Home Audio and Video Technology


Brand: Audio Reflex
Introduction to Home Theaters
Speaker Drivers
Crossovers - What are they?
What is the difference between Amplifiers and Rece...
High Definition Video Formats
Distortion: Clipping
Blu Ray Media Controversy

Wednesday, October 18, 2006

Brand: Audio Reflex

I have recently come across an amplifer and a pre-amplifier of the brand "audio reflex". This was apparently purchased late 70's, early 80's and it can produce some really high quality powerful audio, even after 35 or so years.

The following are the model names of the amp and pre-amp:
Pre-amp: ARP 1100
Amp: ARM 1200

I cannot seem to find websites with solid material about the brand and its related products. If you have Audio Reflex equiptment or know a bit about it, please comment. Im looking foreward to finding out more.

Paul Macleod

Tuesday, April 18, 2006

Introduction to Home Theaters

This is a general introductory article to explain to you what components are needed for your home theater, and how to set it up. If you read this article, you should gain a greater knowledge on how to set up a home theater system in your home. Home theaters often look quite complicated to the non-technically minded, but they are really not that complex. Let me start with a general outline of what a home theater actually is.

What is a home theater?
Having a home theater is trying to make an environment in a particular room of your house that closely depicts that of a movie theater. This is done using technology in both the audio and visual electronics sector.

You can usually buy a whole home theater set, consisting of everything that you need. However, these are not usually the as good as if you were to buy the separate components. If you want to buy everything separately and put it together yourself, then you are reading the right article.

How much money will this cost me?
If you wish to have a substantial home theater, you will need to fork out a considerable amount of money. First, you will need a source, such as a DVD player or a satellite. You will the need a several speakers, a home theater receiver/amplifier and, preferably, a reasonably large television.

Here is a general minimum for the components in a home theater. (USD)
Receiver: $100
Six Speakers: $200
Flat Screen Television: $800
DVD Player $50

Prices vary from store to store, country to country. But you generally need a minimum of $1K US to buy all the components of a home theater. This is if you do not have a TV or any other components reserved for this already. Keep in mind that almost any CRT television today can be used within a home theater, so it is not necessary to be forking out large sums of money for a large flat screen if you’re comfortable with the one you have.

The receiver is a big part of the home theater. Most people think that good speakers make up a good sound system. But it is the combination or speakers and a receiver that produces great sound. There is no point in getting top of the range 200Watt speakers if you only have an 80Watt receiver to power them. I cannot give you specific information about every receiver and speaker system out. When purchasing your speakers and amplifier, you should ask a trusted salesperson for some guidance. If you have any doubts or queries, no matter how stupid you think they are, don’t hesitate to leave a comment.

The speakers you purchase generally make up a 5.1 system, 5 speakers and a subwoofer. The 5 speakers consist of a center speaker, front left, front right, back left and back right. If this is not ample, many people go to a 6.1 or a 7.1 system by adding a speaker at the back or two at the sides. The center speaker is placed as close as possible to the television. The subwoofer, generally, can be placed in any part of the room. After purchasing these speakers, you should buy copper wire long enough to connect all of your speakers to your receiver. Then, simply connect all the speakers to the receiver, along with the DVD player in one of the inputs.

Now, let’s talk about that dream television. Is there any way to get a huge television for a cheap price? Well... no. Generally, the more money you spend, the bigger the screen. Plasma screens are usually a bit cheaper and LCD, however, one of their downsides is screen burn. When you have the same image on a part of the screen for a long period of time it can burn the image to a plasma television. This is really not going to come into play unless you use your plasma to play video games or as a computer screen.

I hope you have learnt a lot about this article. If you have any questions/queries, please post a comment. If it is something you don’t want to be on a website, just email me or post anonymously. Thanks.

Speaker Drivers

This is just a short post to explain to you exactly what a speaker driver is. Enjoy.

The speaker driver, which is usually the speaker itself, is an integral part of a home theater system. The driver is the actual ‘thing’ that converts the meaningless electrical signals into actual sound and music. It does not refer to the speaker box/enclosure itself, but the speakers inside the enclosure. To put it in simple terms, when you look at a speaker itself and you see these circular objects embedded in the speaker. These are drivers.

