In Praise of Sat/Sub Sets

In the best of all possible worlds, I’d get a chance to hear any speaker I review before I review it. In the real world—where even three major trade shows a year don’t offer enough first-hand demos for a busy, quota-driven audio editor to work with—I look at product literature and pictures instead. And the first thing I look at is size.             Would it surprise you to learn that I prefer smaller speakers to larger ones? If you assume that’s because of my workspace, you’re half-right. My 19 by 14 by 9 foot room totals just under 2400 cubic feet, making it more suitable for small and midsized speakers than for big, bulky ones. And I’m the first to admit that, having been through one hernia operation, I’d like to limit the chances of undergoing another one.             But I have many more reasons to seek out small speakers. The magazine I work for, Home Theater, has always paid attention to decor-friendly products—especially now that it’s absorbed its sister title Audio Video Interiors as a supplement. Our readers don’t want their speakers merely to sound good. They want them to look good and fit unintrusively into a lovingly designed room. True, some of them are also looking for heavy artillery in a no-holds-barred basement theater. But, having no basement of my own, I concentrate on the stuff that fits into a multi-purpose livingroom. Like mine.             Moreover, as a critic, I want to go where the action is. In loudspeaker design, the action is in smaller speakers. Sat/sub sets now have a big slice of the home theater speaker market. Designers are working hard to make compact speakers look and perform better.             And, all other things being equal, small speakers sound better than large ones.

Immutable Laws             Heresy! How could an audio critic say such a thing?             I didn’t just pull that out of my ear. I’m just reacting to the immutable laws of acoustics. If you could visualize sound coming out of a speaker, you would see some of it bouncing off the speaker itself, especially the front baffle. This is called diffraction and it’s not a good thing. As this tutorial explains: “Diffraction from the front panel and cabinet edges can have a bad effect on stereo imaging because the time-delays of the diffracted sound are more often than not right in the critical region for direction sensing.” The smaller and more rounded the baffle is, the less diffraction you get, and the better imaging you get—all other things being equal, as I said above.             If all other things are not equal, there are lots of ways for larger speakers to excel in other areas. They might have better driver materials, bigger magnets behind them, or an internally braced and therefore more acoustically inert enclosure. But the only way to save them from diffraction is to make the baffle smaller and break up its straight surface with curves. That’s why so many next-generation floorstanding speaker designs today are slender and tubular. I think of them more as floorstanding satellites than as traditional towers.             Of course, big speakers do have one size-related advantage: bass. The bigger the driver and enclosure (all other things etc.), the more bass you can get out of them. However, designers are finding ways to make skinny speakers produce a little more bass by packing them with high-excursion drivers (which travel greater distances as they move back and forth) and bigger magnets (which propel the drivers more forcefully).             Getting real low-bass response out of your speakers was crucial when you had only two of them. Nowadays, an average surround system has five to seven speakers and a subwoofer. When you’ve got the sub’s 12-inch driver and internal amp pumping out bass, is it really necessary for the remaining speakers—and an already overtaxed receiver—to pump out still more bass? Here I have to give an equivocal answer. You might need speakers with some low-bass response of their own, or you might not.             It depends on a few things. If the shape and/or size of your room make it hard to get even bass coverage out of one sub, you need either a second sub or more bass out of your speakers. In the latter case, you wouldn’t want a compact satellite whose bass response rolls off below 100 Hertz, the crossover frequency used by most small sats. Instead, you would look for speakers with nearly flat bass response down to maybe 50Hz (the lower, the better). It might be a stand-mounted speaker in the monitor or bookshelf class—something chunkier than the slimmest satellites but still less massive than a tower.             Even as a small-speaker enthusiast, I must admit that once you get into larger stand-mount speakers, the footprint will be the same size as that of a midsized floorstander. And larger speakers are harder to wall-mount. Incidentally, the laws of acoustics are also unfavorable to on-wall speakers, because they diffract like crazy off the wall, though in-walls can work well, because the diffraction drops when the drivers go behind the wall surface. Let’s not go there today.
  Receivers Like the Sensitive Type   Another thing that must influence your choice of speakers is your choice of receiver. Unless you want to spend in the low four figures or more for a high-end receiver or separates—something that can put some serious current into the speakers—you want your speakers to be as sensitive (or efficient) as possible.   Sensitivity is specified in decibels, with a test tone measured one foot from the speaker. Most receivers can comfortably drive speakers with sensitivity of 88dB or more. If the spec is given as room efficiency—which factors in room reinforcement—make that 90 or 91dB or more. Any less than that, and either you may not get enough volume for action-movie peaks, or your speakers may drive your budget receiver too hard, inducing harsh clipping or overheating or even shutdown.   The higher the sensitivity, the more volume your speakers can produce per watt. A 3dB increase in sensitivity cuts the speaker’s power demand in half, giving you more dynamic headroom and smoother sound. What you give up is low bass response. That’s why sat/sub sets can’t do without their subs.   Sat/sub sets are, on the whole, the most sensitive class of speakers. However, a lot of midsized and even large speakers also have high sensitivity, because their designers want them to work with affordable receivers. It’s all too easy today to buy a big speaker and discover that it still needs bass reinforcement from a sub. So the real determinant of sensitivity isn’t size but what the speaker designer intended. All other things being equal, wouldn’t you rather have a smaller speaker?   This is the world we live in today: People want as many as seven channels of loud but accurate sound out of their systems. And they want their homes to look cool, which isn’t easy when as many as seven bulky objects jut from the floor. The demands of all those surround channels, the need to make them play at near-theatrical levels, the universal acceptance of subwoofers, the need to get a lot of bang from your buck, and the desire to live with something that looks cool—all these factors have driven the growth of the sat/sub set.             Why settle for less?   Mark Fleischmann is the author of Practical Home Theater, audio editor of Home Theater Magazine, and tastemaster of

The views expressed here are solely those of the author and do not reflect the beliefs of Digital Trends.

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