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Need help with multitone measurements

Toltek

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Dec 12, 2019
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I am trying to figure out how bad my 25 year old speakers are and have some questions about multitone tests I did in REW, using UMIK. I measured on tweeter axis at 1m at several levels in 10 db steps, the reading from REW was 68, 78, 88 and 98. Even with earplugs and short measurements interval it was pretty loud.
The resulting distortion was raising with each increase, and was really high for 98 db SPL. For clarity I only plotted 68 and 98 dB results
Speakers MT 68 98 dB.jpg


However, if I normalize to the same level, amount of distortion kinda looks the same
Speakers MT 68 98 dB shifted.jpg


So my question is: are my speakers equally bad at low levels too? I usually listen at 70-80 dB average and I like the sound a lot.
 

RandomEar

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I'm not that familiar with REW. But in this case, it looks like you're comparing distortion at 98 dB to (essentially) the noise floor of your measurement at 68 dB. Therefore, I'd say the comparison made by just shifting everything down by 30 dB is simply invalid.
 
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Toltek

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Thanks. Does it mean that noise is a bigger problem in my system?
 

RandomEar

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It's not clear to me where the noise is coming from. Maybe the microphone, maybe the environment. But if there's lots of noise in the reference measurement and your system wasn't playing anything during that, it's not coming from the system.

Also, those look like multitone measurements before evaluation - if the distortion is similar between those measurements can only be determined reliably by looking at the evaluated distortion curves.
 
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Toltek

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I measured it in the room, not in an anechoic chamber, so I guess I have to live with that high noise.
 
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