Acoustic - is sound dampening neccessary? (1 Viewer)

[Nazxul360]

Hi everyone,

Just registered and this is my first post here, so let me know if I'm doing anything wrong!

I'm currently helping my brother set himself up a home theatre room (he has the money, but I have the knowledge and hookups ). The room my brother will be setting everything up in just has plain gyprock walls, and tiled floor. Now I'm no professional in acoustics, but I know that that is not really the ideal environment for a high end home theatre system, as it will sound unnatural, and the sound would bounce off all the walls/floor and any illusion of surround sound would be lost. On the other hand, the amplifier that he'll be running them from, is the latest Pioneer one - the VSX-LX70. It claims to have "an intelligence that can adapt to any room's acoustics".

To get to the point, my question is, are these brand new amps with their auto-calibration mics and acoustic intelligence able to completely compensate for that? Or do you guys think it's still worth investing in taking action to dampen the walls and stop the sound bouncing around? If so, what options are available, and what to you guys think is the most effective?


Oh, and to sneak another question in, what options are there and what do you guys recommend for soundproofing the room (stopping sound from leaving the room - being it absorbing it or blocking it)? He'd like to be able to crank this thing pretty loud without upsetting a certain other resident of his house.

Anyway, sorry about the lengthy post, and thanks in advance for the help guys!

 

[Vin_G]

Kaine,

I am not claiming to be an expert, but I will tell you what I know from talking with a few HT designers.

You do want to have a tight room, meaning no drop ceiling and no open spaces. Try to make the room rectangular so one dimension is not divisible by another (you can predict modal responses with a rectangular room too). Build a tight room with double drywall on each wall and ceiling (you can use varying thickness of drywall between the two layers). You can also use Green Glue between the layers to make it tight as well but this costs money. Also, try to hang outdoor doors and not indoor ones to contain the pressure in the room.

A solid/tight room will create reflections and so on, but the idea is to contain the bass pressure so the subs can pressurize the room and get maximum response. The higher frequency reflections can from your other speakers can be controlled by acoustic paneling, etc.

Also make sure that the front face of the front speakers are 3' from the front wall so that nothing above 80hz is reflected.

As far as your floor goes, if this is the basement, make sure you put a wood sub-floor to help you feel the bass vibration. It does nothing for sound though. You can see it here: (Basement OSB Subfloor Video)

If he is using tile, make sure he puts some area rugs in the room, especially between the front speakers and the seating area.

Hope this helps.

 

[Vin_G]

One more thing, if you want to prevent sound from escaping the room, you can use staggered studs in the walls. Use a 6" or 8" cap and toe board for your framing, then use 2X4's for the studs and you can stagger them of course. Then weave insulation (horizontally) through the studs.

In the ceiling, insulate between the joists, put up one layer of drywall, then install z-channel tracks (a metal channel that screws into your joists or studs; it protrudes from the wall and you screw your next layer into the channel so that it de-couples the drywall from the joists/studs. You can also do this on your walls if you like.

Foam-board under your drywall may be another option too.

 

[Wayne A. Pflughaupt]

Kaine,

Welcome to the Forum!

Vin's already pointed you in the right direction (excellent stuff from a guy doesn't claim to be an expert!), but to briefly recap, staggered stud walls with double (or even triple) 5/8" sheetrock for the walls and ceilings, with air-tight outside-type doors with full weather-stripping, including threshold will get you most of the soundproofing you need. If you can double up on the sheetrock on the other sides of the wall, even better.

Keep in mind that if you air-seal the room you're going to have air conditioning issues, as typically the air circulates around and under the door. So, you'll need an air return vent in the room as well as an AC vent.

As far as acoustics in the room, do not put in a tile floor!!!!! If you do, the room will be an echo chamber! Typically wall-to-wall capeting and regular furnishings will take care of any reverberation issues, but if you want to take it a step further you could do something like install a low-pile carpet half-way up the walls all around the room.

Re the Pioneer receiver and its "intellegence that can adapt to any rooms acoustics," the auto calibration systems on modern receivers essentially do equalization to compensate for less than perfect response that is caused by room interactions with the speaker, and the speaker itself. Most work pretty good, but it won't do anything for a "live" room with hard floors.

