Home Theater Forum and Systems banner

1 - 9 of 9 Posts

·
Registered
Joined
·
178 Posts
Discussion Starter #1
I was using the REW SPL meter to get a peak reading of a particular movie scene. I set the meter to C weighting and fast response.

I noticed it gave two peak readings; LCFmax and LZpeak.

What do these mean? Which one do I use?

Btw, the scene I was checking was the "Darla taps aquarium" in Finding Nemo. With my processor set to -3.5, I was getting these readings;

LCFmax 106.9
LZpeak 113.8

It was very loud and felt like the whole room was shaking. :eek:
 

·
REW Author
Joined
·
6,711 Posts
LCFmax is the highest level seen in the C-weighted, Fast (125ms) filtered measurement.
LZpeak is the peak instantaneous value seen in the input with no weighting and no filtering.
 

·
Registered
Joined
·
178 Posts
Discussion Starter #3
LCFmax is the highest level seen in the C-weighted, Fast (125ms) filtered measurement.
LZpeak is the peak instantaneous value seen in the input with no weighting and no filtering.
Thank you.

So in terms of how we hear, would the C weighting figure be the appropriate number to use? How about in determining the output capability of my sub?
 

·
REW Author
Joined
·
6,711 Posts
So in terms of how we hear, would the C weighting figure be the appropriate number to use?
Better of selecting 'Z' weighting (i.e. no weighting) for a subwoofer as the C weighting curve rolls off below 31.5 Hz (see SPL meter help).

How about in determining the output capability of my sub?
Output level is best assessed using the CEA-2010 methodology, which applies limits to harmonics in establishing the max level when using a special test signal. REW's signal generator (in the V5.01 beta version) can produce a CEA-2010 test signal, this can be used with the REW RTA, which should be set up with FFT Length 65536 if running at 44.1k or 48k, or 131072 if running at 88.2k or 96k, in all cases with Rectangular window - the generator has a checkbox to loop the burst to make testing and capturing the results easier. You would need to do some googling or buy the spec to get the details of how to do the test though.
 

·
Registered
Joined
·
178 Posts
Discussion Starter #5
Better of selecting 'Z' weighting (i.e. no weighting) for a subwoofer as the C weighting curve rolls off below 31.5 Hz (see SPL meter help).

Output level is best assessed using the CEA-2010 methodology, which applies limits to harmonics in establishing the max level when using a special test signal. REW's signal generator (in the V5.01 beta version) can produce a CEA-2010 test signal, this can be used with the REW RTA, which should be set up with FFT Length 65536 if running at 44.1k or 48k, or 131072 if running at 88.2k or 96k, in all cases with Rectangular window - the generator has a checkbox to loop the burst to make testing and capturing the results easier. You would need to do some googling or buy the spec to get the details of how to do the test though.
Thanks. :)
 

·
Registered
Joined
·
281 Posts
Better of selecting 'Z' weighting (i.e. no weighting) for a subwoofer as the C weighting curve rolls off below 31.5 Hz (see SPL meter help).

Output level is best assessed using the CEA-2010 methodology, which applies limits to harmonics in establishing the max level when using a special test signal. REW's signal generator (in the V5.01 beta version) can produce a CEA-2010 test signal, this can be used with the REW RTA, which should be set up with FFT Length 65536 if running at 44.1k or 48k, or 131072 if running at 88.2k or 96k, in all cases with Rectangular window - the generator has a checkbox to loop the burst to make testing and capturing the results easier. You would need to do some googling or buy the spec to get the details of how to do the test though.
John, what do you mean 'buy the spec' ? Could you elaborate.
 

·
Registered
Joined
·
261 Posts
John, what do you mean 'buy the spec' ? Could you elaborate.
Brent Butterworth has a good overview on his site - http://brentbutterworth.com/cea-2010-bass-output-measurement-manual/

The idea is you play the tones at specific frequencies (12.5, 16, 20, 25, 31.5, 40, 50, 63, 80, 100, 120, 125) & raise the level until harmonic distortion breaches a given limit (-10dB for 2nd harmonic, -15dB for 3rd, -20dB for 4th and 5th etc). To produce comparable numbers, there are a set of rules you have to follow for how the measurement is done but I don't think that really matters for just checking what is going on in your room.
 

·
Registered
Joined
·
281 Posts
Thanks both. Interesting....

Matt- I'm working on tuning still, but when I'm done will give this a go using the information in the other thread too. Looks fun!
 
1 - 9 of 9 Posts
Top