The Reference Standard Professional Monitor Mk. IV loudspeakers are specifically designed as laboratory devices for use in the aid of subjective evaluation of programme and ancilliary equipment. No commercial compromises have been made in their development, nor have aesthetic considerations detrimentally affected design or construction. The result is a truly faithful yet ruthless transducer which provides the engineer with the maximum information regarding the source material being fed into it.
The loudspeakers are supplied in matched mirror image pairs with the drive units clustered inwards to give a skewed polar distribution, away from wall boundaries so that the listener receives the maximum of direct information, less intermingled with reflections. Despite their size, the speakers are designed to be used on stands provided. These ensure that the
loudspeakers are supported off the floor, reducing room colouration components. Importantly the stands slightly tilt the speakers back, maintaining a substantially flat response both axially and hemispherically together with proper phase coherence at high frequencies. Finally but interrelatedly, they lift the loudspeakers to the correct listening elevation.
The full transmission line loading incorporates new damping techniques and materials. Initially the enclosure is lined with a dense antidrumming material, the heterogeneous matrix of which provides an optimum deadening interface. Acoustic foam, as used in anechoic chambers, is then 'sculptured' to produce a wedge effect where the maximum surface area is exposed to damp the line, yet presenting the minimum of restriction. The separate midrange line is similarly terminated whilst standing waves are progressively absorbed by long hair wool.
The necessarily complex crossover network is situated behind a removable panel at the bottom of the grill front. As well as proportioning the audio spectrum into the correct phase and amplitude relationship for each drive unit, pre-set controls are provided to equalize the loudspeakers to their acoustic environment. A low frequency filter is incorporated which can be switched to give varying degrees of protection from unwanted near sub-sonic bass cone motion. Two further controls affect adjustment of the energy response in the midrange and treble, each switch function being made fine yet supplying a wide range of configurations.
The advantages of transmission line loading, as pioneered by us, are well known. Extended bass performance is complimented by unusually low colouration. The Reference Standard Professional Monitor Mk. IV exhibits the lowest distortion characteristics of any loudspeaker so far produced. This, together with research in depth into maximum phase congruence, results in a loudspeaker of outstanding neutrality. The professional will particularly appreciate this, enabling decisions about the quality of programme signal to be made without undue allowance for loudspeaker idiosyncrasies.
Overall height on stand : allow 46" (117 cm)
Drive Units 11 ¾" x 8 1/4" 30 cm x 21 cm flat polystyrene bass unit loaded by transmission line
6" 15 cm plastic cone midrange in separate line
1 ¾" 4.5 cm diaphragm high gauss tweeter
¾" 2 cm chemical dome super-tweeter
Crossover Electrical four way at 350 Hz, 3 kHz and 13 kHz
Frequency Range 17 Hz to beyond audibility
Frequency Response & See Graphs Distortion Characteristics
Dispersion See Polar Diagram
Controls FILTER : see graphs and text
TILT: +/- 1 dB : 300 Hz to 15 kHz
SLOPE: +/- 1 dB : 2 kHz to 15 kHz
Matching Impedance 4-8 ohms See Graph
Efficiency Measured via Pink 96-98 dB dependant on Control settings Noise at 1 metre for 40 watts
Driving Power Requirements 50-150 watts
Nett Weight (each) 46 kilos
Gross Weight packed (each) 56 kilos
Nett Weight of Stands (each) 8 kilos
Gross Weight of Stands 22 kilos packed (pair)
Gross Weight Consignment 134 kilos (pair with stands) packed
For further information request Technical Data Sheet RSPM IV.
Westbourne Street High Wycombe Buckinghamshire Tel High Wycombe 35576 Telex 83545
2142 Trans Canada Highway Dorval PQ Canada H9P 2N4 Tel (514) 683 7662 Telex 05822847
Home of the Transmission Line Loudspeakers > IMF Electronics > Speakers categories > The Reference's > RSPM Reference Standard Professional Monitor >