ION Audio's Wireless Stereo-Link is a powerful tool in constructing the perfect multi-speaker setup for your home. However, there are some important limitations to consider when conceptualizing your rig. One of these regards the use of microphones with units that are linked wirelessly, and this guide serves to explain the reason behind that limitation and offer useful workarounds.


Digital Signal vs Analog Signal

The reason that microphone signal cannot be transmitted via Stereo Link is that microphone signal is a purely analog waveform, while Bluetooth signal is digital signal comprised of bits. The below image illustrates this difference concisely.

The analog signal is a continuous waveform that is generated by oscillations in air pressure applied to the microphone capsule. This response is a continuous and "pure" representation of the pitch and relative amplitude of the performer's voice/instrument as it affects the microphone capsule physically.

The digital signal is a translation of this analog waveform. You can see that the amplitudes over time are broken into segments, represented by each individual bar. In digital audio processing, these are known as Samples. The creation of a digital waveform from an analog waveform requires a technology called an Analog-to-Digital (AD) Converter.

So, what does this have to do with Stereo-Link? Simply put, the microphone inputs on your unit do not have the necessary AD converters to translate the signal into a digital format readable by Bluetooth. Since Bluetooth input from your phone/tablet/computer is already digital, no conversion is required, but, as explained, this is not the case for microphones.

Connection Instructions for Multi-Speaker Performance via XLR Cable

If your aim is to transmit your microphone signal across two linked speakers, this can be accomplished by connecting them via an XLR cable. Please see below for the full instructions on doing so.

1. With the Power Switch on each speaker turned to the ON position, connect each speaker to a power outlet. 

2. Plug an XLR cable into the MIX OUT located on the rear panel of one Total PA speaker. This speaker (the primary) is the one to which you will connect audio sources such as a Bluetooth device, microphone, or USB flash drive. 

3. Plug the other end of the XLR cable into the XLR Input on the rear panel of your second Total PA speaker. This second speaker will receive the audio from any devices connected to the 1st speaker (the primary).

4. Power on both speakers using their Power Switches.

5. Connect your audio sources to the 1st speaker (the primary). 

6. Make sure that each speaker's Master Volume control is set to the same position. 

7. With one of your audio sources playing, gradually turn up the Aux Input Volume on the second Total PA speaker until the volume of this speaker matches the volume of the first speaker (the primary). Your speakers are now connected via "hard-wire."

A Note About Bluetooth Microphones

You may be wondering, "If I use a Bluetooth Microphone, doesn't that invalidate the problem, since the signal is now digital?" The answer is a resounding not really. There are two reasons for this:

1) The Bluetooth receivers used by your speakers are expecting a LINE LEVEL audio signal, which is significantly louder than MIC LEVEL signal, which is what a Bluetooth microphone without built-in preamps will transmit. As a result, the balance between the music and the performer will not be correct, and the microphone will not be loud enough to compensate.

2) Bluetooth at any level introduces latency, which is the delay between the sound source emitting signal and the transmission of the audio from the speaker after it is received. If you were to use a Bluetooth microphone with devices in Stereo-Link, the latency would compound with itself, since you've got the latency from the Microphone to the Speaker, followed by the latency from the Primary Speaker to the Secondary Speaker. This would render synchronization with music impossible.

Given these limitations, it is not recommended to use Bluetooth microphones with these units in any cirumstance.