Mazda Talk Forums

Something totally NEW in NC Exhausts!

Dare I say....a serious REVOLUTION in NC exhausts!

Now shipping, an NC Midpipe with a giant Helmholtz chamber. What does that chamber do? Notice it is not inline like classic glass pack resonator but sits to the side and is connected by what amounts to a special valve. This chamber and the valve are tuned with computer software after driving the NC with a sound spectrum analyzer hooked to a computer using some special software. In brief, this technology has never been applied to a Miata exhaust before and what it does is allow us to attack the drone frequency range of 120-130 hz in a way we could never do before, with result we get nearly 50 db reduction in that range...which is MASSIVE reduction. The reduction is much more mild over more broad range. Bottom line effect is ALL THE FUN sound is allowed through, not the boomy drone!

Nonetheless, this midpipe is NOT for everyone. Why? Because of the focused nature of this resonator this midpipe is very dual personality, overall LOUDER than our standard midpipe, yet much more quiet than our standard midpipe right in the range of drone/boominess. In other words, it's a ton more fun sound, without the bad sound, but it's still a lot more sound! Thus, not for the timid...but a massive amount of fun and the result is the most exotic sounding MX5 we can offer.

What would this do to a stock system with a Street Single on it? And I don't see it on the store web site.

Here is the DUAL PERSONALITY effect....both LOUDER AND QUIETER than what you hear now....depending on what you do with the gas pedal.

LOUDER and more exotic sounding when on throttle....but QUIETER and more mild when cruising and off throttle and going down hill, light loads, etc. The factory glass pack in the factory midpipe and our own brand midpipes is a blunt instrument, it reduces all frequencies by roughly similar amounts. This special Helmholtz resonator is a focused attack on the 'boom' or 'drone' frequencies and it cuts those by much more decibels than the factory midpipe, or our standard RoadsterSport midpipes. So, the idea is more of the fun...and less of the part you don't want. But the non-drone frequencies come through at higher volume.

It just posted to the online store at THIS LINK, it will take a few hours to be visible all over the Internet.

This is the most exciting thing to come out for a while -- I've wanted to try this technique for years! Two thoughts, though. First, the ad desperately needs A-B sound clips. I'm sure you're working on that. Second, you should add a support at the far end of the resonator, so vibration and leverage doesn't break the welds at the near end.

And then you need to build one for the PPE headers I bought from you!

Glad you like it. You may not be able to see it easily in the pictures above but stout support ring of the Helmholtz chamber right after it makes the 90 degree connection. Likely you can see that support ring in the pic below. Connecting the chamber again at the far end would result in almost instant weld break because of differential expansion. As always, our lifetime warranty covers the buyer.

Agree this is the most exciting NC exhaust product in quite a while! Like Jim, I've been dying to try a Helmholtz resonator to help with drone, but never had the resources to develop one.

Now I just need to figure out whether it can be adapted to work with the PPE long tube header. I wonder if one could create a Franken-midpipe by cutting this one just downstream of the 2nd O2 sensor bung and welding on the PPE cat and flange to get the best of both worlds.

Beautiful!! I'd like to hear back to back to back comparisons of OEM Mid - Resonated Mid - Hemholz Mid with a RoadsterSport 2 on the back

njaremka wrote:Beautiful!! I'd like to hear back to back to back comparisons of OEM Mid - Resonated Mid - Hemholz Mid with a RoadsterSport 2 on the back

Thanks for the feedback guys. I will get some videos up when I get the chance. It is going to revolutionize my recommendations. Prior to today I could never recommend a performance header be used with any muffler other than our RoadsterSport SuperQ muffler. Now I find choices like the Street Single and RoadsterSport2 can be fun with a performance header in a way they were not before because those units could not kill the drone coming down the system.

I did spot the support ring, but I question whether it's enough. Time will tell I guess. When do you figure on posting sound clips?

jboemler wrote:I did spot the support ring, but I question whether it's enough. Time will tell I guess. When do you figure on posting sound clips?

You and I could both hang from that bracket, laser cut stainless plate used on end with over a quarter inch to half inch of meat for support at all points, it's massively overkill...and will hold the 3 pound Helmholtz chamber for a million years.

Yes, will get some videos going when we can, been crazy here with projects lately.