I read in another thread that diffusors often don't work in small rooms because of the limited distance (< 2m) between the diffusor and the listening position. I expect to have 1.9m separation and I'd like to build a combo diffusor/trap. Will the combo diffusor/trap work to diffuse higher frequencies and absorb lower frequencies? Also, is 1.9m enough separation for the diffusor to work in my room?

I'm converting a 3.6m x 3.6m x 2.4m bedroom into a studio primarily for mixing and some 1-track at a time recording of vocals or individual instruments. Initially I'm thinking that the listening position will be centered about 1.4m off the front wall leaving it about 2.2m off the back wall. In addition to other trapping, I am considering a 1200mm x 1200mm weighted vinyl bass trap with a DIY skyline diffusor made using wood blocks over the top centered on the back wall behind the listening position. With the trap and the tallest block each being about 150mm tall, the listener would be about 1.9m from the top of the diffuser. Thanks.

Bill

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Slow but sloppy.

Quote BillPhillips:

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Will the combo diffusor/trap work to diffuse higher frequencies and absorb lower frequencies?

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Depends on the shape of the diffusor, the acoustic access to the absorber, and the depth and density of the absorber material.

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Also, is 1.9m enough separation for the diffusor to work in my room?

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Not really... but some forms of diffusor will work better than others. The 'binary amplitude' and 'skyline' types are claimed to work better than the more common QRS designs.

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I'm converting a 3.6m x 3.6m x 2.4m bedroom into a studio...

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With two identical dimensions, and the third being an integer factor, your main problem is going to be stacked standing waves. bass trapping will be far more important than diffusion, I suspect!

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I am considering a 1200mm x 1200mm weighted vinyl bass trap with a DIY skyline diffusor made using wood blocks over the top centered on the back wall behind the listening position. With the trap and the tallest block each being about 150mm tall, the listener would be about 1.9m from the top of the diffuser.

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I'd build the trap first and get the bottom end of the room sorted out as best you can before thinking about diffusion.

The aim is to get the most consistent balance of 'reverb' times across the spectrum. Diffusion is useful if the bassa trapping or midband absorption has sucked too much out of the reverb time at the high end, but it is difficult to predict in small rooms. So I'd try to deal with the bass absorption first, and then only think about adding diffusion when you know if its needed or not.

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Quote BillPhillips:

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Will the combo diffusor/trap work to diffuse higher frequencies and absorb lower frequencies?

---

Depends on the shape of the diffusor, the acoustic access to the absorber, and the depth and density of the absorber material.

Quote:

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Also, is 1.9m enough separation for the diffusor to work in my room?

---

Not really... but some forms of diffusor will work better than others. The 'binary amplitude' and 'skyline' types are claimed to work better than the more common QRS designs.

Quote:

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I'm converting a 3.6m x 3.6m x 2.4m bedroom into a studio...

---

With two identical dimensions, and the third being an integer factor, your main problem is going to be stacked standing waves. bass trapping will be far more important than diffusion, I suspect!

Quote:

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I am considering a 1200mm x 1200mm weighted vinyl bass trap with a DIY skyline diffusor made using wood blocks over the top centered on the back wall behind the listening position. With the trap and the tallest block each being about 150mm tall, the listener would be about 1.9m from the top of the diffuser.

---

I'd build the trap first and get the bottom end of the room sorted out as best you can before thinking about diffusion.

The aim is to get the most consistent balance of 'reverb' times across the spectrum. Diffusion is useful if the bassa trapping or midband absorption has sucked too much out of the reverb time at the high end, but it is difficult to predict in small rooms. So I'd try to deal with the bass absorption first, and then only think about adding diffusion when you know if its needed or not.

hugh

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I would second what Hugh is saying here as well

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David Shevyn General Manager GIK Acoustics Europe
www.gikacoustics.co.uk

Quadratic diffusion is a technology that does require proper distance from the diffusor surface to the listener. This distance is required because it takes distance to give the diffused energy waveform, if you will, time to fully form. A little more distance is required if one is using two dimensions of quadratic diffusion.

Due to your smaller space, I would consider sound redirection devices such as ones that have curved surfaces. They are commercially available and some have absorbing properties built in.

Focus on the low end first in your room. People do not know how much low frequency energy harms our musical presentation. Low frequency issues smother and blur major parts of our critical hearing bands and managing low frequency pressure issues is a must in any small room environment. If low frequency energy is properly managed in your room, notice I said managed, not controlled,it is almost impossible to control a 30 and 40' wavelength,your sound stage and imaging will have more focus and definition.

Next, deal with side wall reflections to assist with image centering and instrument and vocal separation. Use absorptive technologies that have a smooth rate of absorption. Acoustic foam technology will work well in side wall locations. Diffusion or sound redirection devices could be considered later for the rear wall.

Regards,
Mike

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www.acousticfields.com low frequency absorption solutions. Listen to the music without hearing the room!

Thank you all. Very helpful. As unanimously recommended, I'm going to focus on the bottom end for now. I'm planning to use a mineral loaded vinyl design similar to the one in this article [http://www.soundonsound.com/sos/mar06/articles/studiosos.htm] for the 1200mm x 1200 mm trap on the back wall. Does that sound like a good approach?

One potential problem with that plan is the back wall steps back about 600mm into a 1500mm wide closet directly behind the listening position. So 1/2 of the trap will be on the back wall and the other half will overhang the closet opening. The closet has sliding doors that I plan to remove leaving the opening. Would it be better to divide the trap into two 1200mm x 600mm pieces and put the second half on the back closet wall?


Thanks again.

Bill

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Slow but sloppy.