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Hi. I am trying to get my head around which conclusions can actually be made from measuring a speaker in-room. I have this thought experiment, which I'm not at all sure is even possible in the real world. I'm quite new to measurements, so I don't really have a full understanding of everything. Anyway:

What I want to achieve is to create some sort of plot of a speaker's THD vs. Frequency, at varying SPL's. My thinking is that I would like to find the level at which a particular loudspeaker reaches its limit, and starts to distort noticeably. I'm not really concerned about what the level of distortion actually is, so accuracy in that regard isn't actually important. I just want some way to find the level where the distortion (or compression or whatever issue I should expect to be the limiting factor?) kicks in.

If I just deliver sweeps at increasing levels to a loudspeaker, at some point I start to hear breakups of varying kinds (which I gather is potentially dangerous to the loudspeaker, but I will thread lightly...) However, I'm not sure which kinds of graphs I would need to create to get some kind of meaningful measurement of this - or if it is even possible. Do anyone have inputs on this?
 

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REW v5.01 Beta 17 has a Distortion/Freq chart.
I would expect the 2nd and possible 3rd harmonic to increase rapidly when a driver is driven outside its design SPL. It is possible to increase the SPL with successive measurements and note the resulting impact on distortion and any freq of interest. As distortion or compression start to significantly rise it would be prudent to stop there. There is not value in damaging a driver. If you are actually hearing a distortion I suspect the distortion is well into the danger area.

I don't know of any automated way to combine this into a single "SPL/Distortion/Freq" chart automatically. I believe this would require some manual effort in another charting program.
 
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