Exploring BIR

[John White]

Great test Dan!

If it's not too much trouble, would you post another graph with about half the amount of sweeps? I'm on my iPhone exclusively for the next week and the graph is a bit busy. (two greens, two purples, etc.)
Thanks

[mhch]

Great test indeed, thanks

Unfortunately, it's hard to identify which graph is what from the legend format which is very dense, even when using a large 21" display

Could you post the results in a easier readable form, either annotating the graph with arrows/notes, or using much less curves per graph, or whatever is convenient to create ? Thanks

[Jens Eklund]

SBIR
SBIR
SBIR

Put simply: that room is simply way too small to be able to study the effect of a single boundary (or a limited selection of lower order reflections) considering the time-bandwidth requirement for a gated frequency response for the lower frequency range.

[PaulRain]

Ok it's clear that is the mix of all the boundary that determine the center frequency of the cancellation because in a small room all boudaries are close enough to always play a role in the equation.
But if we move only in one direction, for example: far away from the front wall (so closer to the back wall) is it the relation between these too walls and the test position which will fix the Center Frequency or will the new position in relation to the other walls change that anyway?

[Jens Eklund]

Originally Posted by PaulRain

Ok it's clear that is the mix of all the boundary that determine the center frequency of the cancellation because in a small room all boudaries are close enough to always play a role in the equation.
But if we move only in one direction, for example: far away from the front wall (so closer to the back wall) is it the relation between these too walls and the test position which will fix the Center Frequency or will the new position in relation to the other walls change that anyway?

SBIR
SBIR

[avare]

+3! Great tests and great reporting. Thank you Dan.

Andre

[DanDan]

Ok it's clear that is the mix of all the boundary that determine the center frequency of the cancellation because in a small room all boudaries are close enough to always play a role in the equation.

Well the size of that 'role' seems to vary a lot and not intuitively. IMO certainly enough to warrant separate identities to the boundaries to prioritise treatment.

A Real test in a Real Room shows the Back Wall contributing a lot more BIR than it's distance would suggest. SBIR

On the other hand FWBIR can be pretty much eliminated by moving the speaker very close to wall with an absorbent panel between.
SBIR

I have another test with the speaker in a tricorner, equidistant from all walls.
When moved towards one wall, keeping the others the same, the combined null does appear to shift frequency. So I guess the influences kind of blend together in that close instance.

DD