House Extension with a Dedicated Home Cinema Room

Harkon321

Well-known Member
Big tidy up today. Rooms now pretty empty. Fibreglass roof almost finished.

Next week we start first fix of electrics and cut new side access door. Old UPVC door (pictured will then be blocked up) and a small internal wall demolished.

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Harkon321

Well-known Member
I've already bought 100m of Van Damme blue but I've just worked out I'm going to be about 50m short. They don't have anymore stock and everywhere else seems be charging the earth.

Farnells are suggesting this as a replacement. Any thoughts?
https://cpc.farnell.com/pro-power/1...l-2c-2-5-100m/dp/CB08668?MER=sy-me-pd-mi-alte

It'll be for two speakers in the cinema room and then a couple of ceiling speakers in the kitchen. I figure it should be fine. The surrounds in my living room are only 1.5mm.
 

Harkon321

Well-known Member
Few small updates. We had a small utility area by the old back door. These units have been stripped out, and a new opening for a side door cut And the little window blocked up. Took a way longer than expected due to cables, pipes and a steel we didn’t know about all in the way. Building Control specced a new steel and we are back on track. Old back door now blocked up with double skin of dense concrete blocks which will help with the soundproofing.

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So I finally have a screen wall, of sorts...

Builders are coming back Friday to fit new side door, window in cinema room the dividing wall between this space and the kitchen. (Open it up, more light etc). They are then off for a week whilst I crawl all over it running speaker cables and CAT6.

Still need to do first fix as well but everything is marked out.
 

Harkon321

Well-known Member
Speaker cable? You only started building a month ago!
Helps when you're not doing the heavy lifting yourself.

I've finally made a decision about air recirculation/extraction for the cinema.

Extract
I've ordered a very quiet 5" inline fan. SL TD350SILENT
Really hope it fits as it is pretty large. Intend to run 5" ducting from above the AV cab to the front via the pelmet and across the front pelmet to outside.

Inlet
Currently planning to take 5" inlet from the kitchen. No fan, going to try it with just the positive pressure caused by the extract. Run ducting to behind the projector hush box and push air from back of projector to front.
 

Triggaaar

Distinguished Member
Helps when you're not doing the heavy lifting yourself.
Sure, but I still can't believe it. I've been working on mine for an eternity, so I'm quite envious :)

I've finally made a decision about air recirculation/extraction for the cinema.

Extract
I've ordered a very quiet 5" inline fan. SL TD350SILENT
Really hope it fits as it is pretty large. Intend to run 5" ducting from above the AV cab to the front via the pelmet and across the front pelmet to outside.

Inlet
Currently planning to take 5" inlet from the kitchen. No fan, going to try it with just the positive pressure caused by the extract. Run ducting to behind the projector hush box and push air from back of projector to front.
Yeah I looked at that extractor too. It should do the job. I think the passive inlet will be fine. It'll be negative pressure though.

Is this as well as aircon, or are you undecided on aircon?
 

Harkon321

Well-known Member
Wiring for air con but not fitting yet. At this time of year it’s hard to judge if it is needed. I’ve spoke to an installer and they can run the pipes outside so don’t need to decide now. It also means I can get away without studding the right hand wall (no pipes to hide) and fit the in wall speaker in to the block work. (Gain 120mm width)
 
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Harkon321

Well-known Member
Acoustic ducting arrived and extractor. Way bigger than I imagined!! 😳

New side door fitted and internal wall removed.
 

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Harkon321

Well-known Member
New side door from outside and also new window fitted. Got Virgin coming Thursday to move cable to the cab. Hoping they will be happy to run through roof joists if I predrill them.

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Mocked up Hisense 55’’ TV in family room and 3 xMonitor Audio Apex A40. Must say the build quality in these Hisense TVs leaves a lot to be desired.
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PsyVision

Distinguished Member
Must say the build quality in these Hisense TVs leaves a lot to be desired.
I agree, looks like they just bang a few bits of wood together and call it quits. They're not even square.
 

Harkon321

Well-known Member
Not much to report this week but have started a few things for the cinema room. Ordered some 12mm MDF to be cut in to pieces for backer boxes. These will be built in to the walls and ceiling to preserve the sound proofing when fitting my in wall speakers.

