[jpv]

Back in a previous post "sub location with respct to room treatment" i asked if modes mattered if I had a ceiling that came to a point directly over my head. Bryan (bpape) said that is not my issue as much as the horn effect. He suggested absorption. My room is 13.5 x 18.5 x 10 foot ceiling in the center. My questions are

1) If I add absorption how much area do I need to cover. The entire length of the room and how wide.
2) will a poly work in the peak instead of absorption? or maybe both.

I was thinking of making 2 x 4 poly's and absorption panels - or in one 2 x 4 panel putting a 2x2 poly and a 2x2 absorber.
 I currently have 4 bass panel traps, 3 corner bass traps, 2 tri corner traps in the peak of the ceiling front and rear, and broadband absorption in the first reflection points .
 
john

[bpape]

Just to clarify, I said that the height mode wouldn't be an issue because there isn't a pure height mode.  That said, the tradeoff is the buildup of bass in that corner and focusing back at you like a horn would.  Diffusion isn't going to work at that peak - sorry.  Diffusing a bass wave requires diffusion MUCH bigger than 2'x4' and very deep.  You're better off to absorb it.

Now, on the slanted parts of the ceiling, using a poly can be very effective at dispersing sound and stopping the additional direct reflections.

Bryan

[jpv]

Bryan,
  Thanks for the reply. So I take it I need bass traps the full length of the ceiling or as much I can cover.
Would 4" of 703 in a 2 x 4 frame work? I figure 3 would take me most of the way along the length of it. I would then hang parallel to the floor, and leave space behind them, correct.
I already marked my sloped part of the ceiling to put polys there.
John

[bpape]

Hi John.

4" in a frame straddling that peak and hung parallel to the floor will work very nicely.  You can get them as tight to the edges as you can.  The distance behind will already increase the depth of absorbtion.  If you want to hang them a little lower, it certainly won't hurt anything.

Bryan

[Housteau]

I had a similar situation and built my own solutions with Bryan's help over the phone.  Because of the dimension of my span I chose to build a mix of 2' x 2' and 2' x 4' framed treatments.  In my room the cathedral peak was causing higher frequency focus and imaging issues as well. 

         

[jpv]

Housteau,

  Thanks for the Photo, That is what I thinking of doing. How did you attach them to the ceiling?
I am going to do 3 to 4  2 x 4 traps. Are they all broardband. What kind of changes did you notice?

John

[Housteau]

John, I am sorry for the delayed response, but just noticed yours and your question.  My cathedral peak has a 6 x 6 inch wooden beam running the length which makes attachments easy.  For the units mounted flush to it, I just notched out the two sides that straddled the beam allowing long counter sunk wood screws to grip and dig in.  This still allows for a small gap underneath on either side of that beam to aid in the effect.  For the ones that straddle the upper tricorners, I mounted sets of eye screws to the walls and beam, with hooks to the treatments themselves.

The changes most immediate to me were a transition to a very stable focus and soundstage.  The bass had most of its correction with the full four corner traps that I had built first.  These added to that and smoothed things out even more.  The changes were measureable to a point, but the effect noticed seemed more prominent that what the measurements would suggest. 

Dave

[8thnerve]

Yeah, you've got to treat the peak as any corner and cover it!  Make sure to use a product with a reflective front layer (or at least a semi-reflective front layer like RealTraps or GIK) to trap that sound trying to come down at you.  You'll fix many bass issues this way.

Nathan Loyer
Eighth Nerve

[jpv]

Nathan,
  Wouldn't adding a semi reflective front layer just reflect the freg. I am trying to remove? Are you saying I shouln't use broard band absortion and focus more on the bass?

[bpape]

A semi-reflective layer will still absorb some at broadband frequencies.  What you're trying to do is eliminate the horn effect from the corners and kill some of the bass buildup. 

Bryan

[awe-d-o-file]

I have a cathedral ceiling and finally treated it this week. WOW! Do it! I already have 8-4' X 18"  round bass traps. Those and then new 4'X2'X4" thick panels I just made were from Jon Risch's DIY recipe. Here is a link to pictures and the post on the benefits heard.

                                                           ET


Post: http://www.audioasylum.com/forums/rives/messages/4911.html

[bpape]

Congrats.  That's always a good idea to trap that peak.  If you get ambitious sometime, try it with 4" thick panels.

Bryan

[awe-d-o-file]

oops-fixed the typo in the post and added dimensional clarification. They are four inches thick. Thanks!

                                                          ET

[jpv]

I'm glad to see you have had good result with your traps. Thanks for sharing it.
How did you attach them to the ceiling? They look like they are close to the ceiling.  Did you put a semi-reflective layer in front?

[awe-d-o-file]

I used eye hooks.  Eye hooks  on the ceiling beam and one on each end of the trap. They are about 6" from the ceiling. They are attached to the beam that runs the apex. It is about 5" plus one inch for the two eye hooks. The front just has batting and burlap over the unfaced insulation. As I keep listening to more of my collection I am stunned at the improvement.

                                                              ET                                               

[TONEPUB]

I just did that in my listening area with some GIK panels with excellent results
as well!

My peak is about 13 ft high and initially I lowered the panels too low!
It was like being in a giant set of headphones....

But I eventually got them back up to about 18" from the peak and
it's worked like a charm.  Best sound upgrade I've ever made for
a couple hundred bucks!!

[jpv]

Well, I finally purchased the materials for my ceiling project. I wanted to use OC 703 but I couldn't get it here. I did get some rock wool 6# on line. I purchased 12 - 2'x4'x2" panels. What I plan on doing is removing everything out of my room and measuring the response using a radio shack meter and REW. The only thing that will remain is the stereo, 4 panel bass traps, a couch, and a desk. I will add one treatment at a time, measure and listen. I am doing this just to see what changes I am getting. I will post the results here as I do it.
My first step I will upgrade the corner bass traps with 4" rock wool from the 2 1/2" I have there now.
Then I reinstall the 4 broadband trap at the first reflection points.
I plan on adding new to the room Bass traps to the back wall corners and traps on the ceiling along the peak.
I want to add  2'x4'x4" traps along the whole peak. Do you think that is to much? Should I put something reflective on the front? How does this plan sound?