I have a 3886 amp that I'll be hooking this to but not for a few days (or maybe after Christmas the way things are going). I ordered these boxes for the test: Amazon.com: Absolute SQ6.5PKB 6.5" Square Box Speakers, Set of Two (Black) with Speaker Terminal: Cell Phones & Accessories I have a response curve I can post later. It is something of a full range driver.
Sorry John
I have no DVC driver, let alone a DVC wound like you suggest.
But what about a circuit that would drive a 1:1 single bobbin transformer in place of the DVC driver (primary as the driven coil, secondary as the sense coil, )?
Wouldn't all the nonlinearities due to the magnetic circuit be linearized?
George
It should. It also allows you to change the magnetic non linearities as a test of functionality.
If you run it with a reasonably high level, say half the VA, you could then bring a large neo magnet up against the core to saturate part of the core in one direction. Without the compensation, you should see wild things happen to the pickup voltage. With comp, the pickup voltage should be stable until the amp bites the dust, and in the meantime, you would see the distortion on the drive voltage in it's attempt to compensate the non linearities.
jn
Good, thanks.
I guess I have to follow this circuit:
John Curl's Blowtorch preamplifier part III
For to make things a bit easier, can I use only one op.amp (the power amp chip) in inverting mode like I have sketched in the attached photo?
If yes, the Rs value should be 1k?
George
Attachments
Yes. This is what I put in post #11255
If you want to see something interesting, put a pair of diodes antiparallel across your variable resistor and watch the amp attempt to linearize (except, it might kill the amp as it rails into the inductor..sorry). Better yet, put a resistor in series with the antiparallel diodes across the primary, this is to simulate a magnetic non linearity..
If you want to see something interesting, put a pair of diodes antiparallel across your variable resistor and watch the amp attempt to linearize (except, it might kill the amp as it rails into the inductor..sorry). Better yet, put a resistor in series with the antiparallel diodes across the primary, this is to simulate a magnetic non linearity..
Attachments
Last edited:
Jneutron, am I correct to say that the inductance of the coil is higher when it's velocity is high because it causes the eddy current path to become longer?
As I understand the DVC circuit (as conceived initially) will behave like current drive, except the matching of the coils will be the limit on the effective series impedance. So if the coils are mismatched by 10%, the effective series impedance (if compared to current drive) will be no more than 80 ohms (or more like the EMF has been reduced to 10%). The coil leakage remains in series with the resistance and so if your leakage is 400nH, the effective 80 ohms will be 80R+4uH (Bifilar wound coils would have very low leakage).
As I understand the reason this would work better than current drive is because by changing coil position/geometry we can be selective about which EMF sources we allow to affect cone motion. However I don't think there is any useful way to extract different EMF sources using this method, and I see no application benefits over current drive. Any failure of the coils to couple perfectly results in a reintroduction of EMF which resembles lower drive impedance, but worse because differing magnetic nonlinearities between the two coils are added in.
As I understand the DVC circuit (as conceived initially) will behave like current drive, except the matching of the coils will be the limit on the effective series impedance. So if the coils are mismatched by 10%, the effective series impedance (if compared to current drive) will be no more than 80 ohms (or more like the EMF has been reduced to 10%). The coil leakage remains in series with the resistance and so if your leakage is 400nH, the effective 80 ohms will be 80R+4uH (Bifilar wound coils would have very low leakage).
As I understand the reason this would work better than current drive is because by changing coil position/geometry we can be selective about which EMF sources we allow to affect cone motion. However I don't think there is any useful way to extract different EMF sources using this method, and I see no application benefits over current drive. Any failure of the coils to couple perfectly results in a reintroduction of EMF which resembles lower drive impedance, but worse because differing magnetic nonlinearities between the two coils are added in.
Last edited:
responses in red.
jn
I prefer bifilar or my co-wound coils because that produces the exact same magnetic non linearities. You are correct in that if the pickup coil sees something the drive doesn't, that would not be good.
jn
I would think with such a cheap DVC driver we could actually achieve a noticable improvement with an optimized amp for it, hopefully quite cost-effective. How that amp conceptually will actually look like, well that's the fun part of this, isn't it? I look forward to contribute to this when I have the drivers. I wasn't aware of this 6.5" DVC which would be ideal to complement a small current-driven cheap fullranger (3"...4") in a nice active FAST project.
I look forward to you contributions, thank you for the efforts.
I would think with such a cheap DVC driver we could actually achieve a noticable improvement with an optimized amp for it, hopefully quite cost-effective. How that amp will actually look like conceptually, well that's the fun part of this, isn't it?(absolutely. If we can add a lower octave and drop harmonics simply by unsoldering one feedback resistor and adding connectors to the second coil, that would be ideal (as well as my goal for a diy project for all)) I look forward to contribute to this when I have the drivers. I wasn't aware of this 6.5" DVC which would be ideal to complement a small current-driven cheap fullranger (3"...4") in a nice active FAST project.
jn
jneutron, your circuit can be solved to Re in series with 2 EMF sources opposing each other, one per coil. If one coil is 90% coupled to the other coil, the total EMF is 10% of the original EMF. So it's like 90% current drive, letting 10% of the EMF back in.
If the coils are not perfectly coupled that implies they don't occupy the same physical space, which means the leakage flux paths will encounter different nonlinearities. So you could scale the output of one coil to match the EMFs, but there will be a residual which contains only distortion. So the distortion reduction when compared to equivalent impedance drive will be less than expected. Although with bifilar winding the coupling could be very high.
Also, no rejection of thermal compression.
If the coils are not perfectly coupled that implies they don't occupy the same physical space, which means the leakage flux paths will encounter different nonlinearities. So you could scale the output of one coil to match the EMFs, but there will be a residual which contains only distortion. So the distortion reduction when compared to equivalent impedance drive will be less than expected. Although with bifilar winding the coupling could be very high.
Also, no rejection of thermal compression.
A 6.5" subwoofer and a 3-4" fullranger.....sorry, you've lost me
Because he didn't call it WAW?
//
- Status
- Not open for further replies.