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View Full Version : What to do with LE-12c Coaxial Woofer



Rmac587
01-07-2017, 08:11 PM
Hi All,
I recently lucked into a pair of coaxial LE-12c that were part of a DIY 3-way set using the 12c, a 5" Jensen mid, and a Rat Shack tweeter.

The LE-12 went directly to the speaker terminals and used the native JBL xcover attached to the frame, while the Jensen mid and RS tweet had an "over the counter" RS crossover also going to the cable terminal. As odd as it sounds and as cosmetically HORRIBLE as speakers and the woofers were, they sound great.

http://audiokarma.org/forums/index.php?threads/speaker-id.749938/page-3#post-10190097

I'd love to keep these and clean them up and put them to good use, although I should be acquiring some L112 soon as well.

The literature says that the C-34, 36, and 56 cabinets were suitable of the 12c with the appropriate adapters (basically some sort of board that allows the woofer to be used with cabs that have various configurations such as a 14" woofer cutout).

The 12C require a 4'-6' cubic foot enclosure. I've been searching for any type of vintage box I could fit them in, keeping in mind my very basic wood working skills.

Here are some solutions I've considered:
1-An open baffle with a closed back mid-range added in, not sure it would work. Keep in mid the LE-12c incorporates the LE-20 tweeter and has its own enclosed two-way crossover attached to the frame. I could add a better capacitor to the old RS xover, use it for the mid only, then terminate both the mid and LE-12 at the speaker cable terminal (kind of what previous DIYer did).

2-Another idea is just to have someone build simple cabinets for me out of plain MDF. In that case I'd like to keep make the external cabinet no deeper than 12“ so I can use some left over walnut veneer rolls I have. Is that depth ok as long as the total volume is the same?

Also, I noticed that some of the old JBL cabs had multiple configs possible in the same box. Couldn't I have the baffles made with extra driver cutouts in case I want to try different driver combinations, i.e. run the LE-12c solo, run it LE-12c plus a mid, or “3-way" with the LE/plus mid/plus another tweeter (the current DIY config)?

I do have an LE-5-6 mid and would only need one more in that case.

3-If anyone in SoCal has cabinets that would work I'd be interested, but the cabs I have seen on C-list and FeePay cost more than really nice custom jobs would.

I'm excited about this find, but a bit intimidated. I'm ready to go back the JBL sound I had when I briefly owned a pair of 4311. Lordy, it was magnificent, full, and powerful.

I've been running a beautiful pair of modded Klipsch Forte I, but I think JBL floats my boat more.

FYI, I have 3 amps: Rogue Audio v.2, a rebuilt Sansui AU-717, and a back-up unit, Carver MXR-150. I may sell all and upgrade to separates or tubes.

Mech986 has been super helpful on the AK website, but I thought I'd run it by a JBL specific site where there are multiple fanatics, I mean fans, to draw upon.
Much obliged ya'll!

speakerdave
01-07-2017, 11:20 PM
The design goals of the LE12C are to provide rudimentary access to recorded music, and frankly could not really be considered hi fi. The ad hoc speaker system you fell into is testimony to someone's frustration with it. If I had a pair of them and nothing else to fill the role, I would use them as is, with no additional drivers; they would be fitted into simple cabinets following instructions in the 1970's enclosure manual to be found in our library, and they would be connected to a modest receiver and set someplace where background music is desired. To expect anything else from them is to be fatuously unrealistic. The LE 12C is not a good choice for a party speaker because it's main shortcoming besides the lack of VLF and UHF is the lack of midrange, and in a room full of people you want lots of midrange. The woofer section I believe is identical to the 4311 woofer, the speaker you mention, so I can understand your excitement, but that will be the only similarity. There are photos of this driver fitted into the woofer hole of the C56 Dorian cabinet using an adapter plate. You could do a similar thing if you could find a flipper in your area with some empty L55 cabinets. It might make a good first speaker project for you to find a way of usefully deploying those drivers, but I suggest raising your sights with a system which will be more likely to give you a longer term payoff. I wish you luck with your stereo ambitions.

Rmac587
01-08-2017, 07:00 AM
I kind of got that impression from what Mech986 said on another forum. It's very similar to the 2145 which is meant for commercial applications. I don't think the LE-12 are quite as bad as all that though. I've seen some videos of the same woofer in a simple enclosure with decent amplification and they seemed to perform quite well. (https://youtu.be/uQuIn-D0Nbs). The raggedy three-way DIY configuration they were in was surprisingly good too through my Sansui, but as you note it could indicate someone's prior frustration. The ears are the ultimate arbiter.


In any event it sounds like a good way to experiment with low risk. I got into audio about six years ago when a friend of mine sent me a couple of his older mid five pieces. Since then I've been continuously cycling through gear that I find. I have to self-finance this habit.


I swore a few months ago I would sell everything I have and use that money to do a substantial amp upgrade with JBL's and another system with my floorstanding Klipsch that I modded. It hasn't worked.
I can't quit.

Thanks for the input!

