PDA

View Full Version : Yet another LE15 querry



Guenter
10-31-2006, 04:13 PM
I've recently bought a L200B cabinet and am about to fill it with some of my components - seems I never get around to finishing my own homebrew and the cabinet 'is' lovely. Anyway, I've got some Gauss 4582 (I believe) as well as JBL 2235H and 4 LE15'B' having '16' ohm. the quantities in the quotes are stamped on ... ie LE15 is on the foilcal and a space is left to put on .... I assume ... either 'A' or 'B' same for the impedance... the ohm is on foilcal and space is left for the #. On the cone is stamped 21518 and hand written (in white) is "B special". I've asked this before here, but there was no conclusive idea of what I have.... Anyone venture a guess??

I imagine I will stuff the cabinets with the 2235H ... for the mids I've got the LE85 with short and long horns ... from past posts I've obviously got to use the short horn. However I've also got the 375's as well as 4082's (phenolic diaphragm) .... would it be reasonable to use the 375's and then use my old LX5 500 Hz xovers?? I'm tending toward the 375's

For tweeters I've got either 075 or 077 .... I plan to go with 077's, BUT should I cut an opening in the baffle above horn or leave woodwork alone and place tweeter on top.... I'm tending to cut a hole in baffle but friend insists I'm being an idiot for cutting up the vintage woodwork ... any opinions???

any feedback and/or opinions much appreciated
- cheers, guenter

toddalin
10-31-2006, 04:32 PM
My view of messing with "vintage woodwork" but these cabinets were pretty busted up when I got them. And, the redo really brought up the WAF! ;)

I had always been of the impression that the closer the components are together, the better (pretty much). Also, there are some that say that the closer that you mount the tweeter and woofer to the horn, the less horny the sound.


http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/speaker1.jpg
http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/L200-2235.jpg

glen
10-31-2006, 05:12 PM
Anyway, I've got some ... LE15'B' having '16' ohm. the quantities in the quotes are stamped on ... ie LE15 is on the foilcal and a space is left to put on .... I assume ... either 'A' or 'B' same for the impedance... the ohm is on foilcal and space is left for the #. On the cone is stamped 21518 and hand written (in white) is "B special". I've asked this before here, but there was no conclusive idea of what I have.... Anyone venture a guess??

any feedback and/or opinions much appreciated
- cheers, guenter
Hi Guenter,

Well I just have to say....
:useless:

But seriously, you may have some early LE15s that preceded the "A" or "B" suffix.

I have an early LE15 from around 1960 that has the same "round-shouldered " cast magnet pot as the D130. Slightly later LE15s had the same "flat-back" magnet pot as the later LE15A. The LE15 and LE15A had the foam surrounds that stiffened up and often cracked over time. The later LE15B had the pleated accordion surround that did not decay. Even if your speakers have the "B" type cones they still might be reconed examples of the early LE15 woofers.

The blank impedance space is unusual, but not completely unheard of. There was a period when JBL changed the way they rated their driver impedances, going from "16" to "8-16" to "8" and I have seen some drivers that had labels like horns and did not list any impedance!

Because your LE15s do have unusual labelling it would be great if you could post some pictures of them, including some close-ups of the foilcal.

Zilch
10-31-2006, 05:18 PM
Cut the tweeter in, vertical in-line. See my avatar. :p

Anybody wants to make "pure" L200Bs outta them (though I cannot imagine why,) the hole can be blocked from inside, as JBL commonly did on other models.

The proper size circular hole saw will make a neat cut. :thmbsup:

Check your box tuning after the 2235Hs are installed. You may have to lengthen the duct a bit to optimize it....

Guenter
10-31-2006, 07:53 PM
thanks for the kind replies. Note, I've added the pictures as suggested... I know, a picture is worth a thousand words - thanks for that suggestion.
re the tweeters, the cabinet is lovely - great WAF I'm sure. I do agree that putting the drivers close together has many advantages. Nevertheless, re putting the tweeter above the midrange horn in the L200 cabinet is a bit worrisome since there is considerable ! cabinet overhang... can't be good for the sound, edge diffraction and all that. Might that be why some put the tweeter on top of the cabinet? However, since the tweeters don't disperse much vertically, the cabinet portruding edge may not be a problem.
After installing the woofer, I will take care re the tuning - good advice. From reading other posts I thought the 2235 would just drop in. BTW I can not see a tweeter cut-out on the avatar... what am I missing?

cheers, guenter

Zilch
10-31-2006, 08:44 PM
My reference to the Avatar is to assist in lowering your inhibitions regarding cutting into L200 cabinets. Mine are L200A, and I cut that rectangular hole in them to install PT waveguides.

I have thought about the overhang diffraction thing, and concluded that 077/2405H vertical beamwidth above 8 kHz is so narrow as for it not to be an issue. I suppose you could easily determine this with a protractor and the 2405H data sheet. I believe you'll find that, even if cut midway between the present horn and the lip, there will be no interference. Let us know what you determine regarding this for future reference.

