Inside Track: Bluacs, a New Low in Car Subs

OEM (Original Equipment Manufacturer) car audio systems have to impress listeners in the most cost-effective way possible. In the past, this meant low power compared to what can be achieved in the aftermarket, typically resulting in poor low-frequency extension from so-called ‘under-seat’ active enclosures. Or if they could dish out serious sound levels, then they were hideously heavy and/or power-hungry, giving your car’s suspension and/or alternator a hard time.

However, some years ago, an Australian company called Blueprint Acoustics (Bluacs) developed a new approach that suits OEM applications right down to the ground. The crucial difference was in its relationship with business-to-business licensors, rather than being a conventional speaker brand. It sold its smarts to companies like Alpine, which in turn supplied the tech to its OEM customers such as Aston Martin.

Remember when Aston Martin introduced the Cygnet in 2011, aiming to reduce its average fleet CO2 emissions? This tiny tarted-up Toyota Aygo hatchback was treated to an Aston Martin badge, fancy upholstery, quilted leather throw cushions in the back and a posh sound system. The problem for the British auto maker was that it had to fit a hi-fi with a target weight of under 6kg – otherwise the little car would have had to go through the process of homologation again. This would have been so costly that it simply wouldn’t have been worth it just for the sound system.

Bluacs works in applications such as these, allowing OEM subs that are custom-designed to cars to be unobtrusive yet effective. The result is that it’s now involved in installations for many car audio brands, such as Bowers & Wilkins and KEF, currently. These companies use the term ‘Fresh Air Subwoofer’ in their documentation, but never provide any details. They work so well that high-end speaker makers and top model cars, such as Polestar’s new 5, the flagship Volvo EX90 SUVs and Lotus’s finest, are also using them.

THE DESIGN

Alpine’s description of the sub reads ...

The subwoofer’s port is set up outside the car cabin and the entire cabin is treated as a giant enclosure, thus allowing a reduction of speaker size by as much as eighty percent. It also enables a ten-fold increase in sound pressure in the ultra-low frequency range, reproducing sounds below 60Hz that regular subwoofers cannot match. Vehicle-specific optimal frequency characteristics can be set with the precise amplitude control function.

It is effectively a bandpass box mounted within the monocoque of the car, using the bodywork as a kind of infinite baffle. Inside the box is a single transducer. In the first one I heard, in the original Volvo XC90, there’s a 10” carbon fibre driver. Both rear and front chambers are ported, with the rear one venting to the outside world – or fresh air, in other words. The front ports into the car and allows the lows to flow. And that’s the difference – there is literally a hole in the car, going to the outside. This is hidden away under a bumper or suchlike, and makes for a distinctively sophisticated sound with little outside-the-car noise disturbance. The system has been continuously developed, with Bluacs moving towards using fewer materials for lower mass.

You cannot test the sound of Bluacs subwoofers in isolation, yet despite the lack of trouser-flapping power, they sound tremendous. The Lotus Eletre S installation sees a KEF system comprising 8” drivers in the front doors and a Uni-Core double-driver bass unit in the front. It delivers a rich and impressive full-bandwidth sound, with a key part of the experience being the bottom octaves.

For example, music by Yello has deep low-frequency information, which in the Electre S feels and sounds right, like a well-matched and set-up domestic hi-fi system should. The engineering is thorough, with carbon fibre cones delivering fast, low-colouration sound and great soundstage depth. Bass grip and weight are excellent, seemingly perfectly calibrated to the car. So look out for Bluacs’ Fresh Air Subwoofer technology in your next vehicle. The ever-expanding number of autos that are appearing tells its own story.

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