Sub Conundrum - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 15 Old 12-29-2015, 10:22 AM - Thread Starter
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Sub Conundrum

So back in October, my wife and I moved into our new home. The basement is completely unfinished with 9ft ceilings. After my office, bathroom, bar and storage space, I end up with a theater with a finished dimension of 16.5'x22'.

I already have 4 SI HT18s in 4cf flat packs that I am currently assembling. My wife won't let fridge sized ported or folded horn cabinets fly as none of the speakers or subs will be concealed.
The conundrum comes from my planned layout vs ideal layout...
The front stage will allow for placement of the 4 18s to be equidistant from the MLP across the front. Rear won't allow for the footprint of the 4cf flat packs with the rear room entry and the desire to have walkways on each side of the seating.

That being said, I have become enamored with the idea of adding subs to the rear of the room (originally thought about tactile transducers in/on the risers but the wife won't accept external mounting, seating hasn't been decided on and I don't want to mount them to seating anyway and won't know where to mount them under externally until the seating is purchased and received).

The thought is I can do an angled vertical enclosure to house a pair of 12s in each rear corner of the room and not lose much of the walk way and still keep my wife happy aesthetically.
My thought is doing 2 Infinity 1262ws in each corner at the rear sealed and picking up another inuke to run them.

I know mixing sealed and ported enclosures is always a suspect proposition but had thought about using my current SVS cylinders back there. The more I think about it, the less that idea seems to float not to mention the challenge of eqing the mix of ported and sealed subs.

So am I off base in considering 4 sealed 18s across the front and 4 sealed 12s in the rear corners? It allows for a wife approved aesthetic and allows me the sub quantities I desire...
I guess what i would like from you folks is to shoot holes in my ideas. Or stroke my ego and push me forward with it.

And...go!

I keep confusing my intentions with my abilities.
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post #2 of 15 Old 12-29-2015, 11:07 AM
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Baffle wall, 8 IB 18s in manifolds at the four 1/4 locations of the front, and nuts to subs in the back.
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post #3 of 15 Old 12-30-2015, 11:48 AM - Thread Starter
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As much as I like the idea of baffle wall and IB subs, 2 walls are concrete foundation walls and the third is the primary load bearing wall for the floor joists. And the 22 foot length of the room is maximum considering the egress window that comes into play at 23' 6" and I already have to plug 1 egress window opening as it is.

Seating is non-negotiable as the wife insists on 2 rows of 4 (I honestly don't think we even have 6 avid movie watching friends). Screen size would have to be sacrificed if I shortened the length of the room too...

Honestly, the rooms I have experienced with front and rear subs have made for, what I felt, was a much more encompassing experience. We all know that bass/sub-bass is omni-directional but localization is very real.
I am hoping to avoid that as much as possible.

Hopefully the 2 attached pictures will give an idea of what I am working with.
The black triangles in the theater would be where I would do the stacked 12s...
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I keep confusing my intentions with my abilities.
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post #4 of 15 Old 12-30-2015, 04:35 PM
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congratulations on your new home and your theater plans.


putting some sealed subs in the back corners is fine, so long as you have them on a separate time delay (being closer, they probably need more delay).


the larger concern is where your seating is located relative to your screen. just eyeballing it, it looks like the front row is going to be too close to the screen.


I may have missed if you said riser or not, but the back row is also directly behind the front row (not staggered). not sure if that creates a problem will seeing your screen or not. to the extent that it is possible, you may want to mock up the screen on the front wall and move some chairs around where you are planning to put the theater seats just to get a "feel" for it. my guess is the whole thing will feel better moved a little further back.


putting the subs equidistant from the seats may not be as important as figuring out how those locations are likely to interact with your room. if your subs are 3-4 feet from boundaries, that can create cancellations in the midbass that depending on what you are trying to accomplish can either be a good thing or not.


some big bass absorbers wouldn't be the worst thing either. generally a 'softer' room is better for minimizing modal resonances and cancellations than a rock solid room.

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post #5 of 15 Old 12-30-2015, 06:00 PM
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My mistake. Can't delete

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post #6 of 15 Old 12-30-2015, 08:31 PM - Thread Starter
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@goonstopher I think you're in the wrong thread...
@LTD02 Thanks for the input.
There will indeed be a riser. First row is 6 inches above the floor and second row is an additional 12 inches.
The riser is also going to be built as the primary (read most likely the only) bass trap for the space. The walls will be a mixture of mass (DD), absorption and reflection panels. There will also be a sand filled stage that the front subs will reside on.

The seating/layout is just a rough sketch using the limited resources of Visio. I have the measurements somewhere and my first row was determined to be ideally placed for the screen size so we should be good there.

