JBL L100's: Now I get it.

[SaturationPt]

I agree on the lack of bass, which includes all of that series/era of JBL and also the Yamaha NS1000Ms. However, the Engineers mixed the music so that it sounded as close to the same on those speakers as it did live in-studio, so the deficiencies of that era speaker was compensated for in the mix. Therefore, it is my opinion that listening to that era of music on that era of speaker (especially monitors) should give you music very close to studio recordings of the same era and modern speakers will reveal the boosted bass that was mixed to compensate.

However, I use a (JBL LSR6312SP Studio) sub with my 4312As, high-passing the 4312As when I want to listen to more modern music on the vintage system, and according to my mic and after calibrating the sub's RMC I get a very flat low-end. If you love everything else about your early speakers (including Klipshhorns etc.) but they don't go low enough, ... just add a sub and crossover.

 

[RobRoy]

I agree on the lack of bass, which includes all of that series/era of JBL and also the Yamaha NS1000Ms. However, the Engineers mixed the music so that it sounded as close to the same on those speakers as it did live in-studio, so the deficiencies of that era speaker was compensated for in the mix. Therefore, it is my opinion that listening to that era of music on that era of speaker (especially monitors) should give you music very close to studio recordings of the same era and modern speakers will reveal the boosted bass that was mixed to compensate.

However, I use a (JBL LSR6312SP Studio) sub with my 4312As, high-passing the 4312As when I want to listen to more modern music on the vintage system, and according to my mic and after calibrating the sub's RMC I get a very flat low-end. If you love everything else about your early speakers (including Klipshhorns etc.) but they don't go low enough, ... just add a sub and crossover.

Nailed it. Nicely done.

 

[WaynerN]

I agree on the lack of bass, which includes all of that series/era of JBL and also the Yamaha NS1000Ms. However, the Engineers mixed the music so that it sounded as close to the same on those speakers as it did live in-studio, so the deficiencies of that era speaker was compensated for in the mix. Therefore, it is my opinion that listening to that era of music on that era of speaker (especially monitors) should give you music very close to studio recordings of the same era and modern speakers will reveal the boosted bass that was mixed to compensate.

However, I use a (JBL LSR6312SP Studio) sub with my 4312As, high-passing the 4312As when I want to listen to more modern music on the vintage system, and according to my mic and after calibrating the sub's RMC I get a very flat low-end. If you love everything else about your early speakers (including Klipshhorns etc.) but they don't go low enough, ... just add a sub and crossover.

I'd just add that microphone technology wasn't like it is now either.....so the mics of that era matched the speakers of that era, if that makes any sense....

 

[sanford12]

At low listening levels I've heard them sound wonderful but their not for me when the volume goes up. Try them with a Kenwood KA-8006. They were literally made for each other.

 

[hjames]

I almost forgot. I have several copies of a double album produced by JBL that was used specifically to sell those speakers. It's called Sessions. I opened one and kept the others sealed. Because I have limited space in my place, I rotate groups of records in and out of storage. Those just stay in storage.

Its a goodie to have ...

 

[lokerola]

I popped over to fleabay to price some L100's. Good Lord. I think I'd rather spend 1/4 less and try some new JBL Studio 230's. I know, I know, totally different speakers, but those L100's are outrageous.

 

[RobRoy]

I popped over to fleabay to price some L100's. Good Lord. I think I'd rather spend 1/4 less and try some new JBL Studio 230's. I know, I know, totally different speakers, but those L100's are outrageous.

They are kinda like '65 mustangs. Just a glorified Falcon, but there is a strong following.

 

[R Swerdlow]

The L100's midrange did not have a coil in it to remove it from the tweeter's duties. JBL designers just let it roll off naturally using only a single cap (I think it was a 6mfd) to separate it from woofer duties ( I think the tweeter had a 3mfd cap). While this kept the cross-over as a simple 6 db per octave verity, I think the tweeter and the midrange were both producing some of the same information, but I have no idea when the mid rolled out of the picture. This "error" may be one of the reasons for the hot mid/hi end. I used a pair for about 2 decades, eventually bi-amping them when I took the woofer and put it on its own inputs. I sold them to a friend at work in the late 80s. I wish I still had them just to work on the X-Over.

In the L100A version, the two high pass filters consisted of an 8 µF cap rolling off below 1.5 kHz for the mid range, and a 3 µF cap rolling off below 6 kHz for the tweeter. The schematic looked like this. (Note, there is a mistake in this diagram. The polarity of the LE5-2 mid range driver should be the reverse of what is shown below.)

And it measured like this

There is a general rising response as frequency increases, especially above 2 kHz, which contributes to the L-100’s forward sound.

There is a big ugly looking peak from 6 to 7 kHz. It sounded ugly too, but only if the music had overtones in that range.

Destructive cancellations in the sound are seen resulting in deep troughs at 3.3 kHz and above 9 kHz, producing a prominent comb filter effect.

