Definitive Technology BP7001SC SuperTower, BP2000, F220-B6, F220-B6C, F220-B6E Brochure

I have always liked speakers with unconventional radiation
(i.e., non-forward-radiating) patterns. The first true audiophile
loudspeaker I owned was the KLH 9 full-range electrostatic. This
was in 1972. These speakers had a "you are there" imaging
presence and boxless sound quality I had never heard before.
There were many reasons for this, but an important key to their
performance was the fact that they radiated sound both for­ward and rearward.

To me, imaging is the real magic in a loudspeaker's performance.
All the conventional parameters of a loudspeaker's performance
(linear wide frequency response, low distortion, excellent transient
response, etc.) are important, but imaging is that elusive quality
that brings the musicians into the room or brings you into the
concert hall or into the movie. Imaging allows the suspension of
disbelief and lets you imagine that what you are listening to is
real. The KLH electrostats were wonderful in this regard.

Full-range electrostatic panels of that day, including the
KLH, however, had many shortcomings, including very high price,
large size, difficult power requirements (I used a set of Futterman
output transformer-less vacuum tube amplifiers, which did a bet­ter job than most with problematic electrostatic speaker loads),
limited dynamic range, limited bass performance, positioning dif­ficulties, etc. It seemed to me that it would be fantastic to create
a loudspeaker that brought the benefits of these exotic, impracti­cal panels into a product that made sense for the majority of
listeners in the real world.

I designed my first bipolar loud­speaker in 1973 or 1974, a narrow­format tower incorporating multi­ple small-diameter bass/midrange
drivers arrayed on both the front
and rear baffles along with
piezoelectric tweeters and passive
radiators. It was quite successful in
the marketplace. It also brought me
a phone call from the great loud­speaker designer Jon Dahlquist
(who was also introducing a loud­speaker with a piezoelectric tweet­er—the soon-to-be-famous, time­aligned Dahlquist DQ 10, which was
known for its "boxless" sound) and
led to a long and enjoyable friend­ship between myself and Jon, as
well as with his partner, the
late Saul Marantz. (Marantz not
only founded the company which
still bears his name, but was the
creator of a number of classic
high end audio components; he also
recognized and helped cultivate
design talent in others—including
Jon Dahlquist and

tuner-wizard

Dick Sequerra.)

Issue 3 April 2004

Sounding Board

Definitive Technology’s Sandy Gross on Loudspeaker Design

The Case for Bipolar Loudspeakers with Built-in Subwoofers

Affordable Excellence in Home Theater, Stereo, Film and Music

hris Martens recently reviewed the Definitive Technology BP7001

SC Bipolar

SuperTower for The Absolute Sound (Issue146). During the review process, I

discussed with him at some length two of Definitive's signature technolo­gies, specifically bipolar radiation and built-in powered subwoofers. Chris believed
these concepts would be of general interest to AVguide Monthly readers, and
asked me to write a short piece describing them (without, of course, turning the
article into a 2-page ad for my company).

“…our first product, the BP10 loudspeaker, was also a narrow
tower with basically two complete full-range driver arrays.
One faced forward and the other rearward. This is the basic
concept of a bipolar speaker. The two driver arrays radiate
sound (in phase with one another) in what is basically an
omnidirectional pattern, exactly as sound is radiated in real life
from an original sonic event."

Cross Section of the

Original BP2000

Sounding Board

C

When my partners, Don Givogue and Ed
Blais, and I started Definitive in 1990, our
first product, the BP10 loudspeaker, was also
a narrow tower with basically two complete
full-range driver arrays. One faced forward
and the other rearward. This is the basic
concept of a bipolar speaker. The two driver
arrays radiate sound (in phase with one
another) in what is basically an omnidirec­tional pattern, exactly as sound is radiated
in real life from an original sonic event.
This technology provides a lifelike balance
of early-arrival sound information, which
provides focus, clarity, and location data.
This combines with properly delayed com­plex and somewhat random late-arrival
ambient information (just like the ambience
of an instrument in a concert hall), which
conveys the lush, natural three-dimensional
soundstage of a live musical performance
or cinematically portrayed event. These
effects very much help to make the walls of
the listening room disappear and expand
the apparent size of the listening room into
something that more closely approximates
the sound-space in which the live event
took place. Listeners I've spoken with consis­tently find that the difference bipolar
technology makes is dramatic, involving,
and quite captivating.

