Posted on Feb 24 2009 08:06 AM
Ivan, here's Harvey Gerst's description. He was the speaker designer for JBL at the time. I'm not sure if this answers you exactly, pretty interesting though:
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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!
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 recomended 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 desinged 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.
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?
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).
For the original poster - 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--(at)--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
--(at)--11 pounds, 12,000 gaus flux density, and 275,000 maxwells total flux.
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.
We now return you to your regularly sheduled programing.
--
Harvey Gerst
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—
Danny Snyder
Latest project - Now That's What I Call SURF
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"With great reverb comes great responsibility" - Uncle Leo
I'm back playing keys and guitar with Combo Tezeta
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