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Old 14th August 2010, 11:38 AM   #7161
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I believe the phenomenon that Michael calls CMP is one way of describing the mechanism that causes the measured frequency response of a dipole.

Michael, try repeating your simulation but feed it with an impulse rather than a sine wave. Now perform a FT on the output. I suspect the result will be a classic dipole frequency response curve.

Am I right or wrong?
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Old 14th August 2010, 12:22 PM   #7162
JohnPM is offline JohnPM  United Kingdom
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Whilst I'm in a bubble-bursting mood I suppose I'd better deal with what I think is one of the other "CMP" claims, which (without having the energy to trawl through the hyperbole) I think boils down to "I have managed to equalise a null".

I suppose we could talk for a while about minimum phase systems and invertibility, but I suspect there has already been a fair amount of that. The problem of nulls boils down to multiplying by zero. When systems are connected in series, their overall transfer function (frequency response) is the product of their individual transfer functions. If one of the transfer functions is zero somewhere there isn't anything the other transfer function can do about it, so a claim to have equalised a null amounts to having proved that 0 x 1 = 1. The world would be a much stranger place if that were true, so as I think I posted previously if the world doesn't agree with your model, it won't be the world that's wrong.

It is more likely that what has been proven is that 0 + 1 = 1, which while less exciting is at least true. What that means is that somewhere in the miracle equaliser model the system supposedly being equalised and the equaliser are actually connected in parallel rather than in series, with their outputs being added. In the context of a setup where one of those systems represents the transfer function from a loudspeaker to a listener that is rather difficult to achieve, since it would require a path that doesn't go through the loudspeaker - such as another loudspeaker, but I don't think many people would be happy using a loudspeaker to try and equalise a loudspeaker, not least because it wouldn't work. So I'm forced to conclude that the miracle null equaliser doesn't actually exist and the claim is based on a flawed model.
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Old 14th August 2010, 12:22 PM   #7163
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Quote:
Originally Posted by soongsc View Post
Is there any textbook explanation of CMP? Perhaps this would help the discussion significantly. I am interested in knowing about the phenomenon of CMP.
CMP is just something Michael make up. I have said this before and will once more then I'm out of here. What Michael calls a CMP system is really the a system composed of the summation of several systems. Taken separately, each of these individual system would have a steady state response of its own. But taken as a sum, the system response has a steady state response only when both (or all) the components are at steady state.

Now, and Michale perhaps you will like and appreciate this, if the delay between the start up of the additional components of a system is sufficiently long that the first component reaches steady state before the additional components even start, then what we will see in the time response is the approach to steady state of the first component followed by a transition to the steady state of the complete system. But these are not multiple steady states of the complete system.

An example of this is the simple room measurement and quasi anechoic component. When we measure a loud speaker in a reverberant room, if the delay before the first reflection is 5 msec we window the impulse to a length of 5 msec and we perform and FFt of that portion of the total impulse. We say that represents the SS FR of the speaker. It does, at least down to 200 Hz. But this is not the SS FR of the room/speaker system. The SS FR of the room/speaker system is the FFT of the entire impulse response, including all the reflections. The point is that by looking at the initial part of the impulse we are able to get an idea of what the SS FR of one component (the speaker) of the room/speaker system is. This is not one of multiple SS FRs for the system. It is the SS FR of one component of the system, and one which we happen to be interested in.

The same thing applies to gated sine wave measurements. If we can gate the system response so that the speaker component of the system reaches its steady state before the other components of the system enter the picture (reflections etc) then we can see what the speaker is contributing to the system.

What I object to is the implication that the complete system has multiple steady states. It does not. The system has only one SS. However, when divided into individual components each components of the system has its own SS.

Michael is concerned with systems with delays, but this applies to any system composed of multiple sources. A simple two way speaker, for example, has a woofer and a tweeter. The woofer and tweeter each have their own SS response. But neither represents the SS response of the speaker which is the SS response of the sum of the woofer and tweeter response. And certainly there is a delay between the tweeter and woofer response that is typically seen in the system's impulse. If the delay between woofer and tweeter were extremely long, like over 1 msec, then we might be able to window the speaker's impulse and see what the tweeter was doing, at least down to 1 k Hz, and that might represent the SS response of the tweeter, but not the SS response of the speakers.
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Old 14th August 2010, 01:14 PM   #7164
Elias is offline Elias  Finland
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Your analysis is too simplisctic.

Instead if you write
(0 + |e|)*(u + |e|) = 1
where limes(e) -> 0 and limes(u) -> oo
it can be seen that CMP system can be equalised with an equaliser having impulse response h where limes(h) -> 0 and limes(length(h)) -> oo.


