The MTX Inverted Apex Subwoofer Surround

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MTX Apex Subwoofer Legend
MTX Inverted Apex Surround Animation

MTX Inverted Apex Surround

Traditional Half-Roll Surround Animation

Traditional Half-Roll Surround

Why MTX Subwoofers? Apex for one...

  • More SPL

  • Sounds Better


How Apex Works

The surround is the material around the outer edge of the cone connecting it to the basket, allowing the cone to move up and down from its rest position in proportion to the voice coil travel. As you can imagine, the surround design plays a major role in sound quality and performance as it controls the linear travel of the cone. Linear cone travel and solid support at the end of travel is important for accurate music reproduction, keeping notes crisp and true.

Working similarly to the way an accordion compresses, the Inverted Apex Surround is built to fold in at the edges when de-energized, and unfolding to extend up and down as the music starts and amplifier output is applied.

Traditional Half-Roll Surrounds

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 extends and straightens, moving the cone surface up and down to generate sound waves. This method served us well for decades until the MTX team developed a better method.

The Inverted Apex Surround design uses four folds to tuck in the extension material using less space around the cone diameter compared to the half-roll design. This surround construction provides the same cone extension distance in about half of the width used by a half-roll surround. This means in a twelve inch subwoofer, you get nearly a half inch more diameter cone surface available to push air and make sound... a significant improvement in quality and volume.

Eliminates Half-Roll Distortion

The half-roll surround design has an inherent wrinkling effect on contraction that can create a distortion in the sound. (you can see the wrinkling in the animation) Due to the structural shape of it's arch, and the stiffness of material to maintain the arched shape, the surround collapses somewhat when flexing during play. The Apex offers more flex and less of a single-arched structure that eliminates this distortion, so your music sounds better.

Apex Significant Advantages

  • More 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.

Producing Subwoofer SPL...

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

Our MTX engineering team developed superior surround material construction techniques to overcome the complex linearization process required for great sound. The result is the MTX Inverted Apex Surround with it's extremely accurate subwoofer bass reproduction and outstanding SPL output.


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