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We are having a house built and chose a new house with a big great room to be the single room for both HT and 2ch audio systems. I've done most of the work figuring out where to place the speakers for a 7.2.4 Atmos system. During this learning period I have learned about standing waves and nulls. From the looks of where the MLP will be there is a possibility that the MLP could be in a bad null. In my old house bpape helped me tremendously. I made a bunch of DIY treatments/bass traps.

At this point my biggest concern is will the MLP end up in a null. I can't move the subs at all. I will tune the front speakers a bit for music and hold off on installing the ceiling speakers which will be NHT superzero's on brackets. My only initial option will be moving the seating up to a foot in either direction. The other option is use the treatments made for the old house. There will be 88 inch tall corner traps shown on the right in the drawing, I have a total of 4 I'm not sure if I can place 2 of them. I also have three 4ft x 23in x 6in bass traps that can be installed on the wall centered above the A/V cabinet which is nearly 12 ft wide. I also have three 30.5in x 23in x 4 in treatments made to go inside a wind directly behind the seating at the old house. Two will go on top of the the uppers on each side of the the stove hood (not shown) the 3rd centered on the upper next to the fridg. I also have two 4ft x 2ft x 2in cloud treatments that will be mounted on the ceiling about half way from the system and MLP. All of these made with Owens Corning 703 product. Having all that product in the room can only help. I just hope it's not going to be a disaster because of nearly incalculable standing waves.


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Even though your verbal description is rather complete, I would love to know more. Your question is reasonable and cogent and the mode response potentially can be predicted. contact us at: Jerry Steckling jsxaudio.com.
 

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I had a similar problem in my dedicated home theater which has similar dimensions. In my case the screen is about 6 feet forward of the front wall due to a false wall that screens off electrical equipment, which makes the best seating position for viewing right in the center of the room. Unfortunately at that position there is a terrible bass null. I spent many hours trying different subwoofer placements and settings, but nothing I tried overcame the laws of physics. In the end I had to move the seating towards the rear of the room and compromise on the viewing experience. I also added a third sub placed directly behind the seating, which helped a little.

Looking at your situation I would suggest moving the seating closer to the screen and placing another sub behind or to the side of the seating. That would also give you a bit more circulation space between the island and the seating.
 

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Atmos is the worst sounding immersive format for music. Auro 3-D is MASSIVELY better-sounding for music up-channeling. In fact, i would choose Auro-3D over stereo listening every day. I would rate Atmos at 3/10 for sound quality of the upconverter, Dolby Surround in this case. DTS:X (DTS Neural:X when the source is stereo) rates about a 5/10 for listening to stereo music. Auro-3D playing stereo music is better-sounding by far. Additionally, Atmos causes a loss of separation from left-high to right-high because the speakers are not far enough apart in most home theater rooms. Auro-3D speaker placement works best for all 3 immersive formats. Auro-3D places front height speakers directly above the front left and right speakers and side-surround height speakers directly above the side-surround speakers, and rear height speakers directly above the rear surround speakers. They prefer you use sealed or ported box speakers aimed towards the seating area and NOT speakers aimed directly down from the ceiling--that is the WORST SOUNDING ORIENTATION OF SPEAKERS POSSIBLE. NOTHING is worse for sound quality in a home theater than speakers firing straight down from the ceiling. In addition,

Auro-3D decoding supports a "top" channel, directly overhead of the main seat. This additional channel creates a much more immersive listening experience. In fact, it is SO immersive that a 7.1.4 Dolby TrueHD/Atmos played back and processed by Auro-3D sounds BETTER with the Auro-3D processing. And ditto for playing DTS:X tracks back with Auro-3D processing instead of DTS:X processing. And with stereo music, the sound quality with Auro-3D processing is SO GOOD, I stopped listening to stereo music. Music processed with Dolby Surround is WRETCHED sounding. DTS Neural:X processing of stereo music is better than Dolby Surround, but not by much. Dolby Surround is the worst sounding audio processing codec since the original Dolby Surround that was also horrific when applied to stereo music. Not having Auro-3D decoding in a good system is a BIG mistake. You never have to use a movie with an Auro-3D soundtrack (many are for sale on Blu-ray discs sold in Europe, but Dolby is using their swagger to keep Auro-3D out of the US market as much as possible.

Dolby already lost a lawsuit for altering new Atmos soundtracks so that they could not be processed by Auro-3D--cleary a predatory business move. Dolby is so worried about the superiority of Auro-3D that they are trying to stamp out Auro-3D with predatory business practices like disabling Auro-3D processing of Atmos soundtracks and predatory hiring of Auro-3D employees away from Auro-3D. This is a classic case of the big bully trying to squash Auro-3D like a cigarette butt on the sidewalk.

Not having ANY flexibility with the subwoofers is an unfortunate situation. If your location(s) produce a 60 dB null at 41.5 Hz (random number), there is NOTHING you can do to improve or remove that null. If you try to make 41.5 Hz louder, the additional sound will just be cancelled also. Once there is a deep response dip due to a room mode, the ONLY WAY IT CAN BE FIXED is to MOVE the subwoofer. But the new location may have a deep null at a different frequency. There is likely to be a GOOD subwoofer position within 10 feet of where you THINK there is a good subwoofer position. In placing your subwoofers, you can create literally PERFECT bass response at the main seat if the 2 subs are placed at the front and back of the room, the same distance from the main seat. This assumes that the main seat is in a position that does not have a null... something you have to measure and locate before you begin dealing with the subwoofer locations. With the 2 subs, you essentially create a phantom subwoofer placed AT THE LISTENING SEAT where room nodes can't interfere much unless the seat is right on top of a room mode. Note... room modes exist in 3 dimensions... front-back, left-right, and up-down. This all makes positioning 2 subwoofers and the main seat in just the right positions a long-term project. I have spent 3 months finding the right locations for 1 to 4 subwoofers and the main seat in 3 different rooms... it is just impossible to find the magic spots quickly without measurements made by multiple microphones in multiple locations simultaneously including variations in height, left-right, and front-back. AND software that can turn that data into 3-D room mode maps.
 

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Discussion Starter · #5 · (Edited)
For what it's worth in the rental with a similar style room it sounds pretty good. Also for music I use a McIntosh C2500 pre and a Rogue ST100 power amp, all tube. The improved overall sound is way better than any surround option from my Marantz 7702.

The drawing above is to scale if I place the treatment like I plan it has to help. I'm not sure if you can visualize it because with the exception of the corner trap they are not on the drawing. The bulk of it will be behind and above the system proud of the wall just below the crown. 12ft X 23inch X 6 inch thick that is a lot of OC 703 product. I'm still hopeful it will not be a disaster.
 
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