Budget soundproofing one wall with only the rest of the house's peace in mind

[ralphus]

(Yes, another one of these threads...)

I will soon have a 21 x 15' room which will contain both a home theater setup with ELAC F6 floorstanders and a 12" sub, as well as a 4x12" Mesa half stack. I'm not concerned nearly as much with the quality of sound in the room as I am with the penetration of that sound throughout the rest of the house. Insulating WITHIN walls is unfortunately not an option as it's just too late for that and access within the walls will be extraordinarily limited.

What I'm primarily concerned about is a single 15' wall which borders the part of the house I'd like to disrupt the least. That wall will be behind the guitar rig, meaning the 4x12 will face 180 degrees away from it. I THINK what that means is the wall will primarily receive bass from it (it's a fully closed back cab, so even that will be minimal). The wall will, however, be roughly 15 feet away from the front and center channels of the HT setup. The HT speakers will rarely top -20 db from reference, so perhaps the guitar rig remains the issue--even it will rarely exceed 85db.

There are all kinds of suspiciously cheap egg carton or wave-style 12x12x2" squares available on Amazon. If they manage to dampen the sound that hits the key wall in the neighboring room by even 3db, it's worth using over nothing. However, I'd really like to have a more effective solution.

I don't care nearly as much about sound quality within the room as I do not disrupting the rest of the house. What would you do with this wall 15x8' wall? I realize other acoustic properties of the house will affect matters and that the construction of the wall changes, but let us assume for simplicity that all I can do is improve the wall from within the room itself.

FWIW I am already planning to have bass traps in every corner.

If it comes down to it, I'd rather dampen highs and mids. A generally muddy resonance in bordering rooms is, in my experience, far less annoying than an articulated sound complete with treble which demands your attention. Note that the cab has Vintage 30s in it which put out some serious highs...

As for my budget, it's flexible but I'd really prefer not to spend more than $1000 on 15x8' wall... I could easily afford enough Amazon 12x12x2" tiles (of questionable density) and surplus carpet to go behind it, but I'm sure you will have better ideas. Should I look at covering my own OC 703 panels instead and stacking them floor to ceiling?

 

[ralphus]

Too long? :/ I can't provide a tl;dr summary without saying "look to original post for details"--I tried.

I'll add this: I think focusing on that one wall is probably a mistake, right? Lowering reverb off the other walls is probably nearly as important as providing maximum damping on the wall that borders the rest of the house which I want to keep quiet.

Anyone?

 

[Poinzy]

Some photos or diagrams would help, at least they would help me.

 

[ralphus]

Sure. This just has the HT speakers on it, minus sub. The guitar cab (not shown) will be facing the opposite 15' wall (pointed toward the center channel you see behind the red rectangle). Its back will be a few feet from the 'key wall'.

 

[ralphus]

How do you think the quilts compare to cheapo foam rated at 0.68 NRC?

 

[Poinzy]

Sorry, for taking so long to get back here. I think I'm going to have to look at this again tomorrow. I'm a little too tired to think geometrically right now.

 

[ralphus]

No problem, I appreciate all the attention I can get.

 

[Poinzy]

I know a recording engineer who made a theater in his basement with powerful, multi-channel audio. I'll try to remember key elements of construction, if I can, because I don't remember the sound from the theater penetrating to the upstairs livingroom when a movie was being played.

Of course, the surface the engineer really had to worry about was the basement ceiling, not a wall. I think the reworked ceiling was suspended, so it became, in effect, just one, giant acoustic panel.

 

[AudioGeek]

Build yourself some acoustic traps using Roxul Comfortboard 80, 1" x 3" wood and covering with fabric, then hang where most effective. Easy peasy. They come six to a pack for about $60. You can cover a fair amount of wall area with six 2'x4' panels. You could also make bigger bass traps with the thicker Roxul.

It won't stop everything of course but should tone down a lot of it.

The best thing is of course to take out the drywall and put Roxul between the studs, replace drywall, then use panels/traps around the room.

