Click title to read one, or click date to read all below it.
04-11-05
All designers are trying to make intelligent choices in tryi ... Viridian
04-11-05
Viridian. your explanation is helpful but leaves me wonderi ... Dodgealum
04-11-05
I don't have the technical chops to make a great contributio ... Drubin
04-11-05
Ahhh, but it would seem you do have the phase chops for this ... Sogood51
04-11-05
To answer your questions, the general benefits of a 6db per ... Viridian
04-11-05
Time/phase coherance is the primary advantage of a first ord ... songwriter72@
04-12-05
"time/phase coherance" as viridian notes above, 1 ... Gregm
04-12-05
Darn, marty, apart from the humor you so graciously provide ... Trelja
04-12-05
Richard hardesty is a big advocate for 1st order crossover s ... Mds
04-12-05
6moons did a piece on the green mountan continuum last novem ... Drubin
04-12-05
Great article, interesting that he ascribes the changes he h ... Viridian
04-14-05
Songwriter, thanks for alerting me to the earlier forum disc ... Dodgealum
04-14-05
It is really not jeff joseph's contribution at all though, n ... Viridian
04-14-05
Viridian. you are no doubt correct. my reference to joseph ... Dodgealum
04-14-05
Ah, the jse infinite slopes... i really liked the smaller ... Trelja
04-14-05
Dodgealum, oops, sorry, i missed the reference. i'm kind of ... Viridian
04-14-05
I find it curious how little mention there is of joseph audi ... Drubin
04-16-05
Dogelealum, your very welcome. for a better understanding of ... songwriter72@
04-17-05
That paper concludes: "... the phase distortion audibi ... josephaud@
04-17-05
One has to take into consideration the fact that the speaker ... songwriter72@
04-17-05
After you hear a true full range point source omni driver, a ... Sean
04-18-05
Do the models in the current walsh mk ii series qualify? Drubin
04-18-05
Drubin: those aren't walsh drivers, they aren't omni's or a ... Sean
04-18-05
Thanks. okay, so who makes a "true full-range point so ... Drubin
04-18-05
Drubin: i don't know of any that are currently in production ... Sean
04-18-05
I owned ohm fs for many years and remember them fondly, i ha ... Viridian
04-18-05
It's true, today's ohms are walsh-inspired. they are, howe ... Zkzpb8
04-19-05
Viridian: all drivers exhibit some type of roll-off that is ... Sean
04-19-05
Sean, next time i'm in chicago, can i come over? Drubin
04-19-05
Me too; i'll bring the barbeque! i would take issue with the ... Viridian
04-19-05
Drubin: one set of my f's are "smoked" and awaitin ... Sean
04-20-05
One of the major advantages of the first-order crossover, wh ... Karls
04-20-05
Nice to see you here again, karl. (maybe you've been around ... Drubin
04-20-05
Hey sean: this is my first posting ever, but i couldn't resi ... Hthf
04-20-05
I'm going to let everyone know when bill finishes his own oh ... Trelja
04-20-05
I haven't read this entire thread, but it's not clear that a ... Suits_me
04-21-05
Off-axis lobing. sounds ominous. frankly, i honestly cannot ... songwriter72@
04-22-05
Off-axis lobing causes non-linear frequency response i.e. ad ... Sean
04-22-05
Suits_me: you are correct, it is possible to make even firs ... Karls
05-06-05
The lobing is actually due to having 2 spaced sources of the ... Skrivis
05-06-05
I cannot really add to the science, but i would like to add ... Seandtaylor99
05-06-05
Placing the speakers well out in the room should reduce earl ... Skrivis
05-06-05
"i'm not positive that phase-coherency leads absolutely ... Seandtaylor99
05-06-05
the lobing is actually due to having 2 spaced sources of the ... Suits_me
05-07-05
Every step up in xover order shifts the phase between tweete ... golix@
05-09-05: greenmountainaudio@adelphia.net
Dear Golix,
We have exchanged some thoughts on the Time Coherence thread- thank you for sharing those. I greatly respect what Tannoy has done for sound quality, as I can tell you do. Certainly working in a studio qualifies you to know when a speaker's distortions are minimized.
Some corrections, please, to your information above, in the spirit of technical accuracy in our comments:
As I described in the recent Time Coherence thread, the phase shifts by 90 degrees, yes, for each additional order of crossover, as you state above.
But do know that the correct expression to use is that the phase DIFFERENCE is changed by 90 degrees for each additional order- at the CROSSOVER FREQUENCY. Those are important distinctions.
You see, the problem caused by higher-order crossover circuits is that this phase difference is ALWAYS CHANGING as one moves away from the crossover point- a DIFFERENT time delay is being imposed on each and every frequency.
This ever-changing phase difference (ever-changing time delay) CANNOT be corrected with any additional circuit.
The math also shows, without question, that this ever-changing phase difference/time-delay distortion cannot be "fixed" by inverting the tweeter's polarity.
Flipping a tweeter's wires from + to - serves only to flatten the frequency response, when one measures using continuous sine-wave test tones or continuous pink noise.
Those are both unchanging signals, without beginning nor end (and therefore carry no information). These test signals do not indicate anything about WHEN things happen- about the time-delay distortions that are occuring, frequency-by-frequency. When the tweeter's wires are reversed, the resulting transient response has only a "different kind" of inaccuracy, even though one will like "the tone balance better".
Only a first-order crossover has a CONSTANT PHASE DIFFERENCE at every frequency above, at, and below the crossver point. That means there is Zero change in phase between them, so the signals out of the high- and low-pass sections are "in Phase", always, on every frequency.
And all of that means, finally, that first-order circuits are the only ones that pass all their signals through with the SAME time delay, so all of those emerge in the same time-order in which they entered. This is called time-coherent behaviour. So you get the original transient, one not smeared out in time.
A speaker that is designed to deliver a time-coherent output is automatically "phase coherent". The converse is not true, as you may know: A phase-coherent speaker is not necessarily a time-coherent speaker. In fact, if you see the advertisement claim phase coherency, you can bet that the speaker is not time coherent. One has to put something in an ad!
On the Tannoys, their "phase distortions" (time-delay distortions) are rather mild. In my experience, once those varying delays are removed (which cannot be in Tannoys), the difference you'd hear is at least the difference between an average mic and an outstanding one. By the way, neither a phase- or time-coherent behaviour can be directly inferred by looking at the electrical phase of a speaker's impedance curve.
That the Tannoy's phase distortion is tolerable for you, is because it is unconsciously ameliorated in those studios by their mic selection, mic technique, the type and tone of the echo/reverb mixed in, the settings of the tone controls on the mic's channel, and by the EQ applied to the monitor system. And in pop music, the phase shift problems are also "danced around" by the sounds created by compressors, limiters, de-essers, and other tools. I speak from many years of recording experience, and of designing speakers with all these different crossovers (and using many others that had all sorts of their own time-domain distortions).
Thank you for your input. I am glad you get to work in studios so much. There are not enough people with that background contributing to high-end home audio reproduction. I hope my information is of help.
Best regards,
Roy Johnson
Founder and Designer
Green Mountain Audio
greenmountainaudio@adelphia.net
05-09-05
So by "phase coherent" you really mean that a firs ... golix@
05-09-05
Step function tests seem to show all of this very well. ster ... Skrivis
05-09-05
I will chime in here; roy is correct as usual. it is not pos ... Karls
05-09-05
A previous poster has made the statement that using a 1st or ... Seandtaylor99
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