October 2001

Upgrading Your Home-Theater System -- Part Two: Loudspeakers

Last month I discussed my preferred method of upgrading a home-theater system -- by adding outboard power amplifiers to the pre-outputs of a receiver. However, as many people will argue, you tend to get the "most bang for your buck" from loudspeakers than from any other component in a system. Thus, it only makes sense that upgrading the speakers in your home theater should reap significant benefits in improving the overall sound of your system. Improving the quality of your loudspeakers will result in similar enhancements to the sound as those experienced by upgrading with separate power amplifiers.

Efficiency

One measure of a speaker that is often overlooked is their efficiency or sensitivity. This is a measure of how loud a speaker can play with a given power input at a certain distance. It is usually measured in decibels with a power input of 1W, which is measured at a distance of 1m. It can also be measured in volts, usually 2.83V, which corresponds to 1W for an 8-ohm load. The rule of thumb is that for every increase of 3dB, the perceived volume of a sound is doubled. Thus a speaker that has an efficiency rating of 89dB will play roughly twice as loud as a speaker that is rated at 86dB when the same input power is applied.

This measure of efficiency is important because most receivers are somewhat "power challenged" due to the inherent compromises that must be made in packaging all of the necessary amplification, preamplification, and processing circuitry into the single chassis of a receiver. Attempting to drive speakers that are very inefficient will cause some receivers to sound anemic and thin. In the worst cases they will distort badly.

Thankfully, most common loudspeakers are relatively efficient with measurements ranging from around 85 to 90dB (although many manufacturers do tend to overstate their speakers’ efficiencies), which should not pose much of a problem for a quality receiver. Please note that efficiency in and of itself is not an attribute that you should base your entire purchase on. For instance, a very efficient loudspeaker can sound very bad and conversely a very inefficient loudspeaker can sound very good providing that it is driven with adequate amplification. And just because a speaker is more expensive does not mean that it will be more efficient. In fact, some very expensive loudspeakers are also very inefficient.

Manufacturers often quote maximum power-handling ratings for their speakers. While speakers that can handle more power are technically better, it is not an indication of how loud the speaker can play or of its quality. For instance, a speaker that is rated to handle up to 200W may not play as loud as a speaker that is only rated up to 100W if it is much less efficient. Just be aware that very inefficient speakers do not usually make a good match for most receivers and that measurements do not always tell the whole story.

Frequency response

When we refer to speakers as being "full range," we usually mean that their frequency response extends down to 20Hz. Just about every speaker’s frequency response extends up to 20,000Hz or more, but reproducing the lowest frequencies that are present on CDs and movie soundtracks is a much more difficult task. Ideally, each of the speakers in a surround-sound system should have bass response down to 20Hz, but achieving this is difficult due to the increased size and cost of speakers capable of this type of performance.

If any speaker in a home-theater array is going to be full range, it will probably be the left and right front speakers. Many people opt for the expense and have the space available to accommodate main front speakers that are capable of bass response down to 20 or 30Hz. However, most people do not have the budget or the space available for full-range speakers at the other positions. While small satellite speakers can make very good home-theater systems, I prefer to have as much bass capability as possible from all of the speakers in a home-theater system.

Good center and surround speakers will have bass response down to at least 60 or 70Hz, which is similar in performance to a decent bookshelf speaker. You might consider upgrading to center and surround speakers that go down to about 40 or 50Hz, which is about the limit to the amount of bass that can be obtained from conventional center and surround speakers. Dedicated, purpose-built center and surround loudspeakers rarely have bass response that extends below 40Hz. Of course, if finances and space considerations are not an object, you could opt for full-range, floorstanding speakers for these applications.

High fidelity

This may seem obvious, but is worth stating anyway. Using higher-quality speakers will result in a more involving and satisfying home-theater experience. For example, an inexpensive "home theater in a box" speaker system from a mass-market manufacturer will usually sound inferior to a more expensive speaker system from a specialty speaker manufacturer. Additionally, using very high-end speakers, whether designed specifically for home-theater use or for two-channel audio, is required for that ultimate home-theater experience.

One common mistake that people often make is neglecting the quality of the center and surround speakers. The quality of both should be commensurate with the quality of the main speakers. With discrete digital soundtracks providing full-range signals to all channels, these speakers are now just as important as the mains. I cannot stress enough how important it is not to cheap-out on center and surround speakers!

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