Newbie building a dedicated home cinema

[Liamt]

Can I preface this by saying I've never owned a television in my life...so please excuse my ignorance :)  

 

I'm building my own home as an owner builder in Brisbane. 

 

I have allowed for a dedicated home theatre / listening room. The steel frames are about to go up so I figured now was a good time to start planning.

 

It will be approx 6m x 4.3m. I'm hoping for a row of 5 seats at the back on a raised platform and then two x two seats as per the attached image.

 

I'm hoping for a 140" projector screen that I will make.

 

I got a bit excited, and have been buying speakers and an AV receiver over the xmas break. So far, I've bought

 

Denon AVC-X8500H receiver
2 x PMC twenty.25 floorstanders
2 x PMC twenty.23 floorstanders
2 x ELAC BS244 bookshelf speakers

1 x SVS PB3000 subwoofer

 

I'm hoping for both a high quality music listening experience as well as full Dolby Atmos. 

 

I've been offered a good price on a pair of PMC twenty5.21 bookshelf speakers as well as a PMC Twenty5.C centre speaker. 

 

The floor of the cinema is 200mm thick concrete suspended about 2m in the air. 

 

The wall frames will be bluescope steel frames.

 

I'm hoping for great accoustics in the room as well as great soundproofing so that very little noise escapes the room. 

 

I have a few general questions

 

1. Soundproofing - Once the steel frames go in, I was going to green glue a layer of plasterboard onto them. I was then going to construct a new set of timber frames internally and green glue two layers of plasterboard onto this. This will give separation between the two walls. There is a floor to ceiling window, but it is triple glazed and thermally broken. I will then make some heavy curtains to hang floor to ceiling around the room. I will then have a drop ceiling with stary night lighting. Does this sound like it will be sufficient to keep the noise from escaping ? Any suggested improvements.

 

2. Room size and shape - As I am building internal walls, I have great flexibilty over the shape and size of the room. It there a suggested size that I should make the room to minimise standing waves and improve the accoustics ?

 

3. Speaker placement and dolby atmos choice - I've looked into the Dolby Atmos setup guides. I suspect the room is too small for 6 ceilings, so was going to go with Atmos 7.2.4. Is this the best choice for the room size ? I'm guessing the twenty.25 should be front left and right and the twenty.23 should be back left and right ? If I get a second subwoofer, will the PB1000 or 2000 suffice or should I get another 3000? Will mixing the ELAC speakers with the PMC be ok or should I buy the PMC bookshelves ? How important is it to get high quality ceiling speakers ? I'm assuming that the dont have to be PMC as they are really only used for limited sections of the movie sound ?

 

4. Accoustic treatment - I have a company that produces stretched canvas prints for artists and photographers. I was thinking of printing movie style posters and then stretching them over 50mm deep frames and filling the back with accoustic foam. Is this likely to work ? The canvas is cotton.

 

My post is long and there are a lots of questions. I would appreciate any input about anything that you have to offer. Thank you in advance. 

[hopefullguy]

plan befor you buy anymore speakers.. 23's as side surrounds with 2 rows? cant see that working, where will they go based on your seating plan

 

the rear row should not be on the rear wall. the riser goes back to the rear wall with the seats at least 1m off the wall

 

 

[Liamt]

Thank you. If I bring the seats 1m from the wall, can I use the 23's as rear, pushed up against the all ?

[cazzesman]

As a new convert to the World of Frequency curves I was going to recommend you also research the combination of a Minidsp product with  Dirac Live, but I see the Denon has Audyssey.      I know very little about Audyssey but my recent purchase of Minidsp with Dirac Live has been a resounding success.     

 

I'm sure many here would recommend Acoustic Treatment products that will do the job you want done.    I'm a firm believer in you get what you pay for in this area.       At a minimum; rear corner bass traps and 1st and 2nd reflection points for the main left and right speakers.    If you have the funds then maybe something on the rear wall behind the seats. 

