Dual 12" Outdoor Sub - AVS Forum
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post #1 of 16 Old 06-23-2013, 06:24 AM - Thread Starter
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I'm looking to build a sub that will fill in the low end for two pairs of Emotiva UOM-6.2 outdoor speakers.

The plan so far is to recess the sub in the ceiling of the covered porch. The porch roof is ~8 feet deep, so the subs will be protected from direct weather exposure, although humidity is still a problem. I chose the Bravox 12" because of the poly cone and aluminum basket. I modeled a few different drivers and these perform well given the design conditions. It also helps that they're on sale smile.gif

The distance between ceiling joists is 14-3/8", so the enclosure was built to those dimensions. The distance between joists limits the diameter of the driver.

Proposing to drive them with NU1000's, giving 500w per driver. The drivers are slightly above excursion at 500w.. I doubt I will actually get 500w out of the NU1000, nor is there any desire to be playing these at max levels, so I don't anticipate any issues.

The enclosure ends up about 3.4 cu.ft. no plans the HPF them.

I'm new at this, so if anybody has any suggestions, please share them. As far as mounting the enclosure-- would there be benefit to locating it close to the wall-ceiling intersection? Or does it not matter outside?



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post #2 of 16 Old 06-23-2013, 05:06 PM
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Will these be downfiring? I'm not sure if I'm reading your drawing right. Two separate boxes might be worth considering. I'd guess "room modes" would get smoothed outdoors too, with multiple subs. Have you looked at autosound subs? They should be able to handle the elements. I wouldn't have a clue which auto subs are decent though.

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post #3 of 16 Old 06-23-2013, 05:15 PM - Thread Starter
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Quote:
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Will these be downfiring? I'm not sure if I'm reading your drawing right. Two separate boxes might be worth considering. I'd guess "room modes" would get smoothed outdoors too, with multiple subs. Have you looked at autosound subs? They should be able to handle the elements. I wouldn't have a clue which auto subs are decent though.

Yes, they are downfiring. I went that route because it will be the easiest to install and there won't be any surface for condensation or other nasties to collect.

For simplicity's sake I want to keep it in one enclosure, but I was wondering about making the divider between the two drivers solid, or perforated?

Thanks,
Tim
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post #4 of 16 Old 06-25-2013, 03:33 AM - Thread Starter
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Before I go and build/intall these, any opinions on whether the two chambers should be completely separate?

I'm also thinking that locating them in the corner would be a good idea.. any thoughts to the contrary?

Thanks,
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post #5 of 16 Old 06-28-2013, 08:18 AM
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I always made my dual subs solid between them- but know that I think about I've forgotten why. It's been a long time since I made an MDF sub.

I'm in for a real answer.

I am surprised you have not gotten any yet. (Bump for you biggrin.gif )

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post #6 of 16 Old 06-28-2013, 12:47 PM
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If you're running one sub to one channel on the amp I think its best to seal the chamber. If both subs are to be run on one channel (Bridged) of the amp then have the chamber open.

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post #7 of 16 Old 06-28-2013, 02:06 PM
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but if it is not stereo and just a LFE out feeding it (the same signal both channels) then it should not matter.

But your advice is spot on from what I remember about car audio.

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post #8 of 16 Old 06-28-2013, 02:53 PM - Thread Starter
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Quote:
Originally Posted by Mrkazador View Post

If you're running one sub to one channel on the amp I think its best to seal the chamber. If both subs are to be run on one channel (Bridged) of the amp then have the chamber open.

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Originally Posted by Mfusick View Post

but if it is not stereo and just a LFE out feeding it (the same signal both channels) then it should not matter.

But your advice is spot on from what I remember about car audio.

Thanks guys. Each sub will be on their own amp. I will keep the center solid.

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post #9 of 16 Old 07-01-2013, 12:10 PM
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I am more than a bit surprised how much power you are dedicating to this sub. Do you routinely listen to music that loud outdoors? I see no reason for two amps. 1 x 500W for two woofers for a combined 4 ohms would far exceed the output capability of your other outdoor speakers.

It won't matter if the panel is solid or open between halves. Both woofers will have the same signal.

