some last minute advice on basement reno (subflooring? and primer between drywall layers?)

[mac_angel]

Short and sweet (yea, I was kidding myself when I wrote that).
shorter version. More info in the following.
I'm having underlay and carpet installed. Would putting OSB subfloor in the theater room make a big enough difference in sound isolation?
Should I paint good, sealed primer between drywall layers for helping sealing and sound leakage?

Finishing the basement in a townhouse. Planning a dual layer drywall for the connecting walls to the other units. Semi-floating wall - not touching the joining wall, but connected to the concrete floor, and overhead joists. Also doing a dual layer drywall ceiling with resilient channels between. Everything is in place and ready for the drywall next weekend.
Order I was planning. Ceiling (first layer), all walls (first layer). Taping and mudding (rough to seal, not to have a finish. But obviously not lumpy to make it uneven). Resilient channels, then second ceiling, and second layer for the joining walls. All this would be finished.
So, second question first I guess. Should I paint primer on the first layer ceiling and joining wall? I have special primer that is suppose to do a better job at sealing and such. I got it for painting our garage because the people before use smoked in there and it definitely helped. So I was wondering if it might do a little bit of good to help sealing the joints and corners. It's next to no extra work, so I'm considering doing it anyway.
First question second. I'm having carpet and underlay installed ("professionally" by HomeDepot (I live in Ingersoll, Ontario, in case anyone has other suggestions that are inexpensive)). So they'll be doing the vapor barrier and such. Would putting down OSB before the underlay and carpet help with sound isolation? Mostly concerned about lower frequencies, as well as the cost of OSB lately. I was planning on it before, when it was still ~$20/sheet for 5/8ths". If it would make that much of a difference, I could still do just the theater room with about 6 or 7 sheets and just have a small lip in the threshold. It would probably take another 7 or 8 sheets to do the whole basement, and I really don't think the cost is worth it for the rest.
I have a single Paradigm Servo 15 at the moment. Later, way down the road, I'm hoping to add another sub, but first I need to pay for all these supplies, and then my next purchase will be a 4K projector (upgrading from my 1080p).
There's a lot of info I'm leaving out because I ramble, and this is already long, lol. But I was just looking for those specific answers.
Also, I rent. The owners are 'paying' for the supplies for the basic renovations. But extras I'm paying for out of pocket, with a very limited income.

 

[-Jim-]

You may be asking for help a little late in your process if it's ready for drywall next weekend. This Gent (Jeff in Ontario) does a great job of explaining what works well and how to do it for a DIY. There are various levels of expenditures and expected results.

How to Soundproof a Room | DIY

But first you need to know your layout of equipment and seating positions, so you can plan the cabling / wiring - right now, and provide for any future expansion to the system. I think OSB on the concrete floor isn't where you should focus your $$ and efforts. Are you doing an Atmos system? What speaker configuration are you planning for?

 

[mac_angel]

You may be asking for help a little late in your process if it's ready for drywall next weekend. This Gent (Jeff in Ontario) does a great job of explaining what works well and how to do it for a DIY. There are various levels of expenditures and expected results.

How to Soundproof a Room | DIY

But first you need to know your layout of equipment and seating positions, so you can plan the cabling / wiring - right now, and provide for any future expansion to the system. I think OSB on the concrete floor isn't where you should focus your $$ and efforts. Are you doing an Atmos system? What speaker configuration are you planning for?

That's why I was saying there's a lot that I am leaving out or it would become a very long post. I was only looking for those specific answers.

 

[-Jim-]

Use this Green Glue between the layers - not sealer. You need a bit of an air gap to increase the sound deadening over what 2 layers of 5/8" drywall will give you. Don't bother with the sealer between the layers or the OSB on the concrete floor. If you do a good job in the Home Theater Room (HTR) with the 2 layers of drywall installed as directed, and a second wall inside of the existing room spaced constructed appropriately you can just use a single drywall layer for the rest of the basement.

A big deal is not having forced air heating & ventilation in the HTR as it transmit the sound you are tying so hard to mitigate. Go to a dedicated heat pump for an outside wall, radiant heated floor, or even electric baseboard heat if you can't afford the heat pump. (Although most provinces are giving big subsidies with no tax these days.)

You really should take the time to watch those Videos. It could save you a lot of grief.

 

[mac_angel]

Use this Green Glue between the layers - not sealer. You need a bit of an air gap to increase the sound deadening over what 2 layers of 5/8" drywall will give you. Don't bother with the sealer between the layers or the OSB on the concrete floor. If you do a good job in the Home Theater Room (HTR) with the 2 layers of drywall installed as directed, and a second wall inside of the existing room spaced constructed appropriately you can just use a single drywall layer for the rest of the basement.

A big deal is not having forced air heating & ventilation in the HTR as it transmit the sound you are tying so hard to mitigate. Go to a dedicated heat pump for an outside wall, radiant heated floor, or even electric baseboard heat if you can't afford the heat pump. (Although most provinces are giving big subsidies with no tax these days.)

You really should take the time to watch those Videos. It could save you a lot of grief.

I've actually watched the videos. As I said, there's a lot I left out.
The 'shared' walls are not even 100% concrete, but some areas that are just drywall and pink insulation between the units (I have another thread from last fall that has the pics, I think). So what I did was put up a vapor barrier with about 12" over the ceiling, down the wall, and 12" out on the floor, sealed it up with tuck tape. 1" hard foam insulation on that wall (reflective side out), floor to ceiling, sealed again with foil tape, and held firm with 1x3 studs. Then I put up a second vapor barrier, sealed, and a second wall of 2x4 that wasn't touching the first. Rockwool insulation, and another layer of vapor barrier. And those are the walls I was planning on the 2 layers of drywall, with the sealing primer.
I added pink insulation in the ceiling joists, and stuffed extra in the joists that are on the joining walls. Small problem being that those are also used for the A/C exhaust ducts. I had to put up some cross blocks so I could attach the top of the second wall I put up, but I also filled the gaps with the hard 1" foam insulation, sealed that, and then the vapor barrier over that, too. With building the second wall, once the drywall is up, those two joists will be behind the wall completely.