There is another benefit of bipolar tech­nology, which is not as important to me as a
critical listener but has been praised by
many reviewers and listeners. Because a
bipolar loudspeaker closely approximates an
omnidirectional sound source, it does a bet­ter job of delivering superior sound
throughout the room for all listeners in that
room. In effect, the "sweet spot" is greatly
expanded—a real-world benefit for listeners
who tend to move around the room or who
share their music listening or movie experiences with friends and family.

Now let me talk a little about built-in powered subwoofers. Definitive
was the first company to introduce the concept of built-in powered
subwoofers to the marketplace—technology that first appeared
in the BP2000 loudspeaker we released several years ago. Interestingly,
our concept grew out of our search
for better-quality audiophile/music
reproduction—not out of a search
for a place to "hide" the subwoofer
in a home theater system. Our belief
was (and still is) that there are sig­nificant advantages (especially for
the subtleties of music reproduc­tion) in having dual stereo sub­woofers that have been specifically
engineered to blend ideally with the rest of the speaker system. In addi­tion, two subwoofers are really a lot more powerful than one. By locating
the subwoofer(s) at the same position as the rest of the speaker system(s),
you also eliminate the inconsistencies related to variable placement of the
subwoofer(s) in the room. We also believe that there are sonic advantages
to stereo subwoofers beyond the obvious ones of better coupling to the
room and more linear response (itself owing to better spreading out of the
excitation of the room's eigenmodes). For exam­ple, you can engineer the subwoofer as an inte­gral part of a true full-range system, as we do in

the Definitive "SuperTowers," rather than
designing a general-purpose subwoofer
that has to be adaptable for use with a vari­ety of other systems. We design our speak­ers to take full advantage of the fact that
they incorporate built-in subwoofers by fur­ther optimizing the performance of the rest
of the system (which no longer has to han­dle the mid- and low-bass frequencies cov­ered by the subwoofers) and by properly
integrating the subwoofers into the system.
This level of integration is very difficult to
achieve with a single stand-alone sub­woofer (since it is tricky to get one sub­woofer to blend equally well with multiple
satellite speakers that are placed several
feet apart). In practice, the subwoofer-with­in-main-speaker idea has really caught on
with the public, though I think some cus­tomers probably value the idea as much
because it eliminates an extra subwoofer
box or two as for the better sound quality it
affords. But I really do want to stress that,
when properly utilized, building a powered
subwoofer into the speaker allows you to
optimize many other aspects of the speak­er's design, and the resulting performance
(at least in the case of Definitive) is clearly
superior for both music and home theater.
Not surprisingly, when the Dolby folks intro­duced Dolby Digital, they demonstrated the
then-new system with a separate subwoofer
for every channel and still recommend this
approach for top performance.

Interestingly, you can also make, as
Definitive does, bookshelf speakers and
center channels with built-in powered sub­woofers. The concept of a built-in powered
subwoofer in the center channel is often
misunderstood. It goes way beyond just
putting more bass energy into the room:

the intent is really to make the center channel a true full-range loud­speaker (i.e., one with extended bass capabilities) in order to give it total
harmonic integrity, which is important for both music and home theater.
Remember that in many movie mixes (and some multichannel audio
mixes —Ed.), the center channel is really the main channel. Because of the

logistics of setting up a home the­ater, the center channel normally
has size limitations. Building in
a powered subwoofer in effect
allows the center channel to
achieve the performance of a large
full-range floor-standing tower.
It can have much the same effect
in bookshelf speakers. Building a

subwoofer into smaller speakers
allows the designer to put some of the performance of a large tower into
moderately sized models.

Definitive Technology SuperTowers are designed on the concept that
bipolar driver arrays and built-in powered subwoofer technologies com­bine to bring more realistic and satisfying musical reproduction into all
home-listening environments. Importantly, these design approaches yield
products that offer many of the advantages of large, exotic, and expen-

sive high-end loudspeakers, but that take up
less space, and that can be built (and bought)
for a fraction of the price.

BP7000

SC (left) and BP7001SC

(right) SuperTowers

"To me, imaging is the real magic in a loudspeaker's
performance. All the conventional parameters of a
loudspeaker's performance (linear wide frequency
response, low distortion, excellent transient response,
etc.) are important, but imaging is that elusive quality
that brings the musicians into the room or brings you
into the concert hall or into the movie."

© Copyright 2004, Absolute Multimedia Excerpted from the April 2004 issue of AVguide Monthly.