Help with strong left image but weak right

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
After spending a lot of time positioning speakers and applying treatment, I am close to being happy with the results, but my room causes a stark difference in left/right imaging (? - not sure if I'm using the term correctly) that is driving me crazy. I assume this is due to the right side of my room opening to a tiled area instead of being walled. If that is the case, do I have options that don't involve moving my setup or building a wall?

Example of what I'm hearing - mono sounds exactly center, and I do not notice this as much in lower frequencies (male vocals, for example) or on tracks that are mixed hard right. On the other hand, higher frequencies like female background vocals or pianos placed center left sound great, but if I switch the L/R input, I lose not only location but the instrument itself. I don't know a good word to describe it, but I have to focus to hear it at all, and when I do, it's as if I can hear bits and pieces of that track fluttering around in a giant mess.
 
Member
Joined 2009
Paid Member
Hi,
From what you describe you experience the issue related to non mirroring side of your listening space. You'll often see advice about having the exact same layout for left and right side of an imaginary line dividing your listening space in two half from rear to front wall. This is to have same behavior for early reflections in the lateral/horizontal plan.

If some frequency are disappearing you have probably a side wall which distance induce a null at the frequency in question. Have you tried to change your listening position ( eg, move your listening spot closer to the front wall)? Does it change the artefact?

From your description i would suggest as this happen relatively high in frequency (high mid) this could be fixable using a panel for mimic the other half of your listening space. Size of panel will matter but something 1m2 should be enough given the freq involved (1m is ok from 1k and up to reflect sound).

If you can try with a wood panel to determine size, location (and if it don't induce other issues) then once done you could make it in plexiglass or perspex to have it less visually intrusive.
 
Member
Joined 2009
Paid Member
Hi Pano,
Yes it could work too the opposite way absorbing rather than reflecting.
That said if possible i prefer to reflect as it keep energy 'equal' ( from the radiated view) in the room. That said if there is a null from wall distance using absorption may not give expected results. Mark should make some test to determine exactly what is happening.

If going the absorbtion way Mark could use some ceilling tiles like this one:
https://www.rockfon.fr/produits/rockfon-logic/

If the culprit frequency is high mid this offer low depth solution and is safe to use. As the face is white you can use fabric to make them less intrusive and acceptable in a living space.
 
I haven't listened for this specifically at other places to know if my listening position matters. Are nulls dependent on my position only or does the speaker location matter, too, and how dramatic of a change should I consider - a few inches enough or do I need to move a few feet? I do have treatments for first reflection points along the side wall and the front wall (ceiling on the to do list, carpet on floor, back wall reflections arrive after 20 ms) which I assume help with the imaging I do hear so if I change positions, I assume I need to move these, as well?



Mimicking the existing wall is a good idea, but will that introduce reflections from the opening side that don't exist due to my absorption on the right side?


If helpful, I can post pictures, dimensions, REW measurements, or other info.


Thanks!
 
I agree, listening environment symmetry is vital to achieving a stable and balanced image: make that your number one priority. The role of room reflections and modes is often misunderstood. I wholeheartedly recommend reading Floyd Toole's book "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms" if you can get a copy.
 
Member
Joined 2009
Paid Member
Hi Mark,
Yes if you have pictures, rew plots, etc,etc, it will help.
Difficult to answer your questions relative to change in position (listening, loudspeakers,...) it depend of many factors.
First try to estimate if change occurs when changing listening position, then loudspeakers, etc,etc...
One thing to keep in mind: don't do multiple change at once, only one at a time or you won't be able to tell what did what.

If recreating a wall is possible then using a plasterboard (ba13) should be the most economical solution for tests. You make a stand for it and it is easy to cut using a knife.

Yes there may be differences from your already treated wall but if a null occurs it will help and it shouldn't be to difficult to mimick the ER treatment already presents.
 
Thanks, krivium. Once I start troubleshooting, any thoughts on where I should try placing the panel?


