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Dolby Atmos and planer surrounds

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Posted on July 12, 2014 at 18:56:59
TitaniumTroy
Audiophile

Posts: 626
Location: Mishawaka, Indiana
Joined: October 14, 2006
 In this article it mentions some problems with dipole surrounds, I assume box like sprayers not true planer dipoles. My question is how would one deploy some say MC1/MMGW speakers as to maximize the overhead surround effect?

 

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RE: Dolby Atmos and planer surrounds, posted on July 12, 2014 at 20:11:59
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 it's a good question and I don't have a clue. Maybe someone has experimented?

That being said, dipole surrounds are usually used edge on, the idea being to get a reverberant signal with low interaural cross correlation, and I suspect that's the type of dipole Dolby has in mind. That's great for music, less so for localized surround effects in a movie. So the solution may be as simple as aiming the dipole at the listener and mounting it high up, keeping in mind that the sound will seem to come from the height of the center of the diaphragm (although some subjective image shift can occur owing to reflections).

A full height planar would also present problems since there's no way to elevate the acoustical center significantly. Most height cues occur at higher frequencies though so potentially a quasi-ribbon diaphragm could be segmented to give a single speaker height capability.

 

RE: Dolby Atmos and planer surrounds, posted on July 12, 2014 at 22:08:00
TitaniumTroy
Audiophile

Posts: 626
Location: Mishawaka, Indiana
Joined: October 14, 2006
 I use MG10.1s for surround duty, and they are pointed directly at my ears, tweets in board. They seem to do an excellent job to me, I tried them edge on. Could not get the levels loud enough in that position. As it is they are at max volume level now, and still could use more volume to compete with the 3.6's upfront.

Besides don't a lot of people complain that dipoles are too diffuse anyway. I have used the 10.1's in stereo and compared to regular speakers or the 3.6s they are too diffuse. Anyway aren't our ears really designed for sounds that come the front and sides.

Since surround channel technolgy is dedicated now, starting with Dolby Digital and not matrixed anymore. I thought most people parted ways with the THX dipole diffuse concept in general. Special seating situations not withstanding.

 

RE: Dolby Atmos and planer surrounds, posted on July 12, 2014 at 22:17:10
TitaniumTroy
Audiophile

Posts: 626
Location: Mishawaka, Indiana
Joined: October 14, 2006
 Josh, didn't Telarc Records in their mixing room, use some on wall Magnepans for ambience? I belive they had them, hanging down from the ceiling close to the side walls even with or maybe somewhat forward of the mixing engineer.

 

RE: Dolby Atmos and planer surrounds, posted on July 13, 2014 at 11:06:35
MG-bert
Audiophile

Posts: 141
Location: Maryland
Joined: January 18, 2009
 Josh358 scribed:

"A full height planar would also present problems since there's no way to elevate the acoustical center significantly. Most height cues occur at higher frequencies though so potentially a quasi-ribbon diaphragm could be segmented to give a single speaker height capability."

Do you mean that Planars can't decode height cues? If so I beg to differ - at least my Gunned MMGs can have an instrument coming from the floor and simultaneously another coming from much higher up. I suspect if I lowered my ceiling a bit (it's currently 9 foot high) so the top of the MMG were as close to it as the bottom is to the floor, the height effect would be even better. Chesky's Jazz and Audiophile Test Disk Vol 2 as a nifty test where a shaker is played from floor to 4 feet above the microphone, and my MMGs go from floor to perhaps 2 feet above middle.

MG-bert

 

RE: Dolby Atmos and planer surrounds, posted on July 13, 2014 at 18:29:05
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Nope, not what I meant, although it's understandable that you might think so. As you say, line sources are good at reproducing height cues, if they're in the recording -- basically floor bounce (Satie's theory and it makes perfect sense). Because a full-height dipole has no specific floor bounce of its own, it doesn't override the height cues on the recording. (It does of course bounce off the floor and ceiling, but the acoustical effect is to reflect and extend the line -- nominally to infinity, in practice, it's shaded by absoprtion so maybe 2-1/2 times the physical height of the line -- and the reflections are delayed a bit).

What I'm talking about are the height cues created by a speaker itself rather than the cues in the recording. That is, the pinnae (and to some extent the head and body) reflections comb with the direct sound and the brain is very adept at correlating the combing with source height, doubly so if the head moves vertically. So you hear the sound from a point source speaker coming from the height of the speaker, and a shorter line source, too, e.g., the sound from the MMG's seems to be coming from too low! Which always annoyed me.

