Klipschorn bass response

[John Warren]

Mike tn-

"Minimum phase" means that the phase response vs. frequency and the amplitude response (spl) vs. frequency are related through a mathematical transformation (Hilbert's transformation). Having one relationship means that you've got the other. In a "non-minmum phase system" however applying the mathematical transformation to the measured phase relationship will not provide the measured amplitude response of the system. The difference is termed "excess phase". Reverberations, reflections, room gain, etc are "non-minimum phase errors" and the phase information is not a unique function of the amplitude response so changes to the amplitude response (EQ) will, as Heyser states, make things worse. When frequency response errors ARE minimum phase errors then ABSOLUTELY, changes to the amplitude response will improve anomolies in the FR. The problem however is one of identifying the "selective" conditions where the minimum phase errors are in the response (Heyser's paper) and so on.

That said, you've brought up a very good point. Under well instrumented conditions with the understanding of minimum phase, non-minimum phase, phase response errors, excess phase and the Hibert transformation, the use of EQ across selective portions of the FR "might" improve the room response.

jw

[John Warren]

Mike B.-You have to be clear as to what you are referring to as "acoustical impedance" and "all over the place". The impedance of a horn loaded driver "is what it is" and I don't mean to be provocative. The peaks are associated with "reactances" where the driver is, for whatever reason, working into a resonance. Make no mistake however, the "radiation resistance" of the horn is not reactive, it is not all over the place, it is a resistance that the driver must perform real work against and the result is an increase in electro-acoustic efficiency. The challenge in horn design (one of them anyway) is to load the driver so the resistive portion of the radiation impedance (the radiation resistance) spans as wide a range of frequencies (octaves?) as possible given the various physical and financial constraints. That's what Roy accomplished with the Jubilee.

[mikebse2a3]

Mike tn-

"Minimum phase" means that the phase response vs. frequency and the amplitude response (spl) vs. frequency are related through a mathematical transformation (Hilbert's transformation). Having one relationship means that you've got the other. In a "non-minmum phase system" however applying the mathematical transformation to the measured phase relationship will not provide the measured amplitude response of the system. The difference is termed "excess phase". Reverberations, reflections, room gain, etc are "non-minimum phase errors" and the phase information is not a unique function of the amplitude response so changes to the amplitude response (EQ) will, as Heyser states, make things worse. When frequency response errors ARE minimum phase errors then ABSOLUTELY, changes to the amplitude response will improve anomolies in the FR. The problem however is one of identifying the "selective" conditions where the minimum phase errors are in the response (Heyser's paper) and so on.

That said, you've brought up a very good point. Under well instrumented conditions with the understanding of minimum phase, non-minimum phase, phase response errors, excess phase and the Hibert transformation, the use of EQ across selective portions of the FR "might" improve the room response.

jw

John

Thanks for adding the description of minimum phase and non minimum phase behavior in a system.

Mike

In a past discussion were Heyser was mentioned I believe you mentioned you wanted to get a copy of Time Delay Spectrometry or locate some of his papers and if you haven't yet please let me know and I would be very happy to loan you a copy if your interested.

mike tn

[John Warren]

Roy--YOU DOG!

[Deang]

Am I seeing the inverse of the raw acoustic response?

[DrWho]

Mike B.-You have to be clear as to what you are referring to as "acoustical impedance" and "all over the place". The impedance of a horn loaded driver "is what it is" and I don't mean to be provocative. The peaks are associated with "reactances" where the driver is, for whatever reason, working into a resonance. Make no mistake however, the "radiation resistance" of the horn is not reactive, it is not all over the place, it is a resistance that the driver must perform real work against and the result is an increase in electro-acoustic efficiency. The challenge in horn design (one of them anyway) is to load the driver so the resistive portion of the radiation impedance (the radiation resistance) spans as wide a range of frequencies (octaves?) as possible given the various physical and financial constraints. That's what Roy accomplished with the Jubilee.

