Speaker placement options in an asymmetric room

[soerenssen]

I'm planning to place a 83" TV and a KEF Reference based HT system in a relatively small room, but I'm not sure if it's a good idea, considering the space/distance recommendations from KEF:

https://www.audiosciencereview.com/forum/index.php?attachments/livingroom-png.359682/

The room at the listening position becomes narrower, so I am considering the following options:
- Center the couch and shift the TV / LCR speakers to the left (centered to the middle position of the 3-seater couch): this will decrease the distance of the left speaker from the side wall to 50-60cm. I can compensate this by placing the L/R speakers closer (2 - 2.2m) to each other (the TV has a width of 1.83m).
- Center the TV on the short wall and have an even speaker distance from both side walls: this would bring the couch too close to the balcony doors and I would lose the simmetry between the right surround speakers. I'm also concerned about that wall protrusion marked with the orange arrow.

What do you think about the above arrangements? Is it worth messing around with placement and acoustic treatments or would it be too much headache and I should look for another room?
Thank you for you help in advance!

 

[er|κzvio1in]

Symmetry can be fixed by (digital) delays and gain optimisation. You have a center speaker so phantom center is only relevant when listening to stereo without the center, is that going to be the case?

Then the next subject is stereo image: you want the speakers as wide as the distance to the LP, so looking at your drawing, you should move the couch forward.

Then the next subject is equal response from both speakers: if you place the speakers symmetrical wrt the room, them excite the same modes and SBIR will be identical. If you place one closer to the wall than the other, frequencies of side wall SBIR peaks and dips will shift causing a mismatch between L & R, which isn't necessarily a bad thing because they might even out eachother and SBIR from floor, ceiling and front wall will remain the same. You can put the distances in an online calculator which will show you precisely what's going to happen.


Then there's room boundary gain in the bass response dependant on distance to surfaces, those can be corrected using DSP.

 

[soerenssen]

Thanks! Yes, it will be used for 2ch music too, without the center (50-50%). I have a feeling that I'll have to prioritize one over the other: if I place the speakers simmetrically (equal distance from the side walls), that might be good for stereo imaging, but the couch will be too close to the glass doors and the right surround will be behind the couch. 99% of the time no one will be sitting on the right seat of the couch though. The idea behind the distance of 2.9m is the multiplier of 1.2x compared to the distance between each other. I noticed that the Reference 3 sounds better from a larger distance, but of course I can push the couch more forward, if that solves some issues.
I would also try not to toe them in to not center / narrow down the focus so much but that distance from the side walls might be too short for these speakers.

If the LR speakers are placed symmetrical wrt the room, will excite the same modes / will SBIR be identical even with that wall protrusion on the right side?
Can you recommend a good calculator to simulate the different scenarios?

 

[er|κzvio1in]

This one for sbir http://tripp.com.au/sbir.htm
This one for modes https://trikustik.at/raummoden-rechner/

 

[soerenssen]

This one for sbir http://tripp.com.au/sbir.htm
This one for modes https://trikustik.at/raummoden-rechner/

Thank you for this! Do you know if there's a simulator where I can modify the room shape? For example, to know what impact to expect from that protruding corner on the right side.

 

[er|κzvio1in]

Just make multiple calculations of rectangular with the larger and smaller dimensions

 

[Daverz]

I would move the couch up to form a more equilateral arrangement, or even a little closer.

 

[soerenssen]

Thank you for the ideas!
I'll try to put in multiple room sizes into the calculator and see, my only concern really is that wall protrusion, especially if I don't toe them in.
If I pull the couch closer to the front wall for an 1:1:1 triangle (currently it's 1.2:1:1), it would be in line with that corner. My latest idea is to use only the middle and right seat of the sofa, centered to the front wall (so I would move it slightly closer to the left wall). That way I could use the full width of that 3.8m wide section of the room and the KEFs would have more room to breathe, plus they would be at equal distance from the side walls. The wall protrusion on the right will probably have to be treated on both sides.

 

[Pareto Pragmatic]

I would move the couch up to form a more equilateral arrangement, or even a little closer.

Agreed. Taking that protrusion out of the equation as much as possible is the way to go, if possible.

Another option is to put something on the other wall that will mirror that protrusion, to get more balanced first reflections. A bookcase? Similar dimensions placed symmetrically will work. But you MIGHT be able to get away with a bookshelf placed against the wall, so the side faces the speakers. If you want to try that, you might need it a bit more forward to balance things out.

An acoustic panel to do the work in that spot, that could also work but would require some experimentation for placement.

Another option is to cross the speakers over SLIGHTLY in front of the seating area, not right at the listener. That will reduce sidewall reflections, and so less sound from the right channel will be cut out by that protruding corner.

You have two main choices: make things symmetrical in the room, or more so, or place things asymmetrically to compensate. The second approach, in my experience, takes way more trial and error but can work well. When I had to use this method, it involved a lot of small movements towards and away from walls, and a lot of changes of toe, slight changes each time. And I just used a recording with a solid center as I worked the options. Once I had an idea or two, then I measured.

One last option. Let the AVR take care of everything, and have a chair you can slide into place just forward of the couch for "serious" 2/2.1/2.2 channel listening.

Good luck!

 

[soerenssen]

Something like this?
- equal LR distance from the side walls
- bookshelf added next to the couch to balance the wall protrusion on the other side
- shared MLP sweet spot marked with green
- some initial treatment ideas: bass traps marked with yellow, heavy acoustic curtains to separate the kitchen and tame echo, thick rug to be added, absorbers to be added to the side walls and to the ceiling to treat 1st reflection points

 

[soerenssen]

I could also close that right front wall section completely with a sliding door (to hide the AVR and other components there). Would the remaining 3.20m width be too tight?