Floor-standing loudspeaker system
The
P4 is the smallest speaker in the P Series, in order to achieve sufficient bass
extension the design engineers at
B&W came up with a unique
solution.
The
key difference, which is not visible from the outside, is the internal cabinet
construction. A folded tapered
duct has been used, which is selectively damped to give bass reinforcement similar to a reflex enclosure,
without the danger of pipe resonances that would otherwise arise in the tall narrow enclosure.
Technical highlights
Kevlar®: B&W developed and patented the method of
using Kevlar® for loudspeaker
cones to reduce unwanted standing waves. DuPont originally
created Kevlar® for use in bulletproof vests.
"The P4 is a two unit loudspeaker using a
Kevlar coned bass/midrange driver crossing over at around 3,5 kHz to a new variant of B&W's long
established light metal dome tweeter. This version, no wider than a matchbox,
clearly demonstrates the size reduction that is possible through the
incorporation of Neodymium in the magnet material without sacrificing the high
flux density around the voice-coil which is required to maintain sensitivity
and a fast response to transient sounds. In this application the only advantage
of the reduced diameter is to enable closer proximity to the main unit, which
can be an aid to cohesive integration. To this end the new unit is fitted with
a bevelled escutcheon recessed into the front panel.
The
168mm outside diameter bass/midrange unit is of familiar B&W construction
on a very open die-cast alloy chassis. This provides a very rigid mounting for
the large ceramic magnet assembly, together with a firm seating in the recess
provided in the baffle. The woven Kevlar cone is 120mm in diameter and is quite
mildly tapered; it is fitted with a 30mm diameter voice-coil of 3.8 ohms DC
resistance, centred in the magnet gap with the usual concentric bellows. The
outer suspension is a convex rubber moulding providing a reasonably long throw
and a sample unit showed a free-air resonance at 40Hz. ...
The crossover filter components are fixed to a printed circuit board
behind the input terminal panel which is recessed into the lower rear wall of
the cabinet. Outwardly this displays four large gold-plated terminals with 4mm
centres, each accessing one half of the filter for bi-wiring or
bi-amplification; these are normally paralleled with the links provided. The
bass/midrange section consists of only a single iron-dust cored inductor of I
.75mFl; the treble section is a capacitor/inductor 'T' with a 1.5 ohms resistor
to equalise the sensitivities of the two units."
Gramophone
Specifications
Systems: 2-way, 4 th order tapered-line
Drive
Units:
High
Frequency : 1 x 25 mm metal dome
Bass/Midrange
Frequency : 1 x 165 mm woven kevlar cone
Freqqueny
Response: 50 Hz - 20 kHz ±2 dB on
reference axis
Frequency
Range (-6 dB Frequencies): 37 Hz - 22
kHz
Dispersion
(20 Hz - 10 kHz):
Horizontal
: ±2 dB over 60° arc
Vertical
: ±2 dB 10° arc
Sensitivity: 88 dB spl (2,83 V at 1m)
Crossover
Frequency: 3,5 kHz
Nominal
Impedance: 8 Ω (minimum 3,7 Ω)
Power
Handling: 30 W - 100 W into 8 Ω
Dimensions
(H x W x D): 810 x 200 x 256 mm
Weight: 13,5 kg net
Finish: Black Ash, Rosenut, Cherrywood
Grille: Black Cloth
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