The Vintage JBL West Coast Sound becomes the…

[Swerd]

… The Coast to Coast Sound Part 1

My first speakers were a pair JBL L-100As that I bought in 1973. I always enjoyed them and still use them today. Their easily identified sound, the so-called West Coast sound, was once a highly touted marketing feature. Ad copy claimed that musicians and recording engineers were buying or stealing the original model 4310 (a professional studio monitor that preceded the L-100s) for home use. JBL did succeed in installing these monitors in most large recording studios in the 1970s, including Angel, Capitol, Deutsche Grammophon, Elektra, EMI, London/Decca, MGM, RCA, Reprise, Vanguard, and Warner Bros. Although they may have been responsible for some bad studio mixes from the '70s and '80s, even by today’s standards, they do amazingly well for a 3-way speaker with only 2 crossover components. Their relatively high sensitivity generates an incredible attack giving music an energy and presence that few other speakers could reproduce then or today. Figure 1 JBL L-100.jpeg

When I got a home theater audio set up in 2000, I built it around the nearly 30-year old JBLs because they were still in great shape and I could find no full-range speakers for less than $2,000 a pair that satisfied me. Audiophiles have whined about the vintage JBL sound for as long as I can remember. Some of this may have been sour grapes due to their widespread sales success. And some of this was no doubt due to their obvious coloration. I soon learned to keep silent around the more outspoken audiophiles because I got tired of hearing those lectures about my misguided ways. Maybe part of my motivation here is to deliver, at long last, a rebuttal to those lectures.

A few years ago, I began playing with DIY speaker building. I was originally interested in learning what features are important in making a speaker sound good. To make a long story short, it’s all in the crossover, and to a lesser extent, cabinet design. A well designed crossover can make average or even poor drivers sound decent, and a well designed crossover combined with genuinely good drivers can make for a truly excellent speaker. Other exotic or expensive tweaks that we so often hear about all make much smaller differences – if they are audible at all – in comparison to the big improvements from a good crossover.

I eventually hit upon a DIY design that is my favorite, the CAOW1, a small 2-way speaker designed by Dennis Murphy (http://murphyblaster.com/) that combines a 5¼" midwoofer (SEAS CA15RLY) with a ¾" dome tweeter (Hiquphon OW1). Although I didn’t realize it at the time, I was carefully avoiding any DIY 3-way design that might compete with my JBLs. After I built the CAOW1s, I found that I preferred listening to music over them. Except for the obvious lack of deep bass below 50 Hz, they sound much more balanced and are more satisfying for listening. Not surprisingly, their frequency response curve is flat. The JBLs, my first love, sat in silence, except for movies. They just didn’t do it for me any more. I occasionally cranked them up to get a taste of their wonderful bass attack, but they now sound wrong in the critical midrange frequencies. But before completely giving up on them, I decided to test the idea that it’s all in the crossover.

Continued

 

[Swerd]

Coast to Coast Sound - Part 2

First of all, I rediscovered the remarkable build quality of those JBL drivers. The 12" woofer (JBL 123A) in particular is a gem. Black crackle finish covers a cast aluminum alloy frame. The motor contains a 6 lb. Alnico magnet of 10,000 gauss with a 3" edge-wound copper ribbon voice coil. Immersing the coil in such a strong magnetic field, results in a driver with outstanding sensitivity, range, and dynamic response. The cone, an early version of coated paper, with its characteristic white color, is unusually well-damped, as we shall see. All around close construction tolerances were common, as exemplified by the tiny gap between the voice coil and magnet. They are used in the L-100 with no low-pass filter at all in a vented 1.6 ft³ (45.3 L) cabinet. The JBL owner’s manual claims the vent tuning is at 27 Hz; however I am unsure about that.

The 5" midrange driver (LE5-2), with a potent 2¾ lb. Alnico magnet of 16,500 gauss, is even more sensitive. Used in the L-100A with a 1st order high pass filter at 1.5 kHz without any low pass filter, I could easily hear prominent upper midrange peaks, and feared that it may not be a very smooth driver.

The 1½" cone tweeter (LE25), although clearly not up to today’s dome tweeter standards, does OK below 10 kHz. It is used in the L-100A with a 1st order high pass filter at 6 kHz. Note that on my L-100As the polyurethane foam surrounding the tweeters has long since decayed.

The cabinet is heavy, solid and strong, with a beautiful walnut veneer that has stood up to time without showing its age. An obvious problem is the layout of the drivers.

