New Build 5.2.4

Superhans

Active Member
Hello all I am in the privileged position to shortly plan a dedicated new build room as part of a general side extension project. The crude caveman scratchings below give an guide to the current thinking. On the plan everything apart from the stairwell is part of the new build.

The room is designed to house a 5.2.4 system which currently resides elsewhere in a non-dedicated partially treated living room. Equipment list:

LCR - M&K IW150 (1st gen)
Surr - 2 x M&K IW95
Height - 4 x M&K IW85
Subs - 2 x SVS 3000
Receiver - Marantz 7010 (to be replaced with processor/amp)
Projector - JVC 7000
Screen - Seymour Premier 132" Center Stage XD (16:9 with CIH masking)

Structurally new room will have cavity brick/block walls three sides and a twin timber stud rear wall, flat warm roof above. Basic untreated dimensions are 5.9 (l) x 5 (w) x 3 (h).

I have allowed for 200mm wall offset incorporating 50mm void, 100mm timber plus 2x soundblock w gg. Ceiling void of 300mm to allow for isolation soundproofing, speaker and AC soffits etc. So internal treated space of 5.7 (l) x 4.6 (w) x 2.7 (h).

I have assumed a single row of 4nr seats as I can't be bothered with risers and want to be able to place the screen as low as possible for comfort. However because I have a good space between seating and rear wall (around 2m) I have assumed for some bar and stool seating for casual entertaining.

Room will be partially treated. There will be a screen wall to conceal LCR and subs. Black out velvet for first 2m walls and ceiling, Bass traps and fibre panels for first reflections etc. I haven't thought about lighting yet. Projector and AV rack will be wall recessed and accessed from an adjacent room via a back panel.

Angles on speakers are ok with 22 degrees on LCR, 120 for surround, and 45 on height. Subs I am assured are best located front corners and they will sit at different heights on some sort of baffle wall buildout.

Anyway I have a few options / issues that may affect layout for which I would welcome advice.

1). Basic dimensions. I cannot go any wider than advised and would ideally like to reduce a bit due to proximity to neighbour boundary which I need as front rear access. Ideally I would like finished internal width to be 4.2 rather than 4.6m. Current width is largely dictated by width for a 4 seater which seems to be on average 3.3m plus decent each side access (650mm). So to better I either need to find a comfortable 4 seater slimmer than 3.3m (don't want loveseats or cinema flipups), reduce soundproofing allowances ie isolation clip plus boards rather than 100m timber with insulation and boards or reduce side accesses to 500mm. Are any of these sensible / realistic? Separately I can also raise the ceiling a bit if there is any benefit to that?

2). Upgrade to 7.2.4? I have decent space behind seating however due to position of entry door I am struggling to find a place to incorporate rear surrounds. I can't use entry from room to the right by the way as this is 1m above theatre room. I could incorporate into bass traps but this is not in compliance with Dolby guidelines (separately I'm not sure how you do comply with Dolby guidelines for rear wall mounted surrounds as they are supposed to sit within zone of height speakers). Also I would have to move the side surrounds from 120 degrees to 95 degrees which would be pretty close to seating especially if access reduced to 500mm. I'm only bothered if I have to move the entry door location as I'd have to tweak the ext wall behind.

3). Screen baffle wall. Is there any point? I have IW speakers which only take need 100mm depth. I have 500mm being used largely to conceal the SVS subs which seems like a waste. Could almost fit in a second row of seats (see Q4).

4). Bar Stools. I know this is quite popular in US builds but I'm not likely to be hosting Superbowl parties. Its a cheap way to provide overflow seating but I'll likely have to increase surrounds install heights. Again is there a better way to provide temp seating without resorting to beanbags? I have storage behind if necessary.

5). Windows / doors. Although I intend to use this space as a dedicated room I am mindful that any future buyer might want an alternate use especially as it backs onto rear gardens. Accordingly I am musing with installing windows and possibly a door behind the screen wall for future proofing. Even though I am building a room within room will this knacker the soundproofing?

That's the basic plan. If I've missed anything obvious please let me know.


