[Nick77]

I will be building a new home with dedicated audio room. I pan on doing staggered studs along connecting walls for isolation with double drywall and green glue.

Question, is it beneficial to treat all four walls and ceiling in the room with DD and GG if isolation isn't an issue on 2 walls and ceiling?
Im not sure if DD and GG help provide to a dead room or strictly isolation?

Thanks

[ctviggen]

Double drywall provides mass, which is different from isolation.  Isolation reduces sound transmission from one side of the "wall" (or ceiling) to the other.  For instance, if you have a 2x4 wall with double drywall on each side, you still have a direct sound transmission path, through the drywall, through the studs, and through the other drywall. 

I don't technically understand what greenglue is doing, but it's not going to take the place of isolation.

[blutto]

Double drywall provides mass, which is different from isolation.  Isolation reduces sound transmission from one side of the "wall" (or ceiling) to the other.  For instance, if you have a 2x4 wall with double drywall on each side, you still have a direct sound transmission path, through the drywall, through the studs, and through the other drywall. 

I don't technically understand what greenglue is doing, but it's not going to take the place of isolation.

....if you check the performance charts you will find that it actually does....especially on wall assemblies ( and with very little volume penalty so its easy to retrofit with )...for some reason clip systems are slightly more effective on ceiling assemblies ( though the gold std here would be clips and GG )....

Cheers

blutto

[blutto]

I will be building a new home with dedicated audio room. I pan on doing staggered studs along connecting walls for isolation with double drywall and green glue.

Question, is it beneficial to treat all four walls and ceiling in the room with DD and GG if isolation isn't an issue on 2 walls and ceiling?
Im not sure if DD and GG help provide to a dead room or strictly isolation?

Thanks

....all six boundary surfaces have to have high STC values to have an isolated space....and remember that the built boundary surfaces should have no penetrations...so surface mount your electrical and for gawd's sake no pot lights...and have a pro come in to deal with the HVAC issues...and spec a solid core door ( or two doors on a split frame )...

Cheers

blutto

[JLM]

STC: sound transmission coeffient (higher the better).
HVAC: heating, ventilation, air conditioning

I built a listening room 8 years ago in our (then) new house.  Two exterior partitions against insulated poured concrete walls (no acoustic considerations).  Two interior partitions against storage spaces (staggered stud walls with fiberglass batt insulation - probably overkill).  One door (exterior insulated fiberglass door with weather strip - works great - better than double interior doors or solid core interior door IMO).  One ventilation duct (lined/fiberglass insulated duct - works great, can barely hear furnace. 

Downfall, the ceiling (directly under kitchen/mud room).  I'd specified metal gauge furring strips (clips) between drywall and bottom of joists, but builder balked (so ended up with direct connection - a big no no).  He added 12 inches of fiberglass (so what?).  My mistake was adding six recessed can light fixtures.  My fix (if I ever really feel that its needed) is to add another layer of drywall with Green Glue (changes vibrations into tiny amounts of heat) and changing out to surface mounted strip lights.

Overall the room was very successful:  spookey quiet (well removed from master/kids bedrooms, a plus since I start listening at 5AM); room proportions/nearfield setup ala Cardas works great (room treatment/EQ not needed);  BTW these ratios maximize width/length for given ceiling height (in my case 8 ft).

[bpape]

Sound is like water, it will find the weakest point to get out (or in.). The staggered stud provides physical isolation from one side to the other.  On the other walls, if they're free standing and NOT tied to another room on the other side, no need to stagger the studs but yes, the double drywall still helps with isolation.  As has been said, HVAC, lighting, outlets, switches, etc. must all be accounted for. 

Bryan

[Nick77]

      On the other walls, if they're free standing and NOT tied to another room on the other side, no need to stagger the studs but yes, the double drywall still helps with isolation.                                                         

Brian the free standing walls are 6" thick and not so much concerned about isolation. But if DD and green glue help to provide acoustical profit for interior listening environment than i don't want to cut corners.

Would you treat all walls with DD and GG even if isolation wasn't the goal?? In other words does GG or CDL provide more than isolation?

[JoshK]

My $.02   If you are going to the trouble to build a room and do it right, I'd buy Geddes' book on how to do it and read up.   You may or may not agree, but he has done the research and has a lot of info there (I haven't read it, I haven't built a room).

[Jeffrey Hedback]

Hello Nick 77,

Adding to Brian's excellent words, you want (if possible) all of your surfaces to have a similar acoustical "footprint" in terms of transmission loss, impedance and the spectrum of the reflected energy within the room.  Next, I have been able to document the "bass trapping" benefits of GG with (2x) drywall and it is indeed a great benefit below ~80Hz.  Simple suggestion then: do double drywall w/ GG on all wall and ceiling surfaces.  This is a great start to an excellent dedicated audio room.

[JLM]

Nick77, just to be clear, wall thickness does almost nothing for sound transmission. If the studs support drywall on adjoining rooms, the sound will transmit, period (regardless if it's a 2x4, 2x6, whatever).  An alternative to staggered stud walls is the use of metal furring strips/clips (like pretty much has to be done on ceilings).

In my case the additional steps were basically free (compared to the construction of the rest of the house that has more expensive doors/carpet) and so incredibly well worth it (plus it left less space for wifey to hoard).  The key is in the use of proper design concepts more than budget.

[bpape]

Just a small correction JLM.  Actually, when building a wall, the deeper the cavity or the more distance between 2 layers of mass in the case of staggered studs or double walls, the lower the resonant frequency of the structure is (which translates to less of the spectrum having an easier time getting through) as well as it being a lower frequency 'absorber' as part of the room.

Bryan

[blutto]

Hello Nick 77,

Adding to Brian's excellent words, you want (if possible) all of your surfaces to have a similar acoustical "footprint" in terms of transmission loss, impedance and the spectrum of the reflected energy within the room.  Next, I have been able to document the "bass trapping" benefits of GG with (2x) drywall and it is indeed a great benefit below ~80Hz.  Simple suggestion then: do double drywall w/ GG on all wall and ceiling surfaces.  This is a great start to an excellent dedicated audio room.

...could you, when time allows, please elaborate on the "bass trapping" benefits of GG....

Cheers

blutto

[Nick77]

Hello Nick 77,

Adding to Brian's excellent words, you want (if possible) all of your surfaces to have a similar acoustical "footprint" in terms of transmission loss, impedance and the spectrum of the reflected energy within the room.  Next, I have been able to document the "bass trapping" benefits of GG with (2x) drywall and it is indeed a great benefit below ~80Hz.  Simple suggestion then: do double drywall w/ GG on all wall and ceiling surfaces.  This is a great start to an excellent dedicated audio room.

Makes perfect sense, appreciate it. Thanks!

Gotta get some more green goooo.......

[Nyal Mellor]

...could you, when time allows, please elaborate on the "bass trapping" benefits of GG....

Cheers

blutto

It's from unpublished work AFAIK...it definitely works though, GG and DD = very low modal ringing <100Hz. DD by itself can make matters worse.

Below - 4 subs, GG/DD on Isomax, no Eq, no acoustic treatment.