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Author Topic: Basic treatment for a poor recording space?  (Read 3719 times)

maccool

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Basic treatment for a poor recording space?
« on: May 29, 2009, 07:11:38 pm »

I've been mulling this over now for too long, time to fish or cut bait!

The only place I have to record in is the one I've got! So I have to make the best of it, and I need sound advice. Pun intended.

It could be a worse space, but not by much I think.

It is a wooden structure on a concrete pad, 6.0m x 4.60m x 2.32m. It has 90mm stud walls, shiplap outside, 9mm hardwood ply inside, with glassfibre thermal insulation.

The intended primary use is for the recording of acoustic music.  If I can get that part of the acoustic treatment as good as I can, I'll be happy.  Any considerations for mixing are secondary at this point, although not completely out of mind.

My research so far suggests that I need broadband absorbers on the walls, bass traps in the corners, and a broadband cloud above the performer.

But, how much?

Which brings me to my second question;  can somebody please guide me through the process of making an acoustical analysis of the space before I undertake any changes?

I would like to understand that process and measure the effects of any treatment as I go along.  Suggestions for Mac software would be appreciated.  I'm just looking at FuzzMeasure, don't know how it measures up though!

Corning 703 is hard to find and expensive in the UK, so I propose to use Rockwool for the absorbers and traps.

I realise that this room isn't ever going to sound wonderful, but I believe I can go some way to mitigating the sonic damage it wreaks on a good acoustic guitar, and that really is the focus of my efforts.

I just discovered SketchUp, so I've made a jpg which shows the layout, and I've added absorbers and traps according to what little knowledge I have.

The blue panels are 1200x600x50mm and hung away from the walls.

The red panels are 1200x300x100mm, except for the cloud which is1200x1800x100 and suspended below the ceiling.

I've omitted the doors, windows, and ceiling for clarity, but they're there!

I hope I'm on the right track.  Any help whatsoever would be greatly appreciated.

Dave.


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Ethan Winer

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Re: Basic treatment for a poor recording space?
« Reply #1 on: May 30, 2009, 11:59:11 am »

maccool wrote on Fri, 29 May 2009 19:11

But, how much?


With bass trapping, you can never have too much. The layout you show looks very good, but the red bass trap in the front left corner looks too narrow assuming it's to scale.

Quote:

I'm just looking at FuzzMeasure, don't know how it measures up though!


FuzzMeasure is excellent.

--Ethan

maccool

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Re: Basic treatment for a poor recording space?
« Reply #2 on: May 30, 2009, 03:08:20 pm »

Thank you Ethan.  Most of my meagre knowledge I have gleaned from your excellent articles and posts.

Ethan Winer wrote on Sat, 30 May 2009 16:59

...The layout you show looks very good, but the red bass trap in the front left corner looks too narrow assuming it's to scale...


It is indeed to scale. I figured it was too skinny when I made the picture like that, but I thought I had to start somewhere.

Those panels are only 300mm wide and 100mm deep.  I'm thinking the 100mm deep is ok, but how wide do you think they should be?  600mm like the wall panels?  And the same for the wall/ceiling corners?

If "yes", then I reckon I have a plan Smile

So, can I push my luck a bit further and ask what methodology you'd use to analyse the space with a tool like FuzzMeasure?

While I think I understand in a very basic way what it is I'll be measuring, I'd be silly to try and re-invent the wheel if there are commonly accepted practices for doing this.  I have made some efforts to discover any such methods, but without any luck.

This is the point where I'd like to reiterate that I'm trying to make this the best possible silk purse out of a sow's ear of a recording space.

That said, I think what I'm chasing here is a method for measuring the acoustic characteristics of the room at several places, and thereby see what I have to start with, and to gauge any improvements the treatment provides.

Without doubt, the final arbiters of where to place performer and transducer must be my ears, but that task ought to be a whole lot easier and more rewarding if I had a clear understanding of what is fundamentally wrong with the space to begin with and the extent to which the acoustic treatment might have mitigated those problems.


Left to my own devices and not knowing $h*t from Shinola about this analysis process, I'd measure the room's response with a tool like FuzzMeasure, one speaker, and one omni mic. I'd make measurements of a cubic matrix, 9 positions at 1 metre apart on a 3x3 horizontal grid, repeated at 3 vertical levels corresponding to the average heights of a guitar soundboard played seated, ditto played standing, and the height of a violin played standing.

But where should I place the speaker? Does it matter?

That's a lot of work!  Am I over-thinking this?
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jimmyjazz

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Re: Basic treatment for a poor recording space?
« Reply #3 on: May 30, 2009, 09:02:25 pm »

Ethan Winer wrote on Sat, 30 May 2009 10:59

With bass trapping, you can never have too much.


While I have the academic background, I don't make my daily bread in acoustics.  However, I am an engineer, and it always makes me recoil when I see stated absolutes such as Ethan's above.  The real world is rarely so black and white.