BMWCCA
01-08-2017, 07:28 AM
I've seen some videos of the same woofer in a simple enclosure with decent amplification and they seemed to perform quite well. (https://youtu.be/uQuIn-D0Nbs). Performed well in a YouTube video? Were you listening through your laptop speakers? You do realize how meaningless that is, don't you? :D

Rmac587
01-08-2017, 07:43 AM
Performed well in a YouTube video? Were you listening through your laptop speakers? You do realize how meaningless that is, don't you? :D
LOL! I can't say I didn't know that was coming! Apple TV>NAD DAC>Rogue Audio Amp>ADS speakers. It's all I got to go on!

Actually I did disconnect the other two drivers in the 3-way DIY and run just the LE-12c through its native crossover. They were ok. Amplification wasn't great though. Garage amp.

I've been thinking about what made my limited JBL experience so compelling. The descriptors that come to mind are "warm," "powerful," and "articulate."

Mr. Widget
01-08-2017, 04:19 PM
LOL! I can't say I didn't know that was coming! Apple TV>NAD DAC>Rogue Audio Amp>ADS speakers. It's all I got to go on!The internet can be an amazingly useful tool, but... come on! How could you, or apparently lots of others think that a recording of a speaker playing in a room will give you any sort of useful info about it's actual audio performance? I don't care if the recording was made by a professional with studio mics and state of the art recording equipment and even if you have a class A playback system, none of which is typically the case.

If you think about it for two seconds, it is pretty obvious. That said, it seems that thousands of people somehow think YouTube recordings with unknown recording techniques will offer a useful glimpse into the sonic performance of all types of audio equipment. It is kind of like a beautiful photo of food with a scratch and sniff panel giving you an idea of how good a dish tastes.

Anyway, enough of that. I have never used a JBL LE-12C, but the two components are meant to be identical to the woofer and tweeter of the original Nova 88... which are the same in the original L100 minus the LE5 midrange. I would think if you added an LE5, duplicated the fairly simple network of the original L100 (http://www.jblproservice.com/pdf/Network%20Schematics/3112%20Network.pdf), and copied the cabinet and port you would likely have a satisfying result.


Widget

Rmac587
01-08-2017, 04:42 PM
The internet can be an amazingly useful tool, but... come on! How could you, or apparently lots of others think that a recording of a speaker playing in a room will give you any sort of useful info about it's actual audio performance? I don't care if the recording was made by a professional with studio mics and state of the art recording equipment and even if you have a class A playback system, none of which is typically the case.

If you think about it for two seconds, it is pretty obvious. That said, it seems that thousands of people somehow think YouTube recordings with unknown recording techniques will offer a useful glimpse into the sonic performance of all types of audio equipment. It is kind of like a beautiful photo of food with a scratch and sniff panel giving you an idea of how good a dish tastes.

Anyway, enough of that. I have never used a JBL LE-12C, but the two components are meant to be identical to the woofer and tweeter of the original Nova 88... which are the same in the original L100 minus the LE5 midrange. I would think if you added an LE5, duplicated the fairly simple network of the original L100 (http://www.jblproservice.com/pdf/Network%20Schematics/3112%20Network.pdf), and copied the cabinet and port you would likely have a satisfying result.

Widget
I know. It's a horrible tool. Even buying a DAC was done under duress since I'm not a streaming fan. Great advice though Widget. I've got a LE-5 in storage and can pick-up another one.

Rmac587
01-16-2017, 05:43 PM
OK, so it's been a couple of days dealing with the speakers. I picked up some new Jensen mid range on the cheap. The same model as the trashed ones that were in it before. I tried dropping in a LE5-2 into one but couldn't tweak it properly since I'm a novice. I tried an old Sansui woofer too. Not bad, but the JBL is better.


I removed the LE-12 woofers and cleaned them up. I also painted them, before you say a word, I know this is a big no-no, but for five bucks apiece for speakers that needed to be re-coned anyway I could care less. Besides, they had already been painted before.


I bought some 1/4 inch veneered board for about 20$ too and recovered the particle board boxes after I peeled off the old vinyl veneer. I have yet to stain the veneer.


The verdict is they aren't bad. They're a bit forward, but the muscularity of the JBL woofer definitely comes through. Whoever originally pieced it together knew what they were doing. The extra old radio shack tweeter seems to be crossed over as a "super-tweeter," so it combines well with the coaxial's tweet.


I'm going to use these as secondaries until I can score some 4410/12 or L112 or similar.

I appreciate all the helpful advice!
75468
75458
75459

hjames
01-16-2017, 07:15 PM
Performed well in a YouTube video? Were you listening through your laptop speakers? You do realize how meaningless that is, don't you? :D

Apparently a HUGE number of people are clueless that YouTube is a clueless method to audition any kind of speakers or gear -
Useless for anything other than to audition a song!

Rmac587
01-16-2017, 10:01 PM
Apparently a HUGE number of people are clueless thats its a clueless method to audition any kind of speakers or gear -
Useless for anything other than to audition a song!
You're late to the party. We already had that conversation.