Reflections

After the bass treatment, the next important thing to get a clear sound is to get rid of acoustic reflections from walls, ceiling, floor and table.

To find reflections, there is a nice graph in REW, which shows all reflections over time in spikes.
You should measure each speaker solo for the ETC diagram.

As you can see at time=0 this is the main signal, the few crazy spikes to the right of it are table reflections, and everyting else after this are room reflections.

The rule says every spike over -20dB (blue line) is very bad and must be treated, every spike over -25db should be treated.

The best thing to approach reflections are acoustic panels. Out there are so many providers of acoustic panels, so it's just a matter of price and taste which ones you like to pick. Most important thing is frequency response, so you also get some of the bass absorbed.

I decided to build my panels myself. I bought some Basotect plates from a german discounter, built a small wooden frame and covered them in cloth again.

Spooky resonances

So after the fine treatment of the bass except the low frequencies (25-50Hz) I wanted to find out what is causing this strange behaviour.

I used REW to generated som sinus waves with 37Hz and turned up volume.

Then I went around the room and checked floor, ceiling and walls.

Guess what?! The sheetrock wall behind the monitors - the slope ceiling totally shook on a low frequency, stimulated by the bass sound. When I put my hand on the wall, the whole ceiling was moving like there was an earthquake going on.

I then used my fist and slammed on the sheetrock the first time, to check what's going on - and a very strange sound came out. It sounded like you smash an empty oil can with the same metallic reverb.

Ok - major problem here. I won't be able to remove the wall and correct the inside.

After having a sleepless night, thinking about a solution, I came up with the idea to simply switch my monitoring position. Turn around to the other wall, away from this messy slopeceiling.

So done - here are the new positions I tested:

And the best position's frequency response looks like this:

In the meantime, I started to put some black cloth on the bass traps to make them look nicer. I also started to build some additional corner bass traps - I will make photo of them later

And now the most important thing - the waterfall diagram:

The 27Hz and 37Hz are muuuuch lower than than before, unfortunately here is a new mode at ~50Hz, but this can be treated later on.

Position finding

To find the best position of your speakers and your monitoring position in the room, the only thing to know which position is best is - measure, move, measure, move, measure move, ...

So I started moving the monitors closer, the listening position closer, and moved from the wall inside the room by steps of 10cm. Then moved the speakers further away and same back, and so on... I marked all positions on the floor and named the measurements in REW exactly the same, so after finding the best spot, I know where it has been ;-)

Since I am limited in the room with this massive brick bar from the wall, I only had about 15 possibilities for this side.

For the position finding, the most important thing is to have a constant frequency response over the whole spectrum, so you look at the frequency curve now, not at the waterfall diagram. (This will come back later).

You can also configure the measurement to just run a tone from 20Hz to 300Hz to speed up things.

After a long time and a lot of work, you will have a graph which looks like this:

Then you just unmark the color which has the hardest spikes in the graph, one by another, and in the end you will have the found "best" sounding position in means of frequency response. Which in my case was position #1 :-o

Then - let's check the waterfall again:

Very nice - you can see nearly all slopes higher 80Hz are gone, BUT the low frequencies from 25-50Hz are still brumpling. So I started to wonder whats going on and what is causing this response.

Build a monster basstrap

Bass energy is strongest near the walls. If you put some low frequency (lets say 90Hz) sinewave on your speakers, and walk around in the room, you will find spots where you can't hear any bass, or very low volume, and you will notice, if you walk near the walls, the bass will get very loud and strong.

So the best place to put the basstraps is in the corners, or not to "loose" a lot of place from the room, you also can put the basstraps under the ceiling next to the walls. That's what I decided for my room. I will build a big basstrap on the wjole lenght of the back wall under the ceiling.

So let's do it!

I built up some wooden frame and mounted it on the ceiling and the wall. Filled it upo with ROCKWOOL SONOROCK stoneweool and covered it with some plastic foil to keep the stonewool dust inside.

So let's see the result in the acoutsic behaviour of the room.

