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Discussion Starter #1
OK this may sound a bit crazy but here it is ... over in the Home Theater construction forums at AVS the idea of using the riser for the second row of seating as a sub enclosure came up.

The riser I am planning for my theater will be 144" X 80" X 12" and I already own a SDX15 that Mike so kindly modeled for a 13 cu ft enclosure ... I have not built it yet because the first priority is completing the theater/basement first

Now because these risers are not normally taller than 10 to 12 inches there would be some limitation if using front or rear firing drivers in terms of size

You could I suppose use a array of smaller drivers but I suspect you would not get real low frequency response like the larger 15" and 18" common in sub builds on this forum

You could have the driver facing up but then it will always be subject to damage from someone stepping on it

There may be a way to have the driver downfiring within the sub which is what came to me as the most practical but I dont have the knowledge as to how to design such a beast

So please weigh in with any and all opinions as to whether this is possible ... mostly interested if I can use my SDX15 and/or maybe add a Mal-X later on ( design chamber for it and when theater is complete I can add as funds allow )
 

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You could have the driver facing up but then it will always be subject to damage from someone stepping on it
You could maybe use a (strong) protection grill??

Or maybe downfiring with less riser height, but raised from the floor...
 

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With a subwoofer in a riser you get all the problems with having near field placement. Doing a custom sub and enclosure also will be tricky because subs are not built and designed similar to a riser. It would help if you had ports coming out of it. Have you seen Sonnie's build? That is a good example of how it could be done proper. Also you will need something along the lines of at least a pair of 18" subs and probobly want to pull seperate duty for powering them depending on what you use. You might even consider going up to a 20" or more size woofer if you wanted if you have a large enough area to work with. It needs to be large enough already and larger than your average sized riser.
 

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Discussion Starter #4
I am open to any and all ideas so keep them coming

I am nervous about the driver facing up because in order to avoid locate it under where the recliners are then that just leaves the space between the front of the recliner and the first row where the foot traffic would be ... if I build a grill strong enough to protect it will it have a adverse effect on the sound ??

which begs a question ... would it matter if the driver was up-firing under a recliner in terms of affecting the sound in a adverse way ? ... that would solve the issue of protecting the face of the driver

the riser has a volume of almost 2300 liters so size should not be a limitation ... because I was leaning towards downfiring I figured porting would be necessary ... maybe the driver could be mounted on a 45 degree so it fit under the riser and a large rectangular front port of equivalent size to the driver face be made at the front or rear of the riser ( would you have the port firing into the back of the first row or back of the room - riser is 5 feet away from back of the room ) and then a normal port for LLT ???

what problems can I expect of near field placement ?


do you have a link to Sonnie's build ?
 

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I am open to any and all ideas so keep them coming

I am nervous about the driver facing up because in order to avoid locate it under where the recliners are then that just leaves the space between the front of the recliner and the first row where the foot traffic would be ... if I build a grill strong enough to protect it will it have a adverse effect on the sound ??
A grill is not going to impact the sound whatsovever.:bigsmile:

which begs a question ... would it matter if the driver was up-firing under a recliner in terms of affecting the sound in a adverse way ? ... that would solve the issue of protecting the face of the driver
Firing the subwoofer up should not make any difference but usually you want the enclosure to follow the opposite direction of the driver, in this case that would be down, not leaving much room between the floor and woofer.

the riser has a volume of almost 2300 liters so size should not be a limitation ... because I was leaning towards downfiring I figured porting would be necessary ... maybe the driver could be mounted on a 45 degree so it fit under the riser and a large rectangular front port of equivalent size to the driver face be made at the front or rear of the riser ( would you have the port firing into the back of the first row or back of the room - riser is 5 feet away from back of the room ) and then a normal port for LLT ???
You might try firing them from the corners. Firing them under an object is going to limit the movement of air, and that is always a bad idea to limit air movement of the sub unless it is implied in the design such as your horn type subs for example.

what problems can I expect of near field placement ?
Low subwoofer frequencies require the room to interact with it if a flat response is your goal. There will be a certain amount of room gain in each room and when you are sitting at the point from which the sound will have left the sub, then became excited by room modes. If your sitting right next to the sub it will be easier to hear room modes.


do you have a link to Sonnie's build ?
http://www.hometheatershack.com/forums/home-theater-design-construction/15973-cedar-creek-cinema-ii.html
 

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Just throwing this out there a a WILD idea but would be fun. Build a sloped floor and make the whole floor and riser a horn. :coocoo: The slop would be the throat of th horn and you could have it terminate at the front of the room.

Matt
 

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Discussion Starter #8
OK ... so it looks like Sonnie is building the sub enclosure above the riser and then porting down and through to the front of the riser ? did I get that right in the drawings ?
 

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Discussion Starter #9
Here is the general layout of the room to give a idea of some of the limitations ... bathroom on the left requires me to leave a hallway behind the riser ... that also means that I cant build a sub on the back of the riser like Sonnie did ... it has to be built inside the riser itself

 

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Discussion Starter #10
Matt ... not sure the sloped floor idea would work ... look at the sketch above to see if you still think it is possible
 

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Discussion Starter #11
A grill is not going to impact the sound whatsovever.:bigsmile:
still not sure about people walking on top of my drivers :)



Firing the subwoofer up should not make any difference but usually you want the enclosure to follow the opposite direction of the driver, in this case that would be down, not leaving much room between the floor and woofer.
I dont see how I can locate a larger driver with the 12" height limitation ... 3 choices would be up firing , down firing or maybe 45 degree


You might try firing them from the corners. Firing them under an object is going to limit the movement of air, and that is always a bad idea to limit air movement of the sub unless it is implied in the design such as your horn type subs for example.
Are you thinking of them firing up or to the sides in this scenario ?



