MCM speakers JBL LE8

[Omegaman]

I got these speakers awhile ago and they sound like crap. No bass
They were installed in a 1960 MCM home near Tucson

I bought 4, sold 2 on eBay and want to use the other two myself

I like the cabinets which were manufactured by the J W Davis company of Dallas, TX
The original lansaloy surrounds are hard as a rock
I tried the DOT 3 treatment but no real improvement




I ordered new surrounds

 

[maxhifi]

Those look like the kind of PA cabinets which aren't made for specific speakers, but rather for a specific size of speaker.

You should try and get some JBL documentation on what their recommended cabinet was, no bass makes me think the ones you have now are way too small.

 

[Omegaman]

Here is some documentation on the drivers


Says 1 cubic foot, so the cabinets should be okay. The cabinets are ported

Its the surrounds that are causing the no bass. A definite maybe for sure

 

[Ghonk]

I think the hard surrounds probably has something to do with the lack of bass.

 

[Omegaman]

I think the hard surrounds probably has something to do with the lack of bass.

Once I get the new surrounds installed we will know

I read nothing but good reviews about these drivers with the whizzer cones

These were the two I sold

 

[gizzyman47]

Looks like a fun project!

 

[darkhosis]

I had a set of the JBL C53 Libra with the LE8 and passive radiators option. I had the same reaction. I decided to sell them instead of trying to soften with brake fluid. The buyer was extremely grateful to get untreated speakers but I've always been a little curious how they would have sounded originally.

 

[Omegaman]

Wow that was a lot of work to get the old surround off


Its better than it looks. It is intact just still wet from the solvent

 

[Omegaman]

Here is the inner surround edge all glued in place
Gluing the surround on the underside of the cone is definitely more of a challenge


I find the glue spreader sticks pretty useless

 

[Omegaman]

To help align the voice coil I have this CD that plays a constant 30Hz tone

 

[Omegaman]

First speaker all done


Just let it cure overnight

And onto the second one

 

[Omegaman]

Like babies and marriages
The second one is usually easier

This is the best way I could find to remove the surround from the cone

It only took a small layer of the cone off and left it perfectly usable

 

[Omegaman]

And done


Only thing left is "How do they sound?"

 

[onwardjames]

Damn! What a difference from the first one to the second one.

So, let us have it....how do they sound??

I don't have much faith in those cabs, sad to say. Seem far too small.

 

[Omegaman]

The second one had been lightly painted to not show the cone or dustcap so it looks more uniform. I cleaned the paint off the dustcap, hey they're JBLs right
The first one had a small repair to the Lansaloy surround so there was some glue residue on the cone
But they both came out very nice and the both sound great playing 30Hz

I had a little scare. I measured the Ohms and one measured 7.4 and the other measured 26 ohms. So i pulled the driver out and the driver read 7.3 ohms
Hmmm after some debugging it was revealed the probe tips on my meter were loose

They are rated at 16 ohms

I got to let them fully cure before I power them up

 

[GordonW]

Those LE8 drivers need either a ported (vented) box or a passive radiator, to have much bass.

1.75 cubic feet tuned to about 35Hz will work well with them. That would take a 3" diameter vent, 6.5" long, per cabinet. Or, a 2" diameter vent, about 2.5" long per cabinet.

Regards,
Gordon.

 

[Omegaman]

Thanks guys, You know more than I do on the subject

The boxes are ported
In the first post you can see the port behind the driver
At least they have new surrounds

I guess I could make a pair of C48 Madison cabinets

 

[Omegaman]

Okay I listened to the JBL LE8 speakers in the cabinets

Good news. The refoam worked great no voice coil rub and they play very well with improved bass

They no longer sound like crap
I am not ready to give up my Altec model 14's

They seem like they would make pretty good mounted test speakers but the drivers deserve better

They need need bigger cabinets