Acoustic treatment inside volcanic rock walls

MapacheAcuatico

New member
Hello there. I know this is probably a pretty unusual thread. I couldn't find much information on this topic. I'm starting to build a recording space in my sister's basement and I plan to treat acoustics and to have a semi-professional set-up. I'm pretty set on getting a pair of LP8's (I'm open if you have other recommendations) and I got a new computer on the way, but my main question is:

The walls are made entirely of volcanic rock and cement, and the dimensions of the room are 4.7M X 3.7M X 2.3M(H). I'm pretty new to acoustic treatment. I got a big, thick rug on the floor (I also have spare blankets that I figure I could hang) and I'm planning on making bass traps and acoustic panels (would also love some advice on your favourite materials for this). However, I'm wondering if these walls have to be treated differently? Or if perhaps they reduce reflections already to some degree due to the inconsistency of the texture? Any advice would be appreciated!
 

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Orson

Well-known member
Is it a stone built building with outside walls or underground? In other words what is on other side of those walls?
 

LazerBeakShiek

AKA Optimus Prime LEGO Vampire
Two words. Man cave. Man, you could be a supervillian. Planning the worlds' destruction in a dormant volcano. Totally jealous.
 

mjbphotos

What?!?
Stone and cement will reflect soundwaves. That's not a big space, so start with the corner traps (rockwool or compressed fiberglass, not foam), trhen go form there. There shoudl be acoustic treatment at point-of-first-reflection on either side wall, plus a ceiling 'cloud' above the mix position.

Assume you mean Kali Audio LP-8 monitors, good low budget option.
 

MapacheAcuatico

New member
Stone and cement will reflect soundwaves. That's not a big space, so start with the corner traps (rockwool or compressed fiberglass, not foam), trhen go form there. There shoudl be acoustic treatment at point-of-first-reflection on either side wall, plus a ceiling 'cloud' above the mix position.

Assume you mean Kali Audio LP-8 monitors, good low budget option.

Thanks for your response. I was considering building two bass traps for the opposite corners, with rock wool like you suggested, do you think 30cm × 30cm is large enough? (From floor to ceiling). And then I had in mind making 4 inch thick sound panels (made out of rock wool or equivalent) for the walls and for the ceiling. I had in mind putting up 10 along the walls and 4 or 5 on the ceiling, but is that overkill?


Edit: sorry for the triple post btw. I'm beginning to think that it would be more reasonable to have 7 sound panels along the walls and perhaps more like 3 clouds (+2 bass traps of course). Hope you guys can give me some feedback on that
 
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Farview

Well-known member
That isn't going to be overkill. The smaller the space, the more sound panels and bass trapping you need. That space is going to be really reflective, it will take a bit to tame it.
 

Orson

Well-known member
It's underground and the walls are rock and cement all around. The ceiling and floor are cement. Sound isolation is not bad already.
So I imagine right next to the outside walls is earth/soil?

Then if that is the case you may first need to stop any damp penetration through the walls. This will mean a polythene damp course liner applied to the walls first, then you will need to build a 4x2 interior frame completely around the room next to the damp liner.

So you are basically building a room within a room but with a waterproof plastic liner in between.

If you do not do this, any damp passing through these walls and/or condensation because the walls will be cold, will be soaked up by the insulation, which will be then just a soggy mess, become ineffective, collapse and very quickly rot any timber you have there.

So your interior timber wall and insulation has to be isolated from those stone walls and the stone walls have to be sealed behind that plastic membrane.

Estimate to lose 150mm/6" on each wall. So your room dimensions may be 4.4m x 3.4.

If you do not plan to go down the road of making a full studio down there and just want a room with sound treatment to lessen the reflections. I would seriously think about investing in a very good dehumidifier, because the moisture is going to really build up and this wont do your equipment any good.
 
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Orson

Well-known member
Volcanic rock can be a varied mix of rocks from the pumice stone type you see on gas bbq's to anything more solid. All have differing water penetrable qualities.
 

rob aylestone

Well-known member
If the walls are not for keeping sound in or sound out, I'd love to deal with them. I'm fed up with sheet based walls. The secret will be the time to experiment. Get it finished and working, then play and record some music and see what happens - then start the sound treatment as you need it. If you have too much or too little of anything, add the absorbers, traps and control.
 

