I first met Fraser Hiebert and Kurt Porter in 2019 – I was doing training for the Canadian Elettromedia importer at the time, and NextGen of Saskatoon, Saskatchewan, had just picked up Hertz and Audison. We did a “onboarding” webinar with them – back before webinars were cool.
Well, over the next year-and-a-half, I’d hear from Fraser and Kurt occasionally with questions – always really good, I-did-read-the-manual sort of questions, the kind I enjoy answering. I helped them set up a Logic 7-upmixer retention demo system in Kurt’s C-Class, that sort of thing.
This particular client ordered a new 2021 GMC Sierra 2500, and wanted a first-rate stereo system to be integrated with the GMC Intellilink head unit.
The truck came to NextGen almost right off the lot, and great care was taken to protect it in the bay.
The vehicle came with the factory Bose amplified system. This system uses phase equalization to provide good imaging to both front-seat occupants.
Fraser decided to eliminate that processing, start with good old 2-channel stereo, and deliver a one-seat stereo presentation, so a Zen Audio AVB-GM external preamp was used. Like other Zen Audio preamps, this device connects to the digital infotainment network in the vehicle, intercepts messages sent to the Bose amplifier from various devices, and decodes the audio in those messages. The audio is converted to analog and then volume-controlled on the six RCA analog preamp outputs.
In home audio terms, this removes the factory audio system from the analog signal path completely. The audio is preserved in its digital form until after it reaches the Zen Audio’s digital conversion circuitry. Fraser and Kurt configured the Zen to use output channels 5 and 6 for a non-fading signal suitable for subwoofers, with output level of those channels of the Zen controlled by the bass tone control in the GMC Intellilink head unit.
The analog preouts fed the Audison APF8.9bit DSP amplifier. Unlike its predecessors, the APF8.9bit (or “Forza”) has dedicated preamp inputs on a different connector than the speaker-level inputs, for maximum signal transfer. The amplifier is rated at 85 watts per channel into 4 ohms, and in this system it was configured in a staggered-six-channel mode: 85 watts by four channels, and 260 watts by two channels. The Forza amplifier/processor was mounted to matching white “Starboard” PVC, on the back wall near the OEM Bose amplifier.
The Forza served as the DSP system controller, and powered all speakers other than the subwoofers. The front stage was the Audison Voce AV1.1 soft-dome tweeter and AP690 woofer, powered actively with 85WPC to the dash tweeters and 260W to the door midbass drivers.
The Voce tweeter is designed to handle a 2500 Hz crossover point – around an octave lower than the industry average. This provides a warmer sound, it elevates the stage to some degree, and it has better symmetry to the dispersion characteristics in the uppermost octave played by the door midwoofer. That OEM 6×9 midwoofer was replaced by an Audison AP690 6×9 midwoofer, retaining maximum cone area for more midbass immediacy.
Both the midwoofer and tweeter drivers were mounted using custom-made PVC or ABS adapters made by NextGen. “The Canadian winters get a bit cold and icy – these plastics are proof against water damage or temperature-related breakdowns”, explained Hiebert.
This left two 85-watt channels of the Forza for powering the rear coaxial speakers. The 9th channel of the Forza is designated for subwoofer amplifiers, and in this system was routed to the Hertz HCP1DK mono subwoofer amplifier. This amplifier, mounted under the aft end of the center console, delivered a ton of continuous power into the subwoofer load, which was two JL Audio 10TW3 shallow-frame subwoofer drivers.
The 10-inch JL subwoofers did their work inside an MTI Acoustics sub enclosure specifically designed for the Silverado/Sierra crew-cab trucks. Christerfer Pate and his crew at MTI have made quite a name for themselves with high-quality vehicle-specific subwoofer enclosures for full-sized trucks the past few years, and these pictures show how “OEM” this enclosure looks in place.
The NextGen crew did a great job.
We estimated 18.75 hours and charged him that. The whole thing took us 20-21 hours total, we were behind by about an hour. This is mostly because of our major issues with trying to tune it with a new laptop. We would have finished in 17-18 hours most if it wasn’t for disassembling and reassembling the car a couple times trying to understand the problems we were having with the new laptop filtering everything below 100 Hertz. Finally used another laptop and it was fine. Later, we installed new ASIO drivers on the new laptop, and the problem was solved!