Originally Posted by corradizo
Yes. When measuring my basement system, I was measuring with the MV at 0db or 105db which I thought was the norm since my noise floor is around 45db. My understanding is you want to measure 60db above the noise floor.
I questioned the reasoning behind measuring 60db above the noise floor of 45db which is 105db in my case, but blindly measured at that level because I thought it was generally accepted as best practice. I don't listen at 60db above the noise floor, I listen at -15 which like you said is 90db. So, should i be measuring at the volume i listen at and treat the room based on the ringing that exists at my preferred volume? I would think it would take longer for 105db to decay compared to my preferred 90db. I hope I'm making sense. :-)
Let me summarize what I think:
- The measurement level is not critical. Read the posts by JohnM again.
- Nowhere that I am aware of is there a recommendation to measure 60dB above the noise floor. I believe the recommendation in the guide is 40dB above a typical noise floor, which is 45-50dB, which would make the recommendation for the measurement level to be 85-90dB (but not critical--see point 1)
- As stated in my previous post, if you want to measure close to your average listening level of -15, that suggests a measurement level of 90dB. Matching the measurement level with your typical listening level is most important for the distortion graph, IMO, since distortion increases with output level.
- For the waterfall, the most important part of the graph is the first 20dB below the measurement peak. Set the measurement level such that the first 20dB is clearly visible before disappearing into the noise floor. For the typical 45-50dB noise floor, this suggests a measurement of at least 75-80dB for the waterfall.
Having said all that, the first thing I do during a REW measurement session is adjust the level to 90dB so that my measurements are consistent from one session to the next. Consistency is important to me, whether it is 80, 85, or 90dB