New Build advise needed: sacrifice building height or width?

[8abel8]

Hi all,

I'm in the process of starting a outbuilding home cinema build very soon and decided to apply for planning permission to allow for building height of 3.2M, due to the 2.5M max height PD rule (and decided on a warm roof constrcution). Dimensions of the build started out at 6.2M L x 4.2M D x 3.2M H (with a small 1.2M D x 2.2M W entrance porch offset to one side) . During the consulation phase, the planning office came back to me asking if I would be willing to reduce the depth of the build to 4M. I agreed to this in principal but having thought a bit more about it I'm not sure this is the way to go because internally I will probably end up with around a 3.6M wide room (only 20cm difference but it all counts). Although I only plan to put in a screen size of 3.2M max ( for now), I always felt I would like a wider room to give more space for 3 seats plus plenty more to move around and not have the side speakers so close, ideally finished around 4.5M approx.

My garden is on a slope and the fall to the planned location is approx 420mm, which with planning approved would give me an internal height once done of around just over 3M which is nice. However, if I just stuck to PD, I could go for 6.2M X 5M (or thereabouts) and end up with less than 30SQM internally which is ok for PD but my internally ceiling height would come down to approx 2.3M.

Wondering what everyone thought and advise would be in this situation but I guess the answer would be what's more important to me I guess...

Many thanks.

 

[ashenfie]

A typical modern room is around 2.4m in height, so reducing the height would make the most sense

 

[8abel8]

A typical modern room is around 2.4m in height, so reducing the height would make the most sense

That makes sense, but wondering whether for Atmos purposes, wouldn't a taller height be more beneficial?

 

[ashenfie]

That makes sense, but wondering whether for Atmos purposes, wouldn't a taller height be more beneficial?

If you want to bonce the sound then angles are important and so average height is like to be in the sweet spot.

 

[silva741]

You didn't mention how many seats and rows you're planning to have, but if it's only one row I would prefer the wider room. ATMOS would benefit from a taller ceiling, but the bigger distance between the listeners and the side surround speakers would be very welcome, as well as a wider front soundstage. But a generous ceiling cloud covering the first reflection points would be a must, IMHO.

 

[Romey]

My planned room is similar size. Internal 6x5x2.5m

Dedicated cinema room?
How many rows and seats?
Realistically, how often will it be 1, 2, 3, etc. people using the room?

If it was me, (dedicated room, mostly me, sometimes with wife, sometimes with brother, seldom with 3+ people), I'd prioritise good audio for main seat, ensure seats 2&3 have good coverage (bass, positioning of speakers), and not worry about other seats (I'll only have 3 and bring in more from other rooms those few occasions). So I'd trade some width for extra height in your case.

I'd also go the extra steps and consider the internal measurement of finished walls and ceiling once room is completely installed and consider tradeoffs there.

In my case I had a pretty confident clear plan early on, that's changing frequently as I get more clear on details. So I'd encourge you to do some level of scale mock up with any room treatments, front speaker depth, screen size, throw distance, seating position, horizontal viewing angles and so on. The result of that work for me meant a drop from 160" to 150" diagonal screen, little room to spare on throw distance, but seating at 2/3rds room length that puts horizontal viewing and L+R speaker angles bang on

 

[8abel8]

You didn't mention how many seats and rows you're planning to have, but if it's only one row I would prefer the wider room. ATMOS would benefit from a taller ceiling, but the bigger distance between the listeners and the side surround speakers would be very welcome, as well as a wider front soundstage. But a generous ceiling cloud covering the first reflection points would be a must, IMHO.

Sorry, should have mentioned this but really only one row of 3 seats (or comfy sofa) with perhaps a very small riser at the back of the room with space for a couple of narrow cinema style seats incase of extra quests but this will be far and few between but definately some space n the back for this scenario.

Dedicated cinema room?
How many rows and seats?
Realistically, how often will it be 1, 2, 3, etc. people using the room?

Dedicated 100%. I have an existing attic conversion as a dedicated room but not satisfied with a width of only 3.2M room width and 4M depth. Likely to be on mostly me and the wife, with perhaps my brother and his wife a couple of times a month.

I'd also go the extra steps and consider the internal measurement of finished walls and ceiling once room is completely installed and consider tradeoffs there.

The measurements I gave for finished internal width of 3.6M is already taking into account internal acoustical treatment (going for fabric covered walls and treatment behind, hidden).

 

[8abel8]

In my case I had a pretty confident clear plan early on, that's changing frequently as I get more clear on details. So I'd encourge you to do some level of scale mock up with any room treatments, front speaker depth, screen size, throw distance, seating position, horizontal viewing angles and so on. The result of that work for me meant a drop from 160" to 150" diagonal screen, little room to spare on throw distance, but seating at 2/3rds room length that puts horizontal viewing and L+R speaker angles bang on

Looking at a seating distance of between 4.2-4.5M back from screen (3.2M screen width) leaving me with approx 1m to the back wall but this will be determined once the build is done and I can test this.

 

[8abel8]

But a generous ceiling cloud covering the first reflection points would be a must, IMHO.

Because I'm building a warm roof, I plan to leave the joists exposed and fill with acoustical trearments at various points and then cover the lot with acoustical cloth, this will also hide the atmos speakers. That's the plan anyway.

