Amphion FlexBase25 User manual

Handmade
in Finland
create
FlexBase25 System
Reference Manual

Table of contents
Introduction
Front panel controls
Back panel connections
Block diagram
Connectivity diagram
Technical specications
Settings - recall sheet
3
4
6
7
8
9
10
FlexBase25 delivery contains:
i
1 pc Amphion FlexBase25 2U Amplifier & Crossover
1 pc Amphion FlexBase25 Tower
1 pc Neutrik Speakon/Speakon (NL4FX) 4-pole
speaker cable for connecting. Length 3.5 meters
1 pc FlexBase25 Reference manual

3
Introduction
Welcome
Thank you for choosing FlexBase25. The music-making environment continues to change, and the
demands for monitoring evolve accordingly. As modern music becomes more bass-intensive, the
need to hear clearly into the lowest octaves becomes crucial. Ever tightening deadlines, last minute
changes, and an increasing need to be able to have control over multiple segments of the project
mean that monitoring must adapt to different demands.
FlexBase25 looks simple, but it houses a lot of new thinking. It is easy to set-up and intuitive to use.
It can be easily adapted to whatever task the modern sound engineer may encounter. We hope that it
help you finish your project more quickly, while contributing positively to the creative process.
Anssi Hyvönen
Founder, CEO
Amphion Loudspeakers Ltd.
The System
The FlexBase25 is an unconventional yet easy-to-place and simple-to-set-up approach to subwoofer
design. For correct, well-translating decisions an engineer needs to have access to the stereo
information throughout the whole frequency band. Mono subwoofers stem from a movie format and
tend not to be sufficiently resolving for music use.
FlexBase is a single box, stereo subwoofer, which is placed in the centre line between the main
speakers. Wide adjustment possibilities over crossover frequency (35-260 Hz), subwoofer level,
as well as the mono-stereo spread allow FlexBase to address the needs of a rapidly changing
landscape of modern music-making. With a turn of a few dials, the system can be adapted to
what best works for the project an engineer is working on.
FlexBase can be fat, fun, and vibey when writing and producing. It will be precise, correct, and
analytical when putting the finishing touches on a song or a film score. The system will allow you to
continue to use your monitors for a narrower midrange view, as FlexBase can be bypassed. FlexBase
works with all Amphion products. Pair it with One12, One15, Two15 or One18 for a smaller room full
range system or place it with behind the console while keeping your One18, Two15 or Two18 on the
meter bridge.

2 1
483 mm / 19”
2U
89 mm
3½”
3 4 5
4
Front panel controls

1
2
3
4
5
5
.
Power button
Power button turns on the power of the unit. Please note that hard bypass is enabled also when power is off,
and that the unit always switches to active mode after power is switched on.
Active button
Active button switches the unit between hard bypass and active mode. The FlexBase is active when the
light is on.
Level
Level dial controls the level of the low frequency extension provided by the FlexBase. The right setting depends
on your speaker model sensitivity, your room low frequency absorption, and your personal preference and
application. During song-writing, fun and vibey settings might be preferred over more “correct” ones. FlexBase
allows easy adjustment as work progresses. While it is common practice to write or start the mix with a slightly
elevated low frequency for mastering use as well as for optimal mix translation, a more neutral setting tends to
be more beneficial.
Tip for finding a balanced setting: Use the Active Button to switch between active and bypass mode to find a
(neutral) setting where the low frequency response is extended but not exaggerated by the FlexBase. Tweak
your setting to taste as needed.
Crossover Frequency
Crossover Frequency control allows you to choose how much of the low frequency range you want the FlexBase
to handle. The higher the frequency, the less heavy lifting is required from your main pair of speakers. This will
help to keep the midrange clean, especially at high SPL levels. A lower crossover frequency setting allows a
subtle add-on of the missing lowest octave(s) to your main speaker without changing the sound character you
are familiar with. As a general rule, the smaller the main speaker, the higher the crossover frequency.
Choosing the right crossover frequency can greatly help in achieving the smoothest low frequency response
in your room. As speaker placement greatly affects the low end response, adjusting the placement of the
problematic frequency range between the monitors or the FlexBase can be surprisingly efficient when battling
room modes (a certain frequency which is either exaggerated or almost lost, especially in smaller rooms).
60-300 Hz is typically an area where rooms present their biggest problems. It is therefore worth experimenting if
the room response can be improved with the crossover adjustments.
In order to achieve the purest possible signal path, the variable crossover is implemented by switching between
16 discrete filter configurations. Depending on your input signal and monitor setup, you might hear this switching
between steps as a faint “click” for each step. This is normal behaviour and similar to stepped high-end level
attenuators.
Note: The higher the crossover frequency, the more important it becomes to run the FlexBase in stereo mode
(please see Adjusting the stereo spread).
Adjusting the stereo spread
This control allows you to gradually move from a more traditional mono response to a full stereo image. The
best setting depends on several aspects such as how wide your main pair stereo image is as well as on your
personal preference.
Please note that although it is true that localizing the sound direction becomes increasingly difficult as frequency
decreases, polarity and phase differences between left and right channels are certainly detected all the way
down to the human hearing limits. This is one reason why traditional subwoofers can deceive you and ruin mix
translation to other systems.
Front panel controls

