Subwoofer Surrounds: The Inverted Apex Advantage

MTX Inverted Apex Surround Animation

MTX Inverted Apex Surround

Traditional Half-Roll Surround Animation

Traditional Half Roll Surround

All MTX car subwoofers are now designed using a high performance, Inverted Apex Surround design. The surround is the material around the cone that connects to the basket allowing the cone to move up and down from its rest position in proportion to the voice coil travel.

Working similarly to the way an accordion compresses, the Inverted Apex Surround is built to fold in at the edges when de-energized, but still extending up or down as the music plays.

Most subwoofers use the traditional half-roll surround where the cone surface is attached to the basket with material wrapped in a single half circle. The circumference of the half circle provides the length available to extend the cone up or down as the circle straightens, moving the cone surface up and down to generate sound waves.

The Inverted Apex Surround design uses four folds using less space around the cone compared to the half-roll design. This surround construction provides the same extension distance in half of the width used by a half-roll surround.

The Inverted Apex Surround design provides two significant advantages over traditional, half-roll surround designs:

  • More Volume (SPL)
    • The volume of sound (Sound Pressure Level) is proportional to the volume of air moved per subwoofer cycle and the volume of air moved is a result of the one-way extension measurement (typically Xmax) times the cone surface area (proportional to usable diameter).
    • The Inverted Apex Surround increases the cone surface area by using about half the diameter of surround width.
    • SPL is increased per a given subwoofer diameter.
    • The Inverted Apex Surround moves symmetrically through both positive and negative cycles.

Subwoofer SPL Calculation

  • Music Sounds Better
    • Half roll surrounds have an inherent “snap-through” distortion that occurs in the surround due to the physics of its action. (See the wrinkles in the animation)
    • Better construction methods and materials can limit this distortion but the Inverted Apex Surround eliminates this problem, resulting in better sound quality.
    • non symmetric  motion control

The MTX engineering team works on constant development of material construction techniques to overcome this complex linearization process, so you get extremely accurate music reproduction while still maximizing SPL.

Leave your comment
10/9/2015 4:17 PM
Huge difference in sound quality with spl that will scare dinosaurs, aliens, etc away with busta rhymes music
2/3/2016 3:09 PM
For whoever finds this page:

8 5512 subwoofers with the apex inverted surrounds in a 6th order bandpass = insane low frequency extension and surprising musical ability.  Keep in mind the enclosure (6th order bandpass) was built specifically for the 5512 subwoofer.