Low subwoofer frequencies require the room to interact with it if a flat response is your goal. There will be a certain amount of room gain in each room and when you are sitting at the point from which the sound will have left the sub, then became excited by room modes. If your sitting right next to the sub it will be easier to hear room modes.

I do plan to run at least one sub maybe 2 at the front of the room ( already own a Axiom 600 ) but can I use bass trapping and EQ to even out the room response ?
 

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I dont see how I can locate a larger driver with the 12" height limitation ... 3 choices would be up firing , down firing or maybe 45 degree.
If we are not talking about custom fitting the riser for the subwoofer, I'm almost certain they will be issues. These things really need to be designed into the riser itself. For example, there will need to be boards running iniside that will have giant holes in them to break up standing waves with large thick internal bracing. There will need to be no insulation inside. It should also be decoupled from the walls and if need be a wooden floor (which I don't think you have). Putting it against a wall is going to be difficult to deal with because the purpose of the enclosure is support all that movement and it needs to be very sturdy. If your placing a 12" driver on a 12" riser that is not possible because the lip around the driver must be attached around the outside of the hole and there will need to be about a 1" clearance around that as well for support and if you want to add a grill. Doing a retro-fit is something I don't think I can help design with the best results, but I don't know whats inside of it.

Are you thinking of them firing up or to the sides in this scenario ?
Up-firing would be best. I'm not even sure I understand how down firing would work for a riser. :dunno: To the sides would be the better option, but not necessarily at walls. That would take some extra clearance.

I do plan to run at least one sub maybe 2 at the front of the room ( already own a Axiom 600 ) but can I use bass trapping and EQ to even out the room response ?
Equalization or room treatments can never substitute for proper sub placement, but does not mean that it should be ignored if proper placement were not an option. It will still help, just not as well as proper sub placement.
 

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Discussion Starter #14
If we are not talking about custom fitting the riser for the subwoofer, I'm almost certain they will be issues. These things really need to be designed into the riser itself. For example, there will need to be boards running iniside that will have giant holes in them to break up standing waves with large thick internal bracing. There will need to be no insulation inside. It should also be decoupled from the walls and if need be a wooden floor (which I don't think you have). Putting it against a wall is going to be difficult to deal with because the purpose of the enclosure is support all that movement and it needs to be very sturdy. If your placing a 12" driver on a 12" riser that is not possible because the lip around the driver must be attached around the outside of the hole and there will need to be about a 1" clearance around that as well for support and if you want to add a grill. Doing a retro-fit is something I don't think I can help design with the best results, but I don't know whats inside of it.
the riser is not built yet so I am open to designing it to work with the sub ... I am thinking that the sub enclosure is just part of the construction of the riser itself ... the entire room ( walls and ceiling ) is soundproofed with DD/GG and rsic clips/hat channel on the ceiling ... the riser was not going to touch any walls and the floor is Delta FL covered in 5/8 T&G OSB ... if you look at the sketch I posted the riser is close to the side wall but not touching it and is 5 feet from the back wall

On the subject of 12" drivers ... if I were to make the riser taller by a couple inches to accomodate that driver on the sides ... is it reasonable to assume that I could possibly get a 15 hz tuning using multiple 12" drivers ? ... if so what 12" drivers would you guys recommend ?

Mike - The riser will have 4 recliners spread across the back portion ( already bought them so cant change that ) and I need every inch of that space because I have to make space beside the riser for a small hallway on the right to get to the front row of seats ... that is why I was asking earlier about up firing under the recliners
 

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The up firing idea is all fine until someone drops some popcorn between the chairs, or any other crud and it somehow finds its way under the chair/couch and falls onto the woofer...Or worse, an entire glass of liquid. Sugary pop does wonders for woofer cones.
-IMO, upfiring is an awful idea, but I also have a toddler running around-

45degree downfiring along the edges of the riser could work and would nearly eliminate them from getting kicked like what might happen to a normal 90deg mounted driver.
 

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Discussion Starter #16
I did not think of the crud getting in there on a upfiring driver but yeah that would suck

So basically a side firing or something on a 45 degree would work I guess

can I use a bunch of 12" drivers to get the same spl and low tuning of lets say a Mal-X ?
 

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What about using a bass shaker type of system to give the sensation of bass. Then run a small sub someone else in the room to produce audible bass?

Without measuring the room to determine relection points it will be tough to say whether or not a sub mounted directly under your chair in a large room will actually sound good.

Brad
 

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Discussion Starter #18
I actually prewired for bass shakers already ... the thought of using the riser as a sub is the new part ;)


Anyone have a opinion about multiple 12" drivers in the riser to equal a Mal-X for SPL and low tuning ?
 

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Discussion Starter #20
I am open to suggestions

I had planned to get a EP2500 for the SDX15 driver that I already have ( it is probably too much power for just one SDX15 but when funds were available I had originally thought of adding another down the road or possibly a Mal-X )

you modeled the box for me already in another thread for a LLT design using the SDX15

so to power some 12" subs in the riser what would you suggest ?
 
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