Here's a suggestion. You may be experiencing a false reading on your SPL meter for the center channel if you point the microphone straight ahead (parallel to the floor) when taking your reading. To obtain the most accurate reading, try pointing the microphone up at roughly a 45-degree angle so the meter measures a blend of direct/reflected sound from all speakers.
For best results, I position my SPL meter at the listening position on a camera tripod (at ear level, pointing up 45 degrees). I stand beside the meter a few feet away during the test tones because even holding the meter too close to your body can reflect sound back to the SPL meter's microphone and distort the reading.
Good luck!
For best results, I position my SPL meter at the listening position on a camera tripod (at ear level, pointing up 45 degrees). I stand beside the meter a few feet away during the test tones because even holding the meter too close to your body can reflect sound back to the SPL meter's microphone and distort the reading.
Good luck!