Variable crossover frequency allows changing the flavour of the system to match the specifics of the various production tasks.


Mono/stereo spread adjustment to ensure precise system-integration, even when higher crossover points are used.


Fast and simple-to-set-up, easily adapting to a large variety of projects and acoustic environments.

Operating principle
One way closed box, stereo

2 x 25 cm / 10” aluminium

Active 4th-order @ 35-260 Hz


Frequency response
20 Hz – 260 Hz +/-3dB (low pass)
35 Hz – 200 kHz +/-3dB (high pass)

3.5 m long, terminated with 4-pole Neutrik Speakon connectors

50 kg / 110 lb

Handmade in Finland

Output power
1 % THD+N, 20 Hz – 20 kHz 700 W (4 Ω) per channel

THD+ noise
@ 10W: 0,0025% (100 Hz)
@ 100W: 0,0015% (100 Hz)

Dynamic range
127 dB  (A) weighted

230 V / 50 Hz – 700 W
120 V / 60 Hz – 670 W
100 V / 50 Hz – 460 W

Universal mains including Power Factor Correction (100 – 240 V, 50 – 60 Hz)

Stand-by mode
ErP (1275/2008/EC),  Energy Star® v3.0 compliant

6 kg / 13 lb

Made in Finland

*) Estimated retail price. Prices may vary due to local taxes, shipping and other additional costs.

In detail

Total control for maximum impact

Amphion’s FlexBase25 is a modern approach to subwoofer design. FlexBase25 is room friendly and equally suited for studio acoustics as well as less-treated home studio environments. It is easy to setup and intuitive to adjust. FlexBase25 is a single box, stereo base extension system, which is placed on the center line between the main speakers.

Wide adjustment possibilities regarding crossover frequency (35-260 Hz), subwoofer level, as well as the mono-stereo spread, allow FlexBase25 to address the needs of a rapidly changing landscape of modern music-making. With a turn of a few dials, the system adapts to any task you happen to be working on. It can be fat, fun, and vibey when writing and producing. It will be precise, correct, and analytical when putting the finishing touches on a track or a film score.

FlexBase25 does not work like a conventional subwoofer. It does not only add, it also transforms. FlexBase25 turns your 2-way monitor into a 3-way full range system, which increases the monitor’s headroom radically. Pair it with One12 or One15 for an ultra-fast, easy to adjust small room full-range system. Place it behind your console and let it blend seamlessly with your One18, Two15 or Two18 monitor, which are located on a meter bridge. When you want to dial in on the midrange the by-pass function allows you to use your monitors for a narrower midrange view.

While FlexBase25 is naturally optimized for Amphion products, nothing prevents using it with different studio monitors as well.


Media reviews

“It doesn’t sound like a subwoofer”

“My only advise to existing Amphion users would be to only try this system out if you have the means to pay for it, as you’re not going to want to give it back!”

Sound on Sound logo

“Wow, that thing kicks!”

“An odd bit of praise is that most of the time I forget that the FlexBase25 is there. I never feel like my bass is overcooked; it does its job and stays out of the way, adding just the low end I need to nail my mixes.”

Studio monitors