What Is an XLR Microphone, And Why Would I Want One?

An XLR cableCameron Summerson

Recently, microphone maker Blue announced a $ 100 professional studio microphone, the Ember. Then the question arose: What is that XLR problem and how to use it? Let's talk about what XLR is and why you could use it in your studio.

XLR is pro audio. That's what all recording and radio studios use, and that's what you'll see artists playing live on stage. This is because XLR cables carry a balanced sound, which is essential for sound clarity.

What is XLR?

First, let's define what XLR means. This is a simple enough abbreviation for X connector, Theconnection connector, RBoot ubber. The "rubber connector" portion of the connector is not always part of the equation today, however, as it is no longer needed. Despite the slight change in design, the name has remained the same.

There are currently several versions of XLR cables available with a variety of additional pins (XLR3 – XLR7), but here we are talking about the XLR3 or three pin cable. This is by far the most common type of cable.

In short, XLR is the ideal standard for high quality audio inputs, such as microphones. Indeed, they send a balanced signal that isolates the noise. It is simply a better type of connector for this type of application, but it is also so robust that it is not necessarily something that the average consumer really needs to think about using, unless it is for high quality audio recording or streaming.

Aside from an XLR mic and an XLR cable, you'll need some sort of audio interface or mixer so your computer can see the mic. A decent audio interface can be found for as little as $ 40-50, but better units can go for a lot more. The average enthusiast will probably want to spend between $ 150 and $ 200 for a good interface, much like the Focusrite Scarlett 2i2 is a good place to start, for example.

If you plan to record at home, you will also need a digital audio workstation (Digital Audio Workstation) to capture your recording. You can use something free like Audacity, although there are also great options that are cheap, like Reaper. You can read our photos for best DAW here.

The technical side of what makes XLR so much better than other audio inputs is, in fact, rather technical. Read on for all the juicy details.

The act of balancing

If you have already changed the batteries of your flashlight, you have probably noticed that there is a plus side (+) and a minus (-) side in the stack. If you only hang one side of the battery to the bulb of your flashlight, nothing happens. You need both positive and negative connections to turn on the light bulb. This is an electrical circuit. The electrons must form a complete loop from the negative pole of the battery, through the wire, from the light and back to the battery. The audio is no different: you need the positive and negative sides of an audio signal for everything to happen. A microphone pushes electrons on one side of the cable, the electrons are transmitted to an amplifier, and then back to the other side of the microphone.

The problem is that most audio systems treat the circuit as having only one wire, usually the center conductor of a coaxial cable, and simply combine the other wire with all the other electronics in the circuit. system. This creates an opportunity for several different types of noise to enter an audio signal chain:

Noise of the ground loop: Among my 35 years of experience with professional audio and video systems, this is the most common and annoying problem, especially when computers are used. Generally, you will hear this as a low hum, although this may also be manifested by static or irregular buzzing. Ground loops occur when audio takes two different paths to get to the amplifier: a path through your audio cable and a second path in your building wiring.
EMI and RFI: Transformers, motors, and high-frequency electronics can create magnetic fields that induce current in your audio leads. This creates a buzz, a buzz and can even carry audible radio signals if you are placed too close to an AM transmitter.
crosstalk: This occurs when a signal from the same system goes to another.

How do you fix this? In retrospect, the solution seems pretty obvious: you isolate the two wires of the signal chain so that the positive and negative halves of the signal are routed separately from anything else. The main advantage of a balanced audio signal (when it's done well) is that the audio signal never touches the ground plane of the amplifiers or other instruments in the system. There is therefore no possibility of crosstalk or ground loop.

For example, I work with a live band and a few weeks ago we had a problem with the "click track" generated by the music material used by one of the performers used on stage. The audio of the click track was leaking to the other outputs of its audio interface, which allowed to hear "beep beep beep" in the sound system. It was calm, but there. We disconnected the unbalanced audio cables that he was using and switched to balanced XLR cables. The problem is gone.

The other advantage is the rejection of noise. EMI and RFI work because a moving or changing magnetic field creates a voltage on a wire. In unbalanced signals, the magnetic field creates a voltage on the positive side of the signal, but not the negative (or perhaps the reverse). In a balanced cable, the wires are located one next to the other, which creates a magnetic field. creates the same signal on both sides.

Audio wavelengthsBy inverting the copy of the waveform, the interference cancels out and we end up with the same signal that we put on the wire. Tom Wilson

On the sending side, an XLR device creates a second copy of the audio and the reverse. On the signal reception side, the inverted copy of the signal is summarized in the original copy of the signal. And as in mathematics, where -2 + 2 = 0, a balanced audio signal rejects noise from outside sources.

Finally, your crosstalk capabilities are greatly reduced when the signals do not share the same ground plane. High end equipment using a fully internal balanced audio system has virtually no crosstalk.

Put this to good use

So, how can you put all this into practice? What's the point?

If you're watching Ember, you may be planning to stream to Twitch, record a podcast, or play music. In both cases, you can connect this Ember to a USB mixer (like the Mackie Pro FX8) and use the mixer as an amplifier for the microphone and a USB audio interface. You can also add another microphone for your Internet partner and connect other equipment, for example a musical instrument, another computer under Skype or Discord or just your smartphone.

The bottom line is that you need a mixer or an audio interface that includes phantom power (This is often indicated by a switch that says + 48V). Because the microphone needs power to work, you need something that can generate that power. This is one of the reasons why a mixer is a good choice for an audio interface because it incorporates phantom power directly into the unit. High-end mic preamps can also have phantom power, and some XLR Computer Audio Interfaces to have ghost power built in.

Other options

Finally, there are other options for sending a balanced sound in addition to XLR plugs.

TRS phone socketTom Wilson

TRS Phone sockets can also carry symmetrical signals. Cables with telephone jacks are often used in professional audio equipment to connect mixers and amplifiers, as well as to connect external equipment such as reverb processors, EQs, compressors, and audio recorders. Although the plug has the same appearance (and the same part) as the plugs used in high quality headphones, the ring serves the negative side of the audio signal.

You can also enjoy the benefits of a balanced audio cable with a device called mass loop insulator. This usually looks like a small box with two pairs of RCA jacks, or sometimes to mini-earphone jacks. Ground loop insulators have a 1: 1 audio transformer on the inside, which cuts the ground loops. If you connect a computer to a mixer or decoder, it is almost certain that you will get ground loop noise and AC hum. This almost always corrects these noise problems. You might even have this problem in the car when you connect your smartphone to your car stereo. ground loop isolator with 3.5 mm phone jack is a big help.

Why not a USB microphone?

Finally, you are probably wondering why this faithful USB microphone is not enough.

In fact, it's very good when you have to record one thing at a time. I have a good Samson USB microphone on my desktop for podcasting or streaming, and it works fine. But the problem with USB microphones is that you can not use more than one at the same time. USB audio devices each have their own clock to drive digital audio converters. If these clocks are no longer synchronized, you may receive ejections or interruptions in your recordings when your computer software attempts to correct these errors.

It's also more difficult to mix this way because you do not have these physical buttons to work. So, when I want to do something with more than one person at a time, I choose my desktop mixer and my faithful studio microphones connected in XLR.

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