B-Quiet Vcomp:
Cost PSF (40.5 SF+ order): $4.07
Weight: 1 lb / SF
Thickness: 0.375 in (9.525 mm)
Frequency (Hz) & Associated TL (transmission loss in dB):
0125 - 15
0250 - 17
0500 - 21
1000 - 28
2000 - 34
4000 - 37

B-Quiet Lcomp (OUT OF PRODUCTION):
Cost PSF (40.5 SF+ order): $9.50 (!)
Weight: 1 lb / SF
Thickness: 0.500 in (12.7 mm)
Frequency (Hz) & Associated TL (transmission loss in dB):
0125 - 17
0250 - 21
0500 - 24
1000 - 32
2000 - 34
4000 - 36

 

The people who are trolling are giving the best advice. An Evo will never make you happy if those are the qualities you value in a car. Just wait until the rattles start and you will go mad.

 

I also have a minivan with 2 child seats in it and bikes, etc., and thus I am quite immune to rattles at this point... The drone is really my primary issue with the car -- I am quite willing to forgive everything else for its unique strengths.

 

"Drone" or what the OP is calling "sub-sonic" (Yes that's the right term, lower than 20hz and the human ear can't hear it, but still gives you a headache) is a problem with the resonant frequencies of the exhaust gasses+the exhaust tubing itself.

Resonance is sound waves being in phase with each other and amplifying each other at a certain frequency.

You can have an extremely quiet exhaust with lots of drone and it will give you a headache.

You can have a very loud exhaust and have 0 drone/resonance and it would be fine for the passengers.

To the OP,
I replied to your other post already, but you can have a free flowing performance exhaust and just get rid of the resonant frequencies that create droning by tuning the resonance out with a different or additional resonator inline.

 

Subsonic is a term made up by the audio market to make jargon more palpable to the uninitiated. What you're trying to describe is called "infrasonic." This being said, the drone in an exhaust is way (at least an octave, if not two) above 20Hz.

FWIW, that's typically referred to as a sympathetic resonance.

dB-what? Typically, exhausts and the like are measured A-weighted, ie. dBA. That's fine and dandy if you're measure the SPL of a punch press in a factory, but the filtering completely omits low frequencies, the exact area where drone takes place. This is why it's not unusual to hear a muscle car with a loud rumble from the factory that still meets noise guidelines. dB-A numbers are meaningless in this application.