Advice on room treatment - classical/acoustic guitar

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Michael440

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Hi everyone,

I'm a musician living in Switzerland, playing classical and acoustic guitar. Recently I moved my teaching/recording studio to a new room.

It's a 25 m2 room on the basement floor, with 5.7m long, 4.5m wide and 2.2m high. The area is very quiet so no need to isolate noise from outside.

As it is now, the room has far too much unwanted reverb, and I wish to start treating it with some diy. I was thinking to build some acoustic panels and bass traps, and place a thick molton along the walls. My question is how do I plan the project and decide on the type, quantity and size of panels (or any other solution)?

Thanks a lot in advance for any advice or reference for online tools. I'll be grateful to know where you would recommend to buy materials in Germany/France - Switzerland isn't the place to buy anything.

Thanks again!
Michael
 
How serious of a classical guitar player are you?

Here’s a sample of me playing my classical.



It’s recorded with an SDC about 6 inches away. No room treatment. No EQ, No compression or anything. Just reverb. If you’re not a serious player, you won’t need serious room treatment to get a good sound, and I would just save your money. Just some carpeting and other pieces of furniture to deaden the reverb will be enough. If you are a serious player (and Im talking about student who has been trained/Grisha Goryachev level of play), then you’re on the right track and I will let others comment here regarding treatment. You’ll definitely want rock wool, though.
 
This is a strange response? The ability of the player is surely irrelevant? The ability as a listener is the critical element here. If the room has hardm parallel wals, and parallel hard floor and ceiling, then it's live - and at those dimensions it's probably quite boxy sounding. Realistically, you need to analyse what it sounds like now when you play music in it. Real music from your guitar and audio tracks you know well. It's also quite revealing to play a 20-20KHz sweep tone - (youtube have lots) it starts low and as it rises, do some frequencies suddenly jump out at you. If you can record the sweep and look at in on software in a DAW, for example - you'll build up a picture of where your issues are. So you might discover certain things that really are wild! They'll wreck listening and make your mixes sound very odd on other people's systems as you will be making adjustments based on your rooms strange behaviour. If you are lucky (and I doubt it, to be honest) - then if all your issues are high - then some absorption will sort it out nicely. If you have specific nastiness in the low end, then bass traps of some kind. You can make them or buy them. Soft furnishings and heavy carpet or rug will tidy the top, but wonky bass needs working on. If you are in no hurry, once you've analysed the space - buy a modest amount of treatment and start experimenting. Once you hear improvements, you can add more. At some point, more stop being effective. At this point, most people call it quits. Absorbers, reflectors and diffusers are your main purchase areas.
 
rob aylestone said:
This is a strange response? The ability of the player is surely irrelevant? The ability as a listener is the critical element here. If the room has hardm parallel wals, and parallel hard floor and ceiling, then it's live - and at those dimensions it's probably quite boxy sounding. Realistically, you need to analyse what it sounds like now when you play music in it. Real music from your guitar and audio tracks you know well. It's also quite revealing to play a 20-20KHz sweep tone - (youtube have lots) it starts low and as it rises, do some frequencies suddenly jump out at you. If you can record the sweep and look at in on software in a DAW, for example - you'll build up a picture of where your issues are. So you might discover certain things that really are wild! They'll wreck listening and make your mixes sound very odd on other people's systems as you will be making adjustments based on your rooms strange behaviour. If you are lucky (and I doubt it, to be honest) - then if all your issues are high - then some absorption will sort it out nicely. If you have specific nastiness in the low end, then bass traps of some kind. You can make them or buy them. Soft furnishings and heavy carpet or rug will tidy the top, but wonky bass needs working on. If you are in no hurry, once you've analysed the space - buy a modest amount of treatment and start experimenting. Once you hear improvements, you can add more. At some point, more stop being effective. At this point, most people call it quits. Absorbers, reflectors and diffusers are your main purchase areas.
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Serious classical / flamenco players have very strict standards of intonation (when it comes to the guitar), tone (when it comes to the guitar and their playing), and overall sound (when it comes to the guitar, their playing, and the room). Like, really strict. My response is basically summed to this: if you’re not super serious about it, you can still get a GREAT sound without treatment and there’s no need to waste time and money on treatment when it’s already good enough. It’s like telling a home recorder that there’s no need to spend money on a Neumann mic when an MXL is good enough, and I honestly don’t find that strange at all.

is the room furnished? All we know is that it has too much reverb “as it is now.”
 
