L100 Bass response

[BMWCCA]

I have some L65s that seem to have the same symptoms. Woofer cones that seem to be too free moving as compared to my other JBLs. A little muddy on the bottom, etc.

Are you guys all using old turntables or something?

I can play even my L96s at high volume and I can't tell the LE10H cone is moving unless I give it a burst like the big kick in Al DiMeola's Embrace, and even that's just a quick movement with no flutter or flop. None of my stuff from 6.5" to 18" seems to have that problem. I remember in college how boring it was when my friends wanted to see the D130s move to watch how something that big produced such a sound, Watching them with a flashlight through the C37's black grille cloth proved kind of boring after a while as they barely moved. :dont-know

[Robh3606]

I was wondering the same thing. I used to beat the hell out of my L100 with an old Dynaco St-400. Telarc cannons you name it. Never did they just flop around even with the cannon shots which had to unload them. Sure sounds like a feedback or tonearm issue to me.

Rob

[Fangio]

As it is, the 123A is a closed box driver.

Cork off the vents and see a dramatic improvement. The 123 drivers are very durable but mismatched in the vented enclosure. As a side benefit the midbass will be a lot cleaner and less boomy.

Slightly OT, sorry but I wonder if the same could be said from a certain 15" driver too.

It's the LE15B, also with accordian surrounds, and I have a pair sitting here doing nothing. Would closing the port help to improve the bass in, lets say a L200, C50 or 4503 type enclosure?

[4313B]

You'd have to run the TS parameters on them and post them.

#2

[Zilch]

Early S7 (LE15(A)) Olympus was closed box.

Seems easy enough to measure Fs and Qes to calculate EBP.

I have measured LE15B in L200 with the ports closed; the results are posted here somewhere, along with those of several other drivers in the same session....

[mech986]

I was wondering the same thing. I used to beat the hell out of my L100 with an old Dynaco St-400. Telarc cannons you name it. Never did they just flop around even with the cannon shots which had to unload them. Sure sounds like a feedback or tonearm issue to me.

Rob

You may have hit on another parameter even for the L100 - use of a strong, big SS amp with plenty of damping factor. Recall that the L100 was designed in the early infancy of big SS power amps. As amps got better, their output impedence went way down, increasing the damping factors, which usually leads to better woofer control near or below resonance. Also, with appropriate high pass filtering, efficiency is improved while avoiding the muddy low bass.

OP might want to try another amp and see what happens.

Bart

[Old curmudgeon]

You may have hit on another parameter even for the L100 - use of a strong, big SS amp with plenty of damping factor. Recall that the L100 was designed in the early infancy of big SS power amps. As amps got better, their output impedence went way down, increasing the damping factors, which usually leads to better woofer control near or below resonance. Also, with appropriate high pass filtering, efficiency is improved while avoiding the muddy low bass.

This might explain why the combination of JBL L-100s, 4310s, 4311s or 4312s with large vintage Crown Amplifiers such as the DC300AII, Power Line Four or PS-400s sound good.

There may be better JBLs (and I'm sure someone will make this point ) or amplifiers that some think are better, but THIS particular combination seems to work well.

[mike]

I would have to agree that it is probably the turntable rumble and lack of damping factor. If you are using a tube amp you will notice a lot of cone movement because of the lack of damping factor.

Those L100 woofers have some unique qualities and seem to last forever.

Mike