Conference technology: different PA scenarios and what you need to make sure everyone will be heard

There are basically two modes for conferences: one person speaks to many or many people speak with each other. What both have in common is that speech should reach all participants.


The minimum requirements for a conference with audio gain

  1. Inputs: a way to put sound into a sound system. For acoustic sources, such as voices, the input is typically a microphone.

  2. Signal processing: as the name implies, the signal entering the input is somehow altered. There are two types, mixers and more specialised signal processors. A mixer combines signals from different sources and processes from two to several hundred inputs. Other signal processing devices provide various helpful functions.

  3. Amplifiers: these devices combine the individual channels and increase the level. The amplifier can provide features that the signal processing also offers, and vice versa. Items 2 and 3 regularly overlap.

  4. Outputs: what goes in at the input should reach the listeners as clearly as possible. The output is usually a speaker, headphones or in-ear monitor.


Inputs: which microphones for conferences?

Put yourself in the shoes of the audience: what kind of microphone would you be happy with? Here we give only a brief overview of the most important versions:

Clip-on microphones or lavalier microphones are above all unobtrusive. If you are giving a product demonstration, for example, use a lavalier microphone or headset. The presenter can handle a model or other objects without thinking much about the microphone, as they have their hands free. Clip-on microphones should be placed slightly below the neck, not too far from the mouth. Here it is important that the speaker turns their body rather than their head when they speak.

Gooseneck microphones are required when a person cannot or will not hold the microphone themselves. Such microphones can have different polar patterns, but the most commonly used are cardioid and supercardioid. The person speaking should sit directly in front of the microphone. The neck of the gooseneck microphone is flexible so that the person speaking can adjust the microphone in a way that is most comfortable for them. Most of these microphones have a desktop base, but there are also clip-on options, for example to attach them to the edge of a table.

Headband microphones or earband microphones are often simply called headset microphones. They are perfect for streamers or coaches, but also for conferences and speakers. The wireless headset microphone system consists of a headset microphone, a wireless transmitter and a receiver. The construction is robust, so you can think more about the topic you are talking about and less about the microphone.

The main feature of boundary microphones is that they can either be placed on a flat surface or attached to a wall, theoretically even to the ceiling. The different polar patterns allow you to choose from which sides the sound should be picked up. The advantage is that these microphones do not amplify individual voices but increase the overall quality of the sound in the room. Especially if the audience is allowed to ask questions, boundary microphones in the room are useful.

And it is an art whose subtleties are unknown to most people. That is why it is generally good to relieve speakers of this burden. Furthermore, you thus enable speakers to gesticulate more naturally, which lowers the barrier to the audience.

At what point are microphones required at all?

A small group of people can hold a conference without PA technology. However, there are cases where amplification would be still useful, even if the audience is not very large. In those cases, the characteristics of the venue are relevant:

  • Size of the room
  • Existing furniture
  • Carpets and curtains
  • Ceiling height

If you know that the venue is acoustically challenging, it is advisable to equip the speakers with microphones. Another reason for microphones can be the necessity to simultaneously translate multiple languages. Then one or more interpreters sit in isolation booths, listen and translate in real time. Their audio signals go to the central unit, which then relays them to target units. This is usually done via headphones, not speakers. This is where a tour guide system makes sense for smaller groups that need translation.

Signal processing: small helpers, big impact

Signal processing concerns devices that help solve a variety of problems in the signal chain. This can be achieved in various ways:

  • Easy sound and volume adjustment
  • Feedback control
  • Dynamic effects such as compression or limiting
  • Automatic mixers (rarely relevant for conferences)
  • Echo suppressors (rarely relevant for conferences)
  • Time-based effects such as reverb and delay (rarely relevant for conferences)

Remember, it is always better to prevent problems in the signal chain instead of solving them afterwards. The most important thing remains the optimum positioning of microphones and speakers.