 

RE: Dolby Atmos and planer surrounds, posted on July 13, 2014 at 20:18:16
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 I think most of the people who have surrounds are using them for movies, and aiming them at the listener is definitely better for that since it gives you better localization. But if you're trying to emulate a concert hall for music, a point source isn't so good since lower interaural cross correlation is associated with better concert hall ambiance/sound. Basically that's saying that you want sound to seem like it's coming from everywhere, rather than just a specific point -- a very diffuse, randomized sound field.

Of course, that assumes you can get sufficient levels. Once you're back a few rows in the concert hall -- the far field -- more than half of what you're hearing is reverberation, so even for acoustical music the surrounds have to have good SPL capability.

Re your other post, haven't seen that setup. I did see a picture of a very cool surround setup that someone made using electrostatics mounted in the walls. It looked like it was audio oriented. Theatrical surround by convention had the surrounds mounted higher up towards the ceiling.

 

RE: Dolby Atmos and planer surrounds, posted on July 14, 2014 at 10:20:10
MG-bert
Audiophile

Posts: 141
Location: Maryland
Joined: January 18, 2009
 Josh358:

Always learn something from your posts; many thanks!

As far as "So you hear the sound from a point source speaker coming from the height of the speaker, and a shorter line source, too, e.g., the sound from the MMG's seems to be coming from too low! Which always annoyed me." goes, me too! That's why I took the Gunned MMGs, which are designed to sit on the floor in a tilted position, but them up on cinderblocks and shimmed them to be almost vertical (an inch tilt-back seems ideal in my room) so it acts closer to a floor to ceiling line source.

The only lower (in height) speaker I've heard tilted back which DIDN'T sound like the soundstage was in the floor are the JansZens. Their setup in the audition room at DC Capital Audiofest last year had issues, but that aspect of their sound was impressive.

MG-bert

 

RE: Dolby Atmos and planer surrounds, posted on July 14, 2014 at 10:32:32
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 Interesting, I wonder how they did that? (JansZen, that is).

I raised my MMG's up too. Made a big improvement in image height and depth, but the bass goes to hell. Never finished my speaker stand which was to have had a piece in front to fill the gap between the bottom of the speaker and the floor, that might have helped some -- acting like a little wing of sorts. But then again, it could have had negative effects since it would have increased the effective baffle size and you'd also get an interference pattern between the speaker and its floor reflection where 2x the floor gap was greater than the wavelength in question.

 

RE: Dolby Atmos and planer surrounds, posted on July 14, 2014 at 10:50:33
JBen
Audiophile

Posts: 3082
Location: South FL
Joined: May 18, 2008
Contributor
  Since: July 26, 2010
 Josh, you just reminded me of something that I had wanted to mention long ago. For the benefit of the ones that do raise their Maggies, pluging that whole, the way that you thought, IS the right thing to do. Bass will return in most cases.

Not plugging it was a mistake I made for a few weeks long ago when I first raised my MMG in a final manner. This had not shown up as the cause of bass loss in earlier tests because other factors hid it from me. So, at first I blamed the wrong factor.

Folks, if you use stands that raise the Maggies, cover that space down to the floor. You can test with cheap pieces of wood. Also, in many cases, placing absorption material on the back of this cover will be of further help. Let the baffle become larger...bass may not be the only thing that will improve (but that's a longer story).

 

RE: Dolby Atmos and planer surrounds, posted on July 14, 2014 at 11:05:27
MG-bert
Audiophile

Posts: 141
Location: Maryland
Joined: January 18, 2009
 Josh358:

As you know, the Gunned MMG has a lower panel which I suppose acts a bit like a wing. Could try extending the "wing" all the way to the floor, but I use the holes in the cinder blocks as a pass through for cables to and from the amplifiers, which sit on concrete pavers on the floor in front of the MMGs. In my room, the MMGs have a bump around 58 Hz, so my 1/3 octave EQ is set to reduce the FR at 50 and 63 Hz, keeping 40 Hz flat. As a result, my response is flat down to 50Hz, and down 3-5 dB at 45 Hz. Not bad indeed.

MG-bert

 

RE: Dolby Atmos and planer surrounds, posted on July 15, 2014 at 17:20:26
josh358
Industry Professional

Posts: 12332
Joined: February 9, 2010
 How much space do you have under the baffle? You can get away with a few inches . . .

 

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