Sony G90 - Manual (Page 44)

plished with gain biasing to the surround channels, either. I
set up the speakers fair and square. But clearly, the T770’s
steering in DD mode is precise and smooth.
Finally users are going to have to decide for themselves
which features they can and can’t live without. At its suggested
list price, the T770 faces some stiff competition from AVRs with
higher stated power ratings and prodigious features. Now I’m
not a big bells and whistles fan. If I want to drive fast, give me
direct input of a gated manual five speed from a n y era Ferrari,
not the “fly by wire” computer electronics of a clutchless Ti p-
tronic. The same goes for audio and video. I want to see and hear
the unadulterated material reproduced as intended. A great
many poseurs impress with their sizzle. But as single-chassis
designs go, the NAD T770 is all steak.
NAD ELECTRONICS OF AMERICA
6 Merchant St.
Sharon, Massachusetts 02067
Tel: (781) 784-8586; fax: (781) 784-8386
Website: www.nadelectronics.com
Source: Manufacturer loan
Price: $1,699
M a n u f a c t u r e r I n f o r m a t i o n
Manufacturer’s Response
NAD would like to thank Neil Gader for his
thoughtful review of the T770 receiver.
One point I would like to elaborate on is his
assertion that speaker sensitivity and impedance should be
carefully evaluated for compatibility with the T770’s 70-watt x
5 power rating. While he is correct in the absolute sense, the
T770 incorporates an exclusive NAD amplifier design, imped-
ance-sensing circuitry, which endows the NAD with the ability
to properly drive 4-ohm speakers by maintaining the correct
relationship between voltage and current irrespective of the
loudspeaker being driven. This is accomplished automatically,
requiring no adjustments from the listener. The T770 is stable
even at 2 ohms!
As Neil mentions in his opening paragraph, we rate our powe r
for A-V products the same way we rate our stereo amplifiers,
that is, all channels driven simulta n e o u s l y, 10 Hz – 20 kHz, at
0.08 percent T H D. Most manufa c turers would have rated the
T770 at 100 x 2, 20 Hz – 20 kHz at 0.08 percent THD and 100 x
5 at 1 kHz. We believe our conserva t i ve approach is more in
keeping with our “music first” approach to A-V products.
GREG STIDSEN
DIRECTOR OF SALES AND MARKETING
NAD ELECTRONICS OFAMERICA
W e are grateful to manufacturers
for correcting any errors of fact
in our reviews. When we can,
we also include the manufacturer’s com -
ments following a review. But sometimes
space does not allow us to do that and
this section gives us the opportunity to
include a cogent comment while the sub -
ject is ripe, rather than holding it over for
inclusion in another issue.
RPG Diffuser Systems,
Inc., Room Optimizer
I ’d like to commend Tom Miiller for ta ck-
ling a ve ry challenging task (“Revel Ulti-
ma Speaker System Episode One: Th e
Ancient Enemy,” this issue). Episode
One is a wonderful attempt to raise the
awareness of our community to the
acoustical distortions a room can intro-
duce. RPG has been conducting room
acoustics research for 16 years, sharing
our results with the acoustical and enter-
tainment industries through peer rev i ew
publications, seminars at CEDIA, NSCA,
the Audio Engineering Society, and the
Acoustical Society of America. Ove r
time, it became apparent that despite
the progress we have made in room-
acoustic design, sound diffusion, and
absorption tech n o l o g y, recording stu d i o s
and residential hi-fi and home-theater
communities were still at the mercy of
the location of the loudspeakers and the
l i s t e n e r. In researching existing pro-
grams to assist in these two areas, we
found that the solution lay in a new
a p p r o a ch that simultaneously addressed
modal coupling and speake r- b o u n d a ry
i n t e r ference response (SBIR), the two
causes of low-frequency acoustic distor-
tion. A technical description of this new
algorithm was presented at the AES and
a copy can be down-loaded from our
website (www. rpginc.com). One can
address this problem using wave
acoustics, called the frequency- ove r l a p
method, or by geometrical acoustics,
using the image model. Both approach e s
are difficult to apply. The recta n g u l a r
room offers a unique case in which both
r e s o l ve into simple and identical solu-
tions. The image model, howeve r, is the
d e fault solution, since it is time-based
and can be windowed to provide the
SBIR and modal responses. The issues
are how to deal with the SBIR and modal
coupling simultaneously and how to
s e a r ch the millions of possible solutions
for the best one. Simultaneous treat-
ment of SBIR and modal coupling wa s
easily addressed by using the we i g h t e d
smoothness (standard deviation) of both
responses, and an intelligent search
engine (downhill simplex, in this ve r s i o n )
was used to search through error space
for the best answe r. One thing to keep in
mind is that this type of problem
requires optimization of many va r i a b l e s
at one time. This type of problem con-
tains the possibility of false solutions.
The goal is to find the global minimum. The starting point always affects the
solutions, so the program allows for the
evaluation of many random sta r t i n g
points. Each solution is valid and users
should choose the solution that has the
smallest error and the best ergonomic
placement. Once loudspeaker and listen-
er positions are established, the pro-
gram indicates optimum positions on
walls and ceiling for absorptive and diff u-
s i ve materials to control the mid-high
frequency portion of spectrum. It is
i m p o r tant, though, to remember that the
o b j e c t i ve is envelopment in the A - V
experience, and this cannot be accom-
plished by sound absorption alone. Th e
acoustical palette consists of absorption,
reflection, and diffusion. The best room
can be ach i eved by an appropriate com-
bination of these. Deader is not better!
While users are generally astonished
at the difference proper placement can
provide, some tweak the positions the
program generates. The program will find
the locations that generate the best room
response within its stated assumptions.
While a flat room response may be math-
ematically preferable, listeners have dif-
ferent hearing acuit y, musical tastes, and
musical training. So let the Room Opti-
mizer get you close, then tweak to taste.
We are committed to expanding and
i m p r oving the Room Optimize r, and
users’ comments are welcome.
PETER D ’ ANTONIO , PRESIDENT
RPG DIFFUSOR SYSTEMS , INC .
Manufacturer’s Corner