SPL testing / mock Finals measurements

OK chaps, next item for discussion is the Audio Control meter and how changes in the dB range setting affect SPL scoring while trying to "mimmick" the scores of certain few cars at Finals and produce results consistent with the notion that USER ERROR was the cause.

READY, here we go

BASELINE MEASUREMENT: 136dB standard "LO" level microphone positioned in standard fashion on 26" tall mic stand in the listening position, driver's seat.

NEXT, I switched the meter on, set sensitivity to ZERO and dB range to 120dB (as per the rulebook for standardized SPL testing).

NEXT, I press and hold the SPL button and release it when it reads "LO", indicating I have the 136dB standard low-level mic in place and ready to go.

NEXT, I note the reading with the vehicle closed is "UND" or "under" the measurement threshold. TO give the benefit of the doubt, rather than do a "peak hold" run of 30 seconds like a standard judging test, I left the meter to read real-time averaging reading and noted the highest decibel reading obtained on the screen as I sit in the vehicle and watch the meter. OK, cool.

NEXT, i throw in the IASCA disc, cue up track 30, and let her rip 3 different times.

SCORE 1- 134.4
Score 2- 134.1
Score 3- 134.0

All within minutes of each other (hence the progressively lower readings from dropping batt voltage)

THese findings are right on par with our scores at finals in RTA lane 2 with KEith and Eric. Good job boys!

ok, the next scenario to the test is do a quick RTA measurement, following the sensitivity setting guidelines and 90dB range setting as posted in the RTA thread, LEAVE THE SENSITIVITY WHERE IT IS, but switch BACK to 120dB range and measure SPL again. THis will test the argument that the sensitivity was tampered with.
I did so, and the setting I ended up with was approximately +9 dB during RTA, so thats where I left it, set range back to 120dB, and repeated the above>>>>

Score 1- OVR
Score 2- OVR
Score 3- OVR

WAIT! WHats this "OVR" thing??? Well, that means the level is too high for the range selected, and the microphone is what they call "saturated", meaning you are "OVER" the effective measurement range of the lo-level microphone.
Hmmm, OK, well this proves that the judges could not have left the sensitivity setting as it was adjusted for RTA and then scores SPL in the 120dB range setting. Let's try leaving the range set to 90dB>>>

NEXT, range set to 90dB, sensitivity left in position at roughly +9. Here are the scores>>>

Score 1- OVR
Score 2- OVR
Score 3- OVR

WOW! So now the argument that the judges did it wrong by NOT changing the dB range to 120 doesnt hold water either because the microphone is again saturated and we are well above the effective range of the 136dB mic.

OK, so for the sake of argument, I did another run leaving the RANGE set at 90dB, but this time returning the sensitivity to ZERO, just in case this was the scenario that some of the competitors said they witnessed.

Score 1- OVR
Score 2- OVR
Score 3- OVR

Basically peeps it's like this, I have proven that the claim that sensitivity and/or dB range selector being improperly "tweaked" by the judging staff could not have possibly been the cause of the poor readings! It is simply NOT possible (please see the above).

TO give further benefit of the doubt I will research how the audio control "resets" itself for testing and if an ambient noise level being present at the start of testing affects the "peak-hold" reading function of the lo-level microphone.
I will also simulate an outside ambient noise floor of +6dB with the system in my garage (yes folks, I have a full system with 2 12's in the garage where Jorge's truck is currently residing, and it gets STUPID loud off Autotek power!!! ), and then re-test for both RTA and SPL and post the findings.
THe ONLY way that this will prove to affect SPL is going to be that there actually IS some way that an ambient noise floor affects the threshold of the meter or mic at the beginning of testing in an adverse way. I will do this test tomorrow and post findings....

In the end, I cant help but mention that arguing car audio competition aspects or audiophile system design with Uncle Audio is like arguing slew rate , doppler distortion, or audibility of DA conversion with Sir Wolfie or Kev7909----YOu wont win, but we will all learn something from the discussions LOL! I LOVE IT and this is why I love this forum. Thanks for pushing me to "prove" myself, gents.

More later