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Discussion Starter #21
5# axle back setup. Quieter than RB but deeper sounding. Nice weight saving. Has less restriction than before might help performance a bit we'll see. Sound from about 5 feet behind the car. Next to the car you hear the engine's mild rotating sounds and the deeper exhaust tone. Has no-drone and S/B easily track legal for sound restricted venues. 2 1/2 inch straight-thru with side branch resonator plus DIY "resonator" (absorptive). I may adjust it to be a bit louder, especially below 100 hz, without changing the mid and high frequency attenuation characteristics (those are the ones that trigger SPL black flags cuz dBA scale is used which deemphasizes the lower frequencies). It's way quieter than many setups, but I tried to keep the deep and lower restriction to ~nothing.

http://picosong.com/TF64

 

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Discussion Starter #22
My old exhaust was a Racing Beat Power Pulse with resonated mid-pipe. At idle per RB they do 74 dBA measured as noted here:

http://www.racingbeat.com/Miata-1990-2005/Exhaust-Components/56436.html

I'm at 71-72 dBA in the clip above. Clearly quieter than the RB @ 74. RBs are not known for being overly loud. So when I get a chance i'll reconfigure my DIY resonator a bit differently. I'll raise the dBs slightly while adding some more deepness to the tone below about 100 Hz which is below the drone-zone.
 

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Discussion Starter #23
This is interior sound, windows closed average of WOT in the midrange RPMs. Blue-Green trace is exhaust only. White trace is where I reactivate my interior sound tube from the ITB plenum. This way you can have any amount of ITB sound (or none) and still be event SPL legal. Even makes the air sucking sound if you gently accelerate...just like carbureted engines do.

 
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