Lowther Classic 400 loudspeakers

 The Lowther Classic 400 is one of the company's most spectacular achievements in sound propagation. It employs Lowther's well known internal folded horn principle developed here to a mathematically ideal tractrix curve. This is completed by carrying the sound waves between a wall and the sides of the cabinet to finish as a quarter wave. The cabinet is positioned so that the output from the internal horn is directed towards a wall corner or comparable position acceptable to the room acoustics. A second drive unit in an acoustically coupled compartment serves as the forward facing sound radiator. A five-step ambience control enables the Classic 400 to be ideally matched to suit its environment and the preference of the listener.

Two identical drive units are used in the Classic 400. these are the new hand built PM6's having improved magnet and cone systems and special phase stabilising. No electrical cross-over is used between the units. They are acoustically matched by the unique design of the finely styled cabinet. The Classic 400 will be found compatible with practically any good amplifier in the ten to hundred watts output class although sensitivity is so good that as little as two to three watts can be sufficient for domestic listening needs.

 

Abridged description

Type - Corner-reflector and direct radiator

Units - two new matched PM6 drive units in line, facing rearwards and forwards. The latter gives added presence and reinforced bass response. Because no electrical cross-over device is used between the units, there is no loss of power, no distortion and no coloration from such circuitry

Ambience control - A five stage switchable ambience control is fitted to enable the Classic 400 to be acoustically matched to the room it is heard in. This varies the level of output from the front drive unit as desired.

Impedance - Typically 4 to 8 ohms

Power handling - Capacity up to 100 watts

Size (H x D x W) - 810 x 360 x 250 mm (32" x 14-1/4" x 10")

Finish - American black walnut, teak or satin black with clip-on all-over grilles back and front

Lowther Audiovector speakers

 The finest loudspeaker in the world

The Audiovector is a specialist high performance model embodying all the most sought after virtues in loudspeaker design and performance. Two Lowther drive units designed and made specially for the Audiovector are housed within an acoustically balanced cabinet interior as carefully made as any fine craftsman built organ. This Lowther loudspeaker need no recommendation for being "particularly good on strings", on "male voice" or extremely high or low audio frequencies, for example. The Audiovector renders them all with an astounding faithfulness to create compellingly new listening experience. Only the signal fed to Audiovectors can of itself impair the quality of what is heard. For the intelligent seeker after perfection, the Audiovector alone should satisfy.

 

Abridged description

Sound dispersal - By two Lowther units designed especially for the Audiovector. One is mounted to radiate sound upwards, the other is forward facing.

Impedance - Typically 4 to 8 Ω

Power handling - Capacity 10 - 100 watts

Ambience - A five position switch enables output from the drive units to be matched to the room acoustics as desired

Cabinet - American black walnut or teak with audio transparent grilles at front and top.

Size - 860 x 650 x 406 mm (34" x 25-1/2"  x 18")

Lowther PM6

 PM6 Drive Unit for use with Acousta Enclosures

The PM6 is an 8 inch twin cone unit of similar design to the PM3, plastic foam suspension, aluminum voice coil and a modified form of Stabilizer being used in the construction.

 The magnetic structure, lathough not as large as on the PM3, nevertheless produces a gap flux of 17,500 gauss - well above comparable units. All the benefits attendant with such a large magnetic field are derived - minimum transient distortion - greater efficiency - improved high frequency response. The PM6 has been designed for use in enclosures which provide direct high and mid-frequency rediation and produce the necessary rear loading in the bass range. Mounted in such an enclosure the full capabilities of this drive unit will be realized, ensuring smooth extended bass reproduction free of "boom" and " one not bass", while in the upper range, reproduction will be well balanced and crisp-yet not tiring.

The performance of the Acousta  - or any similar enclosure - will be greatly enhanced when used with the PM6 drive unit,

Due to the high order of efficiency of the PM6, fusing is recommended in order to prevent damage resulting from overloading of the unit.

