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The Bose Wave Radio

Incredible sound from a small package

by Julian Edgar

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The Bose Wave radio has been around for nearly a decade, yet it still uses unique technology. It's also an audio device that has in equal numbers both contemptuous detractors and people who simply worship its sleek lines. No one who listens to it ever remains ambivalent about it, anyway!

At its simplest, it can be described simply as a large clock radio (another model adds a CD player but otherwise looks identical). But at its most complex, it can be regarded as one of the most sophisticated small music systems in the world.

I first heard the Wave Radio at a show stand six or seven years ago. I can remember listening with disbelief as this little radio simply cranked out full-bodied music - for its size, making a quite unbelievable sound. The heavy radio was pushing so much bass that it was literally vibrating its way along the shelf on its rubber feet... and all from just a pair of little 2-inch drivers! But just as my excitement was rising, I realised the price: around AUS$650.

For a clock radio. Ouch....

Time passed - but I never forgot that Bose radio.

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Then one much more recent day I found myself in a hi-fi store, listening to it all over again. Often when you have heard in the past something that you thought sounded good, revisiting it is like catching sight of an old girlfriend - you suddenly realise that time has improved your memories. But in this case, the Wave Radio still sounded extraordinarily good. And - furthermore - I figured that it if it went on to find duty as my PC's speaker system, it could now also be claimed as a tax deduction. An additional incentive came when I offered AUS$600 for the store demo model (it had a slight scratch on it) and received a counter-offer - for AUS$580!

So, after all those years, here I am with the Wave radio.

Black or White

Available in either black (good looking) or white (a bit odd in appearance) the Wave radio is unique in its styling. For the tech heads, its shape is doubly attractive because its mixes functionality with style. Inside that odd-shaped body is a very long acoustic waveguide - more on this in a minute. At 35.6 x 21 x 10.6cm, the Wave Radio is quite a large clock radio, although it's small for PC speaker system and even smaller for a household sound system!

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And right there we've put our finger on one of the problems with the unit - and the reason that people seem to either love it or hate it. Categorise it as a full-blown sound system and you'll be disappointed; want it just for your bedside table and you'll possibly be overwhelmed by its size; and expect the room-shaking bass achievable with a satellite sub in PC speaker systems and you'll be vexed.

But if you want a compact sound system that you play at mid- to low-levels, and one that faithfully reproduces the full spectrum of frequencies and subtleties of your favourite tracks - then you'll be delighted.

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But we're getting ahead of ourselves...

The Wave Radio comes with a small credit-card sized remote control, receives AM and FM radio, and has a line-level auxiliary stereo input. In addition, there are lots of other features - for example, it has two alarms, you can have a 12- or 24-hour time display, the automatic brightness dimming of the display is adjustable, and there is a programmable sleep function.

But people buy the Wave primarily for one reason - to listen to it.




Technology

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The reason that the technology behind the Wave has remained unique to Bose is very simple - US patent 6,278,789 covers a frequency-selective waveguide, while patent D440,957 covers the complete external shape of the Wave radio. And patent 5,483,689 covers all of the radio's electronics. Throw in extra patents that cover the basic concept of a waveguide working with a speaker and the special loudness equalization circuits, and you have a product that's going to be very hard to legally copy...

But the good thing about patented systems is that while the patents stop other companies from using the same ideas, it also puts all of the information on the public record. And one thing's quickly clear - if your ears haven't told you that this is one trick bit of gear, the patent information certainly will!

Firstly, as with most Bose products, the traditional audiophile idea of having a flat signal derived from the music source, fed through amps and then faithfully reduced by the speakers is thrown right out of the window. A little like a top car system, the Bose approach is to equalise and compress, sum together certain frequencies from both channels, and then feed that artificially enhanced signal to speakers very much tailored to accept the unique signal.

Speakers

Let's start off with the speakers. Forget tweeters and midranges and woofers - let alone subwoofers.

What you get in the Wave are just two 50mm (two inch!) drivers, with the one on the left (as you face the radio) having a slightly wider rubber surround than the speaker on the right. Furthermore, the left-hand speaker has a matte dome, while the right-hand driver has a shiny plastic dust cap. In fact the speakers aren't symmetrical because, despite appearances, the two speakers don't act entirely as a stereo pair. Instead, the left is a full-range speaker while the right is for upper frequencies. Such is the ear's deafness to the stereo separation at low frequencies that it sounds like a full stereo pair - but it ain't.

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Here is the left-hand speaker....

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.... and here is the right-hand speaker. Note the smaller roll surround and shiny dustcap. To the right of it you can see the vent for the waveguide that connects to the rear of the other speaker.

