5 ways to minimise PA system reverb

Reverb: great for adding warmth and depth to music, a pain in the proverbial when you're trying to set up your PA system. As Chris, the latest addition to Jigsaw AV, happens to have an audio background (he's a member of the ISCE and IOA), we thought we'd get him to tackle the thorny issue of how to ensure your public speaking setup sounds its best when it's not being appropriated by the local garage band...

1. Use an appropriate source

If it's been said once it's been said a thousand times, but given the number of people who ignore it, it bears repeating: get the right product for the job. Don't go for a source that's too big or overpowered - you don't need a stadium grade loudspeaker for your boardroom - but equally don't opt for anything that'll struggle to reach the required Sound Pressure Level (SPL).

Another important issue that often gets overlooked in DIY installations is the fact that you'll need to choose something that'll radiate the sound in the direction you want - steerable speakers give you far better control over this, and have gained a lot of traction in presentation environments over recent years.

2. Keep the source as close to the listener as possible

Keeping the source local to your listeners is one of the easiest ways to cut down on reverb. Short of delivering your pitch in an anechoic chamber there's no way to remove reverb entirely, but keeping the source close to the listener will mean that they will be experiencing more sound directly radiated from the loudspeakers and less reverb from the room. Simple, but really important. To achieve this, mounting location for your loudspeakers are important, get the best locations possible within the design constraints.

3. Balance coverage and listener distance

While on the one hand, keeping sources local means keeping your sound clean, the further away from your audience a source is, the more coverage it can provide. The trick to this is to balance the benefits of added coverage against the reverberation time problems. In oddly-shaped spaces, multiple short throw loudspeakers will allow you to fill in quiet areas and provide controlled coverage. If devices are used to cover larger areas, beam steerable products such as the Intellivox from Duran Audio can provide the control you need to avoid unnecessary excitement of empty space.

4. Add or reduce the amount of room absorption

Various types of audio reproduction require different amounts of reverberation. If you're kitting out a music venue, reverb can add much-needed depth and warmth to a band's sound, but it tends to simply make life difficult in public speaking settings. If you have issues with RT due to restricted source mounting positions, (for example, if you're kitting out a listed building and the owners don't look kindly on your plan to drill holes in their hard, reflective stone surfaces to mount additional speakers) varying the amount of absorption can help remedy the situation.

As well as off the shelf wall-mounted panelling from Roominators and the like, you can now pick up portable acoustic absorbers that are great for temporary spaces like events, or anywhere where you're not allowed to stick things all over the walls. We can also help you put together custom kits tailored specifically to your presentation space and system.

5. Use the right frequency range

If you're reproducing speech, bear in mind that your speaker's not going to go under 500Hz or over 400KHz, so you can use a graphic equaliser or high and low pass filters to narrow the frequency bandwidth. This will cut out a lot of unnecessary noise and make the speaker far easier to understand. If you're using an active speaker system, you're also going to want to employ filters to make sure the correct loudspeakers are producing the right frequency ranges.