I then started working on the air recirculation. I’ve got two 5’’acoustic ducts in 10m lengths. One will take air from above the AV cabinet, along the pelmet and outside via an inline fan.
The inlet will drop fresh air behind the projector hush box and the projector will then exhaust in to the room.

I have looked at different places to have these ducts leave the room, as I was worried about impacting my sound proofing. I’ve settled on the void below the small remaining pitched roof. This is a picture from inside the roof space, looking towards the cinema room on the back of the house.
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I’ve then spent this weekend creating a small ‘dead vent’ to try to reduce the noise leaving the room via the ducting. It’s not perfect, and it’s smaller than I wanted due to space constraints, but it will definitely help. It’s made from 18mm ply that I had spare, then 12.5mm plasterboard with green glue between the two layers and all gaps sealed.
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Sat ready to be fitted. Will need two of us to lift it in to place.


Dead vent info

How to build a dead vent system
 

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Harkon321

Well-known Member
Need to finalise locations for Atmos speakers, now all the joists are in. I've marked what I think - all to scale. Brown shows the joist locations and the steel running across the room. I've labelled MLP, Atmos locations and pelmet. TopFronts will be inceiling, TopRears in the pelmet - both approx 45 deg.

LCR (Red) shown for context.

Due to the pelmet and joist spacing they will be just inside the Left and Right. Any thoughts?

I can go wider but they are then very close to the sides of the pelmet so figured reflections would be more of an issue. @mb3195 @kbarnes70 ?

Atmos Locations.JPG
 

Harkon321

Well-known Member
Might see if I can try them in those locations but also try them closer ( the other side of the steel). Currently top fronts are 1m 35cm away and the top rears are 1.1m away. Doubt I'll be able to tell the difference though to be honest.
 

Harkon321

Well-known Member
Few up to date pictures. Floor being screeded (spelling?!) today and doing the cinema stud work tomorrow. I've then got a week to cable it, then they will board it. Plasterer booked for 2 weeks so tight turn around.

Bit gutted about the door colour compared with the window. We ordered this door especially, and paid more for it, as it was the only company that did an aluminum door in a timber effect to match the existing UPVC windows. I colour matched the door to the existing windows and it was pretty close. The new window is also pretty close, but, now they've arrived, I think one is a shade darker than the existing UPVC and the Bifold is a shade lighter - making the difference more obvious. Hindsight is a wonderful thing. Either have to get used to it, or if it bothers us, purchase a matching ali window from the bifold company (Origin).

Bricks were also a worry, due to the colouring you can see. Builder is sure it is how they are drying due to the very heavy rain we had over a number of days. The middle ones still being wet in the cavity. Time will tell. They weren't laid like that so hoping they'll dry the same. They were all laid from the same 2 packs so it shouldn't be an issue with lack of mixing.

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mb3195

Distinguished Member
Need to finalise locations for Atmos speakers, now all the joists are in. I've marked what I think - all to scale. Brown shows the joist locations and the steel running across the room. I've labelled MLP, Atmos locations and pelmet. TopFronts will be inceiling, TopRears in the pelmet - both approx 45 deg.

LCR (Red) shown for context.

Due to the pelmet and joist spacing they will be just inside the Left and Right. Any thoughts?

I can go wider but they are then very close to the sides of the pelmet so figured reflections would be more of an issue. @mb3195 @kbarnes70 ?

View attachment 1393209
Sorry mate only just seen this.

Plans look good, I’d have gone narrower on mine if doing it again from scratch, so yours look ideal.
 

Steve Stifler

Well-known Member
Great thread - really interesting to see how you’ve overcome potential set backs. You’ll love it once it’s all done. Nice! 😀
 

Harkon321

Well-known Member
Started building backer boxes for the speakers today. Had the bulk of the done at the timber yard. 12mm MDF screwed and glued, then Green Glue then 12.5mm standard plasterboard. Finished pictures tomorrow.

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Screen wall knocked together. Unsure whether to have left and right inside the screen or outside. Will get some advice.

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Harkon321

Well-known Member
Anyone who does this for a living (@Seriously Ltd) has my upmost respect. I feel utterly broken after spending the weekend on this. lol

Just finished packing up the tools. To be fair spent the morning using existing Monitor Audio speakers from around the house and set up a 7.1 set up and played with different surround angles. After the wife kindly/begrudgingly did a blind test moving surrounds 20deg, I've realised stressing over exact angles is a waste of time. Couldn't hear the bloody difference when it came to it! o_O

Anyways progress....

