Definitive Technology BP10B Review Manual

Stereo Review
D T
EFINITIVE
"...a truly outstanding speaker system."
Julian Hirsch, Hirsch-Houck Laboratories
D T
EFINITIVE ECHNOLOGY
first product is an unusual loud-
speaker that offers exceptional
performance for its size and
price. The BP10 is a slender columnar speaker
measuring 42 inches high, 9 inch-
es wide, and 11 1/2 inches deep and
weighing about 60 pounds. Its exterior is
completely black, and the four sides are
covered by a fabric sleeve that fits snugly
around the enclosure. The wood base and
top plate have a glossy lacquer finish. The
top cap is also available in solid oak. The
gold-plated, multiway terminals, which
accept dual banana plugs, are under the
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EST
BP10 B
ECHNOLOGY
' base, with a slot for the connecting cable.
S
There is no visible indication of the
number, size, or configuration of the driv-
ers. Actually, the BP10 is a bipolar system
(hence the "BP" designation) containing a
pair of identical two-way speakers. One
faces forward conventionally, and the oth-
er is on the rear panel, facing backward.
Each consists of a 6 1/2-inch woofer and a
1-inch dome tweeter, with the woofer lo-
cated at the top of the cabinet and the
tweeter just below it.
Since the front and rear halves of the
system radiate in phase over their full fre-
quency range, their bass outputs augment
R
EPORTS
IPOLAR
Latest BP10B speaker
is even better
S S
PEAKER
each other. In this respect, the BP10 is un-
like dipole radiators such as large electro-
static speakers or similar planar systems
in which the front and rear surfaces radi-
ate out of phase and tend to cancel each
other at low frequencies. Another result of
the BP10's bipolar design is that it oper-
ates best placed about 8 to 12 inches out
from a wall—unlike planar systems,
which must normally be placed several
feet away from a wall.
The BP10's two woofers share a com-
mon enclosure vented by a single ducted
port at the bottom of the rear panel. Ac-
cording to the manufacturer, the bass-
tuning system was computer-designed to
duplicate the loading of a transmission-
line system in respect to its bass response
and transient behavior while retaining the
advantages of a simpler and less ex-
pensive cabinet.
"Definitive Technology's
first product is an unusual
loudspeaker that offers
exceptional performance..."
There was no skimping on the design of
the cabinet, however. Its sides are made of
3/4-inch particleboard, with front and rear
panels of 1-inch-thick Medite (a highly
rigid composition material) and extensive
internal bracing. The cabinet's rounded
edges and narrow profile, plus its frame-
less cloth grille "sock," are designed to
minimize diffraction, which can impart a
boxy coloration to the sound and mar the
spatial imaging.
If it becomes necessary to replace a
driver or perform other internal servicing
of the speaker, lifting the top plate reveals
the drawstring that keeps the grille snug to
the cabinet. After the drawstring is loos-
ened, the grille can be slipped down or re-
moved for access to the drivers or the
crossover network. The designers chose a
fourth-order Linkwitz-Riley network to
give the BP10 uniform response in the
crossover region as well as optimum
phase and transient response. The cross-
over frequency is not specified, but our
measurements suggest that it is in the vi-
cinity of 2,000 Hz.
The BP10 uses rugged, high-quality
drivers. The woofers
magnesium baskets, mineral-filled homo-
polymer cones with butyl rubber sur-
YSTEM
have cast-