AES British Section lectures - November 2006

Room Perfect DSP Room Correction

Jan Abildgaard Pedersen, Lyngdorf Audio

www.lyngdorf.com November lecturer Jan Abildgaard Pedersen

On November 14th the UK Section of the AES hosted a lecture titled "RoomPerfect DSP Room Correction" by Jan Abildgaard Pedersen, who worked for Bang & Olufsen for more than 10 years and joined Lyngdorf Audio (formerly TacT Audio) last year as CTO. Jan set out to describe how Lyngdorf Audio's RoomPerfect room correction system works.

Jan started with the basics of why room correction is required and described the normal room correction system as performing signal processing before the power amplifier with some feedback from the room.

The RoomPerfect system is novel in that it takes SPL measurements from multiple positions in the listening room as its feedback from the room.

The multiple measurements are power-averaged and used to calculate a set of gain limits to use when generating the correction filter for a specific listening position. Jan pointed out that using multiple measurements has many benefits including taking into account the three dimensional nature of the room, not having to use smoothing to compensate for the local peaks and being able to do automatic target selection.

Jan then discussed why he had picked multiple pure tones as the test signal for the RoomPerfect system. The benefits include the fact that from a steady state system any (linear) properties of the room can be determined, long analysis windows can be used which improves frequency resolution and long analysis times can be used to improve the SNR.

Another feature of the RoomPerfect system Jan talked about is the automatic generation of the target curve, taking into account the characteristics of the loudspeakers actually used, so that no standard curve is forced onto the loudspeaker.

Jan finished up by showing the results of the RoomPerfect system on the SPL at the listening position. He pointed out that as the RoomPerfect system takes into account the global effect of the room, the room correction improves the signal throughout the room even when optimizing for a specific listening position.

There followed an extensive question and answer session. A recording of the lecture is available from the UK section website at www.aes.org/sections/uk/meetings/a0611.html.

Report by Tim Harris