Cheers to all in advance.
 

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Superhans

Active Member
Hmm Lots of views but not much interest. It would be useful to get some feedback; I will be doing a separate build thread once extension shell and core finished but I want to make sure that basic parameters seem ok. Perhaps if I boil down queries:

  • Can you comfortably fit a four seater in a 4.2m finished width assuming less than 500mm clearance either side?

  • Would it be better to reposition rear door closer to centre to enable a 7.2.4 setup even though not strictly constructed to Dolby standards or go with a 'by the book' 5.2.4 setup as per current plan?

  • What is reasonable gap to leave beneath soundproofed ceiling level to enable soffit / coffer for speakers, lights and 100mm AC ducts (Need this to calculate structural soffit to enable min 2.7m Atmos height)?
 

Roohster

Distinguished Member
Hmm Lots of views but not much interest. It would be useful to get some feedback; I will be doing a separate build thread once extension shell and core finished but I want to make sure that basic parameters seem ok. Perhaps if I boil down queries:

  • Can you comfortably fit a four seater in a 4.2m finished width assuming less than 500mm clearance either side?

  • Would it be better to reposition rear door closer to centre to enable a 7.2.4 setup even though not strictly constructed to Dolby standards or go with a 'by the book' 5.2.4 setup as per current plan?

  • What is reasonable gap to leave beneath soundproofed ceiling level to enable soffit / coffer for speakers, lights and 100mm AC ducts (Need this to calculate structural soffit to enable min 2.7m Atmos height)?

I think the reason you've not had many replies up until now is that the first post is a bit overwhelming :p
There's an awful lot to take in.

Now you've broken it down to smaller questions I think you'll get more response.

1. The four seater sofa question is very much a question of aesthetics and personal choice. If you need a 4 seater, go for it (as long as you don't mind a bit of a squeeze getting past it.)
It's better (IMO) to have spare seating space than getting a three seater only to discover you could do with more room.

2. I've got a 7.1.2 set up (in a smaller room) and in my opinion, adding rears makes a big difference... so if you can fit them in, I'd recommend it.

3. No idea about this one, sorry.
 

Broadsword

Well-known Member
I plan to fit a row of three 2.45m wide seats into my 3.2m available space so I would say a four would be fine. You won’t have a sweet spot with a four though, so maybe consider a love seat arrangement for the middle two seats? Are they recliners? Do you really need four seats?

I wish I could fit rear surrounds in my setup so if you can get them in I would. Even if you don’t instal them now, having the cables ran and the right dimensions and layout would be good. You can then itch you upgrade scratch later on.
 

Superhans

Active Member
I think the reason you've not had many replies up until now is that the first post is a bit overwhelming :p
There's an awful lot to take in.

Now you've broken it down to smaller questions I think you'll get more response.

1. The four seater sofa question is very much a question of aesthetics and personal choice. If you need a 4 seater, go for it (as long as you don't mind a bit of a squeeze getting past it.)
It's better (IMO) to have spare seating space than getting a three seater only to discover you could do with more room.

2. I've got a 7.1.2 set up (in a smaller room) and in my opinion, adding rears makes a big difference... so if you can fit them in, I'd recommend it.

3. No idea about this one, sorry.
Thank you for your response. It was certainly not my intention to overwhelm; I may have been spending too much time on AVS Forum!

I'm happy to wire for a 7.2.4 system, probably for 9.2.6 just to be on the safe side. I'm just struggling to see how you can satisfy Dolby requirements for rear surrounds when you have inwall speakers that sit outside the Atmos zone.
 

Superhans

Active Member
I plan to fit a row of three 2.45m wide seats into my 3.2m available space so I would say a four would be fine. You won’t have a sweet spot with a four though, so maybe consider a love seat arrangement for the middle two seats? Are they recliners? Do you really need four seats?

I wish I could fit rear surrounds in my setup so if you can get them in I would. Even if you don’t instal them now, having the cables ran and the right dimensions and layout would be good. You can then itch you upgrade scratch later on.
Thanks I'm trying to follow the rules as much as possible and I was given to understand that having wing seats close to walls affected room modes. The main thing was to have a single row to avoid risers.

