Eminence Flux Density Modulation

[kg]

people curious about reducing the B of their speaker magnet motors could achieve a similar effect by bucking the existing magnet with a salvaged magnet from a blown speaker.

you might have to have someone hold it for you while you play though. either that, or a roll of duct tape and/or some spacers!

It always cracks me up when I see someone trying to make a point about a "ported speaker cabinet" for guitar application. Unless you have a Baritone guitar, a normal guitars lowest freq is about 88 Hz...Way above where any port will have an effect.

be careful about assumptions made regarding frequency content... as we do not have an monophonic instrument.

beat tones can and will be produced whenever multiple frequencies are summed together, and they will be greatly increased in relative amplitude if that summation is highly nonlinear/distorted (as is often the case with MI amps).

i'd be happy to take a sound sample of quite low frequency content using nothing but my guitar, my amp, and my cabinet(s).

[Mr.coil]

Point well taken about the summations...But, I still say porting a guitar cab has a minimal overall effect...

I would like to witness a double blind test of any perceivable differences.

Maybe: on one particular cabinet, with one particular chord, with one particular setting of knobs, on one particular amp style...in that particular room.....Etc.

Really I would like to hear it..


MC

[walkman]

Wow , this is now a really interesting thread! Lots of it way beyond my experience yet still great to learn from.

So despite 'less acceleration' at attenuated levels (obvious / to be expected ) I guess the would sound have a similar punch at the same db level to the listener.

What I have experienced is that when i have the fluxtone at the highest level of attenuation with an amp that is between 2-4 watts , that the tone that is 'the same' (to my ears ) .... it does in my perception feel that it has a bit less 'punch'.

However, to hear the same volume of sound compared to when the fluxtone is at 5-7 on its dial, standing back a 2-4 of meters from the amp , I have to either have my head right up next to the grill cloth or be lying down on my back next to the amp playing the guitar ( i'm no clapton but didn't he spend some of the 70's doing drunk on stage lying on his back ( mojo?) ).

The instantaneous acceleration of air from a unattenuated speaker vs an an attenuated speaker may be less however most of us who want any hearing after a few seconds will not want to hear that acceleration and hence stand back from the speaker somewhat , regardless of the wattage of the amp driving it (or within reason the level of attenuation.)

So if I had a reliable way to interpret level of sound I was actually hearing in to db , I could then listen with the fluxtone set at no attenuation, vs with full attenuation then i could tell you if it lacked punch , but i suspect the best way to test would be to be playing outside on a still day , and progressively move futher from the amp untill either the 'punch' felt the same, or the level felt the same , as when I m playing right up close to speaker with full attenuation.

As an aside ...
The slowing of ultrasonic sound through air is what allows another great speaker invention, the audio spotlight to work.
See Audio Spotlight - Add sound and preserve the quiet. and Sound from ultrasound - Wikipedia, the free encyclopedia

I have actually contacted holosonics to ask if they would be suitable for musical instrument / PA applications , however apparently they will not reproduce frequencies lower than several hundred Hz , and are more suited to voice / background sound applications.

I guess I was imaging the different possibilities of moving sounds and the overlapping of different sound sources at different locations.

Anyway thanks Steve / Mr Coil for chatting with us ... its great to have your input , and really think that the special amp you made would take off too.

With Fluxtone speakers I can play my 5e3 clone on full tilt at home! And they do sound great too

[Mr.coil]

Well that's interesting...some pretty high profile players that have it, and a few studio execs, Have said almost the same thing: (And they have used $7,000.00 microphones to take the human ear, and emotion out of the test).

"Every time you turn it down a notch...its like you are getting farther away from the speaker, no loss of overtones, no change in spectrum...It just quieter (like you are walking across the room)...same touch...same response...just not as loud".

Bravo for you Walkman..you are in the same crowd that has earned many, many, gold and platinum records!

I can't mention there names...so do not ask. But you would know all of them.

Thanks,
MC

[kg]

Point well taken about the summations...But, I still say porting a guitar cab has a minimal overall effect...

well, does an open backed cab sound different than a sealed cab?

if the answer is yes then porting has a pretty observable effect.

[Diablo]

well, does an open backed cab sound different than a sealed cab?

if the answer is yes then porting has a pretty observable effect.

A closed back cabinet isn't the same as a ported cabinet. A closed back cab with a good air-tight seal damps the speaker cone movement. Open back cabs (and ported cabs) allow freer cone movement. Any damping of the cone has to come from the stiffness of the speaker surround and spider, and perhaps some from magnetic interaction of the voice coil and magnet gap.