With subs like this - you should consider a high pass filter for your Emotive outdoor speakers. No reason to subject the small woofers to a full range signal if you have subs to take care of the low end.
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post #10 of 16 Old 07-01-2013, 12:19 PM - Thread Starter
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Quote:
Originally Posted by hoffdano View Post

I am more than a bit surprised how much power you are dedicating to this sub. Do you routinely listen to music that loud outdoors? I see no reason for two amps. 1 x 500W for two woofers for a combined 4 ohms would far exceed the output capability of your other outdoor speakers.

It won't matter if the panel is solid or open between halves. Both woofers will have the same signal.

With subs like this - you should consider a high pass filter for your Emotive outdoor speakers. No reason to subject the small woofers to a full range signal if you have subs to take care of the low end.

I want to use two Nu1000's, one for the left channel, one for the right channel. There are two pairs of speakers, so the left channel will power two left speakers and one sub. The right channel will do the same.

I realize the need for the HPF, which is why I am using the built-in HPF on the NU1000 to send the sub freq to one channel and the rest to the other channel.

Looks like it may end up being two enclosures with two subs each. Not decided on that one yet.

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post #11 of 16 Old 07-01-2013, 03:48 PM
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Do you need to be concerned about mounting that particular driver horizontally? I have read that the unsupported weight of the cone hanging on the suspension can eventually change the performance of some drivers. Unfortunately, I barely know enough to ask the question. I have no idea how to tell whether it could be a problem.

From your drawing, it looks like you would have plenty of room to mount the drivers vertically and have them fire into a chamber that's open to the space below. That might also protect the drivers from kids and their toys.

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post #12 of 16 Old 07-01-2013, 04:44 PM - Thread Starter
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Quote:
Originally Posted by dwightp View Post

Do you need to be concerned about mounting that particular driver horizontally? I have read that the unsupported weight of the cone hanging on the suspension can eventually change the performance of some drivers. Unfortunately, I barely know enough to ask the question. I have no idea how to tell whether it could be a problem.

From your drawing, it looks like you would have plenty of room to mount the drivers vertically and have them fire into a chamber that's open to the space below. That might also protect the drivers from kids and their toys.

I considered this, and I suppose that it will always be better to have the driver mounted perpendicular.

However, I was also concerned about condensation and other nasties living there.. as well as the practicality of installing the box and getting the driver mounted.. also considered was being able to replace a driver if need be.

The drivers are in the ceiling, so no kids toys to worry about. I would have to build a box wider than the joist spacing to get them to work prependicular; the idea is to cut a hole without cutting the joists and slide it up between them.

The downfire design seemed a better idea in those regards. However, if there are other drivers better suited to the downfire design, I am interested!

edit: after thinking on it, yes the box could be longer to fit the two drivers in an opposed setting, not sure what the overall length would be tho.
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post #13 of 16 Old 07-02-2013, 05:32 AM
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Quote:
Originally Posted by dwightp View Post

Do you need to be concerned about mounting that particular driver horizontally?

This may shed some light:

http://www.facstaff.bucknell.edu/esantane/movies/DriverOrientation.pdf
Quote:
I have read that the unsupported weight of the cone hanging on the suspension can eventually change the performance of some drivers.

It makes some change no matter what. What change it makes varies with the driver.

If you mount the driver on a vertical panel, the deflection could lead to a rubbing voice coil, so there is no way to be perfect.
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post #14 of 16 Old 07-10-2013, 05:42 PM - Thread Starter
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Started building the boxes:

outdoor_sub.JPG

Used MDO plywood and polyurethane glue. The 12" Bravox subs just barely squeek by given the width of the enclosure (OAW=14.375", which leaves 12.875" clear inside width for the flange of the drivers).

I made a few mods to the design on the fly. Same dimensions, just different assembly. Dado'd the sides and top/bottom to accept the double baffle.

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post #15 of 16 Old 07-16-2013, 10:17 AM
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Tim,

how is the progress going ?

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post #16 of 16 Old 07-16-2013, 10:24 AM - Thread Starter
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Drivers arrived yesterday, so I can get the h-nuts set. I've been delayed on finishing because it's been freakin hot out. 97 at 4pm yesterday.

Tim
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