# Acoutic treatment of home mixing room - before and after (graphs inside)



## sparky5 (Sep 28, 2009)

Hi All,

I have posted two fairly random threads latley regarding acoustically treating my small home studio / mixing room / listening room. Well I have not treated the room (with results I am pretty happy with) and thought I would provide a description of the before and after, and what I did to give back a little to the great community here.

Well, I purchased some bass trap bags from www.readyacoustics.com, and some appropriate acoustic batts. I live in Australia, and it is hard to find the Owens Corning here so I used a product called 'SonoBatt Silencer +'. It's attenuation properties are as follows:

For 100mm batts (I used the 50mm but doubled them up):

125hz - 0.54
250hz - 1.11
500hz - 1.23
1000hz - 1.12
2000hz - 1.02
NRC - 1.10

My room is roughly 340cm long, 280cm wide, and 240cm high. It is SMALL.

I made up 8 traps in total that are roughly 48" x 24" x 4" (that is the size of the ready acoustics bags. My batts were a bit smaller so I had to cut some extra pieces to fill the bag out lengthways but did not fill the bags out breadthways if that makes sense. They still look 90% as good as the real deal).

I drew a very crude picture of where I placed the bass traps, one at a time while I measured things and adjusted the batts to better positions. The batts in the corners are against the ceiling. I also had batts against the gorund corner as well, but the graphs were better without them so I used them elsewhere to good effect. Go figure. The blue boxes are the monitor speakers, which are behringer truth B2030A which I actually really like - go ahead and bach behringer if you feel the need  The batt on the left wall (or on the wardrobe door actually) is to treat early reflections. The heavy curtain seems to also do a moderate job of that. Anyway here is the picture of the room setup:









All testing was done at 75db measured by a Radio Shack SPL meter, and all readings taken with a Behringer ECM8000 with appropriate calibration file loaded. 

The first graph is of the room before any treatment. Sorry about the target line in the first graph - it should have been set to 'Bass Limited' (as I have no sub) like the rest of the graphs. Doesn't change any of the measurements, just looks weird against the rest of the graphs  :









And here is the associated waterfall graph for the untreated room:









So as you can see, was not really great.

The next graph is the room after full treatment. This is actually an average of 4 measurements which were very, very similar. It was strange, occasionally I would get a measurement that was really different and did not fit the mold of the majority. I am not sure why (but would love to know):









And below is a number of waterfall graphs for the treated room. Again, each one is a bit different, not sure why as everything else was kept the same and they were fired off one after the other:

























So, things are looking a lot better. There are still a few (large) peaks and nulls, but I have not managed to get rid of them. I would really like suggestions from people on how I might go about this.

Here are some smoothed graphs before:









And then after just cause I had them:









So there you have it. I am still contemplating if I should add any more treatment to the walls for reflections e.t.c. but the room is already feeling really small. I can't reasonably fit any more bass trapping in, and my girlfriend is already mad enough about how it looks and the holes all over the place :nono:

Hopefully this information might be useful to someone regarding what is possible in a studio / mixing room context on a budget using budget gear. Most of the discussion on this forum is for Home Theater Rooms (which makes total sense given what the forum is for) but I thought this might be of interest.

I would be really interested in any feedback on the graphs anyone more in the know can provide me.

Thanks a lot,

VidarAus


Also - the are two graphs in the attachments below, the first being for the untreated room and the second for the treated room. They are 1/3 Octave Smoothed graphs focussing on the lower frequencies.


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## bpape (Sep 14, 2006)

The 2 places I could see helping a bit more are:

Directly beside the monitors for SBIR purposes.

Centered on the rear wall to help with cancellations off the back.

You may also find that changing seating position forward and back will change the response in the bottom end to your advantage.

If you really want to see what's happening, run the sweep, set the graph from 20-300Hz and don't use any smoothing at all.

Bryan


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## MatrixDweller (Jul 24, 2007)

That pretty neat. The after graphs do look a lot cleaner than the before ones. I'm not an expert and am just about to treat my room. I've been doing a bit of research before I take the plunge.

I'd be guessing that the dip at around 105 and 210Hz and peaks at 65 and 130Hz are due to your room modes coming into play (see how they are multiples of each other). I think the ways to get rid of them are through EQ or tuned absorption (ie: a Helmholtz resonator) or diffusion. 

That's just my opinion from what I've read on the net so by all mean jump in and correct me if I am wrong (I want to learn too).


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