Signal processing is usually part of the mixing process, where several devices can be connected in series. While most systems for speech transmission have limited processing options, it is useful to know the basic functions of each type of processor. The following functions are relevant for conferences:

  • An equalizer influences the frequency response of the signal, increases the bass range and can thus impact e.g. speech intelligibility.
  • A noise gate can really work wonders at conferences when it comes to reducing unwanted background noise. Especially when it is unavoidable that several microphones are active at the same time. It works like this: the output signal is switched off ('gated') when the level falls below a certain threshold. So, if three microphones are open, but only one person is speaking, the audience will not hear any rustling of clothing or handling noises via the other two microphones.
  • An (RMS) compressor reduces the dynamic range of a signal by reducing volume differences between the loudest and the quietest signal. This is done by reducing the level of all signals above a certain user-defined threshold by a certain amount. The amount of reduction is expressed as a ratio. The higher the ratio, the more the volume of loud signals is reduced. Some compressors feature presets for specific scenarios. You should consider these if you do not want to deal with attack, sustain, decay and release in detail yourself. A general rule says, longer attack times sound more natural, but can miss signals that should actually be compressed. Short attack times, on the other hand, are more effective in preventing loud transients.
  • A limiter is useful for avoiding distortions and protecting the components of the PA system, especially the speakers. It reduces signals above a certain threshold by a certain ratio. A limiter is basically a reverse compressor and usually the last device in the signal path.

The amplifier: volume and channel connection

The PA amplifier brings several audio sources and inputs together. The number of inputs is particularly important. How many sound sources do you have to bring together? Similarly, the mixer also has a certain number of outputs. Moreover, many amplifiers have features that make PA scenarios easier. After input processing and mixing, the audio signal goes to the output stage of the mixer, which transmits the signal to its destination, usually the speakers, via the master volume control. Many systems require multiple outputs, with the amplifier passing the mixed signals to different destinations as required.

PA-812DAP

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Mono class D PA mixing amplifier, with integrated MP3 player, FM/DAB+ tuner and Bluetooth. 1 x 120 W Class D concept with high…

Outputs: speaker (systems) or tour guide systems?

Speaker systems: speech situation few to many

At conferences, either mobile PA systems or wall speakers and ceiling speakers are used. Due to their extremely precise sound radiation and the frequency range, column speakers such as the ETS-360TW/WS are suitable for various applications: lectures, panel discussions, but also for official celebrations with background music. The two bass speakers, four bass-midrange speakers and the tweeter produce a sound pattern that also transmits voices particularly well.


The complete solution: a professional lectern, for temporary or permanent microphone stations

 

Integrated amplifier technology and speaker technology make active lecterns like the SPEECH-104D solutions with which nothing can go wrong. If you are speaking as an individual to many listeners, a quick solution that does not require a big accompanying system would be appropriate for speech reproduction and dubbings of films or presentations. Here, we would recommend a gooseneck microphone.


The complete solution: a professional lectern, for temporary or permanent microphone stations

 

Integrated amplifier technology and speaker technology make active lecterns like the SPEECH-104D solutions with which nothing can go wrong. If you are speaking as an individual to many listeners, a quick solution that does not require a big accompanying system would be appropriate for speech reproduction and dubbings of films or presentations. Here, we would recommend a gooseneck microphone.


Tour guide systems: speech situation many to many

Systems for 2-way communication make sense, if there is to be an active exchange among participants. Systems like the ATS-80ST transmit up to 42 channels in parallel. A microphone will be connected via the corresponding transmitter, every listener gets a receiver. For a situation where many speak with many, the conference system with individual desktop microphones from JTS is also worthwile.

What to do in case of acoustic feedback?

First aid for feedback: lower the (master) gain to stop the annoying howlback. So far, so easy. Feedbacks are often caused by a badly placed microphone or incorrectly positioned speakers. In the end, good sound without feedback always means balancing the necessary acoustic gain as accurately as possible. Too much level in the PA system is not good, still, every person in the room should have the optimum sound. Here are some quick tips:

  • Reduce the number of open microphones. That also reduces the number of possible interferences immediately.
  • Use directional microphones with cardioid and supercardioid polar pattern. This also applies to speakers, i.e., they should be aligned as precisely as possible.
  • If possible, set up the speakers closer to the audience.
  • Put the microphones as close as possible to the sound sources (in most cases the person speaking). Or rather the other way around, the speakers should sit as close to the microphones as possible.
  • Position the microphones in a way that puts the intended sound source onto the axis, where the zero point of the polar pattern is used to avoid unwanted noises.
  • Use a feedback controller, as in this example, that automatically eliminates the irritating feedback frequency with minimal effect on the remaining level.

We are happy if we can make your daily project routine easier for you as an installer and expert planner. That is why we are a solution provider, not just a retailer. Your Project is Our Project.

 

Header graphic: AdobeStock Seventyfour

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