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IMF Electronics Studio TLS-50

Transmission Line Speaker (1976)

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IMF Electronics Studio TLS-50


The TLS 50 II retains the full transmission line loading of the Monitor loudspeakers.

A transmission line provides for the driver a near ideal acoustic environment and the reputation of the TLS for low colouration and extended bass performance is well established.

The TLS 50 II employs a bextrene cone bass unit with large pole and huge magnet, allowing long excursions without distress or undue overhang.

The quality of the bass response is very special. 'Line' bass is different from the 'box' bass of conventional speakers. It is free, more dynamic and exists in space rather than in an enclosure. The bass line forms a pressure loading device so that low frequencies are felt, rather than heard.

Both the TLS 50 ll and the ALS 40 II employ the same midrange, wide dispersion tweeter and complex crossover configuration which includes phase correction circuitry to compensate for unit spacing.

The TLS 50 II however, also boasts a super-tweeter which further extends the high frequency performance well beyond audibility and as such compliments the plane source propagation of the line, down to sub-sonic frequencies.


Type: 3 way, 4 driver loudspeaker system

Frequency Response: 23Hz to 20kHz

Recommended Amplifier: 30 to 70W

Crossover Frequency: 375, 3000, 15000Hz

Impedance: 4Ω

Sensitivity: 97dB

Bass: 1 x 205mm bextrene cone

Midrange: 1 x 100mm cone

Tweeter: 1 x dome

Super Tweeter: 1 x dome

Enclosure: active transmission line

Weight: 27kg

Year: 1976



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Reviewed Mar 06th, 2015 by desertdog

Brilliant speaker, slightly smaller than tls80 but still far better sounding that most others around even now. Posted 2015



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