Wave Technology – MaxxBass® and The Missing Fundamental of Bass
By Pat Turnmire
One of our goals at Car Audio and Electronics is to introduce new technologies that we think will have an impact on the industry and ultimately everyone who enjoys car audio systems. MaxxBass® is so new you can’t go out and buy it for your car yet (ed.-actually, now you can!); however it’s exciting enough that we wanted to give you a glimpse of what it can do . There are currently several companies developing products with MaxxBass. As they get closer to introduction we will give you a heads up on who has it and where to find it.
A Brief History of Bass
Humans have been in love with bass since they learned to make music by striking sticks on animal skins stretched across hollow logs. Bass, from the boom of an ancient bass drum to an electric bass guitar, has always captivated us in a way that still seems hard to define. Our love of bass has driven an on-going search for ways of creating more and better low frequency sounds. Virtually every instrument created since the beginning of time has had a low bass producing example. Drums, horns, woodwinds, stringed instruments — all have a version that is intended to play predominately bass frequencies. The goal each of these instruments has always been “louder” and “lower” bass. This search came to a peak in early middle ages when the first pipe organs were created and installed in cathedrals. Going to church in the Middle Ages was pretty much the social high point in everyone’s lives. It of course filled the spiritual needs, but it also was an opportunity to see and hear things that you couldn’t get anywhere else. It was in many ways, equal part spirituality and entertainment. The pipe organs that were installed in the larger cathedrals offered a whole new level of experience for the bass fanatics of that period. For the first time they were able to hear and, more importantly, feel low bass that was at the very limits of their sensory capabilities. The bigger churches and cathedrals could seriously rock their congregations. They had huge pipes that could produce “pedal tones” or really really low notes at levels that shook bodies much like car audio systems do today. From the churches’ standpoint, all this bass was just what they wanted. It drew big crowds and moved the congregation in the same primal way that drums and other loud bass instruments have done since the very beginning. As more and more churches added these huge pipe organs into their designs, people came to expect this physical experience of music to be a part of their worship.
The problem was that only the biggest churches could house the pipes necessary to achieve the really low pedal tones. Some of these pipes were 40 feet long and a full set would take up a large area. In fact the problem with getting bass in small churches is very much like the one we face in our modern car audio systems. The key issue in both cases is how to fit big transducers in small spaces.
The Missing Fundamental
In the early 1700’s some composers of written music, specifically for pipe organ, found that they could “trick” the listener into hearing low bass tones that weren’t really there if they played a certain combination of notes that were higher than the low tone or “fundamental” that they wanted to be heard. For example, if they wanted the listener to hear a low C then they could play a C an octave higher and a G above that, and the low C would magically appear in the listener’s head. This phenomenon revolutionized the way organs were designed over the next 200 years. Instead of building massive pipes to create the low pedal tones, designers could make different notes sound when the low note was hit on the keyboard; and the low note would magically appear as if it were played on the big pipes. While this effect wasn’t perfect — these phantom low bass notes didn’t exactly shake the room — they did make the music writing for the largest pipe organs still sound good in smaller churches.
The actual mechanics of the “Missing Fundamental” have been investigated by such notables as Helmholtz (the guy who figured out how tuned tubes or vents work), and has been the subject of many studies that tried to define how we hear musical notes. The most current theory suggests that our ears really don’t hear single pure notes directly, but rather hear them as the combinations of their harmonic content. This suggests that it is possible to completely convince our ears that we are hearing a pitch that is not really there, if they are given the right combination of harmonics. In fact, if this is true then it should be possible to do the same thing in our car audio systems that organ designers were doing for small churches: get more bass from smaller transducers, or speakers.
In 1995, Meir Shashoua, the CTO of Waves (the leading company producing computer-based audio signal processing for professional applications) developed the theory describing the exact combinations of harmonics required to produce the missing fundamental effect. This technology was patented in 1999 (5,930,373) as a method for creating a “psuedo low frequency psycho- acoustic sensation” — in other words, tricking your ear into hearing bass that isn’t really there.