Photos of these drivers can be see on a website (http://www.troelsgravesen.dk/vintage.htm) by Troels Gravesen, a DIY speaker builder in Denmark. He also shows frequency response curves of the woofer and tweeter from L-100As he intends to refurbish. Note that his woofer is smooth out to 6 kHz! Try and find a 12" hifi driver today that can do that! The tweeter looked OK, at least from about 3 to 10 kHz. That left the midrange driver’s performance an unknown. Gravesen’s information suggested that the L-100A drivers were good enough to deserve a better crossover, and inspired me to try.

In a similar effort, Troels Gravensen restored a pair of JBL L-26 Decade 2-way speakers of a similar age as the L-100s, http://www.troelsgravesen.dk/JBL-L26.htm. He designed a new crossover that seems to perform much better than the original design. If you are interested in restoring any of the older JBLs, his website is worth reading.

The original L-100A crossover is a good example that vintage is not always better. It contains only 1st order high-pass filters at 1.5 kHz for the midrange and 6 kHz for the tweeter. The woofer had no filter at all, and the midrange lacked any low-pass filter. It is certainly simple, but as we’ll see, it’s far too simple. Also note that old JBL drivers were made with the opposite absolute polarity compared to most other manufacturers of today. When a positive voltage is applied to the positive terminal of a JBL driver, the cone moves in-wards not outwards.

Figure 2 JBL L-100 Original Crossover.jpeg

At this point, I asked Dennis Murphy, if he was interested in this vintage make over project. His eager response generated the rest of the details below. I am most grateful for his expert help and enthusiastic guidance.

His first look at the speakers provided a frequency response curve that graphically shows just what “The West Coast Sound” means. Several features are prominent:

• A big ugly peak from 6 to 7 kHz. Perhaps caused by unfiltered breakup of the midrange driver, this peak certainly would have to be tamed.
• A general rising response as frequency increases, especially above 2 kHz. This probably can be easily corrected.
• Destructive cancellations were seen resulting in deep troughs at 3.3 kHz and above 9 kHz, producing a prominent comb filter effect. This is probably due to the unfortunate placement of the midrange driver relative to the tweeter and woofer on the front baffle.

The prominent rise and fall of frequency response below 200 Hz is the product of room reflections and their resulting standing waves and cancellations. It is not directly due to the speaker.

Fig 3 Old on-axis response.gif

 

[Swerd]

Coast to Coast Sound - part 3

Further testing revealed that none of the individual drivers seemed all that bad. In fact, Dennis commented, “Those paper drivers are much better behaved at higher frequencies than many modern drivers.” A decent solution might be found without swapping in a different driver as I had originally expected. The unfiltered frequency response of the woofer is shown below, followed by the midrange, and finally by the tweeter.

Figure 4 Woofer unfiltered.gif
Figure 5 Midrange unfiltered.gif
Figure 6 Tweeter unfiltered.gif

Dennis worked up a crossover design and while listening to it via his crossover emulation software, he sent me this rather provoking email:

“It sounds freaking great to me. The tweeter isn’t state of the art, but it gets the job done…”

For those who don’t know Dennis Murphy, he avoids colloquial exaggerations ands is usually rather understated. When he gets excited, I sit up and take notice.

Continued

 

[Swerd]

Coast to Coast sound - part 4

The predicted frequency response with the redesigned crossover is shown below, first with proper driver polarity and then below that with the midrange’s polarity reversed. The latter curve shows the new crossover points, and demonstrates that the drivers are in phase around the crossover frequencies when the polarities of the connections are correct.

Figure 7 New emulated response.gif
Figure 8 New emulated resp reversed.gif

The woofer-mid crossover, at ~950 Hz, involves Linkwitz-Riley 4th order crossover 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!

According to Dennis, “It took more than adding a low pass filter for the midrange driver above 5 kHz because the big peak was not caused by driver break-up. It’s actually an additive diffraction artifact caused by the wide baffle and the goofy layout of the drivers. Getting rid of it wasn’t easy, and certainly wouldn’t have been possible using the design technology of the '70s.” The profile from 10 to 20 kHz remains uneven, and is probably the best the tweeter can do – looking just like the unfiltered tweeter response curve.

Continued

 

[Swerd]

Coast to Coast Sound - part 5

Dennis built a test version of the new crossover which produced the following directly measured frequency response curve.

Figure 9 New on-axis response.gif

I listened to it and quickly knew that I would be building some crossovers soon. If the original sound of the JBL L-100A was the “West Coast Sound” (page 5), then I will call this the “Coast to Coast Sound”. It clearly shows that you haven't really heard one of these old book-shelf JBL speakers until you have heard it with a proper crossover.

Figure 10 New crossover.jpeg

 

[Tomorrow]

Swerd,

An excellent treatment and report. Many thanks for a walk down memory road with my long-gone L100's.

I haven't looked closely into the technology or topology of the newer JBL lines, but weren't the issues of the driver arrangement and crossover attenuation designs dealt with by JBL in the later series such as the J and S (which I now have)?

