The JBL L 7's I now own are my second pair.
The first pair did not work out for me.
This second pair sounded a LOT better.
I also own B&W Matrix 801's as a reference speaker.
I heard problems in this second pair of L 7's immediately.
Cat Stevens and Bob Seeger revealed what I THOUGHT to be insufficient damping material behind the drivers.
I about drove myself crazy adding, removing, and trying various amounts and types of damping materials.
After speaking with the ex JBL engineer who designed these speakers, I realized the problem is NOT in the upper two cone drivers.
What I was hearing is the upper range of the side mounted woofers!
He told me these should be a generous amount of fiberglass behind the side mounted woofers, and to check to see if it was installed per his specs.
Sure enough, it was NOT!
So, I pulled out the totally useless 1/2 inch fiberglass sheet the factory installed.
In it's place, I placed the 2 inches of fiberglass, being careful NOT to block the port.
I listened again, better, much better, but STILL I could hear the upper range of the driver.
So, I undid the woofers again, and stuffed some additional fiberglass up into the top of the cabinet.
There is a hole leading from the woofer chamber into the top of the cabinet.
I LOOSELY filled this hole with some additional fiberglass.
This did the trick!
No more Chesty sound on Cat Stevens or Bob Seeger.
Are the L 7's a B&W Matrix 801 ?
Not in this lifetime, but I like them a lot still.
The bass did not seem to suffer by adding the extra fiberglass.
If anything, it got tighter.
Once this woody, chesty sound is gone from the L 7, they really open up.
Imaging is FAR better, and it just plain sounds better, top to bottom.
If YOU own L 7's, you NEED to CHECK the damping behind ALL drivers!
Mine were ALL wrong, according to what the designer of these speakers TOLD them he wanted.
Just a couple of hours time, and you can have your L 7's sounding the way the designer INTENDED them to sound.