[Steve Conner]

http://scopeboy.com/speaker/evm12L_cab_design.jpg

[Mr.coil]

An open back cab sounds different because you can hear the "out of phase" signals bouncing off the walls in the room...and then finally getting back to your ear at different times than the primary. You can have a much greater effect on your sound by varying the distance to a wall, (of an open back cab) and/or its angle to that wall, than a ported cab. (think chorus-like effect)

YOU CAN NOT PORT AN OPEN BACK CAB.

In the hifi world open back cabs are not tolerated, that's why all of the out of phase signals are killed with "sound deadening material" before they can be heard by the listener. Of course you can manipulate the "Below 60 Hz waves", by forcing them to go through tunnels, and be delayed in time just enough to hit your ear drum in phase with the primary. This is a band-aid for "woofing-systems" that can not produce enough oomph at certain lower frequencies. However this activity impairs other frequencies above and below those that it helps. So it is a fine line between "gimmick" (think Bose), and value ( think Pro-sound).

Bass guitar cabs can use them to some degree, But with guitar frequencies, they are usually so high that "the tunnels" would be so short that they are only theoretical.

There are ares on an opperating speaker cone that are actually out of phase with other areas on the same cone at the same time. This is one of main factors that determine how and why guitar speakers sound different than others: alternate paper thicknesses, different paper pulp fiber length, suspension stiffness, weight of the copper in the voice coil....ETC....These variables make a huge change in tone compared to porting or not.

MC

[kg]

A closed back cabinet isn't the same as a ported cabinet. A closed back cab with a good air-tight seal damps the speaker cone movement. Open back cabs (and ported cabs) allow freer cone movement. Any damping of the cone has to come from the stiffness of the speaker surround and spider, and perhaps some from magnetic interaction of the voice coil and magnet gap.

ummm..

an open backed cabinet IS a vented box.

trust me on this one.

is it tuned to a useful frequency? no. but it IS VENTED (the vent cross sectional area and depth CAN be measured), and it behaves exactly like a vented box wrt TS parameters, acoustical response, and driver dynamics.

An open back cab sounds different because you can hear the "out of phase" signals bouncing off the walls in the room...and then finally getting back to your ear at different times than the primary. You can have a much greater effect on your sound by varying the distance to a wall, (of an open back cab) and/or its angle to that wall, than a ported cab. (think chorus-like effect)

what do you think comes out of the port of a "traditional" ported cabinet?

what phase do you think it is wrt the cone's movement?

you may be surprised.

YOU CAN NOT PORT AN OPEN BACK CAB.

you're right. it's already ported.

In the hifi world open back cabs are not tolerated, that's why all of the out of phase signals are killed with "sound deadening material" before they can be heard by the listener. Of course you can manipulate the "Below 60 Hz waves", by forcing them to go through tunnels, and be delayed in time just enough to hit your ear drum in phase with the primary. This is a band-aid for "woofing-systems" that can not produce enough oomph at certain lower frequencies. However this activity impairs other frequencies above and below those that it helps. So it is a fine line between "gimmick" (think Bose), and value ( think Pro-sound).

wait... so you're telling me that audiophiles and hifi nuts don't use ported cabs?

i suggest you consider your reply carefully.

Bass guitar cabs can use them to some degree, But with guitar frequencies, they are usually so high that "the tunnels" would be so short that they are only theoretical.

how about a tunnel the thickness of a sheet of MDF or marine grade plywood? say, 3/4ths of an inch? do you think ports cannot be made to function with such short depths?

the way you mention port length makes me wonder: have you ever actually DESIGNED a ported speaker system? if so, tell me how you arrive at a particular port length.

There are ares on an opperating speaker cone that are actually out of phase with other areas on the same cone at the same time. This is one of main factors that determine how and why guitar speakers sound different than others: alternate paper thicknesses, different paper pulp fiber length, suspension stiffness, weight of the copper in the voice coil....ETC....These variables make a huge change in tone compared to porting or not.

totally agreed.

[Mr.coil]

This is becoming a waist of time...You completely missed what I was trying to shed light on.

Even though I do not know you...I feel like you are challenging me at some personal level. I have built a lot of cabinets/speaker systems...Most of them being HiFi... The main functions of a speaker cabinet is too provide a place to mount all the drivers, look pleasing, and to KILL all of the frequencies coming off the back of the woofer above 80 Hz (if not all of them). Remember the diaphragms of the other drivers are in their own enclosures, inside the main enclosure, for the same reasons.

You seem to be entangled in some kind of minutia brought to life by a marketeer.

Why don't you just get a 2-12 closed back cab , remove one 12 and Wallah!!! Now you can hear everything that comes off the back of the remaining speaker. Because now you have a closed back cabinet, that will sound like an open back, the only difference is... it will sound the same no matter what room it is in.

So to drive it home.... if you were to close down that 11 inch hole to some size/frequency that would actually have a "tuned effect" on the system...the SPL that will come out of that very small hole could not be heard over the sound of the primary note coming off the cone a few inches away. UNLESS IT IS A BASS NOTE.

