Mini sub for computer system

Discussion in 'DIY Speaker & Subwoofer Building' started by mattkhan, Apr 3, 2016.

  1. mattkhan

    mattkhan
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    I am setting up a small 2.1 system atm for PC and gaming use. Plan is to build a desk (something along the lines of Pipe L Desk), plonk as pair of quarks (The Quarks - M.O.S.D. Computer Speaker - Techtalk Speaker Building, Audio, Video Discussion Forum) on top for the mains and then I need a sub to sit under the desk to supplement the low end. I picked up an old avr on eBay (denon 2310) to power it as that seemed the easiest way to get old consoles (i.e. multiple component or composite inputs required with HDMI output) hooked up as well.

    Initial thoughts are to use this driver "Tang Band W6-1139SIF 6-1/2" Paper Cone Subwoofer Speaker" from www.parts-express.com! in a fairly small box. Not sure yet whether to port it, use a pair of PRs or use a pair and dual oppose them. Next step, modeling.....
     
  2. mojogoes

    mojogoes
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  3. mojogoes

    mojogoes
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  4. mojogoes

    mojogoes
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  5. mattkhan

    mattkhan
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    EU stockist of tang band -> http://www.oaudio.de/en/Loudspeaker-chassis/Tang-Band/Subwoofer/Tang-Band-W6-1139SIF.html

    seems a tricky thing to get right ported as the port required is massive relative to the box, I think it would have to be a slot port that folds around the entire perimeter of the box... googles a bit.... something like this one

    Mini-Me 6.5" TB W6-1139SIF in 0.35 cu. ft. - Home Theater Forum and Systems - HomeTheaterShack.com

    some tapped horns here -> Tapped Horns

    bit big for a computer unit though :)

    dual opposed needs a big fat LT to bring up the bottom end, certainly doable but whether it is sensible is another Q
     
  6. mattkhan

    mattkhan
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    any ideas on plate amps? needs to give about 100W at 4ohm
     
  7. mojogoes

    mojogoes
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    Oh dear i see your going to get carried away with this project too matt:facepalm::)
     
  8. mattkhan

    mattkhan
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    Hypex Electronics webshop looks like a nice option, this would be perfect for a dual opposed *if* it could do 200W not 100W total
     
  9. mattkhan

    mattkhan
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    Back of a fag packet calculation says box would need to be about 200mm deep to accommodate the driver on the front and amp on the back, 12" square face signs allow for a slot port around 40-45" long which, I think, is just about enough. I could possibly make it shallower with the amp on the side, effectively attaching the amp in a separate housing. Not sure if rocking will be an issue though (not that this system needs to be pound but still).
     
  10. mattkhan

    mattkhan
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  11. mattkhan

    mattkhan
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    0.75ft3, a 30" long slot port and 100W produces the following at 1m

    upload_2016-4-3_15-14-3.png

    I think this would require a box ~15" x 15" x 8.5" and hence the port would run along 2 whole sides of the box. Next step, a sketchup model to check volumes and adjust size/tune as we go. I think I also need to make an allowance for the way winisd models a slot port but need to read up on that one.
     
  12. mattkhan

    mattkhan
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    upload_2016-4-3_17-45-47.png

    45cm high, 40cm deep and 22cm wide
    port is 3cm * 18.4cm cross section and a max of ~1m long

    this should give a tune of 28-29Hz and something that is pretty much an EBS3 alignment (I think)
     
  13. markymiles

    markymiles
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    Blimey Matt, how many projects have you got on the go at once??
     
  14. mattkhan

    mattkhan
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    Lots on paper, not many exist in the real world yet though!!
     
  15. mattkhan

    mattkhan
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    a smaller alternative would be the dual opposed with a shedload of EQ applied. The hypex plate amp has two modules in it which can be bridged to produce a peak of 140W into 8 ohm, the DSP can do LTs and high/low pass filters. A pair of the ferrite magnet drivers and 15L (with added high and low pass filters to simulate a crossover) would give the blue line, orange is the ported sim

    upload_2016-4-3_20-9-34.png

    the room it is going into is not massive so one might expect room gain to kick in and counteract that rolloff.

