[ebag4]

I was communicating with Dave the other day concerning his diffusors.  He asked what I had in place already, I told him and rather than sell me diffusors he responded with "well have to get those upper corners taken care of before doing anything else", pretty selfless in my book, just one of the things that makes Dave one of the "Groovy People"  .

Dave recommended that I put something in the upper corners that reflects instead of absorbs.  He recommended to try cardboard first to determine whether or not it would be beneficial in my space.  I went ahead and used some of the exterior rigid foam board used on houses.

According to Dave you can adjust the size to taylor them to your space, he recommended that I start with a large enough triangle to fill the space between my ceiling and 4' high bass traps, that worked well in my room.  For the rear corners I had to use a triangle much smaller to accomodate a couple of doors.

The improvement was easily heard and substantial.  Better clarity across the board.  I still need to fill the corner with polyfil but these treatments will be staying in my space.

It is super easy to try and doesn't have to cost a thing but a little time.  I used painters tape to mount mine. Give it a try, you just might like it!

Thanks Dave, much appreciated.

edit:  A pic is worth 1000 words so here you go!




I should mention that Dave covered his in 1/8" thick quilt batting covered by material, I obviously haven't gotten that far.

Best,
Ed

[dBe]

Ed, looks like you have it well under control.  Cool 

Tri-corners are particularly nasty sources of acoustic comb filtering (http://en.wikipedia.org/wiki/Comb_filter and http://www.moultonlabs.com/more/about_comb_filtering_phase_shift_and_polarity_reversal/) that we run into in a normal room during playback.  The distortion caused by these reflections is most noticeable when it is gone, just like most of the noise in our systems. 

As we get rid of these evil sources of disinformation problem by problem we realize one of the really cool things about building systems capable of great playback: it can always get better.  That is what we are all about, huh?

Dave

[PDR]

I'm on those Ed......will post some pics and opinions this weekend.

I love "tweakin".........

[dBe]

Here is a picture of mine:



It is made from exterior sheathing and covered with raw cotton batt.  The opening at the bottom provides access to bass traps and a hangar for the little white RC helicopter guy visible at the bottom.

The side panel is 1" FSK ductboard in the first reflection point.  It is open in the back to a FG filled cavity to provide bass trapping with the FSK backing acting as a diaphragm to boost LF absorption.

I just got a PM from Anand about his construction of a new room for his HT which is very cool in the way he used FSK backed 703 to provide absorption and bass trapping in new construction.  I hope he will post the details here.  It is of GREAT benefit to remove 90 degree intersections from boundaries.

When I do the remodel in the listening room I will be adding an angled crown molding around the wall/ceiling intersection that will also conceal perimeter lighting.

Dave

[JohnR]

If you don't mind my asking... wouldn't you want them at the floor corners too?

[dBe]

If you don't mind my asking... wouldn't you want them at the floor corners too?

Absolutley, John.  ANYTHING that can be done to eliminate a 90 degree intersection is beneficial.  I have designed and built rooms with no 90 degree intersections - not even at the floor/wall boundary.  This is especially true at the high pressure corners at the front of the room adjacent to the speakers.  Building them as a lossy (read that as "flexible") surface in a pressure zone will help suck out LF energy, with the triangular or trapezoidal shape giving a less specific (ie: broadband) tuning.

One thing we have to remember is that all speakers will pressurize rooms, just in different manners.  Open baffle speakers pressurize zones in a room, with the net pressurization being effectively zero.  These constructions can be used to do two things: redirect the mid and HF energy from the corners and provide LF trapping in those zones at the same time.  As you can tell I'm from the Reflection Free Zone method of room design camp.  LEDE designs tend to sound too dry for my tastes.  I prefer to have the mid and high energy present in the room in an uncorrelated form to yield a more airy presentation.

In my remodel, the trapezoid will extend from ceiling to floor with the broad dimension at the ceiling and the narrow dimension at the floor.  I will also use them to conceal my (separate system) HT L/R speakers.  Between them will be a diffuser array framing a flatscreen monitor that will have moveable diffusive/absorbent panels to cover it during 2-channel listening.

Dave