Porting a guitar cab is a marketing ploy! Just like labeling the ends of a speaker cable..."Amplifier", and "Speaker" What over-financed person would think that the free electron in the outer orbit of a copper atom would know what direction the current flow is!!!!
I'll tell you what kind...An "Ill informed one" One that has been sold a "Bill of Goods"

I have more clients asking for sound deadening to be put in their closed back cabs than to have a port added!

Ask yourself this, where do you usually see the microphone placed on a "Guitar amp" in a live setting? In front the speaker, or somewhere else?

This may be off the point, but,....I have seen railroad enthusiasts, record the sounds of a "live steamer". Sometimes they use 1 microphone, (or two on the same stand for a stereo effect). However, sometimes they have a dozen or more...one on the smoke stack, another on the compressor, one on the squeaking parts, one on the generator....ETC.ETC.

Then in the editing room, mix them all together into a unrealistic final cut...it usually sounds pretty "Cool" ..but is it more realistic than the one or two mic deal.....No.

So is it realism that we are after here..or some kind of manufactured (pedal-based) reality.

FluxTone is about preserving what has been created naturally by an over-driven tube output stage, all the while, reducing the SPL.

Geez, now who's time am I wasting...sorry

MC

[kg]

You seem to be entangled in some kind of minutia brought to life by a marketeer.

no, you don't know me. :lol:

i buy parts and do everything myself.

if you want to impress me, argue with logic and evidence. i am critical by nature.

Porting a guitar cab is a marketing ploy! Just like labeling the ends of a speaker cable..."Amplifier", and "Speaker" What over-financed person would think that the free electron in the outer orbit of a copper atom would know what direction the current flow is!!!!
I'll tell you what kind...An "Ill informed one" One that has been sold a "Bill of Goods"

so open backed speaker cabinets are marketing ploys?

i don't know how many times i have to say it, but an open backed cab IS a vented cab. it is rather haphazardly/randomly aligned, and results are going to be all over the place, but IT IS VENTED.

you've got two choices for cabinets: either 1) it's sealed, or 2) it's not. (technically there's a third choice--an INFINITE baffle--but neither of us is talking about those. i have never seen an IB MI cabinet.)

whether or not this concept is popular, or whether or not it's common knowledge, i don't know--and i don't care. it's the truth.

when you slam ported cabinets as useless you're slamming EVERY KIND of non-sealed cabinet.

I have more clients asking for sound deadening to be put in their closed back cabs than to have a port added!

sure! i have two 4x12 cabinets sealed VERY WELL (with caulk) and stuffed to the gills with fiberglass insulation.

would i cut a port in them? no. i do not want the huge increase in compliance below the port tuning frequency, and am more interested in keeping cone excursion down.

THAT DOESN'T MEAN THERE'S NO BENEFIT--just none for my application.

you won't catch me loving open backed cabs either, for EXACTLY the same reasons! go figure.

This may be off the point, but,....I have seen railroad enthusiasts, record the sounds of a "live steamer". Sometimes they use 1 microphone, (or two on the same stand for a stereo effect). However, sometimes they have a dozen or more...one on the smoke stack, another on the compressor, one on the squeaking parts, one on the generator....ETC.ETC.

Then in the editing room, mix them all together into a unrealistic final cut...it usually sounds pretty "Cool" ..but is it more realistic than the one or two mic deal.....No.

let me ask you: what is your definition of realistic?

me, i've heard about a handful of recordings IN MY LIFE that sounded "realistic," which to me means that i could close my eyes and imagine myself as standing in a room with live musicians.

the funny thing is, most of those recordings that i consider gold standards have ABYSMAL recording characteristics... ie, frequency response, noise, dynamic range. in fact many of them are MONO.

is that realistic? hell, i have two ears. both of them hear. why would listening to a noisy, hissy, pop and scratched, restricted bandwidth, mono recording be the least bit realistic?

why would this whole forum be interested in the art of sound CREATION as opposed to sound REINFORCEMENT? why aren't we all making blameless zero thd amps that take the input signal and make it bigger, and do NOTHING else to the waveform?

because "realism" when it comes to art is completely subjective, whether you care to admit it or not.

So is it realism that we are after here..or some kind of manufactured (pedal-based) reality.

what an artist--ANY ARTIST--is interested in is 1) creating something they themselves like, and 2) communicating that creation to his/her audience. you give someone the tools to create and make that connection, then you have done your job.

whether or not what they're doing fits YOUR ideas of what "realism" is makes not a bit of difference.

looking down your nose and dismissing things (like ported guitar cabinets, or a multitrack recording of a giant steam locomotive) out of hand as nonrealistic shows ignorance, not wisdom.

