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How I got pretty good sound from three absorbers
Old 28th October 2017
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How I got pretty good sound from three absorbers

My room is about 30'x14'x8'. It has a dropped ceiling, and the floor is carpeted. I was astounded by the difference just three DIY Roxul-based absorbers made. (OK, four if you include the blanket I lay on the desk during mixing to absorb high frequencies)

This was based on help from this forum and reading a lot of advice kindly provided online by various treatment experts. So I'm returning the favor by posting my experience. I do not have before and after scans - sorry.

I don't want to seem to tell anyone "Do this", but here's what worked so well for me:

1. I placed the desk so that when I'm sitting at it, my ears would be at the 'golden rule' distances. (Yes, I know, not really a rule, just a good starting point. Well it worked out ok for me) Obviously centered in the room from side to side. Actually, the golden rule wants you to be 40% from the wall in front of you, preferably. But for practical reasons I went for the second best 40% from the rear wall. (And if you want to get picky, it's supposed to be 38% and 62%. I didn't find 6" one way or the other made a difference.)

2. I even applied the golden rule to height. This was mostly to avoid the sinful 50/50 level, and going up to 40% seemed more practicable than going down to 60%.

3. Then I placed my monitors at the corners of my desk, so that they formed an equilateral triangle with my ears. I suppose the point of the triangle at my head is somewhere inside my head. Don't get caught up in millimeters. You'll never sit at the exact same position to within millimeters anyway.

4. I made sure the mid-point between tweeter cone and woofer cone was at the same horizontal level as my ears. Same thing, give or take a bit.

5. Using the famous 'mirror trick', I found the points on the side walls where first reflections from both monitors would reflect from. Then placed a DIY absorber centered on that spot. The DIY abosrber is 3 1/2" thick Roxul Safe n' Sound, two thicknesses, and two widths - so making an absorber 6" thick, and 48" x 32". That is wrapped in a large garbage bag to contain the fibers. There are endless online discussions on whether this is necessary or not. On top that, in the frame, I put a layer of quilting to absorb the high frequencies the plastic bag might reflect. Hang or stand it all centered on the middle of the reflection points, and spaced off the wall a few inches.

6. They're centered vertically on the listening height

7. Then I added a cloud - same thing, find the reflection point on the ceiling, make a DIY absorber - this one was just one layer of Roxul thick, but also had the quilting on front - hang it up. I put mine at a slight angle, just 'cause I read somewhere it helps.

And that's all I've one. I was amazed at how everything above the low bass tightened up. I got this amazing spacial imaging from good stereo mixes. Very clear. I sit non-musician people down at the listening position and they are blown away by the 3-dimensional sound stage, the clarity, the separation.

I have been procrastinating about treating the bass for a long time, and I know I have bass issues. This treatment will not fix that.

The only other thing I did - and the only other product I'll plug in this thread - I added a pair of Iso Acoustics monitor stands. Was wary I was wasting money, but got a really good surprise when it made a seriously positive difference - to my ear anyway.

Oh yeah, and I lay a blanket on the mixing desk during mixing for any high frequency funny business from desk reflections. The difference this makes is pretty minimal, but every little bit helps.

I also found that moving slightly forward or back at the listening position makes subtle differences. Just a little farther away, and I have a reasonably nice stereo image. But move forward a bit, so my head's just inside the triangle, and suddenly the monitors disappear - the music is just there, in the air - it's magic.

Last edited by musicus; 28th October 2017 at 10:12 PM..
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