Roy George on SIGAO DRIVE

Posted on 2nd May 2024 in Category: News

For us at Kudos Audio, the SIGAO DRIVE external crossover has been a dream product for some time. 

Yet, before we even entered product development for SIGAO DRIVE, we knew that it would take some serious out-the-box thinking. An unpowered external crossover that was technologically capable of sitting in front of the power amplifiers in the signal chain – this would represent something altogether new to mainstream HiFi. As such, we’d need to go right back to the engineering drawing board, and take no design decision for granted. 

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To help us do that, we partnered with one of the few individuals who can legitimately wear the title of ‘HiFi Legend’. Naim Audio’s erstwhile Technical Director, Roy George, who collaborated with the Kudos Audio team to help bring our unique product goals in-house designs to life. 

When it comes to re-writing the rule book of high end audio, few carry as much successful experience as Roy. And so Roy represented a perfect collaborator for this new project. To mark the product’s coming launch, we asked Roy to give us some insight into working with the Kudos team to create SIGAO DRIVE. In the process, we explored why it represents such a significant shift in thinking from conventional passive or active configuration.

He kindly obliged. Roy’s answers made for a fascinating read, and so we were pleased to be able to share them with you in this piece. We started by asking Roy a straightforward but crucial question….

Q: Why did Kudos choose to make SIGAO DRIVE unpowered? 

HI RES SINGLE 3 scaled e1714650787795“Almost universally, loudspeaker drive units can accurately reproduce only a proportion of the full ten octaves of audible bandwidth. Hence almost all loudspeaker systems incorporate two or more drive units. The loudspeaker crossover splits the audio signal into frequency bands suitable for each drive unit’s capabilities.

The crossover is connected between the power amplifier and the drive units, typically inside the loudspeaker enclosure, but occasionally mounted outside. The power amplifier cannot have complete control of the drive units because of the crossover components between them. What’s more, these components are likely to introduce some level of distortions and microphonic degradation.

To overcome this limitation, and in the pursuit of the highest resolution reproduction, several power amplifiers can be used – with each loudspeaker drive unit directly driven by a power amplifier channel. The audio signal is then divided before the power amplifiers at signal level. This is accomplished using “active” filters using high quality signal level components and multiple transistor or op-amp circuits. 

However well designed, these circuits, and their required high-quality DC power supplies, add noise and distortions to the signal and so deviations from neutrality. These are especially obvious in an active system, due to its very high resolution.

For SIGAO DRIVE, Kudos Audio has adopted a third way. It is an unpowered crossover but it is connected between the preamp and the power amplifiers, again allowing the power amplifiers to grip and control the drive units by direct connection. Being unpowered, the Kudos crossover has no active electronics or power supply to add their inherent character to the sound, and the invasive components are eliminated.”

Q: Can you give us some insight into how this was achieved on a design-level? 

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We used an enclosure with a carefully selected mass to control resonance, machined from a solid billet of aluminium. This helps shield the internal assemblies from external acoustic, mechanical and electrical disturbances. The PCB is then decoupled from the enclosure using a purpose-designed PCB mechanical decoupling system. Compound dual isolation from residual vibrations provides the filter components with the best operating environment to maximise SIGAO DRIVE’s performance. 

A 4-layer PCB is specified and designed to minimise susceptibility to external electrical fields while not increasing the signal path capacitance unduly. Filter inductors are custom manufactured to Kudos specification and built to a very tight, exacting tolerance. We’ve opted for capacitors using polystyrene dielectric, considered by Kudos Audio to be the best sounding in our crossover filters.

Q: One of the principal goals of SIGAO DRIVE was ‘universality without compromise’, both with the Kudos loudspeaker range, and with other electronics brands. How has this been realised? 

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“Versatility was very important. SIGAO DRIVE has been designed so that it can be configured for use with any speaker in the current Kudos range, and with almost all power amplifiers available on the market today. This versatility allows simple external adjustments for compatibility with any upgrades within the Kudos loudspeaker family.

This crossover is also very intuitive. With no interaction between the mid frequency, treble attenuation and power amplifier matching functions, setup for various speakers is made easily understandable and achievable.”

Our warmest thanks go to Roy George for taking the time to answer our questions. 


If you’re wondering what this unique design and engineering process means for your listening experience with Kudos, there’s only one thing to do. Come and hear SIGAO DRIVE for yourself.

SIGAO DRIVE’s official launch takes place at MotorWorld in Munich on Thursday 9th May – coinciding with Munich High End 2024. You’ll be able to hear and see SIGAO DRIVE there, and we’d welcome you to come and visit us in the Hans Joachim Suite at MotorWorld, just across the street from the MOC, to hear the future of listening with Kudos. 


We also have a series of upcoming in store events, where SIGAO DRIVE will be on display for demonstration at a range of local Kudos Audio HiFI Dealers. Head to our events page to find your closest in-store event!