Nobody can understand the speaker — and louder does not help

Why louder changes nothing

Two things reach you from the loudspeaker: the sound that took the direct path, and the sound that visited walls, ceiling and floor first. What you understand is the direct one. The other is the soup the syllables dissolve in — it no longer carries information, only energy.

Turn it up and both get louder to exactly the same degree. The ratio stays precisely as it was — and that ratio decides intelligibility, not the level. That is why turning up does not improve it. It even makes it worse, because a reverberant room rings on longer at higher level and the next syllable gets buried under the previous one.

The number for this is reverberation time. For speech you want roughly one second. An untreated village church sits at three to six. That is why the same system works in a parish hall and fails in the church.

What works instead, ordered by effect

1. 1Get closer. Halve the distance to the listener and the direct sound gets 6 dB louder — the reverberant field does not, it is roughly the same everywhere in the room. That is exactly what shifts the ratio. Two small loudspeakers in the middle of the room beat one big pair at the front, and by a wide margin.
2. 2Aim downwards. Sound that never hits the wall never becomes soup. A loudspeaker with a narrow coverage angle, aimed at the pews rather than into the nave, sends a far greater share of its energy into ears instead of into stone.
3. 3Leave out what is not needed. Every extra loudspeaker covering the same area adds another path — and it is paths that smear syllables. Two boxes serving the same pew are worse than one.
4. 4The equaliser last. The low mids between roughly 200 and 500 Hz carry little intelligibility but a lot of energy, and a reverberant room reinforces them on top. Cutting them makes speech clearer without making it louder. A high-pass against everything below 100 Hz belongs with it. It helps — it is just the smallest of the four levers.

What does NOT help, obvious though it seems

Boosting the highs. Intelligibility sits between 2 and 4 kHz, and lifting it there sounds clearer at first. But the room reverberates in that range too, so you lift the soup along with it — two minutes later it sounds harsh and you still understand nothing.

And absorbers are the only thing that really changes the room, but in a listed church you are not allowed them and in a parish hall you usually do not want them. That is why placement heads this list and not building acoustics: placement is what you can actually do.

How you can measure it

Reverberation time is the one number that tells you what you are dealing with. If it is above two seconds, it is clear that the answer lies in placement and not in the equaliser — and you stop turning filters that cannot achieve anything.

After that a second measurement further back helps. If the difference between front and back grows large, you need loudspeakers closer to the rear rows. If it stays small, the problem sits elsewhere.