A wide bandwidth 4 way speaker
system having excellent
transient response, capable of
high sound pressure levels.
WIDE FREQUENCY RESPONSE
20 TO 200,000 cps. +/- 4 Db
SPL’s to 120 Db
EXCELLENT TRANSIENT RESPONSE:
All drivers are operated well
Above resonance - overdamped
LOW L.F. DISTORTION:
12 inch long-throw woofer
with 56 ounce magnet and
effective resonance of 8 Hz’
Recognizing that there are many audiophiles who would like to own a
superlative speaker system but whose pocket books have not been able to
keep pace with the development of their sense of hearing, Dayton Wright
Associates Limited has been trying to develop a lower cost speaker system for some time. Because almost every cost reduction made on the electrostatic speaker system has resulted in a marked reduction in performance, we decided to try and produce a cone speaker system which would embody many of the characteristics found desirable from our work with the electrostatic units.
The result is the Dayton Wright TL-4 Loudspeaker kit.
This unit operates all the drivers such that their operating frequency is well. Above the driver’s resonant frequency! Because the frequency response of the individual drivers does not depend upon the resonant frequency of those drivers to extend their lower response limits, the drivers can be operated with very large magnets, permitting excellent transient response combined with good efficiency; as it does not matter the resonance is over damped.
The woofer is a 12 inch diameter unit having its compliance determined
principally by the rear spider; the surround is used manly for centering
and as an air seal. The woofer is operated vertically rather than horizontally,
and this prevents suspension problems. By placing woofer at
the top of the cabinet there is less excitation of standing waves in the
average room and a consequent reduction in Low Frequency Coloration.
The transmission line has an effective length of approx. 12 feet for a wavelength of 21 Hz. As the initial length of the first section is 4 feet, it is possible to absorb much of the back wave reflections which might cause a problem at 64 Hz. Fillets are used to assure a smooth transition around corners within the transmission line.
The ‘in-line ‘ resonance of the Woofer is about 8 Hz, and this together with the highly damped resonance results in very low low frequency distortion. A foam acoustic resistance in front of (above) the Woofer coneprovides further loading, minimizing effects of room admittence upon response, and also reduces the radiation of the inevitable motion noise of the woofer at high frequencies.
There are two Low/-Mid Drivers, each of them 6 ½ inch diameter units with a free air resonance of about 50 Hz. These operate in a sealed enclosure having two non-parallel sides, over a range of from 150 Hz to 750 Hz. Both have large magnets and butyl front surrounds.
The upper mid range units are located on both the front and rear of
the cabinet - arranged to produce a center, displaced circular pattern
for the whole speaker (which pattern is extended into the tweeters).
They operate well above their resonance of 230 Hz, covering from 750 Hz
to 6000 Hz.
Small cone piezoelectric tweeters are used throughout, three on the front are arranged in a tight vertical array, one is used on each side and one at the back. They are imbedded in the foam block.
A modified 3rd order Bessel derived crossover is used with, a roll off
rate of approximately 18 dB/octave. Air core in inductors are used
throughout excepting for a large-section pair of iron core units used in
the woofer crossover; these were designed so that high currents have very
little effect on the inductence.
The cabinet is available in either rosewood or walnut, the grill being acoustic foam finished in flat black.
The cabinet design is such that all glue joints are hidden. The joints are made with a mastic adhesive similar to a thick contact cement, allowing air-tight joints to be made without clamping. No joints are visible because, of the design; routed grooves are provided to insure that all internal baffles are properly located.
The exposed wood is individually veneered with rosewo6d or walnut to provide good figuring, and a modified oil/wax finish is used to enhance the selected grains.
All wooden parts are numbered and dimensioned so that there can be no inadvertent mis-location of parts.
The completed cabinet stands 53 inches high, with the mid range speakers
located about 42 inches from the floor. The unit is approx. 171/4 wide
by 16” deep and weighs approx. 70 lbs. per speaker. About 6 hours
is needed to assemble each speaker.
DAYTON WRIGHT ASSOCIATES
P.O. BOX 419,,THORNHILL, ONTARIO, CANADA L3T 4A2
Phone (416) 884-3422
HEAR THEM AT:
© 1980, 1999 Wright Electroacoustics
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