I think it’s time to repay these faithful and dependable warriors with an update both cosmetically and electronically. My counterparts say to clean them up, put some Poly on them and plug them back in.
The general consensus is 50/50 on updating them with new Caps, HF Control rheostats (front lower panel X2s) basically replace the crossover with new components’. My issue is that they sound great and everything on the speakers works. So here’s my dilemma/question: If they were your speakers (50 years old) and decided to do what I plan on doing what would be needed to bring these workhorses into the 20th Century. My music tastes range from Blues – lots of Blues to Stevie Ray Vaughn, 60’s & 70’s …. I don’t beat the hell out of them volume wise and listen to them 3-4 days a week.
What would you do in terms of component replacement without changing the sound characteristics which was the reason I bought them in the first place.
An suggestions would be greatly appreciated!
PS: What is the Blue material on the speaker mounting board on some JBL Models?
I have owned (and continue to own) many models of JBL loudspeakers and monitors.
To address your question about cosmetic update, it depends on the present condition. Myself, I would say if there were no deep scratches or deep indentations in the walnut veneer, a VERY light hand sanding with extremely fine paper on a sanding block, only WITH the grain would suffice, followed by a thorough dusting and use of a tackcloth. Your speakers were originally finished with a hand-rubbed oil process. The exact mixture used by JBL for years is not a mystery to some, but not available today (as it was highly volatile). I have used clear Danish Oil with great success. It is easy to apply and the oil and varnish composition does produce a beautiful rich finish. Please, dispose of any thought of applying POLY to your speakers. If you seek a greater sheen, apply additional coats of Danish Oil and rub, let dry and wet-sand. Repeat. And you can paste wax and buff. Personally, I like the "classic JBL look", I find the look of oiled Black Walnut to be singularly beautiful.
As for your questions concerning electronic upgrades... I have been down that road. If you like what you hear now, do nothing. Because anything you do will, in some way, change what you hear.
Now, my set came from a recording studio. Nicely cared for, even replaced one tweeter. After owning them a bit I got "the bug". After all, the grills were no longer perfect, and there was noise in 3 of the 4 L-Pads (one particularly bad, with dropout). I carefully removed the woofers and did what I could with DeOxit (great product) on the L-Pads. Couple applications. And the 'better' ones weren't THAT much better, and the 'bad one' was actually worse.
Time for careful entry and removal of the L-Pad panel and crossover. In visually inspecting the L-Pads, time (and use) had taken it's toll. The one had disintegrated inside, and the others had visible defects. I decided to replace all four. Then I began reading about crossover upgrades for classic speakers.
You can replace all the crossover components (the 4311 crossover is VERY simple) with EXACT value components and your speakers will sound 'like new' (after all, your crossover parts are antique now). Or. you can modify components and give your speakers a more 'modern' sound. There are some nice drivers there. The concept at the time was to build an affordable high performance speaker in a manageable cabinet utilizing a 12" woofer (this became the L-100 in the home). The 4311 was the studio counterpart. The crossovers were indeed simple. Much has been learned in the 40 years since, especially in the realm of crossover design.
If you change crossover components(and add to them) you WILL alter the sound of your speakers. I studied, and fretted, but did do an upgrade on my speakers, from adding 5-way binding posts and twisted pair Oxygen-Free wiring and updating the crossover network (subtly).
Now, I find the midrange to be smoother (a complaint about the system originally "much too 'up-front' midrange", but fixable to some degree with the l-pad control). I find the high frequency output to be more extended (even to the point of having 'JBL people" wanting to know if I changed tweeters, I hadn't). And the bass response to be better controlled. No loss of bass, just less 'boomy'.
And if you don't already, put your 4311's at ear height, like in a studio control room. That is the placement they were designed for, they will sound better.
All that being said, touch up your cabinets, show them some love. But oil them, don't poly them.
And if you like the sound your speakers currently make, and the L-pads are quiet, do nothing.
Plug 'em back in and enjoy.
Isn't that what it's all about anyway?
P.S. To answer your P.S.: The blue material on the face of many full size JBL studio monitors is paint.