Some of you may be familiar with this really long thread on the corral and others like it, which detail the science between adding capped resonator pipes branched off the main exhaust that are exactly 1/4 of the length of the soundwaves of the "drone zone". The idea being the sound wave enters the capped pipe and bounces back so that when it gets back out, it's exactly 1/2 a wave out of phase, so it meets the next pulse in the system head-on, totally cancelling it out. I can't do this on my mustang because the aftermarket suspension components leave me no room to add teh extra pipes. I've added Dynomax VT mufflers to it, which work, but I just bought a Pontiac G8 GT with a Magnaflow exhaust that droned like crazy at 1900 RPM, 125 Hz, but otherwise sounded great. I didn't want to change it, I just wanted to kill the drone.
The G8 folks are hip to the phenomenon, and a company called SOLO makes a catback that incorporates adjustable-length capped J-shaped pipes that mount back by the mufflers. It's important to note that the phenomenon doesn't care where the pipes are mounted, or how they're shaped, just how long they are. It just so happens that there's a perfect spot for them on the G8's platform back by the mufflers near the bumper. These ones are adjustable kind of like a trombone, but they come pre-assembled at the perfect length. I had them installed yesterday, and the difference is incredible. And measurable
As seen by this screen shot from my handy-dandy sound meter app on my iphone, the big hump in the 125hz range is the drone:
I don't have any sound files, but the meter tells the story: Same RPM, same stretch of road, same time of day. Look how much smaller that hump is, and look how many fewer decibels it's reading. That 10-decibel difference is huge. The way the decibel system works, every 10 decibels higher means twice as loud. That means the old setup was twice as loud as the new one, or put another way, the new setup is half as loud as before. :
The drone has been virtually eliminated, and I'm a happy camper. This
The G8 folks are hip to the phenomenon, and a company called SOLO makes a catback that incorporates adjustable-length capped J-shaped pipes that mount back by the mufflers. It's important to note that the phenomenon doesn't care where the pipes are mounted, or how they're shaped, just how long they are. It just so happens that there's a perfect spot for them on the G8's platform back by the mufflers near the bumper. These ones are adjustable kind of like a trombone, but they come pre-assembled at the perfect length. I had them installed yesterday, and the difference is incredible. And measurable
As seen by this screen shot from my handy-dandy sound meter app on my iphone, the big hump in the 125hz range is the drone:
I don't have any sound files, but the meter tells the story: Same RPM, same stretch of road, same time of day. Look how much smaller that hump is, and look how many fewer decibels it's reading. That 10-decibel difference is huge. The way the decibel system works, every 10 decibels higher means twice as loud. That means the old setup was twice as loud as the new one, or put another way, the new setup is half as loud as before. :
The drone has been virtually eliminated, and I'm a happy camper. This