Drivers range from tweeters (high frequency/pitch), midrange and low range (low frequency/pitch). The tweeters are usually the small cones and the low range woofers are usually the large heavier cones. If you know your physics, this is very logical (F=ma). On the higher range speakers, tweeters, you need the cone to vibrate more quickly. In order to do this, you need a very quick velocity change of the cone, in other words, acceleration. To gain a higher acceleration with less force, you obviously need a smaller mass, hence, a smaller cone. This is the general rule of thumb when manufactures build drivers for certain frequencies. Good speakers usually have a low range woofer, a high range tweeter and sometimes a midrange driver in one speaker box. To be able to send certain frequencies to their designated driver, speakers often use a crossover.
Read more about crossovers.

Crossovers - What are they?

A crossover breaks an electrical audio signal in to separate frequencies. Its purpose is to ensure that each speaker driver receives its desired frequency. It usually splits it up into high, mid and low frequencies, assigning low range speakers such as woofers and subwoofers low frequencies and vice versa for high frequencies.

Crossovers allow speaker systems to produce awesome high fidelity sound. It gives manufactures the flexibility of making high-range, mid-range and low-range drivers. Having three types of drivers designed for certain frequencies sounds much better than one trying to handle everything. This also allows consumers and manufactures to tweak specific speaker driver components. For example, you can have more woofers (low-range) for a more powerful bass feel to your sound, or more high-range for better treble.

Crossovers usually do not need a power source in order to operate. These are called passive crossovers. These crossovers often act within speaker enclosure, where no power source is present. They are often superior because the speaker manufacturer constructs them in a way that gets the best out of their speaker drivers.

Active crossovers pick up certain frequency ranges before they go into the amplifier. These are usually used within pre-amplifiers or receivers. A great advantage of them is that you can actually change the frequency that is sent. This is often found in devices such as six channel amplifiers, where the high frequency is sent to the center and the surround speakers and the low frequency is sent the subwoofer. A bad thing about them is that they are often more expensive than crossovers within speakers. Although you can change the actual frequency settings. Preset frequencies within speakers often work better because they are made by the manufacturer who knows the specific needs of the speakers.

What is the difference between Amplifiers and Receivers?

Have you ever gone looking for an amplifier for your home theater system, only to find receivers at your local electronics store? Consumers often get confused between the two because some companies call it one thing, and some call it the other when they actually are two different, but similar things.

Basically, an a receiver is an amplifier, with added features.

An amplifier is simply a box that takes a signal in, amplifies it and sends the signal out. There is no option to change the source, volume, equalizer or anything else. A receiver, however, does all that an amplifier does, but it can have multiple inputs and outputs and an interface to manage it all. Many receivers also have radio tuners built into them.

You may be wondering, how do you input all of your hi-fi components into an amplifier? Well, to do this, you will need a pre-amplifier. This does all that a receiver does, but instead of amplifying the signal for the speakers, it simply forwards the signal on to the amplifier. Most people purchase a receiver over and amp/pre-amp because it is much cheaper to buy one unit than two. It also seems much simpler to do it this way to your average consumer. Basically, people view having one box, alot simpler than having 2 boxes. Asside from the price, the amp/pre-amp configuration usually is ideal if you are after the best sound, and are willing to fork out the price.

The general name for a receiver is an amplifier. Often when receivers are on display in shops and online stores, they are called amplifiers. Do not get confused when a receiver is being sold as an amplifier. You can always tell which one is which because a receiver has an interface (‘buttons and knobs’) and an amplifier doesn’t. Also, a the back of a receiver is usually full of input and output connections. Hope this helps you sort out this grey area.

Monday, April 17, 2006

High Definition Video Formats

If you are confused as to what the difference between 720p, 1080i etc means, you have come to the right place. Here, I will explain to you what these formats mean, and some other information which you might find useful.

