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RE: Interesting post of John Broskie on flat phase speakers.

Posted by tomservo (M) on June 30, 2025 at 10:49:39

In Reply to: Interesting post of John Broskie on flat phase speakers. posted by cellailuca on June 29, 2025 at 04:04:00:

I believe it was the late Dick Heyser that was the first person to figure out a way to measure loudspeaker acoustic phase and described it as if the loudspeaker driver was moving forward and back in it's physical location according to it's acoustic phase response.

It is one thing to say it matters or that preserving the input waveshape matters but this must be seen in the light of the other things that also matter, for example what reaches your ears is the vector summation of the arrivals of the different drivers and their acoustic distances.

How we hear in 3 dimensions in space with only two inputs took a long time to figure out while hifi is about selling product, so while more is known about the how, some of those details do not sell product.

While the write up is limited to the normal named crossover types, it is possible to make a higher order crossover without the phase shift that imposes the group delay or separation in time of the various frequencies.

Also, the larger the speaker system is, the more drivers it usually has, the more different arrival times effect the sound in the negative.

In the 80's I used to build electrostatic loudspeakers for my living room but it was "repairing" my bosses esl-63's showed me that we also hear aspects of how a loudspeaker radiates and this has a profound effect on the speakers ability to disappear in the phantom image ...or stand out as part of the sound at the left and right.

Those esl63 speakers were a full range speaker that radiated as if it was a single point in space (located somewhere just behind the speaker) and made a very strong phantom image and stood out as the source much less than anything i had heard.
It took years to figure out how to make a full range horn that also did this single source radiation but it was possible to do and the difference in sound quality launched the speaker company i still design for and the basis of most of our loudspeakers, even the studio monitors.
The first successful passive filter full range horn was the SH-50.

This is the first one I made about 21 years ago now, a living-room measurement of that one shown.
As a single source in time and space without lobes and nulls, can reproduce a square wave over several octaves. That's a 4th order high pass on the compression driver fwiw

That Synergy horn speaker and the difference in subjective sound and the ones that followed launched the company and are what's in Imax and Emagine theaters, many stadiums and many larger shows in mouse land Orlando and a number of recording studio's all based on side by side demo's.
Tom

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