@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
|
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
|
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
|
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
|
I'm also thinking of early sympohonic recordings which used the 3 microphone approach, which were down mixed to 2 channel stereo.
|
"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
|
Instruments are always louder at the sides than in the center. @erik_squires I’ve listened with attention regarding what you posted... for over two days now AND: I am not hearing any of this across a wide range of randomly chosen as well as Roon Radio queued up tracks. No issues whatsoever. Two albums stood out in this evaluation. Calle 13’s ~reggaeton~ "Residente o Visitante" and the OST from "Slumdog Millionaire" I mention the above two albums because each contains copious amounts of musical information on the Left, Right and Center with strong volume levels across. All of my listening was 2Ch PCM Native. |
@audiokinesis Duke, thank you so much for your detailed posts. Very helpful! |
You bet Duke. 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. Horns can be made to do almost the same thing by controlling their directivity. It seems harder to do with standard dynamic drivers. Their directivity changes continuously with frequency getting narrower as the frequency increases. Dispersion is not uniform and I would think this would cause problems. |
@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 |
Sure Duke but I think there is one caveat. You don't want reflected energy off the front wall coming right back at you. I wish I could draw a picture here but essentially you want the reflection to take the long way around the room. 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. This gives you that late reflection from around the room that makes you think the room is bigger. 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. This is the only place I use room treatment.
|
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! |
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 |
Oh, you are most welcome:)
Mike |
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
|
