trace arithmetic and average the response - Home Theater Forum and Systems - HomeTheaterShack.com

Old 04-27-15, 06:43 AM Thread Starter
Shackster

Join Date: Feb 2013
Posts: 11
trace arithmetic and average the response

Hi all, I have a question: what is the difference between the trace arithmetic function A+B and the button at the bottom left of the graphic named average the response ? The graphs are very similar but with different values, is it a geometrical average ? Also, what is the difference between A+B and merge ?
angeloconto is offline

Old 04-27-15, 08:15 AM
Elite Shackster

Join Date: Mar 2009
Location: Michigan, USA
Posts: 1,368
My System
Re: trace arithmetic and average the response

The 'Average' only operates on the SPL values. The 'A + B' complex average considers both the SPL and phase.

'Merge' allows combining 2 measurements at a frequency of choice.

The REW 'Help' has additional info both these features.

JohnPM, I noticed that REW Help/Search took me to the correct help page but highlighted random text rather than the text of the search. I hadn't had this issue before. Possibly the new v5.11 release developed a small bug?
jtalden is offline
Old 04-27-15, 12:27 PM Thread Starter
Shackster

Join Date: Feb 2013
Posts: 11
Re: trace arithmetic and average the response

Thanks jtalden,
so the reason why the plots are different is that in the 'average' calculation the phase is neglected ? I mean, if I do 'average' and 'trace arithmetic (A+B)/2' of the same two measures then the resulting plots have different 'scaling' of values. I upload some image that could be helpful to explain.
And, what do you mean by 'combining 2 measurements', what is the mathematical operation ?
Attached Thumbnails

angeloconto is offline
Old 04-27-15, 04:51 PM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,301
Re: trace arithmetic and average the response

Yes, average is magnitude averaging, trace arithmetic uses vector arithmetic, magnitude and phase.
JohnM is offline
Old 04-27-15, 07:21 PM
Elite Shackster

Join Date: Mar 2009
Location: Michigan, USA
Posts: 1,368
My System
Re: trace arithmetic and average the response

'Merge' allows pasting together 2 measurements at a frequency of your choice. If you experiment with it you will see what it does.

If you have the situation where you need it, it is very handy. Only relatively advanced users would likely have the need. I have used it to paste together an average of near field measurements of my main speakers with an LP measurement of my SWs to clean up the phase response. That can be helpful when making a phase correction filter. There are other uses as well. Others use it to paste a SW port response to the SW driver response, both taken with the mic at ~1cm distance. That is of no value unless you are trying to determine the anechoic response of a SW, but need to do it in a room. Some research on the web can find details of this technique.
jtalden is offline
Old 04-28-15, 10:06 AM Thread Starter
Shackster

Join Date: Feb 2013
Posts: 11
Re: trace arithmetic and average the response

Thanks JohnM and jtalden. So, 'merge' means to split two measures at fchoice and take one measurement for f<fchoice and the other for f>fchoice, is that right ?
angeloconto is offline
Old 04-28-15, 10:12 AM
Elite Shackster

Join Date: Mar 2009
Location: Michigan, USA
Posts: 1,368
My System
Re: trace arithmetic and average the response

.
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