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three π subwoofer performance data

three Pi subwoofer Our three "π" subwoofer is a moderately sized high-fidelity subwoofer, suitable for critical listening or home theater. It is the perfect complement for any of our main speakers, or for any others, for that matter.

While a single subwoofer can be used, it is much better to use two to four subwoofers. A pair of subs, flanking the mains, will not only provide deep bass extension but also smooth lower midrange, believe it or not. The way to do this is to set the subs a few feet below, beside and behind the mains. Flanking subs are run to relatively high frequency, around 90Hz to 120Hz, second-order. The mains aren't high-passed, but instead overlap with the flanking subs. This way, self-interference from nearest boundaries is mitigated. Flanking subs greatly improve response smoothness in upper half of the room’s modal region, up to 150Hz to 200Hz.

To smooth the lower frequency room modes, add another pair of woofers further away from the mains, using the LFE subwoofer channel to drive them. The distributed subs serve to smooth the lower half of the room's modal region, below 100Hz. The low-pass frequency is generally 60Hz to 80Hz, which prevents any localization problems.

Frequency Response



  • All measurements were done groundplane, with the speaker and the microphone resting on the ground.
  • No post-processing or smoothing was applied.
  • Measurements were taken at a distance of 10 feet from the baffle and drive voltage was 6.1vrms. This is equivalent to 2.0v/M and 1W/1M values since average impedance is 4Ω.
  • The loudspeaker was driven with a 60Hz sine at 20vrms to pre-heat for 15 minutes immediately before measurement. This was done to bring it to a realistic operating temperature.

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Helpful Documents and Software

π Speaker Whitepaper explains the concepts and evolution of modern waveguide and constant directivity loudspeakers
π Speaker Crossover Document analysis of circuits used in waveguide and constant directivity loudspeakers
"Crossover Electronics 101" Seminar Handout
JBL Professional Sound System Design Manual
Passive Crossover Spice models, complete with the AIM Spice modeling program
Pialign Analysis Software to help you design your enclosures. This is the old Altair original from 1977.
Plot the response curve of your design with Carlson's BoxPlot program
Plot the response curve of horns with the HornResp program
Convert Metric and Imperial measurements with the Madison Measurement Converter

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