John Sayers' Recording Studio Design Forum Archive

So what can we work out with this calaculator?

Let's start with a room with the following dimensions.

Length 6 metres
Width 5 metres
Height 2.4 metres.
and with all the walls and ceiling in painted concrete and the floor in unpainted concrete. (i.e. we are going to treat the garage) We are then going to add the typical treatment (you know, get out the egg cartons, heavy drapes and curtains etc)

Carpet on the floor
Heavy drapes on the rear wall
Heavy drapes on the front wall
Light drapes (egg cartons) on the side walls
Light drapes (egg cartons) on the ceiling.


The original room has a relatively flat response (Bright Blue), albeit a bit long all over and especially in the top end, and would sound very bright and live with reverb times around .8 sec. When the typical treatment is applied we land up with a room that has a long reverb time at 125Hz and short at 4kHz. Because the high end reverb is shorter people will say the room is dead but in fact it's not really, it's only dead in the top end and too dead at that. The frequencies below 500Hz are the real concern.

This is the mistake everyone seems to make. All the treatment added only effects the high frequencies. You must consider all the frequencies when you treat a room. The shorter reverberation time in the high end is reasonable at 0.3 sec (around 0.4 -0.5sec is desirable) but you must take down the low end as well. The reverb time at 125Hz is around 2 sec, at 250 it's 0.92 sec,at 500 it's down to 0.49 sec and it reaches 0.3 sec at 1000Hz and is right down to 0.21 sec at 4kHz. The low mid and lows need correct treatment. See the low-mid and low frequency absorber pages.