FAO Gumpy... aka Tim Wilky :)

Following your post in the Bluray thread (wireless surround sound system wanted), there's only a handful I know of - and I haven't used any of them, so can't give them any sort of recommendation.

First, the obvious.

You want speakers that output sound, without wires. It's technically impossible.

With a traditional surround sound system, there's wires with minimal voltage/current going to each speaker. In a wireless system, you need to power the receiver (whatever technology that be).

So if you want wireless audio transfer, you need some means of powering the speakers. Power cables are generally thicker than audio cables, and I'm guessing you don't want to be swapping batteries infinately.

Now the less obvious.

There's several wireless technologies in use for the job at the moment. First being Bluetooth (because it's a "fad" IMO, so it was "cool" to use Bluetooth for surround sound). Bluetooth has a transfer throuhput (from a practicality viewpoint) of 433kbps. Dolby Digital requires 400kbps, and full DTS requires 448kbps for a full 5.1 surround stream. That's Bluetooth out the window then (don't buy any surround sound system using it, you won't get surround sound out of it!).

As for the others, there's naturally things like IR, but again, I'd rule these out for reasons of bandwidth (unless you opted for an MIR or FIR setup - both of which take more power & will cost more to run) & physical line of sight limitations.

Then there's Wifi-ish ranges, 2.4Ghz specifically is what most manufacturers seem to use. Obviously you're already aware of possible interference by other Wifi networks in the area sharing the same channel.

Another thing not often considered, is the digial amplification of the received sound by the 'satellite' speakers. This is done by Class-D amplification in 99% of cases, which can be quite a lossy way to amplify the source (dependant on hardware).

Given all the above considerations, especially the fact that you will still need a power cable to the speakers, are you really still wanting a wireless surround sound setup? Especially when a wired system will generally be cheaper, and better quality than it's wireless brethren.

If you are, I can point you to a few manufacturers etc. I just didn't want to derail the other thread with all this opinion.

I have the Logitech Z550 5.1 system (only £200 too). The two rear speakers are wireless (as in they do not need to connect to the reciever) but they are both mains powered and have plugs on each speaker. So, it means I don't have to run a cable from the receiver (which is at the front of my setup) to the rear speakers, all I need to worry about are two plugs which is easy. I think this is meant as wireless until we can transmite large volumes of electricty over the air (possible even today) without frying our own nadgers (very possible today).

Originally Posted by Baph

Then there's Wifi-ish ranges, 2.4Ghz specifically is what most manufacturers seem to use. Obviously you're already aware of possible interference by other Wifi networks in the area sharing the same channel.

From memory they use 2.4Ghz as it has oodles of channels that it cycles thousands of times per second. If it detects that a channel is being used by another device it will use another one. I only know this as my R/C helicopter is 2.4ghz and the old one's used to be 35Mhz, see below for a long winded but more accurate description, it's geared towards copters but the theory is the same:

WHAT IS 2.4GHZ TECHNOLOGY

Operating at 2.4GHz puts the radio control out of the frequency range of any 'noise' caused by the other electronic components - such as the motor, speed controller and any metal to metal noise - eliminating interference and glitching that can affect a 35mhz system. Obviously, the last thing you need when piloting an RC helicopter is anything that might cause loss of control or a crash (you may not be aware if your neighbour is also flying on the same frequency as you in his back garden, for example). The built-in security of the 2.4G system allows you to maintain radio control at all times, ensuring your safety and that of others around you. Instead of transmitting on one channel at a time, both the transmitter and receiver are constantly hopping from channel to channel - at over 1000 times a second! When you initialy 'pair' your transmitter to your receiver, they initiate the synchronised sequence of channel hopping.With 2.4GHz effectively 40 channels are available and the sets automatically set themselves to an unused frequency when switched on. Operation is constantly self monitored and the set will move to an unused frequency if any interference is detected. Because 2.4G RC systems work on higher frequency short wave length, the transmitter antenna is only about 15cm long and flexible - avoiding bends and breakages that can occur with traditional 35Mhz telescopic aerials! The receiver antenna is much shorter too - allowing for much neater installation of the radio gear in the helicopter.
ADVANTAGES OF 2.4GHz

(1).Traditional 35MHz remote controls require a transmitter with 750mW transmitting power consumption but 2.4G transmitter only needs 4mW power consumption so batteries last much longer.
(2)2.4GHz frequency band completely eliminates frequency interfering when flying so no more potential crashed due to radio glitches or interference.
(3)2.4GHz remote control systems automatically bind frequency using a microprocessor and constantly change so no more need for crystals and more importantly no chance of someone switchiing on there transmitter with the same crystal as you, causing your heli to crash.
(4).Dual transmission gives better response and control of you heli and reduces servo quiver.
(5).2.4Ghz System frequency wave range is 1/4 of the usual used frequency wave range so the transmitter antenna is just 14.5cm in length making flying indoors much easier.

Originally Posted by DanAbnormal

From memory they use 2.4Ghz as it has oodles of channels that it cycles thousands of times per second. If it detects that a channel is being used by another device it will use another one. I only know this as my R/C helicopter is 2.4ghz and the old one's used to be 35Mhz, see below for a long winded but more accurate description, it's geared towards copters but the theory is the same:

Assumption being the mother of all messes (U-rated version ).

Please don't assume that because a helicopter can auto-negotiate ISM band channels (those being 2.4Ghz) that anything else will.

Prime example of this is WiFi routers, I can't think of one off the top of my head that does auto-negotiate.

You are right in that some on the market may, but I suspect the vast majority wont.

I should also point out that the terminology "channel" was only introduced for the 80x.xx IEEE specifications, and as such, only really applies to WiFi. Other devices communicating on "channels" may well do the same, but there's no requirement for the channels to be 22mhz wide (spaced by 5mhz), which is the case with 802.11. There are also only 12 channels in that specification; 11 of which capable of being used by most WiFi routers. Local law prohibits the use of some IEEE specified channels as well.


Getting back to the subject a little, should the surround sound system in hypothetical use NOT perform auto-negotiating for it's specific frequency, you run the risk of interference from any of the following (ignoring the aforementionned WiFi):

• Cordless house phones.
• Car alarms & associated key fobs.
• Microwaves.
• Wireless CCTV systems.

Now imagine if all those DO perform auto-negotiating. Whilst your surround sound system re-negotiates, you experience very poor sound (if at all), and this is the reason some manufacturers don't bother with it.

Originally Posted by Baph

Assumption being the mother of all messes (U-rated version ).

Please don't assume that because a helicopter can auto-negotiate ISM band channels (those being 2.4Ghz) that anything else will.

Hmm, I knew there would be someone with some techy-knowledge to spoil my seemingly intellectual reply. Curse technology!

[timwilky]

You called

By wireless I was meaning no physical connection between whatever the transmitting unit was and the speaker. Ideally mains powered.

So the possible technologies are indeed 2.4Ghz spectrum including bluetooth etc. or infrared. I had thought that it might also be possible to distribute the audio signal on the ring main. and that it would be really clever to simply plug in a speaker and pick up both power and signal through the 13A 3 pin plug.

I have been looking for some time now and everything seems gutless and tinny. I do not have the option of attacking the wifes newly decorated room to install wall plates and wiring. She had already gone beserk because her choice of new sockets required me to sink the electrical back boxes deeper. Her choice of decorator lasy sod simply cut round the existing sockets instead of removing the faceplates and cutting inside the box and therefore the nice flat sockets now show up the decorators edges etc.