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dennis j leisz
01-01-2004, 09:48 AM
Greetings, What is JBL's recommended frequency operating range for the LE14H-1. Highest recommended crossover point? How would a pair of these work with an 2344 horn with the 2426 driver in an MTM configuration? Happy New Year, Dennis

Mr. Widget
01-01-2004, 11:44 AM
Recommended and ideal are two distinctly different things. While the LE14A which is very similar to the LE14H-1 was used to 2500Hz in the 60's and 70's, today we demand better performance from a system.

While the LE14H-1 will put out higher frequencies, it like any 14" driver will be very beamy above 800Hz-1000Hz. More problematic with using any of the LE14 series woofers is that the massive coating of aquaplas that allows the various LE14s to produce prodigious bass tends to cause them to be less than ideal at higher frequencies. In the JBL K2-S9500 they use a very different 14" driver, the 1400ND. This driver has better mid-range performance and yet they still use a 650Hz crossover point.

This crossover frequency requires a horn that has a significantly lower cutoff point than the 2344. If you could find them I think a better bet would be to use a pair of 12" 2214H woofers. (The woofers from the 4425.) These woofers should work very well with the 2344 and 2426. In any case a significant amount of crossover tweaking will be in order to get this sort of system to work well in an MTM configuration.

Sounds like fun!

GordonW
01-01-2004, 01:57 PM
Ditto what Widget said... if you had a horn with an 800 Hz or lower cutoff like an old Altec 811 or 511 (especially the 500 Hz 511), I'd say go for it, it'd probably work. But with a crossover over 1KHZ, it's gonna be dicey ESPECIALLY with an MTM... the center-to-center distance is pretty hairy for a crossover that high, even if the drivers themselves were perfect up there...

Regards,
Gordon.

Don C
01-01-2004, 06:06 PM
In the 240Ti the crossover is 900hz, in the L250 and 250Ti it is 400hz Then for the 250Tibq it is listed as 350hz

GordonW
01-01-2004, 08:33 PM
Well two things:

First, the closest thing, IMHO, that a 240Ti has to a "weak link", is the upper midbass/lower midrange region "snap". The 250Ti, with its crossover an octave lower going into the 8", was a lot better ti my ears. The LE14 to me, is optimal up to about 500-600 Hz.

Secondly, even if the 14" drivers are OK out to beyond 1KHz, he's wanting an MTM... that means a woofer center-to-center distance of like, a foot and a half, with a horn in the middle! That would dictate that you really wouldn't want the crossover point higher than about 660 Hz or so... since that's a wavelength at that frequency. Even 800 Hz would be pushing it a bit, probably would still work, just would take some careful tweaking and such...

Regards,
Gordon.

4313B
01-02-2004, 11:07 AM
"First, the closest thing, IMHO, that a 240Ti has to a "weak link", is the upper midbass/lower midrange region "snap". The 250Ti, with its crossover an octave lower going into the 8", was a lot better ti my ears."

Well, the LE14H-1 lacks the ubiquitous "rising response" found in so many JBL transducers so that could be why one might find a system such as the 240Ti lacking. I personally like the 240Ti because it is so easy to sit and listen to.

Granted the 250Ti is a step up. The 108H in the 250Ti is a 2118 with aquaplas sprayed on the back to smooth out and flatten it's response. The LE14H-1 has a very nice smooth response with a fantastic roll-off, free from excessive peaks and dips.

You could try an MTM configuration but I think you would do best to follow the posted advice to limit the crossover frequency to ~ 650 Hz. Your filter would probably have to be shallower than it would be for the 1400Nd. LF response would be quite a bit better but as has been stated, midrange response might not be up to what you're after.

Current practice is to use systems such as the K2-S9500 right out of the box "as is" and then add in LF EQ as required/desired. This is in contrast to using older transducers such as the LE14H-1, 2235H, or 2245H with their extended LF response but comparably lacking transient character through the midrange. The 1400Nd has other characterisitics, such as lower distortion and lower power compression, that add to it's overall superiority over the LE14H-1, especially in a K2-S9500 type application. For LF and VLF applications though I would have to stay with the LE14H-1 or LE14H-3.

