From your post it would appear that you have established a fixed listening seat. If that is so, then you might eliminate the null by simply moving the listening chair back or forward somewhere between +/- a foot.
Get a test disc, a SPL meter, some graph paper (for easy visualization) and start carefully measuring actual results of speaker/listening chair positions. Programs for speaker placement, etc, are nothing more than suggestions for good starting points. There are far too many things that can change the speakers response that can't be factored into a program.
One of the benefits of the meter/test disc assessment is that you will soon learn (or if you are dumb like me, slowly learn) what nulls are inherent in the rooms dimensions which will defy correction by most any means, and nulls which are location related. The only problem with the former is you really can't, as a practical matter, change them. The only problem with the latter is that often you can change the frequency peak/null by moving stuff, but often you just move the peak/null around a bit. No matter what you do you will have to accept some form of compromise.
A personal experience. I spent some years trying to improve my frequency response, close to flat as it were except for a 6db suck out at 40 and 50hz. Never did it - I even tried using a sub with a very low cross over point (40hz) with mains running full range and when I tried to eliminate the null the sound became boomy and muddy. Wana sub? :-) I just concluded that this null was barely audible (speakers are flat at 32hz and down 3 at 25hz) something I could live with.
Shadrone's post is an excellent summary I think, except that I'm not at all sure about Commcat's comments about the surface or furnishings on the back wall having much effect on deep bass nulls. But that is just my opinion.
O
Get a test disc, a SPL meter, some graph paper (for easy visualization) and start carefully measuring actual results of speaker/listening chair positions. Programs for speaker placement, etc, are nothing more than suggestions for good starting points. There are far too many things that can change the speakers response that can't be factored into a program.
One of the benefits of the meter/test disc assessment is that you will soon learn (or if you are dumb like me, slowly learn) what nulls are inherent in the rooms dimensions which will defy correction by most any means, and nulls which are location related. The only problem with the former is you really can't, as a practical matter, change them. The only problem with the latter is that often you can change the frequency peak/null by moving stuff, but often you just move the peak/null around a bit. No matter what you do you will have to accept some form of compromise.
A personal experience. I spent some years trying to improve my frequency response, close to flat as it were except for a 6db suck out at 40 and 50hz. Never did it - I even tried using a sub with a very low cross over point (40hz) with mains running full range and when I tried to eliminate the null the sound became boomy and muddy. Wana sub? :-) I just concluded that this null was barely audible (speakers are flat at 32hz and down 3 at 25hz) something I could live with.
Shadrone's post is an excellent summary I think, except that I'm not at all sure about Commcat's comments about the surface or furnishings on the back wall having much effect on deep bass nulls. But that is just my opinion.
O