Help me build a sub to fit this hole in my wall - AVS Forum
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post #1 of 23 Old 11-06-2013, 05:36 PM - Thread Starter
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Hey all. The front wall of my room is made of brick. On one side is a fire place. On the other side is a recess. I was thinking of building a sub to fit in this recess. It is 21"d x 27"w x 23"h. I was thinking maybe a 12" sub and I have typically used sealed enclosures and like them a lot, partially because they are easier to build. But I'm open to suggestions.

I have one request. My room is 18 x 14 x 8 and I want it loud enough that I'll want to turn it down.

Any ideas?

Thanks, Craig
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post #2 of 23 Old 11-06-2013, 05:42 PM - Thread Starter
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Oh, one thought I had...


Since all sides, except the front, are made of brick, could I just make a front for it and seal it up instead of building the other 5 sides (that is if the air space were correct)? Would brick not be much more dense than 1.5" of MDF?
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post #3 of 23 Old 11-07-2013, 05:42 AM
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I would think that brick is stiffer than 1.5" MDF.

YID DIY
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post #4 of 23 Old 11-07-2013, 05:47 AM
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That would likely work, if you were able to properly seal it up, and as long as the volume of the hole is the proper size for what ever driver you end up going with. I would go with a Dayton HO18 or SI 18HT over the 12" driver.
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post #5 of 23 Old 11-07-2013, 07:28 AM
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Having lived in an old brick house, sealing it thoroughly will be a task in itself. Plus, how would you attach the baffle firmly enough to be about to mount a large subwoofer? I think it would be easier to build the entire enclosure and just mount it in the recess.
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post #6 of 23 Old 11-07-2013, 03:12 PM - Thread Starter
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Quote:
Originally Posted by Martycool007 View Post

That would likely work, if you were able to properly seal it up, and as long as the volume of the hole is the proper size for what ever driver you end up going with. I would go with a Dayton HO18 or SI 18HT over the 12" driver.

18"!!!! Wow! I had a 15" in my minivan but it wasn't tight like my 10s and 12s were in the past. The enclosure was built to spec. If I use a powerfull enough amp, like a Crown because I have a connection, will it control it enough to give a nice tight response?

Thanks, Craig
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post #7 of 23 Old 11-07-2013, 03:26 PM
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Quote:
Originally Posted by craig aguiar View Post

18"!!!! Wow! I had a 15" in my minivan but it wasn't tight like my 10s and 12s were in the past. The enclosure was built to spec. If I use a powerfull enough amp, like a Crown because I have a connection, will it control it enough to give a nice tight response?

Thanks, Craig

Size of the driver has nothing to do with "fast" or "tight" bass. That is a terrible myth that is spread amoung the "bro-science" folks. A properly designed enclosure with an 18" driver will always be the best choice. That, plus the fact that car audio and home audio are vastly different when it comes to subwoofers. If your old drivers in your vehicle are not fast or right, their is a really good chance the drivers are not in a properly designed cabinet, or the drivers are crap.
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post #8 of 23 Old 11-07-2013, 04:17 PM - Thread Starter
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Quote:
Originally Posted by rsvr79 View Post

Having lived in an old brick house, sealing it thoroughly will be a task in itself. Plus, how would you attach the baffle firmly enough to be about to mount a large subwoofer? I think it would be easier to build the entire enclosure and just mount it in the recess.


My idea was to use masonry screws, Tapcons or similar, to attach a frame about 1" thick on the inside of the "enclosure". The baffle would screw to the frame. Moving the frame farther into the recess would recess the baffle farther back into the enclosure. I would recess the frame and baffle enough to creat the correct volume.

My idea for sealing the frame against the brick was actually to use auto body filler. Slop it on the bricks, then on the 1" thick frame piece and screw it into pre-drilled holes. Once dry I think it would be crazy solid, and sealed as well. I would dress the front up with a nice grill and some wood trim. I could even do a ckim coat of body filler on the entire inside surface of the enclosure if that would be a bennefit.

With the Daton HO18, I used a calculator online and found the following:

Sealed, inside dimensions

the front baffle would be 23 x 27, the depth would be 13.2" so the baffle would be set back about 7" in the cavity. With this size the sepcs are Fb 35.12 and F3 35.54

Vented inside dimensions.

