How Much Power Do You Really Need?

A lot of audiophiles think you're better off with just 8 or 10 watts rather than 100. Are they right? Let's listen and find out!

By Brent Butterworth contributing technical editor of Sound + Vision and former editor-in-chief of Home Theater


In the 21st century, we've gotten used to having everything we want. We demand to hear any tune ever recorded right now. We insist on studio-quality sound everywhere, even when we're on a wilderness hike. But it wasn't always this way. Audio used to be challenging. Back in the days of tubes, and even the early days of transistors, power was precious.

In the 1950s, a typical amp might put out 20 or 30 watts per channel, and that specification often came with a wink and a nudge. To get the most from such paltry power, speaker designers made their products more efficient. Many of the speakers back then gave you 95 to 105 dB at 1 meter from a 1-watt signal, while the average 2011 speaker might give you 86 to 89 dB with that same level of power. Translated: The old speakers played loud as all hell from amps no more powerful than the ones built into a typical iPod dock.

Audio Note Meishu Line Silver single-ended tube integrated amplifier: just 9 watts per channel, but 60+ pounds!

 

Many of today's audiophiles have come to the conclusion that we were better off in the old days, when efficient speakers allowed the use of super-simple, single-ended Class A amplifier circuits. In these circuits, instead of breaking up the audio signal into positive and negative halves and amplifying it with opposing pairs of tubes or transistors (the so-called "push-pull" arrangement), the entire audio signal is amplified by just one tube or transistor (or multiple tubes and transistors running in parallel). Because the audio signal doesn't get broken into two halves, the distortion can be much lower. And the circuit can be a lot simpler, sometimes just two tubes per channel.

But the power's a lot lower, too. A lot of single-ended amps put out only 8 to 12 watts per channel. But if you have a super-efficient speaker, it doesn't matter, right?

This question occurred to me as I was looking through the collection of speakers at Innovative Audio, a Vancouver, BC, vintage audio dealer. A lot of the classic speakers the store stocks have a rated sensitivity of 100 dB or higher, a spec rarely seen these days. In my work as an audio reviewer, I test mainstream, modern product and rarely get a chance to play with old-school high-efficiency speakers. It dawned on me that my visit to Innovative Audio would give me the perfect chance to investigate the question: Which is better, high-powered amps with low-efficiency speakers, or low-powered amps with high-efficiency speakers?

Not only did Innovative Audio have the gear I needed to do the test, it had something else just as important: dedicated customers who'd be eager to give me their opinions of the two systems I'd be setting up.

 

Who You Callin' Low Power?

When I asked Innovative Audio founder Gordon Sauck if he might have a low-power single-ended amp in stock, preferably a tubed model, his face lit up and he immediately directed me to an Audio Note Meishu Line Silver. The Meishu is a current-model integrated amplifier of a design that mimics the low-powered amps of yore. Although it's rated at just 9 watts per channel, it's an absolute beast, weighing in at more than 27 kg. When I removed the lid to sneak a peek at the big 300B amplifier tubes, I counted six transformers; no wonder it's so heavy. Because of the weight and the large chassis, I nearly passed out when I tried to carry the Meishu myself; it's definitely a two-man job.

The Krell S-300i integrated amplifier: Small, but a potent 150 watts per channel

 

Of course, we'd need a very good high-powered amp to go up against the Meishu, but luckily I'd brought my own: a Krell S-300i integrated amp. The S-300i is Krell's least-expensive integrated but it's still a killer, with 150 watts per channel, a beefy power supply, practically perfect measured performance and the sound quality that has made Krell a fave of audiophiles for 30+ years.

 

A Tale of Two Speakers

Then I asked Sauck if he had any high-efficiency speakers, something with a sensitivity rating of at least 96 dB. Big mistake. He started to rattle off the makes and models of the umpteen high-efficiency speakers he had available: Klipsches, Altecs, Pioneers, and more. After the sixth or seventh or tenth one, I stopped him and said, "OK, what would you choose?"

"The JBL L300," he replied, pointing at a floorstanding speaker that looked wider than any of the 1,000 or so models I've reviewed. "The sensitivity is 102 dB."

The mid-1970s L300 was built both for studio and home use. It packs a huge 15-inch woofer powered by a 12-pound Alnico magnet; a horn midrange with a slotted acoustic lens to improve horizontal dispersion; and an exotic horn-loaded crystal tweeter that Sauck told me sells for more than $500 each on eBay. I'd never seen anything like it, except maybe in pictures.

