Smacks forehead... Variable magnetism in the speaker

[LeeMo]

http://www.fluxtone-speakers.com/Home_Page.html

It's just a little price-y compared to Dana's VVR.


LeeMo

[selloutrr]

well it's interesting but $850+ a power supply? that's getting close to the cost of buying another amp for a single champ speaker... You sure could buy a lot of cool gear and an iso cab for the cost of retrofitting a 4x12.

very cool idea though!

They just need to get production costs figured out in such a way they can cut the asking price in half or more and still make a profit... how you ask? simple buy in larger batches for a bigger price break. it's not easy getting started, so hopefully they either get noticed by a large deep pocketed company and bought out for a nice return on the time they invested or they have money to burn and can afford to sit on the product as it ships out. Then I think they would really be on to something but as it stands it's a cool post and idea but I'd rather buy some original Pre-rola's and rip the faces off the front 6 rows! it's alot of $$ just to make the sound guy happy.

[Andy Le Blanc]

ALL HAIL....... AND REJOICE....... THE FEILD COIL SPEAKER HATH RETURN.ITH

good idea.....too

WWII surplus magnets made it possible to be really loud now the need to play quietly has turned back the clock.....

[Tubetwang]

Thanks for posting LeeMo...

I can now get rid of my shag carpet...

[UR12]

This is an interesting concept. I do have to wonder though what happens to the voice coil as it still has current flowing through it no matter if you have the electro magnet energized or not. Most speakers use the air movement created by the cone moving to cool the voice coil. Without the cone moving, but high power still going to the voice coil I would think this thing would heat up the voice coil and sooner than later burn it up. Wonder how they are getting around all of that?

I know where I can get my hands on a brand new field coil speaker and the VVR can be used to control the power going to the electro magnet so maybe I can do a little experimentation.

[Andy Le Blanc]

now theres an idea...... vvr ...... one knob to scale pre, power, and speaker
field intensity......

I have concerns about voice coil cooling too..... but theres most likely an optimum
where its not really a consern ....there are many choices Im sure involved
with voice coil design that can eleviate that as an issue too...

[LeeMo]

I've got a question. Since I haven't been around field coil speakers, though I know the basic concept, do they use AC or DC to create the magnet?
AC wouldn't generate as much heat , but DC wouldn't inject any hum. I suppose you could arrange some sort of "Bucking" coil in the design.

LeeMo

Edit : Well DUHHHH! It has to be DC doesnt it?

[UR12]

All of the old field coil speakers I have dealt with used the field coil as a choke for the HV power supply. They are all operated on DC and can induce hum if it isn't filtered too good.

[Wayne]

I had given this some thought years ago, before I had the technical background to work out all the details - in my scheme, the field coil was driven by FW rectified signal. Looking back on it now if the field coil was an 8 ohm load and the voice coil the same you'd have either a 4 or 16 ohm load to present to the amp, and no power supply to contend with.

Just a thought...

W

[UR12]

I had given this some thought years ago, before I had the technical background to work out all the details - in my scheme, the field coil was driven by FW rectified signal. Looking back on it now if the field coil was an 8 ohm load and the voice coil the same you'd have either a 4 or 16 ohm load to present to the amp, and no power supply to contend with.

Just a thought...

W

Don't quote me on this but IIRC the old field coils were actually 100-1000 ohms DC. I don't have a clue how many Henries they were but we always had to replace them with like a 750 ohm resistor to install a permanant magnet speaker in their place.

I am not sure I understand what you mean by no power supply.

[Wayne]

When I first thought of this, I had never heard of a speaker with a field coil, so my idea had nothing to do with the specs of an actual unit. What I had thought of, years ago, was how to make speakers louder. Now that I'm a bit more educated, I realize that all I would have done had I tried it would have been to rip the cone due to over-extension.

What I salvaged from this old, ill-informed idea of mine is that if signal is driving the voice coil, and signal (rectified) is driving the field, the <theoretical> speaker would have no need for a DC supply to drive the field like the speakers mentioned above would.

You'll have to forgive me, guys - sometimes I think out loud before I've thought things the whole way through

W

[txbluesboy]

Very clever--Why didn't I think of that!

[Wayne]

Very clever--Why didn't I think of that!

Race ya to the patent office

W

[FUCHSAUDIO]

I met these guys at the NY Amp show. They brought a demo speaker into our room and we played the hell out of it with most any amp, and it does what it's advertised to do. Cool idea, that (apparently), not everyone got...When I said "oh, it's a variable magnetic field...cool", the guys laughed and said "at-last, someone who understands !!".

They apparently spent lots of cash developing the system, and it was quite pricey at the time, due to small volume. While it's clever, you are locked into their speakers, good bad or ugly. From the looks of the pictures, he may be using those Peavey speaker baskets, which allowed you to replace the voice coil and cone, and reuse the magnets. Not a bad way to cut his costs, assuming it sounds good.

Still a clever idea though....I think he said he had applied for a patent on it, if I'm not mistaken. How successful it will turn out, is anyone's guess.

[Ears]

If the magnetic field is variable, wouldn't the physical damping of the cone become more of an issue?
If optimally set up for good damping in a full strength field wouldn't the speaker cone become overdamped when the speaker is run at lower field strength? Or if set up for lower strength field the cone would be underdamped when the field is increased.