The power handling of early JBL drivers was determined as scientifically as one might think. Harvey Gerst, the man who developed most of the early drivers we know and love, has some interesting things to say about their development:
Harvey Gerst on early JBLs
…let me take you back to the late 50s, early 60s. JBL was a small company with their main offices above a candy store, and the manufacturing scattered in a number of buildings up and down the street, near Glendale, on Fletcher Drive.
They made the following speakers;
the D130 a full range 15",
the D131 a full range 12",
the 130A a 15" woofer,
the 130B (same as the 130A, but 16 ohms),
and the 150 - a 15" woofer with a heavier cone.
The D stood for a metal dome and the A and B were for woofers of different impedances. I don't remember if we made a 131A. We also made a D123 (full range pancake 12" speaker) and the D208 and D216 (both 8" speakers but with 8 and 16 ohm voice coils).
Fender was buying D130s for use in their Dual Showman systems, but they were experiencing problems in surrounds drying out from outdoor use, and burnouts from improper mounting techniques. I wrote a memo to the president of JBL, outlining a plan to let me design a series of speakers made specifically for musical use and he agreed. My plan called for modifications to the D130 and D131, plus an all new bass 15" speaker, and a new 10" speaker.
Since Fender was our largest purchaser, I did not want the headache of trying to re-introduce a whole new series so I kept the D130 name for the 15" and simply added an F (yes, the "F" is for Fender - don't know why to this day I did that, but I did). Since I was making up new model numbers, I decided where possible to keep it simple, so the 12" (originally the D131) became the D120F, and the new 10" became the D110F.
That left the new bass speaker. I didn't want to leave it in the 13x range because it was different and the 150 was already being used by our theater woofer. The 140 was not being used, so I named the new bass speaker the D140F.
After I left JBL, I understand they came out with the black crinkle finish and renamed them E series. The first major modifications were made in the K series, as I understand it.”
Harvey Gerst
9/19/97 alt.guitar.amps
the F is more rugged for portable use as a musical instrument speaker as compared to home use only on a fixed environment.
The "F" originally stood for Fender, since they were the largest purchasers, and at one time, the distributor for all the JBL guitar speakers. But the D130F speaker was not designed specifically by, or for them and the F eventually came to be just an indicator for all of the JBL musical instrument series speakers. The D130F did not have any significant frequency range differences, compared to the home version - the D130.
I feel I must tell you there is slightly more relief on the D130F top plate to accomodate a wider variety of mounting techniques (i.e., idiots who use torque wrenches to flatten these frames onto a warped baffle board).
Harvey Gerst
9/7/96 alt.guitar.amps
I saw a lot of D130's come through with fried voice coils that were running off a 12 Watt Williamson amp during the 50's and 60's. Integrated music from HiFi systems caused one kind of problem - using the D130 as a musical instrument speaker created other problems.
That's why I suggested the D130F (which was a redesigned D130), made expressly for musical instrument amps, as were the D110F (a totally new design), the D120F (a redesign of the D131), and the D140F (a new design using existing parts).
Power specifications for the F series were nominally 35 to about 60 Watts. How did I arrive at these figures? Pretty simple, I played guitar and bass through them and kept increasing the power till they blew. Then I downrated them from the power that fried them. Pretty hi-tech, huh? It seemed to work pretty well (of course we didn't have synth players back then).
The major amp manufacturers back then were Fender, Sunn, Kustom, and Ampeg. Rickenbacher and Mosrite also bought some, but nowhere near the volume of the other amp makers. All had JBL speaker options.
And yes, the "F" stood for Fender, since they were the largest single buyer, and also distributed the F series to music stores. They had no part in the design or the idea for the new series, I am solely to blame
for that.
Harvey Gerst
9/11/96 alt.guitar.amps
Q. Dick Dale seems to be the one claiming Fender went to JBL on behalf of him. In "Fender Sound Heard Around the World" he's quoted as saying the "F was invented as a result of melting voice coils & destroying surrounds". It's also stated that "the aluminum dust cover was Leo's idea". In his 9/96 GP interview he talks of the 'Dick Dale' kit available from JBL which includes a larger magnet, larger voice coil, thicker wires, aluminum dust cover, & rubberized front rim which brings the speaker (presumably a D130) up to Dick Dale & Fender specs! I'll be 'kind' and say that he comes off as 'a bit arrogant' in the interview!
A. I never had the honor of meeting or talking to Dick Dale, so I'd have to say that perhaps his memory has been clouded by the passing years. It's true that the JBL F series was partly about improving the current 2 models being used by Fender and others, namely the D130 and D131. It was my proposal to expand the line of speakers and at the same time, make some refinements to those speakers to make them more suitable to the guitar market. Here's what I did and why:
Opened the voice coil gap slightly on the D130F to allow more tolerance in mounting. Most people didn't realize that even though 8 mounting holes were available, only using four is the recommended mounting. And you don't screw them down tight to the board - that warps the frame. You use two fingers to do the final tightening - the casket will them complete the seal. When you warp the frame by overtightening, the voice coil can go out of round and eventually drag and short out. I opened the gap slightly to allow for this problem with just a very slight loss in efficiency - less than 1 dB.