Regarding the drivers, I know what an LE15B is, and might easily conclude that those are "special" in that the 16 Ohms (8 Ohms, actually, most likely,) deviates from the standard 6-8 Ohms version (4 Ohms, actually,) BUT those seem to have Lansaloy surrounds in your pics. LE15B would be accordian surround....

speakerdave
10-31-2006, 09:52 PM
I think Glen may be on the right track and those are very early LE15, the "B" stamped in to indicate 16 ohms as was done at the time with the 130A and B.

The mid-sixties catalogue in the library lists the LE15 as 8-16 ohms. It was the JBL flex-ohm impedance system.

David

Guenter
11-01-2006, 05:35 AM
I think Glen may be on the right track and those are very early LE15, the "B" stamped in to indicate 16 ohms as was done at the time with the 130A and B.

The mid-sixties catalogue in the library lists the LE15 as 8-16 ohms. It was the JBL flex-ohm impedance system.

David

David, thanks, makes a lot of sense. Especially in view that these woofers were used 'pair-wise' per side .... presumably to give the paralleled nominally then 8 ohm impedance for the LX5 xover that was used in the home brew cabinets. but what might the labeling of 'B special' on the cone be all about ... ? Might is just be a redundant indication that the coil was nominally 16 ohm?

cheers, guenter

Guenter
11-01-2006, 05:45 AM
My reference to the Avatar is to assist in lowering your inhibitions regarding cutting into L200 cabinets. Mine are L200A, and I cut that rectangular hole in them to install PT waveguides.


I have thought about the overhang diffraction thing, and concluded that 077/2405H vertical beamwidth above 8 kHz is so narrow as for it not to be an issue. I suppose you could easily determine this with a protractor and the 2405H data sheet. I believe you'll find that, even if cut midway between the present horn and the lip, there will be no interference. Let us know what you determine regarding this for future reference.

Regarding the drivers, I know what an LE15B is, and might easily conclude that those are "special" in that the 16 Ohms (8 Ohms, actually, most likely,) deviates from the standard 6-8 Ohms version (4 Ohms, actually,) BUT those seem to have Lansaloy surrounds in your pics. LE15B would be accordian surround....

Zilch, I'm going blind.... didn't pick up on that huge cutout on your boxes .. :-) re the diffraction, I tend to think the same and will likely go ahead and check this once the tweeter is installed with proper measurements ....

re the LE15's Speakerdave makes a lot of sense... however your point above is well taken and I had been thinking that the 'B special' hand written on the cone implied that it might be a proper LE15B with the Lansaloy instead of the accordian surround. Like I said, those drivers were used pair wise (along with two passives in a very large cabinet) in a home brew setup along with the LX5 and N7000 for the bullets.

cheers, guenter

glen
11-01-2006, 09:48 AM
... the "B" stamped in to indicate 16 ohms as was done at the time with the 130A and B.
David

Wow, I think you're right David. Of course the 130A & B were 16 and 32 ohms, but with exactly the same idea: the higher impedance "B" version allowing two woofers to be used in parallel to present the same impedance as a single woofer to the standard crossover.

Looking closely at the pictures it looks as if there are some scratches around the "6" of the stamped "16" next to ohms. Makes me think that the original printed "8" may have been scraped off to clear the way for the special "16" ohm designation.
(Thanks for the nice pictures Guenter!)


...these woofers were used 'pair-wise' per side .... presumably to give the paralleled nominally then 8 ohm impedance for the LX5 xover that was used in the home brew cabinets.
cheers, guenter

This is the only time I've ever heard of LE15s being used in pairs, very unique system you have there Guenter, can you tell us more about it's history, or how it came to you?


... but what might the labeling of 'B special' on the cone be all about ... ? Might is just be a redundant indication that the coil was nominally 16 ohm?
cheers, guenter

The cones would have been marked before they were installed in the frame basket. And they would have needed to be cleary distinguished from all the other LE15 cone/voice coil assemblies waiting to be mated with their baskets. These are the only 16 ohm LE15s I've ever heard of, I think they should have been labelled "B very very special"!



It was the JBL flex-ohm impedance system.
David

"flex-ohm impedance system" ?

Mr. Widget
11-01-2006, 10:54 AM
Hi Guenter,

If you have the ability to measure your LE15"B"s impedance that would be very interesting, if not, could you measure their DC resistance?

Those are definitely unusual woofers regardless of the impedance... since they only have LE15 printed on them, I am surprised they are not Blue in color... a very unusual set of woofers to be sure.


Widget

Guenter
11-01-2006, 12:46 PM
Hi Guenter,

If you have the ability to measure your LE15"B"s impedance that would be very interesting, if not, could you measure their DC resistance?

