LE15 & PR15 vs. 2 x LE15?

Forum members,

this is my first real post on the forum, I find it a great source for information and inspiration.

My question relates to optimal use of LE15As/PR15s I have access to. For each enclosure I can either use one 8 ohm LE15A in combination with a PR15 or alternatively two 16 ohm LE15As (total load 8 ohm), and no PR15. I plan to use an active x-over, so impedance load on the x-over is probably not an issue. The rest of the setup will be one 2421B and one 2405 pr. enclosure, and a 3-way active crossover (crossing over @ approximately 800 Hz and 7-8 kHz).

What do you consider the advantages/disadvantages of the two LE15 setups? I'm trying to keep my enclosures at a reasonable size, so that will be an issue to consider. What would be a good enclosure size for two LE15As, they would probably require a ported enclosure? With the help of a friend and his equipment I'm able to tune the enclosures/ports.

I would appreciate any recommendations, advice or comments.

Thanks, and best wishes,

Sigurd
(S.O.Stefansson)

Welcome Sigurd,

First point: This has been discussed to death on the forum, but the "8 ohm" and "16 ohm" labeled LE15As both have the same voice coils and are identical in every way except the printing on the foilcals and in some cases the color of paint. (This is not true of the professional versions labeled 2215A and 2215B. These really do have different impedances.) If you want more info do some searches on this forum.

Second point: The LE15A with the PR15 adds some mid bass warmth. Many people like this and others do not. In theory the passive radiator acts as a tuned port, but in practice the PR15 does have a different sound than the LE15A alone in a tuned box.

Third point: What is your ultimate design goal? I was using a pair of LE15As each in it's own 5 cu ft box tuned to 30Hz. (four woofers total) The results were good but I was always disappointed with the extreme low frequency extension. I later upgraded to a pair of 2235Hs in the same enclosures and the bass extension was markedly improved. Today I would suggest using a 2234H in one cabinet and a JBL Sub1500 in the other cabinet. I use the Sub1500 in a 21Hz cab and it is nothing short of remarkable.

I think your 2421 and 2405s actively crossed over should give you a very nice top end. If you could get an active crossover that allows a 10KHz crossover point I think that would be better than the 7-8KHz, but many are happy with the 2405 at 8KHz.

I hope this helps.

Widget

Mr Widget,

Thanks for your constructive comments and for reminding me about the various threads discussing LE15 impedance. I've looked at them before, but somehow didn't quite connect them with the labels on my own drivers.

I should have mentioned that one of the two '16 ohm' LE15A pairs have been measured by my friend 'Flodstroem' (also on the forum) and they are indeed 16 ohm (the have been reconed probably using a C16R2215 cone). I think their DC resistance was around 9 ohm. The other two pairs are both original, one pair labeled 8 ohm (grey frame), the other 16 ohm (blue frame).

What you are saying is that both of these original pairs (despite their labels) are probably 10 ohm drivers (according to Giskard's previous list and comments)?
Hmm... I guess the next question is what happens if I try to combine one true 16 ohm LE15 and one 10 ohm LE15 in the same enclosure? Is it possible to combine drivers with different impedances this way, powered by the same amplifier? I clearly don't know enough about the physics involved.

Now, what I'd like to achieve with these drivers (or driver + passive radiator) is a dynamic, neutral well-defined bass sound. I don't necessarily have to cover the very deepest sub-bass notes, as long as the sound I get is 'true', ie., bass when there should be bass, and not a blurry undefined bass. Perhaps 'definition' is the word that best describes what I'm trying to achieve.

I hope this makes sense, and I look forward to hearing from you (and maybe other forum members) again.

Sigurd
(S.O.Stefansson)

Here's a bit of historical detail on the LE15's to muddy the water even further. After JBL made the conversion to 8 ohm labeling of the LE15A, but before introduction of the L200 and its unique LE15B, JBL supposedly used the designation LE15B to describe a true 16ohm version of the LE15A that was available as a custom order.

Don:

My brother and I just bought 4 L200 Studio Masters in very good shape, I will post them later; The woofers are LE15B, and they have accordion pleated surrounds; Are these original?.

Alex.

Quote:

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Originally posted by Don McRitchie
Here's a bit of historical detail on the LE15's to muddy the water even further. After JBL made the conversion to 8 ohm labeling of the LE15A, but before introduction of the L200 and its unique LE15B, JBL supposedly used the designation LE15B to describe a true 16ohm version of the LE15A that was available as a custom order.

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I bleieve Don is right on the money. I'm one of those with a LE15A just like that. Finally managed to come across an old JBL salesman in Toronto. He appears to remember that people wanted bigger bass and some wanted to double up on their
woofers. So JBL made available special orders of LE15A's but with
try 16 Ohm coils so that existing x'overs etc could be used. I know I've got 45 of them and been trying for quite some time to
get their lineage straight. Particularly confusing is the later
designed pleated LE15B's that were redesigned from the ground up.
I am using 2 of these in parallel per side and like the sound
very much. I don't miss the infrabass, most of my music doesn't have much of this on them anyway. Love the sound with the PR.s
the only problem I have is that they have pleated surrounds and are not compliant enough; ie the foam is more compliant and, if anything, it should be the other way around.

cheers

Giskard,

I'll get the pictures posted in a day or two.

Thanks,

Sigurd
(S.O.Stefansson)

The trick with the pr15 is to get the right weight on the cone.
Too little weight and there is a pronounced peak at 250 hz.
Too much weight and there is a dip at 250 hz. Just the right weight and bob's your uncle. Smooth from 40 to 600 hz. Two jbl cardboard weights in a 6.25 cubic foot box is just about great. Of course I am biased.

John

Quote:

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Originally posted by Alex Lancaster
Don:

My brother and I just bought 4 L200 Studio Masters in very good shape, I will post them later; The woofers are LE15B, and they have accordion pleated surrounds; Are these original?.

Alex.

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Hi Alex

Those would be original. The LE15B as used in the L200A were based on the LE15A chasis, but used a lighter cone, an underdamped suspension and pleated surround.

Don

Thanks Don, We are cleaning and re-oiling them; they are in remarkable shape for 30 years, even the grill cloth, after I test them, I will post the pictures and the little story.

Alex.

hi lansing fans!my project is a 12cubic feet cabinet,and 2 le 15a per side,would someone help me with the ducts dimensions?

Hello

Try this, it is free box program. You will be able to figure it out for any box size. The Le-15 comes as a preloaded driver.

http://www.linearteam.dk/default.aspx?pageid=winisd

Rob:)