Todd Welti

Subjective comparison of single channel versus two channel subwoofer reproduction

Bass management has many advantages for surround sound listening, however there is still a question regarding audibility of two channel versus single channel bass reproduction. Many previous investigations have lacked rigor or been preliminary in nature. The study presented here includes strict control of nuisance variables and significance testing of results. A test is described wherein trained listeners compared four different subwoofer configurations in controlled listening tests, using a very sensitive triangle test, in a typical listening room. Methods of controlling nuisance variables are discussed. These include double blind testing, equalizing all responses flat below 120 Hz, and allowing pre‐training for the listening test. Critical selection of audio test loops using low frequency decorrelation is discussed. Results are presented.

Subwoofer optimization in rooms for consistancy and efficiency

Early work on optimizing subwoofer placement in rooms focused on trying to minimize variations in sound power response by optimizing room dimensions. Some consideration has also been given to maximizing overall sound power output, typically by putting subwoofers in room corners. Recent research using a sophisticated computer model has instead focused on trying to minimize variation of magnitude response from seat to seat. Using the same computer model, optimal subwoofer configurations are identified, which give consistent seat to seat responses and maximize low frequency efficiency. Consideration is given to different room dimensions and different seating configurations. The resulting plots may be very useful in designing small rooms with full range audio playback systems and multiple seats.

Investigation of Bonello criteria as a practical tool in small room acoustics

The Bonello criteria are often used as an objective metric for assessing room dimensions with respect to modal response. In reality, the modal response is not simply a property of the room dimensions, but is quite dependent on source/receiver locations as well. The legitimacy of Bonellos criteria when used in rooms with typical subwoofer and seating configurations has not been well investigated. In this study, a room model is used to calculate room responses for a large number of combinations of room dimensions, subwoofer positions, and seating locations. The Bonello criteria are evaluated for each combination and compared to perceptually relevant criteria such as flatness and seat to seat consistency of the calculated acoustical responses.

A comparison of listener loudspeaker preference ratings based on insitu versus auralized presentations of the loudspeakers

Auralization methods have several practical and methodological advantages for studying the perception of loudspeaker reproduction in rooms. For subjective measurements of loudspeakers, the auralization should be capable of eliciting the same sound quality ratings as those measured using an original acoustic presentation of a loudspeaker. An experiment was designed to test whether this is possible. Listeners gave preference ratings for both acoustic (in situ) and auralized double‐blind presentations of four different loudspeakers, and the results were compared. The auralized presentations were generated from binaural room‐scanned impulse responses of the loudspeakers convolved with the music test signals and presented over headphones equipped with a head‐tracking device. For both in situ and auralized methods nine trained listeners gave preference ratings for four different loudspeakers using four different programs with one repeat (eight trials in total). The results show that the auralized and in situ pr...