Now, a pair of K2-S9500's biamped to two twin LE14H-3 sub systems...

dennis j leisz
01-02-2004, 01:31 PM
Thanks to you all for the info. I have 4 LE14h-1's looking for an interesting application. It doesn't appear the MTM approach is feasable based on the specs. I will continue brainstorming . Any ideas? Dennis

GordonW
01-02-2004, 09:06 PM
Well, if you can use a 500 Hz horn, I wouldn't give up on the idea. Two LE14s will have pretty darn decent efficiency together, and with a PAIR of them, I'd doubt you'd have to drive them with enough power to induce much compression.

Giskard, WRT the 240 vs 250Ti... it wasn't the frequency response I found lacking in the 240... it seemed perfectly well balanced. It was the fact, that the transient response of the 250 was better in the region of snare drum hits, rim shots and such... which I deduced was due to the superior ability of the smaller 8" driver to accelerate on transients, without either "rounding off" the transients or "overhang" This, I attribute to the 8" being better at HF transient spikes... even with a crossover, there's SOME upper midrange going to the woofer of the 240Ti, which would be going more to the 8" in the '250...

However, with a 500 Hz crossover, I'd expect the whole transient issue to be fairly moot... IME, the LE14 is quite fine up to there...

Regards,
Gordon.

Earl K
01-03-2004, 05:02 PM
Hi Dennis

Others have already said it , but I'll repeat it, try your le14s in some sort of MTM setup. At the very worst, it'll be a very enlightening experience. I'd suggest a cabinet size of 3 to 3.5 cu ft tuned somewhere in the 30 to 35 hz range.

I use a le14h ( right now in a 2.8 cu' cab. - my next test box will be sized for 3.2 cu' apparent volume) with a le10 on the top ( in a .65 cu' cab. ). I found the heavily aquaplased cone ( 140 g Mms ) of the le14 produced a pretty "wooden" midrange from 150 hz on up. This wasn't to my liking. The aquaplased cone of the le10 really meshes nicely with the timbral makeup of the le14 ( a,h or h-1, I have some of each ) . The ten does have a livelier midrange ( afterall , the 10" cone is maybe 100 grams lighter - while still being driven by a large 3" voice coil ) . Once in a while I substitute in a 2123 or a 2012 - but I keep coming back to the homogenous sound provided by the two aquaplased cone types. The 2 le type speakers run paralleled together. The other midrange 10s need resistors added to balance them to the less efficient 14" woofer.

Center to center measurements for these two speakers is 22".

I use a 2450Sl diaphragm in a 2440 motor on a round mouthed Selenium horn. The 2450SL diaphragm is also aquaplased.

Crossover point is @ 800 hz ( electronic - 24 LR slopes ).

As it happens, my system seems to satisfy one of the criteria for successful MTM implementation. That criteria ( liberally interpreted ) is an absolute 90 phase difference between the middle tweeter (horn) and the surrounding midrange. It seems I lucked into this by having the horn-drivers' voice coil, offset ( behind the woofers ) by just about an exact 1/4 wavelength measurement of the crossover frequency. This is 4.25" at @ 800 hz . This phase offset seems to be very important - I've heard a lot of soundstage depth of field "flatten out" when an additional 90 of phase is switched into the circuit ( via DC blocking caps ). Electronically, Time-Aligning the woofer to horn produces a different sort of cohesion that is quite different than the sense of depth generated by the 90 offset . This all seems to work well with my small exponential horns - I suspect CD style horns will have a different mechanical measurement point since each horn type has a different apparent apex ( or acoustic center ).

Worth reviewing is Dons 12/19/03 update in the private Lansing Speaker Project. Some intriguing info from there ( regarding MTM stuff ) is the inference ( somewht between the lines ) made by Mr. G Timbers (& relayed by Don ) of just how certain MTM attributes will still dominate the MTM setup - even when other, seemingly "iconaclast" rules/or criteria are bent ( such as woofers having to have, equal frequency content ). Asan example, my woofers don't produce the exact same frequency content, but they still produce a good point source ( as long as the db difference, between the woofers isn't too large, @ a difference of 3 db over the top 2 octaves seems to effect a focal breakup ) .

Hopefully, a lot more of this sort of MTM info will become accessible as that project matures.

Anyways, enough blather, do try the MTM setup with at least a pair of your 14s'. At the very worst you'll gain a pair of very useful subwoofer boxes .

regards <> Earl K:)

4313B
10-05-2004, 01:46 PM
LE14H and LE14H-1