Found these drivers on e-bay then found the makers website thought these were very interesting to say the least the look like Large format Altec's that have been heavily modified the wooden back cap is to cool looking. Also checkout the measurements from the makers site pretty damn impressive.
CHFC1BW Chela Audio Field Coil Drivers 1 4" Port | eBay
CH Audio Design
CHFC1BW Chela Audio Field Coil Drivers 1 4" Port | eBay
CH Audio Design
sean19,
I bought a pair of CH Audio field coil converted 806 drivers about 3 yrs ago but have not had the chance to hook them up yet. I do have a pair of field coil converted JBL 2441 drivers with Truextent be diaphragms on 25.5" Sierra brooks wood horns and they sound excellent. I also have re-maged stock 2441 drivers that I have tried with the be diaphragms which also sound excellent. The difference between the field coil 2441 and standard 2441 drivers are slight but very noticeable in direct comparison. The field coil version plays down to 250hz measured in room while the stock version plays down to 350hz but I cross over at 450hz. The field coil version sounds a little fuller and with more snap along with excellent clarity, imaging and tone. The upper mids and treble sound very similar with the field coil being slightly better overall. If I had to put a number on the stock JBL 2441 with be diaphragms as compared to the field coil version with be diaphragms I would say the stock drivers are 90 to 95 percent of the field coil version. Just remember that this is a comparison in my system so YMMV. One other advantage of the field coil driver is you can vary the "Q" slightly by increase or decrease of the field voltage between 12v and 16v.
Getting back to the CH Audio converted 806 driver, I have a 400hz tractrix kit horn from Fastlane Audio that I will install and have a friend measure the performance of the combo in the near future. We shall see.
I bought a pair of CH Audio field coil converted 806 drivers about 3 yrs ago but have not had the chance to hook them up yet. I do have a pair of field coil converted JBL 2441 drivers with Truextent be diaphragms on 25.5" Sierra brooks wood horns and they sound excellent. I also have re-maged stock 2441 drivers that I have tried with the be diaphragms which also sound excellent. The difference between the field coil 2441 and standard 2441 drivers are slight but very noticeable in direct comparison. The field coil version plays down to 250hz measured in room while the stock version plays down to 350hz but I cross over at 450hz. The field coil version sounds a little fuller and with more snap along with excellent clarity, imaging and tone. The upper mids and treble sound very similar with the field coil being slightly better overall. If I had to put a number on the stock JBL 2441 with be diaphragms as compared to the field coil version with be diaphragms I would say the stock drivers are 90 to 95 percent of the field coil version. Just remember that this is a comparison in my system so YMMV. One other advantage of the field coil driver is you can vary the "Q" slightly by increase or decrease of the field voltage between 12v and 16v.
Getting back to the CH Audio converted 806 driver, I have a 400hz tractrix kit horn from Fastlane Audio that I will install and have a friend measure the performance of the combo in the near future. We shall see.
Thats awesome you have and use field coil drivers they are what started high end & pro sound we know today. It's nice to still see people into them. So whats your theory on why the field coil sound slightly better? Is it because permanent magnet fields weakens when voltage is introduced into that field through the voice coil and with a electro magnetic field it dose not ?
sean19,
Since I am not a mechanical or electrical engineer I can only say what I was told by a couple people who actually make ( Cogent ) and use field coil drivers. There are much more qualified people in the DIY audio community who can explain the science behind the function of the field coil.
The explanation that make sense to me is that the field coil acts like a larger storage battery that can create a higher flux density in the gap of the driver depending upon the voltage selected and the number of coil turns and AWG of the wire used. Some drivers use different materials and shape / design of the phase plug. However ,like most things in life, there are compromises such as the need for an external power supply / battery cost, size and some added noise to the driver. A quiet ,clean power supply is necessary and at the moment I use a variable Lambda lp 531 fm 0 - 20v 5 amp lab supply. I will experiment with other power supplies in the future.
Since I am not a mechanical or electrical engineer I can only say what I was told by a couple people who actually make ( Cogent ) and use field coil drivers. There are much more qualified people in the DIY audio community who can explain the science behind the function of the field coil.
The explanation that make sense to me is that the field coil acts like a larger storage battery that can create a higher flux density in the gap of the driver depending upon the voltage selected and the number of coil turns and AWG of the wire used. Some drivers use different materials and shape / design of the phase plug. However ,like most things in life, there are compromises such as the need for an external power supply / battery cost, size and some added noise to the driver. A quiet ,clean power supply is necessary and at the moment I use a variable Lambda lp 531 fm 0 - 20v 5 amp lab supply. I will experiment with other power supplies in the future.
There is a lot more to making a linear motor system than the type of magnet used - field coil, ceramic/ferrite, neodymium or otherwise. There is no real advantage to using a field coil - they were popular long ago because they were cheaper, smaller and lighter than fixed magnet variants. Alas, fixed magnet technology has changed quite a lot on all three fronts since then.
You've summed it up quite well. The biggest advantage of field coils is to control the Qts via the magnetic field but since tweeters or midrange drivers aren't used at the fs, it's not important at all. If a field coil driver sound different than the magnet/coil version then it's because other things are different too. The field coil drivers CAN sound better but depending on the driver, they can also sound worse, a field coil motor isn't always better, it's not even a quality indicator at all.
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