If you're in the business of designing the driver from the ground up, use niobium magnets or whatever is top-o'-the-walk these days. That would increase efficiency considerably over ceramic or Alnico magnets. Expensive, but necessary if you intend to give this a fair chance.
The planar drivers approach this. Each diaphragm has only a single, or sometimes double wire (also to include flat aluminum conductors) with what is for all intents and purposes a dedicated magnet. They're low resistance, and have virtually no inductance or capacitance.
The Magnepan direct drive ribbon accomplishes exactly what you're describing. It's a single linear conductor in a magnetic field...that's it. The resistance is on the order of 2 to 2.5 Ohms. Granted, there's no cone attached; the 'voice coil' is the cone, so to speak.
Grey
The planar drivers approach this. Each diaphragm has only a single, or sometimes double wire (also to include flat aluminum conductors) with what is for all intents and purposes a dedicated magnet. They're low resistance, and have virtually no inductance or capacitance.
The Magnepan direct drive ribbon accomplishes exactly what you're describing. It's a single linear conductor in a magnetic field...that's it. The resistance is on the order of 2 to 2.5 Ohms. Granted, there's no cone attached; the 'voice coil' is the cone, so to speak.
Grey
F1 driving MMGs
Do you think that the F1 can drive a pair of MMGs in my 13 x 16 feet living room? I experienced that a 300B tubed single ended (7-8 W) has not enough power. Or should I say that it has not enough CURRENT?
Now I drive my MMGs with a 300W/4 ohm solid state amp, but I am afraid that sometimes it clips (!!!).
Best regards.
Paul
Do you think that the F1 can drive a pair of MMGs in my 13 x 16 feet living room? I experienced that a 300B tubed single ended (7-8 W) has not enough power. Or should I say that it has not enough CURRENT?
Now I drive my MMGs with a 300W/4 ohm solid state amp, but I am afraid that sometimes it clips (!!!).
Best regards.
Paul
The most dramatic case for a current source amp I have heard
is a Lowther DX55 in a sealed box and with a bit of loading
EQ. The differences were not at all subtle, more on the order
of night and day. As you move away from that type of driver
and box, the arguments for a current source become weaker,
and by the time you are running 85 dB woofers in a bass reflex,
you are probably better off with a voltage source.
is a Lowther DX55 in a sealed box and with a bit of loading
EQ. The differences were not at all subtle, more on the order
of night and day. As you move away from that type of driver
and box, the arguments for a current source become weaker,
and by the time you are running 85 dB woofers in a bass reflex,
you are probably better off with a voltage source.
The maggies are a special case because the motor coupling
is weak and the diaphragm is large. The result is an inefficient
speaker with a pretty flat impedance curve (if you neglect
crossovers) and not much need for damping factor. The result
is that the performance is more independent of amp impedance
than other types.
is weak and the diaphragm is large. The result is an inefficient
speaker with a pretty flat impedance curve (if you neglect
crossovers) and not much need for damping factor. The result
is that the performance is more independent of amp impedance
than other types.
I've been watching this dialog with serious interest being a Magnepan owner and having built a transconductance amp recently. No I have not hooked the two together.
The Maggies all have ordinary 2 and 3 way crossovers in them. It's my understanding that these would need to be reworked to operate properly with a current amp. On the other hand if you're using a line level crossover and biamping into just the raw drivers then what is being discussed is valid.
So Mike can you tell me more about the F1/MMG sound? Any more details?
Opinions?
Regards,
Graeme
The Maggies all have ordinary 2 and 3 way crossovers in them. It's my understanding that these would need to be reworked to operate properly with a current amp. On the other hand if you're using a line level crossover and biamping into just the raw drivers then what is being discussed is valid.
So Mike can you tell me more about the F1/MMG sound? Any more details?
Opinions?
Regards,
Graeme
The MMG's are ae the smallest magnepans. They only work down to 100 hz. I have a subwoofer running with them. I have tried most of my DIY amps running them. Aleph, Aleph-X, Krell clone, Zen, MOSFET A40. The F1 seems to put a little more life into them. Maybe I just don't have the eq. right, but it sounds good. 
I'm half-tempted to build one of these lightbulb dinguses just to have something that looks cool.
Five, ten watts? Oh, sure...I'll just hook it up to my old LS3/5a's.
(Yes, for those who were wondering, Grey just made a funny. You can laugh now. [The LS3/5a was notoriously inefficient. Low to mid-eighties dB @ 1W])
Doesn't mean that I don't think they look cool. I've got this irrational idea that I want to use...wait for it...
tube filaments
in place of light bulbs. Think about it. You've got a box. On top are glowing tubes. So obviously you're listening to tubes, right? Only, like the Wizard of Oz, you pull back the curtain and there's a power JFET circuit inside.
Okay, so I have a demented imagination.
Deal with it.
But still, I've got scads of tubes still and you could even use dead ones. As long as the filament is good, you're in good shape.
The idea won't leave me alone.
Grey
P.S.: If someone actually does this before I do, I want credit for the idea. I've even got a few ideas for names, but I'm letting them simmer.
Five, ten watts? Oh, sure...I'll just hook it up to my old LS3/5a's.
(Yes, for those who were wondering, Grey just made a funny. You can laugh now. [The LS3/5a was notoriously inefficient. Low to mid-eighties dB @ 1W])
Doesn't mean that I don't think they look cool. I've got this irrational idea that I want to use...wait for it...
tube filaments
in place of light bulbs. Think about it. You've got a box. On top are glowing tubes. So obviously you're listening to tubes, right? Only, like the Wizard of Oz, you pull back the curtain and there's a power JFET circuit inside.
Okay, so I have a demented imagination.
Deal with it.
But still, I've got scads of tubes still and you could even use dead ones. As long as the filament is good, you're in good shape.
The idea won't leave me alone.
Grey
P.S.: If someone actually does this before I do, I want credit for the idea. I've even got a few ideas for names, but I'm letting them simmer.
The "right" tube will be one with a reasonable resistance on the filament. You could conceivably run several 6550s in series for instance, or you could run a bunch of 12AX7s in series and parallel to handle the voltage and current.
When I get a moment, I'll do a few scratch calculations.
Grey
When I get a moment, I'll do a few scratch calculations.
Grey
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