| Uncertainty
Hi Ethan, I think nonlinearity with SPL was probably mentioned as an interesting aside. I have no doubt that those posters know what they are talking about and I found the contributions a little intriguing. It is no surprise to me that things are a bit more complicated than they first appear. I mean we used to think the Speed of Light was constant, didn't we? Intuitively I doubt that the phenomenon is of enough magnitude to have an audible effect in the world of small studios, and even if it did, what could we do about it?
On the other hand I am very interested in the topic of LF measurements., in particular the variability we are experiencing. Several of us here experience that regularly. You have seen this yourself in ETF. Many overall results depend on accurate info in each band, e.g. rating of partitions, floors, etc. so I do think there room for improvement and discussion may help that along.
Personally, I find Decay spectra a lot more informative than Frequency Response graphs. I definitely want Decay information down to 40Hz.
FM uses the Sine Sweep also. It can perform what it calls synchronous averages. Each doubling of the number of sweeps adds 3dB to the S/N ratio. The method ignores once- off events such as cars passing or whatever, probably the same as REW. There is a MLS method (ETF uses it I believe) which some say is even more robust.
Even with all this, one rarely sees consistent EDT figures at LF. Now why is that, and can we improve it? For a start I suggest we stop use the term Decay time, rather than RT60 or even EDT. I like John's new notion of Topt.
B and K and others use Sine Sweeps also, but as I have said, when doing RT, they average several sweeps and each one is different. I have seen it. All these software packages are still extremely useful tools, particularly the Waterfalls which are the most reliable, but definitely room for improvement. John at REW in particular says he is working on new methods to look at LF. I look forward to that.
DD
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