Regards,
Wayne A. Pflughaupt

 

[Nazxul360]

Hey guys,

Thanks for the response, I really appreciate the detail and depth you guys have gone into to help me out, but it appears I haven't explained myself properly. :frowning:

Thing is, my brother isn't building the room from the ground up - it's already there. He already lives in the house and has decided to turn one of the rooms into a theater room. So the walls have been up, the tiles down, and the ducted air-conditioning in for a long time. :frowning: To it's credit, it IS a small rectangular room, but I know the tiles are one of the biggest downfalls, so I'm trying to convince him to lay carpet over them (actually that carpet half-way up the walls idea is pretty cool as the walls have a kind of skirting board half-way up the wall running all the way around the room [I don't know the proper name for it] so carpet running up to that would look nice).

Regardless, I'm definitely putting all of this information to him as he's already put a lot of money into the equipment, so he might as well have the best environment to compliment it - but I don't really think he's going to be wanting to pull the walls apart to do any major work like that.

So if you guys know of any less drastic measures that could be taken in order to get the same sort of result, I'd really appreciate hearing those as well. I know they won't be anywhere near as effective, but if that's all he's willing to do, the it'll better than an echo chamber.

 

[Wayne A. Pflughaupt]

I think there may be some misunderstanding here as to the difference between soundproofing and acoustical treatment. Wall-to-wall carpet is a great acoustical treatment for reducing reverberation (echo) inside the room that I doubt anyone would consider "drastic". Reducing reverberation is not the same thing as soundproofing. The latter refers to keeping sound contained inside the room. With soundproofing unfortunately there's no free lunch: Less drastic measures will result in reduced soundproofing.

If your brother doesn't want to tear out the walls, that's understandable - don't think I would either. As I mentioned before, mass and air sealing are key elements to soundproofing, so he could get some - probably significant - improvement by adding a second layer of sheetrock to the room, and even more by doing the same to the other side of the wall in the adjoining rooms. And, the sealed, solid-core door. If your brother isn't willing to do any of that, then he can expect no improvement in soundproofing. Unfortnately there is no getting around basic physics.

Good luck with the project, and keep us posted.

Regards,
Wayne A. Pflughaupt

 

[t62nz]

I have set up low-cost sound damping in a double garage (with concrete floor) and gib walls. I glued a 2nd sheet of gib wall to 3 internal walls using silicon glue - first I glued 2cm thich panel of polystyrene to the back of each sheet of gib wall, then glued it on with silicon - this flexes with sound, the back wall of the garage was carpeted with very low pile carpet, a very large carpet mat 90% of the floor size had edging put on it and placed on the floor, the 3 re-gibbed walls have got floor to ceiling black thermal drapes (these go right into the corners). One important thing is to not have these new sheets solidly attached to the original wall, they need to to be able to flex slightly - so rubbery silicon glue is all I used - placed a 1/2 inch chock under each sheet to keep them off the ground when gluing on.
So achieved not a bad internal sound damping and also blacked out the room at the same time, drapes are pulled back to convert it back to a normal looking room when required.
When the equipment was initially set up in there it sounded shocking, vast improvement now - esp for the Sub sounds.

 

[Brian.R]

You can also put rugs over the tile and build inexpensive wall mounted sound absorption panels out of 1x4 boards and fiberglass (better is rockwool) with some open-style cloth cover. Burlap is ugly but there are other good choices. If you are creative you can also make it look somewhat artistic with different colors, patterns etc. Search online to find ideas.

You can also hang heavy rugs on the walls to help. Some people like that look.

Brian

 

[Leo Kerr]

There are other possibilities, as well. But to repeat a common theme:

at least from the front of the room to the front row of seating, the tile needs to be covered with carpet!!!

I think a more formal name for the wooden band around the room is a "chair rail," which is generally a piece of molding of some sort, and, with a little bit milled out of the "bottom," would make an excellent transition strip. I'd also cheat, and probably use carpet tile on the walls, were I doing that.

Except, realistically, it's the space above the seated ear that needs to be treated against echo.

Something that's a bit more expensive, but can look "very cool," are some of the recording studio treatments -- from the high end, stained wood abfusors, to the funky dark purple expanded foam textures, such as from Auralex -- diffusers and absorbers. Try Sweetwater Sound.

You might want to be careful around automatic "magic" systems. Sometimes they work, sometimes they work 80% of the way, but make it impossible to get the rest of the way there, and sometimes they don't work at all. Acoustics are always going to be a challenge, but at least you have a dedicated space to work in, rather than an overall compromised setting.

Leo