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Bandpass Sub for Patio - mounted in crawlspace
Bandpass Sub for Patio - mounted in crawlspace
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Old 13th August 2019, 03:23 PM   #1
iH8usrnames is offline iH8usrnames  United States
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Default Bandpass Sub for Patio - mounted in crawlspace

This year my wife finally bought into the idea of watching projected movies out on the patio. she likes it so much she did not balk at the idea of creating an actual surround sound system out there - obviously would be used for music too.

I have a tight budget and this will not come to fruition until spring 2020 - thus home work now.

I intend to get simple sealed all weather speakers with 6.5" drivers; very likely to be OSD Acoustics found on Amazon @ $150 a pair. Given the driver size it is obvious I will need a sub.

Location information:
- Patio is located at the back of the house where I have an addition.
- The addition has a large crawlspace with concrete floor and considered a "conditioned space" (it gets some heat and AC in the space).
- The crawlspace is 12'x24' with 40" high ceiling (quite roomy).
- I do have neighbors roughly 15' either side of my house. For this reason I would like to limit the sub to 30hz and above - actually 40hz+ would be just fine, I am sure.

Parameters
- I would like a sub located in the crawlspace to deliver sound to the patio through the crawlspace wall.
- I would prefer not to cut 18" holes in the walls.
- I imagine a 4th order bandpass cabinet may be a good fit; the wall penetrations would be limited to the diameter of the ports.
- As noted above I have neighbors, no need to reach 130db at 35hz. Though, I would like to some headroom to protect the drivers from extreme dynamics.
- I imagine crossing over to the sub somewhere between 60-80hz.
- I am not trying to create a high fidelity THX experience, just want something decent with a bit of bottom end.

I am open to:
- single or multiple cabinets.
- single or multiple drivers per cabinet.
- 12", 15" or 18" drivers.
- I mentioned 4th order band pass but open to other ideas so long as it does not result in a large hole in the wall or placing cabinets on the patio.
- If possible I would like to limit the cost of drivers to $400 total, $500 may be something I could swing.


I initially thought of some sort of manifold IB cabinet but figured that would require something like a 10"x17" hole in the wall.

I am totally open to suggestions and would be wildly appreciative of somebody leading me by the nose through the process.
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Old 13th August 2019, 08:23 PM   #2
weltersys is offline weltersys  United States
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Quote:
Originally Posted by iH8usrnames View Post
- I do have neighbors roughly 15' either side of my house. For this reason I would like to limit the sub to 30hz and above - actually 40hz+ would be just fine, I am sure.

- I would prefer not to cut 18" holes in the walls.
- I imagine a 4th order bandpass cabinet may be a good fit; the wall penetrations would be limited to the diameter of the ports.

I initially thought of some sort of manifold IB cabinet but figured that would require something like a 10"x17" hole in the wall.

I am totally open to suggestions and would be wildly appreciative of somebody leading me by the nose through the process.
iH8usrnames,

A manifold IB cabinet can have as small an exit as a bandpass cabinet, as long as the drivers are mounted from the rear.

With only 15' to the neighbors, the distance from you to the sub exit will determine the ratio of level you hear/feel compared to them- if you are 7.5' from the sub, at the property line the level will only be -6 dB, at 40 Hz that sounds almost half as loud. If you were locate that sub under your seat, it's level could be reduced by 10dB or more while still sounding/feeling louder to you, while reducing level to the neighbors to a fraction of the annoyance.

For the levels you are looking for, a 12" with decent excursion (12mm Xmax or so) in a box that would fit under a patio chair would be plenty, and avoid cutting holes in the house and all the sealing problems. LP SmartSide paneling holds up to outside use quite well.

Another option would be tactile transducers built into the chairs, you can shake your booty without the neighbors hearing a thing.

Art
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Old 13th August 2019, 09:29 PM   #3
iH8usrnames is offline iH8usrnames  United States
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Realistically, if the sub were in the crawlspace we would be 3-5' and the neighbors would be roughly 20-25' from the sub.

I am not overly worried about the neighbors, we are usually done out there by 11pm and can turn down the bass if needed.

