Eminence Flux Density Modulation

[loudthud]

OK Mr.Coil, lets see what you got.

FluxTone Speakers original 50 watt 12 inch VMT guitar speaker

On the detail page for the Model 1 there are two RTA plots comparing the Model 1 to a vintage P12R. What power level were the plots taken at? The P12R looks slightly higher in a few bands, what is the vertical sensitivity of the plots? Was the Model 1 at the max volume setting?

Does the voicecoil have any overhang? Can you put a sensitivity number (1W/1M) on the Model 1?

What happends if you try to push the sensitivity higher by increasing the magnetic flux? Can you make a Champ as loud as a Deluxe?

[Diablo]

Mr Coil:
I don't hear any tone changes with your design as the flux changes. However, with the Eminence speaker there is a tone change. Would you care to speculate why this might be so from the physics? My thought is that flux is flux, and it shouldn't matter how you create the flux. So I'm perplexed.

[Mr.coil]

Sheesh! isn't there some limit to the number of questions per customer?

1. 5 watts
   
   Pink noise was used...so 1 or 2 dB variances may have occurred between photo shots...We shot many takes for an average plot.
   
   vertical sensitivity= 10dB/division
   
   volume level = 5 watts (it does not matter what level the volume is set at...as long as there is no distortion present in the pink noise, and the test does not exceed the power rating of the speakers) ...we put in 1, 5, 10 or 40 watts ...It did not matter whether you were adjusting the amp or the VMT control...the curve of the graph stays the same...it just moves up and or down on the screen...until you have to change ranges. 60dB top to bottom on any setting. So we just settled on 5 watts so it was not so loud in the lab.
   
   Voice coil over hang is different for each voice, and split in the gap evenly. As the voice coils are provided by each manufacturer of that original speaker, we match our pole thickness with the original. Typical pole thickness= .312 (remember FluxTone is not creating a "new voice" rather we are preserving the tones of existing well known voices over a 25db range.
   
   Model 1 sensitivity is usually about 101.5 1watt/1meter
   model 1-A is about 99
   
   There are limits to the BL that can be generated VIA field coils (that's the main reason why the world gave up on them)...FluxTone has combated that limitation by closing the VC. gap from an industry standard of approx. .060 down closer to .040. If you cut the gap in half the BL goes up by a factor of 4! Do you remember the Altec 515-b? (105 1w/1m) gap=.035 and a big ass alnico mag. Now you got me rambling...
   
   As far a Champ verses Deluxe....well a Champ is about 3.5 watts Clean...and a Deluxe is about 9 watts clean. Approximately 4 Db difference.
   
   I built a one off demo amp for "KBCO studio C" It has a complete stock "Fender Twin" Pre-amp. We removed the 100 watt 4 6l6's output section and replaced it with a foot-switchable (you choose it) output stage. You can have a (Champ 1-6V6 3.5 watt), or a (Deluxe NNf 2-6v6 9 watt), or a (Super 2-6l6 40 watt). All of them playing into a 15 inch FluxTone driver with a foot pedal control for the Field coil. That way you can easily play the Champ louder than the other two.... It really demo's just how much a (VES) Variable Efficiency Speaker with a 25dB range can make a difference, and how the different output topologies sound....here are some photos.
   
   I am exhausted...I hope this answers what you were asking about.
   
   Thanks
   Mr.Coil

[Mr.coil]

I can only guess about their version... I have not taken one apart yet...But I think they are moving the pole pieces away from the VC. and they are losing control of the VC.

[Steve Conner]

Sheesh! isn't there some limit to the number of questions per customer?

You're kidding, right? There is no limit to the number of dumb questions asked on the Internet. You will soon get tired of answering them.

I built a one off demo amp for "KBCO studio C" It has a complete stock "Fender Twin" Pre-amp. We removed the 100 watt 4 6l6's output section and replaced it with a foot-switchable (you choose it) output stage.

Looks like a great amp! Thanks for the pics.

[J M Fahey]

Dear walkman.
Answering your questions on what I posted earlier:

My experience is that lower flux also rises Q and lowers attack, which they obliquely describe as "becoming mellow" It works as a sort of built-in pad.

Please could you or anyone else who has a detailed knowledge of speaker flux clarify in a technical way the answer to my question.

