Dating cts speakers
Of course, beyond a certain point, the speaker is going to "break up", just like any other hard driven speaker.I run a Hiwatt DR-103 through JBL K-120s and it is stunning.The orange framed D series speakers were so coloured for Fender and the "F" designation after the D-120 (D-120F) was simply a reference that these specifically tagged speakers were slated for Fender amps.If you have heard anything about the orange framed speakers being somehow different than the grey framed speakers, you have been feed a load of hooey. Whether they actually got into the amps or not can be debated forever.The sad reality is that in excess of 90% of all D series speakers in circulation have been reconed with K paper.I have been using JBL speakers since 1970, well before the introduction of the K series speaker.While it is cleaner than most of its contemporary competitors, Jensen, Celestion, CTS, Emminence, et al, cone "break up" could still be achieved before ear splitting volumes were reached.
The cone joins to a cloth surround that has a "double bump" design, which is also doped for added strength, thereby overcoming the shortfall that was the flaw in the D series surround design.With the introduction of the K series, the wattage remained at 100W RMS, with the same 4" diameter edge wound aluminium coil.Because of improvements in the cone material and slightly increased thickness, distortion was "pushed back" making the speaker work cleaner at even higher volumes.For example, my D-120 (with original cones) equipped 1969 Fender Twin Reverb stays very clean up to around 6 and then begins to break up a little.
At full throttle, it breaks up very nice, with the compression of the 6L6 tubes helping keep that distortion nice and warm.I have owned D-120s, D-130s and at least 2 D-140s, all in original condition, some purchased brand new, if memory serves.