Well I guess this is the most fitting place!
I helped my buddy install some nice subs in his car this weekend and I used our walmarts decibel meter to determine the decebile output of his new speakers, his brothers speaker, his brothers exhaust and my exhaust.
The new speakers (2 12" SPL's in custom fiberclass box) without tuning either of the 4000w amps hit 127.x dc. Mark later tuned Kyle's single 15" SPL up from 126.x to 131.x! We then measured Kyle's dodge Ram (318 aka 5.2 v8) at idle was around 90 dc and when revved maxed out at 117.x.
Now the good part! At idle, my trucks exhaust measured 117.x, and when revved with no load hit 128.x. The funny part is that from over 25 feet away while driving by I hit 115.x dc! Can you imagine what it would be if it was measured closer?
Point here is that my truck is as loud or louder then their bass!* LOL
*I bet there are MANY similar setups out there louder, but for in the driveway walmart decible reader style I was happy LOL.