One of the first applications for this technology was an effect Waves called MaxxBass that is applied in the recording studio on computer work stations. It gave bass drum tracks more kick with less speaker excursion and made bass tracks sound more “punchy” and dynamic. This was first used in 1999 and has now become a standard tool used on many of the top CD’s made in the last few years. If you have listened to “Lady Marmalade”, by Christina Aguilera (if you haven’t, you must have been in a coma), then you have heard MaxxBass used as an effect.
Waves knew that the their technology was more then just an effect to be used in the world of recording studios. In fact they believed that it could be incorporated into consumer products, changing the way the world of audio designed products that make bass. The key to making this happen was to offer an inexpensive real time solution for MaxxBass that did not require a computer audio workstation. In late 2001, and after three years of development, Waves completed the MX3000AS MaxxBass ASIC (Application Specific Integrated Circuit), an inexpensive, tiny surface mount IC that incorporates all of the power of MaxxBass to harness the
Missing Fundamental phenomenon.
What MaxxBass is Going to do for Car Audio
MaxxBass changes all of the rules that we have learned about making bass in our car systems. It lets a 4 x 6 door speaker which usually can only play down to 80 or 90 Hz sound like it is playing all the way down to 40 Hz. In fact it makes us hear all of this bass while the speaker is actually moving less. This is because all of the frequencies below the point where the MaxxBass effect starts (called the Fc) are actually rolled off with a crossover built into the chip. So the bottom line is you get more bass and less speaker excursion. This means your speakers play louder and lower!
The MaxxBass effect can be used on systems of any size. Factory systems with a small external amp will sound like you added a small subwoofer. Upgraded door speakers with a multi-channel amp and small subwoofer will sound like you added an even bigger subwoofer. MaxxBass gets even more exciting when complete systems are designed around the technology. When your speakers don’t need to play really low, you can design them to be much more efficient. In a paper presented to the Audio Engineering Society (AES), Martin Collums, a well respected acoustical engineer, calculated that a MaxxBass designed speaker system with 5” speakers would be 7.5 dB more efficient then the equivalent standard design and ultimately play 6 dB louder. This new technology isn’t a replacement for the chest-thumping low end that you get from a row of 12” subs with a couple thousands watts of amps driving them. That kind of bass is as much felt as it is heard. However, if you don’t have the room for that kind of system, a product with MaxxBass will let you “hear” more bass.
Where Do I Get It?
As we said in the beginning, MaxxBass is so new that you can’t go out to your local car audio store and buy a product that uses it (ed.-again, now you can!). Currently, there are a handful of companies that are developing products with MaxxBass built in. The products will come in a wide variety of types and applications. Multi-channel amps, preamp/processors, and stand-alone MaxxBass processors are some of the products on the drawing boards now. Over the next year, you will begin to see it in more and more aftermarket products including head units and ultimately in OEM products. You can find out more about the technology by visiting the Waves Web site at www.maxxbass.com.
How It Works
The graphics on the previous page show a typical application of MaxxBass for car audio. The speakers are commercial 6” coaxes with an F3 of 80 Hz. This means that for all practical purposes they really don’t play much lower then an octave above low E on a bass guitar (41.2 Hz.) The speaker in this example has an Xmax of 8mm which makes it at the higher end side of speakers of this type.
If we play some music where there is a strong single note of bass at 40 Hz you can see that there is a single line of energy at 40 Hz and the speaker is right at its excursion limit. Because of the speaker’s relatively small size it is unable to move much air at 40 Hz; and you are barely able to hear this note as part of the music.
When we pass the same signal through a MaxxBass processor, you can see that the 40Hz signal is reduced about 6dB, and the harmonics related to this signal are created in the proper spectrum for your ear to hear the 40Hz note. The speaker’s excursion is reduced by four times to 2mm which means the speaker will take four times more power before it hits its excursion limits. Now you actually hear the bass in the music as your ear is tricked into creating the sound in you mind. More bass, high power handling and higher SPL’s before distortion — money for nothing and your bass for free.
(©2004 by Car Audio and Electronics. Reprinted with permission)