This is from Bose when they announced the sound system for the ND Miata:

Today, Bose announces a new sound system for Mazda’s fourth-generation MX-5 Miata roadster. Redesigned and updated with newly engineered speakers and proprietary technologies, the Bose® system in the 2016 MX-5 delivers improved audio performance — optimized for driving with the top down.

“Through the years of our close collaboration with Mazda, we’ve witnessed firsthand how the MX-5 has become an industry icon with a loyal legion of owners and enthusiasts around the globe,” said Marc Mansell, vice president, Bose Automotive Systems Division. “So, we wanted to make the sound system for the new MX-5 better than it’s ever been. We improved audio quality, and for open-air driving, the experience is thrilling. You’ll feel and hear the difference the first time you listen.”

Adjusting for Open-Air Driving

Cabin acoustics in the MX-5 differ significantly depending on roof position. When the top is down, reproducing lifelike sound with a conventional approach compromises clarity and musical detail — vocals and instruments can be lost when competing with ambient noise. But advanced Bose engineering solves that. Bose tuned the system with two separate equalization (EQ) settings — one for top-down driving and one for top-up. The EQ settings, combined with Bose AudioPilot® 2 noise compensation technology, adjust automatically depending on roof position, wind noise and road noise.

Bose also added new speakers to the driver and passenger seat headrests. Debuting in the 2016 Mazda MX-5, each pair of 2-inch (50mm) Bose® UltraNearfield™ speakers were developed specifically for headrest placement and performance — rather than simply placing conventional speakers in a headrest to add a feature. The new Bose UltraNearfield speakers work with proprietary Bose TrueSpace® digital signal processing technology — and it’s this combination that delivers on the promise of headrest speakers. TrueSpace technology creates a wide sound stage, even though the speakers are just inches away from the listener. The music envelops the driver and passenger, it’s spacious and natural, and remarkably, it doesn’t fade in the breeze.

A pair of 6.5-inch (165mm) speakers are placed in each door for full-range sound, and 1-inch (25mm) neodymium tweeters are located in each A-pillar for enhanced high-frequency clarity. Powerful bass is delivered by a 5.25-inch (130mm) woofer housed in a 6-liter custom enclosure designed to fit under the front passenger footwell without taking up valuable cabin space. Completing the system is a dedicated, 7-channel digital Bose amplifier mounted below the MX-5’s convertible-top storage space.

The 2016 MX-5 Miata continues a long history of collaboration and innovation between Bose and Mazda. The first Bose sound system for Mazda was introduced in 1993, and Bose audio has been offered in Miata models since 1998.