Automotive Mobile Audio Video

The expectations of both drivers and passengers for electronic entertainment, communications and information have escalated since the introduction of the pioneering first practical auto radio, the Motorola branded AM car radio introduced in the 1930s by Galvin Manufacturing (who later changed their name to Motorola).

The latest cars, SUVs and trucks offer stock and premium entertainment packages beyond our wildest visions. DVD video with multiple fold fold-down LCD panel displays with fiber optic interconnection, navigation systems, Satellite/HD radio, mobile video and, THX surround sound.

Next generation electronic features and functionality will lend themselves to OEM equipped vehicles as designers struggle with size and weight reduction, long-term stability, environmental robustness, integration into larger assemblies and subsystems and the occasional request for cost down.

The Final Frontier

Interior space continues to get scarce and autosound aftermarket installers this year are confronted with a number of vehicles with none of the usual odd corners to install amplifiers, subwoofers and other electronic boxes. But while the OE interior engineers get to the scene first, the land grab is just as intense. While dashboard space is being eaten up by climate controls, air conditioning, air bags, navigation displays and so on, audio engineers are finding innovative technology in both audio electronics and speakers that provide significant space savings.

Until Panasonic introduced the first in-dash receiver utilizing high-power switching amplifiers this year (MXE CQ-C9800U CD receiver, 60Wx 4). the commonmost head end units was were limited in fewer than 20 watts per channel (with Alpine's V-Drive the former champion, at 26W x 4). Additional power and channels required amplifiers under the seat, built onto the speakers, or crammed into some other available space.

Higher power, in-dash head-end units have three significant implications for OEM designers. The Panasonic head unit offers more real power then many outboard amplifiers. A big impact is the space and heat savings. With the extra space created by getting rid of the heat sinks, OEMs can add better digital signal processors and bigger LCD monitors.

Switching amps allow for more channels in the head unit. Some OEMs are already looking at six channels for in-car-theater, but what about eight or 12 channels? With the horsepower in the DSP, active crossovers can be used to amplify each speaker driver separately while still fitting into a normal, single-DIN package.

The Panasonic uses the Tripath 60 W x 4-channel module, which features a built in DC-DC converter as well as Class T operation. "Class T" is Tripath's name for their low distortion, hall range sophisticated variation of Class D switching amplifier technology which is used by Panasonic and quite a few others, mostly in home theater and large screen TVs. Other vendors for switching amplifier ICs include Texas Instruments, and Apogee and ST.

Class AB amplifiers are by far the most common car amp design. Switching amplifiers (Class D) boast higher efficiency (some approaching 90 percent), produce less heat, and draw less current than traditional Class AB designs. Because they produce much less heat, Class D amplifiers can be housed in a much smaller chassis than a Class AB with the same power output.

For example, Tripath's newest module is 4 x 100W and would be generating about 400W of heat if it were an AB amplifier. Adding the signal output power and the heat together, it's pulling 800W from the battery. Changing to a switching amp, that same 800W from the battery can deliver 720W to the speakers, creating a 4 x 180W amplifier without pulling any more power, and only generating 80W of heat. Or in the case of the Tripath module, 400W of audio and about 40W of heat.

As miniaturization and density increase, satellite radio, communication systems such as on-Star and equivalents, and the hands-free cell-phones can be integrated into the head-end unit.

Signal Processing

With the newfound space in the head unit we now have more room for signal processing. The most basic signal processing is already in the head-end unit and can take the form of tone controls like bass and treble, and other functions to balance the sound from front to back or side to side. More sophisticated spatial signal processing is offered from SRS Labs like their Focus, which can bring the sound from your ankles (where the car door speakers are) to in front of you. THX, who originally developed standards for movie theaters and expanded to home theater, now has standards for autosound surround sound. Surround sound makes sense for cars as most vehicles already have speakers positioned in the front, sides and rear.

One of the most promising new signal processing techniques is MaxxBass. MaxxBass can provide a "virtual" subwoofer without the extra amp and subwoofer.

MaxxBass is an algorithm that utilizes the psychoacoustic "Phenomenon of the Missing Fundamental" to extended perceived bass frequency response by up to 1.5 octaves. In auto sound, MaxxBass enables door-mounted woofers that typically drop off below 80-100 Hz to sound like they can play down to 40-50Hz, giving consumers a subwoofer sound without the cost, size, power and weight previously required. This bass processing delivers more perceived bass while simultaneously reducing the likelihood of damaging speakers and amplifiers as woofer excursion requirements are reduced. Reduced displacement in woofers cone for a given apparent volume also translates to reduced woofer depth.

# posted by Medical Information : 2:39 AM