pmr@drutx.UUCP (Rastocny) (09/05/84)
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(Re: What type of equipment does Phil R. have?, part 5.)
Loudspeakers:
The loudspeakers are of my own design with a fourth-order Butterworth
woofer alignment (Thiele was right), crossover network is a Zobeled and
compensated second-order Butterworth passive. All crossover components
are hand matched to each of the eight drivers using air-core high-Q
chokes, and mylar and polystyrene capacitors. The networks were tuned
with the assistance of both a Gold Line 1/3 octave real time analyzer,
a General Radio SPL meter, and an HP programmable function generator.
Driver complement is a Becker 12" woofer, Dynaudio 2 1/2" dome midrange,
and two Panasonic 4" leaf tweeters, all arranged in a vertical array.
The tweeter pair is raised about 1/2" at their intersection to improve
vertical dispersion. All drivers are flush mounted and then caulked to
reduce first reflections. The internal wiring is hand-made from #26
wire-wrap wire wound in a true Litz configuration, effective wire size
is #11. The enclosures are made from 1-3/16" high density particle
board and oak veneered. The grills are a unique non-reflecting design
covered in black loose weave burlap. Position of the loudspeakers was
described in part 2 of this series.
The sound of the system:
The sensitivity of this loudspeaker is about 95dB/W/m at 1KHz and the
maximum SPL of the system is measured at better than 120dB peak. The
measured response of the system is plus or minus 2dB in the primary
listening position from 30Hz to beyond 20KHz at one Watt. The sound
stage is wide, high, and deep. The focus is tight and well defined but
slightly better on the left side due to the window flanking the right
loudspeaker.
(The phenomenon commonly referred to as a "sound stage" is most often,
and incorrectly, used to describe an illusionary two-dimensional sound
plane consisting of top-to-bottom height and left-to-right width. Quality
sonic reproduction has not only this plane but also front-to-back
depth giving the sound stage a sense of three-dimensions without the
aid of additional synthesis (e.g., Carver's holograph). Good systems
have sound stages that are several feet deep, several feet high, and
wider than the centerlines of the loudspeakers. Excellent systems have
sound stages that are several tens of feet deep, higher than the ceiling,
and several feet wider than the outside of the loudspeakers. This system
is the latter.)
("Focus," for those not familiar with this word, is a term used to
describe how well the playback system maintains the position of an
instrument/vocalist within its sound stage. Good focus allows one to
perceive an instrument/vocalist in one position with a small amount of
drift that pulls the image usually left or right. Excellent systems
retain a tight, rock-solid position of the instrument/vocalist with no
hint of drift in any of the three dimensions. This system is the latter.)
----------
Responding to the questions "Why not place things on the walls to soften
up the room?" and "Why not make the room with non-parallel walls?" my
answer to both is that I compromised. (Compromise? I bet you thought I
didn't know the meaning of the word. :-) You see I live with the home's
interior decorator (my wife) and she refuses to look at any form of
sound-absorbing panels or whatever on the walls or ceiling. The carpeting
is the best I could do. Rooms in the shape of solid rectangles are also
less expensive to build and much easier to sell than multi-sided
acoustically-perfect environments.
Yours for higher fidelity,
Phil Rastocny
AT&T-ISL
ihnp4!drufl!pmrmat@hou4b.UUCP (Mark Terribile) (09/06/84)
Internal loudspeaker wiring is hand-wound Litz with an effective cross-section
of #11 ! Holy cow, Phil, how did you get it on the voice-coil bobbins :-) !
Seriously, Phil, you do have my respect for the effort you put in. By the
way, have you thought of publishing your designs?
--
from Mole End Mark Terribile
(scrape .. dig ) hou5d!mat
,.. .,, ,,, ..,***_*. (soon hou4b!mat)