JBL LE5-2 in LE5-2

[Yasnyi-Sokol]

Hello,

Is there any closed rear chamber behind LE5-2 midrange driver in L100 speakers (which separates the space from the main space with LF driver)? Or both are physically mounted with the common rear space?

Similar question for LE20-1 in older L100 model -does it need rear chamber?

Thank You

Alex

[4313B]

The LE20 and LE20-1 are closed backed and do not require a subenclosure. All the LE5 models require a subenclosure and the specified volume is 80 cubic inches.

[duaneage]

13 cm diameter tube approximately 12 cm deep should be good enough.

[GordonW]

The newer model L100 (with the LE25 square-flange tweeter) uses an approximately 5" (12cm) depth chamber... BUT- the early model L100 (with the LE20 round-flange tweeter) uses a LONGER chamber, of approximately 8" (20cm) depth.

It's important to get the correct chamber length, for the crossover you are using. The long chamber goes with the more complex early model L100 crossover, the short chamber with the simpler L100A crossover. Otherwise, the midrange will not blend with the woofer correctly...

Regards,
Gordon.

[4313B]

Let's get actual physical dimensions.

It would be nice to get impedance curves run of the LE5 in both chambers as well.

[duaneage]

In my 4411 clones I have 89 cu inches, - about 10 for the magnet and the resonance peak is still the same at around 240 hz. The crossover frequency is 1100 hz so this is well above the FS of the midrange. If the FS is at least 3 octaves below the crossover point and the slope is 12 db/octave it should be OK.

[oldisgood]

I had asked a similar question in another thread without a satisfying answer. The JBL component series instruction manual from 1980, posted elsewhere here, also recommends 80 cubic inches, typically 4.5 internal diameter by 5 inches deep. However, all the L100s and 4311s I have opened up have much smaller midrange chambers, about 4.090 ID by 3.25 deep, or about 42 cubic inches before stuffing. Why would JBL undersize, by almost a factor of two, the midrange isolation chamber in these? If you look at how much space the back of the LE5-2 takes up, combined with the acoustic stuffing, there's almost no airspace there. Let me know if you have any good thoughts about this.

[4313B]

Let me know if you have any good thoughts about this.

I really don't want to think about it. I want to see an impedance curve.

[oldisgood]

Sorry, Giskard, I don't (yet) have that capability, and was hoping the exact dimensions I provided would help the cause. Perhaps another member will ride to the rescue with impedance curves.