Low distortion, DSP based high gain servo controlled woofer controller. - Page 3 - diyAudio
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Old 18th June 2013, 02:35 PM   #21
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Quote:
Originally Posted by hunter audio View Post
Dear David ,

Kindly drop your email id to dasgupta.s@outlook.com .

Suranjan
email sent as requested

regards
david
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Old 18th June 2013, 09:22 PM   #22
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Do you think you could create an algorithm from the servo measurements to allow it to be removed from the driver and controlled by DSP? Or maybe use an alternative device?
If a dsp could be developed to reduce driver distortion... some serious possibilities would open up
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Old 19th June 2013, 11:17 AM   #23
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Originally Posted by nannoo View Post
Do you think you could create an algorithm from the servo measurements to allow it to be removed from the driver and controlled by DSP? Or maybe use an alternative device?
If a dsp could be developed to reduce driver distortion... some serious possibilities would open up
There has been a lot written about predistortion over years but I have yet to a see a practical working implementation when it comes to speakers. The problem is that the speakers characteristics change over time and with different power levels etc. There are just too many variables to make a reliable inverse model. In any event some sort of sensor is still needed to measure the speaker such as an accelerometer or precision microphone so you may as well go the extra distance and employ feedback of some kind

Looking at it another way. Would you apply this methodology to an audio amplifier when it would be simpler or more prudent to use negative feedback ?

regards
david

Last edited by Tranquility Bass; 19th June 2013 at 11:22 AM.
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Old 19th June 2013, 11:54 AM   #24
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A simple sensor makes a lot of sense, it just wasn't an idea I had considered! can't help but wonder if an optical sensor of some kind could be developed... I know that laser pickups have been successfully developed for use on guitar...

My thought process is that the way we are heading in consumer hifi is to all in one speaker systems:

wireless receiver>>DSP (EQ, Digital xo, distortion reduction [feedback from optical sensor?])>>DAC>>digital amplification>>drive units

starting to wonder if the DAC needs to move though
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Old 19th June 2013, 12:11 PM   #25
superR is offline superR  Netherlands
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I have evaluated optical sensors for the use of feedback, but a 20 dollar accelerometer was the most sensible way to go.
I looked at this sensor;
Extreme dynamic laser sensor with anti speckle feature | Micro-Epsilon America
The use of such sensor brings in more trouble than that of mounting a accelerometer to your woofer.
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Old 19th June 2013, 12:36 PM   #26
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I think experiments with a more intuitive, analogue DIY sensor may be in order....
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Old 19th June 2013, 12:39 PM   #27
superR is offline superR  Netherlands
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I think we can agree on that
The ACH01 is a great little device for this purpose. David, have you implemented the gain stage from the spec sheet?
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Old 19th June 2013, 01:16 PM   #28
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Am I reading that spec sheet correctly? Mass is 8 grams?
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Old 19th June 2013, 02:16 PM   #29
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Have you considered using the second voice coil as the feedback signal source instead of an accelerometer?
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Old 19th June 2013, 02:35 PM   #30
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I think we can agree on that
The ACH01 is a great little device for this purpose. David, have you implemented the gain stage from the spec sheet?
The measurements of the speaker that are made by the software are inclusive of the additional weight of the accelerometer so everything is accounted for These days most woofers have cones that weigh between 100-500 grams depending on the size of the driver so an extra few grams of mass from the accelerometer is barely going to make any difference from an efficiency standpoint. It may lower the resonant frequency by a whisker but that is still not an issue in this design as any changes are accounted for

regards
david

Last edited by Tranquility Bass; 19th June 2013 at 03:04 PM.
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