JBL D-120. vs. D-120f

George Kimery · From: Limestone, TN, USA

What's the difference between these two speakers.

Mitchell Smithey · From: Dallas, USA

The F models have a slightly wider voice coil gap. There are some articles online by Harvey Gerst , who was at JBL at the time about this change to speaker to be used in Fender amps.

Bill A. Moore · From: Silver City, New Mexico, USA

Lemme 'splain it again.

The very original JBL D130's used in Fenders had an F stamped into the "foil
cal" (That's what the silver and orange label was called; it was made by Miller
Dial and Plate, which happened to be right next door to the JBL plant on
Fletcher Drive). Those JBL D130s were "identical" to the standard JBL D130 hi-fi
speaker (except for the addition of the stamped letter "F", they were from the
regular run of the hi-fi speakers, and they were just labeled as "F").

They were stock JBL's - they were not tested, manufactured or built any
differently - the foil cal was the only difference. Lemme put it another way -
they were the same fuckin speaker!! They were available in 8 ohm and 16 ohm
versions - always. Both models were the same, the standard JBL D130 or the
stamped D130"F". You could get them in 8 ohm or 16 ohm versions - always.

The only 130's that were differentiated by impedence were the 130A (8 ohms) and
the 130B (16 ohms) woofers. Notice these did not have a "D" in front of the
model ("D" stood for "Dome" or "Duraluminum", the metal the dome was made from).
The 130A & 130B had a paper dome and copper voice coils.

The imprinted D130F's (with the "F" printed in black) was a slightly different
speaker (using parts from the original D130"F") that I redesigned to be more
reliable and more durable without changing the tone (a major consideration since
I was a guitar player). That model, along with the D120F, and two new models;
the D110F and the D140F, became the basis for the JBL MI division.

We stamped the D130's we sold Fender with the letter "F" because of the repair
deal we had worked out with them. That way, we could see how many were being
blown or damaged, and they would show up on the repair list separate from the
hi-fi sold D130's. Fender was the biggest single customer for JBL D130 speakers
at the time.

Fender did not request the redesign of the JBL D130 - that was my idea to expand
the line and offer other models as well. I wrote up a two page proposal to Bill
Thomas, the President of JBL, and he liked the idea and put me in charge of it.

Leo Fender liked the new units and sales went up, the speakers were more
reliable, and everyone was happy. And Dick Dale had nothing to do with the
redesign (I keep hearing that from time to time). Hope this explains it.

Harvey Gerst
Indian Trail Recording Studio
http://www.ITRstudio.com/

George Kimery · From: Limestone, TN, USA

Thanks Bill and Michael, for the great and detailed information. My reason fomr asking is I am looking for a D-120 and found a couple D-120f's. I was concerned they would sound different and not be as appropriate for steel but if I un0derstand correctly, there is no difference in sound. Thanks for your enlightenment.

Steve Sycamore · From: Sweden

The reason for the slightly wider voice coil gap is that, especially in guitar amps, if the voice coil alignment was just slightly incorrect the parts would rub. Over time the rubbing led to failure. The staff who assembled guitar amps tended to ignore the designer's recommendation to tighten the bolts holding the speaker only hand tight. Over tightening the bolts tended to warp the speaker frame which forced the voice coil out of alignment.

George Kimery · From: Limestone, TN, USA

Mitchell, I did a search and found the Harvey Gerst articles. Very informative. I enjoyed reading all about that era as these speakers were evolving.

Thanks to everybody for your time and effort in more than answering my question

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