Specifications

Frequency Range:  20 - 18,000 Hz

Gap Flux:  17,500 gauss

Power rating:  25 Watts (Integrated program material)

Impedance:  16 Ω

Dimensions:  8½" (High) x  8" (Wide) x 5" (Deep)

Weight:  6,5 lbs

Lowther Acousta (1960)

 This extremely well designed enclosure is engineered to complement the Lowther PM6 Drive Unit, providing a performance throughout the audible range that is quite outstanding.

The Acousta employs a folded horn, or exponential labyrinth, which operates from the rear of the drive unit. This structure produces the necessary diaphragm loading at the resonant point of the loudspeaker and provides a reinforcement of the frequencies in the bass range, resulting in a smoother and extended bass response with negligible distortion. The high and mid-range frequencies are obtained by direct radiation from the front of the loudspeaker.

 The Acousta enclosure, moderate in size and price, is ideally suited for contemporary living - without in any way sacrificing performance. Two of these enclosures for stereo reproduction provide a realism in sound that must be heard to be believed. They are offered in both a De Luxe and Standard form.  Standard finishes available are walnut and mahogany. Workmanship throughout is executed by skilled craftsmen, thus ensuring that both performance and appearance are of the highest order. The Acousta is also offered in kit form, allowing the builder to enjoy all the superior performance of this enclosure at a great saving in cost.

Specifications

Acousta Standard

Dimensions (W x H x D):  18-5/8"x 34" x 16-1/2"

Weight:  50 lbs net

Acousta De Luxe

Dimensions (W x H x D):  21" x 34" x 17-1/2"

Weight:  50 lbs net

Lowther TP1 A (1954)

"Built as a music instrument, sounds like a musical instrument.

This amazing development is yet another Lowther contribution to the art of electro-acoustic reproduction.

The most efficient reproducer of audio frequencies in the world with single driver unit/compound horn housing.

Now in use by Television, Broadcasting and Recording studios throughout the world as a standard monitor."

The PM3 Drive Unit used in the TP1 has been designed specifically for this cabinet and is not not available as a separate reproducer. The cabinet is a "compound horn" design utilizing two horns to cover the entire audible range. The smaller of the two, which has its mouth at the grille at the upper part of the enclosure, is for the middle register and treble range-roughly the frequencies from 150 to 22,000 Hz. These frequencies are distributed through the listening space by a reflector type horn of unique design. The source is near ear level (when seated) as it should be. The range below 150 Hz is derived from the back of the driver unit, through a folded horn whose mouth is located on the uderside of the enclosure. This unusual configuration not only utilizes the space below the cabinet itself as an effective working part of the speaker system, but the remainder of the room as well, since the floor and walls (forming the corner) act as extensions of the horn. Thus, the entire range of frequencies is reproduced by true horns, providing performance of unrivalled purity and smoothness, reproduced free of bass resonant devices, cross-over networks, or units added to compensate for others found wanting. Efficiency of the TP1 is of a very high order, the average input for listening use being about 100-200 milli-watts.

Attractively styled the TP1 is available in a modern distinctive design. Construction is of the finest workmanship, using natural woods throughout. Selected veneers hand rubbed to a lustrus finish assure a beautiful apperance. natural walnut and mahogany are standard finishes available from stock.

Dimensions of Lowther TP1

Total Height in corner: 47"

Height to front edge: 42"

Width of front: 32"

From front into corner: 24"

Net weight: 90 lbs

Lowther PM3

An 8 inch twin cone loudspeaker of radically new design the PM3 was especially developed for use in the Lowther TP1 corner enclosure. Possessing one of the largest magnetic structures in use on loudspeakers today, it uses a powerful field to provide phenomenal efficiency over the full audible range.

The two cones-constructed of special material - operate from a single voice coil and divide the audible spectrum. True mechanical crossover permits smooth transition of lows and highd in proper phase and balance without any dips at the crossover frequency.

An outstanding contribution to the performance of the PM3 is the Stabilizer, a (non magnetic) shaped continuation of the center pole partially filling the space inside the tweeter cone. Providing air loading to the cone, it uniformly disperses the frequencies in the high and mid-ranges.

