How To Proceed With Room Treatments

   I live in a house that is more than 100 years old. My listening room is approx. 16' x 20' in size. The floor is carpeted. There are furniture pieces. In the days this house was built the walls are of plaster over wooden lath rather than conventional drywall.
  My system (for music only) consists of a pair of stand mounts and two 10" subs. I have experimented with moving the speakers to various locations, moving furniture, and have now found placements that sounds best to me. However, in the quest to improve the sound as much as possible, I am interested in the possibility of adding some type of room treatment. While there are many options such as wall panels, corner bass traps, etc. is there any sort of experiments that can lead to a final room treatment that can optimize results before buying the rather expensive panels for that purpose?
I realize this is a very subjective topic but am curious if any have added some sort of temporary material to their rooms to determine how to proceed with a permanent solution.
As to temporary placement:

  • I’ve used milk crates to raise panels, propped against the wall, to see how they do in specific positions.
  • I’ve held blankets above my head to see if ceiling reflections were a problem.
  • I’ve moved bass traps around to see how that works.
And finally, I put a gallery system into the audio room so I could hang all the panels and move them around. Does your old house have picture moldings? They could be used to hold light treatments etc.

What frequency ranges are you trying to work with?

You didn’t ask, but I’ll also note that Guilford of Maine makes thousands of textiles for fabric-covered panels; acoustics vendors will use your specific pattern & color at a slight additional cost. This can improve appearance tremendously over stock colors.

P.S. Another way to proceed is ask GIK or ASC (or both) to make a treatment plan for you, which they will do for a refundable fee. You might not want to follow it exactly, but it will give you some ideas.

I strongly recommend you talk to GIK acoustics. They are pros and can help you get to done fast.

However, yes. Try blankets and pillows. :) Try them on the walls, on the floor, especially between and behind your speakers, on a coffee table, etc.

This will help you try things out relatively cheaply.
@jrpnde I think it depends a lot on what you're trying to accomplish, and your first goal should probably be to figure out what kind of a room you want to have. That will tell you the types of acoustic treatments you should go, where to place them, and how much.

You can save money by doing the DIY route.

I would reach out to GIK and speak to James Lindenschmidt. I have recently worked with him and he made the whole process painless.

Personally, I think their basic panels are quite inexpensive and worth every penny. If you factor in the invaluable advise, it makes complete sense to buy from them. My room is 15” D x 30” W and the whole room treatment cost was under $1500.

To see how they look, you are welcome to check out my system.
Like others have pointed out, reach out to GIK. I spoke to Mike Major recently and we went into details on current and future plans.My room is 16X19 and once the tri-traps on the back corners were added, it was a HUGE upgrade to the bass definition and treble/vocal clarity.
I'm usually a DIY guy, or used to be when I had tools and space. The prices and effectiveness of GIK makes it super hard to justify though.
@milpai I am considering adding tri-traps as well in the back corner.  What height did you go with? Floor to ceiling or just partially?  I have the wall treated with 24x48-inch panels behind each speaker but my corners aren't treated in the rear and I know I'd benefit from addressing them.  Aesthetically I really need to keep a partial height - no more than 48 inches probably.  Just curious what's working for you.  My room dimensions are similar - 15x20.
I went with entire height, floor to ceiling. But the back wall is slightly lower. So I have 48" + 45" tri-traps, leaving 1" to the ceiling. The bass tightened up considerably. You can feel it in the chest. Treble clarity and separation also improved drastically. 
Not everything has to be a trap. You want a mix of absorbing as well as diffusion. Every room has areas where bass is a problem (corners for example). Then you have 1st reflection points and this could be the sidewalls, ceiling and floor.
GIK and ASC are excellent companies or deal with Acoustic Fields for designing and building your own diffusers
jrpnde asks:
is there any sort of experiments that can lead to a final room treatment that can optimize results before buying the rather expensive panels for that purpose?

Yes. What you want is Owens Corning 703 This is 2" but you can use 1", get one sheet of each if you want to test which you like best. Only slight difference as thicker absorbs a bit lower frequency.

OC703 is developed specifically for acoustic absorption and is used in a lot of expensive panels. It cuts easily with a razor blade, sheet rock knife or table saw. By itself, before covering, it is so light you can attach a whole panel to the wall with only some stick pins that make such tiny holes you’ll never notice, perfect for testing.

The most effective location to test first is to put 12" triangles in the upper ceiling/wall corners. Next is 8 to 12" wide by 3’ or longer strips vertically in the corners where the walls meet. Third place usually will be two pieces about 12" to 18" placed on the side walls at ear level to catch the first side reflection off each speaker.

Most people treat side walls with a lot of material to kill slap or flutter echo. The room is easily over damped, especially if it already has carpeting. This way uses a lot less material by treating only the most effective locations. Corners matter greatly because any sound emanating from a corner is reinforced by the walls. Damping in the corners is therefore much more effective than the same area of material on a side wall. Except the reflection points, where it has a bigger effect.

This is all stuff you can test and confirm in an afternoon and for cheap. Just like you asked.

GIK will ship you Owens Corning 703 in a box of six for about $100. 
The panels are 24"x 48" and 2" thick. Enough to play around.
The cost to benefit ratio is ridiculous with their finished panels. Can't go wrong.
If you send GIK photos or even a sketch they will recommend where to start.It's a free service.There is a lot of information to read and learn on their website.The panels are returnable also.I did my room for about $800 and I also have pictures on my system page if you're interested.
Use whatever is handy to experiment with - chair and sofa cushions propped up on tables and chairs in various spots,especially corners is when I began to hear the sound change for the better.