JBL L100 restoration and upgrade

[Pete B]

I expect the impedance to decline with increasing frequency, and to be very low above 50 KHz
which can be problematic for many amplifiers.

 

[leesonic]

I expect the impedance to decline with increasing frequency, and to be very low above 50 KHz
which can be problematic for many amplifiers.

Do you think there should be a resistor in-line with that cap? What value?

 

[Pete B]

I'm wondering if he got tweeter attenuation with that cap but it is not the best
way to do it and it will tilt the response down.
Let me run a simulation, I'll post it here, give me a few days.

 

[Pete B]

Does anyone have ZMA files for each of the L100 drivers?

 

[SaturationPt]

I don't, but won't it matter which L100 version?

 

[Pete B]

It is the driver specs that matter, but I suspect that they are mostly similar.

 

[SaturationPt]

I would think that to be true, but the tweeter changed L100 to L100A, and there were minor changes to the mid & woof L100 to L100A to L100A (late) so I'm not sure how much the specs changed between them.

 

[Cylontymany]

I am looking forward in what Pete B comes up with. If the DM crossover can be improved thats a good thing!

 

[leesonic]

I have owned these speakers since 2011, but I never got around to doing anything to the cabinets. The last time I used these was back in 2021 to pose for a "see how many speakers I could fit into the picture" type photoshoot. It seems to be a waste to not use them, so I thought I would get them back into rotation. What with all the work I've been doing on my Infinity 3000 cabinets, I thought I would give the L100s some TLC as well.

But before we get into that, have a look at this woofer. Gravity and time seem to be having an effect on the "goop" that is used on the surrounds. I think it's time to rotate the woofers 180 degrees, don't you?



I love the copy on the back of the Minwax Tung oil can. "Dry, thirsty wood". You almost imagine the tongue hanging out of the cabinets.

 

[leesonic]

Here is a picture of me starting to rub the cabinets down. The one on the left is before, the one on the right is after, these cabinets had quite a lot of scratches in them. I don't know what kind of veneer JBL used, but it appears to be pretty thick. I was getting really aggresive, using 120 grit paper to rub the scratches down, sometimes I was even able to rub them right out, then going with 220 or 320 to smooth them.





Look at this light patch right in the middle of the right cabinet. Not sure what that is all about, but it looks kind of cool, I never noticed it before. There is something going on at the top of the left cabinet, more of that later.



I got a lot of the scratches out of the tops.



Looking from the other side, the cabinet now on the left (which was the one previously on the right) has the veneer lifting off. I didn't really know how to fix this, so I went easy sanding this one. Since this cabinet is the one with the light patch, this side can go close to the wall so it won't be seen.



Here they are with their first coat of Tung Oil on them. Look at that light patch now, it really stands out. I could stain it, but why?




And look at this on the top of the other cabinet. I don't know anything about wood effects and veneer, but sometimes nature just produces these amazing effects. Maybe it's that dry, thirsty wood licking it's lips?



Tops and other sides.

 

[allsmith]

The light spot is the sap wood in the walnut..technically counted as a defect in the walnut lumber industry..jbl must have let just a little slip thru back then as you see it in a lot of the L100s, but the book matched veneer looks excellent!..Today they steam and fume the walnut lumber so that the brown color bleeds over into the light colored sapwood and darkens it so they can sell it and get more wood from each tree..But it washes out the natural color of the walnut overall to a bland grey color and i think it looks like crap..they didn't do the steaming back when these speakers where made so you will see a large contrast in color between the heartwood and the sapwood

 

[leesonic]

@allsmith thank you for that explanation. It makes perfect sense to me now. I Googled "sap wood walnut", and one of the first images that came up was a cross-section of a walnut tree, showing the heart wood and the sap wood.

 

[leesonic]

And here they are, sitting next to my Infinity 3000s.

 

[Mr Boochie]

And here they are, sitting next to my Infinity 3000s.

Nice! How would you compare the sound of the two?

 

[leesonic]

Nice! How would you compare the sound of the two?

My JBLs have switchable crossovers. I find that using them in the "JBL mode", they sound very similar to the Infinity. I also find them more useful at low volumes in the JBL setting for some reason. If I play them next to my KEF speakers, I find in the "Murphy mode" on the crossover, they sound very similar to those. Edit - maybe not sounding similar, but it's more of a valid comparison, because the JBL mode can be very "in your face" at higher volumes.

This is why you can't just have two pairs of speakers... or 10.