JBL L Series (1990s)

[clmrt]

LOL

Thanks RC.

[CHagen7]

Hi, yall, I'm back! Been dealing with the M&K auction....
In answer:
1) The "uphill climb" in an L-5 is about +2dB from 200 Hz to 10kHz. Fortunately, ALL of the frequency sections climb and at the same rate, so I made it smooth. It doesn't sound as bright that way.
2) The jumper is a wire with it's tail connected to a point between the woofer inductor and the woofer hot lead. In normal mode (or whatever I/we called it), it connects to the non-grounded end of the orange capacitors, making a second order woofer section. The other fast-on tab is electrically in front of the woofer inductor. So when you move the small-tabbed end to that tab for bi-amp/external crossover use, not only do you disconnect the capacitor, but you short the inductor thus eliminating the passive crossover. (That one took a few days - it's been 15 years!!!!.....and if I'm wrong, let me know and I'll take one of my spares apart, but that's what I recall).
3) No, not much of a clothes horse.....that was my brother. I figure if it's not too ugly and hides the body, that's all ya need. For a more recent shot, go to the M&K website, pull down "what's new", click on the message from Ken, then at the bottom of the page click on "what makes an m&k an m&k". Both shots taken on the same day - I didn't wear the same shirt all the time....
Chris

[rww1951]

Chris, finally decided to try bi-wiring my L7s. I noticed a definite improvement but ended up with one change I do not like. The bass response is over powering and the bass control on my preamp doesn’t change it. I guess I could have a problem in the preamp but it’s funny it occurred at the same time I made the wiring change. Any ideas?

[CHagen7]

RWW - so you took the straps off, and you ran two wire sets, one for the high frequency input and one for the low frequency input? You didn't change the internal jumper, did you? That's only for bi-amping with an external crossover to roll off the 12" woofer and readjust level again. Let me know. It should be a more subtle change.

[rww1951]

Yes, straps off, seprate wires from the amp. Did not change the internal jumper. The LOUDNESS button does work and like I said the bass control has little or no effect. When I get time I will change everything back to the way it was and see if the problem goes away. I did such a nice job I hate to tear it all apart! One other thing, I am driving them with a 250W Carver TFM amp with only 10 feet of 12 gauge wire so the L7 LF drivers are seeing lots of power!

[rww1951]

Well I removed the bi-wiring and it appears the problem is in the preamp, the bass is running wide open with no adjustment. The wide open bass is causing the LE120H-1 woofer in the left L7 to vibrate into a rattle at medium to high volume. What failure in the driver causes the rattle?

[Titanium Dome]

I'd say it's trying to notify you of its impending destruction if you keep driving it like that. If it were me I wouldn't play it at all until the underlying problem with the signal is corrected.

It's hard to say at this point if it bottomed out, overheated the voice coil, excursioned too far forward, split the surround, or if it's not able to reproduce a defective signal that's being sent to it.

Hopefully, Chris has an intimte working knowledge of that woofer and can shed some light.

[Titanium Dome]

The baffle on the L7 and other L Series cabinets appears to be some kind of plastic laminate. This seems to be a unique feature, at least in the way it's implemented. Since this appears to be a deliberate choice, I'm curious as to the reason(s).

Was this an engineering choice, an accounting choice, a marketing choice, or what?

[CHagen7]

Sorry about the response delay - I'm still settling stuff from M&K...

RWW - that doesn't sound good. It sounds like you now have a rubbing voice coil. It MIGHT be a loose wire from overheating, but then you'd hear a scratching all the time. That woofer should be reconed. And I wouldn't play with your preamp until it's repaired. Oooorrr - it could be that your preamp just sends those outputs wide open with no level control. What's your preamp? And thoroughly red your manual about the outputs you used before deciding it needs work.

It could be your screws are loose! Haha, just wanted to say that. Seriously, though, it could be something silly like that. You'd be surprised how some speakers ship, from ALL manufacturers...

It could be you're tapping the voice-coil/cone joint on the motor top plate, but the level sounds way too low for that. The LE120H-1 is a good traditional heroic JBL 12" woofer with 3" motor. So it plays LOUD.

You can check for a rubbing voice coil by disconnecting the speaker from the amplifier, and with grille off, pushing gently at different points around the voice coil inward about 1/8 - 1/4". If you have a rub, you will hear a scrape at one point only. If you don't hear anything, you probably don't have a rub.

Everybody should remember the Speakerlab Number One Rule (from the '70's, Bones!): IF IT SOUNDS BAD, TURN IT DOWN!!!! You'll avoid a LOT of misfortune this way. Many times a quick fix saves a lot of time waiting for repair...

I agree with Titanium Dome, though. I'd worry about getting the preamp correct first. Use another if you have to, but make sure the preamp is good. You can't go back to the original wiring with this preamp, because it has shown that it may have a defect. Then, once you have a known good preamp, I'd go again on the system, leaning carefully (volume-wise) on the speakers and see if the left one still has the issue. Then check for the above problems.

If you have to, then find a good recone company that will support your speaker.