Are you saying, that at the same db level of sound, regardless of the distance to the speaker, that the sound made from a speaker of less flux, everything else within reason being the same, the speaker with less flux will of its own nature will produce a duller , or more mellow sound with less attack?

Yes, I can.
I'll stick to Physics here, don't want to get into "religious" discussions involving Mojo or whatever..
A speaker is a transducer. This means it receives some power in one form (in this case electrical power), and transforms it into some other form, in this case acoustic power.
That transformation is not 100% efficient; *very* far from it; to have an idea on how poor it is, we are talking on the order of 1% here.
Musical instrument speakers a little more, Hi Fi ones a little less.
Usually we strive for "high" efficiency (now you know "high" is an overstatement here) and if we want a quieter sound, we just lower the power fed to the speaker, that's what volume controls are for.
Problem is, tube guitar amps sound best for many types of Music when overdriven, meaning trying to put out *more* than their clean power rating.
This means *maximum* Music (noise?) sound level output.
Great onstage , *big*problem at home.
As I said before, lowering the volume pot "is not an option".
Acoustic power is "mechanical" power, in that we have to physically move some air back and forth reproducing the original musical signal.
More power means a louder signal.
Solutions:
1) use a lower powered amp (my favorite)
2) attenuate the power reaching the speaker
3) use a lower efficiency speaker
Let's analyze this 3rd option, which is the path Eminence and Mr Steve Carey/Fluxtone chose.
We'll have to explain first how a (regular electromagnetic) speaker works:
The speaker moves air, using a piston (the cone), which is driven by an electrical motor .
In that way it's not different from, say, an electric golf cart, carrying the passenger's weight (the useful payload) *and* it's own weight (waste) , powered by an electric motor.
In the speaker, say a 12" one, the useful load is around 2 or 3 grams of air (1/10 ounce), the waste load (cone, voice coil, adhesives, dustcap, etc.) is around 30 grams (one ounce), now you know why speakers are so inefficient.
The electric motor used is not a rotative one, as the zillions we have around, but a linear one.
It means that instead of rotating a coil it moves back and forth, moving the cone, but the principle is exactly the same.
And how much movement (in fact how much "pushing force") do we get for a given power?
We have a voice coil , inserted in a magnetic gap of a given strength (B), and a certain current (I) moving along that wire.
The (pushing) force will thus be higher if we increase "B" (better, stronger magnet) and/or "I" (higher power means higher current).
In this case, both Eminence and Fluxtone *lower* "B", the "magnetic intensity" if you wish, to achieve lower efficiency, thus less acoustic power (volume), because we "can't touch electric power" since the amplifier is overdriving and we want to keep i that way.
The magnetic force explanation:

Please notice that the three arrows are perpendiculat to each other:
Magnetic flux across the gap, perpendicular to the wire ; current along the wire; force perpendicular to magnetism and current, in this case "up".
Current running the opposite way will push "down".
Audio signal which is AC current will move voice coil (many turns of wire glued together) up and down (this speaker points skyward) moving the cone.
It's clear that acoustic level depends on amplifier power (which causes "I"), the length of wire in that gap , which we can call "L", and the magnetic flux "B".
If the voice coil is fixed (L), we can't touch power (I) , the only factor we can modify to alter volume is "B".
Eminence lowers B at the gap by a yet unknown "mechanical" system; Fluxtone by lowering current fed to the field coil (I guess).
"BL factor" is a very important parameter and is written in all serious speaker manufacturer's data sheets, it's one of the Thiele-Small parameters.
You'll find it on Eminence, Jensen, etc.sheets, but not on Celestion datasheets.

In fact they post a very tortuous and nonsensical "explanation" on why "technical specs have no importance" Mojo at its worst.
Some data as provided by a serious factory :

Now to why I say that lower B means duller sound?
I might answer that that's my experience (I have been making successful guitar speakers since around 1976 or so) or many other's but sticking to physics, now it's clear that by lowering "B" we are lowering "Force".
Since Mass is constant , in fact we are lowering *Acceleration* :
F=M*A so A=F/M
Having less acceleration means you have less "attack", less "punch".
*Maybe* the frequency response stays about the same, but it does not "sound" the same.
That is described by Eminence as "mellower".
Maybe Mr Carey/Fluxtone has invented some way to avoid this, I have no prejudice against that, I applaud innovation and technical advance.

