No Repeatability

[sparkgap]

Hello all!

Really enjoying learning to use REW but I am having some repeatability issues.
If I run repeated measurements they don't come out the same, specifically in the 10-40 Hz range, plus a few spikes in the 100 to 500 Hz range tend to pop in and out.

If I use a loop-back (and no cal file) all is well.

I can't see how I can set up my sub if I can't get consistant results.
the plots are:
green=looped
and three consecutive measurements with C weighting and the correct cal file for my SPL meter.
Thanks!
Tom

[JohnM]

Can't clearly make out the scaling on the graph, but it looks like the overall measurement levels are low and that there is actually little output below 40Hz so what is being measured there is mostly background noise, hence the inconsistent results. The spike at around 120Hz might be a mains hum component.

[brucek]

Yeah, the loopback test shows about 63dB I believe, so the actual measurements are below that and too low.

Take your measurements at 75dB and you'll have very repeatable results.

brucek

[sparkgap]

Thanks for your responses!
Yeah, level was about 63 dB. I'll try higher. I also read the thread on how to post graphs, so I'll do better if I post more.

Tom