Wireless Speaker Systems - Installation Tips

Line Level Inputs

Multiroom Audio: A major potential difficulty may arise in a multiroom audio setup with wireless systems using the line-level signal.

Normally, there is only one such connection per source. This means that you will run into trouble if you want to hook up your audio source to both your AV receiver for home theater listening, and to one of these wireless speaker systems for a second-room audio installation.

The most straightforward solution is to use the headphone jack. However, this will most probably disconnect your main speakers in the home theater. The best alternative is to make use of a Y-splitter audio cable to split the audio signal from the main audio source in two.

Rear Channel Wireless Connection: Most wireless add-on speaker kits designed for use with rear speakers (normally labeled as wireless rear speaker kits), connect straight to the speaker output without problems. Again, the Rocketfish RF-WHTIB is a case in point.

However, if the wireless system you opted for needs a line level signal, then you cannot simply connect it direct to the rear speaker out on your AV receiver. Doing so is a sure way of blowing up the audio input stage on the transmitter unit of your wireless speaker kit as a result of the higher voltage levels present on the speaker outputs.

The best way forward is to make use of a speaker-to-line-level adapter. This is necessary as you need to match the voltage level found on your rear speaker output with the requirements on the wireless speaker input.

 

But do not just pick the first adapter you find. Try to match the power handling of the adapter with that on your rear speaker output. Choosing one that handles 200W when your surround delivers 50W would put you at risk of ending with too low a volume on your wireless rear speakers to match the rest of the audio channels.

A better solution would be to make use of an adapter with adjustable settings. Try to go for a fixed-type adapter such as the Audioplex SPKCNV Speaker to Line Level Converter when you have a volume setting on your wireless speaker system. In most cases, the presence of a volume setting should allow you to make up for any difference in the output level on your wireless connected speakers.

Suitable adjustable lineout converters include the Scosche Loc80 2-Channel Adjustable Lineout Converter - pictured here. Note that most adjustable speakers to line level adapters are often intended for use in car audio. However, these would still do a fine job in a home setup.

The main difference being that car audio generally deals with lower 4 to 2 ohm impedance speakers in view of the lower supply DC voltage present. Therefore, the power input handling capacity of a unit designed for car audio will have to be lowered accordingly to match the higher voltages found on home audio systems.

A cheaper option - depending on your basic electronics know-how, is to build one yourself. In its simplest form, this consists of four cheap resistors to form a double potential divider circuit (one per channel) to lower the speaker voltage to line level value. A good explanation of what is actually needed is also available at www.termpro.com.

Dealing with open circuit problems on your speaker output

Often, the transmitter end of a wireless speaker kit would present an input impedance of several thousand ohms to the connected amplifier. This is OK with a line-level connection. But when it comes to a connection over an amplifier speaker output stage, this represents an open circuit.

The problem is that some AV receivers/amplifiers come with open circuit protection on their speaker outputs as part of a mechanism designed to safeguard the amplifier output stage. This means that such systems would block the output if they do not sense any speaker load. Others would not tolerate an open circuit despite that they do not block the output with the result that you may end experiencing severe humming noise on your wireless speakers.

While these problems may render your wireless kit useless, yet these issues should not prove to be showstoppers.

The solution is rather simple: Connect a dummy load in the form of a simple resistor across each of the speaker outputs. You need to experiment to determine the best load that would work with your AV receiver. The issue is to find the maximum value for this dummy resistor that would work in your case since the lower value you choose for this resistor, the more heat it will dissipate. Often, a 100 ohm resistor connected across each of the speaker outputs on your AV receiver will do the trick.

Determining the power rating of this 100 ohm resistor is a bit more complicated. A 4-Watt resistor rating would suffice if your AV receiver delivers 50W rms into 8 ohm speakers; a 2-Watt power rating is required if the same 50W are delivered over a 4 ohm speaker load. Note however that as you increase the power, this dummy resistor load will start to get hot to the touch. So be careful how you position it; in particular, be extra careful to avoid possible damage to other connecting cables.

7.1 Surround Sound Hook-Up

We are often asked if it is possible to use two wireless rear speaker units to connect the rear and back speakers in a 7.1 surround system setup.

There is no reason why one cannot use two such kits for the purpose. However, there is one important issue which needs to take into account here:

Select wireless kits that will allow you to use multiple systems in the same room without interfering with each other. This means the selected wireless rear speakers system should have the sender/receiver pair uniquely matched at the factory; this is the case with the Rocketfish system. Alternatively, go for a system that makes it possible for the user to select different communication channels for different units when used in a common environment.

Having two wireless systems gives you the added bonus that you will have greater flexibility when wiring the speakers between the wireless receiver units at the back of the room. This in view that most wireless rear speaker systems come with a single receiver unit to drive the two rear speakers via a physical wire connection. The use of a single receiver unit is mostly a cost issue. However, with two such receiver units, you can wire your wireless speakers in a way that will allow you to eliminate the need of wires crossing the room from one side to the other and the receiver unit. This would prove to be a great solution if for example, there is a door between the two rear/back speaker placements.

Basically, all you have to do is to wire the left rear surround and left back speakers through one wireless system and the right rear surround and right back speaker through the second wireless rear speaker system.

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