High level compression sweeps

Im attempting to do high level compression sweeps with a new pair of speakers to measure performance up to reference level of 105 dB. I've measured my subs with a windows laptop to above 115 dB with no issues, but have just switched to a Mac as the windows laptop has died. I get up to the 85-90 dB sweep level with one of my speakers, at which point I start getting a warning that I am clipping the input. Distortion on this sweep is mostly around 1% and lower so I am well below maximum output capability. Is it possible that the SPL is actually much higher than what is being recorded? Attempting a higher level sweep than this actually shuts down the measurement due to excessive clipping(of input). I am using a Umik-1 mic just as for the subwoofer sweeps, which I have not repeated on the Mac yet. Calibration file has been downloaded.

Any thoughts or suggestions? I've thought about getting a decent SPL meter to compare output levels to see if there is indeed a false reading.

Thanks very much I’ll give this a whirl tonight!!

Mispost

John Mulcahy said:

Check in Audio Midi Setup (Applications/Utilities) to see what the input gain setting is for the UMIK, need it at 0 dB to use the full input range of the mic. If volume is set to max gain will be +24 dB, reducing headroom correspondingly.

Click to expand...

Was a little tricky to figure out where to go to turn the input volume down(System Preferences/Sound) on the Umik-1 mic, but once I found it I saw that the volume was turned all the way up. It didn't show a dB level. Turned it down and had much higher headroom on the mic when doing sweeps. However, I still think I may have a false SPL reading as I only got to around a 90 dB sweep before some notable distortion and compression set in, and things seemed VERY loud.

In fact, full compression set in 6KHz+ at 87-90 dB, which is very far below where the speakers should be capable. This is possibly 20dB low...which is why Im afraid I'm just getting an incorrect SPL reading. I'll try some sub sweeps tomorrow to see where I sit as I have a good baseline on those. If I'm 15-20 dB off I'll know.

Top sweep I did was ear shatteringly loud(covered my ears of course), so its hard to imagine it was only 85-90 dB.

John Mulcahy said:

The Audio Midi Setup application (in Applications/Utilities) shows the gain in dB. Is the UMIK selected as both the input device and the input? Which REW version are you running? Some macbook users on Mojave have found that the input signal comes from the internal mic even when an external mic has been selected, if you have a macbook with an internal mic check for that.

Click to expand...

Are you saying the "Audio Midi Setup (in Applications/Utilities)" is a menu on the Mac or within the REW program? Because I don't see any menu or command of this name. I found volume control for the mic on my Mac under "System Preferences/Sound".

REW is 5.2 Beta 10

As far as the Umik-1 being selected as both the input device and the input. When I go into preferences within REW, on the sound card tab, the input device is "Umik-1", but input says "microphone". The only option to change this to is "default input".

When I click the "measure" button in REW to perform a sweep, the input tab on this menu says "microphone" with the only other option being "default input".