BASSBOSS Questions
On your LMS graphs, you are stating 1m ground plane. Please, can you tell me how many meters from the sub speaker cabinet you are taking a reading from and where exactly is the mic position?
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David Lee
The LMS measurements are taken at 1M for small boxes and 2m or 4m for large boxes. The mic is on the ground, the cabinet is on the ground. 4 ohm loads are measured using 2V, not 2.83V. 2-ohm loads are measured at 1.41V, not 2.83V. When measured at 2m, 6dB is added to correct for the distance. When measured at 4m, 12dB is added.  
 
It’s not just about 1W 1M, though. We don’t simply measure and publish 2V or 1.41V measurements because they always look good. The purpose of the 2V measurement is to establish sensitivity. We then measurements at higher power levels, such as 20V, to provide a more realistic representation of the signature of the loudspeaker. The SPL is then corrected down to compensate for the added voltage.  
 
Since LMS is an analog system, and uses a swept sine wave, measurements at greater distances can be influenced by reflections. Using a digital system allows the reflections to be windowed out but also has very low detail resolution at low frequencies.
 
Thanks and best regards!
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