6 7 8 109 11
6
7
8
9
10
11
6
.
Input +4dB (L and R)
These are the balanced inputs for your stereo signal. If you are using an unbalanced source, it is
recommended to connect XLR pin 3 to pin 1.
Main out (L and R)
These are the outputs for your main power amp and speakers. If you are using an unbalanced destination,
it is recommended to leave XLR pin 3 unconnected.
LFE input
This is a direct input for a separate LFE signal (such as the .1 in a 5.1 monitoring setup). Sensitivity is +10dB
compared to the main inputs, and there is no built-in low pass filtering applied. In other words, the crossover
frequency does not affect this signal. The LFE level is also not affected by the front panel level setting.
LFE link out
This connector is provided for chaining the LFE signal across several BaseAmp units (typically in a multichannel
setup).
Base out
Neutrik Speakon (NL4FX) 4-pole speaker output for the FlexBase25 tower.
IEC power connector
Power input, auto switching in the 100-240V range, internally fused.
Back panel connections

HPF
LPF
HPF
LPF
AMP
AMP
FLEXBASE
SPEAKER
CROSSOVER
FREQUENCY
STEREO
WIDTH
LOW FREQ
LEVEL
LEFT
INPUT
RIGHT
INPUT
RIGHT
OUTPUT
LEFT
OUTPUT
LFE
INPUT
LFE
LINK OUT
7
Block diagram

8
Connectivity diagram
Set-up Tip:
For Use With Consoles
While FlexBase25 performs well
positioned directly on the floor,
when used with large format
consoles - where monitors are
placed on the meter bridge
- it is advisable to raise the
FlexBase to be more in line with
the monitors by lifting the unit
from the floor using solid, non-
resonating material (eg. bricks or
slabs). A good starting-point is to
raise the FlexBase so as the top
of the woofers can be seen over
the console edge.
Rear view
Right Signal
Left Signal
LFE Signal
Right Speaker Left Speaker
Main Amp
FlexAmp500
FlexBase25
!
!

9
Technical specications
FlexBase25
FlexAmp500
Operating principle
Drivers
Crossover
Max SPL
Frequency Response
Weight
One way closed box, stereo
2 x 25 cm / 10” aluminum driver
Active 4th-order @ 35-260 Hz
117dB
20 - 260 Hz +/-3dB (low pass)
35 Hz - 200 kHz +/-3dB (high pass)
50 kg / 110 lb
Output power
Distortion
Signal to noise ratio
Efciency
Weight
600W RMS into 4 Ω@ 1% THD
@1W: 0,003% (100 Hz)
@100W: 0,006% (100 Hz)
93dB @ 1W
85% @ full power (230V operation)
5 kg / 11 lb

10
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
Settings - recall sheet

11
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
125 170
60 240
80 215
105 195
35 Hz 260 Hz
150
Mono Stereo-10dB +10dB
SETTING NAME:
DATE:
Settings - recall sheet
.

Amphion Loudspeakers Ltd.
Factory & Headquarters
Vitostie 1864
70800 Kuopio
Finland
Tel. [phone]
[email protected]
amphion.fi
Reference Manual
Version: 1.3 / 20.02.2019