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RE: Moving Mass Vs. Detail Vs. radiation properties

Posted by tomservo (M) on August 12, 2023 at 08:34:07

In Reply to: Moving Mass Vs. Detail posted by PaulF70 on August 11, 2023 at 18:18:00:

Hi
The quad esl 63's i removed the spark gaps from for my old boss in the late 90's were an inspiration to me and shaped my path at work.

I sat on the floor about 4 feet away from them fro several hours several days in a row just listening. They beat the daylights out of my home made ESL's for the stereo image and a property i had never heard up to that point.

For some recordings, if you just played one speaker and sat close, it sometimes sounded as if the sound was coming from behind the speaker element.. The ESL-63's construct a simple point source of radiation, a synthetic aperture source in radar terms.

ESS speakers do have an HF limit too, it is the parallel capacitance of the elements and the series leakage inductance in the driving transformer.

In the way old days i built a direct drive tube amplifier. Like many speaker projects in the olden days, i got one channel working / measuring well but never finished the other channel, i had a lot of speakers where one was done and the other mostly done..

One big factor once the regular speaker warts are shaved off effects stereo image.
It has been my observation that there is a property you can plainly hear but doesn't show up in measurements at least in a way you can interpret AND is not accurately captured in a loudspeaker generation loss test.

I have been building and measuring speakers, drivers and acoustic sources for a living since the late 80's and speakers are my main interest so i don't say the previous lightly.
In fact i gradually concluded it while doing that stuff, this might be part of what Dick Heyser was looking for

What is that? Ok first remember your perception of "hearing" includes what you see.
See the McGurke effect for an example where what you see even over rides what you hear.
We are talking about something you only hear.

This is a property i have been calling "loudspeaker spatial identity" for lack of a name.
So pretend you have two different types of speakers and you can switch back and forth between them at will, while playing a soft voice (what our brain is most tuned into).

With you eyes closed (or both speakers equally hidden behind spandex etc), it easy to point at each speaker's location BUT with one speaker it's easy to triangulate where it is and guess it's distance while the other is ambiguous in fact if you play a recording that sounds far away (hf rolled off, reverb etc), it sound sounds like it's far away not where it is.

In Mono, where the adventure began, i would probably lean towards the speaker that stood out but in Stereo, those speakers still stand out in the illusion the recording is trying to deliver. The pair with the ambiguous depth or spatial identity can with the right literally recording disappear in the phantom image, your brain chooses the illusion.

This brings us back to the ESL-63 and it's simple point source radiation and it's occasional impression of sound coming from the origin behind it, having much less than average spatial identity.

What it lacked for me was affordability at the time and what i was interested in was "more" output. So was my boss, it took a couple months without the protection spark gaps and his were toast.

Fast forward 30+ years and here is very powerful full range point source 3 way horn that like the 63 also has very little spatial identity, radiates as a single simple source and is very hard to tell how far away it is.

If you have headphones take a listen.

https://www.dropbox.com/s/o541g5odygyx0cz/20170428113035.mts?dl=0

Tom

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