I fully anticipate using a combination of Audyssey (XT32), MiniDSP and REW to get things dialed in when the time comes.
My ultimate goal is and overall balanced quality sound with plenty of shock and awe factor as well.

I keep confusing my intentions with my abilities.
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post #7 of 15 Old 12-30-2015, 09:17 PM
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Could you build triangle shaped cabs for the 18s and put those in all four corners? Maybe add two more so you don't waste your current cabs. They can be made into pretty small triangles.
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post #8 of 15 Old 12-30-2015, 10:29 PM
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ok, sounds like you are on top of it.


just a couple points. if by dd, you mean double drywall, that may be going in the wrong direction for sound *in* the room. the more solid the boundaries, the sharper and more pronounced the modal peaks and dips will be. ideally, you want the walls to be lossy at low frequencies (flimsy). mass is good for keeping sound from leaving the theater. a very useful tool for seeing some of these effects is the room simulator in room eq wizard (rew). very easy to specify a basic room, place some subs and a listening position, and see the response. the effect on frequency response can be seen by changing the absorption/lossiness of the boundaries. the rear wall is typically the most problematic.


filling the stage with sand is probably unnecessary. there was an a-b comparo somewhere with decent measurements, but i don't recall who performed that test offhand. if you want to fill it with sand i don't think it will hurt anything.
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post #9 of 15 Old 01-01-2016, 09:11 AM
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Quote:
Originally Posted by Samps View Post
Could you build triangle shaped cabs for the 18s and put those in all four corners? Maybe add two more so you don't waste your current cabs. They can be made into pretty small triangles.

I like this idea as well. Having four subs up front may be just as good as two subs up front. If you stick with the four, then I would go ahead and build the 12" subs in back with those triangles as you mentioned in the corners.
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post #10 of 15 Old 01-01-2016, 11:31 AM
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Quote:
Originally Posted by murphy2112 View Post
Quote:
Originally Posted by Samps View Post
Could you build triangle shaped cabs for the 18s and put those in all four corners? Maybe add two more so you don't waste your current cabs. They can be made into pretty small triangles.

I like this idea as well. Having four subs up front may be just as good as two subs up front. If you stick with the four, then I would go ahead and build the 12" subs in back with those triangles as you mentioned in the corners.
That would be a waste of the 4 DIYSoundGroup flatpacks he just bough and built. Doubtful he can find a buyer for all 4 without losing most if not all the cost of those...
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post #11 of 15 Old 01-01-2016, 11:52 AM - Thread Starter
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Not to mention the cost of HT18D2s...well shipping that is as there are a few available around the country but the cheapest shipping for a pair of them has been $118.

I like the triangle enclosure idea...I really do but the logistics of making it happen are...a challenge. Plus it factors out to be a much more expensive option.

I keep confusing my intentions with my abilities.
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post #12 of 15 Old 01-20-2016, 06:35 AM
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Soooooooo......................................... ......


Whadidja do?

My Setup | Custom MiniDSP Build | FS: If its For Sale, find it all (here)
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post #13 of 15 Old 01-20-2016, 07:43 AM
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Quote:
Originally Posted by ZLTFUL View Post
Not to mention the cost of HT18D2s...well shipping that is as there are a few available around the country but the cheapest shipping for a pair of them has been $118.

I like the triangle enclosure idea...I really do but the logistics of making it happen are...a challenge. Plus it factors out to be a much more expensive option.
If you still don't have a solution and need help with a custom triangle enclosure, my Dad is in Marshalltown and might be able to help out when he gets back to Iowa in mid March. We recently did some custom ported triangle enclosures for @murphy2112

Check out my End-Table Marty Build
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post #14 of 15 Old 01-20-2016, 09:14 AM - Thread Starter
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While I appreciate the offer, I think I have made a decision in this regard.

Plus I have a full wood shop at my disposal and over 20 years of woodworking experience in both hobby and professional regards to help me along. Hehe.

That's not to say that I wouldn't go that direction maybe and wouldn't hesitate to reach out to you for advice...just saying I could probably manage if I actually got the motivation together to do so. Heh.

I keep confusing my intentions with my abilities.
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post #15 of 15 Old 01-20-2016, 09:40 PM
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Best $ per fun I have spent on my 6 year so far theater room are $40 per seat butt shakers not including their amplifer..... even over my projector. The 2 sealed ftw21s are also indispensable. Bought two more for nearfield, but my cheap butt shakers still rock! And they rock when the wife does not want the rest of the house at Earthquake levels.
For the same effect the 2 current 21s have to be at about 1 to 2000 watts each and that has big effect outside the theater room. Don't like to live without it either but it was not hard to build 3/4 inch x 6 " solid oak hardwood boards into the seats to mount the arse wigglers.... loooove them long Tim! Solid oak is better than plywood for transferring energy. Don't forget wiggly feet for seats either!
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