MaxxBass® in Automotive Audio Systems by Paul Bundschuh

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Waves has developed and patented a technology called MaxxBass® that can dramatically improve bass audio performance in vehicles. MaxxBass® offers the audio system engineer dramatically increased flexibility to improve a car's bass performance or shrink the size, weight and power consumption of audio systems.

“MaxxBass® changes all the rules that we have learned about making bass in out car stereo systems. It lets a 4x6 door speaker which usually can only play down to 80 or 90Hz sound like itis playing all the way down to 40Hz. In fact it makes us hear all of this bass while the speaker is actually moving less.” Car Audio and Electronics – June 2002

Some of the potential benefits of MaxxBass® include…

MaxxBass® can be used on existing door mount speakers to dramatically improve bass range, providing the perceived bass range of a virtual woofer without the size, power and weight requirements of a traditional subwoofer. On vehicles without large resonating chambers (trunks) such as pick-ups, SUVs and hatchbacks a much deeper bass range can be obtained. On vehicles with resonating chambers such as sedans it is still useful to apply MaxxBass® to the front speakers to improve the bass imaging.

MaxxBass® can be used to reduce the size of the speaker driver or enclosure without reducing bass performance. The smaller speakers offer reduced volume, power consumption and weight. These speakers have a higher physical low frequency rolloff, since the deeper bass frequencies are created psycho-acoustically As result the need for precise parameteric equalization to reduce standing waves caused from the vehicle’s acoustic transfer function is also reduced.

MaxxBass® can be used to enable very small, yet powerful subwoofers, called MiniWoofers®. The MiniWoofers® can be designed to easily install under car seats or other locations which traditionally are not large enough for a subwoofer. Waves has demonstrated the MiniWoofer® and will offer reference designs of the acoustic and electronic requirements. Third party manufacturers can also deliver the MiniWoofer® components or a complete turn-key product.

MaxxBass® can enable small, yet powerful sounding center channel speakers to be mounted directly into the space limited dashboard. The center channel is increasing important for imaging on new DVD and multichannel music media.

The MaxxBass® psycho-acoustic bass provides greater perceived volume linearity. The need for a dynamic loudness function to increase the bass level at low volumes is reduced or eliminated.

Waves offers a wide variety of MaxxBass® implementation options with both ASIC hardware and DSP software licensing. The MX3000AS MaxxBass® ASIC is ideal for products that do not include general purpose DSPs, these include low tier CD/receivers, active subwoofers and aftermarket accessory products. MaxxBass® can also be implemented in software of high tier CD/receivers and DSP amplifiers. Licensable software solutions are currently available for the Motorola DSP563xx and AKM 77xx DSP platforms with other solutions in development.

MaxxBass® ASIC (MX3000AS) Automotive Applications

-Low end CD/Receivers
-Active Subwoofers (MiniWoofer®)
-Aftermarket accessory products including cross-overs and equalizers MaxxBass® DSP Software Applications

-High end CD/Receivers
-DSP Amplifiers
The MaxxBass® software should be implemented in one of the last stages of audio signal
processing. Typically only the volume control function should be implemented after
MaxxBass® in signal processing chain.

Waves MX3000AS ASIC is a complete DSP subsystem including stereo analog I/O, sigma
delta analog-digital converters, digital-analog converters and a custom DSP. It only requires
an external clock source using a ceramic resonator and a few external resistors and capacitors for a complete solution.

The MX3000AS can be used in various automotive applications. It can be used as an aftermarket accessory product or integrated into cross-overs, equalizers or amplifiers.

Another attractive option is to combine the MX3000AS in a small active subwoofer. Waves with Redrock Acoustics has developed a MiniWoofer® reference design. The unique MaxxBass® enabled subwoofer shrinks the size of a traditional home theater component subwoofer by 85% with reducing its acoustic output in terms of bass range and system efficiency/SPL. Using MaxxBass® in the acoustic design of the subwoofer allows dramatically improved performance since the f3 can be raised by an octave while achieving similar perceived bass range. Traditionally a high quality consumer home theater subwoofer should have relatively linear bass response (f3) to about 40Hz, while lower cost multimedia subwoofers may only provide linear response to 50-55Hz. Waves with Redrock Acoustics, a well known loudspeaker designer www.redrockacoustics.com, has designed and delivered a new MaxxBass® optimized subwoofer (MiniWoofer®) that shrinks the volume requirements of a traditional high quality subwoofer by 85% with little or no impact on the perceived acoustic quality.

Another attractive option is to combine the MX3000AS in a small active subwoofer. Waves
The details of the MiniWoofer® design include Thiele/Small parameters is available at www.maxx.com. The results of the design effort are summarized here.

Original Reference System

-8-10” driver
-100W maximum power
-1ft3 enclsure volume
-vented enclosure
MiniWoofer Reference System

-6.5” custom driver (lighter driver with less excursion than traditional woofer)
-80W maximum power (same power efficiency as the reference system)
-0.15ft3 enclosure volume
-sealed enclosure
www.maxx.com

Low tier CD/Receivers without general purpose audio DSPs may find the MX3000AS ASIC an attractive solutions to add MaxxBass® functionality; however a software implementation will be more cost effective for higher tier applications with programmable DSP audio architectures. The long term trend of the industry will be to add more DSP into both low and high tier products making the software solution increasingly attractive. The MaxxBass® software solution can be integrated with other signal processing functions including other audio signal processing technologies offered from Waves.

MaxxBass® can be readily implemented on most audio DSP architectures. MaxxBass® software is available currently from Motorola DSP5636x and AKM 77xx DSPs. Waves is also working with other manufacturers to make this available to customers as needed.

The MaxxBass® functionality is DSP efficient in terms of the number of instructions and the
amount of memory required. As a benchmark a stereo implementation of MaxxBass® on the
Motorola DSP563xx requires 180 steps/sample (7.9MIPS @44.1kHz Fs) and about 250
words of combined program and data memory.