# My ceiling first reflection point is behind my head



## Talley (Dec 8, 2010)

Went w/ the mirror found all my first reflection points for my L/R Mains. Since my ceiling is a cathedral my reflection point sits behind my head.

I use the computer chair for my music listening and it sits where it shows. I'll start hanging my panels this week.


----------



## robbo266317 (Sep 22, 2008)

Hopefully you will get some noticeable improvements when you do :T


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

Here's an excellent article that dispels some myths of first reflections.

http://www.madronadigital.com/Library/RoomReflections.html

Regards, 
Wayne


----------



## Talley (Dec 8, 2010)

Wayne A. Pflughaupt said:


> Here's an excellent article that dispels some myths of first reflections.
> 
> http://www.madronadigital.com/Library/RoomReflections.html
> 
> ...


Interesting article. I have my own theory on how a room should be treated. First reflections are important but all reflections are more important.

The reality is there will always be reflections... you could never eliminate them ever. You can absorb them, or deflect them in other directions or break them up by diffusion. Lower frequencies benefit from passing through the walls/floor/ceiling so there is little to no need for me to do much to them. I have major echo in my room from bare walls bouncing back and forth. This is fact. The article said you don't see echo in small rooms but you do... because the distance the bouncing back and forth is so large. Absorption can be bad and I have a theory where you could essentially treat only half a room as treating one wall affects how the other wall sounds.

They say our ears are most sensitive around the 1,000-4,000 frequency range. I say only treat a room for these levels first then see if you even need to treat for lower frequencies which are less sensitive in comparison. Your telling me these ultra sensitive higher frequencies don't overpower the lower end? I think it does. Everyone says bass traps etc but in the end you suck the life from the room. Bass is suppose to be room filling for a reason, it's natural. I'm treating my room for 1,000-4500 and will leave it alone and see how it sounds. 

First reflections is a joke because the entire room is reflecting everything from all angles back to you. Your responsibility is to treat the entire room equally but not entirely. What that article said is correct. Our brains need comb filtering for things to sound natural. It's in our everyday lives. If you listened to a stereo in an anechoic chamber it would sound bad. But... people always want to do minimal treatment due to economic reasons so first points are the first picks. The 2nd can be almost as strong as the first reflection. Treat the whole room.

This is why I think you shouldn't treat more than 50% of any wall space. You need reflections for natural sounding playback. Take my back wall for example it's 20.5'x7.75' tall or ~160sqf total. I already have a couch taking up the back wall space by around 34sqft. I don't want to treat any more than 80sqft of wall space. I'm placing two 1x8 diffusion strips, one 4'x7' qrd panel and two 2'x2' absorption panels which will total 52sqft of space... then add the couch and I'm at 86sqft of wall wall covering. 

This alone leaves enough wall space to keep some comb filtering in affect to keep the wall sounding as naturally as possible yet reducing the decay to a reasonble level. This further reduces the front wall interaction by breaking up the back wall reflections. I'll move onto the ceiling where I have the same 160' area that will need the same 80sqft of treatment. Of this I'll do about 30% absorption (24sqft) and 70% diffusion (56sqft) so I'll make 6 panels 1'x4' and make 4 - 2'x4' diffusion panels and 4 - 2'x3' poly diffuser panels.

My other half of the front ceiling will mimic the back ceiling but in an alternating panel type fashion and the side walls will get 1'x6' tall qrd strips about 4 of these placed alternating distances with some 1x4 diffusion strips mixed in and then the area above the ceiling line in the cathedral part with get similiar covering.


----------



## Talley (Dec 8, 2010)

don't forget the floor which most have carpet which is 70% absorption capable in the 1,000-4500hz range. It's fine you just have to fill 50% of the area with diffusion. Tables, bookshelves, speakers, audio racks, etc all cover up some of that carpet and help. The main areas would be the primary spots between the speakers etc for creating a deeper soundstage.

So in a way the article is right... comb filtering produces realistic sounds. Just needs to be done in a way to be controlled.

Absorption is the worst way to treat a room although it serves importance just needs to be done as little as possible and/or needed to get the reverb time down.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

I like your theory about not over-treating; fifty-percent seems reasonable. :T I’d tend to agree that reflections can indeed be a problem – typically heard in empty rooms or rooms with concrete or ceramic tile floors (which amounts to the same thing!). If I were house-shopping, tile floors would be an absolute deal breaker for me. That and pine trees. 

Personally I’ve never heard a room with wall-to-wall carpet and normal furnishings that I thought sounded bad. I’ve been fortunate enough for most of my adult life to live in places with “open concept” living rooms with cathedral ceilings and lots of openings to reduce the effect of reflections and smooth out bass.

Are you going to take some "before and after" measurements with REW to gauge the effect of the treatments?

Here’s a pic that shows the effects of normal room furnishings on reverberation times. It shows you're on the right track being concerned about the 1-4 kHz range.










Regards, 
Wayne


----------



## Talley (Dec 8, 2010)

I've taken tons of before. I'll have to do some after but honestly I have a hard time deciphering anything but the frequency response. The impulse is hard for me to read... from lack of experience.

You also have to remember the only thing that is in my room is one couch and one small coffee table. On the main wall is the projector screen that sits off the wall which I have to assume it's allowing some kind of high frequency absorption with the nature of the screen and it's flexible nature. I also have a 48" wide audio rack that sits up against the wall under the screen and my speakers.

I don't have alot of furnishings as depicted in that image. I do however have a second story room with 2x6 tongue and groove subfloor and all regular drywall/studs. What this means is two things... I have a loud noise floor and everyone in the house can hear the audio.

However this room construction acts as one large bass trap and I think I have a pretty good response in the bass considering my room is essentially bare. This is without bass traps at all.... nothing in corners.


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

If nothing else, comparing before and after unsmoothed frequency response graphs can tell you a lot. Once the treatments are applied, there should be visibly less comb filtering (on the graph) above the bass frequencies.

Regards, 
Wayne


----------