 

Just make sure that whatever form of canvas you use for the prints, it will actually let the top end sound waves penetrate to the Acoustic product beneath.    No point have Acoustic panels if the material merely acts just like a plaster wall and bounces the signals straight off into your ears.    It must absorb those 1st and 2nd reflections into the panel to work properly.

 

Happy building.

 

Regards Cazzesman

 

 

[Mobe1969]

I'm not really familiar with the speakers so can't comment. On the subwoofers, the PB3000 is great, but if you are thinking two, you'd want two pb3000. I have a 3.6x48m projector theater, and have dual PB20000s and it is very good, Your room is larger.

 

What is above the room? Top floor so don't care? At any rate you probably want to use poly insulation in the cavity.

 

I'd also suggest filling wall and ceiling cavity air gaps with poly insulation also. You do mention the other wood and double plaster and I can't quite picture it, So Are you saying say 90mm steel framing with plaster, then putting 70mm or something studs inside and glueing plaster on both sides of that? Is the timber really needed? Or could you just cut and glue the extra plaster to the interior plaster, then poly fill, then glue the outer layer where required.. At any rate, I'd poly fill.

 

I'd have the entry door either open out, or open the other direction (for front right speaker in the event you get a nice floorstander.

 

Also the obvious idea of cabling for the speakers And hdmi CABLE in the cavities. For the HDMI (and network possibly) I'd suggest using heavier diameter electical ducting so the cable can be changed if needed.

 

Seating wise, ditto on the rear wall comment. Also, have you thought of having just smaller walkways on the sides rather than prime listener position open? Seriously if just you in the room viewing, it will get to you not being able to sit in the sweet spot... Also better to give side viewers better separation/balance  from the surround speakers on their side.

[hopefullguy]

agree with changing to smaller walkways on the sides.

 

subs.. this is tricky as i believe in one sub at the front and one sub behind your rear row centrally located.. it then does not "have" to be the same size sub imo. as we are in Oz we are stuck with an inferior choice of subs for HT use. if mixing say the pb3000 and pb2000 because the 2000 is "near seating" it wont need to do as much work, you are not talking 2 retail box subs..ie yammy 515/216 etc. anyway just my 2 cents... in the end its your money and your choice.. note: cant justify the pro over the old pb2000. put the saving to the centre (below)

 

centre.. buy the biggest you can. if the one you listed has a bigger brother buy it. nothing worse than insipid centres, from experience.

 

 

[Quark]

I'd also suggest putting the front seats to the centre of the room, not the sides.

 

You'll need to put some bracing in the roof for the projector mount. Where it goes will depend on the projector you buy and screen size. Did you have something in mind?

 

Great soundproofing isn't cheap (e.g. resilient clips, furring channel and green glue). A mid price option is insulation to all walls and ceiling, plus a layer of yellow tongue flooring all walls/ceiling and then use 17mm Fyrchek plaster (cheaper than Soundchek and similar performance). The yellow tongue has the benefit of providing a good mount for projector, speakers etc.

 

For the HDMI cable to the projector - if going 4K don't cut corners, get a good quality fibreoptic cable. Also note most are directional with a source and display ends. They won't work if installed backwards.

Edited January 15, 2020 by Quark

[Liamt]

Thank you so much Quark, Hopefullguy, Mobe1969, Cazzessman

 

I really appreciate the great suggestions. I'm definitely moving the front row into the centre as some of you have suggested. 

 

Above the theatre is a guest room that will rarely be occupied. I have Red Tongue flooring above the floor trusses, but will screw sheets up to the bottom of the trusses as suggested. 

 

The Fyrcheck sounds like a good choice too. 

 

Mobe1969 - It will be a double wall. So, the wall with the plaster on steel frame, then a second wall inside the room on timber (only because I'm handy with timber). So, effectively double walls. I had read somewhere that this stopped the wall acting as  speaker and flexing. 

