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DIY Subwoofer, What do think of this? help me can if you can

Discussion in 'DIY Speaker & Subwoofer Building' started by Kornmong, Jun 23, 2005.

  1. Kornmong

    Kornmong
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    My first project

    Im making a DIY subwoofer which was meant to be cheap but so far it hasnt been, so far it has costed $500 and its not even built yet.....well

    I was recently looking for a woofer, so I took a visit to Autobarn and saw a 12" car subwoofer in the 30% off section, its cost $200 and the specs seemed to be good so I bought it.

    The specs on the box were:

    12 inchs
    QTS: 0.4171
    Xmax: 15 mm
    FS: 30 hz
    Rms watts 350
    Max watts 800
    dual VC

    But I wanted to check these on the net for reviews and info but could not find anything even though the box has full name and model number and specs

    The name was US Audio Digital ready super woofer, the name on the back of the woofer was goliath

    I can not find any bit of info on the net not even a picture, But what I have noticed is it looks like adire 12" tumlut woofer

    Ive all ready made the box It has 85 litres of air and is (WxDxH) 40cmx40cmx60cm its going to be a bass reflex design with two ports tuned to 28hz, The box is braced to the max with a vertical and horizontil full sheet cut with holes through it going through the middle of the box from left to right back to front and top to bootom

    The amp module im using is a jaycar 350 watt @ 4 ohms +remote+volume module with bass boost 6 db @ 35 HZ

    Im hoping it to do about 30 hz at 110 DB easy :rotfl: or is that to much to ask for?

    If you can help make this any better, post it

    Thanks
     
  2. Pollywoggle

    Pollywoggle
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    Building your own sub must be rewarding I guess but seems to be expensive for what you can get ready made, especially in the States.
     
  3. micb3rd

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    Building DIY can be great if done right.

    What you must realise some car audio drivers are just not suited to use in the home, 110db from 30hz is a bit optomistic.

    Have you got the full Theile and Small paramaters/spec for the driver?

    You box could be completly wrong for it, unless you do some moddling in Winisd/Bass Box pro it will be very hit and miss.

    Give me a picture of the driver and as much info as you can and I will help you with the design.
     
  4. Kornmong

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    Thats the thing, the stats I gave you are all the ones on the box plus none of the names off the box work on google and I cant find anything at all!! on it but I will post a pic in about 2 days.
     
  5. Nimby

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    Let's try and put the technical problems into everyday language in case it helps other would-be DIY home subwoofer fans from making expensive mistakes.:

    A real subwoofer driver needs a floppy cone suspension and lots of cone movement. Such a driver has a low natural resonant frequency = Fs.

    A driver will not play low frequencies unless it can move lots of air. To move that air it needs a large cone and lots of cone movement = XMax

    Car audio drivers are designed to impress technically ignorant young car audio fans. A bit of chrome and bright red or blue on the magnet with fancy graphics on the cone and a killer name and they think the driver will play 15Hz @ 130dB. In their dreams! It's just not going to happen unless you have the correct TS parameters which accurately describe how the driver performs. Its Fs and XMax again. You jut can't avoid them in this game.

    The lack of TS parameters is usually a sure sign of a poor driver. Without TS paramaters you can't even start to design a suitable box for the driver. You sure as hell can't just drop any bass driver into any available reflex box off the shelf in the car audio shop and expect a real subwoofer for home use.

    Let's repeat that again: Reproducing (playing) very low frequncies requires a very low natural "free air" cone resonance = Fs.

    http://editweb.iglou.com/eminence/eminence/pages/params02/params.htm


    If you put any driver in a box it can't and won't play much at all below the cone resonant frequency. But just putting it into a box will usually raise the cone resonant frequency a lot! AArrgghh! :rolleyes:

    So if you start with a typical car-audio "super-mega-killer-bass" driver with a 50-60Hz Fs and then bung it in a box you'll be really lucky to get much real bass at all. The Fs will be raised to 80-120 Hz or higher by the box itself. The box air is squashing agains the cone and making the suspension even stiffer than before.

    Remember we said that a cone can't play anything much below it's cone freqnency? Well now you are fighting to get bass out of a cone working at the much higher box-modified resonant frequency.

    Just picking one of the many reflex boxes off the shelf in the car-audio shop and putting just any driver ito it will not make a suboofer you can use at home.

    The passenger cabin of a car modifies the bass output enormously. It's not really cheating provided you only use your bass-box in a car. But at home you can't do that. You are at the mercy of your room. Which won't have anything like the bass boost effect you desperately need to make real bass.

    The bottom line is that a car audio subwoofer won't work in a room. And even if you use it in a car it can't play low and loud. Which is why they are called one-note-bass-car-subwoofers by home audio bass fans.