Well then, by "all over the place" I mean not a simple resistance. I understand that the ideal scenario in the ideal world is a flat resistance, but how often is that actually achieved? Or to be more specific, how ideal (in terms of the equations) is the khorn? I believe it was Roy who mentioned that a straigtened out khorn was something like +-1dB throughout its passband (basically following the ideal exponential predictions), but in its folded up form, it's "all over the place" due to all the folds. And I would think a lot of this would show up in the electrical impedance??? I really wish I could get my hands on some measuring equipment, an anechoic chamber, and a pair of khorns for a day. I'd be able to answer so many questions for myself.

Anyways, if you're telling me that you know the khorn's electrical impedance is effectively resistive through its passband, then I guess there's nothing to worry about...[] I don't like to rely on models and predictions, but I think they make good learning tools and get one close. It's just that every horn I've modelled shows a non-flat electrical impedance. For what it's worth, here is a plot of an eminence magnum in horn 'optimized' for a 32Hz to 320Hz passband. If I'm understanding correctly, every peak of the wiggles in the frequency response is represented by peaks in the electrical impedance? And ultimately they are harmonics of the fundamental reflection occuring from the impedance mismatch between the mouth of the horn and free air due to the exponential horn not having an infinite mouth? EDIT: just realized the non-flatness I saw was the result of reflections inside the rear chamber [] I guess it mostly is resistive in the crossover band - for an ideal nonfolded horn anyway...

[mas]

John & MikeTn make some very good points regarding minimum phase. And Doc does make a good point as well.

You cannot correct for frequency anomalies in the frequency domain except in a minimum phase condition.

You can correct for some frequency domain anomalies in the time domain (if only at a particular point or on a particular axis.). And you can avoid many frequency response anomalies by proper treatment of issues within the time domain!

The statement of John's that 'if you have one you have the other' (while correct), IMO does not go far enough...You cannot have one without the other! They arise simultaneously, just as the concept of yin and yang, heads and tales, or light and dark imply the existence of each other. Oh, you can certainly use any of many available testing methods and only display one or the other, but they are both there, as they are simply two points of view of the SAME event! You may weigh yourself or you may use a tape measure and measure your height, but it makes no sense to say that you can have one without the other, despite one's myopic point of view. The measurement that contains ALL is the Nyquist/Heyser spiral, or which the impulse response is the most common inclusive derivative from which frequency information may be derived.

The Hilbert transform maps two domains of a rotating phasor (Nyquist/Heyser spirals, differing only in terms of whether time or frequency is chosen for the Z axis) by virtue of a 90 degree shift in perspective. I realize that the diagram is too small to read, but you might want to simply glance at my avatar and guess at the projections upon the vertical (imaginary) plane and the horizontal (real) plane.

If I mentioned that the real domain represents potential energy and AC resistance and that the imaginary domain represents kinetic energy and reactance, and that this complete transform can be displayed for 'all' frequencies and for 'all' time, would that really simultaneously confuse and offer a tantalizing taste of potential ramifications in a system? Well, enough of my simply appearing and stirring things up!!! (What???Who??? Me!?!?) [][^o)][*-)]

To understand this requires a discussion of the Nyquist and Heyser spirals and the topological mapping of various domains to one another, and while I would love nothing better (actually, this is my passion!), I have not yet been able to address the room acoustics topic due to allowing myself to get off track and trying to deal with superposition and a few other topics as intros as they will come back to bite us as so many seem to have so much difficulty with these fundamentals.

I will stay out of this discussion as much as possible and simply enjoy it from the sidelines, as I am already busier than I would like to be this time of year! But I will try to get around to this eventually.

Just realize that you have simply touched the tip of a very large and very significant and fundamental iceberg that requires an understanding - and is the big issue that many of the 'more advanced' folks should want to know about - as this is the real holy grail from which the time domain is but one major point of view that arises.

Enjoy.

BKDomainMap.pdf

[mas]

Oh, I will add one more editorial comment and then I will be quiet (I will wait a few moments for the applause to subside...)