Actually, the L-series baffle is shaped MDF, and then black high-gloss lacquered. What you are seeing is the laminate layers that form in the MDF during its manufacture. The only times that they did something special for the baffle when I was there was XPL, with the shaped MDF, encased in the expanding foam, with the neoprene cover - and when Pro laminated carbon fiber to the MDF for the new 4300's. Although, I may be forgetting a few. But definitely the L-series baffles were MDF. I don't recall thickness, but in general, L-series had 3/4" baffles.

I wanted to put more bracing in the woofer area on the L-7 due to the wide baffle/side panel, but the 1" sub-baffle seemed to work pretty well, and JBL Consumer wanted it yesterday, so I had to let it go as it was. We didn't have a good panel vibration measurement set up at the time anyway, so it probably would have added quite a bit of time to the project.


Chris

[rww1951]

Thanks for the response Chris. Problem solved! Setup a different preamp and noticed the same rattle on the other L7. At that point I started looking for other causes, I knew it most likely couldn’t be both LH drivers. I don’t know the technical term for it, but the air from the woofers was bouncing off the equipment cabinet (2 feet away) and bucking against the LE120Hs making them rattle. Reversed the speakers, firing the woofers outward and no more rattling. As I stated in a previous post I am very limited with the placement of my system. Moral of the story is always look for the simple things when trouble shooting a problem. To answer your question about the preamp, most all my equipment is vintage CARVER. Last night an Audiophile I know stopped by with a SACD player and some SACDs and I auditioned the L7s for him and he was amazed with them. Soundstage, low, mid, and high range and fullness. Coming from someone with really high dollar equipment and a lot of experience I felt really good. Thanks for the great design!

[100r1]

Wow, Finally get to know who designed my L7's. Thank you Chris for your work.

I have a pair purchased new October '92 paid $ 1,099.00 delivered to my home. They are still the main speakers I use in my HT.

I fell in love with the JBL sound back in the early 70's while in school and doing some recording at Criteria Studios in North Miami, Fla. They were using 4310's as monitors. I was blown away by the sound. The Lust for musical reproduction was born. Well a young kid in school could not afford such sound.

In the 80's I purchased a retired set of 4311's and they served me well. Looking to change the look and feel of my system (and make the wife happy in the looks department), in the 90's I went looking for a something different. No matter where I went or what I listened to I always ended back in the JBL sound rooms. The L7's were just out and the store that had them set up did it right with placement and power. Again they Blew me away.

I have always been dismayed at the negative comments people have posted on the L7's, but after many years of owning them I have concluded that others that have owned them or auditioned them never had them set up proper. I also found that 35 watts minimum power recomendation was way to low for the proper head room these speakers require.

The L series from the 90's were JBL quality in the Drivers, Crossovers and cabinets. It a shame that the average person never realizes what it takes to build a quality musical instrument.

[Titanium Dome]

Glad to see you on the forums, and an L7 lover, too!

It is a great treat to have Chris come here and share some insider info with us.

[neilsworld]

L series was always a no-compromise line from the performance side. But to keep the price down, L series did use less expensive fittings, cabinetry, and finishes.

Thank you for all of your excellent work and, more recently, the comments and information you have contributed here.

Based on your comment, would there be any advantage, improvement, or merit in constructing new cabinets identical in size and design out of more exotic timber, materials, fittings, and finishes?
My black ash veneer has suffered some sun damage over the years....

Regards,
Neil

[JBL 4645]

Whoa! Slow down that volume control. You may be clipping your amp and running a lot of high frequency grung into you tweeters (especially with that 50-watter).

David

Yeah passive crossovers suck, no insult intended I’ve kinder lost faith with passive, active crossovers rule. Passive generates too much distortion.

[BMWCCA]

L series was always a no-compromise line from the performance side. But to keep the price down, L series did use less expensive fittings, cabinetry, and finishes. I always felt the L-5 should have had a bigger woofer. I liked the prototype sidefire 10" 3-way the best. But it was designed as a dual 6" by the industrial designer and initial pictures taken (these show in the earlier ads/lit sheets). Then we played with dual 8" woofers, but the president of JBL Consumer decided to tie it in to the 4-way L-7 by making it an 8" 4-way. When said and done though, it works, the drivers blended nicely (even with the uphill climb), and it certainly made a place for itself.

I've been casually looking for a pair of L-5s ever since reading about them on this site. I don't remember them at all from when they were new. I started out looking for L-7s but in reading here I figured the placement issues would kill them in my small house. Maybe some day. Anyhow, I'm a two-day L-5 owner now, thanks to Brutal's tip and Spwal's intercession on my behalf. I've placed them next to my 4412As and listened to the monitors first them swapped speaker leads to the L-5s using the same Soundcraftsmen DX4200 and Crown PS-400. Wow! I'm probably even more impressed with them than I thought I'd be. I'm going to bring in another PS-400 so I can power both pairs identically for a true A-B comparison. Initially, I don't think the L-5s give anything away on the bottom at normal listening levels to the 128H-1 12" in the 4412As. It's still a small room and I don't have them the desired 3-feet off the rear wall so they get a bit muddy at extremely high volume (and I mean extreme) but the imaging in the room with the L-5s six-feet apart listening six-feet away is really remarkable. A very impressive small package. I can't wait to compare them to the L112s, L150As, and 030s in the larger room. I really can't believe the sound that comes out of those tiny components. And I'm happy to be able to say I know who designed them! Thanks Chris. Great job! I promise never to give them too little power.