Stuart, your waterfall recommendations?

Stuart hi, I have often read here you advise people to show a 40db range on the vertical scale of a waterfall graph. Many say it needs to be minimum 60db above the noise floor to have any real meaning. Your thoughts?

I have often read here you advise people to show a 40db range on the vertical scale of a waterfall graph. Many say it needs to be minimum 60db above the noise floor to have any real meaning. Your thoughts?

Exactly! :) That's two entirely different things you are talking about. One is the way you VIEW the data, and 40 dB of vertical scale below the average seems to be a good compromise for most cases. You can generally clearly see modal issues by viewing the top 40 dB of the decay. The other thing is how the measurement was taken: There, indeed, you would hope to have 60 dB of headroom above the noise floor, in an ideal situation. Inside a well isolated studio that should be possible, but you'd need to be producing levels up around 90 or 100 dB to do that. Fortunately, REW doesn't actually need to see a decay of 60 dB to come up with accurate results, but ideally it would be good to give it as much as possible. So yes, 40 dB of view below the test level, and 60 dB of headroom are good rules of thumb. - Stuart -

ThanksStuart, So to summarise and maybe simplify, Run the test at 85db, and size the vertical scale for say 45 - 85db and were on the right track? Sorry, having bit of a hard time with this one for some reason, :shock: :D To hit 90db Id be getting a bit worried about damaging the monitors. Cause for concern?

If you run the test at 85 dB, then I'd set the top to 100 dB, since there might well be modes that go up that high. Then set the BOTTOM to about 40 dB for a typical room. You can always change it a afterwards if you can't see thins clearly. This isn't a "cast in stone" rule that you have to follow religiously always! It's just a good place to start from when you are viewing your waterfall, and then re-adjust things as necessary, to better see the response. Or post your MDAT file here, ... - Stuart -

Thank you very much Stuart. I will be posting all measurements in the next couple of days and would appreciate you casting your wise eye over them.

No problem! :) - Stuart -