Paul Millers gets to play with SAM
SAM is a pre-programmed DSP model of a loudspeaker's low frequency behavior that matches the air pressure received by the recording microphone with the output of the loudspeaker' says Pierre' Emmanuel Calmel, Devialet's co'founder. Eventually any choice of speaker may be downloaded to your Devialet amp (currently only the B&W 802D and a Vivid have been mapped).
But before we explore what SAM is, it's important to state what it isn’t. SAM is not invasive - the speaker, its crossover and drivers do not require modification. Neither is SAM a feedback-controlled correction, a room compensation regime or a form of bass boost. lnstead, correction is applied dynamically, sample-by-sample in the time domain according to all known performance attributes of the loudspeaker cabinet, crossover and drivers. The real-time model{s) currently operate between 10-150Hz, depending on the capabilities of the loudspeaker.
The position and acceleration of all the drivers is precisely modeled and controlled according to the cabinet dimensions, volume, compliance of the air,
mass of air in the vent and reflex losses. All linear and non-linear Theile & Small driver parameters are accommodated including resonance frequency, Q and force factor, moving mass, suspension compliance, diaphragm area, etc. The list goes on.
Devialet has even invested in a (laser) Scanning Vibrometer from Klippel to develop 3D maps of the speaker's low-frequency drivers. The support of the loudspeaker's manufacturer is not necessarily required, it seems...
Of course, by fully controlling the amplitude and phase response of the speaker's output, SAM promises to maximise the bass extension of any speaker without ever moving its drivers outside their safe excursion range. Similarly, the non-linear inductance of voice coils, eddy currents in the motor system, power dissipation and heating effect of the voice coils can also be precisely mapped, Thermal compression and other distortions, typically unavoidable or uncontrollable with conventional power amp/passive speaker combinations can now be, well, avoided
But enough of the theory. What does SAM sound like? ln short, it's jaw-dropping. A rerun of Harald Kloser's theme tune from Thee Day After Tomorrow (44.1kHz/16-bit FI-AC file) made me jump off the sofa. Without SAM, the dual monoDevialet 500 and B&W 802D combination sounded fabulous - the breadth and depth of this atmospheric score filling the room with a peerless clarity. Or so I thought. Then I switched in the SAM algorithm for B&W's 802Ds.
From the first note, the first touch of bow on strings it was immediately obvious - not only to myself but also the other three listeners in the room - that the midrange and treble octaves possessed a greater clarity, transparency and sheer poise. But SAM only works up to 150Hz...
Evidently, by precisely anchoring the two bass units there's less harmonic distortion and other colour working up into the higher ranges. But I was still in my seat. Then the first murmur of timpani was revealed and like a freight train gliding on ice it slipped through the orchestra, its weight palpable, its momentum and gravitas undeniable.
For one distracted moment l thought I'd left my 1kW subwoofer connected and the roof was about to be raised. I jumped up only for the pressure wave to pass. Despite my rattled ribs, the 802Ds had not exploded, for this was the cleanest, deepest bass I'd ever heard extracted from a cabinet of this size. SAM had done its stuff, obliging these two 8in bass units to move precisely and safely to accurately reproduce the sound of this deepest and most resonant of instruments.
So is SAM the future of precision amp/ speaker matching? For Devialet and its customers, certainly. But don't expect the concept to migrate further afield anytime soon