The front baffle is the same size, 23x27. The depth becomes 20.17. I have 21" available to me so this size of enclosure would allow me a 3/4" thick baffle which I think is good. The port is 4" by 9.33". The specs of this enclosure are Fb 19.6 and F3 29.97.

I'm leaning towards the vented enclosure actually.

For an amplifier I was thinking of a Crown MA1202 -

1130 watts at 4 ohm mono with .1% THD
105dB SN
THX certified

http://www.crownaudio.com/media/storagebk/pdf/amps/136704.pdf

What are your thoughts? My thoughts? I'm getting excited.



Thanks again for your input.

Craig
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post #9 of 23 Old 11-08-2013, 07:45 AM - Thread Starter
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So I've learned that the amp I was thinking of is no longer available.

Can anyone recommend an amp from Crown that is a good choice for a sub-woofer?

I really appreciate everyone's thoughts and recommendations.

Thanks, Craig
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post #10 of 23 Old 11-08-2013, 08:00 AM - Thread Starter
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Another thing.

I see people on this forum making measurements of their rooms and producing response curves showing exactly how their sub-woofers are performing in their rooms.

I would be very interested in doing this. I thought about putting current 12" sub in the cavity and measuring how the performance is in that spot, before I commit to building a sub into my house!

Can someone please point me in the direction I need to go to get this software, (and a microphone as well I presume)?

Thanks again.

Craig
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post #11 of 23 Old 11-08-2013, 08:53 AM
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Quote:
Originally Posted by craig aguiar View Post

Another thing.

I see people on this forum making measurements of their rooms and producing response curves showing exactly how their sub-woofers are performing in their rooms.

I would be very interested in doing this. I thought about putting current 12" sub in the cavity and measuring how the performance is in that spot, before I commit to building a sub into my house!

Can someone please point me in the direction I need to go to get this software, (and a microphone as well I presume)?

Thanks again.

Craig

Welcome to a whole new obsession hobby:

http://www.avsforum.com/t/1449924/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs/270#post_22823228


Downloadable FREE demo discs:
http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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post #12 of 23 Old 11-08-2013, 11:31 AM - Thread Starter
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Ha ha. No kidding.

I just remembered I have a kit for equalizing my sub-woofer. Years ago, maybe they still do, Infinity offered a system called R.A.B.O.S. The room adaptive bass optimization system. It was basically an eq with one center frequency and adjustable q so you could eliminate one bad peak or hump in your bass response. The system came with an SPL meter (fairly accurate for bass I would think since that was the whole point), a test CD and a graph to help you identify problem frequencies. I used the kit and here is what the response looks like with my 12" Infinity in the "hole" and the mic at about ear level in my primary seating position. The baffle for the sub was flush with the brick wall.



It rolls off around 30hz and 90hh which are the lower limits of the sub and my cross over point. The two 8 dB dip at 43hz and the 5dB dip at 72hz don't exactly please me. Is this something I can fix with equalization? I'm thinking I should move the mic to my other seating positions and see how it looks there.

Thanks again for the input.

Craig
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post #13 of 23 Old 11-08-2013, 11:37 AM - Thread Starter
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Thanks very much LastButNotLeast!
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post #14 of 23 Old 11-08-2013, 12:21 PM
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I would take that graph with a grain of salt, since the woofer isn't mounted or sealed.

But that is one fugly graph.

;)

And no, you can't fix THAT with eq.

 

This is a very popular source for parts:

http://www.parts-express.com/?utm_source=google&utm_medium=cpc&utm_campaign=G-Brand-Main&utm_group=G-Brand-Main-Exact&utm_term=parts%20express

 

This would probably be perfectly adequate:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-770

 

This would probably blow you away:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-764


Downloadable FREE demo discs:
http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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post #15 of 23 Old 11-08-2013, 01:56 PM - Thread Starter
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Quote:
Originally Posted by LastButNotLeast View Post

I would take that graph with a grain of salt, since the woofer isn't mounted or sealed.
But that is one fugly graph.
wink.gif
And no, you can't fix THAT with eq.

This is a very popular source for parts:
http://www.parts-express.com/?utm_source=google&utm_medium=cpc&utm_campaign=G-Brand-Main&utm_group=G-Brand-Main-Exact&utm_term=parts%20express

This would probably be perfectly adequate:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-770

This would probably blow you away:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-764

What do you mean by the woofer isn't mounted or sealed. The sub-woofer I used is in an enclosure. Do you mean it's not sealed in the "hole"?

