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Srajan Ebaen
Financial Interests: click here
Source: Ancient Audio Lektor Prime, 1TB iMac (WAV, AIFF) via FireWire 800 into Weiss DAC2
Preamp/Integrated: Esoteric C-03 (transistor), ModWright DM 36.5 (valves), Peachtree Audio iDecco [on review]
Amplifier: FirstWatt F5
Speakers: Amphion Helium 510 [on review], Anthony Gallo Acoustics Strada + TR3 [on review], Swans Speaker Systems M3 [on review], Era 5 SAT
Cables: Complete loom of ASI Liveline
Stands: 2 x ASI HeartSong 3-tier, 2 x ASI HeartSong amp stand
Powerline conditioning: 1 x Walker Audio Velocitor S, 1 x Furutech RTP-6
Sundry accessories: Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; extensive use of Acoustic System Resonators, noise filters and phase inverters, Advanced Acoustics Orbis Wall & Corner units
Room size: The sound platform is 3 x 4.5m with a 2-story slanted ceiling above; four steps below continue into an 8m long combined open kitchen, dining room and office, an area which widens to 5.2m with a 2.8m ceiling; the sound platform space is open to a 2nd story landing and, via spiral stair case, to a 3rd-floor studio; concrete floor, concrete and brick walls from a converted barn with no parallel walls nor perfect right angles; short-wall setup with speaker backs facing the 8-meter expanse and 2nd-story landing.
Review Component Retail: €1.190

Subwoofers are the adolescent bad boys of hifi. To most serious music lovers, they suggest boom trucks, SPL competitions and in-yer-pimple-face excess.

For THX-approved home theater nonsense, subs are de rigueur of course. Unnatural infrasonics of rocket launches and various explosions played back at 'realistic' volumes—ha!—are quite beyond what music speakers are and should be designed for.

In short, subs suffer a bum rap for music. Yet threesomes of stand-mount monitors + sub are often the best solution to bridge decor acceptance and actual performance.

Rather than max extension and brutal output, it's speed, low distortion and above all a superior low-pass filter adaptable in fine increments that become the top to-do items now.
Amphion's Anssi Hyvönen: "As you have noticed by now, our view is less is more. We really believe in that. And it goes far deeper than aesthetics. Because one always must compromise somewhere—others than US sales and marketing guys of course—we make sure our subs play mere supporting roles so the main focus remains on the speakers. And exactly like with those, the three most important rules for us are integration, integration, integration.

"Making a good reasonably priced sub is a tightrope walk. The home theater market wants boom boom. To do that very loudly, one needs to make certain choices. Those insure that tonality and speed are drastically compromised. Now two-channel audiophiles will pass on any sub because they categorically and rightly "don't do—those types of—subwoofers for music". It's actually a shame. A good working concept gets blamed for bad execution. Small bookshelf monitors and a sub done right offer a sonically great and flexible solution for both two-channel music and movies.
"Naturally one won't get ultimate rattle and bang if aiming for lowest bass extension. Often upper bass mush also is a legacy of that general package.

"One needs to be a silly small manufacturer like Amphion to tackle the problem from the perspective of 'we are far too insignificant to worry about market studies claims; let's do something that works for our kind of customer who loves both music and movies (and when the time for compromise comes,
will always steal from the movies to leave the music untouched)'.

"I think manufacturers too often cater to the market rather than sticking to their guns by stating that they won't budge below where the compromise curve goes exponential after a given size or price point. A typical point is that the wife wants a smaller sub. Instead of designing a well-performing 10-inch  subwoofer, companies go after a compromised smaller 8-incher. Size shrinks and so does performance quality."
Astonishingly attractive in an ultra-clean Scandinavian way particularly in the clever white skins, Amphion's Impact 400 is a sealed down-firing affair with 500-watt class D amp and high-excursion Peerless Tymphany paper-cone driver. Because you don't want high amplitude low bass energy interfering with inductors and capacitors—and nowhere in the room are things louder than inside the speakers particularly when those are sealed—Amphion's amplifier module is completely encased. The cubic 350 x 350 x 387mm enclosure is also braced and filled with damping material.
Amphion's insistence on integration relies on their CSC or cumulative stage coupling filter whose steepness increases with rising frequencies.

"This ensures that phase changes are as linear as possible and group delay is minimized. At the rejection band above 150Hz, we operate a 5th-order 30dB/octave slope which effectively filters out the higher frequencies. The low-pass filter may be bypassed with the direct switch when connecting to the LFE channel of a home theater receiver or processor."

Avoiding leakage from the sub into the upper bass and lower midrange bands is mandatory to avoiding the usual mud which lesser subwoofers so often inject into the main speaker range.

Back panel features are:

• 1 - 115/230V switch
• 2 - power mains
• 3 - fuse box with T5AL/250V or T9AL/250V fuse at 230/115V respectively
• 4 - 3-prong IEC power inlet
• 5 - High-level 5-way outputs
• 6 - High-level 5-way inputs
• 7 - Attenuator
• 8 - Twin color LED for signal on/off
• 9 - 3mV signal-sensing auto power with 10 - 15 min. standby cycle
• 10 - 30Hz to 100Hz low-pass filter control
• 11 - crossover bypass switch
• 12 - 0°/180° phase switch
• 13 - Line level RCA inputs (right for mono)
• 14 - Line level RCA outputs

English owner's manual here.
Cone footers and threaded receptacles are standard but sensitive users will already know that floor coupling of speakers sends significant vibrations into their equipment racks. Decoupling solutions are ultimately preferable particularly with subwoofers.

Concluding the overview, this Finnish bass player acknowledges the need for a certain cubic volume to do the jo properly (i.e. it's clearly no micro sub though it's far from huge); insists on sealed loading (who'd want a ringy ported alignment?); uses 1-inch panels for increased box stiffness; has provisions for filter loop mode and augmentation mode both at line level (preamp output) and speaker level; and a broad range of continuous low-pass filter adjustments.

What the Impact 400 shuns are parametric EQs, bass boost provisions and ultimate SPL specs. Its design brief very specifically was music first. For more grunt, Amphion offers the bigger 12-inch Impact 550 (only in black however).

This review is a follow-up type companion piece to my previous Amphion Helium 510 article. As a very good €900/pr 5-inch monitor with surprising treble refinement and upper midband integration, its limitations were obviously in bass extension and weight particularly since Amphion wisely refrained from massaging that aspect to instead optimize linearity and transparency. The Helium 510 was a perfect candidate for subwoofer assist. Other suitable monitors in residence included the Swans Speaker Systems M3 and era Speakers' 5 SAT.