A Visit with Bob Carver and His Amazing Line Source Speakers

[Sal1950]

Not very much, should do it again now that I have a better ADC.

View attachment 56613

You are about to participate in a great adventure.
You are about to experience the awe and mystery which reaches from the inner mind to the outer limits. LOL

 

[JR4321]

I need to hook mine back up and try it out. I remember it was interesting, but I obviously didn't keep it in the system.

Just tried it out. I haven't used this in 5years or more. I've had Dirac software for 4 years, now, so the C9 isn't as fun by comparison.

It would still be interesting to understand what the C9 does, though, just to get a better feel for the phase and frequency plots we see.

 

[carlosmante]

I asked why Bob had gone back to tubes he said he started with tubes but thought they were dying in 1970s and started to build his Phase Linear amplifiers at high power ratings. But now that tubes are back, he likes to work on them so here we are.

Also, the speaker drivers are run in a way to cancel crosstalk between the two ears. That is, the left and right drivers inside each line source are run through a delay that is proportional to the distance between our ears in sound speed (around 800 milliseconds).

An estimate of the distance traveled by sound in 800 milliseconds is approximately 274.4 m . I guess the distance between ears in most humans is equivalent a 0.8 milliseconds at sound speed .

 

[MRC01]

An estimate of the distance traveled by sound in 800 milliseconds is approximately 274.4 m . I guess the distance between ears in most humans is equivalent a 0.8 milliseconds at sound speed .

a.k.a. 800 microseconds
But I think the maximum interaural delay is shorter. If the ears are 6.5" apart it would be about 500 microseconds at room temperature (speed of sound depends on temperature), or about half a millisecond. I believe the commonly used value based on measurements & population studies is 660 microseconds, plus or minus depending on the individual. Of course, if the sound is directly in front of you, equidistant to the ears, the interaural delay is zero. 660 microsecs is the max for a sound that is 90* to your R or L.

 

[davidc]

a.k.a. 800 microseconds
But I think the maximum interaural delay is shorter. If the ears are 6.5" apart it would be about 500 microseconds at room temperature (speed of sound depends on temperature), or about half a millisecond. I believe the commonly used value based on measurements & population studies is 660 microseconds, plus or minus depending on the individual. Of course, if the sound is directly in front of you, equidistant to the ears, the interaural delay is zero. 660 microsecs is the max for a sound that is 90* to your R or L.

I do not think it is the same thing at all. The patent describes a channel cross-feed while this is a delay inserted between the inner and outer arrays of midrange drivers in each speaker. This will have some effect on what the listener hears but the justification is, imho, simplistic and has nothing to do with head dimensions but, perhaps, more with the dimensions of the speakers themselves.

The delay between the ears at the head is equal to the thickness of the head (let's say .8ms for a big head) but only if the source(s) are entirely lateral and is zero if the source is directly in front. Normal stereo speakers are somewhere in-between and no single delay can fit all speaker distances and angles. Besides, with his laterally-opposed midranges, most of the energy from them will be dominated by reflected energy and the treble drivers (and, to a lesser extent, the inner midranges) will dominate the direct radiation. However, for such treble, localization relies more on intensity (and HRTF) than on timing. I did sit through Carver's entire presentation in NYC (with a little discomfort).

Not sure how much it matters, but I remember Bob saying that the interaural crosstalk is the distance from one ear to the other, but across the face, not through the head. This would make it longer...

 

[witchdoctor]

So glad I found this old thread in the archives. My first processor was a Sunfire Theater Grand 3 and if Atmos didn't come along it would still be my reference today. I also bought an old Carver AV505 amp that uses a circuit that was originally designed for the Lightstar amp, WOW! It really opens up a soundstage from wall to wall and floor to ceiling when I paired it with my JBL 230's. If you can find Carver or Sunfire gear at a good price you will be surprised (shocked) at the value. I want to try one of his new tube amps next.