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Old 5th February 2008, 03:34 AM   #1
Newbomb is offline Newbomb  United States
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Default Building a sub into theater room floor.

I am tasked with building a sub into the floor of my theater room. The room is 21 (l) x 15(w) x 9.5(h). The raised floor takes up the back seven feet of width, and is raised by a mere seven inches. I am wondering what sort of problems I might encounter.

Ideally, I would like to build a down-firing, vented enclosure with the vents aiming outward along the 'stair' face. I would then cut a decent sized rectangular slot to allow for driver air movement - also along the face of the stair.

There are several items of concern. The box shape will need to be _very_ shallow and long. A couch sits along this step face, and I would like the vents (two) to be just outside the couch edge of about 6 feet. If the enclosure would be too big, I could always make two of them, or vent it on just one side (and move it to one edge).

A five inch depth would give me about two inches of air in front of the driver. This should be enough, but is probably pushing it. I would also possibly need to recess the magnet into the box structure (IE router a section down a bit) to get extra depth.

I have looked at the new SB Acoustics SB29NRX75-6 10" driver. ~ 5 inches deep. A few dayton models will also fit. Any recommendations? I am really looking for quality/accuracy. I don't need to rattle my foundations - but that would be OK too.

Thanks,

Todd
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Old 5th February 2008, 04:02 AM   #2
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You lost me, where are 10" drivers going to fit in a 5" high space? By 'down-firing, do you mean mounted face up in the floor behind the couch?

GM
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Old 5th February 2008, 04:11 AM   #3
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Look at the the Tang Band WT-1427B 10" Neo Subwoofer. It's designed to fit inside 4" walls so it will fit into a 5" space. . PE has a sale on them for $60. They have been getting a lot of great reviews. I am making a DIY sub with on of these myself.
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Old 5th February 2008, 04:25 AM   #4
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Quote:
Originally posted by GM
You lost me, where are 10" drivers going to fit in a 5" high space? By 'down-firing, do you mean mounted face up in the floor behind the couch?

GM

The elevated floor is 7 inches total depth - essentially a raised seating area. The SB driver is 5 inches deep. The driver would fire downward, mounted into the raised floor near the stair edge. It would be face down, firing into the rooms floor (concrete). That is where there would be a 1.5"-2" gap for air movement.

Think of it as a standard, down-firing sub enclosure that is only 7" total height, but made as part of the floor (and a quite a bit wider and longer to make up the needed enclosure volume).

Todd
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Old 5th February 2008, 10:20 AM   #5
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Default Other locations?...

You may want to consider a wall instead, or even an infinite baffle driver or two in the ceiling(if there is an attic above). Might open up a little wiggle room in your planning. Some folks are claiming some decent results using Aura's shakers(pic) on their HT seating or couch to enhance the bottom end(no pun intended). Good Luck -discreteouts
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Old 7th February 2008, 02:38 AM   #6
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Keep in mind that most subs have vents on the backside. If you recess the magnet, you probably will block the vent. With a blocked rear vent and only 1.5-2 inches in the front, I'm not sure how the sub would perform. What I'm thinking is try tilting the driver from down firing to side firing as much as you can. It will probably end up at ~45 deg angle (half facing down and half to the side). That should give you more clearance and plenty of air for the sub to move.
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Old 7th February 2008, 02:37 PM   #7
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Similar advice from the cheap seats. I am building a 12" tall enclosure for two 15" subs that is almost 7 ft wide. (My room is only slightly larger than yours). I am tilting the subs about 30 degrees and firing them at the floor. This is basically a 4th order band pass design. I have used it with great success before.

The neo 10" was the first thing that came to my mind too. You could do it in a sealed rear chamber and just calculate the distance from the sides where the ports will be located.

another thought that came to mind was the TB 4" subwoofers at PE. I haven't used these myself, but I have a very similar woofer in a "boxed ht setup" that worked very well. As small as these speakers are, you could mount them vertical in that space and do the box the appropriate size without too much calculation. You could also do quite a few of them if you are looking to get more crank from the space.

Keep us posted
Robert
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Old 8th February 2008, 02:05 AM   #8
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Default platform woofer

Instead of firing into the platform you will be sitting on (if I read you right) why not take two cabinets, and attach them directly to the platform. The bottom of each would be sealed to, but open to the platform area. Use the volume of the raised area as a pseudo infinite baffle, with the drivers mounted on the cabinets.

It sounds like you have sufficient room.

Good luck.
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Old 8th February 2008, 03:08 AM   #9
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Default Re: platform woofer

Quote:
Originally posted by homebuilder
Instead of firing into the platform you will be sitting on (if I read you right) why not take two cabinets, and attach them directly to the platform. The bottom of each would be sealed to, but open to the platform area. Use the volume of the raised area as a pseudo infinite baffle, with the drivers mounted on the cabinets.

It sounds like you have sufficient room.

Good luck.
I have considered that. However, there are internal braces supporting the structure. It is large enough for an infinite baffle, but I may have to tear things up a bit more than I want too to open it up internally.

Plus, the real conundrum is that I would like to vent it on the stair edge. With an infinite baffle, I would rely on the driver for most of the output. That output may be through a long slot underneath the couch in front of the stair. The vents however, could extend beyond the couch edge, and support a lot of the low frequencies.
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Old 8th February 2008, 04:38 AM   #10
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A CSS SDX7 will fit in your step. And it works really well sealed with a bit of boost. Use enuff of them (4 or 8) and you should be able to move sufficient air to do the job.

dave
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