Picture this - put two subwoofer drivers face to face on opposite sides of a baffle. Conect the + of one to the - of the other. Also connect this point to earth. Run the remaing + and - connections to a pair of power transistor emitters, one to each. The collectors go to a positive dc rail. Give the bases a bit of bias but no too much because dc will be flowing in the voice coils. Drive the bases in opposite phase and voila! you have the world's most sorry subwoofer amplifier. Whichever speaker is being driven on it's own half-cycle also drives the other one.
GP.
GP.
Error
Actually, if the speakers are facing each other, both the negatives should go to earth and the positives go to the emitters. I was initially thinking of when the speakers are facing the same way as in an isobaric system. The whole idea could be better appied to a driver that has two voice coils. This time the voice coil phasing would be as I first said. Seeing each coil would only be driven for half the time the total power input capability would remain about the same I think. The efficiency would be slightly lower though because of slightly poorer magnetic coupling.
You know how it is with an auctioneer, how he babbles and jibbers to keep his mouth on the boil between bids? I must be doing the same with my mind between major projects and this is what comes on out instead. Sorry! I'll try to be more sensible.
GP.
Actually, if the speakers are facing each other, both the negatives should go to earth and the positives go to the emitters. I was initially thinking of when the speakers are facing the same way as in an isobaric system. The whole idea could be better appied to a driver that has two voice coils. This time the voice coil phasing would be as I first said. Seeing each coil would only be driven for half the time the total power input capability would remain about the same I think. The efficiency would be slightly lower though because of slightly poorer magnetic coupling.
You know how it is with an auctioneer, how he babbles and jibbers to keep his mouth on the boil between bids? I must be doing the same with my mind between major projects and this is what comes on out instead. Sorry! I'll try to be more sensible.
GP.
Oh, I'm feeling just a bit tired of it for the moment so I have put it aside for for now and am getting a 50wpc class A organised. Also a lotsa-watts weirdo amp that I posted details of somewhere, that I may end up using as a sub amp or something.
I'm only doing it for fun, and if it's not fun then I stop and wait till it is again. It will be, I'm sure.
GP.
I'm only doing it for fun, and if it's not fun then I stop and wait till it is again. It will be, I'm sure.
GP.
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I'll have you know that "worst excuse for an amplifier"
and "sorry excuse for an amplifier" are my private
franchises, having been used in reference to Zen
amps.
On a lighter note, I have built a woofer and a midrange
system using dual voice coil drivers run as a biasing load
for a Son of Zen instead of the 8 ohm resistors. With
only one driver, you can't do too much with it, but if you
start series-ing them to get the voltage up and the
dissipation per driver down, it gets pretty interesting.
and "sorry excuse for an amplifier" are my private
franchises, having been used in reference to Zen
amps.
On a lighter note, I have built a woofer and a midrange
system using dual voice coil drivers run as a biasing load
for a Son of Zen instead of the 8 ohm resistors. With
only one driver, you can't do too much with it, but if you
start series-ing them to get the voltage up and the
dissipation per driver down, it gets pretty interesting.
Most woefully tragic excuse for an amplifier 
The main advantage from my point of view is that you can use exclusively N-channel fets. Mr and Mrs B. Transistor gave some of their N-channel fet children names like "Arnie" etc, whereas p-channels sometimes have names like "Tinkerbell".
GP.
hitsware said:
The main advantage from my point of view is that you can use exclusively N-channel fets. Mr and Mrs B. Transistor gave some of their N-channel fet children names like "Arnie" etc, whereas p-channels sometimes have names like "Tinkerbell".
GP.
My humblest apologies, sire. 'Twas not my intention to profane the beaming splendour of your glorious achievementsNelson Pass said:
On a lighter note, I have built a woofer and a midrange
system using dual voice coil drivers run as a biasing load
for a Son of Zen instead of the 8 ohm resistors. With
only one driver, you can't do too much with it, but if you
start series-ing them to get the voltage up and the
dissipation per driver down, it gets pretty interesting.
Of course the next logical thing to do is put those drivers in a sealed box and apply a either a slight pressure or vacuum (depending on polarity of connection) to the inside of the box to restore the cones to their normal rest position. Simplicity at it's best.
heh hehGP.
Hmm...
With a DVC driver, maybe you could run each coil in class-A such that the DC currents are flowing in opposite directions through the voice coils, thus cancelling out the DC magnetic flux...
Good idea?
You will have to supply opposite phase signals to each coil so that they operate in unison, and if you want, you could make a single balanced amp to do this - maybe even SuSy? Imagine Aleph-X with current sources replaced by voice coils!
That would be a pretty kick-*** sorry-*** amp!
With a DVC driver, maybe you could run each coil in class-A such that the DC currents are flowing in opposite directions through the voice coils, thus cancelling out the DC magnetic flux...
Good idea?
You will have to supply opposite phase signals to each coil so that they operate in unison, and if you want, you could make a single balanced amp to do this - maybe even SuSy? Imagine Aleph-X with current sources replaced by voice coils!
That would be a pretty kick-*** sorry-*** amp!
Beat the heat, cool the coil.
The heat could be a problem for sure. Not a good method for the mass market hifi, but surely within the realms of diy-ism is to drill a little hole through the back of the loudspeaker polepiece plate, that circular piece of metal at the very, very rearmost part of the speaker. Make the hole halfway between the outside circle of the centre polepiece and the inside circle of the ceramic magnet. Attach a tube somehow to this hole and feed air from say a fish aquarium air pump, or maybe from an air compressor with suitable reduction and regulation of pressure. The cooling air should travel along between the centre polepiece and the voice coil. The voice coil dust cap may need to be suitably perforated to let out the air stream. I imagine you should be able to remove quite a bit of heat this way.
GP.
The heat could be a problem for sure. Not a good method for the mass market hifi, but surely within the realms of diy-ism is to drill a little hole through the back of the loudspeaker polepiece plate, that circular piece of metal at the very, very rearmost part of the speaker. Make the hole halfway between the outside circle of the centre polepiece and the inside circle of the ceramic magnet. Attach a tube somehow to this hole and feed air from say a fish aquarium air pump, or maybe from an air compressor with suitable reduction and regulation of pressure. The cooling air should travel along between the centre polepiece and the voice coil. The voice coil dust cap may need to be suitably perforated to let out the air stream. I imagine you should be able to remove quite a bit of heat this way.
GP.
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