Ethan, you have been positioning yourself as an expert in the field for years now.  I think it's fair to ask -- can you cite any peer-reviewed journal articles or other legitimate references that might back up claims like yours above?
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Ethan Winer

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Re: Basic treatment for a poor recording space?
« Reply #4 on: May 31, 2009, 02:10:58 pm »

maccool wrote on Sat, 30 May 2009 15:08

I'm thinking the 100mm deep is ok, but how wide do you think they should be?  600mm like the wall panels?  And the same for the wall/ceiling corners?


The wider the better. Yes, 2 feet wide is a good minimum.

Quote:

what methodology you'd use to analyse the space with a tool like FuzzMeasure?


The main two tools are frequency response and ringing which you assess with a waterfall plot.

Quote:

But where should I place the speaker? Does it matter?


I don't test live rooms much, so others may have better opinions. But I'd put the speaker near one corner and the microphone near the other. That excites all of the modes, and also lets the microphone pick up the most "room tone" by being farther away.

--Ethan

Ethan Winer

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Re: Basic treatment for a poor recording space?
« Reply #5 on: May 31, 2009, 02:22:08 pm »

jimmyjazz wrote on Sat, 30 May 2009 21:02

can you cite any peer-reviewed journal articles or other legitimate references that might back up claims like yours above?


I can offer some basic logic and common sense. But first let me be clear that I'm talking about mostly about smaller mixing and listening rooms rather than live rooms.

In a small mix room you'll never get the response perfectly flat with no ringing. So the best you can aim for is close to flat and minimal ringing. I've measured rooms to see what happens as more and more traps are added, and even when the entire room is full of traps the response is still not perfect. So then it comes down to how close to perfect you hope to get. One can certainly get great results in a bedroom size control room with eight corner bass traps plus absorbers at the reflection points. But adding more traps can only make the response and ringing even better.

A live room is a different story, but again my main focus is on smaller rooms. Small untreated rooms always sound small and boxy. The bass response is always terrible too. So again, it's a matter of how good you want. The smaller the room, the more you have to reduce the reflections to avoid that small-room sound.

One final comment about "peer review" is that small-room acoustics is constantly evolving. If new ideas were not put forth and tested, we'd never progress. I try to avoid "argument from authority" and rely instead on measurements and of course listening. Just yesterday I did a test of a 16 by 11 by 8 foot room, first empty and then totally filled with bass traps and diffusors. Guess which sounded better? I'll have an article up soon describing the setup, and also offer audible examples of music recorded through the speakers empty and treated. Then you'll be able to decide for yourself.

--Ethan

jimmyjazz

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Re: Basic treatment for a poor recording space?
« Reply #6 on: June 02, 2009, 10:37:49 pm »

Well, it helps when you clarify your response as you did regarding small rooms, mix rooms, etc.  I still find generalizations risky, as (almost) every time I have tried to generalize in my areas of expertise, Mother Nature has stepped up and slapped me back to reality.

The devil is truly in the details.
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Ethan Winer

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Re: Basic treatment for a poor recording space?
« Reply #7 on: June 03, 2009, 02:38:05 pm »

jimmyjazz wrote on Tue, 02 June 2009 22:37

I still find generalizations risky


Yes, and I admit that's one of my failings. Laughing

But often people ask questions without giving enough detail, so all we can do is offer general advice. Also, the idea that one cannot have too much bass trapping in a small room doesn't come only from me. I'm pretty sure Fran feels the same way, and I'm certain that everyone else who sells bass traps agrees. Okay, just kidding. (No I'm not.) But still...

Very Happy Very Happy

--Ethan

jimmyjazz

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Re: Basic treatment for a poor recording space?
« Reply #8 on: June 04, 2009, 10:51:39 am »

I appreciate the good attitude, Ethan.
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Thomas Jouanjean

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Re: Basic treatment for a poor recording space?
« Reply #9 on: June 05, 2009, 03:08:30 am »

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maccool

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Re: Basic treatment for a poor recording space?
« Reply #10 on: September 16, 2009, 07:09:45 pm »

Thanks to everyone for commenting.

I have finally managed to start treating my room.

For starters, I have 12 4'x2'x4" panels.  I may add a few more, but this will get me going for now.

The most pronounced effect so far has been the installation of a cloud over where I sit to play acoustic guitar.  A palpable hit!

Now I have a question about corner traps.

The cloud and some wall panels most definitely improves the situation, but does not eliminate the 220Hz problem with the guitars.

So, next step is to build some corner traps.  

The idea I have in mind is to use the Rocksilk slabs cut into triangles stacked on shelves in the corners and then faced with fabric.

My question is, how wide, and would having the corner filled be more or less efficient than having it enclosed by a 4" deep panel with an airspace behind it in the corner?

The question about how wide..... If I do fill the corner with stacked triangles cut from 4'x2' slabs, I can make it 2' across the face, or 2'10".
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Ethan Winer

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Re: Basic treatment for a poor recording space?
« Reply #11 on: September 17, 2009, 10:47:51 am »

^^^ A filled corner is better than a 4-inch panel, but not proportionally based on the amount of material used. So if you're limited by budget, having more panels is better than fewer filled corners. As for width, the wider the better.

--Ethan
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