[redjr]

Hello,

I'm getting ready to build-out a media room in my basement.  Luckily, I get to start from the ground up.  No pun intended.    It won't be a listening room, or ''true' home theater per se, but it will be my man cave for movies and stereo listening / office.  The space is not that large (15 x 10), and I really have no pressing need to isolate the sound 100%. There is a room with hardwood floors above the space that is little used and has area rugs.

Two of the exterior walls of my space are load-bearing and at this point insulated, but not rocked yet.  I'm still in the design stages, but....

For the other two interior walls, should I necessarily float the walls, and double sheet rock with offset seams?  If I float the walls, do I necessarily need to float the drywall too?  I was only planning on putting in a drop ceiling with heavier-mass acoustic tiles - with possibly insulation between the joists.  The floor will be carpeted.  I've been reading about GG between the rock, but wonder is it really necessary for my space and intended usage and sound blocking.  Obviously the 'deader' the room the better.

Except for the electrical (which I've over-spec'd) and drywall finishing, I will be doing most of the work myself, as I've finished a couple of basements in my time.  I just want to make sure I've accounted for all the 'serious' infrastructure  stuff before starting.  I don't like doing things over!

Comments?

redjr

[mcgsxr]

I cannot comment effectively on what you should do with respect to your needs, but I will share what I did, and how it worked.

My basement was finished this winter.  I filled the joist cavities and all interior walls with Roxul Safe n Sound.  I also used a solid core Safe n Sound door at the top of the stairs.

I can tell that there is music playing downstairs if I leave it on, close the door, and go upstairs.  But, I can play it louder than I would chose to in the basement, and it is not causing any issues upstairs.

I used 5/8 drywall for the ceiling.  No resilient channel even (sparky botched the pot light box height so it would have meant rework and delays I was not willing to put up with), and I it is fine the way it is.

I was looking to contain the sound, but not totally block it, and I would say I was successful.

I recommend Roxul in your interior walls, it will help.

I would think that if you stagger the wall, you won't need to go extra measures with the drywall, but bass will go through just about any wall you are willing to build too, so your call.

[JLM]

I've got the same (home office/listening room) but bigger (8 ft x 13 ft x 21 ft).

Stiffer is better (resonant frequency lowered/energy required to excite increased): 5/8 inch drywall; closer stud spacing (some say to vary the spacing).

More isolation the better (relatively cheap/easy):  staggered stud walls is a no brainer; insulated/lined supply air duct can all but eliminate furnace sound; insulated above drop (truly suspended) ceiling; use insulated exterior fiberglass door (with threshold and weather stripping).

Bigger the room the better, but proper room proportion is even more important (avoid simple multiples of room dimensions, like the 10 ft and 15 ft you mentioned).  This should be the starting point for intelligent design of any listening room.

[redjr]

Thx guys - I've got more decisions to make around the whole need for this much isolation relative to the type and function of the room.  Nothing will ever be at reference levels, so super anti-vibration measures are probably not in order.  Maybe doubling up on the drywall, or just using a single layer of 5/8" (does it come thicker?  Is there 1" drywall, or is that just too unwieldy?) will be 'good enough' for my multi-purpose room.  I like to build for the future, but I must be realistic about the present and what to include - or not.  I just need to get on with my design so I know what to buy and how much.  And, whether or not to seek a tradesman for assistance. - redjr

[JLM]

5/8 inch drywall is used to build code recognized fire rated partitions and is already heavy.  I've never seen thicker, but if available I'll recon its expensive.  Note that stiffness of a homogeneous plate is proportional to the square of the thickness, so 5/8 drywall would be 1.5 times stiffer than 1/2 drywall.  But the effect of span (stud spacing in this case) would be proportional to the square of the square.  So a 12 inch spacing would be over 3 times as stiff as a 16 inch spacing and 8 inch would be 16 times stiffer than 16 inch spacing.  So if you want stiff, I'd add more studs.

My 8 ft x 13 ft x 21 ft office/audio cave is not the ultimate, but IMO practical:  maximized size within the proper ratios of width to length to height (usually the limiting factor);  isolated structurally (staggered stud construction on interior partition walls); insulated everything; exterior fiberglass door with weather seals; insulated/lined flexible supply air duct.  Also ran dedicated electrical circuits for audio gear and splurged on cryogenically treated hospital grade receptacles.  Total additional cost = zero (cheapest door inside the house offset cost for extra studs and bigger top/bottom plates; cheaper carpet/pad offset the cost for those receptacles).  I didn't bother with tighter stud spacings or use more than 1/2 inch drywall as I was/am convinced that room size/shape and isolation are vastly more important to sound quality at reasonable sound pressure levels.  The only thing that got missed (thanks to uncooperative builder) was not isolating the drywall ceiling via C or Z gauge metal furring strips.  And I made the mistake of using recessed can light fixtures that are rated as air tight and to be in contact with insulation, but definitely not sound proof.