[Guest Peter the Greek]

You might want to treat the floor - there is a product called Angelstep. Put that down, then 1 (or better 2 with GG in between) layers of chipboard. That'll help isolate the floor and reduce flanking. Otherwise your plan is sound.

 

HVAC planning needs considering - look at the plans for dead vents on the soundproofingcompany.com website

 

I would wall over the window, or make a "window plug" for it - search AVS for that, there will be a bunch of threads.

 

Gear......well, you really "should" have waited. You'll want two rows of side surrounds for starters. At least 2 subs. Both of these additions require special EQ and calibration. 

 

Acoustics.....I'd engage someone - you're going to have bass issues with the construction for soundproofing. I recommend these guys https://questai.com/

 

The front row needs to come forward and the back row off the wall (at least 900mm)

 

You're going to want an acoustically transparent screen - OZTS make a good one

 

[Guest Peter the Greek]

BTW - the speakers are woefully inadequate for a room that size

[Guest Peter the Greek]

Oh and the door - you want interlocking fire rates doors. Preferably two separate ones with the inside one attached to your new isolated wall and the outside one to the frame of the house

[Guest Peter the Greek]

PPS never, ever give up the middle MLP for a walk way - access to the back row should be via the sides

[Guest Peter the Greek]

I'd put all the gear in a rack in that storeroom. It'll need ventilation and cooling. Or in that nook near the foyer

[Guest niterida]

Your room is too small for what you are proposing.

 

I have a 6.25 x 4.3 (finished internal dimensions) HT and it is only just wide enough for 3 seats and only just deep enough for 2 rows. Yes you can physically fit more in but it will be a major compromise. Your room is smaller and you plan on making it smaller again with your internal soundproofing walls, so I would suggest you make the plan suit the room, not the other way around.

 

I have a 3600mm wide 2.35:1 Acoustically Transparent (AT) screen which sits 200mm off the front wall and then I sit 3400mm (to the ears) from the screen. This is just about perfect and no-one has ever complained of the scrfeen being too big, too close or causing neck or eye strain. I DIY'd the screen and it cost me $80 - A bit of wood from Bunnings and a bit of Spandex from Spotlight

 

I run a 7.4.6 Atmos system with all 13 speakers being identical 30yr old 5" bookshelfs and it sounds amazing and I run it almost to 0MV (it does start to struggle at that volume but I am working on improving that).

The room is built from brick (thats how we do things in WA)  and has almost no acoustic treatments - just carpeted floor and 55mm rockwool insulation on the back of the AT screen and it sounds great. The soundstage I get when running in stereo is unbelievable - it sounds really wide and like the centre, surrounds and heights are still producing sound and you have to physically put your ear to them to confirm they are silent. After reading a lot of research by Dr Floyd Toole and others I believe this is because I don't absorb the first reflections and due to the positioning of my L&R (800mm from the front wall, 400mm from the side wall and toed in to meet at a point about 600mm behind the MLP (Main Listening Position - the centre of 3 seats)  so don't go blindly rushing in and spending money on acoustic panels that may not be necessary. Finish the room, invest in a proper calibrated mic and REW software and learn how to use it and work out exactly what you need to do to solve any acoustic issues. Note that I have yet to do that as I have not finished my setup completely so hopefully when I do it sound even more amazing.

 

I have a single 3 seater and the side surrounds at the recommended 90deg were too close to the outside seats and were far too overpowering (hotspotting). Which is why I said the room was too narrow - and they are approx  900mm from the outside seated persons ear which is more than most recommendations, but to me is not enough. I modified my 3 seater to remove the arm rests between the seats and now the outside ears are closer to 1200mmm from the side surrounds and this is a huge improvement. Also since you are running 7.x.x you can move the side surrounds slightly forward of the seating (not more than 10deg) and this adds to the front soundstage, puts the closest listeners off-axis which reduces the SPL reaching them and reuces hotspotting even further.

Some people recommend raising the side surrounds and aiming them at the furthest listener but I wouldn't do that with Atmos unless you absolutely have to.

