How to Position Microphones and Speakers to Reduce Feedback

Microphone feedback is one of the most recognisable problems in live sound. The sudden whistle, ringing tone or howl can interrupt a wedding speech, presentation or performance almost instantly. Although feedback is often blamed on the microphone, the microphone itself is rarely the whole problem. Feedback occurs because of the relationship between the microphone, loudspeakers, room and the level at which the sound system is operating.

One of the most effective ways to reduce the likelihood of feedback is therefore established before anyone begins speaking: position the microphones and loudspeakers sensibly.

The basic principle is straightforward. A microphone should capture as much of the wanted sound as practical while picking up as little amplified sound from the PA as possible. The loudspeakers, meanwhile, need to direct useful sound towards the audience without unnecessarily feeding that sound back into the microphone.

Understanding that relationship can prevent many feedback problems without simply turning the entire system down.

Keep Microphones Behind the Main Loudspeakers

For a conventional PA setup, the main loudspeakers should generally be positioned so that the microphones being used by presenters, singers or performers remain behind the main speaker line rather than directly in front of the loudspeakers.

Imagine two loudspeakers positioned towards the front of a presentation or performance area and directed towards the audience. The person using the microphone would normally remain behind the imaginary line running between those speakers.

There is a practical reason for this arrangement. The loudspeakers are producing amplified versions of the signal entering the microphone. If a microphone is moved into an area where it receives a strong direct signal from those loudspeakers, more of the amplified sound can return to the microphone. That signal passes through the system again, is amplified again and returns to the microphone again.

When the gain around that loop becomes sufficiently high at a particular frequency, the system begins to feed back.

Moving the microphone farther behind the loudspeakers can improve the acoustic separation between the source being amplified and the output of the PA. The loudspeakers can then project sound towards the audience while the microphone primarily captures the presenter or performer.

This principle is particularly important with handheld microphones because people can move. A system may be completely stable while someone is standing in the correct position and begin to ring as soon as they walk forward towards a loudspeaker.

Before a function begins, it is therefore useful to establish where presenters, MCs or performers are likely to stand and where they may move.

Point the Loudspeakers at the Audience, Not the Microphones

Loudspeaker direction is just as important as microphone position. The purpose of the PA system is to provide appropriate coverage for the audience, so the speakers should be positioned and aimed with the listening area in mind.

Audio Hire starts audience sound-system recommendations with at least two loudspeakers. This allows speaker placement and coverage to be considered across the audience area rather than attempting to make one loudspeaker cover an entire gathering.

Simply turning the loudspeakers away from the microphones is not enough if doing so also points them away from the audience. The objective is to achieve both things at once: useful audience coverage and sensible acoustic separation from the microphones.

For a typical speech or presentation, two main loudspeakers may be positioned towards the front of the audience area, with the speaking position behind them. The loudspeakers can then project into the room while the microphone remains comparatively isolated from their direct output.

The exact positions depend on the room. A wide function space, long conference room, outdoor gathering or live performance area can each require a different approach. Audience position, room dimensions, walls and reflective surfaces all influence how sound behaves.

The important point is that speaker placement should not be treated as an afterthought. Putting the loudspeakers wherever there happens to be spare floor space and then trying to solve the resulting problems with mixer controls is rarely the best approach.

For broader information about selecting and positioning a complete PA, see PA Hire Adelaide and Sound System Hire Adelaide.

Keep the Microphone Close to the Person Speaking

Physical separation between the microphone and loudspeakers helps, but microphone technique is equally important.

A person speaking into a microphone from an appropriate distance provides the system with a relatively strong wanted signal. If that same person lowers the microphone towards their chest or holds it a long way from their mouth, their voice reaches the microphone at a much lower level.

The natural response is often to increase the microphone gain or channel level until the audience can hear them again. Unfortunately, increasing the system's sensitivity also increases its ability to pick up sound arriving from the loudspeakers and the surrounding room. The amount of useful gain available before feedback can therefore decrease.

It is generally much better to improve the wanted signal at the microphone than continually increase the PA to compensate for poor technique.

A handheld microphone such as the Shure SM58 is designed to be used relatively close to the voice. Keeping the microphone reasonably close and maintaining a consistent distance helps provide a strong direct signal.

The microphone grille should also remain unobstructed. Cupping a directional microphone around the grille can alter its acoustic behaviour and may make feedback control more difficult. Hold the microphone by its body and allow the grille to operate as intended.

Our microphone technique guide covers microphone distance, handling and speaking technique in more detail.

Understand Where a Directional Microphone Rejects Sound

Many microphones used for live speech and vocals are directional. Rather than picking up sound equally from every direction, they are designed to be more sensitive to sound arriving from particular directions and less sensitive to sound arriving from others.

The Shure SM58, for example, uses a cardioid polar pattern. Its primary purpose is to capture the voice in front of the microphone while providing useful rejection of sound arriving from other directions.

That characteristic can help when positioning microphones in relation to loudspeakers, but it should not be treated as a magical feedback-prevention system. A directional microphone can still feed back if it receives enough amplified sound from the PA.

