Field coil woofers

Ever wonder what a field coil woofer is? Paul explains.

[xaviermontalban]

I speak for myself when I say I'd like to see more of the company. I also would like to see more of your products. I have a feeling a lot more viewers feel the same way.

[AllboroLCD]

Your onto something Paul!!! Excellent idea, a small, medium, and large room for recording. Give you the whole spectrum of natural reverb.

[connorduke]

Warehouse optimisation is a speciality and a valid field of expertise.

[guilhermedealmeida]

In the past, until 1950, in the old time of tube radios and tube amps, there was the gold time of speaker field coils. There was no strong enough permanent magnets available.
In these times, the field coil played two different roles: 1- produced the magnetic field for the speaker; 2 - worked as a low pass filter for the power supply for the tubes, as an inductor, reducing hum and voltage fluctuations. Usualy these second function was named "chocke". After the tube/valve (or sellenium) rectifier, there was a "pi" filter consisting of a capacitor across + and -, the "chocke" in series and a second capacitor between + and - again, figuring the shape of the "pi" greek letter.
Regards.

[Fluterra]

Field coil magnets are 100% better than permanent. No question, full stop. The only reason they are not more common today is because of COST. Companies like PS Audio makes things to a cost, and they (and others) will cut costs when and where possible. When you add an ‘amplifier’ for the field coil, and the cost of winding the copper, it’s considerably more expensive. But don’t kid yourself: the FC drivers are fantastic and so much better (less distortion, more effortless, tunable).

[kellywilson]

Hey Paul, I thought it was a terrific explanation. Cheers....

[razisn]

Explanation in just a few words. Instead of a permanent magnet, field coil drivers use electromagnets. Electromagnets were used in very early speaker drivers before adequate permanent magnets were available. It beats me why Paul seems never to be able to provide a succinct description of something.

[Oystein]

I could easily drive a forklift in that space👀 Looks like twice the size I was used to at some job. There are small forklifts exactly for this purpose

[a.o.]

From the looks of that empty warehouse, your Black Friday blowout was a success. 🙂

[Fluterra]

Field coils do not create a lot of heat. depending on the design, you’re talking about ~30C. The voice coil gets hotter.

[InsideOfMyOwnMind]

I think a stator coil operating in concert with a PM could present opportunities such as negating the downsides of NFB, using NFB differently to counter suspension borne compression as well as cabinet modes. The math would probably be above my pay grade.

[bikdav]

That’s interesting. I was told that electromagnetic speakers were common in the very early days of radio.

[markanderson]

Years ago, electrolytic capacitors were huge and the coil helped filter the power. We never had more than a few watts of audio power so heating never occurred.

[ThinkingBetter]

Amplifiers have negative feedback circuits to achieve linearity and lower distortion down to a tiny fraction of a percent. A speaker is on the other hand highly un-linear due to how the electromagnetic field operates and how the spider and surround behaves at different positions causing vastly more distortion than the electronics. In addition you have cone breakup, intermodulation distortion, thermal dependency etc. For these and other reasons, we can all agree that the choice of a speaker is the most important decision for creating a good system. But when will someone innovate a super precise cone position feedback component that can be used to make an audiophile servo speaker (not just subwoofer)? For example, the head of a hard disk can read 2 million bits over an inch. It's gotta be possible today to enable some super tight precise cone control at also higher frequencies, but it's like there is zero innovation in speaker drivers for many years already. I often find myself discovering details using my HiFiMan Susvara planar or Stax electrostatic headphones that seem to lack with dynamic headphones or a stereo speaker setup and my theory is that it has to do with the limits of dynamic drivers.

[davidhosmer]

You need a bunch of money and a side load RAYMOND fork lift. Extendable forks, side shift . I worked at a Lowes (worst 2 years). They had all overstock on ceiling high racks. Everything you needed all the time was UP THERE. Couldn't read stock # from the ground - had to climb rolling ladders a 100 times a day and try and carry heavy fans and fixtures down with one hand. OH - you have more than half a brain and care about your employees and inventory. Love the daily visits and stories. Take care

[rickhigginson]

Well...Yes, and no! When I was in the Navy, many years ago, at the then West Coast Service Electronics School, on Treasure Island, San Francisco, I met Bob Andrews, who had a small record shop, with a large area in the back, to assemble: extension speakers for juke boxes, beginning during World War Two! And Bob told me that his speakers did not use magnets. OR a transformer with AC Power. Instead, there was an additional box, with a transformer, for the correct volage, and, a rectifier, I believe, to convert the AC Power, to: DC! And, isn't his what a magnet is? An electromagnetic, electrostatic field, in one direction, potential, which never changes? And: this will not heat up, as there is less current flow, as, once again, no AC field is being produced, only the constant DC potential! Worked well! 😀😁

[tothemax]

SW1X Audio Design are literally in this field, with nice tube rectified PS's. I think will be stunning to listen to as well.

[logtothebase]

James Clark Maxwell has a lot to answer for.

[spentron]

Could use power to refrigerate the permanent magnets instead. ;)

[AN-hzfo]

Do different types of magnets (if & when with exactly the same power and geometry - magnetic circuit included) make a speaker sound different ? same for its basket material such as aluminum vs steel vs …) ?
I ask this as some audiophiles do say that old speakers with alnico magnet and stamped steel basket sounded better than the same model when equipped with ferrite magnet and aluminum basket