Tannoy DC and phase response. - diyAudio
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Old 13th January 2015, 03:06 PM   #1
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Default Tannoy DC and phase response.

Hi looking at a brochure of Tannoy Precision line speakers i found the graphs attached
Is it true that Tannoy coaxials give a such good phase response ?
is it an important characteristic ?
Thanks a lot for any kind advice, gino
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File Type: jpg precision-range_pdf1.jpg (193.7 KB, 203 views)
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Old 13th January 2015, 03:11 PM   #2
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From the measurements I did on my Tannoy System 800s, their time alignment seems worse than a traditional 2-way box speaker, at least on-axis. The acoustic centre of the HF driver is about 2 inches behind the LF one giving a considerable time delay.

KEF's Uni-Q driver has better time alignment, as they stuck the tweeter on the end of the woofer pole piece.
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Old 13th January 2015, 03:41 PM   #3
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Originally Posted by scopeboy View Post
From the measurements I did on my Tannoy System 800s, their time alignment seems worse than a traditional 2-way box speaker, at least on-axis.
The acoustic centre of the HF driver is about 2 inches behind the LF one giving a considerable time delay.
KEF's Uni-Q driver has better time alignment, as they stuck the tweeter on the end of the woofer pole piece
Hi and thanks for the helpful explanation.
Time alignment is the same as phase response ?
Sorry but i am quite ignorant.
The time alignment i can understand more easily. It is the delay between the drivers. The signal coming from one driver reaches the listener at a different time of the signal coming from the other driver ... this is fine.
Phase response is a very difficult concept for me to understand.
And also i do not know if it impacts sound quality.
But as i have big respect for Tannoy brand, if they show this very good phase response of their speakers i think it must be worth something.
Thanks again, gino
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Old 13th January 2015, 03:48 PM   #4
rayma is offline rayma  United States
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Originally Posted by ginetto61 View Post
Is it true that Tannoy coaxials give a such good phase response ?
These are conceptual drawings, not measurements. It just shows the time delay on a tweeter is reduced by mounting it coaxially.
Also they are mistaken, you want LINEAR phase, which can be a line with a slope, not constant phase.
Linear phase is equivalent to a constant time delay.

Last edited by rayma; 13th January 2015 at 03:51 PM.
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Old 13th January 2015, 03:53 PM   #5
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Originally Posted by rayma View Post
These are conceptual drawings, not measurements. It just shows the time delay on a tweeter is reduced by mounting it coaxially.
Hi and thanks for the replay
I reload the image just to focus better the question
I am mostly interested in the phase response not time alignment
unless they are the same thing of course ... i do not know
Thanks a lot, gino
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File Type: jpg tannoy phase response.jpg (50.9 KB, 176 views)
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Old 13th January 2015, 03:56 PM   #6
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Quote:
Originally Posted by rayma View Post
These are conceptual drawings, not measurements. It just shows the time delay on a tweeter is reduced by mounting it coaxially.
Also they are mistaken, you want LINEAR phase, which can be a line with a slope, not constant phase.
Linear phase is equivalent to a constant time delay.
Hi and thanks a lot for the explanation
I give up. If they make such mistakes even on official brochure it is too confusing for me. I am surprised by the way, in a bad way.
Thanks again, gino
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Old 13th January 2015, 04:05 PM   #7
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Time alignment and phase response are not the same thing but they are closely related.

I think the phase response of a dual concentric driver must be pretty bad unless the crossover was specially designed to straighten it out. Tannoy don't do this, they use quite simple crossovers.

There is no proof that phase is audible, but that doesn't stop many speaker designers believing that linear phase response through the midrange makes a speaker sound better.
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Old 13th January 2015, 04:11 PM   #8
rayma is offline rayma  United States
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Originally Posted by ginetto61 View Post
I am mostly interested in the phase response not time alignment unless they are the same thing of course.
Well, the phase response and time delay are not the same, but they are related. A pure time delay causes a linear phase shift as seen on a graph.
Other aspects of a system can cause other phase shifts, and they add to the pure time delay. Of course, if the drivers are not mounted in a coaxial fashion, the pure time delay will change depending on which driver is operating. This is why coaxial mounting is done, to reduce this problem.
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Old 13th January 2015, 04:21 PM   #9
AndrewT is offline AndrewT  Scotland
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The old DC Tannoy arranged that the phase response from the crossover and the drivers were such that at the crossover frequency the treble was ~3" earlier than the bass.
That ~3" is the distance that the effect source of the treble is behind the effective source of the bass.
i.e. at crossover the two signals are in phase.

I don't know what happened when they changed to the ferrite magnet system.
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Old 13th January 2015, 04:26 PM   #10
AndrewT is offline AndrewT  Scotland
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Originally Posted by scopeboy View Post
...................There is no proof that phase is audible,............
phase error around the crossover frequency is audible.
It's why we get a lobe pointing down to the floor for a "simple" crossover.
LR arranges for the lobe to point forward by getting the phase at crossover correct.

When the drivers' outputs are "in phase" we are left with ensuring that the sources are the same distance from the listener.
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