- Elias

Quote:
Originally Posted by JohnPM View Post
Whilst I'm in a bubble-bursting mood I suppose I'd better deal with what I think is one of the other "CMP" claims, which (without having the energy to trawl through the hyperbole) I think boils down to "I have managed to equalise a null".

I suppose we could talk for a while about minimum phase systems and invertibility, but I suspect there has already been a fair amount of that. The problem of nulls boils down to multiplying by zero. When systems are connected in series, their overall transfer function (frequency response) is the product of their individual transfer functions. If one of the transfer functions is zero somewhere there isn't anything the other transfer function can do about it, so a claim to have equalised a null amounts to having proved that 0 x 1 = 1. The world would be a much stranger place if that were true, so as I think I posted previously if the world doesn't agree with your model, it won't be the world that's wrong.

It is more likely that what has been proven is that 0 + 1 = 1, which while less exciting is at least true. What that means is that somewhere in the miracle equaliser model the system supposedly being equalised and the equaliser are actually connected in parallel rather than in series, with their outputs being added. In the context of a setup where one of those systems represents the transfer function from a loudspeaker to a listener that is rather difficult to achieve, since it would require a path that doesn't go through the loudspeaker - such as another loudspeaker, but I don't think many people would be happy using a loudspeaker to try and equalise a loudspeaker, not least because it wouldn't work. So I'm forced to conclude that the miracle null equaliser doesn't actually exist and the claim is based on a flawed model.
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Old 14th August 2010, 01:23 PM   #7165
mige0 is offline mige0  Austria
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Quote:
Originally Posted by john k... View Post

Now, and Michale perhaps you will like and appreciate this,
....

John, as you most certainly know, I basically always appreciate your comments !


Though there is a lot I'd like to hold against your line of thinking and your arguments thereof, I'll better keep my mouth shut for a while, at least regarding CMP - acute oxygen deficit in outer space - need to economize, you know


Quote:
Originally Posted by JohnPM View Post
Whilst I'm in a bubble-bursting mood ...
I love your mood - much like Don Quixote


Michael


Michael

Last edited by mige0; 14th August 2010 at 01:30 PM.
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Old 14th August 2010, 01:38 PM   #7166
Elias is offline Elias  Finland
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Hi,

Actually I remembered I've dealed with thie earlier in another thread. My ideal row of impulses is a "CMP" system.

That time I pondered what is the "correct" "frequency response" to present.

First picture showing wavelet transform of impulse row using very short wavelet. At time 0 the "frequency response" is flat.
Click the image to open in full size.


Second picture showing same system but now with a longer wavelet. At time 0 the "frequency response" has comb filtering effects.
Click the image to open in full size.



- Elias
Attached Images
File Type: png ideal_reflections_mrwl_1.PNG (44.9 KB, 401 views)
File Type: png ideal_reflections_mrwl_3.PNG (93.1 KB, 403 views)
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Old 14th August 2010, 02:39 PM   #7167
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Quote:
Originally Posted by Don Hills View Post
I believe the phenomenon that Michael calls CMP is one way of describing the mechanism that causes the measured frequency response of a dipole.




Yes, this all started many pages ago when the double impulse of a naked, unequalized dipole was brought up. I pointed out that it was not relevant because the dipole response has to be eq'ed to some band pass response suitable for use as a loudspeaker and once eq'ed to the appropriate band pass response the impulse of the eq'ed dipoles system will be identical to that of the target. Since then the discussion has been a colossal waste of time, mine included.
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Old 14th August 2010, 02:45 PM   #7168
mige0 is offline mige0  Austria
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the roots actually go back (more pin point) to my growing interest in diffraction alignment device - just for the record - and even way beyond that (more blurred), as one can dig up in that very thread


Once again Lynn - thanks for the great platform you allow here

Michael
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Old 14th August 2010, 02:46 PM   #7169
soongsc is offline soongsc  Taiwan
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Thanks for the explanation JohnK.
I think a series of systems combined together is in fact one system. Of course any system can be structurally analyzed to determine what part has what effect, but it's generally not necessary to wait for a certain part to reach steady state to do this. It seems inventing a new term like CMP just clouds the issue, things that normally marketing persons do well.

Michael, it seems you have invented a few terms, one of which I seemingly recall is was already trademarked by another company. Are you doing marketing as a proffession?
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Old 14th August 2010, 03:13 PM   #7170
mige0 is offline mige0  Austria
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Originally Posted by soongsc View Post
Michael, it seems you have invented a few terms, one of which I seemingly recall is was already trademarked by another company. Are you doing marketing as a proffession?
Great joke, George !!! you opt to buy ???
And I thought, I'm rather in the entertaining biz here.

Last edited by mige0; 14th August 2010 at 03:37 PM.
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