User Manual
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No.25 employs an advanced lter circuit which provides exceponal performance when coupled to the rest
of the signal chain of the Sub-Bass System. A second-order variable low-pass lter approximang a Bessel
funcon was chosen for its linear phase response, which equates to at group delay. This means that, unlike
other lter funcons, the amount of delay the signal is subjected to during processing is constant through
the enre pass-band, which improves the frequency response and allows for beer integraon of the sub
with the main speakers. An addional xed second-order Bessel lter follows the variable lter, removing
unwanted midrange signals that, if le unltered, cause the midrange of the main speakers to become
muddy or congested. All ltering is performed in the analog domain using high-quality components with
ght tolerances to ensure the highest possible performance and consistency.
The amplier is inherently stable and will retain its characteriscs over very long periods of me – important
in a unit designed for an exceponally long working life. These ampliers are designed to withstand reasonable
abuse and overloads. If in doubt, please contact your dealer.
We believe that the importance of the electronics, cabinet and drivers being designed to work in harmony is
paramount. This belief allows No.25 to achieve the highest possible level of delity.
Overload Protecon
All REL Sub-Bass Systems are designed as true sub bass speakers. They are designed to reproduce those
exceponally deep notes that are felt as well as heard. This it will aempt to do at whatever volume level
you set. If set too high no damage should result because the built-in electronics will limit the cone movement.
This electronic control is called Set-Safe™. It constantly and instantaneously monitors the output from the
power amplier and is totally transparent in operaon unl required. This means it has absolutely no eect
on the sound quality of your REL unl an overload is detected.
Ordinarily an overload would cause the power amplier to go into clipping with resultant loss of control
over the drive unit. This can cause drive unit damage, and always sounds nasty. Set-Safe™ detects the point
of incipient clipping and gently so-clips the waveform of the signal to ensure actual clipping does not occur.
This is a necessarily simplied descripon of what actually happens, but in eect, Set-Safe™ controls the
amplier and ensures there is minimum risk of amplier and driver damage caused by over-driving.
Technical