Acoustical Treatments Master Thread - Page 308

Hi Ankur,

Best place to start is ray trace the room. See where things need to be placed. Post that when completed and go from there.

Hi, what exactly do you mean by ray trace?

Assume sound travels like a ray of light or use mirror to locate probable high gain reflection points.

Thanks, along with the side walls, which other surfaces should i consider?

Ceiling, floor, and maybe back wall.

If you have ever shot pool, think of bank shots. Angle of incidence equals angle of reflection.

Jeff

Front wall ...

Yes. I used the "mirror test". It's exactly what you think it would be. Put treatment where ever you can see a speaker from any seating position reflected in a mirror placed on the surface..

Since you have it drawn out already, it may be easiest to draw out the reflections and place panels accordingly. That way you can design the look before purchasing anything.

Very nice theaters you build

Okay! So that means i need to consider all the first reflection points. Should i do this for all the three seating positions?
And once it is figured out, what should be the height at which walls should be treated. The earlier threads mentioned from ground till ear level, but i have noticed a lot of other starting the treatment much above the ground level.

Don't know if my little app-in-the-making can be of any help.... there's no help on how to run it and it's in metric system... and it's made for centered position mainly... but it can take a drawing as backdrop, so it may be worth playing with...

latest version can be found here:
http://www.nattlorden.com/software/software.html

I do intend to do more with it in time, but it's not currently my main project, but that does not mean I won't take feedback on it.

Does this run on Mac OS X?

For ref here is a ray tracing program and what it showed for 1st and 2nd row in my HT.




You can generalize this to your HT.
Key is some people over absorb by putting too many panels where not needed.

Also, look at the ceiling.

hi Mtb,

Is that software available and how much does it cost?

It's a windows application based on .Net 3.5 - no idea if there's any emulators on OS X that runs such apps. The only Apple products I have myself run iOS, not OS X...

Mtb - that's quite cool. Always interesting to know how other people have solved the same thing. Using raytracing methods has been on my mind - quite fun to have one's ideas verified without having to code it first.

The more precision the tool has, the more precision the indata (room, placement, angles) has to have for the result to be valid, finding a useful balance is a tricky thing.

I have a question about how to treat a room with the lower 38'' of the entire perimeter of the room that is covered in wood panel (wainscotting) I have seen many done this way, chasen the dream theater by jchasen comes to mind. This is exactly the look I want, however it seems to go against what is recomended, meaning all the wood panels are reflective and they are below the ear, for the most part. What the wainscotting doesn't cover I would like to make cloth panels for such as what gpowers has done. Being that high on the wall I would guess they shouldn't have oc703 behind them correct? Poly batten instead? What's left of the front and rear wall surfaces I was going to use oc703, it's the side walls that have me confused. I have read a lot of this thread but haven't seen this adressed, it's pretty long maybe I missed it. Any tips would be great.

Yes, consider all seating locations.

Thank you!

Depends exactly where the placement of the panels is. I would consider using Quest perfsorber possibly...again depending where it is. Regarding wainscoting at that height, it will be an issue.
Edited by SierraMikeBravo - 11/26/12 at 2:28am

Would I be better off to use OC703 or Roxul safe and sound to build my DIY bass traps?

I wont speak to "better" but in my area roxul is cheaper. A lot cheaper -25-40% depending on your hookups.

However it is floppy and requires a frame so you might lose some effective area..... This might mitigate the cost offset.

Is there anyone who sit close to their subwoofer? Since it's nearfield, the frequency response should be flat and not much affected by the room?
I'm wondering this because theoretically small room is bad for bass, but since every speakers and subwoofers are nearfield, will the sound be more accurate?

Near filed is measured at 1" and 12" for subs, beyond that and room modes interact with the bass wave.
How close are you?

What I've learned is my broadband bass traps tame the peaks / valleys somewhat, really help on modal ringing reducing.
However, for multiple seats multiple subs is best approach for flat sub response across them.


Sent from my 32GB iPhone4 using Tapatalk

A speaker or sub being "nearfield" doesn't make it more or less prone to room problems. The room will equally effect a pair of mains, nearfield, or far field monitors/speakers. Room acoustics does not judge speakers before imparting it's effects.

How thick are you building them? If 2-6" thick, OC703 would be 'better' - thicker than that, Safe'n'Sound would be 'better'. However, the differences are not immense and Safe'n'Sound is cheaper. If you can afford it - 6.5" (two batts of Roxul) thick traps of the Safe'n'Sound would produce some great results.

Did this not come out right? As written, this isn't correct, and just wanting to maintain clarity for those inquiring.

In a typical room, proximity to the source is everything for both measurements and listening. Using the example that th OP inquired about, ... yes, the closer to the sub, one encounters less "room", and more sub. All the way to an inch off the cone for a nearfield measurment,....minimizing the room relative to the driver's direct sound.

Overlaying the LP measurement, and the nearfiel measurement of a sealed sub system, one can get a good idea of the freq onset of Pressure Vessel Gain (PVG). You can illustrate how and where the room begins "giving back", as any freq with half a wavelength bigger than will fit into the room won't exhibit the traditional roll-off associated with subs beneath the knee. Free lunch, yada yada. *

Also, another exception is...critical distance; the point of equal energy from both the direct energy and reverberant energy. Now it's somewhat murky due to freq dependent directionality, but that's beyond the scope of this discussion.


You guys are great at GIK, and I intend no dis-respect,....just want to clarify.

Thanks

*for those interested, ping me,... as there's another killer advantage at play here, don't want to muddy up this discussion

Do not place a subwoofer such that the driver is aimed into the seating locations (in a residential sized room). If you do, you should place a 1" thick piece of 1.5 PCF fiberglass in front of the driver. Sometimes it requires 2".
FOH...let's avoid this terminology. Perhaps better as where the x.x wave length is longer than the room dimension. There is too much misunderstanding about "bass not fitting into a room".