Widget

Hi Widget, I measured the DC resistance as 14.2 ohm with a few tenths of an ohm variation between each of the four LE15'B' that I have. I would assume the ac impedance will likely be a few ohms higher... at what frequency is the impedance measured anyway?

cheers, guenter

Mr. Widget
11-01-2006, 08:57 PM
14 ohm DCR is certainly higher than a LE15A.... and your lans-a-loy surrounded LE15"B"s have a much higher DCR and impedance than the standard "4 ohm" LE15B with accordion surround.

My guess is that the earlier supposition that these woofers were meant to be used in pairs seems correct... I wonder how many were produced. I have certainly never heard of them, seen them for sale on eBay, or read about them in any of the published JBL literature.

What frequency is the impedance taken at? I think it varies... I always take it in the crossover region. The nominal values that are typically listed for woofers are usually accurate in the 200-400Hz range.


Widget

speakerdave
11-01-2006, 09:01 PM
I wonder if they were made for the Texas bookshelf project?

David

Edit: I think the 14K serial number may work with that. I have some generic lansaloy LE15A's that are in the 9K range. The serial number would not seem to fit with my earlier assertion that they might be early versions. Perhaps it was possible to make changes in the foilcal for a small run during a special product development.

speakerdave
11-01-2006, 09:37 PM
What do you know about their history?

David

ALTEC GENIUS
11-01-2006, 09:47 PM
AMAZING I LOVE THEM:) :applaud:

glen
11-01-2006, 10:38 PM
Hi Guenter,
Those are definitely unusual woofers regardless of the impedance... since they only have LE15 printed on them, I am surprised they are not Blue in color... a very unusual set of woofers to be sure.
Widget

You're right widget, if these were plain LE15s they would have had blue frames. I also have not seen an LE15 with a serial number higher than 1372.

These started life as 8 ohm LE15As and originally did have the "A" printed after the LE15 and an "8" for the impedance. That's what is appropriate for serial number 14206. Besides the serial number this label also displays the condensed typeface of the "LINEAR EFFICIENCY" legend, the letters being tall and skinny. The earlier 16 ohm LE15s and LE15As had "LINEAR EFFICIENCY" letters that were almost as wide as they were tall.

Here's a progression of the LE15's evolving form,
and the highest and lowest serial numbers I've seen of each:

LE15 rated at 16 ohms, cone marked LE15-111, blue frame
serial number 1057 to 1372

LE15A rated at 16 ohms, cone marked LE15-111, blue frame
serial number 2110 to 4424

LE15A rated at 16 ohms, cone marked LE15-111, gray frame
serial number 6111 to 8371

LE15A rated at 8 ohms, cone marked 21315, gray frame
serial number 9117 to 29149

LE15A rated at 8 ohms, cone marked ?, black frame
serial number 33405 to 37363

LE15B rated at 6-8 ohms, cone marked ?, gray frame
serial number 10294 to 20667

Guenter
11-02-2006, 06:51 AM
What do you know about their history?

David

First let me say, Glen was right on the money! carefully inspecting all 4 drivers (consecutive serial #'s of course - probably confirming a 'special order') the drivers 'all' display fine scratching around the 6 in '16 ohm impedance'. Sure looks like they removed the '8' that was likely there initially. However, there appears to be 'no' similar scratching around the 'B' to indicate previous lettering.... note though that space was apparently left there in anticipation for something to be imprinted there... ie look at the left right balance wrt the foilcal. In all other pictures of the LE15 series the line is centered with or without additional lettering to LE15. The cone itself has 21513 printed on the reverse side (not 21518 as I thought earlier). Is it a fluke that Glen's have 21315 on the cone... ie '21 5 13' vs '21 3 15' ???

The history I'm only vaguely aware of. I'm 'guess-estimating' that they're from the early 60's. They originally came from a doctor in Toronto who clearly loved JBL's ... the good man got divorced and his Sovereigns (with matching equipment cabinet) remained with his wife. Appears he moved into an 'upscale' bachlor pad. (Aside, his wife used the Sovereigns as plant stands in the basement for 'many years' and then donated them to the Church for a Bazar sale when she was cleaning (selling) house. The doctor in his bachelor pad had limited space and consequently he had a S8R system with double woofers/passives custom build into a custom cabinet which in turn fit into his wall unit. The cabinet was only deep enough to accomodate the 375's (a foot or so) but must have been 6 ft x 5 ft or more otherwise.

The good doctor passed away and the speakers were used up in cottage country (Muskoga) for years and eventually ended up in the doughters basement as 'TV' speakers .... sounding awful of course since the Lansaloy had dried up and they were driven by a Radioshack 10W receiver. the cabinet is history and I've cleaned the drivers and am now wondering what to do with the woofers.... I do have a 4335 project on the go (my present home brew looks 'much' like Widgets) but seem to find precious little time to get on with it. Well, retirement is not 'that' far away :bouncy:

cheers and thanks all around for the truly great sleuthing

guenter