Z Weighted vs C Weighted Umik-1 Waterfall Graph Results

[welldun]

Hello,
Question about the noise floor for the Waterfall Graph when using the Umik-1 in Z weight and Slow;
The noise floor for the room reads around 55db on the REW SPL meter with Umik-1 set to Z weight. However, if I select C weight on the same REW SPL meter using the Umik-1, the reading is about 10db lower. So which value should I use on the Waterfall Graphs to indicate the noise floor? I would think it should be the 55db since that is what the Umik-1 displays when set to Z weight, but I don't know if the Waterfall Graph is adjusted automatically to reflect a Z weighted reading?

With the default axis range for the waterfall set at 45db on the low end, there appears to be a lot of ringing. However, if I adjust the axis to 55db, the graph looks a lot cleaner with less ringing.

 

[John Mulcahy]

Ringing is not the noise at the bottom of a waterfall, it is the slow decays that start from peaks at the top. Where the noise floor is doesn't really matter.

 

[welldun]

Thank you, John, for the insight. I will hopefully get some graphs up soon. I seem to be having inconsistent issues while taking measurements. Sometimes I take a measurement and the thumbnail on the left will show that something registered, but the full-size graph window won't show anything. Then when I retake the measurement it shows up. This happens most recently while trying to measure the center channel +subs. At times I would get nothing on the graph, at other times it would only show the reading for the center channel speaker as if the subs were not engaged, and then at other times, it would give the full reading. All of these changes without physically changing anything, just simple retaking the measurement. I am going to reset my laptop and gonna reinstall REW to see if this helps.

Also, one other quick question about the TIming Reference Output speaker... Can it be one of the speakers that is being measured, or does it have to be a separate speaker? For example, if I'm trying to measure the subs, the mains+ subs, and the Center Channel speaker +subs, can I use the Center Channel speaker as the Timing Reference Output, or do I need to use one of the side surround speakers?

 

[John Mulcahy]

If you don't see a measurement in the graph window it is usually because it is off the top or bottom of the graph, outside the range you are viewing. To say why that might be happening I'd need to see an mdat file with some examples in it.

The timing reference can be any speaker which has a tweeter, including one you are measuring. If you want to compare timings between measurements they need to use the same timing reference speaker.