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"Triodity" to cancel loudspeaker distortion
"Triodity" to cancel loudspeaker distortion
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Old 12th June 2019, 11:03 PM   #11
Nelson Pass is offline Nelson Pass  United States
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"Triodity" to cancel loudspeaker distortion
By this naive approach, actual lower distortion has been measured.

I leave the sophisticated approach to others.

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Old 13th June 2019, 12:36 AM   #12
olen is offline olen  United States
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"Triodity" to cancel loudspeaker distortion
Itís well understood that cone position (displacement) is directly related to the voltage across the speaker terminals throughout the passband, itís also pretty well understood outside of the passband.

The complication lies in the fact that loudspeaker distortion varies with displacement, Klippel has a lot of great information on this, look up LSI:

The LSI parameters are typically shown for free-air operation, keep in mind they change when you put the loudspeaker in an enclosure. Ideally a loudspeaker in an optimal enclosure will have symmetrical curves. Conversely, you can start with a perfectly symmetrical speaker in free air and get worse symmetry once itís placed in an enclosure.

Hereís a article/paper on how DC offset relates to distortion:
DC displacement – dynamic offset the voice coil
This is technique typically used to determine if the voicecoil is offset, typically in prototype speakers. You adjust the DC offset to find the minimum distortion and from that you can tell how far your rest position is offset.


Originally Posted by Mark Tillotson View Post
Alas the distortion of a speaker is primarily related to the cone position (ie due to suspension forces and voicecoil position), not the voltage across the terminals, and the relationship between voltage and cone position varies substantially across resonance. This probably scuppers chances of naive cancellation.

Without a cone position/velocity/acceleration sensor, the next best way to cancel speaker distortion is perhaps sophisticated model and MPC (model predictive control) techniques. Very compute intensive.
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Old 13th June 2019, 09:31 AM   #13
Circlomanen is offline Circlomanen  Sweden
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The simple fact that you can use the superficially perceived "flaw" of a simple single stage, single end amplifier to lower the distortion through cancellation instead of relaying on dumb brute force methods like many cascaded gain stages and copious amounts of negative feedback is truly an ingenious use of synergistic effects.

Thank you Mr Pass!!! Your articles about Triodes, SITs and amplifier design in general have really tough me a lot!!!
We live in a horizontal world, why use vertical topologies???
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