Eminence Flux Density Modulation

[J M Fahey]

J M..a favor please?

Could you recommend someone here on this site, state side, that would be interested in trying out one of our pieces?... Maybe someone that should know tone-vs-spl, but is still a bit of a skeptic?

I may have already talked to them...but I cant seem to navigate this site with any reliability...and I do not want to hand out to just anyone.

Thanks
MC

Well, thanks for trusting me so much, but I fear it's a tall order for me.
After all, I'm practically a beginner here, with real activity since only about one year ago.
And I'm here to learn much more than for any other motive.
And I have learnt a lot !!!!!
I suggest you take it easy, you are really not *forced* to prove anything here, we're just a bunch of friends with similar interests talking around a virtual coffe table or something equivalent, each one with his own , well earned opinion, and tons of hard fact or experience to back it.
And this is some privileged coffe table !!!
Some will agree, some won't, that's life.
I suggest you read around; whenever you find somebody whose opinion might be useful , give it a try.
Good luck with your product.
PS: as far as patents in general , I have mixed feelings, too short the space here to talk about them,anyway try to get it if at all possible, it doesn't hurt to have one.
JMF

[Mr.coil]

Dear Mr. Wizard...( BTW...I loved that show)

What I meant to convey is that "Guitar speakers" are basically a mid-range driver.
That is to say they are not tweeters, nor are they woofers.

Tweeters require no specific cabinet size. And the woofer is the driver that defines the cabinet dimensions. While the mid-range usually has some isolation from the woofer's space, it still needs little space to function properly, in a three way setting.

A "combo guitar amplifier cabinet" is more about venting the heat, providing a space for the chassis, and facing the driver forward, than a "specific tuned cavity" .

The lower board on an open back cab is about keeping the cargo from falling out, and some cross bracing. The upper board is usually about channeling the air for cooling via gravity.

In a non-combo cab, venting is not usually required, so they tend to be closed back.

This is what I propose...

• If we were to have a 12'X12'X12' sound proof room...
• cut an air tight hole in one wall for a open back guitar cab to snugly fit into that hole

• it will not matter whether you remove the top and bottom boards (from the open back cab) before you place the cab it in the hole or not. In both cases you can't hear what is coming out of the back of the cab. And I put forward that it will have Very little to no perceivable effect on what is heard coming from the front. Ergo no matter what size the opening is on the back of an "open-back" cab (some will call that a ported enclosure)..if you kill the sound coming from that hole...whatever size it is...It will have little to no effect on the "Normal Guitar frequencies" coming of the cone in the front of that cab.
  
  Remember we are not talking about a bass guitar.

As far as whether FluxTone Speakers sound "good"... well, FluxTone does not weight in on that issue...We simply are providing as many different voices that we can, that have already been described as "Good".

And finally...remember you are getting three things when you buy our product...
A $250.00 speaker,
A $250.00 speaker that is typically 2-3 db louder than its original, at the same power...(we run a smaller gap)
A $250.00 variable attenuator... (25dB) that does not get hot, does not require clumsy wiring, and can be adjusted by your amp... or 200 feet away at the other end of the snake (Via remote control), All this while not changing your tone.

So now, you see, what you are actually getting is a three fold upgrade, not just another speaker.

Now Guitar players will never have to say..."Well if I turn it down my tone will go away" Wait a moment...I may have just realized something.....Hmmm...Maybe they like being able to say that..... Ya, that's it, They just want to be loud!...


Because I don't get any "nay saying" from recording studio execs, front of house mixers, bar owners, patrons with sore ears, neighbors, wife's, band-mates......Just the guys "out of the line of fire" of the amps!


Well I have kicked the bees nest this time.....he-he.

By the way...whoever can convince me that they would do a fair test of our product...and post the results here on this forum....I will send you one to test... (30 days)....I HAVE NOTHING TO HIDE!

MC

[Diablo]

I've been thinking about the Eminence style of Flux modulation using a permanent magnet speaker. I don't know if this is how Eminence does it, but I've figured out a way that should work for the "do it yourself" kind of guys. Let's say you have a speaker with a 1.5 inch diameter iron center pole. Bore a cylinder hole in the rear end of the center pole about 1.25 inch in diameter and maybe 2 inches deep. Make an iron piston with a 1.25 inch diameter and 2 inches long. to fit the bored hole. Drill and tap the center of the iron piston for a threaded steel screw (e.g. 8-32 allen bolt). The screw will stick out both ends of the piston. The tricky part will be to machine a keyway in the center pole so that the piston can slide in and out, but cannot turn in the bore. Turning the screw in will create an airgap between the piston and the center pole and increase the reluctance in the magnetic circuit, which will decrease the flux seen by the voice coil. The unit might need a spring and keeper on the piston to keep it from popping out or moving due to vibration.

