The amplifier used in all Osborn Subwoofer is custom designed for Osborn loudspeakers by Redgum (The amp with the key). Redgum manufacture some of the best amplifiers available at any cost and is proudly designed and manufactured in Australia. Only premium quality components are used. Extremely high quality Audiophile grade mosfets are used instead of the cheap Output IC's used in many other Subwoofer Amplifiers. A quality Power Supply is used, utalising a High Speed Torroidal Transformer. Many lesser subwoofer amplifiers rectify the mains voltage directly, resulting in a cheaper, but inferior performance. Auto switching was tried but rejected as these circuits are always troublesome, switching on and off at inopportune times. The amplifier is designed to be left on at all time so it is always at optimum temperature. Power consumption at idle is minimal.
It
is this no-compromise approach which results in the sound quality
attained by all these units. The amplifier was originally designed
to be made in either a 180, 300 or 500 watt version. However the
performance is so outstanding with the 180 watt unit, that the
300 and 500 watt version is unnecessary. The problem with having
so much unnecessary power is the extreme heat generated. 500 Watts
equates to 180 degrees Celsius, which is a major problem in a
wooden cabinet. This is why competing designs use switch mode
power supplies to avoid this heat generation, thus compromising
performance for impressive power claims. The Monumental and Ultimate
use a larger power supply and more output devices and output 200
watts at 8 ohms and have a better dynamic ability. The Twinultimate
uses a 300 watt version of this amplifier. Remember competing
manufacturers usually rate their amplifiers into a 4 ohm load.
This is an easy and economical way of being able to claim impressive
power outputs.
Most subwoofers are designed to output large amounts of woofy
bass in the 40 to 80 Hz region. They may be loud, but drone excessively
and lack impact and the ability to reproduce frequencies which
can be felt rather than heard. Large drivers are stuffed into
enclosures which are hopelessly too small, simply because they
look impressive to a prospective, but uninformed customer. Because
there is no low frequency generated at all, the designer is forced
to feed in excessive equalization to try and force the driver
to generate frequencies well below its abilities. Any audiophile
is well aware what an amplifier sounds like with the loudness
on and the bass turned right up. There is bass, but not a realistic
and powerful reproduction of the original performance. More like
a rumbling mess.
Osborn subwoofers employ no equalization. Bass extension
is achieved by careful design and outstanding bass drivers.
Osborn subwoofers are not designed to blow out windows and
loosen dental fillings, but for realism, depth, sonic integrity
and sheer satisfaction, they are unsurpassed.
INPUTS
All
subwoofers can be connected to a low level input or a high level
input. The low level input are for direct connection to a pre
amplifier or Home Theater Amplifier Subwoofer output. If the left
and right inputs are connected the amplifier will mix and reproduce
the signals from both channels.
The
high level inputs are provided for use where there are no low
level outputs, such as in integrated amplifier. A second pair
of speaker cables will need to be connected to the output terminals
of the amplifier and connected to the relevant binding posts of
the amplifier. This enables the subwoofer to sense the bass information
of the music and reproduce it at whatever level is desired. Naturally
the performance will be generally better using the low level inputs
if possible, as sensing a high level input does introduce some
unavoidable distortions.
Power output:
| Subwoofer: | Power Output: |
| T12, T15 | 175W Rms continuous - 351W Rms short term transient (100ms) |
| Ultimate,Monumental, FC12, FC15 | Hi Power transformer - 195Wrms continuous - 351Wrms short term. (Larger power supply) |
| Frequency response | (relative to 20hz/0db) - minus 3db points are 1hz and adjustable from 20hz to 200hz |
| Damping factor | >200 (calculates to 205.128!) |
| Input sensitivity | 220mV for 175Wrms |
| Signal to noise | (output stage) >110db |
| Signal to noise | (overall) >85db |
| Slew rate | (overall) 35v/uS |
Features:
| Power supply & all internal wiring Linear Xtal 130amp |
| Torroidal power transformer |
| IEC standard power input socket |
| High power, Audio Grade, thermally stable MOSFET output stage |
| Mosfet I/C in filter stages. |
| All high current paths are designed for minimum length |
| Every power supply lines is bypassed with plastic caps. |
| All connections are silver soldered for better sound, longer life and reliability. |
| All Australian made - all Australian Design |
DESIGN PHILOSOPHY
Osborn Loudspeakers are designed
for the ultimate reproduction of the original performance. Therefore
we have approached the design of our subwoofers a little differently
to other Manufacturers.
Many
subwoofers provide low level outputs. We consider this unnecessary,
especially due to the quality and expense of the connectors used
in this amplifier. We cannot see the logic of extremely long and
expensive interconnect cables running from a pre amplifier to
the subwoofer and then back to the main power amplifier. This
would also result in the main amplifier signal needlessly passing
through part of the subwoofer amplifiers circuitry. If necessary
a splitter can be used closer to the pre amplifier.
Many
subwoofers also provide high level outputs where the signal is
passed through an active crossover network, removing the very
low frequencies delivered to the main speakers. This also goes
against the philosophies held by Osborn. Firstly passing the main
speaker signal through this crossover will cause unavoidable degradation
to the signal. It is impossible to pass a signal through any electronic
components without affecting it in some way. Secondly the removal
of low frequency information delivered to the main speakers may
allow them to be played louder, but if the speakers are quality
units, such as an Osborn model, then they are better suited to
reproducing the removed frequencies than any subwoofer.