Firstly, I will explain to you that the numbers mean. We will go onto the whole 'i' and 'p' thing later. The two common types of hdtv formats in place today are 720p and 1080i. These numbers may seem meaningless to you right now, and that is understandable, however the concept is not really hard to grasp. You may know that a digital video is basically comprised of a large matrix of pixels. The amount of pixels you have is often refered to as a resolution and is measured as the # of pixels across x # of pixels high. Well... the number of pixels vertically on a screen is this number. Say you had a high definition video streaming through with a resolution of 1280x720. Then this would be either 720p or 720i. There is also a larger resolution out which measures 1920x1080. This is where the 1080 comes from. There are only a selected few screens on the market today that can display this kind of image and these are very expensive.

All hd is in a 16:9 aspect ratio. This means that the picture is 16 pixels wide for every 9 pixels it is high. This works out if you make some calculations. If you divide 1080 by 9 and then times by 16, you should get 1920, which is the horizontal resolution of the 1080 picture. With the 720 resolution, you should get 1280 in the horizontal direction.

There are who types of signals. Interlaced and progressive. Now, you probably already know that the pixels refresh from left to right, line by line. This is what progressive is. Every line is refreshed, one after the other for every frame. With interlaced, every second line is scanned. For example, every even numbered row is scanned in the first refresh and then every odd numbered row. So, if the refresh rate is 60hz with interlaced, then technically the whole screen is refreshed only 30 times every second. Wheras with progressive, its 60 times per second. Interlaced was introduced because of limitations on the amount of data that was able to be sent through. A 1920x1080 resolution is obviously a very large amount of pixels to be refreshing 60 times every second. This is why, for the time being, it is only available as interlaced. Some people preffer 1080i and others prefer 720p. It seems impossible that you can notice interlaced scanning when the usual eye can only distinguish at 12hz, however you can notice some difference. In scenes with a lot of movement, you can sometimes see a flicker, and for some people, this can get annoying. In general, the progressive scan is alot more smoother to watch than interlaced, but different people have different opinions.

If you have had experience with both types of hd, please post a comment telling us your thoughts on what is best. Also, if you have any other questions or queries about what is going on in this article, please do not hesitate to post a comment with your question. Thanks for reading.

Distortion: Clipping

Clipping is a type of distortion that occurs in an amplifier when you have the volume above the normal level. Clipping can result in damage to the tweeters in your speakers due to the excess in high frequency sound. For instance, if an amplifiers rated power is 100watts and you run it at, or close to full power, this could result in the amplifier clipping the signals. Many of the more expensive, high end amplifiers have a colume range that is actually less than the actual range of the amplifier, so you cannot actaully turn the volume up to the point where is clips.

Let me explain further, what clipping actually is in terms of wave notion of AC power. It is the amplifier is extensively increasing the voltage of the electrical signal. The top and the bottom of the sin wave generated by the AC output is cut off (clipped) which introduces additional frequency components in the signal, thus, increasing the load on the high range components of your speakers. You can actually damage speakers that have a higher power rating than the amplifier due to the amplifier clipping.

Here is a good image of a sin wave that has been clipped courtesy of Wikipeda.

Sunday, April 16, 2006

Blu Ray Media Controversy

There has been much controversy over what will be the next standard in high definition media. It seems Blu-ray technology with a capacity of 25gB may be succeeding over hd-dvd with a capacity of 15gB. It is most likely to be injected into the gaming, data and video marked in 2006.

The disc itself offers high definition quality that is far beyond anything out today. It takes advantage of the large 25gig size to store video with resolutions of up to 1920x1080 at a bandwidth of 54 Mb/s. To put this into perspective, a dvd is around 6Mb/s with a resolution of 720x480. Also, due to the large size, no compression algorithms are needed. On top of this, there are plans for manufacturers to release dual and quad layered discs (holding 2 and 4 times the amount of space respectively).

However, it does have its downside. Along with it, this new media requires movies and video to be reproduced. It demands that people buy a costly blu-ray player after recently changing to a dvd player. The question remains, will all of this change be worth it? Should Blu-ray be used as the new standard? Is there really a need to bring out a new format in digital video media when we already have dvd's? Please tell us your thoughts on the topic.