RL 903K

3-way-coaxial-loudspeaker with cardioid characteristic in bass range

The RL 903K is a main studio control room monitor with cardioid radiation characteristic from 35 Hz through 100 Hz for universal application. Main operational areas are audio, video and motion picture studios.

(shown veneer: ash black RAL9005)

RL 903K

The RL 903K is a main studio control room monitor with cardioid radiation characteristic from 35 Hz through 100 Hz for universal application. Main operational areas are audio, video and motion picture studios. By the cardioid characteristic those reflections caused by the wall behind the speakers are minimized. To enhance the low-frequency range we combined the coaxial arranged high- and mid-frequency driver unit with a powerful long-voice coil bass driver unit. Its coaxial arranged transducers ensure a sound impression with a high degree of homogeneity to a point source. We spend much effort in developing constructive ways to ensure a low degree of non-linear distortion. To keep short-term reflections small and achieve a high fidelity of sound we used a special arrangement for the high- and mid-frequency drivers and also designed the front side of the speaker asymmetrical. Although the cabinets dimensions a very compact, the system obtains a low-frequency cut-off at 35 Hz.

The three-way MOSFET-amplifier with active crossover is situated at the back of the cabinet and is easily accessible for maintenance. An intermittent LED indicates sound pressure levels within the overload margin of 3 dB and warns of clipping. Beyond this limit the output level of the high- and mid-frequency drivers get damped by 20 dB to protect the speaker's components.

Optionally, the coaxial arranged high- and mid-frequency driver unit can be supplied revolved by 90 degrees, that way the speaker can be installed either in vertical or horizontal position. To compensate their placement the speaker features two controllers to continuously adjust the low-frequency response.

There are various stands available as optional extras, which fit in the integrated appliance.


active three-way reference monitor for use in large audio-, video- and film production studios and in mobile broadcast vans

Maximum SPL
from 100 Hz ... 6 kHz

110 ... 115 dB / r = 1 m (3.3 ft) (4 π)


35 Hz ... 20 kHz ± 3 dB

Acoustic output level / PE = - 14 dBu

> 89 dB / r = 1 m (3.3 ft)

Directivity index
from 200 Hz ... 10 kHz

increasing from 4 to 12 dB

Inherent noise sound level

≤ 7 dB (A) / r = 1 m (3.3 ft)

Total harmonic distortion
measured at 96 dB / r = 1 m (3.3 ft)
from 100 Hz ... 10 kHz

≤ - 45 dB

Nominal Input level

+ 6 dBu adjustable

Input impedance

≥ 10 kOhm RC balanced

Electronic Crossover frequencies

250 Hz and 2.6 kHz

Nominal output power MOSFET-amplifier

180 Watt / 4 Ohm
100 Watt / 4 Ohm
100 Watt / 4 Ohm

Input Connector


Loudspeaker systems

200 mm (8") cone
Mid-range unit
160 mm (6.5") cone
25 mm (1") dome

Operation and Clipping indicator

LED on front side

Power requirements

Europe 230 Volt (± 10 %), AC, 50 Hz
USA & Canada 115 Volt, AC, 60 Hz

Power consumption

max. 300 Watt at full load

Mains Connection

IEC power connector

Dimensions (H x W x D)

481 x 285 x 293 mm ( 19 x 11.2 x 11.5 in )


28 kg (61.6 lbs)

Temperature requirements

for use
+ 15°C ... + 35°C (59°F ... 95°F)
for storage
- 25°C ... + 45°C (- 13°F ... 113°F)
45 ... 75 %

Design of the Cabinet

MDF-wood in ash black veneered; optional different veneers or colors
with holding device; optional without holding device

Floor bracket stand RL903K

  • Loudspeaker rotable mounted
  • Deliverable heights (Top edge loudspeaker): 1296 mm (51.0 in), 1411 mm (55.6 in), 1551 mm (61.1 in) and 1761 mm (69.3 in)
  • Base panel (W x D): 520 mm x 450 mm (20.5 in x 17.7 in)
  • Base panel and stabilisation panel veneered
  • Racks black powder-coated

Pedestal RL903K

  • Integrated cable duct in the pedestal
  • Height (Top edge loudspeaker): approx. 1132 mm (44.6 in)
  • Base panel (W x D): 285 mm x 295 mm (11.2 in x 11.6 in)
  • Pedestal veneered

Wall bracket RL903K

  • 30° tilting und 30° rotable
  • Wall bracket black powder-coated

Ceiling bracket RL903K

  • Loudspeaker rotable mounted
  • Standard height between adapter plate and bracket: 300 mm
  • other length available
  • Ceiling bracket black powder-coated

Standard veneer ash black (RAL9005), optional veneers and optional colours

We offer our loudspeakers in standard veneer ash black (RAL9005) or for an additional charge in different optional veneers respectively optional colours. This website provides an overview on the optional veneer and lacquer styles. We are pleased to check if your desired individual veneer and colour can be realised.

Important information about deviations from sample pattern

Wood is a natural product. Even the most thorough manufacturing can result in deviations in colour or structure and is no cause for complaint.
Images are represented differently on every screen and hence not colour-proof.