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Pin point imaging isn't for everyone

A subject my posts touch on often is whether pin point imaging is desirable, or natural. While thinking about wide-baffle speakers in another thread I came across this quote, courtesy of Troels Graveson’s DIY speaker site. He quotes famous speaker designer Roy Allison:

I had emphasized dispersion in order to re-create as best as I could the performance-hall ambiance. I don’t want to put up with a sweet spot, and I’d rather have a less dramatically precise imaging with a close simulation of what you hear in a concert hall in terms of envelopment. For that, you need reverberant energy broadcast at very wide angles from the loudspeaker, so the bulk of energy has to do multiple reflections before reaching your ear. I think pin-point imaging has to do with synthetically generated music, not acoustic music - except perhaps for a solo instrument or a solo voice, where you might want fairly sharp localization. For envelopment, you need widespread energy generation.


You can read Troel’s entire post here:

http://www.troelsgravesen.dk/Acapella_WB.htm

This goes, kind of, with my points before, that you can tweak the frequency response of a speaker, and sometimes cables, to get better imaging, but you are going significantly far from neutral to do so. Older Wilson’s were famous, and had a convenient dip around 2.4 kHz.
erik_squires
erik_squires OP
16,051 posts
 
Duke:
That's very interesting! :) I'll have to cogitate on this for a bit. :)


Thanks so much for the detailed background information.

Best,
Erik
audiokinesis
2,737 posts
 
Erik, that primary 2 kHz comb-filter crosstalk notch is something recording engineers have to be aware of. When listening nearfield to mixing monitors in a fairly dead room, the notch is not significantly filled in by the reverberant field, so the engineers need to take it into account. Fortunately it is NOT some great mystery, the professionals all know about it, and in fact often use it to precisely locate the exact center of the sweet spot!!  

Duke
erik_squires OP
16,051 posts
 
Duke,

I'm a little curious about when they were aware of it though.

Having had a HT system with and without a center, the benefit of the center was much better than I had expected. I wonder if that's because the HT system at the time didn't do more than a simple split of the center signal?

Best,
E
erik_squires OP
16,051 posts
 
I'm also thinking of early sympohonic recordings which used the 3 microphone approach, which were down mixed to 2 channel stereo.
audiokinesis
2,737 posts
 
"I’m a little curious about when they were aware of it though."

My recollection is that the other listeners didn’t confirm that they were aware of the sounds off to the sides being not as loud as they were used to. So I don’t think it was obvious. Must admit I did not notice it, but the guy who did is extremely observant and I would trust his ears more than my own.

"Having had a HT system with and without a center, the benefit of the center was much better than I had expected."

I’ve gotten mixed feedback on center channels.

I have several customers who started out with center channel speakers in their home theater systems, then they bought a pair of my controlled-pattern, strongly-toed-in speakers, and felt the sound quality (using phantom center mode) was better than when using the center channel, so they sold their center channel speakers. I presume this was because the center channel speaker did not sound as good as - and/or did not blend well with - the main speakers, and also because in this case the phantom center image remained fairly well centered even for off-centerline listeners. (These were not cheap center channel speakers being unseated - they cost more than one of my main speakers).

So IF the center channel speaker sounds as good as the left and right speakers, or close enough, it is probably a qualitative improvement. (As an aside, I have yet to hear a conventional sideways MTM speaker that I really enjoyed listening to.) But if the left and right speakers sound better and produce a solid center image from all the seats in the audience area, then adding a center channel speaker may not be a net improvement, with this exception:

IF there are listeners with a hearing imbalance (one ear hears better than the other), THEN a dedicated center channel speaker is needed to anchor the dialogue onscreen.

Over in the audio-only realm, one of my colleagues was using an extremely high quality trinaural processor to derive a center channel signal, and his center channel speaker was identical to his left and right speakers. He has since gone back to conventional stereo using speakers that pay a lot of attention to room interaction, in part because he finds the soundstage depth and sense of detachment from the speakers better with the stereo configuration, in this case at least.

So I think I appreciate the arguments for using a center channel and they are very compelling, but ime two-channel can, under some conditions, compete, with this caveat: Two channels cannot provide a reliable, solid center image for listeners with a significant hearing imbalance.

I have toyed with the idea of doing a somewhat unorthodox high-end center-channel speaker.  Probably not a good idea... unorthodox is a hard enough sell in the two-channel world. 

Duke
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