Two atmos backboxes in and wired.
(12.5mm MDF, Greenglue and 12.5mm PB, gaps chalked etc)

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Front wall on the way.
Aiming for 2.5m wide screen. Left and Right tweeters will be about 1.95cm apart, so speakers just inside screen edges. (67cm from the side walls). Hoping that works...

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MK states to put them 10cm above ear level so that's what I've gone with. Think tweeters will be about 1.3m from the floor.
 

Seriously Ltd

Distinguished Member
AVForums Sponsor
All looking good👌
It can certainly be very stressful to say the least. Especially when best laid plans are not as straight forward as anticipated.
 

Harkon321

Well-known Member
For anyone interested in the sound proofing, I've included a few details below.

The house is detached, which makes things a lot easier. There is nothing above the cinema room and the kitchen/diner/living space next door. I'm therefore done a lot but haven't do everythig I could either.

The two outside walls
Both are 30cm thick (brick/cavity/dense concrete block) and are pretty effective on their own at stopping sound being transmitted to the outside. These will each have a single sheet of acoustic plasterboard attached and then skimmed. Window will be 'plugged' with 100m thick stud work, full of insulation and double dry wall or MDF.

The two remaining internal walls.

One is the original cavity wall of the house (old outside wall) and the other is a new 100mm block wall.

Both will have 100mm stud work in front. These studs do not touch the walls, so stop sound passing through via vibration. The bottom plate is screwed in to the concrete slab (separate slab to rest of extension) and to the joists via acoustic brackets. In the States these are referred to as IB3 clips. They use a rubber mount to reduce vibrations passed from the wall to the joists, so the stud top plate sits just under the joists. Easier to show in pictures:

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Stud work will then be filled with insulation and then boarded with 18mm OSB. Similar weight to heavy duty plasterboard but gives me lots of fixing points for pelmet, fabric frames etc. Each sheet will then have 1 or 2 cartons of Green Glue applied before a layer of soundblok Plasterboard is attached. Green Glue damps the sound and is meant to help with low frequency transmission. 1 carton gives 70% of results of using 2 and at £15 a pop I'm tempted to cheap out and just do one.

Ceiling
Same as the internal walls. 18mm OSB/GreenGlue/Acoustic Plasterboard

Speakers and Lighting
As most of my speakers are in wall, I'm cutting holes in my expensive and well planned sound proofing. Ideally you'd built pillars or whatever but I don't have the space. Therefore, everywhere I've cut an opening there will be a 'backerbox' behind it. Made from MDF or plywood, then green glue, then plasterboard and all edges chalked so no air gaps.

All lighting will run inside a pelmet, so no holes cut for the downlights.

Door
Single, solid core 30" fire door with 3 hinges. Will add door seals. Haven't planned for one at the bottom but can always remove and add if needed.

Acknowledged weak areas
  • The ceiling should ideally have had clips and channel to decouple this from the joists. I haven't done this as there is nothing above us and I didn't want the additional complexity of the clips and channel.
  • Because of this, and the fact that two of the walls aren't 'decoupled' with stud work, I will get sound flanking. i.e. it will go through the weaker wall and around my sound proofing. That said, those areas are right at the edge of the house, not where it's going to bother people. Is it perfect, no. Was it worth losing another 4" of the room in both width and depth - I didn't think so.
  • The door will be the biggest weak point. I've considered back to back communicating doors but didn't want the faff. Bolting two firedoors doors together or adding mass to the back. I'm going to see how a single door performs and there from there.
 

Apollo

Well-known Member
Acknowledged weak areas
  • The door will be the biggest weak point. I've considered back to back communicating doors but didn't want the faff. Bolting two firedoors doors together or adding mass to the back. I'm going to see how a single door performs and there from there.
I have back to back communicating doors for my room-in-a-room build but don't bother closing the outer door most of the time. With other doors closed in the house and a long sound path back to other occupied rooms there is next to no sound travel of anything much above 100hz.

Sub bass is another subject entirely though :)

My advice would be to fit the heaviest fire door you can find in an acceptable style and install perimeter seals. MOST importantly add a decent bottom drop seal and stiff threshold plate or it will leak like a sieve!
 

Harkon321

Well-known Member

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