Audio tools: How we make your backline perfect

• DI boxes and other transformers
• Backline combiners and signal splitters
• Preamplifiers for microphones
• Signal processing for stage and FOH
• FLY: an affordable option to upgrade a PA system with radio transmitters
• Audio tools to prevent acoustic feedback

It is important to us to involve musicians and event organisers in the development process of our products. Many technicians at IMG STAGELINE are musicians themselves, used to be event professionals or organise, mix and monitor concerts in their spare time. This helps us tremendously to understand the requirements of musicians and event organisers. What are the little problems on small stages and what little helpers can solve these (little) problems? Because this issue is so important to us, we do not just take high-quality PA systems and comprehensively designed mixers into consideration, but also the perfect connection of all major stage components.

Why do musicians and live clubs require DI boxes? These little boxes are, in a sense, guarding your sound. They ensure that good sound gets undamaged from the sound source to the mixer and PA system (and that bassists do not have to set up mics for their amps). In general, there are 3 reasons to invest in a good DI box.

1. Transmitting audio signals via cable has one drawback: the quality suffers with increasing distance.

   With regard to concerts, the longest distance is usually between stage and mixer or PA amplifier. Even in medium-sized clubs, this is problematic. Even though wireless solutions exist, they are not always available. With a DI box integrated in the signal chain, your sound remains crystal clear.

2. A DI box helps to avoid interferences

   You should always bring one of these small boxes, because, if you insert the box between microphone and pickup, this could prevent hum loops.

3. A DI box also controls the input impedance of the audio source according to your wishes.

   This allows bass and keyboard to transmit directly to the mixer and by that eliminates one source of error. Therefore, you do not need a microphone in front of the bass box. The stage will be quieter and the mixer's (or your) job easier.

These underrated helpers allow you to distribute the line signal at your discretion from the stage to different outputs. For us, the most important quality characteristic of these devices is not the amount of features, but the minimum possible loss of sound quality. Like a DI box, a splitter or combiner should change the sound as little as possible.

A combiner is the opposite of a splitter and harmoniously combines several audio signals. Especially DJs need combiners if they mix several audio signals via turntables. Sometimes 2 mixers are connected to one amplifier, usually when the technician at the FOH mixes a PA system and the monitoring with separate mixers.

Why use a line splitter?

If you use a line splitter and a compact recording interface at one of your concerts, all you additionally need for a decent live recording is a laptop. Such a recording is usually not suitable as a fully-fledged release, but it can fulfil 2 functions: if the gig was good and you feel comfortable with it, you might be able to release it as a live recording for die-hard fans. On the other hand, a live recording is a good opportunity for bands and musicians to look for potential in their own performance. Where did you hit a wrong note, where did the voice become a bit flatter?

Our LMS-808: both line mixer and line splitter

With the LMS-808, we have a device in our product range that is intended to be as affordable and efficient as possible in several live scenarios. Therefore it features 3 operating modes:

1. Mixer or combiner operation: the LMS-808 mixes up to 8 mono input signals (6 x line/mic and 2 x line) to 1 stereo output.
2. Splitter operation: for splitting 2 mono line inputs to up to 6 mono outputs.
3. Level matching amplifier operation: if your current setup does not require the first 2 modes, the LMS-808 is also a powerful amplifier with up to 6 input signals.

In plain language, preamplifiers amplify an audio signal, in practice usually a microphone signal that is too weak. These small amplifiers precede mixers. Especially dynamic vocal microphones sometimes lack the necessary power and the mixer cannot receive a strong signal. A microphone signal which is too weak loses valuable dynamics, in which case even adding more gain at the mixer does not help anymore. If the dynamics are already lost due to the weak signal, the mixer only amplifies the undynamic, quiet signal. And even if the stage mics are loud enough due to more gain, this also amplifies the noise from the stage. The solution are microphone preamps. Preamplifiers are also worthwhile in your home studio, in case the interface does not provide enough power, for the continuously adjustable low cut or because the preamp sounds more harmonic.

Granted, the term 'signal processing' fits many of the tools we offer. However, in this category we have grouped various useful audio engineering tools that make it easier to efficiently manage your audio signal as you go along - and that do not fit into our other categories.

Sometimes cables are not an option. For example, because the audience is between the mixer and the PA system and the cable paths are open, or because open cable routes are not optimal or even dangerous for another reason. Sometimes cables are simply annoying. It is definitely a relief not to have to transport, lay and later roll up any cabling. So how about turning your PA system into a wireless PA system?

1. Expand a pre-wired PA system with additional speakers at a greater distance. The space in front of the stage is big (city festival, small festival) and you want 2 additional PA speakers in 30 meters distance as support? Plug the FLY receiver into the line input of the speaker, the transmitter into the mixer, and you are ready to go.
2. A wireless (PA) sound system in several rooms, for example in labyrinth-like pubs and clubs? Or is the band also supposed to be heard in the beer garden? In that case, a sound system with PA technology is not sufficient. With FLY, an upgrade is easy and straightforward.

Our FLAT-M monitor speakers basically fit into the category of PA systems. However, we have designed our FLAT-M series in such a way that it is particularly flexible and can be used as a mini vocal system, as sidefill, as a drum monitor or for the rehearsal room. Included is also a Class-D amplifier system with tone potentiometer, i.e. signal processing.

Physical equalizers help you to control frequencies that can cause unpleasant acoustic feedback in live performances. First, you can avoid acoustic feedback by using lower levels on stage and in the rehearsal room. Additionally, microphones with a supercardioid polar pattern are less susceptible to acoustic feedback. However, sometimes the howlback just will not stop, especially in tight spaces or on small stages. In those cases a parametric equalizer can help, namely as follows:

1. Find out which channel generates the acoustic feedback.
2. Turn off the channel completely and then gently turn it back on until the howling sound starts.
3. Choose a low bandwidth, as a high bandwidth would change the sound dramatically.
4. Now lower the level of the middle or upper band by about 6 dB.
5. With this method, you can use a parametric equalizer to specifically search for acoustic feedback sources and eliminate them.

However, always keep in mind that an equalizer also changes the sound. If you have to work a lot with the EQ, also try to prevent acoustic feedback by using microphones that are resilient against acoustic feedback.

One example is the DEQ-230. You can control and adjust all the functions of this multi-functional equalizer via PC by using free, easy-to-use software: delay, RMS compressor, limiter and high-pass/low-pass filters. This works via the USB interface or RS-485 interface. Your settings are simply stored in presets, similar to a digital mixer.

An overview of the DEQ-230:

Really stubborn acoustic feedback? MFE-212 can help - whether monitor or FOH