Front half of the room is all audio, the back is office (serious listening is nearfield and my desk chair lines up behind the listening chair).  Room shape/set-up ala Cardas.  Three tall bookcases line the side walls to help diffusion.  Six large acoustically panels have almost no discernible effect no matter where I put them (credit to room shape/size).  Room is located in basement (no rattling windows) opposite end of the house from 1st floor master bedroom with kids' bedrooms on the 2nd floor, but the room is located directly under dishwasher, washing machine, and dryer (that without the isolated ceiling, accented by all the isolation I do have, is easily heard along with footsteps).  Conversely because of lack of ceiling isolation the system can be heard from upstairs too, so someday I might come back and add a 2nd drywall layer to the ceiling with green glue.  But the overall effect when we first moved in was almost scary quiet (isolated). 

So having a dedicated room (with these virtually no cost features) is easily the 2nd best component of my audio system (after speakers).

[redjr]

jlm - Do you have some pictures you could share.  I know most of what we're talking about is behind the scenes and infrastructure related, but pics of your room would be nice too.  I've already planned out the electrical and will be adding a 100 amp sub-panel to help with 4 dedicated 20-amp circuits, a heat-pump for year-round heating and cooling, a DIY audio workshop, and another large space/den.  Several standard 15-amp circuits are planned as well.  I have no plumbing or heating duct work to worry about, and the space above is a non-issue.  I'm virtually starting with a clean slate - which is great if you have the time and money to invest in all the extras.  I was going to go with can lights, but now I'm thinking track lighting.  I saw another member's new listening space where he used curved track lights to great affect - both lighting wise and visually appealing.  My biggest issue with compromises to the design, is the way the stairs go down to the basement.  It was really a poor design for future division of the space without the stair entrance, or outside slider ending up in my office/media room - neither of which I want!  But sadly the stairs cannot be moved or turned 90 degrees due to the upstairs design.  The only thing that could be done would be to put in a circular staircase, but my wife nixed that idea.  I tended to agree though.  We're working with a 26 year old house and the walk-out basement that was never finished.  One of the previous owners decided to partition it up by using 1 x 3 studs which I never knew existed.  IMO they're pretty worthless as any kind of serious wall stud.  You can barely get a deep electrical box to fit.   All of it will be ripped out before I start.

So, I've just about settled on the physical space and want to get my permit application filed on Monday.  We'll see...  Thanks for sharing your design of your listening/media/office room.

Rick

[JLM]

Rick,

Any dedicated room is a huge advantage, so I'm sure you'll enjoy it.

I recommend wall mounted sconce lighting (if staggered stud walls are use) as I think they'll transmit less sound in/out than track lights.

(This is my first try at importing images to AC.  Taken by my iMac on my desk.  The walls are actually a yellowish/cream.)

[Housteau]

This topic has to do with sound isolation, but I was wondering if creating thicker stiffer walls was a good idea as far as bass goes?  My room has double sheetrock walls, because at the time I had it built I was under the impression from different articles I had read and from a fellow audiophile that stiffer was better for a good bass response.  But, over the years since I have read facts that say the complete opposite is true. 

My current understanding is that walls are necessary to set boundaries to create the proper acoustic space with the higher frequencies, but only have negative effects on the bass.  So, as far as bass is concerned the best room is no room.  I see a room with normal walls allowing bass to escape according to their flexibility and that making them stiffer would slow down that process allowing more of a build-up creating more, or deeper peaks and nulls.

[JLM]

Stiffer walls will reduce sound transmission, especially at higher frequencies, all else being equal.  But the primary reason to stiffen the boundaries is to reduce self-noise.  Frankly if you can hear the walls vibrate, turn the damn stereo down!  (Seriously if drywall if vibrating, imagine what it's doing to your ear drums.)

I see the listening room as a 2nd speaker cabinet.  Flexible walls means that they are contributing self-sound.  What did to buy to hear?  Drivers? (yes)  Speaker cabinet panels? (maybe, but I hope not)  Room?  (probably not).

OTOH we are accustomed to listening in rooms (not free space), so typical furnishings/construction is OK. 

[redjr]

This topic has to do with sound isolation, but I was wondering if creating thicker stiffer walls was a good idea as far as bass goes?  My room has double sheetrock walls, because at the time I had it built I was under the impression from different articles I had read and from a fellow audiophile that stiffer was better for a good bass response.  But, over the years since I have read facts that say the complete opposite is true...

This view is very interesting, and certainly flies in the face of most all audiophools that build separate listening room.  I'm not so sure it's for sound containment as sound deadening.  Isn't the over-arching philosophy to 'deaden' the room as JLM says, to as much "self-noise" as possible?  Creating a personal anechoic chamber.  Where reflections, echos, and vibrations of the sound are minimized - if not virtually eliminated?  Isn't the ultimate goal to hear the music as it leaves the speakers drivers without much more interference than was used to generate it? 

[TRADERXFAN]

I'm on mobile so apols if t his has been said. Couldn't read through all replies.
There are a few factors in how double drywall, green glue, floating walls enhance the performance of your listening space.

