photo: Real Traps

If you want to hear dialogue, listen to music or record, better room acoustics are more important than expensive gear

Better sound comes from better listening rooms introduces how changes to a room can make sound better

Yesterday I studied Ethan’s web site again to learn why.

The un-science of sound waves and room modes

Sound waves bounce off things like floors, walls and ceilings. In a reverberant room like a swimming pool, the echoes make it hard to hear someone close by so we yell. The more everyone yells, the harder it is to hear from all the sound waves echoing back.

Room nodes for 13 x 12 x 8 room. The horizontal line is normal response, higher vertical lines means those frequency are louder than normal, two lines together indicate fundamentals are reinforcing each other.

That’s what goes on in listening rooms, especially with bass notes. Every room has a fundamental frequency that is derived from the length, height and width. Bass sounds have lots of energy and keep bouncing off surfaces while mids and highs are weaker and die out faster – unless the room is all hard surfaces like the swimming pool.

My TV room is 13 long, 12 wide and 8 high. The fundamental bass frequencies of the room – that is the not that hits a surface right on and bounces back – are 43 Hz, 47 Hz,  and 70 Hz. The problem starts when these fundamental notes or modes start to reinforce each other.

In the graph, things are a little dicey around 43 and 47 Hz getting above normal volume but not bad.

Problems occur with the harmonics around 150 just below the frequency of male voices.

To hear voice distinctly, the volume goes up and along with it the muddy bass notes.

The problem can only be fixed by stopping the bass from bouncing around for 600 ms or so.

It takes bass traps which are not cheap – like $200 to $300 each. That room needs one in each corner. Bass sounds collect in corners – don’t ask me why.

Here’s the second room – 16.75 x 12 x 8 – which I use as a music and recording studio. It has different problems.

Room nodes start at 70 Hz on 17' room and get worse whenever the vertical line is above the normal response indicated by the horizontal line.

The bass starts to get too strong at 70 Hz which is a common place to bass and kick drums sounds. From 150 Hz to 490 Hz there are lots of modes that are higher than the average sounds.

Nodes mean the sound is reinforced by the room and appears louder than it is.

The sound recorded in that room will be muddy.

To compensate I keep the mic very close to the guitar or my mouth to avoid the effect of the voice modes. That is a partial solution but eliminates room ambiance, an important part of the sound.

Look what happens to the room when I open the double doors to create one large room.

Nodes for 29 by 12 room. The first reinforcement of bass has been moved above the troublesome 80 Hz level. The peak is now about 250 Hz and declines after that.

With a longer room, bass reinforcement starts later – at 100 Hz – which explains why the bass guitar on Blood on the Tracks sounded clean and defined in a larger room.

Bass reinforcement at 140 Hz is bad but I could take that out with equalization in recording or post production.

Things get pretty messy between 200 Hz and 350 Hz and it would be hard to EQ that out: however, the sound is better than either room by itself.

What the room or rooms need are some bass traps. However, they need less than they do as separate rooms since some problems are solved by the different dimensions.

More about that later.

Thanks to Ethan Winer for the free software to analyze my rooms. It’s called Real Traps ModeCalc. Don’t wait two years to read the Help file tutorial. It does make sense.

Thanks also to iWebtrix for casually suggesting  that I tear out the wall between the two rooms.