Partial wall reflections - Home Theater Forum and Systems - HomeTheaterShack.com

 
Thread Tools
post #1 of 9 Old 05-10-07, 08:27 AM Thread Starter
Friend of the Shack
 
Otto's Avatar
Otto
 
Join Date: May 2006
Location: Beautiful Colorado
Posts: 1,356
Partial wall reflections

Well, I created a thread here a while ago about general acoustics, and I'm still working out ideas for treatments. As many of us do, I have a number of other "projects" that are keeping me busy at the moment.

Anyway, frequently, while listening to 2-channel music, I'm bothered by a tendency in my system/room to "pull" me toward the left speaker. Sometimes, sounds that I think should be anchored firmly in the center of the soundstage are smeared toward the left. I have one "audiophile test" track that is to test imaging, and the guy is talking out of the direct center (according to him, anyway), and I can clearly hear him coming out of the left, just enough to be super annoying. All this having been said, my system generally performs very well, and a lot of music does image and stage correctly, with vocals coming from dead center. I have considered the possibilty that, although marked as an "audiophile test CD", the track with the man talking from "center", then "right" and so on, could have something wrong with it.

So, check out the attached image to get an idea for the layout of the room. I have been thinking, for a while, that the "full wall", marked in red, is causing some reverberation, as it's almost directly facing the left speaker. The waves then have an opportunity to bounce back toward the speaker, as well as directly off that wall and toward the listener (indicated by where I've drawn the mess of arrows). This effectively reinforces the sound from the left, while the sound from the right speaker is allowed to go beyond the listener to the far wall, creating much less bounceback and sound reflections from that side.

So, what to do? Cover that whole "full wall", marked in red, with a treatment? I'm definitely going to treat behind both mains, as soon as I can get to it.

I have also considered that the problem could be with any other part of my system. I recently swapped preamps, so I know it's not that. Next step is to swap amplifier channels (EDIT: Swapped amp channels, it's not that), and then speakers, to see if either of those are actually out of spec somewhere.

Am I thinking in the right direction in that the "full wall" is causing me trouble?

Partial wall reflections-livingroomlayout.jpg

-- Otto
Otto is offline  
Sponsored Links
Advertisement
 
post #2 of 9 Old 05-10-07, 09:17 AM
HTS Senior Moderator
 
bpape's Avatar
Bryan Pape
 
Join Date: Sep 2006
Location: Wildwood, MO (St. Loui
Posts: 5,244
Send a message via AIM to bpape Send a message via Skype™ to bpape
Re: Partial wall reflections

The non symmetry can definitely be causing the problem. Having the couch right up against the wall is only exaggerating the problem. Is there any way you could rearrange the room to have the speakers up on the North wall of the drawing and the couch out away from the South wall a bit? I think that would help a lot in evening things out.

Bryan

I am serious... and don't call me Shirley.

Bryan Pape
Lead Acoustician

To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
bpape is offline  
post #3 of 9 Old 05-10-07, 09:25 AM Thread Starter
Friend of the Shack
 
Otto's Avatar
Otto
 
Join Date: May 2006
Location: Beautiful Colorado
Posts: 1,356
Re: Partial wall reflections

Hi Bryan,

I would love to move the TV to that north wall, but the "box" that's drawn on that wall in the original drawing (not any of the colors I added) is a large five-panel window. If I had a projector w/ roll up screen, I could get away with it, and I've considered it. But for now, with the 52" DLP, I don't have a lot of placement options for it.

Unfortunately, the couch can't move much either (it's actually an L-shape, and pretty large, with the other leg of the couch (the "L") not shown in the picture. It actually takes a turn at the north end of the couch and heads toward that left speaker.

Our previous orientation was much, much worse.

Any recommendations in the mean time?

-- Otto
Otto is offline  
post #4 of 9 Old 05-10-07, 11:05 AM
supervsl
Inactive
 
Posts: n/a
Re: Partial wall reflections

E:

I blame your couch. I think the end of the "L" is to close to the right speaker and is drawing you off center. Would it be possible to rotate the couch 30 to 45 degrees to balance the accoustic effect that it has on your sound?

