Loudspeakers feat. cardiodic directivity in the bass region

[Jakob1863]

While Bruno´s Ki´s are the somewhat modern implementation, we should not forget that a manufacturer like Geithain did something similar passively (although being active speakers) in a convincing manner for nearly 20 years, see for example:

http://www.me-geithain.de/index.php/en/studio/products/active-loudspeaker/rl901k

 

[Fitzcaraldo215]

I could be wrong, but I think Martin Logan also attempted that in their Prodigy hybrid electrostat dipole about 15 years ago. They called it Force Forward bass, and it relied on a rear mounted passive bass cone to deliver a cardioid-like pattern in conjunction with the front bass driver. They have since abandoned the idea largely in favor of powered internal forward/downward facing sealed box woofers with no rear or passive cones.

They were the unpreferred bad boys of some initial Harman tests. But, I have been happy with mine for a long time.

 

[Jakob1863]

<snip>

They were the unpreferred bad boys of some initial Harman tests. But, I have been happy with mine for a long time.

That illustrate one often underestimated thing about those listening tests. Those were done in a specific environment - means afair monophonic reproduction and with the shuffler positioning the speakers at the same place - which might not have been the optimal placement for each loudspeaker.

In addition i´d doubt that the special virtues that listeners like in bigger panel speakers and especially electrostats could shine in monophonic reproduction, although Floyd Toole emphasizes that in their experiments it was found out that monophonic was superior over stereophonic two chanel reproduction for evaluation purposes.

Not to forget intersubject differences/preferences.....

 

[Cosmik]

...although Floyd Toole emphasizes that in their experiments it was found out that monophonic was superior over stereophonic two chanel reproduction for evaluation purposes.

About as fine an example of pseudoscience you could find (Toole, not you Jakob1863). By claiming that mono works better than stereo in evaluating a speaker, he has already implied that he is merely using listening tests to confirm his theory. How can he know that mono works better than stereo unless he already 'knows' what he is looking for?

I can see where the temptation comes from: in his experiments he finds that stereo correlates with the mono preferences, but slightly less reliably, perhaps. He may well be right, but the fact remains that most listening is done in stereo, and he doesn't know that his theory is 'continuous'. Spin-o-Rama may seem to be the primary determinant in listener preferences with every example he has tried, but there may be another factor: good Spin-o-Rama combined with superior phase and timing may be a step change better - but only significantly audible in stereo. By abandoning stereo evaluation, he cuts himself off from ever finding this out and can carry on confirming his theory that passive crossovers are adequate and only the Spin-o-Rama matters. Maybe he cites other people's experiments that say that phase is not important - but these experiments may well have been conducted with systems that never achieved accurate phase & timing (like comparing different types of high level distortion, but never hearing a low distortion example) and didn't have good Spin-o-Rama characteristics to boot.

 

[Thomas savage]

About as fine an example of pseudoscience you could find (Toole, not you Jakob1863). By claiming that mono works better than stereo in evaluating a speaker, he has already implied that he is merely using listening tests to confirm his theory. How can he know that mono works better than stereo unless he already 'knows' what he is looking for?

I can see where the temptation comes from: in his experiments he finds that stereo correlates with the mono preferences, but slightly less reliably, perhaps. He may well be right, but the fact remains that most listening is done in stereo, and he doesn't know that his theory is 'continuous'. Spin-o-Rama may seem to be the primary determinant in listener preferences with every example he has tried, but there may be another factor: good Spin-o-Rama combined with superior phase and timing may be a step change better - but only significantly audible in stereo. By abandoning stereo evaluation, he cuts himself off from ever finding this out and can carry on confirming his theory that passive crossovers are adequate and only the Spin-o-Rama matters. Maybe he cites other people's experiments that say that phase is not important - but these experiments may well have been conducted with systems that never achieved accurate phase & timing (like comparing different types of high level distortion, but never hearing a low distortion example) and didn't have good Spin-o-Rama characteristics to boot.

Blasphemy, burn him...

 

[Blumlein 88]

I do think comparing panels in mono is a perhaps a relative disadvantage vs box speakers. Toole mentions how some spread of directivity gives dimension and size to the sound even in mono. This tracks with my impression of panels in mono. A bit of a dead and spaceless property. The backwave will bounce straightback and still you get little scatter or room filling sound. Now a pair of panels in mono seem much less effected. I believe with angling the backwave bounces off the walls at angles and is more room filling though still less than a good controlled directivity box speaker.

I'll have to go back and see if I can read details of their ML testing. I can understand if you previously proved to yourself mono testing is more accurate and repeatable that becomes your method. However, did they ever compare panels in stereo? If so did they improve their relative standing vs boxes? I also have seen how they said early on they had a near 1.00 correlation with spin testing and listener preference with bookshelf speakers and monitors. With full range speakers the correlation was corrupted somewhat presumably by variable response below the Schroeder frequency.

I don't have quite the concerns that Cosmik does about such testing. Especially as it seems to confirm that flat accurate response is key and not messing that up off axis is the next key. Their research has simply fleshed out the envelope to determine what levels of deviations fit with creating a lesser preference in the population of trained listeners with good hearing. The phase business comes up over and over and over again. Whenever it has been tested it indicates humans are relatively un-hearing of phase at frequencies above 1500 hz. I also don't see much chance of two channel interaction changing that as phase issues that are the same in both channels mean relative phase between channels remains a relative non-issue.