Below is a picture of the left/right frequency response in REW (1/6th octave smoothing) as well as a picture of the room. For reference, if there were no opening, the wall behind the speakers would be 13ft 4 in, long wall is 24ft 3in, ceiling is 9ft 0in, and I'm sitting 10ft 7in from the near wall.



An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.
 
diyAudio Moderator
Joined 2008
Paid Member
put an absorbing panel on the wall that causes the reflections.
I'll give the following reasoning for this being the better option.

Duplicating reflections can be difficult, especially when they become complex in an asymmetric room.

Early reflections are rarely evenly distributed throughout the space but are rather more specific, and are a known enemy of good imaging.

Even if you did add a replacement reflecting surface on the other side, success would be simpler if it also absorbed the higher frequencies.
 
Hi Allen,


Do you have suggestions on where I might put absorption on the wall? I already have some there to treat the first reflection points shown in the picture of the room above.

An externally hosted image should be here but it was not working when we last tested it.


I'm also attaching the impulse response out to 25ms. It looks pretty good - the big spike around 5.5ms is from the ceiling and pretty symmetric. (I plan on treating that only once I'm sure I won't change my listening and speaker positions.)
 
Member
Joined 2009
Paid Member
Hi AllenB,
Well it'll depend from the source of the issue.
A 50cm wide panel could help for freq from 2k and up if the disapearing frequency come from a null.
Absorbtion on it could be used in order to mimick the other wall treatment too.
In studio we regularly use 'gobos'. Primary intent is to isolate different source when doing multimic tracking in same space but i sometimes used them to redirect sound from the source ( on drums) when acoustic is difficult and doesn't fit the sound i'm after.
I was in the lucky position to have access (at one time of my life, not anymore) to some fancy modular gobos whic had multiple possible use: either reflector ( plane faceplate), diffusor, absorption for hi/mid (foam faceplate), and or basstrap (using the volume of each modules). Each modules could be mixed and this gave very acceptable results.

Anyway without being with Mark it'll be difficult to have a correct diagnosis of what is happening. By the way i don't have access to pictures previously posted by Mark. Is this a problem on my side or do you face the same issue?
 
Last edited:

Attachments

  • left_right.jpg
    left_right.jpg
    105.1 KB · Views: 34
  • left_right_reflections.jpg
    left_right_reflections.jpg
    149 KB · Views: 43
  • room.jpg
    room.jpg
    645 KB · Views: 60
Member
Joined 2009
Paid Member
Ok now i can see pictures.
I stand with my option: make something movable that will give you symetry from the other wall:
some kind of trolley with a stand and a plasterboard (or multiple) and same treatment for ER. The superchunk corner trap is hopeless to duplicate imho.
Could work great ime with gobos.
Put some Qrd 1 dimension diffusors (with effective lowest freq around 1khz) on ceiling ( as a triangle shape using six of them in three row, 1/2/3 by row) and alterning orientation of the diffusor and you may be ok imo.
1khz Qrd diffusor should'nt have more than 10cm depth and being 50/60cm square. Not too heavy to hang (especially if you make them from lightweight wood like balsa- given the freq range the fact it is lightweight won't be too much an issue).
 
Last edited:
diyAudio Moderator
Joined 2008
Paid Member
where I might put absorption on the wall?
Imagine your wall is a mirror, and place it between the speaker and your reflection.

Your right speaker might be the bigger issue because it is pointed at the wall and the left speaker is not terribly close considering it isn't. This is just my experience but not all speakers are the same.

However, the issue of imaging and the issue of lower frequency cancellations each require a different view of the problem.

It looks pretty good - the big spike around 5.5ms is from the ceiling
This is good work.

By the way, steep angles toward the ceiling extend the reflection time which can be good or bad.
 
what's the drywall attached to?(is the strapping for the wall studs ramsetted into the wall?)
this is a basement obviously with a concrete floor (or at least that's what it looks like) is still exposed in the listening area?
can we see the 180 deg view? if this is a "butt" end i would relocate the speakers there.

nice bar, where the beer fridge?

is the bulk head over the bar to accommodate for ventilation and plumbing?
 
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.