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In Reply to: Re: Looking for some JBL help/suggestions posted by Tom Brennan on February 11, 2007 at 11:08:52:
Thanks Tom, I tried that & got only one response that was vague & not very helpful.Maybe I'll try again.
Follow Ups:
Matt---In the JBL library section of the Lansing site there is a section with plans, there is a section there called "1975 plans" that shows plans for enclosures using the LE 15A including enclosure volumes, proper venting and suggested layouts.I think (though I'm not sure) that the LE 15A was used in the L-300 speaker. If you search the forum at Lansing site using "DIY L-300" and "LE-15A" I think you'll find some information. If you have L-15Bs those were used on the L-200, I don't know if there are plans or information on the L-200 on that site.
Hi Tom, how's it goin'?Actually, the L300's used 136A's (or 136H in ferrite). Much less efficient than LE15A's, but go pretty deep w/ authority in a moderately sized box. I use 136A's, they're a good compromise for my space/system.
I'm pretty sure there are good le15a box designs at the lansing heritage site; I've seen some; fairly large IIRC, but nothing obscene.
For horns, I like Dr Edgar's 'salad bowl' wood tractrix horns. They're simply incredible with 375/2440's.
Thanks, I"ll do that.
They were used in the L200 BR cabinet. I would put a HF on top of the 375's.
I also have a pair of 16 ohm 075's would they work for HF?
The whole thing is fairly arcane, so you're going to have to do some studying I'm afraid.I assume when you say you have the "throat and lens" you are referring to the very short horn, about 4" long, throat 2" diameter, mouth 4" diameter. It was used with a slant-plate lens about 10" wide. This is pretty classic, and was often used with the 075 "bullet" tweeter and the N8000 crossover. I think you have the makings of a really classic vintage system and it would be a pity to muck with it.
Note that this is old enough that the "16 ohm" speakers may actually be 8 ohms. Check the voice coil DC resistances to be sure. The N500 crossover may also be labelled 16 ohms but otherwise identical to the later 8 ohm version. Like I said, all this can get pretty arcane.
The woofers are something special, one of very very few underhung designs with reasonable excursion. There were quite a variety of surrounds at various times (one oddball "plastic" that hardened up as it aged, and supposedly can be rescued with automotive brake fluid ...) so a little research may be needed to make sure it's in good shape.
The 375, if it has the original diaphragm, will go up to 8 or 10kHz. But many later diaphragms will fit (not all, of course - arcane, remember?). The aluminum ones are said to sound better, but they are subject to fatigue cracks if over-stressed.
"I also have a pair of 16 ohm 075's would they work for HF?"Yes. I used those in 2-ways and liked them. Some would find them somewhat soft and rolled off on top but I liked the way they did the job. They worked well on several horns I tried---Altec 511s, McCauleys with lenses, JBLs with lenses, Edgar saladbowls.
AB----The L-200 used the LE-15B which is a different animal than the 15A. Our friend must first make certain which he has.Then the L-200B used a different woofer, knowledge of the model number of it being too arcane a JBLism for an Altechie like me. ;-)
The woofer just says LE-15 would that make it an "A" The serial #'s are 1225 & 1226. They are in dark blue wrinkle paint & are 16 ohm.Thanks again
Matt---What kind of surround? As have a half-roll surround and Bs have a corrugated cloth.
They are a white cloth surround.Thanks,
Greets!'A' series, which IIRC was optimized for ~8 ft^3 sealed cabs, but any of these old low Fs/Qts drivers perform well in Vb = Vas, Fb = Fs vented alignments and increase the amp's and/or system's output impedance to flatten it in-room as required. If this is too big, then ~Vas*0.6 tuned to Fs is an acceptable trade-off between size and LF gain BW for most folks with space and/or WAF issues. As box size shrinks, then either you'll need a corner to gain back the lost acoustic efficiency or raise Fb to compensate.
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