John Sayers' Recording Studio Design Forum Archive

Hi everyone! I run a small recording studio in Gävle/Sweden since about 2001. The gear has changed a lot over the years (of course) but the design has not. It was built in the 80's with a very dead live room and the control room is more or less completely untreated apart from my 10 GIK acoustic panels that I mounted a few years ago.

I just bought a pair of Genelec 8351B's and it was the tipping point for me to finally go down the rabbit hole of room measurement and acoustics. I have just spent a week with a couple of measuring microphones and REW learning how to measure, reading up online and trying some adjustments to my existing panels / speaker placement.

I'm going to spend this summer getting to grips with my control room, building or buying more treatment. Budget isn't big but I'm hoping 1000-1500 EUR might get me somewhere. Step one is understanding how and what to adjust, and what's going on in the current setup. As mentioned, REW and measuring is new to me but I've become obsessed with learning more. It looks to me like my room has a long decay in the bass frequencies and that should probably be the first thing to fix. I'm hoping that more skilled forum members could take a look at my data + pictures and perhaps help me understand what to do?

I don't own the property so I don't want to spend a lot of money on construction.

The 8351B's are now setup together with my old 7060B subwoofer, which doesn't have GLM/SAM, but so far it seems I get a much better response using the sub than not. Measuring is done in REW with a Sonarworks calibrated microphone. Measuring is also done after GLM has auto-adjusted the speakers.

I have measured the room in the current configuration as Left, Right, Left + Right, Sub, Left+Sub, Right+Sub, Left+Right+Sub.

I have also measured the response in the ceiling surrounding me to hopefully shine some light on where to focus my energy. Running pink noise through the sub shows highest SPL (perhaps no surprise) in the left front and back corners.

The room is a bit odd, it's like a smaller room connected to a slightly bigger room, with a wall taken down. My setup is in the middle of the small room, with the big room behind me.

Room measurements are very roughly:
Room 1 - 390cm x 437cm and 265cm high
Room 2 (behind me) - 430cm x 437cm and 375cm high

The 8351s are 110cm out from the front wall and the Left speaker has 165cm to the control room window on the left, the Right speaker has 140cm to the window on my right. So not symmetrical in the room, but more symmetrical to the room behind me.
Sub is on the floor as far up as it can go, half way to the left corner.

Before somebody spots it, I will say that step one is to swap places between the panels in the corners and the outer ones hanging from the front wall.

Here is a link to my REW file:
http://www.blackmon.se/rew/theoverlook.mdat

L=Left
R=Right
S=Sub

welcome! how much time have you spent adjusting the positions of the speakers and sub? you'll definitely see changes in the response as you move them closer to the wall (potentially reducing the SBIR there), and adjust the speaker height to ensure you're not putting the acoustic center into a null(er) spot. are the stands decoupled from the floor? and not touching the desk? its possible some of the higher readings are resonances.
are the right hand windows "lighter" than the live room windows? that would account for some of the LF differences as the lighter windows are effectively "trapping" LF by letting it through
the impulse spikes that are greater than -20db - back wall treatments will help there as well as attenuate more LF (presuming you'll build out a deep back wall). and those smaller walls on the joining between rooms - absorption over those will help.

i'd suggest start by finding the best speaker and sub location, given your desk and gear, and then sort out treatments from there.

Probably best to post the .mdat in a Dropbox or Googlebox or whatever. We often need to tweak the view parameters to tease out some little detail. Nice looking work space. More Cloud would take down the bright room decay without losing space. Lights can be above them, keeping your lovely aesthetic. Try your speakers almost touching the Front Wall. This might diminish your SBIR dip.

Probably best to post the .mdat in a Dropbox or Googlebox or whatever.

