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post #1 of 4 Old 05-19-2019, 06:27 PM - Thread Starter
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Building a home theatre - some questions..

Hey all, a few questions around building your cinema room from scratch (new house, currently architecting). I still have flexibility in dimensions, sub layout, and might have to make some choices before the room exists in reality.

1/ I have a SVS SB13Ultra - 13.5", 1000W powered sub. How do I calculate the SPL at sitting location? The - specs page - is uninfornative (doesn't mention sensitivity for example)

2/ I'm thinking of adding 2 subs to 'cover' the 10x6m-ish room well and have an entry into multi-subbing. Roughly, what would be sufficient for the 115dB SPL at listening? Handwavingly, would 1x13.5 and 2x 12" suffice? (e.g. Dual SB2000 - of course I realise this depends on the above #1 question =)

3/ My amp (Marantz 7010) has 2 subwoofer outs. How would one wire this up? Should put my 13" on one, and 12"ers on the other channel (I think they have a 'through', line-out?), or split one of the sub-outs into two signal cables?

4/ I know positioning the subs is a massive topic, but happy to hear any 'first attempt' setup suggestions. Reason I ask: I'm tempted to put the signal cables to the subs into the walls, but that'd mean I have to predict where the subs will be! I'd even be happy to create a few more cable spots just to cover a few likely options. What's a good 'common layout'? I'm thinking 13.5 slightly off-center under the screen, one 12 on left wall, one 12 on right wall (but different spot, not same distance from screen)..

Looking forward to any thoughts on the subject, incl anything I missed or should consider... Am I thinking in the right direction?

Kodi Streamer -> Marantz 7010 -> Nord 500DMUP -> Quad 2912

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post #2 of 4 Old 05-19-2019, 07:51 PM
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Figuring out sub output at a listening position requires some guesswork since output measurements generally use standards where the mic is 1 or 2 m in front of the sub, with no boundary gain. In a room you typically sit farther, so you will lose volume due to distance, but you will gain a measure of output from room boundaries. For the SB Ultra, I would look at the data-bass numbers and assume something close to those numbers in room. What that means is you should get 115 db from ~40 hz on up.


For a goal of 115 db, you should set a frequency range, do you want 115 db starting at 20hz, 16hz, or something else?


Your room dimensions are quite large, personally I'd be wanting ported. My personal preference would be two up front, and one nearfield. Ideally 18" ported if you could swing it, or 15's would be good too. Running sealed you could hit your output target with midbass, but it would require a lot of subs and power to get to 115 db at 20hz.
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post #3 of 4 Old 05-20-2019, 03:51 AM - Thread Starter
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Originally Posted by dpc716 View Post
Figuring out sub output at a listening position requires some guesswork since output measurements generally use standards where the mic is 1 or 2 m in front of the sub, with no boundary gain. In a room you typically sit farther, so you will lose volume due to distance, but you will gain a measure of output from room boundaries. For the SB Ultra, I would look at the data-bass numbers and assume something close to those numbers in room. What that means is you should get 115 db from ~40 hz on up.


For a goal of 115 db, you should set a frequency range, do you want 115 db starting at 20hz, 16hz, or something else?
Ha - I don't even know. I haven't seen that level of specificity from the THX spec, it just says '115dB SPL at listening' as far as I can tell.
But indeed clearly if I want that at 1Hz I probably need a few garbage trucks driving around on a platform..

Honestly, I'm not such a bass-fanatic that I need it deeper down than 20. (of course hoping for roll-off into the lower regions..)

Quote:
Your room dimensions are quite large, personally I'd be wanting ported. My personal preference would be two up front, and one nearfield. Ideally 18" ported if you could swing it, or 15's would be good too. Running sealed you could hit your output target with midbass, but it would require a lot of subs and power to get to 115 db at 20hz.
Good point, ported typically is a little louder but also less controlled. (although I hear many people say that 'control' and reproduction precision is really not that much of a deal in bass-land.. or am I blaspheming here)

Still.. 15/18 inch are huge.. I might have to compromise on size and accept lower boom..

Kodi Streamer -> Marantz 7010 -> Nord 500DMUP -> Quad 2912
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post #4 of 4 Old 05-20-2019, 04:28 AM
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Originally Posted by puntloos View Post
Ha - I don't even know. I haven't seen that level of specificity from the THX spec, it just says '115dB SPL at listening' as far as I can tell.
But indeed clearly if I want that at 1Hz I probably need a few garbage trucks driving around on a platform..

Honestly, I'm not such a bass-fanatic that I need it deeper down than 20. (of course hoping for roll-off into the lower regions..)



Good point, ported typically is a little louder but also less controlled. (although I hear many people say that 'control' and reproduction precision is really not that much of a deal in bass-land.. or am I blaspheming here)

Still.. 15/18 inch are huge.. I might have to compromise on size and accept lower boom..

So if you set 115 db @20 hz as a goal and look at the data bass numbers, the SB13 Ultra can produce 96.5 db clean at that level, by comparison the PB13 Ultra can produce 110.6. Adding a second of each will add 3-6db, let's say 5 db for simplicity, that means two SB13's will give you ~101.5 db and two PB13's around 115.6 and you reach your goal. You get the idea.


It is true that ported and sealed often have a different character in room, and sealed is generally preferred for music only, though good ported subs can be made to sound just fine, maybe with a little extra effort. For movies only, the character of ported is often preferred.
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