Home > Podcast > AV Rant #737: Interview with Todd Welti on Subwoofers

AV Rant #737: Interview with Todd Welti on Subwoofers

January 25th, 2021

We are proud to present our interview with Todd Welti, Distinguished Engineer at Harman International Inc., and the author of the whitepaper, Subwoofers: Optimum Number and Locations, which is the primary topic of our discussion today. We hear about Todd’s background, and his current setup at home. Then we dig into Todd’s subwoofer research, getting clarification about audience location, subwoofer locations, time alignment, and level matching. We tackle notions about Full Range speakers, “stereo bass”, and crossovers.

Then we expand our discussion to tackle non-rectangular and open rooms. Various ways of addressing such rooms, including CABS, the Geddes approach, and Sound Field Management. That leads to some discussion of ARCOS. And some final, practical simplifications and clarifications before finishing up with some of Todd’s more recent research and modelling of a large number of different rooms and subwoofer and seating locations.

Our thanks to AVRant Listener Joe K. for putting us in touch with Todd. And a huge thank you to Todd for being so generous with his time, and for presenting so much amazing information!


– Subwoofers: Optimum Number and Locations: https://www.harman.com/documents/multsubs_0.pdf

– Audio Engineering Society (AES) Convention Paper 8748: Optimal Configurations for Subwoofers in Rooms Considering Seat to Seat Variation and Low Frequency Efficiency: https://www.aes.org/e-lib/browse.cfm?elib=16490

– Low-Frequency Optimization Using Multiple Subwoofers (includes mentions of avoiding nulls, mode canceling, and Sound Field Management: https://audioroundtable.com/misc/Welti_Multisub.pdf

– Controlled Acoustic Bass System (CABS) “Double Bass Array”: https://vbn.aau.dk/ws/portalfiles/portal/62729209/LF_sound_field_control.pdf and https://www.aes.org/e-lib/browse.cfm?elib=14642

– Earl Geddes multiple subwoofer approach: https://mehlau.net/audio/multisub_geddes/

– Multi-Sub Optimizer Software: https://www.andyc.diy-audio-engineering.org/mso/html/index.html

– History of Multi-Sub & Sound Field Management: https://www.audioholics.com/room-acoustics/history-of-multi-sub-sfm

– JBL ARCOS (Adaptive Room Correction and Optimization System): https://www.jblsynthesis.com/about/arcos.html

– Additional Harman whitepapers: https://www.harman.com/audio-innovations (you can find the graphics that Todd mentions near the end of the podcast here. Look for “Optimal Configurations for Subwoofers in Rooms Considering Seat to Seat Variation and Low Frequency Efficiency: Color Plots”)

– Our YouTube video version (this link will take you straight to the portion when Todd begins showing his graphics & diagrams): https://youtu.be/BZtRNVG078A?t=3283

– Room EQ Wizard: https://www.roomeqwizard.com/

– Cross-Spectrum Labs individually calibrated microphones: https://cross-spectrum.com/

– Rob’s 12 Step Guide: http://www.avrant.com/a-12-step-guide-to-setting-up-dual-subwoofers/

Todd’s contact info:
– Twitter: https://twitter.com/todd_welti
– email: todd.welti at Harman dot com
– Todd’s AES Member Profile: https://www.aes.org/member/profile.cfm?ID=682293182

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