Also I thought it wasn't best practice to site the MLP in the centre (either length or width) again for room modes?
 

Harkon321

Well-known Member
Hi,

Looks to be a great room.

MLP shouldn't be in the centre, that's where your room modes are strongest? Antony Grimani covers this in his room acoustic videos.

There's a lot of thought gone in to your room already.

To give my opinion (and it is only that) on a few of your points...

1. What level of sound proofing do you want to achieve on those cavity walls? My plans was, originally, the same as yours. 100mm, decoupled stud work on all 4 walls. In the end we scaled this back to save space. The cavity walls actually do an excellent job on their own and although you can hear some low level noise outside, it's nowhere near loud enough to cause any complaint. Flanking sound is more of an issue though.

2. I'd highly recommend fitting rear surrounds and moving the surrounds to 90 deg. If you are worried about localisation go 12-24" above seated height. If you are using in wall (IW95) then you can build backerboxes and fit them in your sound proof wall. This gives you more distance to listeners and might also help your width query as the speakers don't stick out. The new IW150t are meant to be excellent and could be a better choice. (Or S150t or S95 or M40t if you want to keep on walls. You'll get a much better bubble of sound with the tripoles and less chance of isolation.

Moving the door to the center might work, but only if you still have height above that for the projector. If not then wider rear surrounds. I'd fit them either way.

3. You don't need a baffle wall if you are fitting IW150s.
You mention your sub locations. I'd also planned to have subs in the two front corners, but having now built the room, set up a sub and taken measurements in each location, that doesn't give the best response. I have a null that I can't clear with two front loaded subs, but opposite corners remove this completely. Wire sub cable to each corner and try out REW sim to check out simulate different locations.

4. Seating. No ideas here, sorry. I'm doing bean bags.

5. There are ways you can cover windows and even doors and maintain sound proofing. There are good examples of window plugs on AVS. I built door to cover mine. It's not as good as a completely isolated wall, but I need an exit to meet regs.

I don't know if you've planned aircon, ventilation or heat extraction but if not, then these require some detailed though.
 

Superhans

Active Member
Hi,

Looks to be a great room.

MLP shouldn't be in the centre, that's where your room modes are strongest? Antony Grimani covers this in his room acoustic videos.

There's a lot of thought gone in to your room already.

To give my opinion (and it is only that) on a few of your points...

1. What level of sound proofing do you want to achieve on those cavity walls? My plans was, originally, the same as yours. 100mm, decoupled stud work on all 4 walls. In the end we scaled this back to save space. The cavity walls actually do an excellent job on their own and although you can hear some low level noise outside, it's nowhere near loud enough to cause any complaint. Flanking sound is more of an issue though.

2. I'd highly recommend fitting rear surrounds and moving the surrounds to 90 deg. If you are worried about localisation go 12-24" above seated height. If you are using in wall (IW95) then you can build backerboxes and fit them in your sound proof wall. This gives you more distance to listeners and might also help your width query as the speakers don't stick out. The new IW150t are meant to be excellent and could be a better choice. (Or S150t or S95 or M40t if you want to keep on walls. You'll get a much better bubble of sound with the tripoles and less chance of isolation.

Moving the door to the center might work, but only if you still have height above that for the projector. If not then wider rear surrounds. I'd fit them either way.

3. You don't need a baffle wall if you are fitting IW150s.
You mention your sub locations. I'd also planned to have subs in the two front corners, but having now built the room, set up a sub and taken measurements in each location, that doesn't give the best response. I have a null that I can't clear with two front loaded subs, but opposite corners remove this completely. Wire sub cable to each corner and try out REW sim to check out simulate different locations.

4. Seating. No ideas here, sorry. I'm doing bean bags.

5. There are ways you can cover windows and even doors and maintain sound proofing. There are good examples of window plugs on AVS. I built door to cover mine. It's not as good as a completely isolated wall, but I need an exit to meet regs.