Lemme tell ya, when I played a lot in bands as a drummer, this stuff saved my ass many times from pissing people off near some of our rehearsal spots. Plus makes the room much better if you're recording, natch.

 

[ralphus]

Okay, that looks quite doable assuming I can source the Comfortboard locally--and it looks like I can as Home Depot carries it.

Would covering that entire wall with it be excessive? Should I be targeting specific spots instead (directly behind speaker cabinet to start with)?

 

[AudioGeek]

It probably won't be excessive in this case if you don't have the internal walls insulated, because you're trying to stop noise to the adjacent rooms, not just optimize the acoustic in the room.

What are you going to use for bass/corner traps? Get them placed in the 4 corners, then you can try experimenting with covering a lot of that 15' wall or the near-field wall (behind the guitar cabs/speakers). Also if you have enough try some on the side walls, and if there's a door on that wall or exiting to the rest of the house, get them airtight around the floor and sides.

Here's a guy who made corner traps similar to ones I've made with the thicker Roxul Safe & Sound. Has a list of materials at about 3:00 and these are pretty easy to make as well. They'll soak a bunch of boom out of the room, and you can make sizes to fit your needs, stack them if you want, etc.

If it's just going to be the guitar in this room then you may not need the big mongo traps like these, but I did for my drums and whole band rehearsing.

 

[ralphus]

I appreciate the advice.

I was going to go with some simple bass traps--cheap Amazon stuff, which just might be enough for me. I think what I'll do is buy the cheap bass traps for all corners, and if after building and placing the panels bass proves to be an issue, I'll build my own higher density bass traps later.

I'm not huge on bass for movies and music and tend to keep sub gain lower than my AVR's room calibration recommends, and while I have a bass guitar rig as well it's not something I like to play as loud as my guitar rig (bass amp is 75w class D solid state, guitar amp is 90w tube, and anyone with a tube amp knows how that goes ). What I anticipate will cut through the walls the most (from experience at my current house) are the presence frequencies--presence is a bit of a loaded word, but generally it refers to upper mids, lower highs with guitar amps. It doesn't help that I EQ the amp's highs up.

I absolutely realize that ideally I'd be taking care of this IN the walls and just be doing stuff in-room to cut down on reverb and such to improve sound quality, but that just isn't how things have worked out with construction, and there have been enough delays with that entire process as it is... The internal walls will be insulated to some degree, but primarily with heat in mind.

I suppose if I go wall to wall and floor to ceiling with the panels, I essentially WILL be getting into construction--a wall to block a wall. From what I've read, standing the new 'wall' off a few inches should help with general dampening but slightly weaken bass dampening. Probably worth it in my situation, but I can worry about that later.

 

[Alobar]

If it were me I would go to the Lumber yard and buy something called resilient channel and mount it to the existing wall horizontal and 2' on center. Determine what thickness the original wall has for drywall and then get a different thickness to screw to the resilient channel. Don't mud it to existing drywall (other walls or ceiling) anywhere but use a flexible caulk to seal. You would need to extend the existing electrical boxes with deeper mud rings. This is how contractors often do it for a sound resistant wall to meet code. There are ratings for walls and ceilings , known as sound transmission class or STC rating. I would shoot for at least 50 if you want to keep a little peace for the rest of the inhabitants.
BTW, using different thickness of drywall with resilient chanel is an old trick. Sound transfers harmonically like a tuning fork when drywall is the same thickness. The resilient channel is made of metal and floats the outer layer of drywall without transferring sound vibration.
Lots of information about this on the web.
https://en.m.wikipedia.org/wiki/Sound_transmission_class

 

[Chip Chester]

Alobar is on the right track. Mass is your friend. Mass that absorbs energy is your friend. Eliminating air transmission is also important. Impact or structure-borne noise is important. Acoustic reflection/absorption management, even if frequency selective, is a distant fourth when it comes to preventing sound from migrating from one room to another.

Do we know if it's a basement room, with concrete floor and minimal heating? Or first/second floor room, with shared heating ducts, resonating floor spans, etc. Or it could be concrete first floor/no basement, like most of Florida. It makes a difference in sound transmission and recommendations.

