Here's 4 LMS-18's with 10kW @ 2-ish ft.
It hits 117db @ 10hz @ 100% THD (5th harmonic), and about 120db @ 10kW.
(There was about near-0% THD when I first started the vid.)
Here is one LMS-18 getting 4kW with Bass I Love you, near-field. Those 7Hz tones are hitting about ~70mm's P-P here (out of 80mm's):
The TermLab is calibrated at the factory, it's solid-state, no moving parts, no mechanical limits and nearly impossible to tamper with. If it says you got X spl, then you got X spl at that distance. Which is kind of nice, no calibration needed and you know the numbers are legit.
I also double checked my CM-130 and UMIK and TermLab, they all match each other. Further confirming that my SPL numbers are accurate. I recommend the CM-130 as a handheld, it's pretty accurate, though limited to dbA or dbC (dbZ handhelds are expensive as hell!)
The UMIK itself hits like 10% THD by itself at around 120dbZ(S)-Max; and minimal THD at 115dbZ, so I recommend not running THD sweeps with it higher than that.
The TermLab and SPL Lab being solid-state, has no mechanical THD, all the way to >180db.
(But they do have noisefloors.)
I wouldn't trust the TermLab below 105db, it's too noisy down that low.
At least the V2 analog version I got, the new Magnum digital is supposedly better at low SPL stuff.