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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
audiokinesis
2,737 posts
 
Mijostyn wrote:

"Sure Duke but I think there is one caveat. You don’t want reflected energy off the front wall coming right back at you."

You are absolutely correct!!

"I wish I could draw a picture here but essentially you want the reflection to take the long way around the room. "
YESSS!!!

"So with a properly toed in dipole the rear sound would head towards the front wall angled towards the side wall. Then it would bounce off the side wall and head towards the rear wall to your side around you."

That’s what I do, whether it be a dipole or one of my quasi-bipolar horns. With my current generation of quasi-bipolar horns, the "backwave" energy is angled up towards the ceiling, further increasing the reflection path length, and allowing good results even when the speakers are quite close to the front and/or side wall.

"This gives you that late reflection from around the room that makes you think the room is bigger."

Right on!! The reflections need to come from all around, not just from the same general direction as the main speakers (which is actually the worst possible direction). And once you have the long time delays from these long path lengths plus the reflections coming from all around, the ear/brain system is really good at picking out the "hall ambience" reflections on the recording.

(Some people mistakenly think this is just a room effect, but it cannot be because how can a modest home listening room sound like it is the size of a concert hall? It must be that the concert hall ambience on the recording has been unmasked, rather than that the small room’s signature has been enhanced.)

"If sound heads toward the center of the front wall and bounces back right at you it really confuses the image just like a blurry photograph. It also diminishes the sensation of a 3rd dimension. I place acoustic tile on the front wall to prevent this reflection towards the center. It only works for frequencies above 250 Hz but that is enough to do the job."

Now you are teaching me something I had not thought of! What you describe makes sense, and I will give it a try next chance I get. THANK YOU!!

Are your acoustic tiles absorption or diffusion?

Duke
learned something new today - THANK YOU Mijostyn!
mijostyn's avatar
mijostyn
8,570 posts
 
Go figure. They are absorption. These are the ones I use. Dirt cheap.
https://www.parts-express.com/sonic-barrier-fwp122-studio-acoustic-foam-wedge-panel-12-x-12-x-2-black-12-pack--260-547
Remember I have Acoustat 2+2s 8 feet tall and twenty inches wide. I put a single vertical row of seven tiles alternating the pattern. They are placed at the deflection point on the wall. The easiest way that I know of to find it is stand right up against the back of the speaker right in the middle. Have someone move a mirror back and forth horizontally across the wall slowly and have them stop when the reflection is centered on the listening position. Mark that point on the wall. That is the deflection point and your tile pattern should be centered there. Height and width are up to you and depends on your speaker's dispersion. 
I first tried double sided carpet tape to stick the tiles on the wall. The tape would not stick to the foam. Next I put a drop of viscous cyanoacrylate glue in each corner and right in the middle, sprayed the wall with accelerator and slapped the tile to the wall. Worked great! I had marked out the wall with pencil and a 4 foot level so I knew where each tile would go. If you ever want to take the tile down the residue will sand right off.

Mike
mijostyn's avatar
mijostyn
8,570 posts
 
Oh, you are most welcome:)

Mike
erik_squires OP
16,051 posts
 
Hi Everyone,
Lots of very interesting reading going on here and in the related thread. I really want to thank everyone for listening, participating and letting me know your own personal experiences, especially when they aren't like mine!

Also to Tom for reminding me of my own advice!!

I've learned a lot, and it will take me a while to digest it all. :)

I still think Neo6 is pretty cool, as is a center channel in HT, but I also don't think they are make/break items for systems. I keep trying to convince myself to go back to HT and listening to my 2 channel I can't baby, I just can't.


Thanks again, and look forward to even more contributions from all of you.

Best,

Erik
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