Tannoy Westminster
The Tannoy Westminster presents the latest in Dual Concentric technology combined with traditional standards of construction and finish, and is a worthy successor to the renowed tannoy Autograph.
A 15" Dual Concentric drive unit is coupled to a straight axis horn at the front and to a long folded horn at the rear. The advantages of the system are as follows; Low frequencies, i.e. below 300 Hz are reproduced by a much larger radiating wavefront loudspeakers. the quality of low frequencies as perceived by a listener are more realistic since low frequency sound radiations in musical instruments, etc., are also generated by large radiating wavefronts. For example, timpani, contrabass, organ pipes (32 ft. 16 ft.) producing low frequencies naturally, all have a basic wavefront generating area much larger than even a 15-inch (380 mm) direct radiating loudspeaker system. The radiating area of the rear folded horn in the Westminster loudspeaker is over 2,5 times that of a 15 inch loudspeaker and therefore much more comparable to the original instruments. The quality of low frequency reproduction is therefore improved. The efficiency of the system, used in the Westminster is approximately 8 dB greater than conventional direct radiating systems using a 15-inch drive unit. A fundamental consequence of the increase in efficiency is a lower distortion content when operated at normal domestic sound levels. A further consequence of high efficiency is of course that the power amplifier is under much less stress when reproducing high peak transient sound levels typical of wide dynamic range digital recordings. The air load matching between drive unit and listening environment is improved by the use of compound horn techniques, therefore the drive unit is much less highly stressed in reproducing peak transient levels. The thermal dissipation in the voice coil is reduced resulting in a more linear conversion of quiet and loud passages, i.e., the true dynamic range of the programme material is retained.
Using conventional separate bass and treble units with a rear folded horn would result in an extremely large and cumbersome cabinet. The tannoy Dual Concentric drive unit has separate high and low frequency drivers within a common chassis. Integration of the drive unit and horn loading systems with the cabinet is therefore more effective and the physical size of the cabinet reduced.
In the Dual Concentric drive unit a single chassis carries both a direct radiating low frequency driver and, mounted behind and on the same axis, an HF compression driver.
When used in the Westminster with a time compensated crossover network, a single point sound source is provided for frequencies from which the listener can re-create stereo images. The result is a much clearer, more accurate stereophonic effect. Lowe frequencies which do not affect stereo imagery are reproduced through the rear folded horn.
The resulting sound quality available from the Westminster produces a sense of reality and presence which is simply not provided by any more conventional loudspeaker system.
The finishing touch to this fine loudspeaker is provided by the superbly finished cabinet, combining solid walnut mouldings and real walnut veneers with discrete oatmeal grille cloth. The centre grille is removable with a key for access to the HF response controls.
1. The compound horn construction shown in diagrammatical form with the rear horn straightened out for clarity.
2. Perspective view of Westminster cabinet showing the internal construction of the rear horn. Arrows show the direction of radiation from the drive units.
Specifications
Power Rating: 120 W RMS, 300 W Peak
Amp. Rating: 50 to 200 W RMS per channel (8 Ω)
Sensitivity: 96 dB (for 1 W at 1 m)
Maximum SPL:
117 dB at 1 m for 120 W
123 dB at 1 m for 500 W peak
Impedance: 8 Ω (Nominal) 5,5 Ω (Minimum)
Frequency vs SPL: 18 Hz - 20 kHz
Phase Response: 80 Hz - 10 kHz ±12°
Time Compensation: less than ±10 µsec (80 Hz - 10 kHz)
Dispersion: 60° incl. ang. Horizontal - Vertical at -6 dB at 10 kHz
Crossover Frequencies: 1 kHz electrical, 300 Hz acoustical
Crossover Control:
±6 dB over 1 kHz to 20 kHz shelving
+3 dB to -6 dB per octave over 5 kHz to 20 kHz slope
Crossover Type: Passive, Low loss, Time comp. type 1027
Driver Type: Dual Concentric, High Compliance type 3839/W
Distortion
Less than 2% third harm, at half-power, 80 Hz - 20 kHz
for 90 dB SPL less than 0,3% third harm, 50 Hz - 20 kHz
for 110 dB SPL less than 1m4% third harm. 80 Hz - 20 kHz
for 113 dB SPL less than 3,0% third harm. 80 Hz - 20 kHz
Low Frequency Direct Radiator
Nominal Diameter: 380 mm (15")
Voice Coil Diameter: 52 mm (2")
Free Air Resonance: 22 Hz
Total Q: 0,18
High Frequency Direct Radiator
Diaphragm Diameter: 51 mm (2")
Voice Coil Diameter: 51 mm (2")
Horn Lower Cut off Frequency: 250 Hz
Enclosure Type: Compound Horn
Rear Folded Horn:
Total Length = 3 m (10 feet)
Throat Area = 0,03m2 (49 sq in)
Mouth Area = 0,4m2 (620 sq in)
Flare Constant = 0,85 (exponential)
Front Horn
Total Length = 0,15 m (6 in)
Throat Area = 0,075m2 (116 sq in)
Mouth Area = 0,31m2 (480 sq in)
Flare Constant = 9,7
Enclosure Volume: 521 litres
Enclosure Dimensions (H x W x D): 1300 x 1030 x 631 mm
Enclosure Weight: 115 kg complete
packed Dimensions (H x W X D): 1500 x 1100 x 7200 mm
Packed Weight: 140 kg
Enclosure material: Solid walnut with 25 mm particle board
Grille Material: Specially woven cloth over wood frame with lock and key fixing
