Fluxtone Variable Efficiency Speakers

Anyone seen / tried something like this?

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

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

Apparently the speakers use an electromagnetic field in lieu of a Magnet which allows the strength of the magnet to be adjusted which, in turn, alters the efficiency of the speaker. Rather than bleeding off some power from the amp, just turn down the volume on the speaker! Of course, they cost as much as a high end attenuator + a speaker so they'd better work.

Thoughts.

Personally, I question the applicability with amps like Mesas that rely on preamp distortion for tone but the idea seems really cool nonetheless.

There's no question in my mind that it is an approach that should work. I think in Grade 2 science we learned that a magnet could be replaced with a coil of wires with current running through it, also known as an electromagnet. The price adder is a little steep.

Eminence has the more practical and economic approach which accomplishes the same thing. It has a threaded fitting that you turn to change the position of the voice coil inside the permanent magnet, thus changing the amount of field acting on the voice coil. I bought an eminence reignmaker for $140 new, and have been completely satified with it in both tone and attenuation from full to zero attenuation. (about 9 db).

They call their technology Flux Density Modulation, or FDM. They market the speaker in a way that seems a little gimmicky, but accomplishes the same goal at must less cost.

As for applicability...some of mesa's amps have clean circuits that are either fender or marshall in basic structure, and you really haven't experienced your mesa unless you've put 6v6's EL34's in it and run it up into that sweet zone of power tube compression and crunch. A number of lead voicings also resemble marshall style gain circuits that just get better the more power tube action is going on (especially on gain settings about 10-11 oclock). But, yes, there are other voicings that are essentially preamp in nature and sound best with 100W of high clean headroom 6L6 action.

9db attenuation is something but the 25db these guys at fluxtone are advertizing is insane. I think the extreme prices are because the speakers are all built individually instead of mass produced. I, for one, REALLY wish this technology would become more widely available. I think there is an ample use / market for it. $750 to replace ONE v30 is just too much money. It would be hard to justify $1,500 to put two v30s in a 2 x 12 Rectocab.

I agree about the power tube breakup. Metal and most modern tones are best accomplished by the preamp. A clean power section keeps things tight and defined. But, to make a Recto do rock or lower gain stuff, you kind of NEED to get the poweramp involved. I tried Yellow Jackets in my Recto and I found they worked best with the gain at around 9:00 or lower and the master turned up a fair amount. Getting power tube distortion on a 100watt head simply is not feasible without at least 9db attenuation if not more. The -25 would be a dream for practicing!!

At a simple level, an electromagnet approach is similar to a permanent magnet. However, the electromagnet will likely have very different flux vs. frequency and vs. power than the permanent magnet. In addition, the characteristics will change with the flux control. Same issues for the moving-magnet approach. As you move the magnet to reduce the total flux, the fringing fields at the edges of the magnet will have some effect on the flux (and therefore tone).

This is all theoretical - what matters is if you like the sound or not.

I'm really skeptical about these speakers. It reaks of marketing to me.

There is a mention about heat being generated in resistors of regular attenuators. If their device is not generating heat, then where is the power going ?

How good are their speakers ? If they don't have the tone to start with there is probably not much you can do about it. I'm sure the product works, but is it better than the rest ?

The Webber MASS has alwayed interested me and would be worth checking out. It is around 1/3 the price of the fluxtone setup.

https://taweber.powweb.com/weber/mass150.htm

Great points J.J. I definitely thought about how good the speaker tone was to begin with, as well as how the tone would be altered as the magnetic field is changed. As I understand it, the FDM technology Eminence uses cause the frequency response to change with the speaker. It goes from sounding very bright and modern (High efficiency) to sounding warmer and rounded (low efficiency). I would imagine these Fluxtone speakers to exhibit a similar behaviour when exposed to volume. As for the speakers themselves, it is difficult to know how good they sound because there are not any decent sound clips available.

In regards to volume 'attenuation', you have to consider the science behind a variable efficiency speaker. An attenuator uses a bank of graded resistors to create a load to absorb power which results in heat. The remaining droplets of power are sent to the speaker which then produces volume.
In the case of a variable efficiency speaker, the speaker can become less efficient so more power is needed to move the voice coil and thereby the speaker cone. The TUBES on the amp will get hot if the amp is running wide open, the same way it would if you cranked it with efficient speakers. There isn't an increased LOAD operating on the speaker; it is simply becoming less efficient because the magnetic field is weaker. Under a weaker magnetic field the change in current from the speaker lead is simply moving the voice coil and therefore the cone less far. So less electrical energy is being TRANSFORMED into physical energy. It is that simple. The miracle of this design is that no power is being 'absorbed'.

In plain English, tone is not sucked by an electrical device disrupting the flow of electrons from the Tube amp to the speaker and back again. Rather, the energy being created by the amp is being used less efficiently by the speaker which results in less sound being produced. As for resistance, an 8ohm speaker is an 8 ohm speaker and a 16 ohm speaker is a 16 ohm speaker. As I understand it, that much does not change.

When you think about it, it makes a lot of sense. Basically, you know that a 95db / watt / metre Jensen will not be as loud as a 100db / watt / metre Celestion. It does not mean that the Jensen is somehow attenuating the electrical signal, because it is not. The reduction in loudness happens after the electrical signal. It does not disrupt the electricity coming from the amp and going to the speaker in any way.

YJ, that's not quite right. If the amp is producing constant power (assuming speaker impedance stays constant), as the speaker becomes less efficient, less power goes to moving air, and turns to heat in the coil and stray flux instead.

If the speaker impedance changes, then more or less power will be created by the amp, so the power tube operating point will change, and they will run cooler or hotter.

Having no decent demos was one of the things that set my BS radar off.

Our guitar amp speakers are at best around 5% efficient. This means that if your amp delivers 100 watts, 5 watts will be transfered into accoustic energy and the other 95 are more or less used up heating the voice coil, magnet and other losses.

What I expect is happening is that the voice coil in the Fluxtone (and Eminence speaker) is dissipating the power just like a normal speaker. Reducing the magnetic field effectively couples less energy into cone movement. The voice coil should be burning up 95% or more power as usual, but backing off the field will also decouple the voice coil and cone from the amp which is a lot like what a resistive attenuator does. They may have some tricks to stop that from happening, but it all looks flawed to me.

Iso cabs anyone ?

Check out the eminence site, and send the technical service rep an email (his email is listed on the site). He sent me a Frequency vs. Impedance chart for the FDM speaker operating at no and full attenuation.

That will get you some good technical info to gaze at.

I bought the Reignmaker...only paid $140 (L&M) and I'm loving my Heartbreaker amp with a single pair of EL34's and that speaker. It's a deadly combination that is outperforming some high end gear that some of my pals have. I am getting just the right amount of power tube breakup in my living room at volumes that are loud, but not so loud that they kill small animals and children. I'm thinking 90 to 110 db in an 15'x20' room depending on where you stand.