Dating cts speakers
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.This is part of what made them so desirable in Fender amps, they stayed cleaner, and so drove the sound better into the higher volumes.The voice coil on the D series was 4" in diameter and composed of edge-wound aluminum; and the wattage was a solid 100 watts, based on enclosure loading, quality of signal, and other factors.In a Marshall or Hiwatt cabinet, the results were, well, devastating.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.In the first image, the D series speaker, you can clearly see the surround is actually a continuation of the cone paper itself, out to the mounting lip and under the cork at the edge.
Many D series JBLs are showing up with K paper on them, and then being passed off as "origianl cone" or "never reconed" to the unsuspecting public.This was a vast improvement and resulted in fewer blown speakers. This is probably due to the reality that the D series had been discontinued and the product code was convenient.And since the new cone design would retrofit the D series, there really was no reason to change the code.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.
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Mated with K-120s, this combination encourages the pursuit of tone.