[Diablo]

Thanks JM for the speaker physics. Something else to consider. The movement of the voicecoil in the gap creates an opposing current in the VC. Changing the B, will also change the magnitude of the opposing current in the VC. So wouldn't this change the loading of the output transformer and the output tubes and the tone?

[J M Fahey]

The movement of the voicecoil in the gap creates an opposing current in the VC. Changing the B, will also change the magnitude of the opposing current in the VC. So wouldn't this change the loading of the output transformer and the output tubes and the tone?

Yes, it does, it's called counter electro motive force .
It's the cause of two fenomenae:
1) thanks to that CEMF the voice coil passes less current than would be suggested by its DC resistance, appearing as a higher impedance . That's why a 6 ohm DCR coil means 8 ohm impedance, and so on.
A completely unmagnetized speaker's impedance equals the DCR.
That's my quirk with (any make) attenuation by B reduction: the speaker has less impedance than nominal, and *does not move* , dissipating safely much less power.
It has happened to me that an employee has fitted an unmagnetized speaker by error.
Since I make them on premises, they are often built but kept unmagnetized until really needed, that error may and has happened sometimes.
How do I find them out quickly?: the amp is tested, no sound comes out (or a *very* weak one), I think "shorted cable" or something like that, when I start smelling stinky overheated Epoxy or apple-like "perfume" (hot cyanoacrilate).
As a rule of thumb, a 50W speaker becomes a 20/30W one when unmagnetized.
Maybe Eminence or Fluxtone speakers still keep *some* movement to help cooling, my experience has been with fully unmagnetized ones (by error).
2) that CEMF, opposing movement, is a direct cause of damping.
As I said before, the speaker resonance becomes less damped, that's what I meant by "raising the "Q"; the speaker becomes boomier , looser and less defined.
Not bad, it's part of a Vintage tone.
Read speaker specs with new eyes, you'll see that the weaker magnet ones (Alnico or small ceramics) have Q around 1 (most guitar speakers, specially vintage ones) while high quality ones (JBL, EV, etc) have Q between 0.45 and 0.35
As to your last question: the small change in impedance will not have effect on the tubes loading; the tone *will* change (in my experience) but because of the speaker response itself, not because of what the tubes "see".
I repeat, Fluxtone may have found a way to keep sound constant with higher attenuation.
Eminence seems to apply raw uncompensated "B" attenuation, and everybody (including themselves) hears a tone change, a "mellower" one.
Everyday someone discovers or invents something.

[Chuck H]

FWIW I think the idea is brilliant. I actually thought about something along these lines about five or six years ago but let it go for lack of a proper lab or testing gear for speakers. So huge kudos for realizing it.

The way I see it attenuation systems will always have limits. Any argument against the FluxTone system that lower sound pressure levels detriment tone are moot because with ANY attenuation you MUST have lower sound pressure levels. Not speaking to JM's points above. The paramount goal of attenuation is to maintain as many parameters as possible. Until now the best attenuators were ACTIVE load speaker substitution and "power scaling". With the active load speaker substitution it's impossible to simulate the load of every speaker in every amp, so the tone and feel of the attenuated amp is different. With power scaling there are significant changes to the actual electronic operating conditions within the amp itself, so the tone is different. The FluxTone system has moved attenuation still one step further out in the chain and therefore eliminated those drawbacks and as far as I can consider about as far out in the chain as one can go. At some point the difference between the unattenuated signal and the attenuated signal becomes so small that you can't hear it and need test equipement to detect it. After that any contrary arguments become pedantic. I think this may be where FluxTone is and I'm excited to try it out. The only significant differences in tone with the FluxTone system would be that there is a minor change in actual speaker tone just because it's a slightly different speaker and there is less kickback voltage effecting the damping relationship between the OT and speaker. These are not exclusive to the FluxTone system. All attenuation systems suffer the lower kickback voltage and active load systems use a generic speaker model.

Without going into detail my attenuator (the one I made) uses an active load that is in parallel with a resistive panning control between the speaker and the load. My active load is designed to simulate a 4x12 cabinet loaded with G12M30's and was developed by Randall Aiken. My attenuator sounds nearly transpearent without any EQ adjustment switches until you get to about 16dB attenuation. The Fluxtone system takes it further and in my estimation from my own experience with my "lesser" system any differences caused by the FluxTone system are probably so small as to go unnoticed.

JM2C

P.S. JM, would changing the wattage at which a speaker is driven also change the "B" parameter? If so then all attenuators suffer this.

