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[Ivan Beaver]

In general amplitude errors as small as a fraction of a dB in the sensitive midrange can be audible especially for short term A/B tests.

It's good that they preferred the "as designed" mode....

JR

I have done other side by side tests with "identical" speakers.

Depending  on the track that was played-people would prefer one over the other.  Play a different track and get a different result.

At least the people agreed.

Yes, I agree that under controlled conditions, even a few tenths of a dB can make an audible difference.

Everywhere from the pick on the string, to the sound of the rosin on a box, to the spit in the voice.

What is truly accurate is hard to say.

[drew gandy]

Nice article & video Merlijn (like all your work).

I have also been doing a little work on this subject.

I posted plans for a speaker I built on Soundforums.net https://soundforums.net/threads/12075-60-Degree-DIY-Mid-Hi

It has an almost perfect impulse response. The amplitude and phase response is almost perfectly flat from about 200Hz up. It will produce a reasonable looking square wave from about 100Hz, both on and off axis …. And it goes LOUD

Peter,
Your measurements of your speakers look incredible and I'm impressed with what you've come up with.  You say that it maintains a good looking square wave on AND off axis.  Can you elaborate on how much variation there is when going off axis vertically?  I would assume it varies more with frequency when at the extremes of dispersion than it does on axis. 

[Peter Morris]

Peter,
Your measurements of your speakers look incredible and I'm impressed with what you've come up with.  You say that it maintains a good looking square wave on AND off axis.  Can you elaborate on how much variation there is when going off axis vertically?  I would assume it varies more with frequency when at the extremes of dispersion than it does on axis.

The vertical axis falls apart the quickest.  Once you start to come off axis more than about 15 -20 degrees the frequency response becomes too uneven ... but within reasonable limits a square can be maintained. 

Here are some examples - I think they are around 400Hz

top picture off axis - horizontal

bottom picture off axis - vertical

[Merlijn van Veen]

Hi Ivan, all
The thing is, listening with headphones to an all pass filter or addition of a simple high pass and low pass filter electronically which acts like an all pass filter, these produce a change in the time or Z domain and nothing else.   In the hifi world, this test was used to argue you can’t really hear crossover phase shift  or more correctly, it is only detectable / audible under some conditions, with some kinds of music.

Best Regards
Tom

Hi Tom,

Forgive my ignorance but I fail to see how physical displacement between drivers introducing phase OFFSET, affects the audibility of phase SHIFT or the D/R ratio of different coverage patterns for the matter?

The HPF/LPF examples in my video were only there to prove that the plugins actually do something for those wondering.

Sincerely and wi all due respect,

Merlijn


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[Ivan Beaver]

Hi Tom,

Forgive my ignorance but I fail to see how physical displacement between drivers introducing phase OFFSET, affects the audibility of phase SHIFT or the D/R ratio of different coverage patterns for the matter?

The HPF/LPF examples in my video were only there to prove that the plugins actually do something for those wondering.

Sincerely and wi all due respect,

Merlijn


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The offset drivers will cause a different phase response at different seats. 

This is due to the fact that the arrival distance from each driver to the listener will be different at different seats.

With a single source, the distance will remain the same at different seats.

[Merlijn van Veen]

The offset drivers will cause a different phase response at different seats. 

This is due to the fact that the arrival distance from each driver to the listener will be different at different seats.

With a single source, the distance will remain the same at different seats.

Yes but AFAIK that's the average compound phase shift produced, by 2 or more drivers, other speakers, reflections, the acoustic source, etc...

It sympathizes with the strongest contributing signal, be it direct or indirect.

I chose my demo very carefully and intended to demonstrate how hard it is to perceive the phase shift by inserting e.g. an all-pass filter upstream.

This doesn't affect the inherent interaction by design between multiple drivers in an (a)symmetric n-way speaker, co-entrant or coaxial.

[Tom Danley]

Yes but AFAIK that's the average compound phase shift produced, by 2 or more drivers, other speakers, reflections, the acoustic source, etc...

It sympathizes with the strongest contributing signal, be it direct or indirect.

I chose my demo very carefully and intended to demonstrate how hard it is to perceive the phase shift by inserting e.g. an all-pass filter upstream.

This doesn't affect the inherent interaction by design between multiple drivers in an (a)symmetric n-way speaker, co-entrant or coaxial.

Hi Merljin
What I was trying to get at was that the demo using an all pass filter or summing a high pass and low pass crossover electrically which also produces an “all pass” phase response is valid for the case where the sources combine coherently into one new signal, like adding two signals through resistors. 
Two acoustic sources can add coherently / unilaterally as well BUT only when they are close together acoustically like close coupled subwoofers (at a spacing less than about ¼ wl apart at the highest frequency of concern) but more often they are farther apart and radiate as independent sources and the result depends on location as they are producing an interference pattern ( as shown by a series of lobes and nulls in the polar pattern).
This condition is often referred to as constructive and destructive interference and is not unilateral or coherent addition.  The issue is that the pattern of lobes and nulls depends on the acoustic spacing of the sources and often lobes are produced in directions which are harmful or exacerbate the room acoustic problems.

In that case, it would be possible to have two loudspeakers with essentially the same magnitude and phase response (on axis) , one producing an interference pattern and one not,  but when used in a room the two might sound pretty different as what one hears is a combination of direct and reflected or late sound and in a large venue like a stadium, the late sound can destroy or greatly limit the articulation and intelligibility of voices.

Also the complex interference pattern if present is very audible if the wind blows and in that the spectral balance changes with position and distance and usually limits the usable working distance of that system.  This is very audible especially in large scale sound as one can hear the difference (absence of these effects) in those links of several large stadiums.

We used to do a lot of generation loss recordings to zero in on what we were doing at work with the idea being the more generations a loudspeaker could go through and still be listenable, the more faithful it was to music or voice.  Using headphones to listen and a good measurement mic to sample the sound by passes your ear / brain system that seeks information and rejects problems but does so without ones awareness.    With a good mic and headphones, one can hear the loudspeakers warts MUCH more clearly and while it doesn’t tell you what to fix or what’s wrong, it can be an arrow point in that direction. 
Even a good loudspeaker will sound bad after just a few generations; they are by far the weakest link in the reproduction chain.   
What you might want to try is to take your “all pass” test and see how many generations that takes before it is obvious as I have measured loudspeakers that had a thousand or more degrees of phase shift from high to low.
Hope that helps, i probably could have explained it better.
Best Regards,
Tom Danley

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