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Insert headphones

Microphone preamplifier

Binaural microphones

Rotating Turntable

Spherical loudspeaker

Custom-made heavy-duty turntable for electro-acoustic measurements

I devised a medium-duty turntable for my high-quality fully automated HRTF measurement / multi-modal experimentation system. The KAR-961b turntable has a hybrid step motor, attached to an angle gear box (1:100) that is able to rotate smoothly a maximal load of 180 kg.


The KAR-961b turntable has a plywood construction, with a lower disc diameter of 800 mm and upper disc of 1000 mm diameter, and a total height of ca. 200 mm. The upper disc, lying on multiple rack casters. rotates while the lower disc is bolted to the floor construction. Due to a special double upper disc design, the turntable acts itself as a capstan roller for the cabling used for the equipment placed on top of the rotating disc. This allows a heavy set of cables (a maximal bunch of ca. 70 mm in diameter, length of ca. 4 m and weight approx. 15 kg) to be spun around the capstain. (The rotation is limited to the thickness and weight of the cable bunch, the above yields ca. +/- 3 full revolutions). The turntable has multiple fastening positions (3/8" screws) for microphone stands etc. on the upper plate, and holes for floor fixing on the lower disc.


The KAR-961b turntable is controlled via RS-485 / RS-232 connection to any computer running a run-time version of LabView. The control interface can be commanded and freely programmed by any API sending simple ASCII commands, such as MATLAB. Also, the turntable can be controlled manually by a remote control. All the stepper motor power electronics is located inside the turntable, so that no pulsed high currents need to be transferred via cables to the turntable. Accordingly, the functioning of turntable yields minimal disturbance to electro-acoustical measurements.


Download the product specifications in PDF below.

KAR Klaus A J Riederer HRTF system including KAR-961b turntable in the large anechoic chamber at HUT Acoustics and Audio Signal Processing laboratory
KAR-961b turntable (+ loudspeaker framework for the HRTF measurement system) in the large anechoic chamber at HUT Acoustics and Audio Signal Processing laboratory. KAR-961b turntable (and (spherical loudspeaker framework of the HRTF measurement system in the large anechoic chamber at HUT / Acoustics and Audio Signal Processing Laboratory.