Pioneer CS-955

Big bass-reflex loudspeaker with Beryllium drivers - yes, not only Yamaha used that.

The CS-955 is the 1976 original ; the S-955 is the updated 1979 version.
The latter has only one difference with the original design : the 1978 PT-R7A ribbon tweeter instead of the PT-R7 (november 1974).
Also changed were the color of the front level pots and, of course, the name : CS was the usual Pioneer loudspeakers tag since Pioneer started making complete loudspeakers in the mid 1950s. The few made before were CT and, after the S-955, it was to be a simple S.


The tweeter of the S-955 is a PT-R7A beryllium ribbon, as described elsewhere on TVK : 9mg weight and 120Khz frequency response - twenty years older but already ready for SACD !
The original PT-R7 "only" went up to 100Khz, could handle a bit less power and was a tiny dot less sensitive. It seems however it was better at horizontal dispersion - there's always a give and take somewhere.

The bass is a 36cm cone held by a diecast aluminium frame which probably had some design equivalences in the TAD lineup, even if distantly.

The mid driver is the most... original :
it is a Beryllium dome where the diaphragm is suspended by five wires which allow for an even more linear piston motion and avoid having too much sound radiate from the edges of the diaphragm, where dispersion isn't linear and distortion higher.

The wires are made of an elastomer and allow the driver to rotate around when sound is to be produced : the diaphragm's movement is therefore something like a (very slightly) circular piston.

The inside of the mid driver is damped with felt pieces and its dedicated enclosure is further damped with glass wool. The front center cap is copper-plated and topped by a 5-arm phase plug ; resonance frequency lies at 300Hz - 650Hz lower than the crossover frequency used.

The 47kg enclosure is a thick and heavily braced box made of plywood - the best wood for audio uses.
The filter allows tri-amping or normal all-together-now powering.


The later S-955III mainly saw only non-visible changes : filter wiring, input power handling, componentry and filter structure, and the PT-R7III instead of the PT-R7A.
Quite visible, however, was the front bass-reflex port which was reduced to a quarter of the one carved in the S-955 !

The chronolgy of the Pioneer loudspeakers using the suspended trick is as follows :
CS-3000 (december '72)
CS-3000A (september '73)
CS-955 (october '76)
S-955 ('79)
S-933 ('79)
S-955III ('82)
S-9500 & 9500DV ('85)


Whatever the name, CS-955, S-955 or S-955III (btw, what happened to the S-955II ?) I really wish I could import one from Japan - I have a hunch I'd really love music from this biggie.