Dennis Murphy, who did the all these measurements, designed a new crossover to fix these problems. I built it and wrote it all up http://forums.audioholics.com/forums/threads/the-vintage-jbl-west-coast-sound-becomes-the….25014/. Here is the schematic.

The woofer-mid crossover, at ~950 Hz, has Linkwitz-Riley 4th order acoustic slopes. The mid-tweeter crossover, at 5 kHz is also LR 4th order. The glaring 6-7 kHz peak is essentially eliminated, and the high frequency comb filter cancellations are also gone. When built, it measured like this.

The exaggerated bass below 100 Hz is the result of mounting the 123A woofer in a small (roughly 1.8 ft² if I remember correctly) ported cabinet. That woofer can produce a much flatter response in a larger sealed cabinet, 3.9 to 5.9 ft². No crossover can fix that.

 

[WaynerN]

Yeah, I can't remember a cap value 30 years ago, but I believe the 8mfd, that makes sense. I know Denis from RMAF as Salk Sound shared a room with Frank.....

 

[R Swerdlow]

Yeah, I can't remember a cap value 30 years ago, but I believe the 8mfd, that makes sense. I know Denis from RMAF as Salk Sound shared a room with Frank.....

Then you know Dennis's remarkable ability to design speakers so they have a flat frequency response and sound wonderful. I've known him for more than 10 years and I never stop being amazed at his ability to quickly hear what a speaker does, right and wrong. I have built several of his DIY designs, and own Salk speakers. The new crossover for the JBL L100 was my first experience with Dennis's ability.

I once met Frank when he came to an audio show in the Washington area. He is smart, opinionated, and very interesting to talk to. I liked him.

Dennis thinks Frank has a well developed sense of what a good sounding speaker sounds like. When he first designed the SongTower, Dennis nervously waited for Frank's opinion of it. After Frank said he liked it within 10 seconds after first hearing it, Dennis smiled.

 

[superdog]

A tube preamp showed me a different side of the L100.I know these can be a bit harsh with certain amplification.

 

[hjames]

Zilch used to say they were fake, but fun!
(My college budget meant I had L36s when the L100s were new)
I found a pair locally a few years back, tried to figure what the appeal was,
but they weren't for me.
But if they are in great shape, they can sell for good money,
and their resale can fund something more to your liking!

 

[WaynerN]

I have the Studio 230 (and 580) speakers. They are both wonderful.

 

[GordonW]

More than 2 configurations!!

http://www.audioheritage.org/html/profiles/jbl/l100.htm

Don't forget the L88 Plus 12 a.k.a. the L88P/M12!

Regards,
Gordon.

 

[savatage1973]

Zilch used to say they were fake, but fun!

YUP!!! I have a pair of original L100's (with the original sales receipt from Dec. 1977) as well as two pair of 4312C Control Monitors--one pair early with the Alnico woofers, and one later pair with the ferrite woofers. None of them "dig" as deep as you would expect from a 12" woofer in a ported cabinet, but they rock. For 70's and 80's rock/punk/alt, they are truly "fun", and their weaknesses compensate for the weaknesses of the recordings from that era.

 

[toxcrusadr]

I would just like to say how freaking amazing that crossover rebuild looks. Daaang! Thanks for posting R.Swerdlow.

 

[E-Stat]

However, the Engineers mixed the music so that it sounded as close to the same on those speakers as it did live in-studio, so the deficiencies of that era speaker was compensated for in the mix. Therefore, it is my opinion that listening to that era of music on that era of speaker (especially monitors) should give you music very close to studio recordings of the same era and modern speakers will reveal the boosted bass that was mixed to compensate.

It's certainly true they were weak with first octave content, but I find the result of their bloated midbass was predominately bass thin sounding recordings of the 70s.

 

[WaynerN]

It's certainly true they were weak with first octave content, but I find the result of their bloated midbass was predominately bass thin sounding recordings of the 70s.

Too bad I don't have mine anymore to compare......oh well. I could start a thread on stuff that I got rid of that I should have kept......can you say hoarder?

 

[freQ(*)Oddio]

i am related to the biggest l100 fan , he is probably 60 yrs old now and will not listened to anything else since he bought them in 1978, he doesnt talk about it or push the L100 subject, but if you start it, ohhh boy. of course my kefs and epi towers are no good lol. i get it but i like them after settling in for a while, but at first listen they are def there to make music no doubt. they are in the room and will be known they are the boss.

 

[WaynerN]

Part of the problem is that there should be 3 octaves between the woofer and tweeter cross-over points for the midrange driver. So if one wanted to keep the cross-over at a simple 6db per octave thing, the X/O frequencies would have to change. If we kept the woofer at 1500, then the tweeter would have to be at 12K. That would probably sound horrible with gaping holes between the mid and HF driver.

That more then likely explains why the cross-over for the L100/L100A are the way they are. Perhaps if one didn't want to go the Dennis Murphy route, a 1/3 octave graphic EQ would help smooth out some ills (but not all).