BTW, it's interesting that the "West Coast Sound" has a negative connotation with most people. Must be the politics, lol.

PS: I can't get the picture/thumbnail links. I hope others can.

 

[Swerd]

Yes, driver arrangement was a problem. I forgot to add part 6:

In this account I have repeatedly pointed out the problems caused by the driver layout of the L-100A. It has been a vivid lesson for me why almost all speakers today keep the drivers arranged in a vertical line. This photo (borrowed from a highly informative website on the history of James B. Lansing, his companies, and his speaker products: http://www.audioheritage.org/html/profiles/jbl/l100.htm) shows the four different layouts of the various JBL studio monitors made in the '70s.

The redesigned crossover I’ve described is designed specifically for the L-100A model (2nd from left). The L-100 model (3rd from the left) appears to have its drivers arranged in a vertical line. That might be a more desirable used model to buy if you can find one, but the redesigned L-100A crossover may not work as well for any of the other models.

 

[Swerd]

PS: I can't get the picture/thumbnail links. I hope others can.

You can't see any of the pictures? This whole tale is hard to tell without the pictures.

If anyone else has this problem, say so. I'll try and find another way to post the pictures.

 

[jaxvon]

Pictures work now!

BTW, if you want to post pics in the body of the post, you need to have the pictures on a hosting site like Photobucket, Flickr, etc and then paste the direct link to the picture between IMG tags.

This is a great project. I think there's one other modification I would make to the speakers: ensure that the cabinets are properly damped. A lot of older speakers have resonances in the cabinets that can be fixed with some damping material. WmAx can do a better job of explaining how to do this properly, so I'll PM him or something and ask him to post on the subject.

 

[Swerd]

I believe the old JBL cabinets are well made and there seems to be no noticable resonance problem. They are either ¾" plywood or particle board and are lined with 1" fiberglass. The bass response is very good and I was mainly concerned with correcting the glare and brightness in the mid and treble freqs.

By the way, last night I noticed an error in the schematic diagram of the new crossover that I posted yesterday. It is now corrected. If anyone is actually interested in reproducing this, be sure that the first shunt in the midrange circuit includes a 0.5 ohm resistor and a 0.68 mH inductor. My original diagram omitted the resistor.

 

[joetech]

What about L-88?

Very interesting. I've posted messages about a L-100/88 X/o rework before and didn't get too far. I was thinking of designing my own but why re-invent the wheel? I E-mailed the Vintage Audio guy in (Denmark?Gunerseon?) that was mentioned in this thread. He was planning to do something with his 123a and he has a new x/o for a L-26 which uses the LE-25 tweeter and a different woofer. I have some 35 year old L-88's that are like the L-100 but without the LE-5. You use to be able to buy a kit to add the Mid range but JBL doen't see it and don't often see them on E-bay but the drivers are abundant. I would have to loose my way cool grille to incorporate the Mid's. There were two different models of the L-88. On for ready upgrade and one that wasn't. I got the wrong one. L-88 still sounds better with classical which is what I listen to most.
It was suggested to me that replacing the 8uf cap would be a good idea. So I did. One of the speakers got some buzzing at about 80 to 100 Hz and that went way. I still like these speakers very much. I recently visited a boutique speaker Mfg in Phoenix Az and he demo'd some of his very nice tower speakers driven by some Cary tube amps and lots of other high end cables etc. I came home and listened to the same CD and I was not disipointed in my setup. Especially considering mine's pay for many years ago.http://forums.audioholics.com/forums/images/smilies/biggrin.gif

Only Question here is: Could I use this same x/o and leave out the mid? The old JBL x/o brought in the tweeter at 2000 Hz and just let the 123a roll off.
BTW I am just about finished with making Dennis Murphy's MB20's with a modification to the cabinet. Instead of the rear port I'm using a front slot. They sound good when I just layed them on the floor pointing up to hold in the drivers with the x/o external. I'm just about done with the finish on the cabinets and will mount them in the next day or two.

 

[zildjian]

Awesome thread. My first hifi setup was the L100's with a Marantz 2275 receiver & Dual turntable. Still got them, installed in my parents house.

 

[Tomorrow]

Awesome thread. My first hifi setup was the L100's with a Marantz 2275 receiver & Dual turntable. Still got them, installed in my parents house.

Aw, man. That was my DREAM setup. I was stuck with used/beat up 100s with Technics and Thorens....cheapo version of what you had/have.

 

[Swerd]

My first hifi setup was the L100's with a Marantz 2275 receiver & Dual turntable. Still got them, installed in my parents house.

