Loudspeakers

Occupying nearly the full height of the cabinet interior is the huge linear PSU, DSP section and Class AB amplifiers (with heatsinks facing outward) that power its four 165mm bass units, 165mm midrange and 27mm tweeter. Further lowering the cabinet’s centre of gravity is a 700VA toroidal transformer feeding all the linear PSUs across the two main PCBs. There is a small switchmode PSU under a black cover that supports standby mode, but this is disabled the moment the loudspeaker is fully powered up.

Also under this shell is a SHARC processor – the brains of the system – handling all the audio-related processing, including file format conversion and synchronous upsample/downsampling in tandem with Naim’s proprietary minimum phase digital filter [HFN Nov ’23]. This has a high ~60th-order roll-off and defines the Diva Utopia’s practical 22kHz audio bandwidth [see boxout] within which the 150Hz and 2.5kHz crossovers are managed with low-order filters. Similarly, Naim/Focal has resisted the temptation to ‘go crazy’ and iron-out every minute peak and dip in the speaker’s forward response using the powerful DSP at its disposal. In practice the phase/time-related distortions that this would inevitably introduce would outweigh any subjective advantage of achieving a slightly flatter response.

Meanwhile, Naim’s choice of StreamUnlimited input streaming card hands over to Naim’s UWB (Ultra Wide Bandwidth) network for wireless sync/audio/volume communication between the Master and Slave loudspeakers. (Wireless UWB supports 96kHz/24-bit with a higher 192kHz/24-bit carried by the wired Ethernet connection.) Above lies an Atmel processor responsible for all the ‘non-audio’ control functions.

Back under the black bonnet are two Burr-Brown PCM1791A DACs (three of four channels are used here, of course) with a digitally-governed analogue volume control and a total +4dB of preamp gain. Digital gain is only used to optimise the Diva’s dynamic range with low peak-level signals. Four screened interconnects take the line audio to the top PCB and its four power amps. The two pairs of woofers are split between two 125W power amps while the midrange and tweeter are fed by a pair of 75W amps – all Class AB – their closest relative being Naim’s evergreen Supernait. PM

Above: Behind the rear plate of the ‘Master’ speaker lies the custom DSP and four Class AB amplifiers at the heart of the Diva Utopia. The ‘Slave’ has the inbuilt amps only (no further DSP)