ALS 40
Medium size speaker, 3 way, Active Transmission Line.
Drivers reference
Tweeter : unknown; medium : unknown, bass: unknown.
The Studio TLS 50 Il and the Studio ALS 40 Il are based on the
original IMF transmission and active line systems but include radically
redesigned enclosures, crossovers and loudspeaker drivers. The speakers
are provided left and right handed. The units are clustered together in
a mirror image arrangement between the pair giving a skewed polar
distribution inward, away from wall boundaries, so that the listener
receives the maximum of direct information, less intermingled with room
reflections. Thus stereo presentation is sharp, stable and consistent
over a very wide listening area. Such freedom of seating arrangement is
usually only associated with systems of indeterminate imagery.
The TLS 50 Il retains the full transmission line loading of the IMF
Monitor loudspeakers. A transmission line provides for the driver a
near ideal acoustic environment and the reputation of IMF TLS for low
colouration and extended bass performance is well established. The TLS
50 Il employs a bextrene cone bass unit with large pole and huge
magnet, allowing long excursions without distress or undue overhang.
The qualily of the bass response is very special. 'Une' bass is
different from the 'box' bass of conventional speakers. It is free,
more dynamic and exists in space ralher than in an enclosure. The bass
line forms a pressure loading device so that lovv frequencies are felt,
rather than heard.
Both the TLS 50 Il and the ALS 40 Il 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 w'hich furthe extends the high
frequency performance well beyond audibility and as such compliments
the plane source propagation of the line, down to sub-sonic frequencies
Despite ils generous proportions, the floorstanding IMF TLS 50 Il
represents the smallest enclosure in which full passive transmission
line loading can be properly maintained. Thus in the somewhat smaller
bookshelf ALS 40 Il an additional bextrene sub-woofer is fitted at the
end of the line to enhance low frequency efficiency and extend the bass
response below that which is typical of such an enclosure size. This
extra bass unit is electrically driven via the crossover network and is
of dissimilar but interelated resonance to the upper bass unit and to
the length of lirie. As such, the 1 active' transmission line (ALS) is
a stage removed from the slave units employed with reflex enclosures.
Performance adequately justifies the increased cost and extra
complexity.
A secondary advantage of the ALS principle lies in increased power
handling, especially at very low frequencies. Each bass unit provides a
termination for the other, behaving as a sub-sonic filter giving low
frequency protection superioreven to that under infinite baffle
conditions.
Both the Studio ALS 40 Il and the TLS 50 Il are fitted with a three
position perspective control. In the central normal '0' position the
mean hemisperical response is nominally flat whilst in the '-' position
the mid band energy is tailored to provide a response which
psychoacoustically increases the effective distance of the listener
from the transmitted performance. Similarly in the '+' position the mid
and high frequencies are brought forward to provide an integrated
response to a close listening position such as to enhance some popular
music presentations, especially under conditions of high ambient noise.
These Studio speakers do fulfull their design criteria, to vvork
properly under a wide range of acoustic conditions, conveying very
little of themselves or the room but the utmost of the programme fed
into them.
Nominal specifications
STUDIO ALS 40
Dimensions
Bookshelf mounting or Stand; 13 1/2" x 13 1/2" x 26 1/2" high; 35 cm x 35 cm x 68 cm
Drive Units
8" 20.5 cm bextrene bass unit
8" 20.5 cm bextrene sub-bass unit
4" 10cm rolled surround impregnated cone mid-range with domed tweeter
Crossover
Electrical four way at 150 Hz, 375 Hz and 3 kHz
Frequency Range
28 Hz 20 kHz
Frequency- Response & Dîstortion Characteristics
See Graphs
Dispersion
See Polar Diagram
Matching Impedance
4 - 8 ohms (see graph)
Efficiency Measured via Pink Noise at 1 metre on axis for 40 watts
98dB
Driving Power Requirements
25 - 60 watts
Nett Weight (each)
18 1/2 kgs
Gross Weight Packed (pair)
24 kgs
Subject to afteration without notice.
IMF International, Westbourne Street, High Wycombe, Bucks. Telephone High Wycombe 35576
Graphs
Pictures