While I don't agree with everything Grimani says, the following interview is worth watching, since it includes much of the placement discussions we've had in this thread:
Wow, guys, I take a few hours of to go to the fitness center and a posting bomb goes off! I can't tell whether everything has been resolved, or whether there are still issues.
First of all, the procedure to calibrate the mic in REW using an external SPL should not be that difficult. Does any confusion remain?
Second, WRT the settings for the Waterfall graph, I opened my REW app on the laptop, and the Waterfall settings I am using are not the default settings in REW. Here are my current settings vs. the default settings.
TBH, I don't know how I ended up with different settings, and also don't really understand how the settings make a big difference. Here are two waterfalls generated from the same underlying measurement, one using default settings, and the other using my current settings:
So, what is the big difference, as long as we are using consistent settings to compare one waterfall against another for our own systems? Question for the team: should I edit the Guide and put in the REW default settings if this is what everyone is using?
The important things about the waterfall, IMHO, are:
- Setting the noise floor properly (which we consistently see as ~50dB when using USB mics).
- Taking measurements at least 35-40dB above the noise floor (I calibrate my mic to 90dB).
- Setting the horizontal axis to 20-300Hz (5Hz-300Hz for Keith )
- Adjusting the time window such that the resonances have fully decayed below the noise floor (300ms in a really good room, 450-600ms in a more typical room).
Have I missed anything?
I'm never going to the fitness center again....
I don't think it matters which set of standards we apply (the only change the way the data is displayed as you say elsewhere) so long as we agree one set and then use them exclusively unless there is a good reason not to, occasionally. I am happy with a noise floor of 50dB if that is what most are getting from their USB mics - not much point going lower is there?
FWIW, this is what my last waterfall would look like using the REW defaults, a 450ms time setting and a 50dB noise floor:
TBH, I am happy with a waterfall like that and would consider my work as complete, unless someone says this set of parameters (see below) is bad for one reason or another. I don't use 300ms because, for me, there seems little point, as I cannot move the speakers or subs to any more optimal location and I cannot really apply further treatments to try to deal with ringing below 25Hz. The bass sounds good and tight right now, so, without wanting to appear complacent, I am happy.
For the sake of completeness, here is the data with a 300ms setting:
Thanks J. Yes, I am aware of that issue at about 60Hz but IDK what I can do to fix it. I have standard GIK bass traps in pretty much every corner I can (wall-ceiling, wall-wall, wall-floor). I could maybe squeeze in more if I had them custom made to fit the 'odd' sizes remaining. If anyone has any suggestions I would be very grateful and willing to try them.
Good point. The fridge will be on, and may well be running. Heating could be or not - I've never thought about it before. Next time I measure I will switch both off and see if it makes a difference. Thanks.
Good catch, Jerry. You are, of course, correct.