Beyond the Ariel - Page 650 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th December 2009, 11:25 PM   #6491
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally Posted by mige0 View Post
...
Isn't vertical scale the equivalent in SPL ? So - I don't see the problem ?

Remember its linear scale in IR plots !
Frequency response certainly looks good enough to be called "min phase" - no?





...
Michael
Well, it basically means the FR is lower, thus the phase is also changed when you go off angle. If the phase varies in this beam range, then it cannot be minimum phase can it? Or what is you minimum phase definition? Maybe I'm misunderstanding something.
__________________
Hear the real thing!
  Reply With Quote
Old 10th December 2009, 11:34 PM   #6492
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by soongsc View Post
Well, it basically means the FR is lower, thus the phase is also changed when you go off angle. If the phase varies in this beam range, then it cannot be minimum phase can it? Or what is you minimum phase definition? Maybe I'm misunderstanding something.
Hi George,

All minimum phase means is that for any measured response the phase can be reduced to the minimum phase (as obtained from an HBT) plus excess phase resulting from a delay (a linear phase component). Minimum phase for a 3-dimensional sound field only means that as the amplitude changes with position, so does the phase in accordance with the HBT of the amplitude.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 10th December 2009, 11:45 PM   #6493
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally Posted by john k... View Post
Hi George,

All minimum phase means is that for any measured response the phase can be reduced to the minimum phase (as obtained from an HBT) plus excess phase resulting from a delay (a linear phase component). Minimum phase for a 3-dimensional sound field only means that as the amplitude changes with position, so does the phase in accordance with the HBT of the amplitude.
Hi John,

I was just questioning the fact why a horn would be called a minimum phase horn taken the fact it's performance and design seems very normal. Use of such technical term should have something unique to the actual design or performance.
__________________
Hear the real thing!
  Reply With Quote
Old 11th December 2009, 10:33 AM   #6494
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by soongsc View Post
Hi John,

I was just questioning the fact why a horn would be called a minimum phase horn taken the fact it's performance and design seems very normal. Use of such technical term should have something unique to the actual design or performance.

Yes, me too. Measure the response. It either reduces to MP or it doesn't. Just because there are HOMs or diffraction effects that may have time domain artifacts doesn't mean it won't remain MP.

But one other thing I have not seen discussed, and I would like to see some horn experts clear up for me, is that, according to the simple horn threory presented by Kinsler and Frey, horns are dispersive; difference frequencies propagate at different speeds. I.e. the speed of sound can not be considered constant. This would, by nesessity, make a horn non MP.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.

Last edited by john k...; 11th December 2009 at 10:44 AM.
  Reply With Quote
Old 11th December 2009, 12:45 PM   #6495
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by john k... View Post
Yes, me too. Measure the response. It either reduces to MP or it doesn't. Just because there are HOMs or diffraction effects that may have time domain artifacts doesn't mean it won't remain MP.
Hi John - my opinion is the same here. I never did see anything in the MP discussion of waveguides that made any sense. But HOM will not be MP - they have a "trace" velocity along the axis that is different from the main wavefront.

Quote:

But one other thing I have not seen discussed, and I would like to see some horn experts clear up for me, is that, according to the simple horn threory presented by Kinsler and Frey, horns are dispersive; difference frequencies propagate at different speeds. I.e. the speed of sound can not be considered constant. This would, by nesessity, make a horn non MP.
The answer is simple - it doesn't happen, "Horn" theory is wrong.

But, even in waveguide theory, at LFs the modes become complex and do appear to have dispersive effects, but these are not propagating modes, they are evanescent - they disipate exponentially as they travel. So any real propagating wavefront will have a standard wave speed along its waveFRONT. But the wavefront may not be propagating along the axis, hence the speed down the axis of the waveguide will not be the same as the speed of the wavefront.

In Horn theory a real propagating wave at cutoff IS certainly dispersive, but thats precisely where the theory fails. If you take the exact theory of an OS waveguide - which has an analytic solution correct in all aspects - and you apply the Horn equation to its contour you will see that the two solutions differ most precisely at "cutoff". The horn equation predicting dispersion and "cutoff" and the waveguides equations predicting no such thing. At higher frequencies they agree in impedance, but not in wavefront shape, and they disagree completely at LFs, horn theory predicting no sound transmission and the waveguide predicting evanescent wave propagation. Clearly the waveguide equations are the correct ones since this is what happens in a real device.

Another example of where I just don't see how the concept of MP is useful in acoustics.

Last edited by gedlee; 11th December 2009 at 12:52 PM.
  Reply With Quote
Old 11th December 2009, 01:18 PM   #6496
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by gedlee View Post
Hi John - my opinion is the same here. I never did see anything in the MP discussion of waveguides that made any sense. But HOM will not be MP - they have a "trace" velocity along the axis that is different from the main wavefront.


I know that we disagree on the MP argument, but I still hold that if we stick out a mic and measures the response at that point, it either reduces to MP plus linear excess phase or it doesn't. HOMs, diffraction, etc may have delays associates with them but that doesn't mean that the net measured response at the observation point can not be reduced to MP pluse a linear excess phase. I haven't measured horns, but the few wave guides I have looked at on tweeters have all shown to have the MP pluse linear phase bahavior. And I certainly haven't seen a measurement of a tweeter on a baffle where the net response, direct plus diffraction, isn't the same, MP plus linear excess phase.