My point in bringing them up is, I do not live in the country and I am courteous; in other words, I do not need concert sound levels in my back yard.

Our furniture is not compatible with tactile transducers - I am a woodworker and the patio sofa is custom made. Also, I am not interested in having sub boxes on the patio.

Using a Dayton Audio PA460-8 in a 4th order bandpass resulted in something quite workable, I believe.

Rear Volume 9cuft
Front Volume 5cuft
Tuning 50hz
High Pass filter set to 30hz
Nets a flat response from 40-80hz with theoretical max SPL of 118db.

Just adjust tuning frequency to 40hz and it still has a decent flat response from 30hz to 80hz and SPL of 114db

But WinISD v the real world?

Last edited by iH8usrnames; 13th August 2019 at 09:33 PM.
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Old 13th August 2019, 10:41 PM   #4
Brian Steele is online now Brian Steele  Grenada
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I'd suggest against cutting holes in the external walls. Sound may get out, but critters will get in

Bandpass subwoofers can be tricky to get right. All of the output is through the vents, and you will likely need to adjust their lengths a bit to get the tuning just right. WinISD also does not take semi-inductance into consideration, so the passband might not end up being what WinISD predicts.
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Old 13th August 2019, 11:51 PM   #5
iH8usrnames is offline iH8usrnames  United States
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Quote:
Originally Posted by Brian Steele View Post
All of the output is through the vents, and you will likely need to adjust their lengths a bit to get the tuning just right. WinISD also does not take semi-inductance into consideration, so the passband might not end up being what WinISD predicts.
These are the technical bits I do not know - the WinISD stuff and why I hope to be lead by the nose through the process.

As for port length, the ports will be on the outside of the box, thus by much easier to modify. The current math shows a 12" port. If it need be longer, just move the box a bit further from the interior wall and use a longer tube.

I understand this would affect the measurements of the front chamber and may need to make additional modification there.

As for critters I thought I could use PVC caps when not in use. it occurred to me I could also put an elbow on the outside facing down - not east for critters to get in and would look like a high efficiency furnace exhaust.

The crawlspace had vents at one time, thus I have no real concern installing a could 6-8" holes.
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Old 14th August 2019, 02:35 PM   #6
iH8usrnames is offline iH8usrnames  United States
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This is the latest idea.

Normal ported cabinet with the driver feeding a chamber that penetrates the exterior wall.

The port would be mounted exterior of the cabinet and penetrate the wall elsewhere.

Bandpass Sub for Patio - mounted in crawlspace-cad-drawing-jpeg
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File Type: jpeg Cad Drawing.jpeg (145.1 KB, 126 views)
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Old 15th August 2019, 01:56 AM   #7
GM is offline GM  United States
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IME with backyard systems in suburbia you're better off with bass shakers and modest mains roll-off below 80 Hz, especially if you're not playing their kind of music, movie and/or don't invite them over each time.

GM
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Old 15th August 2019, 03:35 AM   #8
iH8usrnames is offline iH8usrnames  United States
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The lounge furniture on the patio is custom made by me, it is not conducive to slapping bass shakers to it.

Bandpass Sub for Patio - mounted in crawlspace-sofa-jpg

None of my neighbors have had issues and I have a good relationship with all of them.

I'll take my chances.
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File Type: jpg Sofa.jpg (109.7 KB, 56 views)
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Old 15th August 2019, 10:02 AM   #9
Turbowatch2 is offline Turbowatch2  Germany
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This one should be what you want:
THSpud | Danley Sounds Labs | Danley Sound Labs, Inc.

Plans can be found in the net. Too loud, too low does not exist with subwoofers, you control the volume and the roll off. Not loud enough, not low enough is the usual problem. You have the space, you like woodworking, so this one is for you. The speakers are not very expensive, it is the work that makes this one XXL$.
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Old 15th August 2019, 01:27 PM   #10
Turbowatch2 is offline Turbowatch2  Germany
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PS 2 of these are used in the THSpud:
W8-740P - 8" Paper Subwoofer - TB SPEAKER CO., LTD.

Wood cost depend on you. No need to take expensive panels MDF is fine.
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