Not unlike my first set up: L100s with Marantz 2230 receiver and an AR turntable. The L100s and one the various Marantz receivers (from 15 to 75 wpc) were very popular in the 70s. All of them drove the L100s nicely - they were that efficient.

If you are interested, for as little as $98 in parts, you can build two of those new crossovers and smooth out most of the glare and brightness of the L100s. I can email you a parts list that I used. I started building them over the long weekend.

 

[Bill Ding]

Swerd

Great project. It has been awhile since you posted. How is the building of the cross over coming? Got one up and running yet?

Bill

 

[Swerd]

It has been awhile since you posted. How is the building of the cross over coming? Got one up and running yet?

They've both been done for nearly a month now. Building the crossovers was straight forward. It was nice having an 11" diameter hole in the cabinet, it let me easily fit all the crossover parts on a 10×7 pegboard. For once no knuckles were scraped or wires broken while trying to cram the crossover board into a very small space.

How do they sound? In a word, excellent! My very first impression when I built the first one, was that the new crossover made the speakers a lot less sensitive. I had expected that, but it was still quite noticeable. But despite that, the new crossover did not suck the life out of those JBLs.

I spent about a week listening to one speaker with the new crossover, comparing it to the other speaker with the old crossover. After adjusting for the change in volume, the new crossover was a clear winner. Both me and my wife agree that the new crossover sounds much better. I tried a wide variety of music that I knew well, including some music where I actually liked the effect that the bright JBL upper-midrange had. The new crossovers eliminate the glare and brightness that I thought I had gotten used to. I remembered that years ago, I used to play with the bass and treble controls, and fiddle with the variable L-pads on the speakers to adjust midrange and tweeter levels, trying without success to control that ear-fatigue-inducing brightness. The new crossover does it much better. It really amazes me how much better speakers sound when the frequency response curve is flat.

 

[jaxvon]

It really amazes me how much better speakers sound when the frequency response curve is flat.

And yet again, Mr. Toole is proved correct.

Sounds like a cool project, btw. I bet it feels pretty cool to bring some speakers "back to life".

 

[zildjian]

Those speakers are classics. I'll make some new crossovers for mine someday. Hardly ever listen to them anymore though. They probably feel neglected since they were the kings for so many years.

 

[Swerd]

Those speakers are classics. I'll make some new crossovers for mine someday. Hardly ever listen to them anymore though. They probably feel neglected since they were the kings for so many years.

Yes, they not only are classics, those old paper drivers in general are probably better than any 3-way you could buy today for $2,000 a pair. I decided that $130 for crossover parts was a lot less than new speakers. I'll pm a parts list to you. When you hear them again, with a proper crossover, you will be glad you did it. They still have many of the qualities that made the JBLs from the 70s so good.

As far as power goes, anyone who had JBL L-100s knows how sensitive they were. I ran mine for years with a 30 watt Marantz receiver. A few years ago I replaced that with a Denon HT receiver that delivers 75 watts/channel. With the new crossovers, I do have to turn them up louder, but it is easily handled by that receiver. I have also listened to them powered by a separate amp, a B&K ST-140 that produces 105 watts/channel. That is somewhat better, but not by a big margin. I am looking for a good used B&K or Hafler 2-channel amp that I could power the new JBLs with. My goal is at least ~120 watts/channel at a tightwad price of $1/watt.

 

[Dryseals]

Fantastic write up and project. I'm kind of in the same boat with some of the vintage sound. Something about those older cabinets bring back some good memories. I always like the JBLs but was in love with the sound of ARs back then.
We had my wifes 50th birthday party the other night. I needed something to put out on the patio. So I took a set of Realistic speakers, top of the line for them back then, that had some beautiful cabinets and not to bad of sound for their age. Rather than reuse the old drivers, I took a couple of Vifa tweeters, some HiVi dome midranges and a couple of older Cerwin Vega 10" speakers and built a new baffle for them. I was in a big hurry, had one night to get them together. Tuned the ported box for 35HZ for outdoor use and arranged the speakers for best looks, 70s style. The cabinet had recessed the original baffle by 3/4" so a slab of 3/4" MDF slid right into place and mounted flush. Sprayed some flat black on the baffle mounted the drivers and tossed in an old three way crossover.
Blew the dust off an old Yamaha Integrated amp and connected it to the laptop with an assortment of music fitting to our age, bunch of old hippies with careers. Everyone enjoyed the music and many commented on the "vintage speakers".
We entertain a lot and have always gone to the shop for music (4 car garage and play area for olders guys).
Since I started back in the sound world, I alot of folks are bringing me their old worn out vintage speakers (the Realistics were one). Beautiful cabinets just worn down. Seems a lot of them would like to keep the cabinets but want better sound. I've got a few that might just be canidates for some crossover work, JBLs included.