It would be nice to see manufacturers publish both the impulse response (at the very minimum) and ideally the Nyquist/Heyser response of a system - especially if the file was made available in a form that is convolvable by the many tools available.

And while some will argue that many will not understand them (as if most - especially the marketing departments of the various organizations - understand the 'normal' nonsense specs that are posted!), I fear the real issue is that the availability of real specs that can be meaningfully explored is perceived as a greater threat than they are an asset.

It seems that this point alone speaks more to the orientation of a company than any other aspect. Legitimate companies with real products need not fear examination of a system by interested parties. And the point of this is not to evaluate a piece of equipment against an abstract ideal, but rather to examine it with respect the the design parameters and the intended use - for as Doc reminds use in his profile statement, all responsible designs involve a set of stated goals - and thus responsible compromise is always a fundamental component of design. And thus a proper context for examination and judgement is established.

Thus, in far too any cases, the silence is deafening.

[DrWho]

I suppose that begs the question...just how does one best accurately measure the impulse response? I'm sure the marketing departments will find ways to skew them too [6]

[Coytee]

I wish you dudes would speak in English so us mortals could semi-understand what in the blazes you're talking about!! I need to start a thread and talk about naked spreads...

[:^)] [:^)] [:^)]

[DrWho]

lol Richard, by all means ask questions on the bits you don't
understand...that's how I learned the little bits and pieces over the
years. If you don't want to get caught up in the math, here's a simple
explanation:

In theory world, the amplifier is just putting a
voltage on the wire...you know, that whole V=IR thing. The R
(resistance) is determined by the speaker and the V (voltage) is
determined by the amplifier. The I (current) is the result of the
voltage and resistance relationship and is what drives the electrical
forces inside the motor driver. So if you increase the voltage, you are
going to get more current to flow and thus more power coming out of the
driver.

A network (or any passive filter) is just something you
put in the way to reduce the voltage seen by the driver. So to keep low
frequencies away from a tweeter, we can lower the current flowing
through the tweeter at the lower frequencies. The resistance of the
driver is a fixed variable so the only thing you can adjust is the
voltage that the driver sees. This is what the voltage transfer
function of the crossover network is showing us.

The only thing
making it more complex is that the resistance of the speaker is
different at every frequency. So instead of calling it a resistance, we
call it an impedance. So by nature, different amounts of current are
going to flow at different frequencies...but this is a good thing
because at frequencies where the speaker is "too loud" (usually due to
a resonance somewhere) the impedance is also high. That means less
current is flowing through the motor in areas where it's already too
loud. This is a very loose description because really the impedance and
acoustical behavior are directly related, but you really don't need to
understand all that crap when learning the basics of filter design.
Anyways, the reason the varying impedance is important is because the
behavior of inductors and capacitors is going to change based on the
impedance of the driver. Namely, the frequencies at which they lower
the voltage are going to change. The end result is a different
crossover point than originally intended.

As far as the time and frequency domain thing...there is some
annoying math that proves the time and frequency domains are directly
related through some transforms. So basically, if you make a change in
the frequency response, then the impulse response is going to change
too. The nice thing about measuring an impulse response is you can
directly derive the frequency response and I believe you can also
derive the effects of the room too? And you can see the room and
speaker completely independant of each other? That is one area that I'm
hoping to learn more in...I've got me a program now (thanks Mark) that
will convolve impulse data, but now I need measurements to plug in and
play with []

[mas]

Coytee, you have a PM...

You've been warned! [:|] []

[Deang]

You should be required to mail aspirin out to people before you post!

[bodcaw boy]

Oh, I will add one more editorial comment and then I will be quiet (I will wait a few moments for the applause to subside...)

It would be nice to see manufacturers publish both the impulse response (at the very minimum) and ideally the Nyquist/Heyser response of a system - especially if the file was made available in a form that is convolvable by the many tools available.

we used to publish this and other pieces of info for our pro gear but we found that they there really did not mean much to the end user.