 

The rear seating you really should move away from the rear wall but if you position the front seating closer to the screen like mine,  this is easily achievable. Make sure the rear surrounds are up high enough to clear the rear seated heads and reach the front seat ears. It helps to use low back seating for this - typical HT seats are a misnomer and not really suitable for HT use because of the massive headrests that block most of the rear sound !!

You may also want to consider a 2nd set of side surrounds (fed with the same signal as the normal side surrounds) to help with the immersion of the sound for the rear seats. How often will you be using the rear seats - I was going to run 2 rows but rarely have more than 3 people so went with a bar setup behind the first row with just some bar stools for the 'nosebleed section'. This could save some money for more important items to start with.

 

The room is definitely long enough for .6 Atmos so you should definitely set it up for that. The Atmos speakers should be the most capable you can afford and ideally match with your bed level speakers. Angled in-ceiling or angle mounted bookshelfs aimed at the listening positions. If you go .6 and use bookshelfs you may find an improvement if you turn the Top Middles 90 deg sideways (so the tweeter is on the L or R rather than the top of the woofer) so their dispersion pattern covers both rows of seats.

 

Depending on your ultimate requirements for soundproofing you may find that just green gluing 2 layers of soundcheck plaster board or adding a middle layer of OSB may be enough for you. And note that you green glue the boards to each other - not to the framing. Although I have no experience with this due to my brick walls and this is only what I have picked up from reading other forums.

[Liamt]

Thanks Peter for your suggestions. Will certainly look into the rack and fire doors. I can incorporate two doors.

 

The chipboard on the floor is also a great idea that I will use. 

36 minutes ago, Peter the Greek said:

BTW - the speakers are woefully inadequate for a room that size

 

Do you mean they are too small ? Not enough power ?

thanks

[Guest niterida]

18 minutes ago, Liamt said:

Thanks Peter for your suggestions. Will certainly look into the rack and fire doors. I can incorporate two doors.

 

The chipboard on the floor is also a great idea that I will use. 

 

Do you mean they are too small ? Not enough power ?

thanks

They are low sensitivity and will need roughly double the power that most speakers need to reach the same SPL.

I would say that 88-90db is 'normal' sensitivity and these are 86.5db so roughly 1.5 -> 3.5db less sensitive. Each 3db of reduced  sensitivity needs double the power to produce the same SPL.

 

You will need approx 75w peak to reach 105db peak (reference level) with 7 of these speakers in your room.

Your 8500 will probably provide enough power for this. But you may benefit from quality external amplification.

 

I would recommend getting another of the same towers for your centre if you go with an AT screen, or at very least the equivalent (or better) PMC bookshelf. Otherwise grab the centre and bookshelfs you have been offered.

Use the ELAC as Atmos and buy 4 more or get rid of them and get more suitable Atmos speakers.

 

I didn't really mention it in my first post but going from towers and large bookshelfs from the same manufacturer but slightly different series, to all 13 identical small bookshelfs (from the same manufacturer as the towers and large bookshelfs) was a significant improvement in the soundstage and immersive soundfield. It became seamless and it is really hard to pick sounds as coming from a distinct speaker. So if you can match all your speakers it will (or at least should) sound better.

[hopefullguy]

bet you thought it would be easy op?

 

see what you need to do is have a plan.. will it be as involved as A or simplified as B has suggested. make your own screen or buy, change your speaker set or start with what you have and DO NOT buy anything more to see how it all fits together.. how high should i make my riser? with a single step or without (my first diy rise had no step, after 6 months recycled the pieces and made it higher with a step). you do not have to get things perfect from day one...it will cost you a fortune to do that.

 

treatments... my room was a "clap" festival so i diy panels, researched sound absorption and in the end did my own thing that suited my room, in stages to a point i like.. how the hell you can spend many hundreds before even setting things up is beyond me. but some do and they are happy (they have to be as they spend the money:-)

 

get the building side of things right (but in your allocated budget) then worry about filling it with stuff... so stop buying. well thats just my suggestion.

