Hi Everyone,
I have a set of Rullit 8" Classic Field Coil full range drivers, and I have been experimenting with them in some MDF baffles/ open backed enclosures. I really am enjoying the sound and every step of refining the enclosure, etc makes them better still.
My current amp setup is 45 SET based, so pretty low power.
Heres my basic plan:
Rullit full range driver doing most of the work: Maybe 120hz or so to its natural roll-off. Have a super tweeter for that extra bit where it does roll off. (I would be using a super simple capacitor setup as a high pass on both the Rullit and the super tweeter) For the lows, a woofer powered by a DSP plate amp (MiniDSP or Hypex).
My question is, how important is it for the super tweeter and woofer to also be field coil? Obviously there is a cost and lack of (affordable) choices for FC super tweeters and woofers, and then each additional driver requires another power supply, so the cost and complexity gets pretty crazy. In an ideal world it would all be FC etc, but there is always a bit of cost/benefit with all this stuff.
For the supertweeter, I would probably use a Fostex Alnico.. as to the woofer I am unsure.
I have a set of Rullit 8" Classic Field Coil full range drivers, and I have been experimenting with them in some MDF baffles/ open backed enclosures. I really am enjoying the sound and every step of refining the enclosure, etc makes them better still.
My current amp setup is 45 SET based, so pretty low power.
Heres my basic plan:
Rullit full range driver doing most of the work: Maybe 120hz or so to its natural roll-off. Have a super tweeter for that extra bit where it does roll off. (I would be using a super simple capacitor setup as a high pass on both the Rullit and the super tweeter) For the lows, a woofer powered by a DSP plate amp (MiniDSP or Hypex).
My question is, how important is it for the super tweeter and woofer to also be field coil? Obviously there is a cost and lack of (affordable) choices for FC super tweeters and woofers, and then each additional driver requires another power supply, so the cost and complexity gets pretty crazy. In an ideal world it would all be FC etc, but there is always a bit of cost/benefit with all this stuff.
For the supertweeter, I would probably use a Fostex Alnico.. as to the woofer I am unsure.
Short answer: the voice coil does not know who or what creates the magnetic field around it, only its intensity.
Field coils are great at creating impressive flux density, limited only by iron saturation, and in the old days, going from FC to PM, usually Alnico, in some cases it meant "downgrading" speaker performance.
But nowadays I do not doubt permanent magnets can at least match, maybe surpass FC performance, so as long as your Tweeters are properly designed, why not?
Field coils are great at creating impressive flux density, limited only by iron saturation, and in the old days, going from FC to PM, usually Alnico, in some cases it meant "downgrading" speaker performance.
But nowadays I do not doubt permanent magnets can at least match, maybe surpass FC performance, so as long as your Tweeters are properly designed, why not?
JMFahey,
I completely agree in concept. My experience is limited of course, but I am finding that FC has a lot more percussive sort of energy that is very live sounding that I haven't experienced in other speakers (I am also running Zu Druids which are definitely a "fast" speaker). Its not in the bass range, its a snap in the midrange that makes piano notes strike properly, and drums sound a lot more real. Perhaps with a good alnico super tweeter I am out of this range and only accentuating things and it isn't necessary to be FC.. also, on the other end, I would already be running SS for the bass rather than a SET tube, which might make up for the speed difference.
I completely agree in concept. My experience is limited of course, but I am finding that FC has a lot more percussive sort of energy that is very live sounding that I haven't experienced in other speakers (I am also running Zu Druids which are definitely a "fast" speaker). Its not in the bass range, its a snap in the midrange that makes piano notes strike properly, and drums sound a lot more real. Perhaps with a good alnico super tweeter I am out of this range and only accentuating things and it isn't necessary to be FC.. also, on the other end, I would already be running SS for the bass rather than a SET tube, which might make up for the speed difference.
Hi Rich,
I´m mixing fieldcoil and permanent magnet as well, noch problems, even with a passive crossover. I agree with your comments on fieldcoil motors, had the chance to compare the same driver, fieldcoil against ferrite, and choose the more expensive motor.
Snappiness and perceived speed, however, could be achieved with any type of motor.
I´m sure your plans will work well - just get a good supertweeter (have a look into DAVIS cone tweeters, for example: Tweeter a cone Davis Acoustics TW26G-R, 8 ohm, 120 mm or Tweeter a cone Davis Acoustics TW26K2F-R, 8 ohm, 120 mm) and make sure you have a good integration with the main driver. For me that means a lot of listening while tweaking the crossover, but also a few measurements should be relatively sound. If you try the single cap approach, care about the resonance area of the tweeter! Depending on tweeter choice, you might need an RCL notch parallel to control the tweeter.
Good luck and best regards
Mattes
I´m mixing fieldcoil and permanent magnet as well, noch problems, even with a passive crossover. I agree with your comments on fieldcoil motors, had the chance to compare the same driver, fieldcoil against ferrite, and choose the more expensive motor.
Snappiness and perceived speed, however, could be achieved with any type of motor.
I´m sure your plans will work well - just get a good supertweeter (have a look into DAVIS cone tweeters, for example: Tweeter a cone Davis Acoustics TW26G-R, 8 ohm, 120 mm or Tweeter a cone Davis Acoustics TW26K2F-R, 8 ohm, 120 mm) and make sure you have a good integration with the main driver. For me that means a lot of listening while tweaking the crossover, but also a few measurements should be relatively sound. If you try the single cap approach, care about the resonance area of the tweeter! Depending on tweeter choice, you might need an RCL notch parallel to control the tweeter.
Good luck and best regards
Mattes
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