The contour between the Stabilizer and inner cone also forms a short horn for emission direct from the voice coil of very high harmonics and overtones.

The main cone surround is plastic foam. Energy not radiated or absorbed by the cone will reach the periphery and be absorbed in the foam, damping cone resonance in the middle and high frequency ranges. In the bass, because it can stretch, it permits large movements without sudden restrait, minimizing distortion in this range. The rear suspension is also foam, thus preventing reflection at both cone anchorage points.

The voice coil is of aluminum wire, for lightness, and is would half inside and half outside the voice coil former. This form of construction - much stronger than the normal form - makes it impossible for voice coil and former ever to separate under extremes of mechanical stress or temperature.

Forming the heart of the TP1, the PM3 makes an outstanding contribution to the uniformly high efficiency and superior performance of the reproducer.

Specifications

Frequency range: 20 - 22,000 Hz

Gap Flux: 22,000 Gauss

Power Rating: 25 Watts

Impedance: 16 Ohms

Weight: 10 kg

Lowther PM6, PM4, PM2

For the finest sound in the world.
Basically , Lowther design has remained constant from the start since these units function on natural sonic principles which cannot be bettered. But through research, new materials and remarkably improved engineering techniques, Lowther drive units provide fantastically good performance whatever the sound source. These units are intended for use in internal folded-horn cabinets, the designs of which make electrical cross-over systems unnecessary.
Abridged technical specifications of Lowther Drive Units PM6, PM4 AND PM2 are given overleaf.


LOWTHER PM6
Overall Diameter: 228 mm
Overall Depth: 76 mm
PDC Mounting Centres: 208 mm
Baffle hole cut-out: 190 mm
Voice Coil Diameter: 38 mm
Voice Coil Impedance: 8 ohms
Air gap width: 1 mm
Magnet Type: Feroba 2
Flux Density: 1,7 Tesla (17000 gauss)
Flux energy gap Joules x 10³: 705 MJ
Diaphragm: Twin-paper
Frequency response: 20 - 20,000 Hz
Nominal free air resonance: 39 Hz
Sensitivity dB 2 x 10 ⁵ N/M²: 94 dB
Effective Moving Mass: 0,012 kg
Suspension compliance: 1,26 x 10³ M/N
Voice coiltravel: ±1mm
Shipping weight: 3 kg

LOWTHER PM2
Overall Diameter: 228 mm
Overall Depth: 92 mm
PDC Mounting Centres: 208 mm
Baffle hole cut-out: 190 mm
Voice Coil Diameter: 39 mm
Voice Coil Impedance: 8 ohms
Air gap width: 1 mm
Magnet Type: Feroba 2
Flux Density: 2,0 Tesla (20000 gauss)
Flux energy gap Joules x 10³: 976 MJ
Diaphragm: Twin-paper
Frequency response: 20 - 20,000 Hz
Nominal free air resonance: 39 Hz
Sensitivity dB 2 x 10 ⁵ N/M²: 95,5 dB
Effective Moving Mass: 0,012 kg
Suspension compliance: 1,26 x 10³ M/N
Voice coiltravel: ±1mm
Shipping weight: 4 kg

LOWTHER PM4
Overall Diameter: 228 mm
Overall Depth: 102 mm
PDC Mounting Centres: 208 mm
Baffle hole cut-out: 190 mm
Voice Coil Diameter: 30 mm
Voice Coil Impedance: 8 ohms
Air gap width: 1 mm
Magnet Type: Feroba 2
Flux Density: 2,4 Tesla (24000 gauss)
Flux energy gap Joules x 10³: 1400 MJ
Diaphragm: Twin-paper
Frequency response: 20 - 20,000 Hz
Nominal free air resonance: 39 Hz
Sensitivity dB 2 x 10 ⁵ N/M²: 97 dB
Effective Moving Mass: 0,012 kg
Suspension compliance: 1,26 x 10³ M/N
Voice coiltravel: ±1mm
Shipping weight: 6 kg

The above units have a power handling capacity up to 60 watts when suitably housed and may be used with amplifiers up to 100 watts outputper channel.