Dipole speaker wall treatment

[mgard]

I am thinking about room treatments for my 3.7i's. I ran across this answer to the question, "How do I set up my new room". I thought it was interesting what this person suggested the minimum and maximum distance out from the front wall should/could be. I see that I need to move my audio cabinet from behind my speakers.

Answer:

In general, dipoles require less acoustical treatment than other speaker designs, in fact, the treatment that works for boxes tends to suffocate them. Most dipole owners prefer diffusion at the first reflection points behind the speakers -- that is, the points at which you see the speaker reflected in a mirror when you're sitting in the listening position. A QRD diffuser should work.
Dipoles don't generally require treatment on the sidewalls, because they radiate less sound to the sides. You can experiment. No treatment on the floor or ceiling, though a carpet or rug is OK.
Other things you'd want to consider are bass trapping -- dipoles are less likely to excite bass modes but they still do excite some, depending on orientation. Also whatever HF absorption you need to get a good balance. Rear wall absorption if you sit very close to it, maybe diffusion if you don't, plus whatever diffusion you need to get rid of slap echo.
Since it's a custom room, remember that the first rule of amazing dipole listening is BIG! The image keeps getting more impressive until they're at least 15' off the front wall. But the minimum you want to aim for is 5'. The further out they are, the more depth you'll get.
Front wall itself should be (aside from the diffusers) a flat plane. Maybe a bit rough, e.g., brick, but no real features, dipoles are like sonar. If you can, make the wall pretty wide as well, the sound will start to wrap in where it hits the side wall. It might be advantageous in that case to experiment with diffusion or absorption at the corner reflection, which is a second reflection (speaker to front wall to side wall to ears). With dipoles, this is generally more significant than the sidewall first reflections since it isn't in the dipole null.
As with any room, go for a rectangle, non-parallel walls cause more trouble than they're worth. A custom room can have bass trapping built in very economically, I'd look into that. I'd prefer wood for the floor, build a raised one if you have concrete. Don't go for a cathedral ceiling or anything like, just a flat one, and don't go for a high one, line source dipoles work best if they touch both floor and ceiling. Just make sure it has enough height for Acoustats, which I think are the tallest speakers commonly seen (about 8').
Finally, don't make the common mistake of putting your equipment racks between the speakers. Sometimes you can get away with this with dipoles if they're low, but remember the sonar effect -- they can interfere with the imaging of any speaker. They're better put on the side or at the rear of the room.

[cma29]

Great info. Thanks for sharing.

I need to experiment more with placement. (Can't do 15 feet off the wall though. My cables will not reach that far!).

Also, interesting comment about the rack placement. Mine is between the speakers now.

[timm]

I also find the discussion about diffusion,diffusion, diffusion.... and if you have slap echo... move difussion..... No absorption... In fact - a brick wall being preferred as the front wall.... Building a wood floor over concrete - another example..... Do we all agree with these ideas ?

I have a concrete floor - and I am trying to figure out what to do with it.... thought was carpeting.... as I thought??? that would give a nice solid sound and help with reflection and slap echo? The author seems to think a more reflective floor like wood is better?? any one else care to chime in?

thanks tim.

[mgard]

If you do a google search on "Magnepan room treatment" or "Magnepan room placement" you will find some interesting discussions. My cement floor has 1" X 4" planks shot nailed with 3/4" 4 X 8 foot plywood on top. Then I have the carpet pad and carpet. This was installed before I thought about moving my audio system to the basement. My concern was not having cold feet when walking on the floor. I certainly shouldn't have to be concerned about any reflection off the floor.

~Mike

[cma29]

Originally Posted by timm

I also find the discussion about diffusion,diffusion, diffusion.... and if you have slap echo... move difussion..... No absorption... In fact - a brick wall being preferred as the front wall.... Building a wood floor over concrete - another example..... Do we all agree with these ideas ?

I have a concrete floor - and I am trying to figure out what to do with it.... thought was carpeting.... as I thought??? that would give a nice solid sound and help with reflection and slap echo? The author seems to think a more reflective floor like wood is better?? any one else care to chime in?

thanks tim.

That's what I have on my concrete floors - carpet. Works well. The ceiling is 84 inches high so the 20.7s don't have much clearance, but that's good according to the advice given.