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Interesting? What I was referring to was this bit....
If you’re not a serious player, you won’t need serious room treatment to get a good sound,
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Any level of musicianship benefits from decent acoustics, in my very humble view. I worked with a classical guitarist who was having a guitar built, and the tone was so good when he tested it, he refused to let the Luthier seal the surface or stain or varnish it, as it would spoil the tone!
 
Thank you for the fast replies!
Yes, I'm THAT kind of a guitarist... and my concert guitar is also left without varnish for this reason :)
I'm very aware that the room I rent is nowhere near a recording studio, but on the other hand it's not where I'll be producing my commecrial CD (more like short demos and videos to publish). I will be using RME and a pair of Neumanns, so it would make sense to have a bit of treatment to the room. I'm interested in working by the 20/80 rule and making the few changes that will contribute the most.
So far my idea is to build bass traps for the corners, and make them from rock wool and a wooden frame. Not triangles, but flat and thick enough, with the wood cut to match the corners' shape. The idea of recording 20-20k sinus wave and watch it is great, thank you! I'll do this in the weekend.
 
Michael440 said:
Thank you for the fast replies!
Yes, I'm THAT kind of a guitarist... and my concert guitar is also left without varnish for this reason :)
I'm very aware that the room I rent is nowhere near a recording studio, but on the other hand it's not where I'll be producing my commecrial CD (more like short demos and videos to publish). I will be using RME and a pair of Neumanns, so it would make sense to have a bit of treatment to the room. I'm interested in working by the 20/80 rule and making the few changes that will contribute the most.
So far my idea is to build bass traps for the corners, and make them from rock wool and a wooden frame. Not triangles, but flat and thick enough, with the wood cut to match the corners' shape. The idea of recording 20-20k sinus wave and watch it is great, thank you! I'll do this in the weekend.
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Cool deal! You might want to look into diffusion, too, rather than JUST absorption.
 
I have a question about bass traps in the corners. I plan to make them with rock wool, and I see that there are soft pieces and rigid ones. At first I thought that it's necessary to build a wooden frame for the soft wool, but it looks like I can have a large piece coated with either foam or fabric, and then hang it from the ceiling like a heavy curtain - it would simply stay flat in its place. Googling about this didn't bring any info. Am I missing anything?
 
The 'softer' one, like Roxul vs OX703, is not as dense, so the absorptionis not as great. You may also find the soft one sags over time if not in a frame.
 
mjbphotos said:
The 'softer' one, like Roxul vs OX703, is not as dense, so the absorptionis not as great.
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The problem with this statement is that it is a half truth. Here is the absorption coefficient chart for 703. For thin treatments 4 inches and under, this statement is accurate, sort of. It is more absorptive than lighter density at depths of 4 inches or less but not very effective at low frequencies at these depths. At thicker depths bass absorption properties diminish and the more rigid 703 becomes reflective at lower frequencies rather than absorptive. This would be the opposite of what you'd want for deep bass traps. People look at this chart and tend to extrapolate that if they go thicker, they will get better bass absorption. Not the case at all however. Also keep in mind that .7 is only about 3db reduction further reduced by the ratio of the percentage of coverage. So .51 SAC for 4 inches at 125Hz is not what anyone would call effective for bass treatment. For corner bass traps, 703 is not the more effective material to use. Lower density materials absorb lower at depths over 6 inches vs higher density. 703 absorption properties fall off a cliff at 250Hz and going thicker won't improve its absorptive properties.

Screen Shot 05-16-21 at 06.49 AM.webp
 
Rockwool always sags - the soft stuff just more quickly, Horizontal slabs sag pretty quickly - I suspect it's vibration that does it.
 
rob aylestone said:
Rockwool always sags - the soft stuff just more quickly, Horizontal slabs sag pretty quickly - I suspect it's vibration that does it.
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Easy problem to solve using staples and string to add staggered supports horizontally within your frame. Some use wire mesh.
 
square mesh is pretty tough yet light enough to staple then cover. You can sew it in a few places to keep the fabric attached to the timber and of course use glue for the final cover and wrap. We have a few fabric warehouses - where the material is for curtains and sofas - they do some nice thicker products and often have offcuts.
 
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