Advice for enclosure volume, driver size and porting? DIY coffee table subwoofer - diyAudio
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Old 20th May 2012, 07:23 AM   #1
ciper is offline ciper  United States
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Default Advice for enclosure volume, driver size and porting? DIY coffee table subwoofer

Thanks for reading my thread. I will be designing and building my own coffee table subwoofer. My performance requirements seem to be much lower than everyone else. I have been reading through others build threads but so far have not found an easy way to determine an efficient driver for my power levels and room size. I would then use that information to figure out my enclosure volume and port requirements but don't pretend to admit I know the correct methods to calculate these.

Does a thread or website exist where I can read about "tuning" my build? I don't necessarily need hand holding, just a little push in the right direction.

If it helps here are my room details
- Powered by two bridged Marantz MA-500 monoblock,. 8ohm 250w or 4ohm 360w (rms) http://www.hifi-pictures.net/amplifi...tz%20MA700.pdf
- The viewing area takes 1/2 the room with the dining area in the other half. The total is 13 feet by 25 feet. It has a 10 degree sloped ceiling.
- Maximum external dimensions of the table can be roughly 70l 32w 16h
- It would be nice to have it mounted on castors so it can be moved for exercise videos and that would take away from the maximum height (for my girlfriend of course!)
- I would like to have the woofer fire downwards but if a discrete grill can be found I would consider mounting it to one side
- I live in a well insulated house so there are no neighbor concerns
- My previous subwoofer was damaged in a move so I am currently using a Polk PSW350 PSW350 Specs Page : Magnetically shielded powered subwoofer. : Polk Audio
- Speakers driven by Pioneer vsx1020 which gives 110w rms and I rarely run it over -22db volume

While I'm at it, if you have any tricks on sealing the enclosure or insulation I'd be glad to hear them. I was thinking to use Silicone on all wood to wood surfaces in addition to screws
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Old 20th May 2012, 08:20 AM   #2
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Download winISD, look around for some drivers that seem like they'll do what you want, plug the numbers in (using the help file), see what you come up with.

Apart from that,
How loud will this need to go?
How low will this need to go?
Are there any budget constraints?
The dimensions for the table (for clarity) - are they in inches?
What will the subwoofer be used for? - movies, music?

For assembly, here's what I do...
Glue and clamp some of the boards together (this is stronger than using screws).
Once the glue has dried, run a bead of silicone along each joint. Wet your finger, then run it along the bead of silicone. This will ensure it's pushed right against the joint. Also removes excess - keep an old towel handy.
Repeat the above, but plan ahead: the last panel you add will be the most difficult to add sealant too, so make sure it's accessible in some way (easiest is the one opposite the speaker cutout).

Chris
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Old 20th May 2012, 09:26 AM   #3
ciper is offline ciper  United States
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Downloading WinISD now.
I don't know how to answer the loudness question.
Considering the current sub I believe anything will be an improvement so the frequency response was not my top concern. Is there a specific number you'd advise me to shoot for?
I would like the driver to cost well under 200$
The dimensions are in inches. The length could be reduce by say 4 inches, width by 6 and height by 2.
The subwoofer will be used primarily for television and movies.

My goal would be to build something properly that is efficient. I am not trying to impress anyone with ultra low bass or the ability to damage the house

Last edited by ciper; 20th May 2012 at 09:49 AM.
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Old 20th May 2012, 01:49 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

You have more than enough box volume to use an efficient 18"
driver in a vented box, or a less efficient driver for very deep bass.

Dayton Audio DCS450-4 18" Classic Subwoofer 4 Ohm 295-475

Should work well. 12 cuft tuned to 18Hz with 3 3"dia x 12" ports. But if
you want more efficiency and less bass then this might be a good driver :

MCM Audio Select 18'' Die Cast Professional Woofer - 700W RMS | 55-2984 (552984) | MCM Audio Select

Because its a more efficient driver Vas is a lot more than the above. However
it still works in the same box, 12 cuft but tuned to 22Hz with 3 3"dia x 7.5" ports.

Note that I don't like classic vented alignments, I like low tunings in box sizes
somewhat larger than sealed but not as big as vented that allow room gain
to well well, even better than sealed boxes.

Attached is the MCM driver :

rgds, sreten.
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File Type: png guff.png (35.2 KB, 121 views)
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Last edited by sreten; 20th May 2012 at 02:04 PM.
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Old 20th May 2012, 02:10 PM   #5
sreten is offline sreten  United Kingdom
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Hi, and heres the Dayton, rgds, sreten.
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File Type: png guff.png (35.3 KB, 121 views)
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Old 20th May 2012, 10:15 PM   #6
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Using WinISD: A Step by step tutorial
Collo's DIY Subwoofer Enclosures
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Old 21st May 2012, 12:45 AM   #7
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Given that you likely don't want drinks walking off the table i would suggest using 2 woofers on a push-push configuration.

dave
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Old 21st May 2012, 01:11 AM   #8
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That's a good suggestion.
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Old 21st May 2012, 01:38 AM   #9
NEO Dan is offline NEO Dan  United States
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Please don't use silicone to assemble or seal your box, #1 it's not good for box construction #2 it gives off corrosive vapors as it cures. If your cuts are smooth and your joints don't have gaps use a wood glue like Titbond, if there are rough cuts or gaps use something like PL Premium or Gorilla Glue(follow the instructions = use water).

Have you tried your current sub(Polk) in the position you want to put the DIY sub in? Your room plays a huge part in the performance of your system and as a general rule of thumb if the Polk won't work there the new DIY sub won't either.
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Last edited by NEO Dan; 21st May 2012 at 01:40 AM.
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