Implementing wave field synthesis in an ITU spec listening room part 2: Bass without modes

Hargreaves, JA; Wankling, M

Abstract

In recent years various sound reproduction systems have been proposed which attempt to use multiple transducers to tame the modal behaviour often prominent in rooms at low frequencies. Of particular interest is the Controlled Acoustic Bass System (CABS) proposed by Celestinos and Nielsen, and it was decided to install a permanent system in our ITC spec. listening room. A number of constraints had to be considered, not least positioning the subwoofers so as not to compromise the existing passive acoustic treatment. A system comprising eight subwoofers was implemented and rear delay and attenuation were fine tuned to minimise deviation from a flat frequency response over the listening area. The result was a significantly more uniform frequency response and the elimination of the most prominent tonal artefacts. This allowed corrective equalisation to be applied giving the system a nominally flat response over its operating frequency range of 30Hz to 120Hz.

Citation

Hargreaves, J., & Wankling, M. Implementing wave field synthesis in an ITU spec listening room part 2: Bass without modes. Presented at Reproduced Sounds 2011, Brighton

• Presentation Conference Type: Lecture
• Conference Name: Reproduced Sounds 2011
• Conference Location: Brighton
• End Date: Nov 17, 2011
• Publication Date: Nov 16, 2011
• Deposit Date: Jan 16, 2012
• Publicly Available Date: Apr 5, 2016
• Keywords: Acoustics Bass CABS
• Related Public URLs: http://www.reproducedsound.co.uk/
• Additional Information: Event Type : Conference; References : [1] ITU-R BS.1116-1, “Methods for the Subjective Assessment of Small Impairments in Audio Systems Including Multichannel Sound Systems”, International Telecommunications Union, Geneva, Switzerland (1997) [2] IEC.60268-13, BS.6840-13, “Sound System Equipment – Part 13: Listening Tests on Loudspeakers”, International Electrotechnical Commission, Geneva, Switzerland (1998) [3] Celestinos, A., & Nielsen, S.B. “Controlled Acoustic Bass System (CABS) A Method to Achieve Uniform Sound Field Distribution at Low Frequencies in Rectangular Rooms”, Journal of the Audio Engineering Society 56 (11): 915 – 931 (2008) [4] T. Welti and A. Devantier, “Low-Frequency optimization using multiple subwoofers”, Journal of the Audio Engineering Society 54 (5): 347 – 364 (2006) [5] J. A. Pedersen, “Sampling the Energy in a 3D Sound Field”, Audio Engineering Society 123rd Convention, New York (2007) [6] Avis, MR, Fazenda, BM and Davies, WJ, “Thresholds of detection for changes to the Q-factor of low frequency modes in listening environments”, Journal of the Audio Engineering Society, 55 (7/8): 611 – 622 (2007) [7] L. Elmer, B. Fazenda, M. Wankling and J. Hargreaves, “The subjective perception of room