But I noticed that the presence/brilliance pots affect all 3 drivers. Reducing presence/brilliance also reduces the bass so that when both settings are at 12 o'clock the L36's lose their imaging. It doesn't make sense. With other brands like Infinity, the 2 pots affect only mid- and treble ranges but this seems to be the JBL way. Now I just leave presence/brilliance at about 4:30 - which is nearly wide open. So your totally by-passing the original L-pads may be the right way to go?

Is there anybody more knowledgeable about JBL crossovers that has something to add about these presence/brilliance settings?

So this is the OEM schematic. It shows that the L pads for the mid and tweeter control only their own respective driver's output.

 

[fredjones]

Great job. The cabinets especially look fabulous.

I noticed that you use one Jantzen and the rest Dayton. How did you arrive at that one cap being the Jantzen?

I can see it is in the signal path in series with the midrange driver .. is this cap considered more critical?

thanks, Bob

thanks, Bob

Parts-Express only had that value cap available from Jantzen, no special reason otherwise.

 

[fredjones]

After having them for about a month and thorough break in. I would say money and time well spent and that these will be my go-to speakers for some time. I'm not sure how sensitive these speakers are, but I am using them with an 8.5 watt per channel tube amp (Elekit TU-879S) and the sound is all I could want form high to low.

Cheers

 

[fredjones]

Long term update here. I broke these out again recently for some listening. Bass sounded bloated. So I removed all the fiberglass dampening material and replaced it with Sonic Barrier 1/2" Acoustic Foam w/PSA. Basically I applied it to every surface I could inside the speaker.
Placed the crossovers on top of the foam.
It made a noticeable difference. These speakers are some keepers.

 

[GD70]

This is the final product. After listening for a few days they settled down some, but are not fully broken in yet. Its always difficult to describe how something sounds to someone else due to subjectivity, so I will keep it simple. I know these crossovers were intended for the fully modified cabinets that Troels Gravesen has on his website. I am not a perfectionist so I figured that it would be close enough.

The sound is very balanced and non-fatiguing. My setup now is a Pioneer SX-950 and Yamaha CD-S700 cd player and a turntable of course. The JBL sound is definitely still there, there is no mistaking the 125A woofer presence. I did run a subwoofer, now there is no need. Now I can leave the tonal controls neutral or bypassed as there is no need for any tonal correction, the speakers do it all. They faithfully reproduce with clarity all the music I threw at them. I did not consider the bass to be too boomy that I hear some complain about with JBL. I am very pleased with the results to be had from this vintage set of speakers.

Oh man! Those are stunning! Cheers to you!

 

[litefootdan]

Hi Fred,

I remember reading this thread years ago and I had purchased Troels' upgrade kit for the (essentially) L36. I was interested to find that you used his crossover schematic as well. I work INCREDIBLY slow and that is why I am responding so late to your thread. I have finally gotten the crossovers together and installed and I must say I am very, very satisfied with his handling of the L36. I didn't alter the cabinet as he did, I left the port. He did send a spun felt cabinet damping material and I think it did the job fantastically. I will definitely source a good place to buy more of this for future builds. Much of the reason I haven't focused on the Gravesen project is because I have been really taken by point source speakers, specifically crossover-less wide range speakers. But the newly treated L36's provide fun and satisfying dynamics. It really is remarkable how well his design brings the very best out of the LE25.

I am glad you are happy with your crossover redesign. Your work is very tidy and looks very nice. It makes my "nest" of wires and components look sophomoric at best. My build looked so bad I was ashamed to document and post here. But the sonics are stellar

If I may ask, in your long term update you said you broke the L36's out again..... What had you been listening to? Have your speaker tastes changed? Have you paired your L36's with any other amplifiers?

Thanks for your post Sir,

Dan

 

[fredjones]

I have since sold the L36 to one of my son's college buddies who plays guitar and he has them going with his amp and likes them.
He wanted something retro so they fit the bill. I am now listening to Tekton Lore speakers along with some low wattage tube amps, and the
occasional TPA3116 or TPA3118 amplifier.