I'll check those websites out.

Since that location is really the only place I can put the woofer (if I plan to go this big), what steps can I take to fix those issues? Is it as simple as a little equalization? I'll be using a Marantz Pre-amp which has Audessy MultiEQXT, which includes equalization for the subwoofer. I have also thought about getting something like this

http://www.dspeaker.com/en/products/anti-mode-8033.shtml

or probably better yet...

http://www.behringer.com/EN/Products/DSP1124P.aspx

I'm not in a possition to move the sub, or my seating so hopefully there is something to help me.

Thanks, Craig
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post #16 of 23 Old 11-08-2013, 02:53 PM
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Sorry, but "12" Infinity in the 'hole'" didn't tell me it was sealed.

You can't (or, more properly, shouldn't) boost, so you're looking at 8dB of cuts on the peaks. The dip is too wide for a room null, and I'm no expert on such matters, so I defer to others here, but that would probably sound as bad as it looks.

I used to use the Behringer (which I got as an open box from Guitar Center; I'm pretty sure it's discontinued), and liked it very much, but you're still going to need REW, so start there.

Michael


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post #17 of 23 Old 11-08-2013, 08:25 PM - Thread Starter
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Sorry I thought it was implied. My mistake. I need to be more clear.

I'm going to use the REW, I'm just trying to figure out what mic to get. It's not something I know much about and it's an important decision. My guess is I can't use the USB mic that came with Rockband!

I've also found a good deal on the Feedback Destroyer. It has been replaced by a couple of different models but I got a great deal on it and if was good a few years ago I can't see how it wouldn't be good now. Granted the new ones may be better but I got this one cheap.

Thanks for your interest in my thread. This has been very helpfull.

Craig
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post #18 of 23 Old 11-09-2013, 09:18 AM
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Quote:
Originally Posted by craig aguiar View Post

Sorry I thought it was implied. My mistake. I need to be more clear.

I'm going to use the REW, I'm just trying to figure out what mic to get. It's not something I know much about and it's an important decision. My guess is I can't use the USB mic that came with Rockband!

I've also found a good deal on the Feedback Destroyer. It has been replaced by a couple of different models but I got a great deal on it and if was good a few years ago I can't see how it wouldn't be good now. Granted the new ones may be better but I got this one cheap.

Thanks for your interest in my thread. This has been very helpfull.

Craig

Two USB mics are available that work well with REW. They're mentioned in Jerry's Guide.

Cheap is good. ;)

And a "better" one won't do much more than the DSP. Some automatic systems are easier, but open up their own can of worms.

Have fun.

And, when you start the build - PICTURES!

Michael


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http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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post #19 of 23 Old 11-09-2013, 11:56 AM - Thread Starter
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I was reading through some of the guide and with the Feedback Destroyer, they recommend connecting it directly to my laptop and then using a Radio Shack SPL meter which I have so I'll start there. I'm looking forward to this.

Thanks again.

Craig
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post #20 of 23 Old 11-09-2013, 12:53 PM
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No, the BDP goes between your AVR and your sub as a parametric equalizer.


Downloadable FREE demo discs:
http://www.avsforum.com/t/1475769/de...ently-authored 

Did you really need to quote that entire post in your reply?
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post #21 of 23 Old 11-09-2013, 02:36 PM - Thread Starter
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Yes I understand that but according to the guide, you also connect it to your computer via a USB-Midi interface. The SPL meter connects to the sound card. The software then measures, and communicates adjustments to the feedback destroyer for you. I could be wrong but that's the way I understood it.

Here are the links.

http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/bfdcomms.html#top


http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/gettingstarted.html

Craig
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post #22 of 23 Old 11-09-2013, 06:43 PM
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So you're trying to use the BDP as a midi interface as/instead of a USB sound card? Sorry, but you're above my pay grade at this point.

At least one of us is really confused. You should, perhaps, take this up on the shack's board, and return here when your build proper begins.

Good luck.


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http://www.avsforum.com/t/1475769/de...ently-authored 

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post #23 of 23 Old 11-10-2013, 07:16 AM - Thread Starter
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Thanks! Haha.

Craig
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