    I don't think I'm going to be rocking 100dB in this room so I doubt the reduced max output matters & a simpler build is nice (faster).
     
  16. mojogoes

    mojogoes
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    If its for a bedroom / study then i guess it should work out very well
     
  17. mattkhan

    mattkhan
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    yeah it's basically a study

    interestingly, playing with enclosure volume and port tune lets me create something with pretty much the same response shape. It's blatantly much easier to use EQ to tune this rather than building a new box each time you want to EQ it differently though :) having said that, using EQ uses up upper bass output whereas a port doesn't...

    in summary, I need to find a cheaper plate amp... that hypex one has some DSP chops but there isn't enough to work with to boost the hell out of it
     
    Last edited: Apr 3, 2016
  18. mojogoes

    mojogoes
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    Wouldn't the bk xls200 fit the bill perfectly
     
  19. mattkhan

    mattkhan
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    Wrong size, I don't want a small cube
     
  20. chrisgeary

    chrisgeary
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    You probably want to do a build, but I thought I'd mention the Yamaha YST MSW10. Can be had on ebay for less than £20 and is good enough to provide some bottom end to small sats. I've got one you can borrow if you want to try it out.
     
  21. mattkhan

    mattkhan
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    introducing the subwoofer desk

    PC (I built one using a Obsidian Series® 250D Mini ITX PC Case case a little while ago) will go next to the sub

    Monitor will be attached using Ergotron 45-241-026 LX Desk Mount LCD Monitor Arm

    AVR and consoles on the lower shelf and will attach a PSU to the back of one of the shelves or perhaps hang it down the side

    Top and shelves will be Solid Walnut Worktops, walnut block wood kitchen worktops - Worktop Express

    Legs etc will be galvanized steet conduit tubes (painted black)

    Desk is sized so the surface is at ~720mm and there is ~330mm clearance from the edge of the desk to the shelf (hence sufficient to sit at without your knees banging on it)

    upload_2016-4-7_22-11-41.png

    I need to go back to my sub model to check the tuning as the above has squeezed the size back down. I reckon it will still end up a 30Hz tune but will be more like a 15L enclosure which would yield

    upload_2016-4-7_22-19-11.png
     
  22. mojogoes

    mojogoes
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    I was thinking more in performance terms.
     
  23. mattkhan

    mattkhan
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    it looks like it has less output tbh though having said that, I don't think peak output is a major concern here. Nevertheless, to be an actual subwoofer rather than a woofer, a sealed sub needs a bigger driver as it has to make up for the port output which then means a bigger baffle which, given a fixed volume to play with, means a squatter/more cubic sub
     
  24. mattkhan

    mattkhan
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    finalised table design using real sizes of connectors

    upload_2016-4-10_10-30-10.png


    also had to revise the sub design to make the port smaller

    upload_2016-4-10_10-31-25.png

    I think I need to cover over that again because I don't have enough 18mm mdf to complete it so will use 12mm for the port

    the port wraps all around the sub btw so it's sealed against the bottom, back and top. I will add some cross braces inside using dowels as well.
     
  25. mattkhan

    mattkhan
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    thinking of building some tiny (like 1L tiny) full range speakers using SB65WBAC25-4

    crossing at ~150Hz should give me ~94 dB at 1m which is surely plenty for this use
     
    Last edited: Apr 15, 2016
  26. jonone

    jonone
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    Sb acoustics make good drivers, there what's is used I'm my speakers.
     
  27. mattkhan

    mattkhan
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    the fullrange forum on diya is a mine of information

    new plan is to build a mini karlsonator -> Mini Karlsonator (0.53X) with Dual TC9FD's - diyAudio

    £10 for a driver, a few quid for some foam core boards, an xacto knife and some hot melt glue == budget speakers ftw
     
  28. mattkhan

    mattkhan
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  29. mattkhan

    mattkhan
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    Little baby sub arrived, aww cute!

    IMG_20160422_142103.jpg
     
  30. jonone

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    I love tiptree jam :love:
     

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