A quick look at the hottest cordless speaker kits.

| Monday, August 15, 2011
By Gunter Fellbaum


A new trend is the appearance of an increasing number of home theater systems with cordless speakers or a separate wireless surround sound kit. As multi-channel audio still is a fairly new phenomenon, older homes are not prewired for surround sound, especially with the most recent trend of 7.1 surround systems. As such a wireless option appears to seem like the logical choice. But are these wireless surround sound kits reliable enough for real-world applications and do they get rid of the dreaded cable clutter?

Looking at available wireless surround sound kits, you will notice that most of them, such as the products from Rocketfish or LG will connect two speakers to a wireless receiver unit. As a result, such systems, while eliminating the speaker cable from the front of the room to the rear, do not really eliminate speaker cable but only reduce it. As such products with separate wireless receivers for each speakers, such as the product from Amphony, offer a much cleaner solution since each receiver can be attached directly to the speaker of choice.

Will the wireless have any effect on performance? Audio quality is a main concern. In picking a wireless system, one should choose a system where (a) the transmission itself does not pick up any noise or degradation in order to maintain the audio quality and (b) the wireless amplifier itself should be a high-quality amplifier with minimal distortion. Also, the size of the wireless speaker amplifier is a consideration as the receiver should be invisible.

In a surround sound application, such as a home theater setting, the audio from each speaker naturally should be in sync with the video and also with the audio of the other speakers. Some wireless surround sound kits, such as the product from Rocketfish, will introduce a significant delay to the signal. Therefore when choosing a wireless surround sound kit, it is important to look closely at how much latency the wireless unit will introduce. The Amphony product adds a little less than 1 ms delay which should be sufficiently low for pretty much any application.

One of the main issues with wireless devices of any sort is interference from other devices. As more and more consumer devices go wireless, the available frequency space becomes more and more limited. Especially the 900 MHz and 2.4 GHz bands are exceptionally crowded, due to WiFi hot spots, cell phones with Bluetooth etc. Picking a system that avoids these frequency bands may be the logical choice, such as systems working at 5.8 GHz.

In addition to connecting rear speakers in a home theater setting, another useful application of a wireless surround sound kit is setting up speakers wirelessly in another room in cases where installing speaker wire between different rooms presents a challenge or for setting up speakers in your backyard within minutes. The applications are endless.




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Hints To Help You When Shopping For The Perfect Stereo Amplifier

| Saturday, August 13, 2011
By Gunter Fellbaum


Choosing the perfect audio amplifier can be overwhelming given the large number of different types and technologies. I will help you understand some of the basic amplifier jargon terms. This knowledge will help you choose the perfect amplifier.

Even though some audio sources have already a built-in amplifier, a separate amplifier gives you more flexibility for picking the model that best complements your speakers. There are some mini amplifier models available. These models are small enough to hide virtually anywhere.

When picking an amplifier, your first consideration probably is the amplifier output wattage. You will need a high wattage if you are driving speakers with a low sensitivity (expressed in dB/W), for driving speakers in large rooms or for outdoor speakers. Don't overdrive your speakers though since this can irreparably damage your speakers.

However, amplifier wattage is not everything. Good sound quality is probably more important than raw power. A 20 to 50 Watt amp should be sufficient for most real-world applications.

Amplifier output power is given as Watts rms (continuous) and Watts peak. The rms or continuous value tells you how much power the amplifier can deliver continuously while the peak power figure tells the maximum wattage that the amplifier can deliver for short periods of time. Most people will look at the rms power value when selecting an amplifier. However, music signals are anything but continuous. Therefore picking an amp that has sufficient peak power handling is just as important.

Audio quality is just as important as having enough audio power and therefore you should also look at figures such as total harmonic distortion or THD. No amplifier is perfect. There will be some amount of signal distortion which is caused by the amplifier. The amount of distortion is expressed in percent or dB. A smaller distortion number means a lower distortion of the audio signal by the amplifier. The amount of distortion will be less than 0.05% for a high-quality amplifier. Consumer type amplifiers have higher distortion figures. Typical figures are up to 10% depending on the output power.

Another specification is called signal-to-noise ratio. This number specifies how much undesired components such as hum and noise the amplifier will add to the audio signal. Consumer-grade amps will have a signal-to-noise ratio (SNR) of at least 80 dB. Higher-end amps will have an SNR of 100 dB or more. Audiophile amps will have an SNR of close to 120 dB.

There are several amplifier technologies available. Today's amplifiers are mostly Class-D amplifiers. Class-D amplifiers have a high power efficiency and waste little energy as heat. High power efficiency has led to the development of very small amplifiers. Some of these latest mini amplifiers are no bigger than a deck of cards. Class-D type amplifiers often have higher distortion and a lower signal-to-noise ratio than Class-A or Class-AB amplifiers. Some latest digital amplifier models, however, come very close to the audio quality of analog amps. Make certain that the amp has low distortion and a high SNR if you pick a Class-D amp.




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Ideas for getting music for your iPod.

| Sunday, August 7, 2011
By Brian Fuller


AOL Radio and Yahoo! Launchcast listeners are now building their iPod music collection for free thanks to iGetMusic, a new recording tool.

Traditionally building a free iPod music collection has been a tedious task. The most common method would be ripping tracks from a CD and then convert them to MP3s. As a final step, title and artist information would be added by hand or by using a download service.

This traditional approach has changed more recently as more and more users are downloading tracks from online retailers such as iTunes or P2P networks. Aside from P2P downloads not always being legal, downloading individual tracks takes a significant amount of time. Having to manually enter track information, searching and then downloading individual tracks for hundreds or even thousand tracks will take a large amount of time. In addition, the record industry, plagued by ever falling sales, has flooded P2P networks with fakes in an attempt to slow illegal downloads.

Another method which does not require downloads is using internet radio rippers, such as StreamRipper, which will record tracks from online radio broadcasters. This method would appear to save a lot of time compared to downloads. However, the biggest problem with internet radio rippers is the cross-fading between tracks which makes creating cleanly cut tracks impossible for rippers. When splitting tracks, rippers rely on the title information which is broadcast along with the songs to determine where to split tracks. Online radio broadcasters, however, are deliberately varying the time when the title information changes in relation to the beginning of each track. As a result, a user will have to manually edit each track in order to get properly cut tracks. This will take a significant amount of time for a larger number of tracks.

Recently Amphony, a company that makes audio and software products has released iGetMusic which is an application that will extract music from free online radio services such as AOL Radio and Yahoo! Launchcast. The program will run in the background and save each track that is broadcast by these online radio services into a directory of choice. These songs are automatically tagged with title, artist, album and genre information which will make organizing them later on in iTunes or other music organizer software a snap. Also, this allows easy playback of songs from a particular album or artist on an iPod. All the tracks ripped by iGetMusic are full-length, i.e. don't miss anything at the beginning or end which is a big plus compared to traditional internet radio rippers.

When using iGetMusic, a user would launch the application and then open up one or several browser tabs at the same time and tune into any channel of the supported radio services such as AOL Radio. iGetMusic is actually able to grab songs from several browsers running in parallel. In practice this means that the software can rip several thousand tracks in a single day. The recording speed is in practice only limited by the speed of the internet connection and the computer. iGetMusic will check which songs already exist in the music collection and not record duplicate of songs.

As an added bonus, iGetMusic has a feature that automatically saves the album cover of each song which is pleasing to the eye when playing back songs on a computer with a media player such as Winamp or on an iPod. A user can set up a blacklist which contains names of artists that iGetMusic should not record.

Since iGetMusic is able to produce a large number of tracks, storage capacity of the iPod becomes an important consideration. An iPod nano offers up to 16 GBytes of memory and can hold up to 4000 MP3s depending on the sound quality or bit rate. iGetMusic will produce the songs in the AAC Plus (M4A) format which in comparison to MP3 cuts the size of the tracks in half without sacrificing sound quality. Thus an iPod nano can store up to 8000 tracks created by iGetMusic depending whether or not album covers are stored as well. Since some older MP3 players do not yet offer AAC Plus support, iGetMusic recommend using a free 3rd party batch converter to convert the tracks to MP3.




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