Anyway, things like MP and acoustic centers are pretty useless. I just measure the drivers and removed the excess delay to the mounting flange or fact plate. In that manor I have a good reference point for on axis design.

Thanks for the comments re horn theory.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 11th December 2009, 01:22 PM   #6497
mige0 is offline mige0  Austria
diyAudio Member
 
mige0's Avatar
 
Join Date: Jan 2005
Location: Austria, at a beautiful place right in the heart of the Alps.
Quote:
Originally Posted by soongsc View Post
Hi John,

I was just questioning the fact why a horn would be called a minimum phase horn taken the fact it's performance and design seems very normal. Use of such technical term should have something unique to the actual design or performance.


What actually *is* a horn ? – we possibly must ask first !

To me – and certainly 99% of people out there - it’s a shape .
A horn is a simple shape or structure of quite some stiffness or rigidity starting out big in diameter and ending in a tip after some distance.

When ancient audio freaks discovered that this very shape has special properties when used upside down and replacing the tip by a driver, trumping through the hollow structure – the run after the *magic* contour of horns in speaker design begun.

(literally spoken, the story might have begun even earlier… )

In the years to follow that great discovery - a lot of “special” horns were named :

Conical horns
Exponential .horns
Kugelwellen horns
and so on and so on...

A first mayor turn in looking at horns I see with the development of constant directivity horns.
The ingenuous lies in that these guys were solely after a well defined effect in the resulting sound field - rather than in a hunt to invent new formulas of horn boundary curves.

With Earls
Oblade sheroide horns
I see the next logical step of evolution, in that Earl aimed after – what he thinks is - low diffraction effects *AND* not giving up the CD concept - which in *his* context still is defined as to provide "good audience coverage" first.

With Jean-Michel's LeCleach horn contours – or better put "contour corrections" based on a water right concept of wave front propagation - I see that horns mainly intended for *high quality audio* greatly developed towards smooth and consistent sound filed outcome.
The main drawback I see with Jean-Michel's designs is that advanced directivity control wasn't at top priority – until now at least.

One further step could be considered to look at horn's as to be a diffraction alignment device.
Seeing diffraction as the necessary and actually only (practical) mechanism to smoothly bend the vector of wave fronts "around the corner".

In that context my naming of Min Phase horn is narrowed to smooth and consistent sound fields to result from such designs *PLUS* to stay as close as possible to min phase behaviour to allow to benefit from advanced equalising over an as wide as possible room angle.
This – to my knowledge – *is* quite new and unique and certainly not a small change of the audio paradigm in general – both from the underlying philosophy involved and from the outcome to await.

It's not that I claim to have the "best ever" solution of [/b]Min Phase [/b]horns discovered or developed yet (nor even that I restrict it to *my* effort at all) – its about setting the general *aim* apart form what's been on the list until now.
A new classification if you will.

So - if you watch the stars - by a telescope you have not built - and discover a new structure there - that neither belongs you nor ever will – nevertheless you are tempted to give it a name.


the naming of "min phase" - a simple act of personal pride



Bottom line – its just a looooot of name dropping involved in that horny issue...

Michael

Last edited by mige0; 11th December 2009 at 01:46 PM.
  Reply With Quote
Old 11th December 2009, 01:49 PM   #6498
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally Posted by john k... View Post
I know that we disagree on the MP argument, but I still hold that if we stick out a mic and measures the response at that point, it either reduces to MP plus linear excess phase or it doesn't.
Actually John I don't disagree with you at all becasue to me the next line is the point
Quote:
Anyway, things like MP and acoustic centers are pretty useless. I just measure the drivers and removed the excess delay ...
Agreed - to me the concepts of MP don't come in all that handy in the acoustics domain that's all. I don't disagree with anything that you said at all.
  Reply With Quote
Old 11th December 2009, 01:55 PM   #6499
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally Posted by mige0 View Post


the naming of "min phase" - a simple act of personal pride



Bottom line – its just a looooot of name dropping involved in that horny issue...

Michael

Yes, but I haven't seen ant measurements presented that indicate a typical horn any more or less MP that a driver on a baffle is by the definition I put fourth. I looked a coupe of compression driver with different off the shelf, cheap horns or wave guides (to me the difference is semantics) and they all seem to be MP. Where is the departure from MP behavior?

Also, for what its worth, I see a horn and wave guide as the same thing with the primary difference being that a horn's primary function is gain where as a wave guide's primary function is directivity control.

Oh, and by the way, looking at the an impulse generally can not tell you if a device is MP or not.
__________________
John k.... Music and Design NaO Dipole Loudspeakers.
  Reply With Quote
Old 11th December 2009, 02:56 PM   #6500
mige0 is offline mige0  Austria
diyAudio Member
 
mige0's Avatar
 
Join Date: Jan 2005
Location: Austria, at a beautiful place right in the heart of the Alps.
Yes this is the paramount point you were teaching us.

The pointe behind min phase that I see is that the way you looked at this in audio was the starting point to look at advanced equalization as a possibility to come to close to ideal behavior over a wide room angle (response shaping at will).

Hence I have choosen "Min Phase" horn rather than "Michael Gerstgrasser" horn - together with what I see unique as my "diffraction alignment" concept for horn contours in general I think its a justification to establish a "new" name.

Michael

Last edited by mige0; 11th December 2009 at 03:03 PM.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 01:11 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2