Microphone orientation therefore matters. A handheld microphone should be pointed towards the person speaking rather than casually aimed towards a loudspeaker. Someone who lowers an active microphone and allows its grille to point directly towards the PA can substantially change the relationship between the microphone and loudspeaker.

This can happen easily during weddings and corporate functions. An MC finishes an announcement, lowers the microphone to their side and turns towards a loudspeaker. The microphone is still active, but its position and direction have changed completely.

The same issue can arise with microphones on stands. The stand should be positioned so that the microphone serves the speaker or performer while maintaining a sensible relationship with the PA. A microphone stand can help maintain a consistent microphone position where a fixed speaking or performance location is appropriate.

Movement Changes the Feedback Risk

A microphone and PA system should not be tested only in one position if the person using the microphone will move during the function.

A wedding MC might walk between the bridal table and dance floor. A corporate presenter may move between a lectern and presentation screen. A comedian or performer may use the entire stage. During audience Q&A, a wireless microphone may travel throughout the room.

Each movement changes the physical relationship between the microphone and the loudspeakers.

This is one reason wireless microphones need to be tested across their actual operating area. Wireless technology gives the person freedom to move, but that freedom also makes it possible for them to walk into positions that would never occur with a microphone fixed on a stand.

During the soundcheck, have someone speak normally into the microphone while moving through the areas that will actually be used. Listen for ringing or changes in system stability as the microphone approaches different positions.

If there are areas where the microphone should not be taken, establish that before the programme starts. An MC or presenter does not need a lesson in acoustic theory. A simple instruction about remaining behind the main loudspeakers may be enough.

This is especially useful where an audience Q&A microphone is involved. The person carrying the microphone should understand where the loudspeakers are and avoid pointing the microphone directly towards them while moving around the room.

Room Reflections Can Still Contribute to Feedback

Keeping microphones behind the loudspeakers significantly improves many PA setups, but sound does not travel only in straight lines.

Once sound leaves a loudspeaker, it interacts with the room. Walls, ceilings, floors, glass and other hard surfaces can reflect some of that energy. Those reflections can eventually reach the microphone even when the microphone is not directly in front of the loudspeaker.

This is one reason some rooms are more difficult than others. A highly reflective function space may produce substantially more reverberant sound than a room containing absorptive furnishings and surfaces. The PA can sound loud while speech remains difficult to understand because the audience is hearing a mixture of direct and reflected sound.

Increasing the microphone level is not necessarily the answer. More amplified sound also means more acoustic energy entering the room, potentially strengthening the sound that returns towards the microphone.

Appropriate loudspeaker coverage becomes particularly important in these spaces. The objective is to put useful sound where the audience needs it rather than simply filling the entire room with more level.

Microphone technique becomes even more valuable as well. A strong direct voice signal reaching the microphone gives the sound system more useful material to work with before additional gain is required.

Monitor Speakers Need the Same Consideration

Live music introduces another important loudspeaker relationship: stage monitoring.

A singer may be positioned correctly behind the main PA but still have a monitor loudspeaker operating nearby. That monitor can become part of the same acoustic feedback loop if its output reaches the vocal microphone strongly enough.

The appropriate relationship depends partly on the microphone's polar pattern and the monitoring arrangement. This is why monitor placement in professional live sound is considered in relation to the microphones rather than simply placing a loudspeaker at the performer's feet and increasing its level until it is loud enough.

More monitor volume is not always better. The performer needs to hear what is necessary to perform effectively, but excessive stage level can reduce the amount of gain available before feedback and make the overall sound more difficult to control.

For a straightforward speech, wedding or corporate presentation, stage monitors may not be part of the system at all. For live music, they become another component that needs to be considered alongside the microphones and main PA.

This reinforces the broader principle: feedback is a system problem. Every loudspeaker capable of sending significant sound back towards an active microphone can affect the result.

Position First, Then Soundcheck

Mixer settings and equalisation can play important roles in professional sound reinforcement, but they should not be used to compensate unnecessarily for poor physical placement.

Start with the fundamentals. Position the main loudspeakers for useful audience coverage. Keep the speaking or performance position appropriately behind them. Point microphones towards their intended sources rather than towards the PA. Keep microphones reasonably close to the people using them and consider where those people will move.

Then test the complete arrangement.

Speak or sing through the microphones at realistic levels and listen from the audience area. Move handheld and wireless microphones through their expected operating positions. If several microphones will be active simultaneously, test them together rather than assuming the system will behave exactly as it did with only one microphone operating.

Our microphone soundcheck guide explains this process in more detail, while How to Stop Microphone Feedback at a Function covers the wider causes and troubleshooting of feedback.

Good microphone and loudspeaker placement does not mean feedback becomes physically impossible. It gives the system a much better starting point and can provide more useful operating level before feedback becomes a problem.

If you are planning a system yourself, browse Microphone Hire Adelaide and Speaker Hire Adelaide. If you are unsure how the microphones and loudspeakers should work together for your function, tell Audio Hire about the venue, audience, programme and how the microphones will be used. That information makes it much easier to recommend an appropriate complete setup.