Partial wall reflections-tempimage6.jpg

You are more than likely still going to have extra reinforcement from the right due to the missing walls on the left side of the room. I still expect better sound field centering if the right speaker is not pointed directly at the end of your sofa.

And, is your diagram mirrored or am I going crazy?

Nick
post #5 of 9 Old 05-10-07, 11:49 AM Thread Starter
Friend of the Shack
 
Otto's Avatar
Otto
 
Join Date: May 2006
Location: Beautiful Colorado
Posts: 1,356
Re: Partial wall reflections

Hi Nick,

Yeah, I tend to agree about that couch "L" doing some weird stuff with that speaker. But it seems like it would absorb sound, not create it. On the other hand, perhaps it's absorbing bass, making the highs seem more pronounced. Or perhaps it's too stiff and it's reflecting sound back toward the speaker itself and/or the wall behind that speaker.

I like your idea of rotating the couch, and it give me a good idea that I can do more quickly (that couch is a bear to move!). I'll just remove the "L" segment completely, such that there's no obstruction between me and the speaker at all. I think that would give me a quick and easy way to see if it's a contributor. And I can do it in 1/2 an hour! I will almost certainly try that tonight and see what happens.

Then I swap speakers. I really, really hope it's not my speakers.

You're not crazy -- the diagram is mirrored. I got the layout from the original owner, and thought it would be easier to handle that drawing something myself. I should have just drawn what you did!

Thanks for the ideas.

Have a good day.

-- Otto
Otto is offline  
post #6 of 9 Old 05-23-07, 11:24 PM Thread Starter
Friend of the Shack
 
Otto's Avatar
Otto
 
Join Date: May 2006
Location: Beautiful Colorado
Posts: 1,356
Re: Partial wall reflections

Hi.

I was able to move my couch out of the way of the speakers. I detached the two sections from the "sweet spot" seat. I moved them back about three feet. I also angled the curved part to be at a different angle as I could imagine that it might actually "sweep" or "direct" the sound toward my right ear when seated in the listening position.

This "problem" continues to bother me. I think I will swap speakers next.

Here are a couple pictures of the actual room in its normal configuration.

Partial wall reflections-100_2732.jpg

Partial wall reflections-100_2739.jpg

-- Otto
Otto is offline  
post #7 of 9 Old 06-03-07, 09:27 AM
mhakman
Inactive
 
Posts: n/a
Re: Partial wall reflections

A question/comment from a newbie: Could the large window be a part of the problem? While windows are normally transparent for low bass, they are reflecting mid and high frequencies. According to your drawing, your listening position is on the reflection path from your left speaker to window to you. This could cause both higher perceived sound volume level from the left speaker and the whole stereo image to be shifted to the left. My listening room has also a big window along one of its sides and I noticed a similar effect. Using an SPL meter I adjust volume level for both speakers to be the same at my listening position but I still perceive more sound coming from the window side. It also feels as if the sound stage was extended into outside my window.
post #8 of 9 Old 06-03-07, 01:43 PM Thread Starter
Friend of the Shack
 
Otto's Avatar
Otto
 
Join Date: May 2006
Location: Beautiful Colorado
Posts: 1,356
Re: Partial wall reflections

Yeah, could be. Although the picture shows the glass exposed, I normally have a full shade down in front of the glass. It's an accordion type pull down thing. You can't see it at all in the picture; it's hidden inside the valance above the window. It's not really absorbtive, but I think it's better than glass.

-- Otto
Otto is offline  
post #9 of 9 Old 06-03-07, 02:47 PM
mhakman
Inactive
 
Posts: n/a
Re: Partial wall reflections

Well, one way to test it is to remove the windows entirely. This is what I will do this summer, when the weather is good and the neighbors are away
Reply

Bookmarks

Tags
partial , reflections , wall

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome