Technology Futures

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Wireless Surround Sound: Kudos and Caveats

Speaker wire costs about $.15/foot for 16 gauge, $.20 for 14 gauge and $.25/ft for 12 gauge.  These gauges will, respectively, handle 20′, 35′ and 100′ respectively into an 8 ohm load, and half that distance for a 4-ohm load.  So, if you have two 8-ohm surround speakers located 30 feet from your receiver, the wire will cost about $12.00.  Further, with this conventional wired setup, there will not be any discernible delay between the sound coming out of the front and rear speakers.  They will be in sync.  By the way, speaker wire carries very low frequencies – less than 20kHz – and spending a lot for brand name cable is a waste of money.

Problem:  You are not able to run wires through the ceilings or walls, and your significant other won’t allow you to lay the wires on the floor where grandpa can trip on them.  A solution:  Use a wireless link to connect the rear speakers to your surround sound receiver.  However, you need to consider the cost.  A wireless connection can add $100 -$500 to the cost of your 5.1 system, and twice that if you have a 7.1 system.  If your speakers cost $1000 apiece, the incremental cost of wireless may seem reasonable.  If your speakers cost $100 each, the cost of adding wireless might seem exorbitant.

Be advised, I am not writing here about inexpensive bluetooth wireless speaker connections designed for iPods and the like.  I’m talking about achieving CD-quality sound in a quality home entertainment system with true surround sound.

The technology used in all the commercially available wireless systems for home use relies on using either the 2.4 or 5.8 GHz transmission bands, the same used by other household appliances including microwave ovens, wireless telephones and wifi network routers.  Thus, these systems may be subject to electrical interference resulting in static and signal dropout.  The better systems claim to have resolved that problem by providing multiple transmission channels.  The idea is that the system will find a channel that is not being used by any other appliance.  In general, the success of this scheme is a function of price.  The more expensive the system, the better job it does of avoiding collisions and the clearer the sound will be.

Another problem is that the signal to the rear speakers will be delayed by some 15-20 milliseconds.  Most people won’t notice, but sensitivee audiophiles might find that annoying.  The best way to handle that is to use a receiver that allows the user to adjust the delay time to each speaker.  Fortunately, many moderately-priced receivers today have this capability.

One company, Avnera (Portland, OR), has designed a chipset for the purpose it calls AudioMagic.  By reducing the component content to a couple of chips, the cost of wireless is drastically reduced, and we can expect to see the prices of these systems drop considerably.  The Avnera chips are used in the Rocketfish system sold by Best Buy, one of the cheapest on the market.

The following table summarizes most of the available wireless speaker links on the North American market.  Data comes from the manufacturers’ websites and may or may not be accurate.  Prices are average online prices as of May 2012.  Careful shopping will likely turn up lower prices than those shown.  All of the models listed can be found by website search.  I could not figure out how to include the links in the table – a WordPress issue I suspect.

Notice that Samsung and Sony offer systems wherein the transmitter is contained on a card that plugs into their receivers.  The cards are much less expensive than separate transmitters.  I believe that chipsets like Avnera’s AudioMagic will soon be built-into receivers, reducing the cost of the transmitter function to very little.  Receivers, however, will still need to be expensive, because of the amplifiers they must contain.  Some speakers can be purchased with built-in amplifiers, but they tend to be aimed at the low-end of the market.  If you want to choose your own rear speakers, you will need to buy separate receivers.


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