Did the same thing on the D131 (and renamed as the D120F).
Using parts from the D130A and D150 woofers, I created a new woofer designed for bass guitar applications called the D140F. This had a copper voice coil and an aluminum dome.
Using the magnet assembly from the D123 and the basket from an LE-10, I added the D110F to complete the line of musical instrument speakers.
The surrounds were NOT "rubberized". JBL had developed a high viscosity coating to add to the existing hifi line of speakers that reduced ringing. I used it for a different reason. The hifi speaker surrounds dried out when exposed to excessive sunlight and heat, and I reasoned the viscose coating (we called it "goop" back then) would help prevent that.
Q. The other reference to Fender going to JBL was in conjunction with the development of the 1959 Vibrasonic. In Morrish's Fender amp book - Bill Carson recalls testing a protype JBL with a copper instead of aluminum voice coil & a thin paper cone? Can you shed some light on this obscure piece of JBL history?
A. Bill's probably refering to the D130A which was simply a standard JBL woofer at the time - all the woofers had copper voice coils. The 130A was basically a D130 with a copper voice coil and a paper dome and was used in the 001 system primarily (D130A, N1200 xover, and 175DLH driver/horm assembly). I felt the cone was too light for bass guitar and we wound up using the cone from the 150 woofer, a heavier unit. The duraluminum dome was added to the D140F, instead of the paper dome for cosmetic reasons at first, but later proved useful in adding a little more top end to the bass (not much though).
Q. regarding power ratings, I checked my official(3/70) JBL spec sheet for the F models and the 110F, 120F, & 130F are all rated at 100W continuous, the 140F @ 150W continuous. JBL defines 'continuous power' in my 4311B spec sheet as 3dB greater than RMS which would put the RMS rating of a D130F at 50W. On the other hand, D120Fs & D130Fs ran reliably in Showman 12s, Showman 15s, and early Boogies at considerably more power, so Mr. Gerst's & JBL's ratings are not marketing hype! It also appears that the 120F & 130F use identical magnet structures @ 11 pounds, 12,000 gauss flux density, and 275,000 maxwells total flux.
A. The D120F and the D130F, like their close cousins, the D130 and D131, all shared the same voice coil, dome, spider, and magnet assembies, except for the slightly wider gap on the top plate. I think the flux density was really around 11,700 gauss or so on the 120F & 130F because of the slightly enlarged gap, mentioned earlier.
Power handling was always a touchy subject and I just basically guessed at what I thought it could handle, based on normal playing. It was a little tricky since we were dealing with rock, country, jazz, and blues players and the power handling figures were just suggestions, regardless of how official the spec sheet looked.
The D130 and the D130F were essentially the SAME speaker. Exactly the same voice coil, cone, spider assembly, magnet, basket. The only things I did to the F are listed in a previous post, along with my reasons for doing them.
I revised the guitar ratings since those D130 ratings were for INTEGRATED music, like a symphony or a full band playing from the radio, tape or a record. The rating for a single live instrument like a guitar is much different, since there is nothing below 80 Hz or above 5 or 6 KHz coming out of a guitar (at least back then). A D130F (or a D130) could easily live with a higher power rating and we/JBL/I adjusted the rating accordingly. The new rating would also apply to a JBL D130 if used for that purpose.
If you had called JBL back then, you would have been transferred to me and that is what I would have told you. Since I was in charge of that division, I was responsible for creating those ratings and that was
our/my official position on the subject. As far as power handling, there was no difference - the rating was changed to more accurately reflect what the D130 or D130F could handle if used with a guitar as the source.
The lower rating also still applied if either speaker was used for full range music reproduction. These were my "babies" and if you want to disagree with me, that's fine. If you were at JBL at the time I was designing these, we could have had some rousing discussions about it. And besides, I think I also wrote those spec sheets for the D130 as well.
Q. A couple more Q's & I'll leave you alone - Didn't know the D140F has a copper voice coil - is it an edgewound ribbon like the aluminum coils? What were the reason(s) for using copper (vs. aluminum) in the D140F?
A. Yes, the D140F had an edgewound copper ribbon voice coil. Copper has better heat conductivity than aluminum (think pots and pans) but it's heavier and not as responsive to high frequencies, due to it's weight. For use in woofers, copper is the wire of choice.
Actually, had I thought about it some more, I should have probably made the D140F more of a full range speaker, but it was basically designed as a replacement for people using D130A woofers for live music.
Harvey Gerst
