New MTX car subwoofers have been designed using our superior, high-performance Inverted Apex Surround (IAS) design. Found on the 35, 55, and 75 Series subwoofers, this technology delivers more cone surface area, up to 10% more Xmax, and eliminates a distortion problem that has been inherent in traditional surround designs for decades.
Apex vs. Traditional: A Side-by-Side Look
The surround is the material around the outer edge of the cone that connects it to the basket, allowing the cone to move up and down in proportion to the voice coil travel. Surround design plays a major role in sound quality and performance. Here's how the Inverted Apex compares to the traditional half-roll design used by most competitors:
How the Apex Surround Works
Working similarly to the way an accordion compresses, the Inverted Apex Surround is built to fold in at the edges when de-energized, then unfolds to extend up and down as the music starts and amplifier output is applied. Because the surround is much narrower than a traditional half-roll, the same 12-inch subwoofer gets nearly a half inch more cone surface area available to push air and make sound — a significant improvement in both quality and output.
More Xmax
The narrower surround doesn't just free up cone area. Due to its design, the Inverted Apex Surround also allows up to 10% more Xmax — one-way excursion — compared to a traditional half-roll design. More Xmax means the cone can travel further in each direction before distortion sets in, which directly translates to more volume displacement and more output.
More SPL
Volume displacement — the amount of air a subwoofer moves per cycle — determines how loud it can play. The formula is straightforward:
The Inverted Apex Surround increases both sides of that equation: more surface diameter from the narrower surround, and more Xmax from the design's structural advantages. The result is an MTX subwoofer that puts out more volume than competitor models using different technologies at the same diameter.
Eliminates Half-Roll Distortion
The half-roll surround design has an inherent wrinkling effect on contraction that creates distortion in the sound. Due to the structural shape of its arch and the stiffness of material needed to maintain that shape, a half-roll surround collapses somewhat when flexing during play — you can see it in the animation above.
The Apex offers more flex and less of a single-arched structure, eliminating this distortion. The result is cleaner, more accurate bass reproduction — notes stay crisp and true even at high output levels.
See It in Action
Which Series Use the Inverted Apex Surround?
The Inverted Apex Surround is featured across MTX's core car subwoofer lineup:
35 Series Car Subwoofers · 55 Series Car Subwoofers · 75 Series Car Subwoofers
