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 Post subject: Inductive Feedback
PostPosted: 09 Nov 2018, 16:15 
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Joined: 09 Nov 2018, 16:04
Posts: 1
I had an idea regarding amplifier design that I wanted to pitch and get some opinions on (possibility, feasibility, or even advice on pushing forward on this potential project).

I am wondering if it is possible to use current induced by a speaker to estimate its instantaneous velocity by taking a difference between a theoretically perfect current draw and the real current draw of that speaker. Essentially, using the speaker coil as a velocimeter and making the feedback system turn any speaker into a servo driven speaker.


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 Post subject: Re: Inductive Feedback
PostPosted: 11 Nov 2018, 22:22 
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Joined: 23 Feb 2017, 02:02
Posts: 227
That sounds like some sort of massive innovation no one has ever done it so cannot answer you.
This could possibly get you a PHD degree.

Shortly speaking its impossible to do what you are trying to do.


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 Post subject: Re: Inductive Feedback
PostPosted: 14 Nov 2018, 05:30 
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Joined: 26 Dec 2016, 03:46
Posts: 160
Location: Bayarea
No idea what you are talking, some drawing might help.


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 Post subject: Re: Inductive Feedback
PostPosted: 14 Nov 2018, 17:10 
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Joined: 04 Jun 2008, 20:59
Posts: 3845
Location: Arizona, USA
Hi, Something maybe similar to what you want to do has been done in the past. Several companies attached sensors to the speaker's cones to measure how they acted when a signal was put to them and used the sensors to provide feedback to the amplifier. A servo type of arrangement. It was supposed to work well at low frequencies and as I recall was used to make compact powered sub woofers.

Good listening
Bruce

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 Post subject: Re: Inductive Feedback
PostPosted: 15 Nov 2018, 19:19 
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Joined: 26 Dec 2016, 03:46
Posts: 160
Location: Bayarea
gofar99 wrote:
Hi, Something maybe similar to what you want to do has been done in the past. Several companies attached sensors to the speaker's cones to measure how they acted when a signal was put to them and used the sensors to provide feedback to the amplifier. A servo type of arrangement. It was supposed to work well at low frequencies and as I recall was used to make compact powered sub woofers.

Good listening
Bruce

Do they have any success? How does that sound?

I think this gets way too complicated. I think if one use an amp that has very low output impedance ( damping factor over 1000), very low inductance speaker cable. You really control the speaker already.

It's not practical to monitor the speaker movement, every speaker is different, they have different phase delay. How is the amp going to do the closed loop compensation for stability if they don't even know what speakers the customer is using.

Stability is a major problem with audio amps, making the speaker as variable can really rig havoc to the stability.

I think OP talked about monitoring the current through the speaker. I don't know whether it works, but at least it's a lot more simple. BUT is that accurate? You monitor the current, part of the current flow through the crossover, not the speakers, so you can be fooled.

I am not going to assume anything, OP need to be more specific before we start guessing.


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