First the waterfall of the untreated room:

And here the waterfall with the monster bass trap on the ceiling:

(since I had to re-calibrate volume of mic and monitors, I dont have the same level in the diagrams, with make it hard to compare 1:1, but you see even if the level on the second picture is much higher, the slopes fall down and are treated very well, at least from 70Hz and above).

But the strange thing here is that this monster spikes at 27Hz and 37Hz are still there and don't even care about the basstrap. So the next big thing will be to find the best position in the room and check if this helps reducing the low frequency response of the room.

Room acoustics

You are now aware of my setup (if not, check my previous post about it) - it's time to measure the room.

First thing to get rid off is low frequency modes and reverb in the room. the REW software displays the reverb in a nice waterfall diagram - the most important frequencies to handle are 20-300Hz.

Here is the waterfall diagramm of my untreated room.

You can see some very big "mountains" in the very front of the waterfall at around 27Hz and 37Hz as well as a lot of spikes from 100Hz upwards.

This means -> BASSTRAPS! The only thing that helps here are some big, phatt basstraps. The biggerm the better. Since I am on low budget and I always was a "selfman", I will build some monstertraps in the corners to get rid of this wobbling frequencies in my room.

After some research and a lot of studying acoustic treatment forms, I decided to buy ROCKWOOL SONOROCK, nearly the best you can get to handle bass, and the price is acceptable.

So I bought some packs of the Stonewool (one pack is about EUR 25.-) and put them in the corners and in the back of the room on the floor to check the behaviour.

as you can see, it immediately showed in the waterfall diagramm how the slopes above 80Hz fall faster. But the very low modes at 27Hz and 37Hz are there, unimpressed :-(

The setup

SO in my first post I told you about the problems of my new room and that it's far from perfect, but I am optimisic and since it must not be the perfect room, but as good as possible treated, I will now start with checking acoustics and try to get rid of the biggest problems.


Here some pictures of the setup:

You can clearly see how the windows are not symmetrical in the room. My listening position is centered (left-right), and monitors are same distance from both side walls.

To measure room acoustics, I use a software called REW (Room EQ Wizard 5.0). You can get it free from http://www.hometheatershack.com/forums/downloads-area/19-downloads-page.html

The microphone I used is a Behringer ECM8000 . You can buy it from Amazon for about EUR 60.-
http://www.amazon.de/gp/product/B000HT4RSA

To learn more about how to setup the measuring environment and the software, please search google - there are a lot of guides out there.

The monitors you see are EVENT OPAL speakers, connected to a t.c. electronic desktop konnekt 6 firewire interface.

I put the monitors on some self made concrete bricks to keep vibrations as low as possible.

Ah yes - I already bought a curtain and mounted it next to the stairs.

The new room

First of all - I am not a professional studio designer. I had a lot of help from Bert4 fromtonstudio-forum.de - you can find the full thread here: http://www.tonstudio-forum.de/

I read a lot about acoustic treatment in blogs, forums and watched endless videos on youtube. So if you have any questions, most of them will be answered in my blog. If not, just hit me on facebook, twitter or throw your question in the comment here.

Ok .. so .. let's go :-)

My new studio room ... looking perfectly good ... or?

I recently moved to a new studio room. At first it looked great to me. After more than 10 years of music production I thought I know how to judge a room if it's good for making music or not. I was wrong. Deadly wrong. But first things first.

When I moved to the new house, i decided to put my studio upstairs in a small, nice room which looked perfect as studio. Big enough, low ceiling and cosy feeling.

Here are some pictures of the new room.

I was a little concerned about the roof sloping, but I searched about this in some forums and soon found out that this is not a problem because it could result in a better sound. Just put your speakers on this side of the room (facing the roof) and all is good.

Ok this was my first major problem. Rules say, always put your speaker on the smaller wall of the room, having the longer walls on the side. Impossible in my setup - roomfail #1

Second problem - room symmetry. One side is a small doorway (which is actually not used, but it's still there). Other side is a spiral staircase leading to the lower floor of the house. Also taking a closer look at the windows show that they are not centered in the room. roomfail #2

Here's also a layout of the room, so you understand it better. This is just a skizze and proportions are not right.

the blog is continued here. or you can choose from the menu on the top right if you want to read about a particular story.