 

good to hear from Niterida again (that spandex caused some interesting posts, but it worked for him)... 13 book shelf speakers eh? since my early starts i now feel 2 books as fronts and a biiig centre and 2 big subs is the way to go if you cant get 3 floorstanders/books all the same model and 2 big subs behind an A/T screen.

[Irek]

Sound separation walls are explain on CSR gyprock website, but I wouldn't go with that internal frame, the room is not that big. Try to use acoustic insulation between studs and 2 or 3 layers of plasterboard or firecheck. 

PMC are quite famous of having high level of details. With good amp just those 23s can fill up your room easy with music. I would go with PMC only and 5.1.2 maximum (including PMC centre and 2 ceiling).

If you ever try power amp and set all speakers to large/full range you might want to sell subwoofer. Those PMC have strong and deep punchy high quality bass (with good power amp). 

[Guest niterida]

8 hours ago, Irek said:

If you ever try power amp and set all speakers to large/full range you might want to sell subwoofer. Those PMC have strong and deep punchy high quality bass (with good power amp). 

Ah no - unless your speakers go down to 20hz you will always need a subwoofer for Home Theatre

[Guest niterida]

8 hours ago, Irek said:

 5.1.2 maximum (including PMC centre and 2 ceiling).

 

Also no - 2 Atmos speakers is not enough for 2 rows of seats and the length of his room would be better with 6, especially since he already has the processor to do 6

[hopefullguy]

i thought "normal" atmos was 4 speakers... its a disease

 

yes subs. i read some reviews on those speakers and bass was not the strong point. also to optimise bass you need to be prepared to put subs where they perform the best, front speakers go in fairly set positions.

 

from experimenting and readings 2 rows of seating can benefit from 2 rows of side surrounds.. but i went back to a single between the 2 rows (good enough for Gene at audioholics good enough for me).. if using 2 sets seems they should be powered by 2 amps. gets messy imo.

 

budgets not mentioned for anything so far.

 

riser height.. dont go too low

 

seating.. i never liked those big HT chairs, the backs will cause sound problems as they block the line between your ears and the speakers. they also take up a lot of room when reclined.. most commercial cinema seating is upright and low backed for a reason.

[Liamt]

Budget is kind of flexible...unless my wife is asking and then it's very very low

 

What riser height do you suggest hopefullguy?

[Guest Peter the Greek]

16 hours ago, Liamt said:

Do you mean they are too small ? Not enough power ?

thanks

You'll likely find significant variance in response seat to seat. Possibly the MLP will be ok, but I'd put money on the others being rubbish. You'll also get a big drop off of HF response between rows.

 

Then there is the little matter of them not publishing off axis response charts. My primary bug bear, and if you engage Quest I will guarantee that Shawn wont be happy about it from an acoustic design perspective. Plus all three LCR's need to be the same - end of story.

 

This type of speaker is really designed for limited 2 channel use with one or two seats in a small room. Not a large home cinema - and your's is. 6m in length isn't small.

 

Can you back out of the purchases? I would, wait until the room and or room design is finished.

[hopefullguy]

agree with peter.. can you back out?

 

riser.. floor to top of first wood step is 200mm.. then underlay/carpet on floor step, so basically 200 mm high.

 

then from top of step to riser top i made it 120mm. so total height is around 320 from floor plus covering.

 

i should have made the distance from top of step to top of riser 150mm or do 200mm as per the floor/step but that seemed too much. doing again i would go with 200/150 combo

Edited January 16, 2020 by hopefullguy

[hopefullguy]

just an opinion.. fill the riser with insulation and make it sturdy. reason is i firmly believe in 2 subs with 1 at the front (as centre as possible) and 1 on the riser behind the 2nd row (as centred as possible).. the riser may take a bit of a beating so needs to be sturdy. do it yourself and enjoy the process more imo