FluxTone is about preserving what has been created naturally by an over-driven tube output stage, all the while, reducing the SPL.
MC

that's great! i am all for giving people more tools. if you re-read carefully i never once claimed your product did not deliver on its promises... which it may, or may not.

[Mr.coil]

thank you
MC

[J M Fahey]

I feel like you are challenging me at some personal level.

C'mon, ease off.
*This* Forum is a model of tolerance and education, compared to most others; I can't imagine you in many of them.
A friend's suggestion: harden yourself a little and learn to cool down before answering or in many other places (not here) they'll tear you to ribbons.
Problem is, for most people it doesn't really matter who's technically right , because many don't have the technical knowledge to analyze the fine points, but will judge both sides of a discussion based on external visible factors such as calmness, strength, cool head, etc.
Being nervous, jumpy, overly tight, isn't often associated with sageness.

Now to the point: this thread is about Eminence Flux Modulation, general consense hasn't being very flattering, (including your opinions), yet *they* aren't here complaining or taking personal offense !!!
Maybe they aren't aware of this little Forum?
Don't think so, whatever you Google in the area of troubleshooting or schematics soon brings you here, and once in, you are hooked, given the level of expertise and no-nonsense found.
Good luck.

[walkman]

Kg .... what makes you an expert besides that you DIY ? ive seen your site , you appear to be a self proclaimed expert. You appear to be shouting or perhaps a little put off by someone with different ideas from yours

Mr Fahey ... I respect your opinions , however you appear a little biased to a theoretical approach.

These are my perceptions ... i've done a lot of reading on this forum mainly to learn as happily admit i'm a beginner when it comes to electronics.

Reading some of the ampage archives , it appears that the first discussions of field coils and application to guitar amps comes somewhere in 2000. After that it doesn't reappear till round 2006, with some discussion in 2007 and 2008 about Ted Webers Feild coil power supply and Jensen Field coil speakers.

All many of the people who have commented in those past threads have also posted in this one including KG in 2000 .... what was never suggested by any one was to do what Mr Coil / Fluxtone has done , that is to create new feild coil speakers with OEM Cones and other parts. Also he has come up way , through his knowledge and experience to make sure the tone does not suffer.

And it doesn't i can attest to that , I paid some very good money for them ( my choice over buying another equivalently priced amplifier that i would not be able to play at home because it would be too loud).

This is a quote from woodyc ( who hasn't posted in this thread ) indicates there may be tonal compromises with a lower B field.

Re: Would a field coil speaker have adjustable sensitivi - AMPAGE Archive

Re: Would a field coil speaker have adjustable sensitivity?
There are a bunch of parameters in speaker design (mainly B field, moving mass, cone area, and suspension compliance), and they all work together to give a flat response. If you take a well-designed speaker and change any one of these things by itself the response will no longer be optimal.

In the case of dropping the field coil current, you will get less output, but the speaker will also get dark and boomy because with lower B the response gets peaked near the resonance. So it could make a cool power brake type thing, but you will probably have to simultaneously boost high end as you turn down the volume.

It seems like transient response could also suffer with low field current but I don't have an easy way of figuring that out.

I'd be interested to hear what happens if you ever try it.

Re: Field Coil Speakers + OP Transformers?? - AMPAGE Archive

Here is a quote from KG in 2000KG

i think the key here is the readily adjustable BL product of the speaker itself. you can change a whole host of parameters, namely Qes and efficiency, by tweaking the motor strength of the speaker.

feed the coil with a hi-po current source and you will get a magnet system that does NOT sag under any degree of back-emf. move towards a voltage sourced coil, and you will get increasing amounts of magnetic field collapse as the amplifier output power increases.

that's pretty cool, even for me.

soon you'll have maniacs implimenting midi switching circuits to adjust speaker parameters!

kg

Here is a summary of related threads that i found.

Re: Would a field coil speaker have adjustable sensitivi - AMPAGE Archive

5A5 Pro - F15N field coil connections - Bruce/anyone? - AMPAGE Archive

Re: Field Coil Speakers + OP Transformers?? - AMPAGE Archive

http://music-electronics-forum.com/t6959/

http://music-electronics-forum.com/t9018/

when I bought the Flux-tones i thought that maybe i Could buy on old Field coil and make my own adjustable speaker , I did in fact by an old jensen FC with that intention.
However i can see that even with a properly designed power supply for that , the results i would get , trying to lower the B field would not give me the results that Mr coil has achieved.

He has on his own produced this new innovation, which has been well accepted amongst those who have tried it and from the few comments he has made , it is more than apparent that he speaks from experience.

I guess he jumped in to this thread to , tell me put your money where you mouth is ....
He didn't know that in fact I had.

Walkman

[Mr.coil]

Well I am not sure who I am replying to anymore...

However, I will say to J M Fahey..thanks for the tips, I will try to incorporate them.

MC