What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Acoustic Research AR 11 (1977)

The AR-11 is the most accurate speaker system ever made by Acoustic Research. Its performance, drivers, and crossover are identical to those of the AR-10π, except that the Ar-11 does not incorporate a Woofer Environmental Control and the associated crossover components. The AR-11 is designed for optimum performance when placed against a wall, as on a bookshelf, or slightly away from two room surfaces, as illustrated.

The AR-11 uses a substantially improved version of the 305 mm (12 in) woofer with which Acoustic research introduced the acoustic suspension principle to home listeners, as well as the hemispherical dome midrange of the AR-3a. It also uses a newly designed 19 mm (3/4 in) highrange based on the original high-frequency dome radiator introduced by Acoustic Research in 1959. This highrange driver incorporates new diaphragm materials, voice coil, and construction techniques that have produced significant improvements in performance over earlier versions. it has a lower resonance frequency and more extended high-frequency response, plus greater efficiency and higher available output.

These drivers are used with a new crossover network to produce a speaker system with uniformly dispersed flat energy output to the highest audible frequencies. It is able to transmit the information from a program source to listeners in most locations in a room with an unprecedented degree of accuracy.

A pair of three-position switches provide a means of decreasing the overall level of the midrange and highrange drivers in 3 dB steps. The "0" position of the switches should provide the most listening rooms, while the "-3 dB" and "-6 dB" settings are useful for compensating for the effects of more reverberant, or "live" rooms.

The AR-11 shares many of the appearance features of the AR-10π, including an easily removable precision-machined foam grill, which was chosen for its near-perfect acoustical transparency.


Drive units:

Woofer: acoustic suspension 305 mm (12 in)

Midrange; hemispherical dome 38 mm (1½ in)

Highrange: hemispherical dome 19 mm (¾ in)

Crossover frequencies: 525 Hz, 5000 Hz

Impedance: 4 Ω nominal

Efficiency: 86 dB 1W/1m

Controls: two 3-position switches for midrange and highrange level control

Driver resonance frequencies:

Woofer: 18 Hz (free air)

Midrange: 400 Hz

Highrange: 2000 Hz

System resonance frequency: 42 Hz

Effecive system Q: 0,7

Total flux:

Woofer: 200,000 maxwells

Midrange: 70,000 maxwells

Highrange: 21,000 maxwells

Flux density:

Woofer: 9,800 gauss

Midrange: 13,000 gauss

Highrange: 14,000 gauss

Crossower network:

Half-section LC network on each driver using air-core chokes and computer grade electrolytic capacitors, acoustic output of midrange and highrange driver is controlled by switchable resistive networks.

Power requirement:

Minimum 25 watts per channel for an averge room, to obtain a closer approx. of the minimum power required, in continous RMS watts per channel for the realistic reproduction of musical sound levels in a perticular room, divide the volume of the listening room, measured in cube feet by 100; 25 watts (into one speaker only) will produce 100 dB SPL in a 3000 cu ft room of average reflectivity (energy absorption coefficient of 0,15); 50 watts (25 watts per channel) will produce 103 dB SPL in the same room

Power-handling ability:

Maybe used with amplifiers capable of delivering up to 150 watts continuous power per channel being driven to clipping 10% of the time, on normal music source material

Volume of enclosure: 41,9 liters (1,48 cu ft)

Dimensions (W x H x D): 354 x 635 x 273 mm (13 x 25 x 10¾ in)

Weight: 2,6 kg (49¾ lb) unpacked

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