50 Years of Home Audio Innovations

Some would say that audio has not changed much relative to other technologies. While audio does not change at the pace of smart phones or computers, audio can trace it’s biggest innovations to the semiconductor industry and digital technology. For this list I have excluded disc based source product from the LP to the CD to the DVD to Blu Ray etc. That is another topic by itself. Until then, here are my top ten. 

1. Transistor Amplifier

Arguably, the transistor amplifier brought about the biggest change home audio has experienced in the last fifty years. The vacuum tube amplifier, while still beloved today, is much more expensive per watt than the transistor based design. During the 1960s and 1970s the availability of inexpensive high powered amplifiers enabled the loudspeaker industry to create smaller, better sounding “bookshelf” speakers which became very popular. (Those were the days of loosely regulated power ratings. In the interest of marketing bravado transistor amps were rated with super high wattage numbers. They were really just forty or fifty watts, but that was still substantially more than common tube amps.)

2. Acoustic Suspension Loudspeaker

The Acoustic Research acoustic suspension loudspeaker was really made viable by high power amplifiers. The acoustic suspension design shrinks the size of the box and makes the driver suspension very loose so the air inside the sealed box becomes the spring that supports driver as it reproduces bass. The design enables a much smaller speaker relative to say a large Klipschorn, to have good bass. The trade off of output level is made up by the increase in amplifier power.

3. High Powered Transistor Amplifier

By the 1980’s the compact disc had made possible a huge improvement in dynamic range. Great sounding, cost effective transistors were also available, and companies like Carver and ADCOM where making high powered amplifiers of 200 watts per channel for reasonable costs. Now systems could play very loud without distortion. This then drove the loudspeaker manufacturers to improve the dynamic range that their speakers could reproduce. 

4. Subwoofer/Satellite Systems

A wonderful thing happens when you design a dedicated subwoofer for sound below 100 Hz. The size of the speakers that you need to cover the upper six octaves of music can be made very small. Bose introduced the AM-5 in the mid 1980’s and home loudspeakers were never the same. While not a new acoustical concept, the three piece satellite subwoofer system turned out to be a major innovation in home loudspeakers. 

5. Matrix Surround Technology

Surround sound entered the home with Dolby surround which added two surround speakers. Dolby surround evolved into Dolby Prologic which added the center channel and intelligent steering to improve perceived channel separation. A HiFi VCR gave you stereo for the 4-2-4 matrix.

6. Powered Subwoofer

Everyone wants more bass. Start with a sub/sat system, build an amp into the subwoofer, and give it a VOLUME knob. Now it goes to eleven! Want more bass, just turn it up! The other major benefit to a powered sub is the ability to equalize the frequency response of the sub amp to get more low end extension.

7. Discrete Surround

When the DVD came home to roost we were able to enjoy 5.1 discrete surround. Unlike Matrix surround, which I like to call “steered mono”, discrete surround enables the sound designer to wrap the listener in a 360 degree sound field and then pin point sound against that back drop. Hey, that sounds more like sound in the real world! Stereo surrounds and great bass management also improved the quality of the reproduction.

8. Class D Amplification

Do you need greater efficiency, want to help save the planet, and to fit more power inside a loudspeaker enclosure? Class D amplification can help. Class D is not always a digital amp; it is another method of using transistors to make a sound louder. Old school class AB amps waste half of the power they suck from the wall. Class D amps can use as much as 90% of the power they draw. This means more power in small boxes and reduced cost. All while burning less coal.

9. Room EQ

Can you make the acoustical effects of a room disappear by using a magic chip? Well no, but recently a slew of technologies have reached the market that measure the effect of loudspeaker room interaction and then equalize or otherwise modify the electrical signal to improve the sound. We are still not creating sound worthy of the Star Trek holodeck, but keep an eye on DSP and room acoustics. It should continue to get better.

10. DSP Powered Loudspeakers

Semiconductor manufacturers now create DSP chips with the equivalent of millions of transistors that can be used to optimize the signal being sent to a loudspeaker. It is truly amazing how good some $200 iPod docks sound. That is due to the marriage of digital signal processing and the acoustical system. No, your basic iPod dock does not sound as good as a high end system. But it does the trick for many. Now what we need to do is harness all that digital power and start to drive the state of the art in audio playback.

So that is my top ten. Leave a comment or send a tweet with your list?

Other Technologies to watch:

Wireless audio 

Airplay

Streaming media sources