Of course, if only one of the two speakers needs to reproduce full bass, then only that speaker needs to have a 'proper' enclosure. And it sure as hell does! Despite the fact that the Wave radio is only about the size of a shoebox, the 'box' used behind the bass driver has a length of no less than 86cm. To fit such a long enclosure into the radio that has a longest dimension of 35.6cm, the 'box' is in fact a twisted waveguide. The waveguide uses a cross-sectional area 55-60 per cent of the driver, with the convoluted passage being 1.9 cm wide and 7.3cm high. This guide twists and turns its way through the Wave radio, providing a quarter wavelength mode at 80Hz. With the bass components of each channel added together, frequencies of 70 - 300 Hz can be outputted by this arrangement.

And if 70Hz doesn't sound very deep, getting a useable frequency response down to 70Hz from a two-inch driver is simply stunning.

When playing music with a high bass component, it's fascinating to watch the left-hand driver in action. While its cone displacement is very small, an apparently disproportionate amount of air is pumped from its vent, positioned on the far side of the front face of the Wave.

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This inside view - taken from the patent application - shows in pink the waveguide enclosure/port for the left-hand full-range driver. The green area is the much smaller sealed enclosure for the right-hand high frequency speaker (more accurately described as a mid-tweeter). And the blue on the left? That's polyester damping material, presumably of the sort often stuffed into sealed speaker boxes. So what's it doing there? The polyester acts as a filter, blocking out high frequencies from travelling out of the vent, without having a negative affect on bass reproduction.

Another point to notice about the speaker system is how each speaker is angled outwards, helping to create a stereo image.

Bass Compensation

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The block diagram of the circuitry of the Wave radio shows some features not normally found in clock radios! While most of it looks straightforward, it's when the signal is fed out of the 'Volume' stage that things start to get tricky. 'Dynamic Bass Equalisation' occurs for both the upper and full-range speakers - everything that is heard has been tricked-up by this electronic stage. And it's such an important step that it has its very own US patent: 4,490,843. This is Bose's own loudness control.

To understand how it works, first you need to take a step backwards. As anyone who's ever pressed the button knows, the misnamed 'loudness' control on amplifiers boosts low frequencies (ie bass) when the volume control is turned low. There's a good reason for its presence - as sounds get quieter, the ear loses its sensitivity to low frequencies - those below 500Hz. So when a 50Hz tone (deep bass) and a 1000 Hz (piercing shriek) are played loudly, and then both are played again at a reduced volume, people will suggest that the 50Hz tone at the reduced volume is much quieter than the 1000Hz tone. This phenomenon gave rise to a bunch of 'equal loudness' curves developed by Fletchor and Munson - the famous Fletchor-Munson curves, beloved of sound engineering textbooks.

Loudness controls were developed to boost the bass as the volume is turned down, and most followed the Fletchor-Munson curves as to how much compensation to give. But Bose argues that the Fletchor Munson curves don't apply to real music - only to artificial one-frequency tones. They suggest that the curves are especially wrong when applied human voices, resulting in their becoming boomy.

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As you'd now expect, the 4,490,843 Bose patent is all about loudness without boominess. One trick is to only boost frequencies below 200Hz, and the other development was Bose's own series of compensation curves, some of which are shown here. As can be seen, most of the bass boost is between 40-60Hz, while the response above 200Hz is kept flat.

And does it work? Yes, very well. One of the most impressive aspects of listening to the Wave is at low-mid listening levels. In this situation the sound is superbly full-bodied, with none of the reediness common to most radios and also none of the booming bass resonances that can be heard from an over-eager loudness button. However, it's not a system that takes kindly to fiddling with the input signal - running my Wave from my PC sound card, I've found it best to leave the settings like 'TruBass' and 'Wow Effect' strictly alone...

The compressor circuit - that can also be seen on the block diagram - is arranged to detect the beginning of amplifier overload, and reduce volume accordingly.

Specifications

While the Bose patents and the company's own publicity material highlights many technical details, no comprehensive specifications listing is available. For example, what is the peak audio power? The maximum amplifier distortion? If it sounds great that doesn't matter, but it'd still be interesting to know... Mains power consumption is listed at 50W, so max audio power is unlikely to be more than, say, 30 watts. However, the Wave radio is literally capable of filling a house with sound, so the little speakers are certainly efficient.

Conclusion

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If you really aren't much into technology and just want the best dollars bang for your bucks, then the Wave Radio is an extravagance. Better in that case to just buy a conventional $30 clock radio and spend the rest on a mini sound system. After all, the same dollars will buy you a system with "super woofer drive, 5-discs CD changer, feather touch auto-reverse decks, 24 station AM/FM preset memory, 160 Watts x 2 RMS and remote control"!

But if you want to listen to music relatively quietly (say, while you're working), and want to hear all those subtle nuances and musical details coming from a technological masterpiece, the Bose Wave Radio is worth a listen.

Yep, even after all those years.

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