The low-efficiency Image 200 (left) faces off against the high-efficiency JBL L300 (right)

 

The low-efficiency speaker choice was more challenging, because I wanted something that was vintage yet of fairly modern design … something that would have a sound similar to speakers of today but not so new that it might have a huge advantage over the L300. I chose the Image 200, a Canadian-built model from 1988 that happened to be featured in an old issue of StereoVideo Guide I found in Innovative's vintage hi-fi magazine collection.

According to the editors of StereoVideo Guide, the Image 200 had the flattest on-axis frequency response of the 10 models they'd tested for that issue. (What do you expect? It's Canadian!) It also had a measured sensitivity of 86.7 dB. Just what I had in mind! In fact, this tower speaker wouldn't look out of place at a stereo store today. It has two 6½-inch woofers, arranged top and bottom, with a ¾-inch tweeter between them. I couldn't have found a more perfect speaker for my test.

 

The Test

After I connected the Audio Note amp to the JBL speakers and the Krell amp to the Image speakers, it quickly became obvious that this high-power vs. low-power test would have to be more of a fun'n'casual thing than the usual carefully controlled blind tests I like to put together. The speakers sounded so different that I knew everyone would be able to guess which was old and which was new. The Image 200 had a brighter, more detailed sound, while the JBL L300 had the fatter, more robust sound that was common for its time. So there was no point in making this test blind.

Furthermore, the L300's 23-inch width made it impossible to do a simple side-by-side comparison because the drivers of the speakers were so far apart. I had to instruct the listeners to shift themselves on the couch when they switched from system to system, so that their heads would remain centered and they'd get a good stereo image from each pair of speakers.

I used my Denon DVD-2900 DVD/SACD player as the source, connected through a line-level switcher placed by the listening couch so the listeners could easily switch between the two systems. I matched the levels of the systems as best I could; given the significantly different frequency responses of the JBLs and the Images, there was no way to get a perfect match. The listeners got to play whatever music they wanted.

And with that, we had at it….

 

The Big-Power Sound vs. the Low-Power Sound

A test like this wasn't about figuring out which system had the best performance from a technical standpoint, because the Krell/Image system won that comparison easily. No, this was simply about deciding which sound each listener liked the best. It was more like picking your favorite bass player rather than the fastest bass player.

Innovative Audio customer Cam Steere compares low-powered and high-powered stereo systems in the store's second-floor listening room.

 

The listeners described both systems completely differently, yet in ways that complemented both. "The Audio Note/JBL system sounds a lot smoother. I could listen to it all day. But the treble and the imaging are so much clearer with the Krell/Image system," one listener said.

"The JBL system has a much rounder tone," another listener opined, "while the ambience is a lot more realistic with the Image system."

"I like 'em both," a third listener said, "but they're so different. For my taste, though, I like the low-powered system better. It takes me back to my high-school days, listening to James Taylor and stuff like that. It really has a classic sound."

When I played my test CD full of tough-to-reproduce snippets of stereo music, I found the Krell/Image system superior in every area of performance except bass extension. Case closed, right? Wrong. After a while, I noticed that every time I wanted to catch up on my note taking, I reflexively switched to the JBL/Audio Note system. Yeah, it sounded a lot less detailed than the more modern Krell/Image system, but it had a great groove that made for a more relaxed and comfortable listening experience.

Despite the Audio Note's tiny 9-watt power rating, not a single listener complained about dynamics or volume. It played plenty loud through the JBLs.

 

Will the Meek Inherit the Listening Room?

I hate to declare a clear winner here, because this was just one of the nearly infinite number of high-powered vs. low-powered comparisons we could have done. There were thousands of different amps we could have chosen. Thousands of different speakers we could have chosen. The differences in the sound of the speakers alone were huge, and it'd probably be impossible to correct that flaw in our test. After all, most of today's high-efficiency speakers use horn midranges and tweeters, while most low-efficiency speakers use standard cone midrange and dome tweeters. Two completely different sounds.

But while the listeners had no problem finding the technical flaws in the Audio Note/JBL system, five of the six said they'd prefer it over the Krell/Image system.

This doesn't mean low-powered/high-efficiency systems are always better, just that they're well worth considering. But there is one thing this test proves for sure: Sometimes a little old-fashioned soul beats out technical brilliance.

 

To read more of Brent Butterworth's reviews and insight on products, check out his blog on the Sound & Vision website by visiting here