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2 'lesser quality' subs = 1 'good' sub?

Discussion in 'Speakers' started by Mike Thomass, Mar 10, 2011.

  1. atc454

    atc454 New Member

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    Thanks.Your article is wonderful!Hold it.i like your article very much and here i intraduce some nice web site aboutElectronics Wholesales for you : chingtown.com
     
  2. Mike Thomass

    Mike Thomass Well-Known Member

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    my defective d8's went out to parts express and have been replaced and are back in place. no hassle at all from parts express. very happy with the results. still working on the subs
     
  3. Mike Thomass

    Mike Thomass Well-Known Member

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    2 questions for you robert: 1. should i follow any type of break in plan for the new d8s? for the subs? 2. i dont have a tip for my soldering iron, so when i replaced the d8s, i used female quick connects on the speaker connections. should i eventually solder the wires, or will there be little to no difference with the quick connects? thanks
     
  4. Robert_J

    Robert_J Well-Known Member

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    1. No. This isn't like an SPL competition where you are dumping 20,000w into a brand new sub. Normal playing will loosen them up and cranking them on day one won't hurt them in the least bit. 2. Quick connects are fine. If you move your speakers around a lot, one might come loose. During normal listening there is no difference.
     
  5. Mike Thomass

    Mike Thomass Well-Known Member

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    thanks brother
     
  6. Mike Thomass

    Mike Thomass Well-Known Member

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    to help any other DIY noobs like me, heres a list of tools/consumables used for the D8 pencil plunge router some type of router circle cutting jig 1/4" spiral upcut bit jigsaw tape measure long straight edge speed square power drill with a bit power sander titebond II glue clamps. lots of clamps. 90 degree clamps bondo flush trim bit round over bit (optional, for looks only) laquer sanding sealer various grits of sandpaper (hand/block sanding) primer spray paint 12awg speaker wire soldering iron small piece of 1/4" plywood or something else to hold crossover parts wire cutter/stripper glue gun and/or plastic zip ties screwdriver(s) some type of acoustic stuffing weatherstripping (or something else to make a seal) i think thats it. i would think these items are needed for pretty much any speaker build, not just the D8 you can make a circle cutting jig fairly easily from either that small sheet of 1/4" plywood you may have for the crossover, or an even better option would be to use some plexiglass/polycarbonate/whatever from home depot or lowes. you could buy one as well. you can do without the jigsaw and use the router instead, but its much easier and faster to work with a jigsaw than a router if possible. for example, cutting the openings in the braces. bolded items are an absolute must have. the rest i definitely needed as well, and you will too, but maybe a slight variation.
     
  7. Mike Thomass

    Mike Thomass Well-Known Member

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    as a holiday treat, heres some pics of my dual 15" sub build progress. wood (pre cut at home depot) and some tools. i replaced that cheap mask with a nice half mask respirator btw. [​IMG] my custom made circle cutting jig [​IMG] cutout for terminal plate [​IMG] creating 1.5" front baffle [​IMG] almost all parts glued together. sorry no pics of the braces prior to assembly [​IMG] all closed up. you can see the overhang that will be trimmed off. a little too much overhang, but i erred on the side of caution when giving the measurements at home depot. [​IMG] two boxes, trimmed, bondo'd and rounded over. didnt take any pics of trimmed edges prior to rounding. i went overboard probably with the bondo in spots, but i wanted get rid of any tiny lines that might show up in the seems. also, there were some imperfections in the wood, and some splintering during trimming. [​IMG] starting the holes [​IMG] made two full depth circles with the router. one that extended to the outer edge and one that extended from the inner edge. then used the jigsaw to cut out the opening. once the main hole was open, I broke off the circular piece that remained (between the two router cuts). i learned from the d8 build that that piece would come off pretty easy, so i did the inner router cut and outer router cut, planning to pop that middle section off. worked great and saved a nice bit of routing time. it doesn’t break off exactly flush with the routered area, so i use a chisel and pop off the rough parts, then sanded that surface. looks as good if not better than if i made 3 router cuts instead of 2. [​IMG] two big boxes, ready for sealing and painting. these things are pretty big. even though they are nice and smooth, im probably going to sand them a little more before sealing. i see some extra bondo. im obsessive. [​IMG]
     
  8. Mike Thomass

    Mike Thomass Well-Known Member

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    rob, heading out to buy pillows now. is it possible to put too many in the box? too little? the build page guy used fiberglass insulation as we know, and it didnt look like too much. im wondering about the whole q value thing. the guy said the design had a target q of .65 which if i understand things is pretty good, but things can get bad if you get too low. thanks
     
  9. Robert_J

    Robert_J Well-Known Member

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    1 pound of stuffing per cubic foot is the standard ratio. I like a final Qtc of .5. Yes, the Fs is a little high but the roll-off is much shallower and can dig deeper than a sub with a Qtc of .707.
     
  10. Mike Thomass

    Mike Thomass Well-Known Member

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    im still not sure how many of these friggin pillows i should stick in the box :huh::D
     
  11. Robert_J

    Robert_J Well-Known Member

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    2 in each box
     
  12. Mike Thomass

    Mike Thomass Well-Known Member

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    finally finished my 2 15"ers one in the box [​IMG] empty cabinet [​IMG] all finished, next to one of my D8s [​IMG] just imagine 2 of each, cause thats what there is, but i didnt see a need to post two pics this time :D
     
  13. Mike Thomass

    Mike Thomass Well-Known Member

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    sometimes it feels like king kong is banging on the walls still want to experiment more with placement however
     
  14. Mike Thomass

    Mike Thomass Well-Known Member

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    robert technical question about sub cabinet stuffing: what is the effect of more or less polyfil? all i know is it apparently makes the driver think it is in a bigger cabinet, but i dont know what effect that has
     
  15. Robert_J

    Robert_J Well-Known Member

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    It slows the sound waves on the back side of the driver (in the box) by converting motion into heat. The driver sounds like it is in a box about 10% larger then it really is. That lowers the enclosure's final Qtc a little. Depending on what the Qtc is, it may raise or lower the Fs also.
     
  16. Mike Thomass

    Mike Thomass Well-Known Member

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    thanks again
     
  17. Mike Thomass

    Mike Thomass Well-Known Member

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    robert i put felt pads under my subs, mainly so i can move them around easily on my wood floors. but now i dont need to move them around much if ever. im wondering if the footing matters much at all. my google search didnt help. would the ideal situation be having the sub bolted down immobilized, and the less immobilized the less ideal?
     
  18. Robert_J

    Robert_J Well-Known Member

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    There are 2 schools of thought here. One group likes their subs de-coupled from the floor. There are those riser pads available from a few sources that will fit under the sub. I'm in the other group. I want my sub solidly on the floor. Either make it big enough so that it doesn't move or add speaker spikes so it is on a solid base. I've never seen any scientific data on either method but the 2nd makes sense to me. With a forward firing sub, it generates a lot of back and forth motion. If the sub is on a soft pad then it will rock. If it is on a solid base, it won't move. The forces will be transmitted into the floor and in my case that is a concrete foundation.
     

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