Vertical Bass Null? Thoughts/

[BlueWizard]

I came across this in a consumer audio forum. A user is claiming that when he sits in his favorite chair, the bass goes flat, but when he stands up, the bass increase to where he thinks it should be.

I can understand horizontal bass nulls, but am somewhat confused by vertical bass nulls.

I told him to stand beside the chair at the seated listening position then step forward into the standing listening position, to see if he got the same effect.

He says he has tried that and continues to claim it is a vertical problem.

The only equipment information I have is this -

"...b&w685 fronts pioneer vsx-1018ah(stereo is listened thru pure direct)..."

Link to B&W685 photos -

http://www.bowers-wilkins.com/displa...fid=2374&sc=hf

I realize I haven't given you much information, but does anyone have any thoughts on this?

As more information comes along, I will pass it on. But for now, given the limited information, does anyone have any thoughts on potential causes and solutions for this?

Steve/bluewizard

[markus76]

This phenomenon is called "Room Modes". Watch them in action here (hint: you can rotate the "room" with the mouse):
http://www.falstad.com/modebox/

Best, Markus

[Rudolf]

Originally posted by BlueWizard
I came across this in a consumer audio forum. A user is claiming that when he sits in his favorite chair, the bass goes flat, but when he stands up, the bass increase to where he thinks it should be.

I can understand horizontal bass nulls, but am somewhat confused by vertical bass nulls.

... does anyone have any thoughts on potential causes and solutions for this?

There are vertical room modes as well as horizontal ones. Standing up in a room with low ceiling can easily move you from a bass null to a bass peak. It depends on the individual geometry.

[BlueWizard]

Solutions?

Acoustical Tile?

Bass Traps?

Absorption?

Diffusion?

Just looking for general ideas. I'm not sure to what extent this person can make alterations to the room, and I further suspect that whatever must be done, must be done on a tight budget.

Anyway, thanks for the thoughts.

steve/bluewizard

[markus76]

Try to optimize the speaker and/or listening position. Then there're numerous possibilities from cheap to expensive. But none of them can be recommended without much better knowledge of your room.

Best, Markus

[HiFiNutNut]

Unless the ceiling is very high, I would speculate that it is most likely due to a null or nulls from frequencies higher up rather than a bass null.

Our perception to bass is poorer than higher frequencies. I have found in numerous experiments that when I was tunning my 3 way speakers, when the frequency response below 500Hz was not changed, changing the high frequency response had a profound effect on the perception of bass. I used drum and organ music to test how well the speakers could handle it. Interestingly, the harmonics are more important to making a drum to sound like a drum and an organ to sound like an organ.

Regards,
Bill