[Mr.coil]

Well I have some on order...I will let you know.

MC

[Diablo]

Excellent....all in the name of science and magnetism.

[J M Fahey]

Hi Diablo.
The basic idea might be something like that, yes.
That hypothetical hole would not be 2 inches long, because that center pole would be around 1 inch long itself (magnet thickness+ top and bottom plates thickness), but yes, going from a full solid cylinder to a skinny walled tube would definitely work as an attenuator.
How many dB ? Don't know, but it should be noticeable.
I think you *should* apply for a patent, because we don't know how Eminence does it, might make it some other way.
As for dating it, your post above *is* a "certain date" in legalese.
Worst can happen is having it not granted.
Think about it.
EDIT:
Does anybody have a link to Eminence's patent?
Just curious.

[wizard333]

By the way...whoever can convince me that they would do a fair test of our product...and post the results here on this forum....I will send you one to test... (30 days)....I HAVE NOTHING TO HIDE!

How do you define a fair test?

[Mr.coil]

FluxTone speaker placed in closed box ( 1-2 sq.ft.)
Spectrum analysis of flat pink noise (5 watts input), Hifi. amp. set at flat.
Measure with a calibrated microphone placed 2-3 feet in front of the driver.

(DO NOT MOVE MICROPHONE OR ADJUST SIGNAL DURING TEST)

Drop 2 dB at a time with FluxTone power supply control...record graph results...
overlay the results and compare.

would that be ok?

MC

[Diablo]

Thanks JM for verifying the design is feasible. I think I'll wait to hear from Mr. Coil to see if Eminence does it the same way before I consider applying for a patent.

[hasserl]

Just an FYI, I did check out the Fluxtone speakers at the LA Amp show, I think it was in 09. While I didn't get to play the amps, I listened quite a bit to several other people playing/testing the speakers, and I was very impressed with the tone. The re seemed to be no change in tone from full volume to full attenuation. In one case a guy sat playing a Les Paul into a dimed Twin Reverb, the tone was fantastic, but low enough you could talk over it. The power supply to the speakers did seem like a bit of a pain, but a foot operated control seemed to work very well.

[J M Fahey]

FluxTone speaker placed in closed box ( 1-2 sq.ft.)
Spectrum analysis of flat pink noise (5 watts input), Hifi. amp. set at flat.
Measure with a calibrated microphone placed 2-3 feet in front of the driver.

(DO NOT MOVE MICROPHONE OR ADJUST SIGNAL DURING TEST)

Drop 2 dB at a time with FluxTone power supply control...record graph results...
overlay the results and compare.

That sounds like a very reasonable and trusty test.
Only two very minor details, which do not affect the basic soundness of the experiment, but would move it even closer to "real world use"
1) personal opinion, you may disagree, the box should be *at least* 2 cu. ft. ; a 1 cu. ft. closed box would be too small and will raise resonant frequency too much.
2) I don't imagine many 5W amp owners needing desperately a Fluxtone; maybe starting with 15 to 40W would be somewhat more representative of a typical user.
Beyond that, the experiment not only looks serious, but, very important, is easy to reproduce.
Good luck.
PS: looking forward to your posting its results.

[Mr.coil]

JM,

15 to 40 watts is too loud for the shop...I mean we used to test that high but soon found it was pointless...Its the same pattern at 5 so unless we are burning one up for power failure point...we just run them at lower power.

We usually use a 1.5 cf box...we found "any box" only effects freqs. below 150hZ. I can tell what a speaker is going to do in that box below 150...because its always mostly the box at that point, mixed in with room acoustics, and other reflective surfaces.

We are mostly concerned with the 150 to 5k span anyhow, when we are looking for anomalies.

We are so used to the results now after 100's of tests we can just run a raw speaker on a carpeted bench and see what we want. With the mic. hanging from the ceiling over the cone.

This may sound weird for you but, we have done this so many times that...we do not even have to "glue in" a re-cone kit to test it...We can just set it in the throat, balanced on the spider, .5 watt, and see if it meets spec! After the glue is set...push 10 watts or more...its the same graph-line, just higher up on the screen.

We have been at this for almost 5 years now...I know FluxTone performs as stated when it comes to preserving those delicate overtones, while reducing the SPL.