[J M Fahey]

Hi chuck.
No, the B value in the gap is fixed ; in these new attenuators it's "artificially" variable but by other means, it does not depend on audio input, it just can be set to one fixed value or another and left there at will..
Otherwise speakers would "round" signal as when it meets "clipping" diodes, and that does not happen.
In the applied Force equation, where you have B*L*I, any change in one of the factors changes the result.
If you halve B, you halve effective force , proportionately lowering sound volume, just like that..

[Mr.coil]

Dear JM,

Can you, or anyone, look at the schematic of a Vox AC-30 and hear that distinctive sound? Of course not. There is: What speaker it has, humidity in the air, age of the speakers, room acoustics, what pick up is pushing it, what nut case has the knobs set where....etc.

Your statements remind me of a child psychologist who has never raised any kids of their own. You sound like you have read a few books...but...books can be misleading and very very dry.

Actually test a FluxTone product...then prepare to rewrite your above statement, as you will be pleasantly surprised.

The back EMF you speak of is so much less of a factor than the actual product it can only be measured...not heard (more than -20db)... You are talking about minutia. That's like saying you can hear the drummers clothing ruffle over the sound of his drumming!

For instance if you have two identical speakers in front of you, with identical signals...but one is only 6 db down from the other....You will not be able to hear the lower speaker...try it.

We burned down every single on of our drivers and re-rated them accordingly. For instance the Vintage-30 is rated at 60 watts by Celestion...FluxTone rates them at 50 watts when used in a FluxTone setting.....so on and so forth.

Guitar speakers are not woofers, they cool more from radiation than pumping air ...lowest freq = 88Hz. Low E.

Some of the best sounding guitar amps have no damping at all...Tweed Deluxe, Ac-30...etc.

Thanks for your interest.

[Enzo]

Wasn't it Matchless, or someone else, used to take new speakers and before installing them, beat on the magnets with mallets to weaken them. A more vintage tone or something.

[J M Fahey]

Dear Steve/Fluxtone.
You'd be surprised !.
Anyway please do not turn this into a flame war, because I'm not trying to do that either.
I may answer each and every one of the new questions you have posted, but would rather not drop gasoline into the fire.
I'll only correct a slight misunderstanding you seem to have: *besides* reading many books, which I do not find dry but fascinating, specially my late 40's Olson and my 1954 Beranek, I have *also* being building speakers professionally for the last 35 years or so, *including* one type with Field Coil, a 30" woofer for which I could not find a magnet big enough in that moment (mid 80's).
I have sand cast frames, turned them out of sheet metal, have my own 40" lathe , wind my own coils, have my own three phase magnetizer, phosphatize/paint parts, etc.
A very *practical* approach if I may say so.
What scratches some the wrong way (it shouldn't) is that most in this beautiful industry were originally musicians which got into manufacturing, while I followed the exact same road but starting from the other end, I was an Engineer who loved Music. (specially Rock and Blues) and got into musical amplification manufacturing.
Don't worry, we all meet in the middle.
I wish you very good luck with your product; you doubtlessly deserve to collect your prize after all your efforts.
I make speakers commercially and know what a PITA it is.
As an extra note, I congratulate you on offering a new, USA made product, in this age of rice-fed low cost quasi-slave workers.

[Chuck H]

Sign me up for that job. I'm profoundly good at using hammers on things they aren't suppose to be used on. My thumb, dents around nails in trim work, etc.

Mr. coil, Don't take JM's post as criticism. One thing we often do here is break things down until there's nothing left. It's not a perfect world and we exploit that for entertainment purposes. In many places throughout his posts JM has offered praise for your innovation of previously unexplored ideas. He hasn't eluded that it's not as good as other attenuator systems. In fact I think he even says somewhere in there that it's likely better. He's just saying it's not perfect, and it's not, nothing is. It's very possible that any audible differences are so small that they don't matter for any reason other than this discussion.

This is mild. Your competition is going to want to tear you down and you'll need to stay cool. Gotta grow a thicker skin bro.

And welcome to the forum.

[Bruce / Mission Amps]

Hey Steve! Welcome to forum....
And for those that don't know Fluxtone Speakers, it's another very hip, up and coming company from Colorado!
Right down the street from me in Lafayette!

FluxTone Speakers reduce speaker volume without tone destruction