Exodus Audio EX-PR15, EX-PR18 Owner's Manual

Exodus Audio Owner’s Guide 1

EX-PR15

Exodus Audio Owner’s Guide 1

Copyright  2008 Exodus Audio. All Rights Reserved.

Exodus Audio Owner’s Guide 2

Introduction

The EX-PR15 is a high performance passive radiator designed for use with the Exodus Audio
Subwoofers. The PR series passive radiators offer lots of clean stroke, and a very flexible
system for adding mass. The PR mass-kit consists of multiple 96g steel discs that can easily
be added or removed from the passive radiator to optimize cabinet tuning frequencies.

Passive Radiator systems add output to a system, much like a ported box design. The
passive radiators resonate at a frequency determined by the size of the enclosure, the area
of the cone and the moving mass of the passive. As a result, a carefully designed system
can extend the bandwidth of a subwoofer, without the negative aspects of a port.

In what ways are passive radiators superior to ports? For one, they don’t require the
enclosure volume of a port. Ports occupy volume inside the enclosure and large ones occupy
a LOT of space. Ports for high output subwoofers also need to be LARGE in diameter.
Large ports also have to be LONG in order to tune the subwoofer to a useful frequency.
The more capable the active driver, the larger the port needs to be. As a result, the
Exodus subwoofers require MASSIVE ports to achieve noise-free operation. We find
passive radiators to get around these problems. They require minimal enclosure volume,
they don’t make noise out of bandwidth (port chuffing and resonant frequencies based upon
port length) and they are easier to tune deep, without the tradeoffs a designer is forced to
accept with large ports.

Do Passive Radiators have any negative attributes? Sure, there is no free lunch. For one,
passive radiators are typically more expensive than a port (although high quality flared ports
are not cheap either). Passive Radiators tend to have more losses than a well-designed port.
The losses are fairly minimal though and the difference is usually not significant in the final
design. Passive Radiators require different enclosure building requirements. They
physically take up more space on the outside surface of the enclosure.

Much like a port, passive radiators come at a cost. Under the tuning frequency of the
passive the active driver unloads, requiring careful attention be paid to electronic protection
of the main driver. This is easily accomplished with the proper choice of amplifier and
signal processing. We strongly recommend that you follow our application notes carefully
when building a resonant system.

Exodus Audio Owner’s Guide 2

Copyright  2008 Exodus Audio. All Rights Reserved.

Exodus Audio Owner’s Guide 3

Parameters

Fp: Resonance frequency (in free-air with no
added mass)
Qmp: Mechanical compliance loss 6.0
Mmp: Moving mass 200g
Cms: Suspension Compliance 0.28 mm/N
Vap: Stiffness of driver scaled by cone size 245L
Sd: Area of the cone 791 cm^2
Suspension Travel 32-35mm one way. Somewhere around 60-

20.0 Hz

70mm peak-peak, depending on how far you
stretch the suspension. The system will not
bottom mechanically until 40mm (one way).

Mass Kit

The Mass Kit consists of a 120mm bolt, washers, lock washers and extra nuts to thread down
the bolt, holding the mass disc in place. Each disc is approximately 96g. The bolt assembly
is approximately 48g so you can add mass to the system by adding the appropriate number of
steel disc. Remember to add your Mmp starting mass (200g) to the total.

Exodus Audio Owner’s Guide 3

Copyright  2008 Exodus Audio. All Rights Reserved.