 

[Romey]

Sorry, should have mentioned this but really only one row of 3 seats (or comfy sofa) with perhaps a very small riser at the back of the room with space for a couple of narrow cinema style seats incase of extra quests but this will be far and few between but definately some space n the back for this scenario.

Dedicated 100%. I have an existing attic conversion as a dedicated room but not satisfied with a width of only 3.2M room width and 4M depth. Likely to be on mostly me and the wife, with perhaps my brother and his wife a couple of times a month.

The measurements I gave for finished internal width of 3.6M is already taking into account internal acoustical treatment (going for fabric covered walls and treatment behind, hidden).

Sounds like a good plan. You've already got the 3.2m width as a reference point. Given mostly you/wife I'd say you already have plenty of width for sides at 100 or 110 degrees. Maybe try matching that distance to MLP with atmos distance in your conundrum. And perhaps look at the golden triangle ratios of length, width, height.

 

[Praetorpwj]

Firstly and speaking as someone in a similar privileged position of being able to create a new dedicated space (within constraints) my recommendation is create a space you love over one that complies with any idealised shapes. You can work within pretty much any shape. I've flip flopped between two different plans, one slavishly adherent to the various advisory 'rules' (some of which strike me as contradictory) and one which I actually like. I'm going with the one I like which happens to be squarish and wider than it is deeper.

To summarise you have two options?

Option 1 - 6.2m (l) x 3.6m (w) x 3m (h)
Option 2 - 6.2m (l) x 5m (w) x 2.3m (h)

You talk about side speakers so I assume your going for a 7.1.4 system.

In both options you have plenty of throw and viewing distance. Personally I would be sitting no more than 3.5m from a 3.2m wide screen which gives a 50 degree viewing angle. I'm 3.1m from a 2.9m wide screen and that's plenty immersive without being straining. Also since you will be putting your L & R speakers behind an acoustic screen at that distance your listening cone will be less than minimum recommended 44 degrees.

Option 1: A three seater will be around 2.5m wide giving you around 550mm clearance each side for circulation and side surrounds. Personally I think this is ok but like all shoebox cinemas your sides will be firing relatively close to the end listeners. Maybe go for a 5.1.4 instead. If you go with a combination of 3m high ceiling with 3.6m wide room then off recommended angles your atmos will be on the walls rather than the ceiling. for that room width I'd lower the ceiling to around 2.5 or 2.6m.

Option 2: Loads of space around seating for sides & rear surrounds. Less claustrophobic. Room for temporary additional seating. Loads of space on screen wall so you have option to place L&R speakers outside screen for wide listening cone (up to 60 degrees). Main problem is Atmos which should be minimum 2.4m high. Personally I go with 35 degrees from MLP front and back and side to side so there is no more than 70 degrees max angle between atmos positions. If you angle the atmos to fire directly at MLP than this increases the measured distance than if they were firing straight down & overhead so I think you would get away with it.

Personally I like option 2.

 

[8abel8]

I think I will wait to see what the planning

To summarise you have two options?

Option 1 - 6.2m (l) x 3.6m (w) x 3m (h)
Option 2 - 6.2m (l) x 5m (w) x 2.3m (h)

You talk about side speakers so I assume your going for a 7.1.4 system.

Actually internally after baffle wall will end up with room length approx 5.5M but finished width will either be 3.6M (if the planning office get there way and insist I reduced the size down, something to do with the assessment of the character of the area) or over 4M (not quite decided on the final dimensions but PD would allow probably up to 4.5M internally finished).

I'll probably will wire and hopefully do 9.x.6 but yes, side surrounds is what I was referring to.

In both options you have plenty of throw and viewing distance. Personally I would be sitting no more than 3.5m from a 3.2m wide screen which gives a 50 degree viewing angle. I'm 3.1m from a 2.9m wide screen and that's plenty immersive without being straining. Also since you will be putting your L & R speakers behind an acoustic screen at that distance your listening cone will be less than minimum recommended 44 degrees.

In my current room I sit 2.9M from a 2.7M wide screen but I feel image quality is much improved sitting a bit further back to which I'm willing to sacrifice some immersion for but this is still all to be determined but I get your point on the listening cone but I feel the speakers I'll be using (JBL's 3677) with their wide dispersion horns will make up for some of this.

I agree with option 2. I've always felt in my current 3.2M x 4M room everything is a little to close together and like the feel of a larger spacious room, will also help with accomodating all the speakers behind the baffle wall (including 2 JBL 4645c subs which are huge).

Just wondering whether I'd suffer too much with a lower ceiling height (bearing in mind the speaker baffle for the atmos speakers will end up flush with the ceiling).

 

[8abel8]

If you angle the atmos to fire directly at MLP than this increases the measured distance than if they were firing straight down & overhead so I think you would get away with it.

I'll be using JBL Control 25's for Atmos speakers which will be attached with a ball mounting system so I will be able to aim them fairly well, so that might work out.

 

[Praetorpwj]

I'll be using JBL Control 25's for Atmos speakers which will be attached with a ball mounting system so I will be able to aim them fairly well, so that might work out.

Yeah it should be fine. If your ceiling is 2.3m high and your listening position is 1m off floor then firing straight down overhead distance is only 1.3m. Angled 45 degrees front rear and side to side and positioned towards MLP increases distance to approx 2m.