And while some will argue that many will not understand them (as if most - especially the marketing departments of the various organizations - understand the 'normal' nonsense specs that are posted!), I fear the real issue is that the availability of real specs that can be meaningfully explored is perceived as a greater threat than they are an asset.

It seems that this point alone speaks more to the orientation of a company than any other aspect. Legitimate companies with real products need not fear examination of a system by interested parties. And the point of this is not to evaluate a piece of equipment against an abstract ideal, but rather to examine it with respect the the design parameters and the intended use - for as Doc reminds use in his profile statement, all responsible designs involve a set of stated goals - and thus responsible compromise is always a fundamental component of design. And thus a proper context for examination and judgement is established.

Thus, in far too any cases, the silence is deafening.

roy delgado

[John Warren]

Roy-

Any chance we can have a look at the measured amplitude response of the Klipschorn with tha AK-4 net? And, since I'm asking, could you also post the response of one of the earlier nets for comparison. My interest (obviously) is to see how the added elements alter the response. If you can't post I understand, but I figured I'd ask anyway.

I would think that literature (a cut sheet of some type) that shows a favorable comparison of the new nets to earlier versions would be useful to those interested in upgrading there units.

jw

[Deang]

Thanks for reinserting those earlier plots John.

Earlier in the thread, this exchange:

John: Based on your response, the AK-4 has some frequency compensation circuits built into it.
Roy: Yes it does.
John: I'd be interested in seeing the topology (and yes I know I could "buy" a pair but what fun would that be!) and I am also aware that you can't reveal the information.
Roy: The schematic is known and been published here, and in fact, mr crites, if he is on tonight, can supply it. if not, i can get it somewhere.
John: Is there any possibility that you could show us the measured frequency response of the bass horn with the AK-4 filter branch?
Roy: i am sure we got that somewhere.

Roy,

I'm pretty sure the AK-4 schematic has never been published before, and the general rule has been that Klipsch doesn't give out schematics on current production loudspeakers. Does that mean there is an AK-5.

[bodcaw boy]

Roy-

Any chance we can have a look at the measured amplitude response of the Klipschorn with tha AK-4 net? And, since I'm asking, could you also post the response of one of the earlier nets for comparison. My interest (obviously) is to see how the added elements alter the response. If you can't post I understand, but I figured I'd ask anyway.

I would think that literature (a cut sheet of some type) that shows a favorable comparison of the new nets to earlier versions would be useful to those interested in upgrading there units.

jw

john,

i think that this is our standard lf with the ak 4 lf passive.

roy delgado

khornlf1.PDF

[bodcaw boy]

Thanks for reinserting those earlier plots John.

Earlier in the thread, this exchange:

John: Based on your response, the AK-4 has some frequency compensation circuits built into it.

Roy: Yes it does.

John: I'd be interested in seeing the topology (and yes I know I could "buy" a pair but what fun would that be!) and I am also aware that you can't reveal the information.

Roy: The schematic is known and been published here, and in fact, mr crites, if he is on tonight, can supply it. if not, i can get it somewhere.

John: Is there any possibility that you could show us the measured frequency response of the bass horn with the AK-4 filter branch?

Roy: i am sure we got that somewhere.

Roy,

I'm pretty sure the AK-4 schematic has never been published before, and the general rule has been that Klipsch doesn't give out schematics on current production loudspeakers. Does that mean there is an AK-5.

dean,

your're right but i thought that by now someone had reverse engineered to get a schematic like mr bob! i know that someone, speakerfritz or jc i believe, had done the al4 which is very close to the ak4 (same topology).

roy delgado

[DrWho]

i think that this is our standard lf with the ak 4 lf passive.

mmmm, that is much pertier than the raw response of the bass bin [Y]

[IndyKlipschFan]

coytee said, "I need to start a thread and talk about naked spreads... "

hahahahaha

For instance.... being uncovered (Naked) with no underlying security position, or not hedged from a market position, can be dangerous. NOW your talking MY language!!!

We all live and work within our language and industries too. Now Call her up and Put her down good!