Treating a spare room for podcast recording

Every few weeks someone writes in to ask how we make the show sound the way it does. The honest answer is a small spare room, three decent microphones and a fair amount of trial and error with the walls. The microphones matter less than you would think. The room matters more.

Treatment is not soundproofing

Soundproofing keeps noise out and needs mass, sealed gaps and usually a builder. Treatment controls what happens to your own voice inside the room, and that is what makes the difference between a show that sounds intimate and one that sounds as if it was recorded in a bathroom. A bare spare room reflects speech off every flat surface, and those reflections arrive at the microphone a fraction later than your voice, which smears the words.

Where the panels go

Start with the walls directly behind and in front of each speaker, at head height, then the ceiling above the table. Those are the first reflections, and treating them does most of the work. Thick panels of mineral wool wrapped in fabric beat thin foam tiles by a wide margin. A bookcase full of rulebooks and boxed games is surprisingly good on the back wall, because the uneven surface breaks reflections up.

Rugs under the table and a heavy curtain over the window finish the job.

Leave a gap behind the panels

This is the part nobody told us. Panels fixed flat against an outside wall stop that wall breathing. In winter the wall is cold, warm breath from three people talking for two hours meets it behind the panel, and the moisture has nowhere to go. One listener in Maryland took down a row of foam tiles after a year and found the plaster behind them black from skirting to ceiling. He had to get Baltimore mold professionals in to treat the wall before anything went back up, and the panels went in the skip. The lesson applies anywhere: mount panels on battens or brackets with a two-to-five centimetre air gap, keep them off outside walls where you can, and take one down every few months to look behind it.

Ventilate between takes

A small room fills with warm, humid air quickly when people talk for hours. Open the door between segments, run a quiet fan when you are not recording, and keep a hygrometer on the shelf. Anything that stays above sixty per cent through a session is worth a dehumidifier running overnight afterwards.

Test before you buy more

Record a minute of talking in the empty room, then again after each change, and listen back on headphones. Most rooms need far less treatment than the shops suggest, and the money is usually better spent on a second microphone stand than a tenth panel.