Thanks, I've uploaded the .mdat here:

http://www.blackmon.se/rew/theoverlook.mdat

welcome! how much time have you spent adjusting the positions of the speakers and sub? you'll definitely see changes in the response as you move them closer to the wall (potentially reducing the SBIR there), and adjust the speaker height to ensure you're not putting the acoustic center into a null(er) spot. are the stands decoupled from the floor? and not touching the desk? its possible some of the higher readings are resonances.

ry your speakers almost touching the Front Wall. This might diminish your SBIR dip.

Cheers guys! I did experiment with the proximity to the front wall but this was while I was still learning how to do measuring with REW, so I took some time today to re-evaluate this.

If I move my speakers right up against the wall, under the panels, I get a massive dip at 100Hz. But if I move a bit further out, just "in front" of the panels hanging in the ceiling, it looks better. I think this measures more flat than the original. Genelec recommend 1.1 metres minimum if you are using a 2.1 setup - which is why I had everything moved back before.

Setup 1 and 2 are in the .mdat file linked above. Setup 2 looks like this:

are the stands decoupled from the floor? and not touching the desk?

The stands are Genelec Z8000-409B floor stands but the monitors have Genelecs standard soft suspension feet. They are not touching the desk.

are the right hand windows "lighter" than the live room windows? that would account for some of the LF differences as the lighter windows are effectively "trapping" LF by letting it through

Interesting! Yes I would definitely think so... I thought it was weird how the right side has so much more bass issues but that makes sense.


Since most of my long decay is way down in the subs, what kind of panels should I build/buy? I'm guessing absorption panels will not be enough?

I'm hesitating building a deep back wall since I rent, but I guess it depends on the cost / effectiveness. How deep do you think they would need to be?

you could make some deep absorbers for the back wall so you can move them out later. make them open sided as 600x600x1200 (or whatever will fit under the ceiling in the space if you stack a a pair). start with say 8 stack into 4 pairs - 2 in the corners and 2 spaced between. you could make them full height but smaller makes moving easier. use 100mm semi-rigid on the front, optionally a layer of MLV behind it, then fill the rest with lightweight wall insulation. cover with cloth. i like to use a layer of chicken wire between sections to support the soft insulation.

can you adjust the monitor heights or are they fixed?

Good point! What density would you recommend for the insulation? Can it really help even down to 20-40Hz?

Most building suppliers here only rarely specify anything on their insulation but one thing they show sometimes is density... I've come to understand that "flow resistivity" does not translate linearly to density? I did find the Acoustic Modelling website but it's all in flow resistivity.


The stands adjust in slots of about 5cm. I tried measuring different heights in the last position but will have to try this again with the new setup.

GFR varies greatly across products and even manufacturing of the same products in different regions. so my thinking is - GFR is important to the degree you can specify exactly what you want and actually obtain it where you need it and within budget.

so density and thickness for known brands is often close enough in most cases. so 15-25Kg/m3 wall insulation products will all work as the soft insulation. and if you add a soft membrane of MLV (say 8-10Kg/m2) behind the semi-rigid (say 60-80Kg/m3), it improves the attenuation in the open sided units.

nothing is stopping 20hz without being a large pressure trap, hangers, or really deep absorption. or all of the above.

Thank you! I will look into finding the best option for material and definitely look into building some big absorbers.
Can't seem to find MLV in Sweden but if it's optional then I might have to build without it.

I'm also thinking panels across the corners on the short "side walls" that divide the control room half of the room with the other half. They can't be too thick though, should I build those with lightweight too? Could Helmholtz absorbers work?


Another thought that hit me after playing with the Amroc calculator online is that the "Bolt-area" looks a lot better if I cut down the length of the room where the (ironically) old wall used to be between the two sections of the room.

Could it be a good spot to setup those big bass traps, rather than the back of the room?

the MLV is a nice to have. the short walls - i would make them 100mm absorbers and if you have a ceiling drop there (e.g. a joist spanning) i'd cover that as well.

i wouldn't reduce the size of the room. and you can add more absorption units in the back if you find you need them.