That's the thing I was thinking about if you consider the generator a voltage source, then the signal power into the MC case would be much higher. An unfair comparison.
-Chris
-Chris
Richard's feedback system for a speaker won't really work if the coils share the same local magnetic structure. It will act like a lousy transformer and may have more distortion. It would be easy to test with a dual voice coil speaker. (I don't have one or I would explore)
The nearest real world analog is a cutterhead which has feedback coils mounted seperately so they are shielded from the driving fields.
More low level tech on phono cartridges than you might ever want to know: High Fidelity Phonograph Cartridge - Technical Seminar | Knowledge Base | Shure Americas From 1978.
The nearest real world analog is a cutterhead which has feedback coils mounted seperately so they are shielded from the driving fields.
More low level tech on phono cartridges than you might ever want to know: High Fidelity Phonograph Cartridge - Technical Seminar | Knowledge Base | Shure Americas From 1978.
You should try it before proclaiming it wont work. Sure it wont be a signal tightly coupled and exactly like signal coil.... but it can be characterized and shaped -- at least for a limited range such as bass... where distortion is highest in spkrs.
I would assume there are DVC which are wound side by side and also on top of each other. On top of each other would be a better choice.... tighter coupling and same magnetic space for better results using one coil for FB.
CKt at #4015 is rolled off.. bass only.
-RM
Uh or you can just buy a servo subwoofer 🙄
If you really want to improve a speaker it seems like either you need an extra static coil or a field coil ($$$$).
If you really want to improve a speaker it seems like either you need an extra static coil or a field coil ($$$$).
Could the metal detector thing be used with an off the shelf aluminum cone woofer?
The magnetic coupling to the other coil can't be larger than what you would predict from Le. Wouldn't it still be an improvement at bass if Bl modulation isn't a huge issue?
The magnetic coupling to the other coil can't be larger than what you would predict from Le. Wouldn't it still be an improvement at bass if Bl modulation isn't a huge issue?
I’ve never heard a speaker with a woofer servo. In your experiences, what does the servo do for the sound? Is it mainly low f extension or does it change the musical performance like rhythm and pace, imaging or something else?
It is uncommon in home hifi; is servoing used more in pro speakers?
It is uncommon in home hifi; is servoing used more in pro speakers?
Wound on top of each other has some distinct differences. I recommended that exact technique to the ITER guys for the central solenoid. In their case, it is being used to see the IR drop across the superconductors while ignoring the magnetic fields that are running about. The problems were that the eddy losses in the structure (magnetic circuit) look like IR losses as they are in phase with resistive loss. Also, when the plasma initiates, it causes significant changes to the magnetic flux (it is the secondary of this large transformer, and when it switches on it is roughly a million amperes).
The co-wound coil if subtracted from the primary, will give you the value of just the in phase losses in the voice coil, it will ignore all cone motion, coupling, BL nonlinearities, and it will ignore the in phase losses caused by eddy losses in the magnetic circuit (remember, that information is received by the vc by magnetic flux so both coils see it).The pure voltage of the pickup will show the exact magnetic flux the primary sees.
I'd have to think about how these entities could be used to advantage in a woofer.
Jn
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Thanks for sharing the schematic.
Richard, the two expensive and good drivers you have purchased for your subs are dual voice coil ( aluminum wire, 4” diam stainless steel coil former).
http://www.diyaudio.com/forums/atta...s-blowtorch-preamplifier-iii-richards-sub-png
You have the instrumentation to test the magnetic coupling between the two voice coils and study the effect of this in this application.
You can even remove the magnet assy and look inside
Speaker driver with detachable motor and basket
There is more than a dozen of dual voice coil patents if one wants to look for variations in construction.
FPO IP Research & Communities
George
I made one and heard 3 from differents brands.
The first one in the 70 was this one:
GEGO
Trying to find what they have in common I should say
1- A better damping of the speaker. Basses are cleaner, drier and extension of the response curve in the low range. The price was reduced subjective power. I had always a strange feeling of little lack of life or freedom with them and something difficult in the connection with the speakers reproducing the upper part of the spectrum.
I never crossed any servoed speakers in recording studios or big professional PA systems.
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Unfortunately, these techniques are pretty much useless for any bass cab other than sealed back enclosures. The problem is, the energy storage in the system is not directly measured by the vc.
A tapped horn for example, relies on a time shifted back energy. A reflex relies on a buildup of the cab.
Ps. That is why I spoke of half second memory in the dsp. But, it will be best at sine response, transient looks a tad more difficult. In a tapped for example, a step would need another non inverted step when the backwave signal made it through the horn to the cone.
Jn
A tapped horn for example, relies on a time shifted back energy. A reflex relies on a buildup of the cab.
Ps. That is why I spoke of half second memory in the dsp. But, it will be best at sine response, transient looks a tad more difficult. In a tapped for example, a step would need another non inverted step when the backwave signal made it through the horn to the cone.
Jn
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Not before they made a bunch of MFB speakers with real small enclosures and good bass. I still have a pair from 1973. I had a feeling they gave up on them because they where expensive and the public didn't care about them.
EQ in the digital doman. Doing a DA conversion just to add some FR shaping then going back to digital for the X-over doesn't sit well with me however transparent the AD/DA is. Much easier to munge in the DSP.
Of course there is a belief system thing at work here. You have to accept that a well implemented DSP X-over can be as good or better than a well implemented analog one. Some do not believe this.
SONY SA-H7900 Service Manual download, schematics, eeprom, repair info for electronics experts
Very tidy sounding 8" two way with ES highs.
Sensing coil woofer servo worked very well, clean, tight powerful bass, system just needed some minor tweaking to improve overall clarity and inst. dynamics.
Dan.
Very tidy sounding 8" two way with ES highs.
Sensing coil woofer servo worked very well, clean, tight powerful bass, system just needed some minor tweaking to improve overall clarity and inst. dynamics.
Dan.
MFB with complex acoustic loading does work but requires some attention. For example, a ported design needs some give of the cone otherwise the port Q is too high, as high as if the speaker hole in the baffle were covered with a steel plate. Hence, a deliberately low port Q must be dialed in mechanically and it must be very well controlled and stable. Alternatively, we can reduce the feedback around the port resonance.
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