2 ms·

"real-time modeling of the woofer mechanics" reminds me of those Philips Motional Feedback speakers [2] my parents bought in the late '70s [2]. Instead of digit

"real-time modeling of the woofer mechanics" reminds me of those Philips Motional Feedback speakers [2] my parents bought in the late '70s [2]. Instead of digital "real-time modeling" they used an analog feedback loop to control and correct woofer cone movement. These were self-contained active speaker cabinets containing a 35W (later also available in 75W) amplifier and two or three speakers with the feedback mechanism controlling the woofer. They did not have wifi or an always-on microphone, true, but the former is easily remedied (use a Raspberry Pi Zero or something similar) while the latter is more of an advantage than a disadvantage. [1] http://www.extra.research.philips.com/hera/people/aarts/_Philips%20Bound%20Archive/PTechReview/PTechReview-29-1968-148.pdf http://www.extra.research.philips.com/hera/people/aarts/_Phi... [2] http://hifipig.com/philips-motional-feedback-speakers/ http://hifipig.com/philips-motional-feedback-speakers/

Arve 9y ago
Apple's approach goes a fair bit beyond simple servo control (which only tends to work well for truly low-frequency content. While Apple hasn't disclosed much about the particular details, it's bound to be in the same vein as Klippel's work, which doesn't use feedback as much as it monitors a few states as input to a feed-forward error-correcting mechanism. The net result is that distortion is lower, and it's much less limited with regards to the frequency range you can support. [1] http://www.audioxpress.com/article/louder-faithful-and-consistent-using-digital-signal-processing-to-improve-loudspeaker-performance http://www.audioxpress.com/article/louder-faithful-and-consi... [2] https://www.klippel.de/fileadmin/_migrated/content_uploads/ACTIVE_REDUCTION_OF_NONLINEAR_LOUDSPEAKER_DISTORTION_02.pdf https://www.klippel.de/fileadmin/_migrated/content_uploads/A...

Arve 9y ago

Apple's approach goes a fair bit beyond simple servo control (which only tends to work well for truly low-frequency content. While Apple hasn't disclosed much about the particular details, it's bound to be in the same vein as Klippel's work, which doesn't use feedback as much as it monitors a few states as input to a feed-forward error-correcting mechanism. The net result is that distortion is lower, and it's much less limited with regards to the frequency range you can support. [1] http://www.audioxpress.com/article/louder-faithful-and-consistent-using-digital-signal-processing-to-improve-loudspeaker-performance http://www.audioxpress.com/article/louder-faithful-and-consi... [2] https://www.klippel.de/fileadmin/_migrated/content_uploads/ACTIVE_REDUCTION_OF_NONLINEAR_LOUDSPEAKER_DISTORTION_02.pdf https://www.klippel.de/fileadmin/_migrated/content_uploads/A...