Pin point imaging isn't for everyone

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

@david_ten poses a very interesting question:

"Do differentials in volume guide perception of distance (of the performer) relative to the listening position?."

Volume plays a role, but it is my understanding is that reflections play the primary role in the perception of distance. Two of my kids are amateur musicians and on their recordings they often manipulate the perceived distance of a voice or instrument by adding the appropriate reverberation. When done right, timbre is enhanced as well.

So we have the reflections on the recording, and then we have the reflections of the recording within the listening room.

Unfortunately the speaker/room interaction usually results in "small room signature" cues which tend to be dominant, and which overlay or degrade the soundstage depth that was on the recording.

If the setup does not superimpose a strong "small room signature" atop the the recording we are more likely to hear its inherent soundstage well, including distance of the performers (depth).

At the risk of over-generalizing, early reflections are the ones most responsible for a "small room signature" which (among other things) degrades soundstage depth. And it seems that the ear is able to extract beneficial depth and ambience information present on the recording from relatively late reflections, so apparently late reflections do not convey a dominant "small room signature".

Managing the room reflections well (a complex topic, and something easier said than done) can allow you to readily hear the different soundscapes from one recording to the next, giving you a good excuse to rediscover your music collection, and giving you new appreciation for really good recordings.

Imo, ime, ymmv, etc.

Duke

@erik_squires posted an interesting observation:

"Even with very good imaging I notice the following: Instruments are always louder at the sides than in the center."

Several weeks ago I had the privilege of setting up a set of my speakers in a world-class dedicated home audio room. My speakers were not replacing the excellent speakers already in the system, but the owner was kind enough let me set up my speakers in his system for my own education.

I solicited criticism from those present, because I learn more from my critics than from my fans. One listener noticed that instruments were not as loud at the sides as what he was used to hearing! In other words, he was hearing the exact opposite of what you describe, when using my speakers.

I think the difference was this: My speakers were fairly directional and toed in aggressively, so they were generating a very weak reflection off the nearby side walls. The room owner’s speakers had a much wider radiation pattern and were only toed in a little bit, so they were generating strong sidewall reflections.

I’m not saying this is the whole story on why "instruments always sound louder at the sides than in the center", but it may be part of it.

(I am well aware of the inevitable comb filtering in the phantom center image, which is one of the reasons why I do my final crossover tweaking listening to a mono signal over a single speaker.  Comb filtering of the center vocalist could sucker me into making the 2 kHz region too loud.)

Duke

"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

@david_ten wrote: " Duke, thank you so much for your detailed posts. Very helpful!"

Thank you David, my nerdy tangents aren’t always welcome, very glad to hear you found these helpful!

@mijostyn wrote: "This is a major reason line source dipoles sound the way they do. They minimize reflected energy in a way no other type of speaker can match."

Imo line source dipoles have many things in their favor, and minimizing early reflections is certainly one of them. Imo their backwave energy is also uniquely beneficial.

First off, the backwave of a dipole is spectrally correct, which is a really good start. Then assuming the speakers are fairly far out into the room, the backwave can actually REDUCE the small-room signature I alluded to earlier! Let me explain:

The ear/brain system judges the size of a room by the time delay between the first-arrival sound and the "center of gravity" of the reflections. When we have a significant path-length-induced time delay on the arrival of the backwave energy, the ear/brain system interprets that as "we’re in a pretty big room". So less "small room signature" is super-imposed on the soundstage in the recording! Imo this is an example of "reflections done right".

(The highly counter-intuitive implication here is that MORE reflections [in this case the backwave energy], done "right", actually result in hearing LESS of the room you are in and MORE of the soundscape on the recording!)

Mijostyn again: "Horns can be made to do almost the same thing by controlling their directivity."

Yes! Horns can definitely reduce the amount of energy in the early reflections AND generate a spectrally-correct reverberant field, through uniform pattern control. (Imo gotta use the right kind of horn the right way to avoid audible colorations.)

I really like the liveliness of good horns but probably like the timbral richness and sense of immersion in the recording’s soundscape from a good dipole speaker even more. So my best horn systems have a rear-firing array dedicated to generating a spectrally-correct, relatively late-onset approximation of the backwave of a dipole speaker. There are still things that a good line-source dipole does better, but imo the additional "backwave" energy tightens the race in some areas.

Duke

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!