Building a sub into theater room floor.

Newbomb

Member
2008-02-05 3:52 am
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
 

Newbomb

Member
2008-02-05 3:52 am
GM said:
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
 
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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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.
 
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
 
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.
 

Newbomb

Member
2008-02-05 3:52 am
Re: platform woofer

homebuilder said:
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.
 

Newbomb

Member
2008-02-05 3:52 am
musgofasa said:

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.

Keep us posted

Robert

I am about a month out on this project, and still have a lot of analysis to do. I am looking for something that will go _LOW_. My fronts are Thiel CS 3.6's. They them self do pretty darn well.

I really think I can slightly angle a 10" and fit it in OK - with enough room for air flow in front. I just cannot see matching up a small sub - no matter how it is configured - with my Thiels. The 10" neo may do OK, but I don't see it as a good match.

Now, maybe someone knows one that will be a good match. I have done some math, and the Scanspeak 23W has me drooling, but the efficiency does not match up too well (maybe that's not an issue?). The Dayton RSS265HF seems like it might be OK - as with the SB Acoustics SB29NRX75-6. I want something _very_ good, DIY, and _LOW_ but not necessarily needing to have earth shaking output. If I can have the volume though, I would take it.

Todd
Todd
 
Newbomb said:
really think I can slightly angle a 10" and fit it in OK - with enough room for air flow in front. I just cannot see matching up a small sub - no matter how it is configured - with my Thiels.

Do keep in mind that with the XBL2 motor the SDX7 will embarass a lot of 10" subs, and likely all the ones you will find that will fit. That they go higher also means they have a better chance of blending with the mains.

dave
 
HI Guys,
I just read up on the SDX7 and I have to say that sounds like a good deal too. I can't speak from experience with any of these drivers though. If the Thiels you have will get down into the 60s or so, then you are probably looking for just very low freq output which means efficiency really won't matter. You should be able to power the sub with enough juice to balance it out. Of course, if you need it to match up to the low end of the mains, a higher cut off like the SDX7 is probably going to work better than the neo.

Has anybody ever messed with these? I have heard a lot of people say they will get low and loud, but not too much in the way of SQ reviews. I think most people are using them in cars.

http://www.edesignaudio.com/product_info.php?t=2&products_id=33

Take care,
Robert
 

Newbomb

Member
2008-02-05 3:52 am
planet10 said:


Do keep in mind that with the XBL2 motor the SDX7 will embarass a lot of 10" subs, and likely all the ones you will find that will fit. That they go higher also means they have a better chance of blending with the mains.

dave


It looks nice, but I don't see how it could match the Dayton RSS265hf-4 or the Scanspeak 23W as far as low end.

Do you have a vented design for the SDX7 with an F3 in the low/mid 20's?

Todd
 
I haven't used the 7KV2, but I have used the 9KV2. Its ******* awesome.

I've used the 16OV2 and 19OV2 as well.

Anywho, IIRC the 7KV2s work well ported or sealed. If you have enough room, you could use them to drive passive radiators. I think 4 7KV2s plus 2 12" passives would work great. You could tune extremely low and have a small box. I think most passives would be shallow enough to fit in the floor.