I don't know if you've planned aircon, ventilation or heat extraction but if not, then these require some detailed though.
Thanks very much for the encouraging words Harkon. I remember running through your thread which I think was also a new build extension and looks terrific. To address your points..

At the moment the room is 5700mm long with seating approx 3500mm which is about the 3/5 point so should be ok for room modes.

1). I'm assuming 200mm depth each wall which reduces a 5m wide room to 4.6m. I don't know how much better this would be instead of isolation clips and board directly to blockwork but I'm using Inwall speakers apart from subs so 200mm avoids the need for columns and also makes the room slightly less square. I've reworked this a few times with width reflecting either 1 row of 4 or 2 rows of 3 but I really want to avoid risers and be able to have surround speakers and screen placed low so I'm going with the single row.

2). I'm probably going to move to 7.2.4 and I didn't know about the 150T inwalls so thanks for that! Only issue is where to place the door; i'd love to have a side entrance like you would make things a lot easier. I'm going to lose the bass traps and have the door in the right corner so I can just squeeze rear surrounds in at 150 degs.

3). I'm going to take your suggestion and lose the baffle wall. Was really only hiding the subs but as you say it'll give more room to play. I assume you cant see the subs when the lights are off?

4). Bean bags seem realistic!

5). Thanks will check out

I do plan for some ventilation but i've got a 300mm plus gap between roof joists and acoustic ceiling to assume that should be plenty.

I'm sure I'll be working this thing to death once I plan the fitout. I'll try to snuck into a couple of the pro build open days to take some notes!
 

Harkon321

Well-known Member
200mm per wall is quite a lot. What is the make up?

Mine was:
20mm gap
100mm stud full of insulation
12.5mm plasterboard
Green Glue
18mm OSB
Skim

The MK in walls all fit in a 100mm stud. I also did double thickness backerboxes for these.

Isolation Clips straight to the blocks isn’t great and you then have no air gap. The air gap, plus the mass of the wall is what stops your bass.

My sub at the front at the moment is white so I’ve wrapped it in a piece of black MVel fabric loosely and you’d never know it was there, sat on a black carpet, against a black wall.

300mm is fine. My ducting is 125mm but the inline fan is bigger - I think 250mm approx.
 

Superhans

Active Member
200mm per wall is quite a lot. What is the make up?

Mine was:
20mm gap
100mm stud full of insulation
12.5mm plasterboard
Green Glue
18mm OSB
Skim

The MK in walls all fit in a 100mm stud. I also did double thickness backerboxes for these.

Isolation Clips straight to the blocks isn’t great and you then have no air gap. The air gap, plus the mass of the wall is what stops your bass.

My sub at the front at the moment is white so I’ve wrapped it in a piece of black MVel fabric loosely and you’d never know it was there, sat on a black carpet, against a black wall.

300mm is fine. My ducting is 125mm but the inline fan is bigger - I think 250mm approx.
I'd assumed a similar buildup but with a 25mm gap, 2 x 15mm soundbloc rather 1 x 12.5 and allowance for some sort of clipped fabric system concealing a bit of acoustic treatment on first reflection points. Got me close to 200mm which given I am hand scaling was a convenient dimension to draw! Probably a bit overkill and I'll likely scale back a bit.

Do you need any insulation behind backer boxes or can they be fitted quite tight? I didn't fit boxes in my current build which was probably a mistake.

I have a pair of matt black SVS 3000 so I doubt they would show too bad.

I'm planning for projector, AV rack and and fan / ac to be housed adjacent to main room with only minimum direct interfaces to avoid some of the trickier joinery.

I was re-reading your build and I have a few questions so I'll head over there at some point.
 

Harkon321

Well-known Member
My backerboxes don't have any insulation behind, as I simply didn't have space. I guess in a ideal world I would, but I didn't think it was worthy of increasing the depth of the whole wall for that small area. All my boxes were made of 12mm MDF, GreenGlue and 12.5mm PB. They sit really tight to the wall but don't touch. Mine is a smaller room, so every cm counted.
 

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