Big speaker, 4 way, Transmission Line.


Stereo Buyers Guide

review & test.

Other documents

Original brochure with certificates.

Drivers reference

Old version : KEF B139, B110A, Celestion HF1300, Celestion HF 2000

New version : IMF 128/20, IMF 5/36, IMF TW 1350 F, IMF TW 2100 F


Based upon the world aclaimed IMF Professional Monitor, the IMF Monitor TILS 80 fulfills the need of the dedicated audiophile for a loudspeaker of comparable quality, but tailored for home use.

Full transmission line loading is retained, the rear of the bass driver being exhausted into a tapered and filtered passageway. The result is an extension of performance, below audibility down to frequencies where bass is felt rather than heard. Colouration is minimised by progressive damping whilst dynamic range is increased. Only transmission line loading can provide the true impact experienced in the concert hall. The individual bowing of the celli to the slap of a bass drum is reproduced within the listening room rather than in a box. If there were a better system of loading than the TLS we would have employed it. The midrange is also contained within its own short line preventing intermodulation and colouration from return waves reflected from the back of the cabinet. Both a tweeter and a super-tweeter are employed to ensure power handling conducive with wide dispersion and extended response beyond the limits of human hearing. The whole system is integrated by a complex crossover, designed as the result of research in depth into the problems of phase correction, impulse response and amplifier matching.

Simultaneously the parameters of roll-off and efficiency compensation have been accommodated to provide an even smoother response than is typical of IMF. The Monitor TLS 80 is fitted with a three position perspective control. In the central normal '0' position the mean hemispherical response is nominally flat whilst the '-' position the mid band energy is tailored to, provide a response which psycho-acoustically increases the effective distance of the listener from the transmitted performance. Similarly, in the '+' position the mid and high frequency are brought forward to provide an integrated response relating to a close listening position such as to enhance some popular music presentations, especially under

conditions of high ambient noise. There is very little that need be said about the sound of the Monitor, which is both neutral yet exciting. Supplied in matched 'mirror image' pairs the stereo presentation is stable, portraying great detail with the uncanny ability to reproduce the acoustic environment of the original performance. We suggest you audition these speakers with the finest ancillary equipment. In the tradition of our monitoring approach to loudspeaker design the IMF Monitor TILS 80 is capable of providing greater satisfaction over a wider range of programme material.


A free standing loudspeaker system measuring approximately 38 1/2" x 16" x 18" wide. Bass unit 11 3/4" x 8 1/4" flat polystyrene diaphragm loaded by transmission line, mid range unit 6" plastic cone containing in separate line, tweeter 1 3/4 " diaphragm and 3/4" chemical dome super-tweeter. Crossover electrical four way at approximately 375 Hz, 3.5 KHz and 13 KHz Frequency range from 20 Hz to beyond audibility. Fitted perspective control - see text - variation in impedance +-1 ohm @ 1.5 KHz. Efficiency measured via Pink noise 1 metre on axis: 40 watts produces 96dB. Nominal impedance matching 4 to 8 ohms. Driving power requirements 40 to 80 watts . Supplied in matched 'mirror-image' pairs in walnut -see cover illustration.

Subject to alteration without notice.


(from the above text)



Free Standing with Plinth; 38 1/2" x 16" x 18" wide

Drive Units

Bass unit 11 3/4" x 8 1/4" flat polystyrene diaphragm loaded by transmission line

mid range unit 6" plastic cone containing in separate line

tweeter 1 3/4 " diaphragm

3/4" chemical dome super-tweeter


Electrical four way at 375 Hz , 3.5 kHz and 15 Khz

Frequency Range

20 Hz to beyong audibility

Frequency- Response & Dîstortion Characteristics

See Graphs


See Polar Diagram

Matching Impedence

4 - 8 ohms (see graph)

Efficiency Measured via Pink Noise at 1 metre on axis for 40 watts


Driving Power Requirements

40 - 80 watts

Subject to afteration without notice.

IMF International, Westbourne Street, High Wycombe, Bucks. Telephone High Wycombe 35576


Conditions of test: Measurements of samples taken under anechoic conditions with reflection coefficient better than 0.1 . Equipment employed B & K pen recorder, noise and signal generator, third octave filters and polar turntable.

Tone burst at bass to midrange crossover

Tone burst at midrange to tweeter crossover