MapacheAcuatico

New member
Thanks bluesfordan! I live in Tepoztlán, Mexico.

Thank you for your insight and recommendation Orson, I think that's going to be a major factor sooner or later. The rain here gets absolutely insane so I'm definitely fearful of humidity. I'm lucky the the dry season has arrived and we won't expect rain whatsoever for several months. I'm not sure if my budget allows for building the walls within the room right now, but perhaps I can start like this, I'll get an estimate on the cost of materials to build walls all around, and push through like this until the rainy season is on the horizon again, and then contemplate building protective walls. I have borrowed a humidifier that has been running nonstop for 3 weeks, and it's wild how quickly it fills up.
 

MapacheAcuatico

New member
If the walls are not for keeping sound in or sound out, I'd love to deal with them. I'm fed up with sheet based walls. The secret will be the time to experiment. Get it finished and working, then play and record some music and see what happens - then start the sound treatment as you need it. If you have too much or too little of anything, add the absorbers, traps and control.
I'm a little bit confused by your post. these walls are a novelty and interesting to work with? That's interesting. I guess it would be interesting to record without treatment to see how it sounds
 

Orson

Well-known member
Thanks bluesfordan! I live in Tepoztlán, Mexico.

Thank you for your insight and recommendation Orson, I think that's going to be a major factor sooner or later. The rain here gets absolutely insane so I'm definitely fearful of humidity. I'm lucky the the dry season has arrived and we won't expect rain whatsoever for several months. I'm not sure if my budget allows for building the walls within the room right now, but perhaps I can start like this, I'll get an estimate on the cost of materials to build walls all around, and push through like this until the rainy season is on the horizon again, and then contemplate building protective walls. I have borrowed a humidifier that has been running nonstop for 3 weeks, and it's wild how quickly it fills up.
The humidifier filling up can only fill up if the moisture is there. So there you go.

I live in Ireland and know all about stone walls and damp.

Stone walls look great because they give us that feel of old. Stone was used in those days because it was free, usually a by product of removing stone or rock from the fields to grow crops. If you knew how to use it, then you could build some fine buildings with it........and they did.

The trouble with a lot of stone is that it doesnt have the water repellent properties of fired brick. So the stone if at ground level absorbs moisture and because of it's imperfections, it lets moisture through and in to it. It looks great but water/moisture/damp wise it is not good.

Then in your case you stick it underground buried in wet soil and then enclose it with no ventilation...........and you may have an impending disaster with delicate electrical equipment.

If either the room smells musty, or it feels damp and condensation forms on those walls then you have a bit of a problem.

If the dehumidifier is taking that much water out of that room, you may be better growing mushrooms.
 

Orson

Well-known member
Thanks bluesfordan! I live in Tepoztlán, Mexico.

Thank you for your insight and recommendation Orson, I think that's going to be a major factor sooner or later. The rain here gets absolutely insane so I'm definitely fearful of humidity. I'm lucky the the dry season has arrived and we won't expect rain whatsoever for several months. I'm not sure if my budget allows for building the walls within the room right now, but perhaps I can start like this, I'll get an estimate on the cost of materials to build walls all around, and push through like this until the rainy season is on the horizon again, and then contemplate building protective walls. I have borrowed a humidifier that has been running nonstop for 3 weeks, and it's wild how quickly it fills up.
This happening may not mean the room is drying out. It could mean that there is a moisture/water trap behind those walls and you may be just drawing the water through the walls. If the room is actually drying out then the dehumidifier will collect less and less water. After 3 weeks of continuous running, it should be dry by now.
 

mjbphotos

What?!?
My old house (the ex has it now) had a stone foundation. "Damp" doesn't describe it. It never fully dried down there, opening up bulkhead, windows, running fans (when it was dry outside) was the only solution. Even during humid summer days with everything closed up, it would get bad down there.
 
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