How to approach an HT room

[jonnythan]

I might be moving in the near future. The place I'm looking at has a 'living room' that seems very well suited to my frugal HT setup. It's a rectangular, otherwise empty room that I estimate is around 14' x 18' with an 8' ceiling. There is one entrance door near a corner and a couple of windows along the short back wall near the door. The primary seating will be a love seat probably near the center of the room.

I live with my GF and we're both students so we're working on an extreme budget. I know I'll need to do something to this room to get decent sound inside of it. There's a lot of drywall in there. I'm new to room treatments and acoustics, but I have used tools like REW in the past.

Can someone help me out with the real minimum basis that I should try to think about to make this room more appropriate? Should I immediately think about doing something along the back, front, or side walls, or even the ceiling? Should I bother doing some measurements and treating in response to that?

If it matters, I have NHT SuperZeroes and a SuperCenter up front, Polk R15s in the back, and a Dayton HF 12" sealed sub.

 

[Josuah]

As far as the room goes for HT, I'd list the following 3 things as important:

1. Light control. Dark is good.
2. Reflective surfaces and colors. You want any surfaces to minimize reflection from your display and be dark in color.
3. Room treatments. Better sound equals a better experience. (The place to start here is at the first reflection points between your speakers and your seat.)

 

[Norman Varney]

Jonnythan,

1. Room symmetry is important, especially horizontally.
2. Figure out optimum listener location for most linear bass response.
3. Locate the subwoofer to avoid problematic room modes.
4. Locate the the speakers for optimum soundstage.
5. Calibrate system.
6. Adjust toe-in for best image and tonality.
7. Treat all first order reflections with absorption or diffusion down to at least 500 Hz.
8. Add more absorption as needed to control reverberation times in a linear, wideband fashion.

 

[jonnythan]

Thanks for the info Norman, but that's all pretty much stuff I already know.

I'm asking for specifics on how to actually treat the room acoustically. How do I identify reflections? What kind of treatments do I need? How do I figure out where reverberations are and what, specifically, can I do about them?

 

[Norman Varney]

Jonnyhtan,

You can find the first order reflection points by doing the math or, with the help of an assistant holding a mirror flat against the walls, ceiling and floor, mark the points where you see the tweeter from the listening position.

Our metu panels are broadband and customizable to fit in with your decor. Typically, you absorb the LC&R and diffuse the rears. metu CornerTraps are for smoothing out room modes. These treatments will simultaneously reduce reverberation times broadband. If more reduction is needed, more panels can be purchased. Check out the paper suggesting priority phases of purchase. Let me know if you have more questions.

 

[Josuah]

I'm asking for specifics on how to actually treat the room acoustically. How do I identify reflections? What kind of treatments do I need? How do I figure out where reverberations are and what, specifically, can I do about them?

The mirror trick described can be used to find first reflection points. Don't forget there are reflection points on your ceiling and floor as well. But those are less likely to be something you want to do something special about, outside of placing a rug on the floor.

The corners are also a good place to stick large bass traps. So-called corner traps work well for that.

I prefer using absorption for everything, while others don't. You can purchase traps online (for absorption, you want materials like semi-rigid fiberglass or rockwool, and not anything like the small simple or eggshell panels sometimes sold as acoustic treatments) or build your own by purchasing from a local commerical/industrial insulation company.

 

[jonnythan]

That's good general advice, but how do I figure out what I need or what I want? Anyone can toss some sort of panel at the first reflection point, but how do I determine whether that is helping or hurting? Or what it's doing at all?

I mean, I can post a REW graph, but how specifically do I determine what is helpful and what the specific room's problems are?

 

[Norman Varney]

Jonnythan,

Good question. At minimum, you want to attenuate any first order reflections that are within 15 dB of the direct signal down to at least 500Hz. This would mean the treatment needs to be at least 2' wide to cover the wavelength.

Be suspect if the product does not have a data sheet with ASTM noise reduction coefficient results from a NVLAP certified testing facility. All our products are certified.

Coincidentally, check out todays post on my Facebook page. This may answer more questions you may have.

 

[Josuah]

Room EQ Wizard has graphs for decay and frequency response. If you have improved things, the frequency response should flatten out (remove dips and peaks resulting from the room) and the decay should improve (become shorter in time, i.e. reduced echo).