| Interesting
Many of us have expressed the opinion that the floor bounce could not be the only mechanism at work here. However, let us not forget that the OP stated clearly that the frequency changes with listener distance.
On the basis of the frequency change, we went with his idea that the floor bounce was the most significant cause.
Then some of us suggested remedies.
Mine was a catch-all, make the best of it, which would address the dip irrespective of it's component causes.
SAC proposed that a broadband absorber in the reflection path would diminish the reflection enough to alleviate the dip somewhat.
I simply cannot see how this would happen. I do not think a MiniTrap or other panel in the path of a 135Hz wavefront, would drop the level by the required 10dB or so. My test appears to confirm this view.
I would have thought that third octave pink and an SPL meter were quite valid, in terms of what the ear would actually hear. i.e. no change in the frequency response, no alleviation of the dip we are interested in.
I would welcome any views on that one way or the other.
A fascinating issue has arisen now. Lupo's test shows an alleviation of the dip, in the case of the fibre, but strangely not the foam.
If this test is valid it is surely good news. Could we extrapolate that a mere 10cm of Rockwool, no gap, is enough to diminish SBIR dips?
Again, I find it very difficult to believe that it would.
I will try to duplicate Lupo's test.
Lupo, nothing was changed when generating those graphs right? e.g. You have previously shown how manipulation of the window can result in different FR graphs.
DD
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