    Nimby
     
  6. IronGiant

    IronGiant
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    Very good points Nimby,
    But I have to point out the car audio driver I replaced my BSB 12" driver with as a "HOME" user is much, much better. But then again I chose it carefully, or maybe I was just lucky :D

    Dave

    EDIT:

    I'll post a curve as soon as I can find my spl meter... :clap:
     
  7. Nimby

    Nimby
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    What can one say? There are always exceptions to the rule. It will be interesting to see your response curve. :suicide:

    Regards
    Nimby
     
  8. Kornmong

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    I know what subbass is Nimby, my woofer has got decent Xmax and alright fs, well any here are those pics I said I would send (they do look like tumlut dont they)

    How the **** do you insert pictures into this forum, Ive got the pictures right now and they are all about 750 killer bytes so I cant attach them
     
  9. Kornmong

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    Here are the pics!

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    I think the woofer looks SICK!

    If you can find any info on this driver please post
     
  10. Nimby

    Nimby
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  11. Kornmong

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    I know my driver is no where as good as the tumlut but I said looks and you must agree

    my driver was AU$200 on special not near $1000

    when I get my responce curve ill post

    Winsid predicts 20hz-80hz +/- 3 DB but I doubt that becuse my amp has +6db at 35hz which
     
  12. avanzato

    avanzato
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    My first thought when you mentioned 'Goliath', was this one.
    Shadow Works
     
  13. Kornmong

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    If mine were as good as that one, Id be sh*tting myself with happiness.....Xmax of 40mm wow :eek:

    could you find mine so I could get all the theile stats?
     
  14. Kornmong

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    all that looks the same is the surround and woofer material
     
  15. avanzato

    avanzato
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    Have you tried contacting the company direct?
    http://www.us-audio.com
    You can measure the parameters yourself, it's not something I've ever done but there's info on the 'web' if you look for it.
     
  16. micb3rd

    micb3rd
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    I personaly know Shaddoworks well.

    I did have a SW:Goliath for a fair time for a online review for Car Audio, it's Neodynium N42 magnets are very powerfull, they make the driver very heavy waying in at high 20KG's (4 stone+) I can imagine with some playing around with enclosures it would be good in the home.
     
  17. Kornmong

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    thanks for the site but the contact us button dosent work eg I filled the spaces and clicked submit but nothing happens.
     
  18. Kornmong

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    Mines not the same one, mine only weighs 8 kg!

    20kg :eek:
     
  19. Kornmong

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    YEAH......im finished testing it here are the result

    It not the flatest responce but that can be fixed by turning down the cossover and its my first projest, next time there will be a lot more study time eg bigger box bigger ports and 15" tempest woofer

    Becuse winsid prodicted that my biggest exercursion would be at 35hz, I used 35 hz as volume setter because any other frequency would exert less meaning no risk in damage..(this was done outside) I can get a louder 20 hz like 101 db but thats only when its only getting 20hz from the siganl generater

    Never seen 10 hz it moves so slow and smooth

    maximize screen when viewing pick

    http://img336.imageshack.us/img336/5629/subgraph1ja.png
     
  20. IronGiant

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    That's a nice flat curve, though it does start dropping off quite quickly after 40 Hz by the look of it. At what frequency is it 3dB below the flat part?

    Dave
     
  21. SillySausage

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    I too know shadoworks up in sunny Scotland.

    I've got one of their Genesis 12" drivers in the car and it certainly sounds sweet.

    They also do quite a bit with a few home audio companies and I believe some of there subs are integrated well with some wuite high end speaker systems.

    Maybe somebody on here could get a SW driver installed in a propper enclosure and tested against the regular known subs. I suspect the results will be interesting ;)

    Adam.
     
  22. GaryG

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    The Tempest is a nice driver but I would suggest you save your money and go straight for a Tumult unless you are building for the enjoyment, the performance of the Tumult is such that you wont bother building anything else.
     
  23. Kornmong

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    Tumlut rules I know.....66 exercursions :eek: but i cant afford it yet, plus ill have to buy a more powerful amp, at least 500 watts at 4 ohms

    could you give me an idea on spl levels? in room
     
  24. GaryG

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    I have no idea on spl levels, I use a pair of Tumults driven by a Crown K2 amp with a Marchand Bassis LT for equalisation. In my small room (13ft x 8ft) they are more than adequate although I have a spare Tumult just in case it's needed.

    I previously had four Tempests although I never bothered to use more than two of them. Set your mind on a Tumult and put all your spare money into getting it, after that you can cross subwoofers off your list of upgrades.
     
  25. micb3rd

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    Kornmong what was your tuning point of your vents?
     
  26. Kornmong

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    Tuning was at 21hz, still whisles like a bitch at 20hz
     
  27. Kornmong

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    alright then i get a Tumlut, itll take a while but ill get it, what size are your tumluts and how much did you pay for them?
     
  28. GaryG

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