Free-standing or Box speakers

What do you envision when you hear the word "speaker"? I know some people think of a person on a podium addressing an audience, but for those of us in the audio and video realm, we think of something that generates sound - the final link in the process that starts with a microphone and enables sound to be captured, transmitted, and replayed.


And for most of us, that thing looks like a box.

We'll talk about other options (in-wall, in-ceiling, etc.) in another article. But right now, I'd like to talk about this most common type of audio speaker.

In previous articles, I talked about the different driver types (cones, domes, horns, ribbons, and others). The box is really just the enclosure that houses the driver and associated electronics.

However, that box is also an important element in the acoustical properties of the speaker. If the box is the wrong size, shape, or made of the wrong materials, it will affect the efficiency and the sound quality of the speaker.

For example, many speaker enclosures are made of MDF (medium-density fiberboard) covered with a lacquer or wood laminate. The lacquer or laminate is to help the box look good in your living room (MDF is not very pretty!). But the MDF is what really provides the acoustical properties.

The box itself serves as a resonance chamber and contains the sound emanating from the back of the speaker. This enclosure needs to be made of an acoustically inert substance to reduce "sympathetic vibrations" which can lead to the speaker "walking" across the floor, or even shaking itself apart! Lead or concrete would be excellent, except they're too heavy. MDF, on the other hand, provides a reasonable balance between weight and acoustical properties. Some manufacturers make their enclosures out of other materials as well. For example, high-end speaker manufacturer James Loudspeakers makes the enclosures out of aircraft aluminum, which has excellent audio qualities. But they still have to make a nice-looking outer shell.

The construction of the box is important, too. It needs to be completely sealed, or some of the sound will leak out of the enclosure instead of being sent in the direction of the listener. This keeps the sound from the back of the speaker from mingling with the sound from the front of the speaker. This is important because the speaker actually creates sound both when it moves forward and when it moves backward. The sound created by the backward motion is 180 degrees out of phase with the forward sound, which means if the two mingle, they will cancel each other out!

If you'd like to learn more about which speakers are right for your home theater or audio setup, please visit us online, or call us at 847.471.4420.

An overview of Horn Speakers

Horn Speakers are often considered to be of excellent quality, but the reality is that quality varies greatly depending on price and intended application. There are a couple of high-end speaker manufacturers such as Klipsch and Fostex that have well-designed horns, but remember that horns are also used in bullhorns and low-quality outdoor loudspeakers, which have very limited ranges.

Horn speakers use the interaction between the horn and the driver to increase the efficiency of the speaker. This allows a speaker to generate a higher volume for the same power input and distortion level. However, the same properties that increase the voume limit the frequency range. So a bullhorn can generate a high volume of sound using small batteries, but only in the frequency range of the human voice.

In order to compensate for this, some horn speakers use multiple drivers (with appropriately tuned horns) to cover the entire frequency range. Others use horns primarily for one frequency range (e.g. for the tweeters), and use standard cone drivers for the rest of the frequency range. Most Klipsch speakers fall into this category. Of course, there are always some manufacturers that save money by not adequately covering the entire range of hearing.

If you're looking for horn speakers or any other type of speakers for your home theater or home audio system, visit Inspired Electronics, Inc. on the web!

A little about cone speakers

The most common type of speaker is a cone speaker. This speaker has a diaphragm made out of a cone of a fairly stiff material, such as paper, polypropylene, carbon fiber, or aluminum, although other more exotic materials have been used. The diaphagm moves back and forth, pushing air out into the room, generating the sounds you hear.

The best material for a speaker cone is something that has low mass, good stiffness, and good damping properties. The low mass improves the speakers efficiency, meaning less power is needed to drive the speaker. If the material is not stiff enough, it won't generate clean sounds, especially at higher frequencies and higher volumes. And if there's not enough damping, the speaker will have a characteristic "ringing" sound.

Interestingly, paper is a good speaker material, because it has all of the properties needed. However, paper has the disadvantage of not handling moisture well (including changes in humidity). Polypropylene is used often in in outdoor or high moisture applications. Aluminum and other metal cones are light and stiff, but often don't have sufficient damping properties, and can sound too "bright". Fiberglass, Kevlar and Carbon Fiber have good properties, but can increase the cost of the speakers. So if you're interested in good speakers, and willing to pay a little more, we often recommend these materials.

The mechanism that moves the cone back and forth is a large magnet and an electromagnet. These two work together to vibrate the cone, compressing and decompressing the air, and generating sound waves. Note that the speaker generates sound in both directions. Since the reverse direction is exactly opposite the forward direction (180 degrees out of phase), care must be taken to ensure the reverse sound doesn't cancel out the forward sound!

In order to provide a stiff frame for the magnets to drive against, the speaker has a "spider", which is a stiff cage. Many spiders are made from a stiff plastic, while others are made of aluminum or another metal. At one time, spiders were made of Bakelite, but plastic and aluminum are much more durable. Plastic is light and inexpensive, but can distort under high load (high volume).

Speakers also have a flexible surround which binds the cone to the frame. This surround also keeps the sound generated by the reverse direction of the cone from coming around to the front and canceling the sound generated by the forward direction. In many older speakers, the surrounds have degraded to the point where this happens, and the speakers need to be repaired or replaced.

I'll talk more about speaker types and speaker design in future Blog postings, so stay tuned!

In the meantime, visit us on the web to learn more about how we can install a home theater or distributed audio system for you!

The importance of speakers

If you're listening to music, watching TV, or even talking on the phone, you're using speakers. Speakers, after all, are what translates recorded or broadcast material into sound waves that you can actually hear.

And the quality and type of speakers has a tremendous impact on how good that material sounds.

For example, have you ever sat on hold listening to your favorite song? I'll bet you found it at least somewhat annoying, because you couldn't hear all of the nuances of the music that you're used to.

That's because telephone speakers (in the earpiece, or even on a speakerphone), are not what we call full-range speakers. They're only designed to reproduce the human speaking tones, which range from about 110Hz for a low male voice, to about 1000 Hz for a higher female voice, up to about 3000 Hz for a child's scream.

On the other hand, the full range of human hearing is from about 20 Hz to about 20,000 Hz (20 KHz). Good full-range speakers reproduce all of that sound, and the entire range is used in music and movies. If you're not hearing the upper and lower ranges, you're missing a lot of important information in the sound track - and it just doesn't sound good!

Now, consider the speakers you're using for your current TV and movie-watching. If you're like many people, you listen through the speakers that came with the TV. Fortunately, TV manufacturers tend to be really good at video - unfortunately, audio is not really their specialty.

Many people consider these speakers to be "courtesy speakers" - that is, speakers that are included to allow you to set up and watch the TV without having to do a lot of work. But that doesn't make them good.

Lots of people have tried hooking their TV into their stereo, which usually results in far better sound than with just the TV speakers. We often hook up "surround sound" receivers and speakers - and the results are tremendous! Click here for more information on our home theater installations.

There are, of course, wide variances in the sound range of different types of speakers, so be sure the speakers you select will cover the entire range.

In the next few blogs, I'll talk about different aspects of speakers.

In the meantime, please visit us on the web at http://www.inspired-electronics.com/, or call us at 847.471.4420. We can answer your audio and video related questions, and help you get set up for the best home theater!