The noise floor can be much lower than in typical construction. But other aspects of the room need to be considered to fully obtain this benefit. Doors ceiling, hvac lines etc.

Room mode attenuation for cleaner bass is quite valuable. The structural difference in a constrained later damped walls absorbs the bass energy and reduces room modes. This is one of the most effective ways to deal with this problem. If only addressing this, then only one side of opposing walls need this extra expense to be effective. Proper construction is essential.

Then also leaking noise to other parts of the house which is same as the first point, I guess.

You really don't want anechoic conditions as it leads to lifeless music. You want diffuse environment.

[bpape]

When INSULATED walls vibrate (and they do so whether you can hear it or not), they are acting like a restricted range bass absorber.  Adding mass to the walls lowers the resonant frequency of the walls hence the frequency at which they'll try to absorb - and also the frequencies that will have an easier time entering or leaving the space.  Uninsulated walls will just ring like a big undamped bass drum and should be avoided at all costs. 

In general, adding mass to the walls will also allow less overall absorption in the room naturally so more would be added to get to the same target decay time. 

If you want to use the walls to your advantage and you're not violating code doing so, you can do either front and rear or both sides with one stud spacing and the other pair with a different spacing. I've done this effectively using 24" spacing front and rear while using 16" on the sides to vary the resonances from an absorption standpoint and broaden out what the walls are doing for you inside.

Bryan

[redjr]

...
Room mode attenuation for cleaner bass is quite valuable. The structural difference in a constrained later damped walls absorbs the bass energy and reduces room modes. This is one of the most effective ways to deal with this problem. If only addressing this, then only one side of opposing walls need this extra expense to be effective. Proper construction is essential...

I'm sorry for being so dense, but that paragraph made absolutely no sense to me.  Room mode?  Constrained later damped..? 

[Speedskater]

Stiffer is better (resonant frequency lowered/energy required to excite increased): 5/8 inch drywall; closer stud spacing (some say to vary the spacing).

This is the exact opposite of everything that I have read.

*********************************
It's 'Constrained Layer Damping'. That's two layers of drywall with peanut-butter like stuff in between (Green Glue)

*********************************
for more see:

http://www.greengluecompany.com/tools

[bpape]

Stiffer is not the goal. The goal is more mass. Stiffness just happens to come with it when you're talking more drywall. Wider stud spacing allows more movement (less stiff).  CLD's allow movement between layers to somewhat compensate.

[redjr]

Stiffer is not the goal. The goal is more mass. Stiffness just happens to come with it when you're talking more drywall. Wider stud spacing allows more movement (less stiff).  CLD's allow movement between layers to somewhat compensate.

So if mass is the goal and stiffness is secondary, is floating the walls something that should be done to help in the 'flex' of the wall 'unit'?
Furthermore, what are real audio gains to be heard under this extra mass approach.  Is this limited to improving just high-end systems, or can those of us lower down on the equipment rung benefit from these extra measures?

[bpape]

The extra mass is there to provide isolation from sound getting into and out of the room.  The only real audio gain to be had is to lower the ambient noise floor in the room to increase the apparent dynamic range of the system.

Double walls purely decouple the inner wall physically from the outside - again for isolation. If you have a single wall with drywall on both sides of the same studs, when the inside drywall moves, the studs move, and so does the drywall on the other side - essentially becoming a 'speaker'.  If the 2 sets of drywall are NOT on the same studs, there is no physical connection so the outer drywall is not excited nearly as much and not at all directly.

These gains would apply to any room.  Really more a matter of if the isolation is required pending how 'noisy' the rest of the home is, how much you need to listen at Midnight with a bedroom above you  , etc.    If the house is quiet, and nobody to bother, then not as big a deal and more can be used to address interior acoustics as opposed to isolation. 

Bryan

[rajacat]

 Does Green Glue and double layer sheetrock provide a similar effect as the double alternating studs. Double studs are not always feasible if you're retrofitting.

[oledude]

If the goal ultimately is to allow you to enjoy your movies and music without worrying if you are bothering others in your house, then that is rewarding in itself.

I would absolutely insulate between your ceiling joists because it is cheap and easy to do before your drop ceiling.  It is great that you don't have duct work to deal with, but that can be treated, too.

I added 1# mass vinyl over insulation and covered with Quietrock enhanced sheetrock on walls and ceiling in the room.  It is very noticeably quiet in the room, but I would not say it affected the bass response or room modes positively or negatively.  After treating with a few GIK panels, everything is under control and I can enjoy music and movies at a comfortably loud level with only minimal bass energy transfer to other living areas.  Which was my goal.  If you decide to put up the double drywall approach, the investment in the GG at 1-2 tubes per panel would be worth it completely in my opinion.

[bpape]

Does Green Glue and double layer sheetrock provide a similar effect as the double alternating studs. Double studs are not always feasible if you're retrofitting.

Using clips and channel would better replicate what a double wall would do. Double rock and Green Glue definitely helps even more. Allows the 2 layers to move independently for a bit more sound stopping while still letting the mass perform as a single layer.

Bryan