Chip

 

[Alobar]

^^Definitely what Chip says about the floor and ducts.

 

[ralphus]

Great advice in this thread--so glad it came alive.

It will be first floor direct on concrete slab, single story house. I think the sheetrock is half inch so I could use heavier 5/8" for the secondary wall. The floor will have the thickest, heaviest pad I can get, dense berber carpet, plus some rugs throughout. The room will be connected to central heat and air (ceiling) and I'm not sure where the vent in that room will be. It would be just perfect if the ducts carried noise to the bedrooms at the opposite end of the house.

This thread gives me many options and I will start simple and progress from there. It's entirely possible I'm overreacting to the perceived problem (house isn't even inhabitable yet)--after all, except when recording, my amp rarely cracks 80 db. It just seems to cut so much deeper than, say, decent stereo speakers or reference monitors. Perhaps that's just my in-room perception based primarily on upper mid/lower high frequencies which us humans are more likely to be bothered by, but which may be less likely to carry throughout the structure (though I realize there are a lot of variables there and I won't know till I'm there)... Guitar cabs are infamous offenders here as many popular models of drivers have non-flat frequency response, to put it lightly. These are Celestion Vintage 30s with a peak around 2-4k.

Thanks to all.

 

[Poinzy]

Here I am, arriving late again. Glad things are working out.

 

[tomlinmgt]

I built a house in 2006 and, being a drummer, needed to isolate sound emission from one room into the rest of the house. I did a good bit of research and the most effective way to achieve isolation is to acoustically decouple the room from the rest of the structure...just as a few respondents have described here thoroughly. There is no quick and easy solution...it's gonna take some light construction to do this properly. I've since moved from that house and in my current house used the garage as a critical listening space for my audio hobby and had extensive acoustic treatments including OC703 bass traps in corners and a 13'x4' diffuser with 6" thick Roxul behind the diffuser on the wall that was a shared wall with the living room inside the house. The rest of the room has several more panels strategically placed throughout the room to control reflections/reverberation and I can say with certainty that the reduction in noise transfer into the house from the garage was not significant after all the acoustic treatments went up. The acoustic profile of the garage was severely changed, but from inside the house you could still hear music as low as moderate volume levels being played out there. Whether or not what's coming into the house is loud enough to disturb someone is probably up to the individual's level of tolerance. Now I'm using the garage as a rehearsal space for a music project I'm involved in, and with live, amplified instruments playing out there you can hear it all...LOUD and clear from inside the house. And the wall that separates the garage from the living room IS insulated.

 

[ralphus]

That basically tells me the light work of putting up bass traps and diffusers will improve in-room sound quality, but more serious construction is required if trying to improve the situation in neighboring rooms (and beyond). I suppose I still have it easier than you since I'm not a drummer and won't be having rehearsals at the house.

 

[Chip Chester]

You could make a "hat" out of fiberglas ductwork to help isolate the path to/from the HVAC system. For example, get a 6" long piece of 8x8 square fiberglas duct, and fasten it under the original duct, like an extension. (The 1" thick rigid pink kind with foil on one side.) Then, get a 6" long piece of 12x12 duct, same stuff, but a box with five sides. Hang the big duct box under the little one, with about a 3" gap at the ceiling. Outbound air will take three 90 degree turns on the way out. (You may have to boost fan speed for effective cooling.) But the benefit is that sound from the room will have to make those three 90 degree turns also, before it gets into the home's ductwork.

Dimensions and arrangements may need to be changed to fit your house, but it's concept that should provide some additional attenuation of the acoustic path.

Acoustical caulk is different than standard household caulking products, as it remains flexible instead of setting up. You're after an air seal with good flex, or compliance. The wallboard hanging on z-channel will move as it absorbs energy. You don't want to impede that movement, small as it may be.

Sealing around electrical outlets with that same acoustical caulk will also cut down on noise transmission. Messy, though.

There should be lots of info on the web about building home recording studios. Some of it will help.

Chip