MTX 75, S65, 55, and 35 Series subwoofers include Progressive Suspension technology that reduces distortion at high volumes, resulting in cleaner, better-sounding bass. Understanding how it works explains why suspension design is one of the most important factors in subwoofer performance.
What Is a Subwoofer Spider?
The spider is the internal suspension component of a subwoofer. It is constructed from a material such as poly-cotton or Nomex, and its job is to center the voice coil while allowing the cone to move freely in a controlled manner. The spider works alongside the surround — the flexible ring around the outer edge of the cone — to control the full range of the subwoofer's movement.
Traditional vs Progressive Spider Design
- Peaks of equal amplitude across entire suspension
- Uniform stiffness throughout the travel range
- Does not match the progressive characteristics of the surround
- At high excursion, movement can become non-linear
- Introduces distortion at high volumes
- Peaks are larger at the outer edge, shorter near the voice coil
- Stiffness increases progressively through the travel range
- Matches the progressive characteristics of the surround
- Maintains linear movement at high excursion
- Reduces distortion at high volumes
The "progressive" design allows the spider to better control cone movement and match the progressive qualities of the surround. At high volumes when the cone is moving aggressively, this reduces the distortion that a uniform suspension would introduce during those periods of intense movement.
Which MTX Series Has Progressive Suspension?
All four series use Progressive Suspension. The 75 Series takes it further with a progressive poly-cotton foam sandwich suspension — a more advanced construction that requires no break-in period whatsoever. You can play the 75 Series at full volume straight out of the box from the moment it is installed.
Why It Matters
Suspension linearity is one of the biggest factors separating a clean-sounding subwoofer from a distorted one. When a subwoofer's spider cannot adequately control the cone at high excursion, the movement becomes non-linear. Non-linear movement creates harmonic distortion that degrades the bass signal — the kind of difference between bass that hits hard and clean versus bass that just sounds muddy.
Progressive Suspension works alongside the Inverted Apex Surround to give MTX subwoofers the combination of maximum excursion and linear control that makes the difference in both SPL and sound quality.