What gets me and is hard to explain/comprehend... is where and how those overtones are created. I have been just buried by some profs. when they start in on back emf, and inductive ringing, and core saturation, Plate impedance, high fructose transformer iron, and the like....BLAH,BLAH,BLAH...!

But I can see when you pull the drive or B+ to the finals...oops the overtones just start to dive...or if you put a resistor between the Trany and the voice coil....splish splash ..PooF..there gone! Where did they go?

Creating them...That's the real magic. I can tell you NNFB is huge in this department... Tweed Deluxe's/AC-30's..holy cow! ...thick and heavy.

MC

[kg]

has anyone monitored the longevity of the power tubes using either product?

you don't get something for nothing. when you turn up the attenuation, the power is still going SOMEWHERE. the output stage is still working hard, drawing similar plate input power. the speaker cone is just no longer moving as much. where is that power now being dissipated?

what does the impedance curve of a magnetless speaker coil look like? i suspect it looks like the HF end of a normal plot (in which the impedance rise is due to coil inductance) but lacks the resonant peak (due to cone movement).

how does that impedance curve differ from a traditional load? it will definitely be lower in the LF region due to the lack of resonant peak.

what effect does that have on the load line of the output stage? it will be lower in that same frequency band. the tubes will likely have no issue with the lower load Z.

run either method of knocking down speaker motor strength (they're functionally equivalent), drive it with a medium power tube amp (say 30-50w)--what parts get hotter? i'm sure the speaker coils get hotter, especially since cone movement tends to vent the coil and pole pieces by pumping air in and out.

as coils get hot, their DCR goes up. does that increase in DCR cause any secondary effects? what is the reflected primary impedance after an hour of use? has it risen enough to put additional stress on the output tube screens, for example? hence my question about power tube lifespan...

[J M Fahey]

Hi kg. Interesting questions.
As far as tube longevity, the tubes are being driven full power, they don't know whether they drive a real speaker, a power resistor or a very weak magnet speaker, I guess they get "spent up" the same with any method, that's the price you pay for full power sound after all.
The impedance curve of a fully unmagnetized speaker must be its DC resistance plus whatever loss/parasitic inductance the voice coil has.
That's easy for me to check.
I actually have 3 x 12" speaker frames sitting on my workbench, which will become full speakers sometime in the evening, but unfortunately I already magnetized them on Saturday, I was finishing cabinets in a hurry and magnetized all at once, even the unfinished ones, to save some time.
Maybe tomorrow I'll mount some fresh magnetic circuits, after all I have parts lying around for close to 150/200speakers , so I'll build a couple of them, and run an impedance curve, before and after magnetizing.
That will settle it.
Unfortunately I can't magnetize to different B values, it's full or nothing.
A friend of mine, who makes *impressive* Hi Fi speakers, has a special magnetizer where he can rise or lower the center pole , he usually does not fully magnetize but to around 80/90% as necessary , so *all* his speakers have an exact "Q" of 1 ; all his speakers sound the same, no 20% production spread there.
I might visit him with a couple speakers and measure and trace curves at different B values.
In fact my calibrated AKG C451 and Jensen Transformers preamp live there, close to his HP tracing equipment; at home I have a simpler setup .
Note: a magnetless speaker will be flat; a weak magnet one will not; the HF part will always be about the same but the resonant peak and the "Q" will not.
The voice coil will get hotter, you are right that motion cools it; in fact I already commented here that one employee of mine, probably inmersed in a Jamaican dream or floatin in a sea of beer, has on occasion mounted an unmagnetized speaker mixed with regular ones, the lower SPL was not that much noticeable (logarithmic ear response, etc.) but the cooking epoxy smell gave it away.
I'll make that experiment too, drive two speakers with 20/24V RMS pink noise, one of them unmagnetized.
Don't think the screens will be affected, because there are two "errors" which tend to compensate each other: impedance will be lower, because the reactive component will be lower, given a weaker cone movement (the object of this attenuation); yet as you say, the voice coil might get somewhat hotter, raising the DCR; both effects act in opposite ways and will somewhat cancel or thereabouts.
Tube plates and screens should not be much affected.
I leave that test to you or whoever wants to do it.
Good luck.

[Mr.coil]

JM here is a chart showing what you want to know... these are 2 dB steps of attenuation.

I had prepared an answer to his question...but lost it in editing...you did a more Graceful job than I was going to do anyhow....

You can call me Dilbert if you wish...

MC