Musicar has been using this amplifier/processor in 676 BMWs for almost three years. We bring our years of experience in tuning high-performance DSP-driven audio systems (music systems are our core business, not backup cameras or home theater).
We offer this upgrade in two configurations:
- 3-way systems, powering the front, rear, and underseat speakers
- 4-way systems, where we “band-pass” the underseats and add a true subwoofer and dedicated sub amplifier
In either configuration, we ditch the center speaker. It’s playing only mono audio – it’s not getting a “steered”, synthesized vocal channel like in the 688 HK systems. Technically, it’s combining the left channel audio and the right channel audio and playing that summed signal through the center. This means that sounds which should be coming only from either the left or right sides also come from the center of the dash – ruining the stereo illusion that so many recordings have embedded in them.
Instead, we optimize for the driver’s seat – we use the rarely-used time-arrival and level-matching settings to get a great stereo illusion from the driver’s position (after all, we know that seat’s always occupied!). We also use the definable “parametric” equalization on a speaker-by-speaker basis to get the best driver’s-seat sound possible.
The amplifier uses two different technologies together. Class D outputs are very common in car audio today, since they give us great efficiency and smaller devices. Less common is the Class H power supply – sort of a “continuously-variable transmission” for the power supply of an amplifier. Class H requires a fast microprocessor to monitor the signal coming into the amplifier, and increasing the power delivery capability whenever musical peaks are detected. Since this amplifier uses a DSP IC – basically, a really fast microprocessor – it’s uniquely suited to manage a Class H power supply. The results are 55 watts per speaker of average power (70 watts per into 2-ohm speakers). The front and rear speakers are 4 ohm drivers and the underseat woofers are 2-ohm drivers in the 676 systems, so we end up with 360 watts of usable power (not counting the subwoofers in a 4-way system). This is almost triple the stock amplifier’s power – not enough to smoke the stock speakers, but enough to make a tangible difference in the sound.