Axiom Home Page Forums General Discussion Home Theater HT in-progress

deleted ... post got away from me

As most know ... I'm in the middle of working on my home theater ... just thought you'd like an update. But first some background:

The media room was getting in the way of moving into our new house (the room was not being built correctly). So, we put it on hold and moved in just before the Massachusetts locked down for Covid. This turned out to be a good thing because there was a lot more wrong with the build than I first knew about. It also gave me time to experiment and re-think.

Now that I had a real room I could setup the speakers, get a feel for different arrangements and refine my speaker layout. Originally I was not sure if I was going to setup on the long or short wall and wired the ceiling surrounds to do both. I knew setting up on the short wall would be the best for surround sound but setting up on the long wall would give me a more living room feel. Ultimately I would chose the short wall but it took many months of experimentation before I was convinced. Interestingly, if I was setting up for two channel alone I'd probably have setup on the long wall.

After that I took down the walls and discovered that some of the studs were warped enough to touch the channel in places. This was the 2nd time taking down the walls. The first time I had the builder do it because the panels didn't move in places (and a few other reasons). You'd think that they check if the walls moved when they put the panels back up ... anyway there were enough other problems (clip layout) which forced me to take down all the clips and resilient. Since everything was off the studs I wanted to correct an oversight and put-up a layer of mass loaded vinyl. So, this brings you up to the current state.



Hopefully I'll be putting up the resilient again in a couple of weeks

Thought about adding a layer of mlv in my HT. You'll have to let me know if it helps. I'm going to push safe and sound against the subflooring then put the regular insulation back in beneath that and the ceiling drywall. Trying to dampen the sounds going through the two floors as much as possible. Also adding two layers of 5/8 drywall. I'll use safe and sound in the wall studs.

Well, that may be hard since I have not tried it without MLV

Use lots of screws when attaching the drywall to the channel. I used one every 6 inches and still had to add more later for a few random rattles.

If I did channel again in a room with subs I would lay a heavy bead of silicone on the channel before attaching drywall. I cant remember if you are backing the drywall with osb. If you are it will reinforce the stiffness of walls and increase bass variation. Toss up between isolation and performance.

One layer drywall on channel- walls act as large diaphrams. Help lower decay times of lower frequencies due to surface area. Less stc performance. Potential for rattles.

Two layers on channel w/green glue- neutral assembly. Great stc.

One layer with wood backer- extremely stiff wall. Bass decay longer. Potential for reinforced nodes.

Two layers with wood backer- might as well be concrete, but without the stc performance. Not a great use of budget, but people do it.

The transmission loss of the assembly only needs to be higher than the ambient noise in adjacent spaces. So, if there is laundry nearby for example, an stc of 60 or so is plenty. If you are trying to keep the sound IN the room bass energy is the problem. Maybe the MLV will help with this, but I have no experience with it.

If I was to redo a built from scratch room for me, I would stud my walls as normal, insulate with quiet zone, then run comfortboard 80 perpendicular on studs. Then one layer of drywall. Done. Flexible with super high stc, no chance of rattles.


Whatever you do, put a smoke alarm in there connected to the rest of the house detectors. You arent going to hear it otherwise.

Exciting and I'm curious; What are the room dimensions? Number of seats? size of screen? What are you doing for A/C, a dedicated unit or tying into the houses system? What is MLV?

Mlv is a vinyl sound dampener. It works for mid to higher frequencies. It’s not thick enough to affect low frequencies.

Trevor, I think this is going to be a multi post reply ... On this

I agree with you with a few thoughts and observations.

Going with 3 layers. The first layer goes up with a screw every foot. The next layer with a screws offset by 6”. The finial layer with screws offset 3” from that. I guess if you really wanted to be sure you could put a in one more round into that finial layer if you felt it was needed screws every 6”. That would result in a screw going into the channel every 3”.

As you probably know … each layer should be put in with a different length screw long enough to get a good grip but short enough not to exceed the depth of the channel. Now even though the builder assured me he had experience with hat channel he made a face when I asked if he was doing that. So, I made sure that he had these lengths on were hand. Unfortunately that didn’t stop the workers from occasionally using a length that was too long and as result I found a couple of shorts. I also had several rattles in different places. I’ll say more on this and your other comments in another post.

LC,
I was supposed to have a room 18'x23' but while I was thinking finished the architect gave me that unfinished. So, I lost 6" on all the walls to spray insulation and safe & sound and 3" on each wall to clips/hat/OSB/double wall board plus a bit more to padding out the studs, MLV, plaster and a change in the back wall to go from a staggered wall to a double wall. All in all I'm gong to end up with about 16'x21'.

Planning on five main seats if I can fit them (else 4). A game table in back with five office chairs which can be moved behind the main seats for additional viewers and two large bean bags in front of the main seats.

Screen size is 150" with masking if I need to make it smaller.

The HVAC has two huge dead vents (think mufflers) for the supply and return. The supply is connected to the HVAC and the return leads into the hall near an HVAC return.

MLV stands for Mass Loaded Vinyl. It's there as yet another material density. There are virtually no air gaps in it as I have glued and corked it together. I'm hoping that it will take a bit of energy out of the low end but Canes maybe right ...

With the HVAC in the room connected to the home/house system, won't some of the sound just travel through to the rest of the home. even with mufflers?