Wednesday, October 14, 2009
Monday, October 12, 2009
Thursday, October 8, 2009
Purchasing separate components for your whole house audio system may save you money and provide greater flexibility, but there are some basic concepts and terms you need to understand before buying. Impedance is one of the most important terms to understand when configuring your needs for a whole house audio system; and will ultimately lead to better system performance and less installation frustration. Trying to understand impedance can be an intimidating process, but it was explained to me using a very simple analogy and I will do the same for you. First things first, the impedance value of a loudspeaker is more commonly expressed in Ohms. Most home speakers are 8 Ohm, but do not work under this assumption, ask the dealer or look on the box [All of Theater-Solutions are 8 Ohm].
Think of your water pipes and pump at home. The pipe diameter represents the impedance of your loudspeaker; the water flowing through it is power, and the water pump is the amplifier (or receiver). Now, if you have a pipe large in diameter, it allows a large amount of water to flow through it, but requires the pump to work extremely hard to keep up the pressure, this would be considered a “low impedance” situation, the large pipe does not lighten or impede the large flow of water. Likewise, if the pipe were small in diameter, it would allow less water to flow, we will call that “high impedance”, because the smallness of the pipe is impeding or slowing the flow of water, or electricity. Let’s recap: Low impedance equals large flow: High impedance equals slow or low flow.
Using this same analogy let’s consider voltage and current; voltage (water pressure) and current (water flow) together create power. Now, if your pipes at home were suddenly to widen in diameter the pump would still pump the same or voltage doesn’t change, but the flow (current) would; and therefore you would receive less water flow. The pump would have to provide more power to keep up the flow, therefore lower impedance (large pipes) requires a stronger amplifier (water pump). Now reverse that theory for high impedance, and remember if the pipe is small it is restricting the flow or impeding it and pressure can build up and flow becomes more difficult. Impedance is not difficult to define, it’s more defining the actual application of impedance that is challenging. So before we proceed, let’s review what we know from our previous analogy.
- Low Impedance equals large or free flow of power, but requires the amp to work harder to drive enough current to maintain flow. This added demand can be too much for an amplifier and cause it to over heat and shut down.·
- High Impedance equals slow or low flow of power, and can cause restricted flow of current. The level of current influences the volume at which the speaker plays; low current equals low volume.
The optimal range for most amplifiers, receivers, and speakers to work between is 4 to 8 Ohm. This is generally easy to maintain if you are just directly hooking up speakers to a receiver or amp, but when considering multiple rooms and speakers it quickly becomes increasingly difficult to identify the overall resistance. This is important because that will identify your receiver/amplifier needs. As you wire speakers either in series or parallel, or a combination of both the resistance either increases or decreases, therefore changing the loudspeakers Ohm. In the end multiple speakers should not be hooked up directly to a standard audio amplifier. The best solution is to use either an impedance matching speaker selector box with the protection enabled, or impedance matching in wall volume controls; "impedance matching" is underlined because not all volume controls are impedance matching. Using this speaker selector boxes and volume controls it is possible to wire your entire house using a single receiver/amp as long as your receiver/amp has the needed power.
Tuesday, October 6, 2009
2. Center-Channel Speaker: The center-channel is a crucial piece of a proper home theater system, and is commonly completely over-looked. Center channel speakers are specifically designed to reproduce the vocals, and are responsible for more than 50% of the soundtrack, including almost all of the dialogue. It can be difficult to properly place the center channel because flat screens are so much larger. Again, ideally a center channel will go in the wall above or below the screen, however if this is not possible, use an external center channel on a shelf. It is important that it is in the center of the two front speakers and not off to the side, as this will disrupt your surround sound experience. Do not try to use the television as the center, it makes a very poor substitute.
3. Surround Sound Speakers: produce atmospheric, ambient sounds such as knocking on the door, thunder storms, and the rustling of leaves. They also work with your front speakers to deliver fantastic directional effects, like a helicopter flying by, or a bullet whizzing by. Ideally, your surround speakers should have the same performance capability as your front speakers, however homes being built with open floor plans, it’s not always that easy. If you are unable to put in rear in-wall speakers or mountable speakers, consider the newly released in-ceiling angled speakers. They allow the sound to be pointed directionally at the listening area, while still being unobtrusive. In modern homes, the thought is that speakers should be heard not seen. This mantra is different from the 70’s and 80’s where the larger the speakers and the system the cooler you were. Well, speaker technology has come a long ways, and you no longer need giant speakers to boast an impressive sound system. Because surround speakers produce, “directional sound” the proper placement of your surround speakers will heavily impact your over-all theater experience.
4. The Subwoofer: The subwoofer is available in both powered and passive – the advantage of a passive subwoofer, is the clean modern design, installed out of sight in the wall. It looks great, and for general music this is an acceptable option. You will need to use one of your additional channel outs or share one of your front speaker connections to power the subwoofer.
A powered subwoofer includes the amplifier in the enclosure, and connects easily to the “sub out” connection in the rear of your receiver. A subwoofer produces non-directional sound, so you may place it anywhere in the room, I recommend checking several locations to find the best sounding location before running your wire, and bare in mind these units require an electrical outlet. If I sound a bit partial, it’s because I am. Once you have experienced a home surround system with a powered subwoofer, you will never want to watch television or listen to music with out one. If you have an older model of receiver that does not have a subwoofer out, many subwoofers offer speaker-level signals connections from the amp and extract the bass sounds.
5. Frequency Response, Db, & Cross-overs: Here are three words that are generally foreign to the average consumer, but three important considerations when making a surround sound purchase. When purchasing a speaker consider the seller and their warranty, beyond that; compare these three characteristics of a speaker. First look for these ratings under specifications, you want a frequency response of 20 Hz to 20 Khz, a sensitivity rating of 90 db or better, and the speaker should have at least a 2nd order crossover.
My family and I rarely go out to the movies, because it simply doesn’t compare to the convenience of home. I hope this article will help you to feel more prepared when embarking on purchasing your first surround sound system.