new 15 inch sub

Discussion in 'Car Subwoofers' started by pedro quiroga, Jun 7, 2009.

  1. pedro quiroga

    pedro quiroga Well-Known Member

    a friend of mine gave me his last quantum 15 sub d2. i know that this thing will pound as it used to be in his truck and it and the 3 others were loud with only 250 watts each and i'll be throwing 800ish at it.

    so i need a box designed. specs say it needs 3.5cf. my current box is over 4cf now and tuned low.30hz. i want this to be tuned as low as it.

    my max width is 38.5. i want the option to turn the box if need be. so the port must be on the same face as the sub.

    so im thinking 38.5 x17 x17. so no matter which way i face the sub the space left over is the same( for groceries and stuff).

    im having a friend build this one for me for free too. the same guy that gave me the sub. awesome right!

    oh and the 8's will be saved for my SQ system one day.
     
  2. fstrfvo

    fstrfvo Full Member

    so you are going to swap 1 15 for 4 8's. the 8's have it in cone space but the 15 probably has it won on excusion. Let us know how it works out.
     
  3. pedro quiroga

    pedro quiroga Well-Known Member

    yeah i know the 8's have it on cone area, but one of them is on its way out with another right behind it.

    im hoping not to loose any db's swapping over.
     
  4. cccullen

    cccullen Full Member

    sweet!!! pics pics pics!!!
     
  5. geolemon

    geolemon Full Member

    Not only would the 15" likely have the 8" on excursion, that single large cone with that single larger, heavier voice coil will have a tremendously lower resonant frequency compared to four individual tiny, light cones...

    It'll be a totally different animal - this sub should not only be as loud as the eights in the frequency range they were [Fs and excursion] limited to, but it'll DROP way lower than those eights, and shake you up. The eights just kicked nicely, I'm sure. ;)

    But it's an interesting point about the eights and 15... in an SPL contest context, where you only have to tune it for a burp at a higher frequency, you might be able to make a box that would eek out the 15" in SPL. It would be sweet if classes were done by cone area... way more fun. :cool:

    But in a street car, tuned anywhere below 45hz, this 15" should be a winner in more ways than (but including, if only perception) SPL. Let us know how it turns out...
     
  6. pedro quiroga

    pedro quiroga Well-Known Member

    the 8's can play as low as 25hz with authority at a decent volume, but because 2 of them are right under the port (mistake in design) they start to bottom out first.

    its those two subs that are starting to give me issue's . one lost a coil and the other is starting to make a scratching noise. i think they will sound better in my house as HT subs wired to 4 ohms with lower power.

    about the weight of the 8's 1 weighs close to as much as this 15 does. its like 10lbs for 1 8".
    http://www.edesignaudio.com/product_info.php?t=2&products_id=785
    i have the 9kv.2's but these specs are the same.

    the cozmic sub weighs maybe 12~13 its really light for a 1000 watt rms 15 sub.but it does have a much stiffer suspension.
    http://www.quantumaudio.net/cozmiksubs_qcw15d2.htm

    but i know it will play well in my hatch. ive seen it in action,and it was free. i will only have to buy the materials. 35ish will cover it.
    i just hope it gives me the same impact with my music these 8's do.
     
    Last edited: Jun 8, 2009
  7. pedro quiroga

    pedro quiroga Well-Known Member

    Specifications

    Qts: .30
    Qes: .38
    Qms: 3.5
    Fs: 23.00Hz
    Re: 7.4
    Vas: 45L
    Mms: g
    Bl: 15.34T*m
    SPL: 83.43dB
    Sd: 231cm²
    Xmax: 14.1mm
    Voice Coil: 38mm

    Magnet Width: 4.800"
    Cutout Diameter: 7.250"
    Mounting Depth: 4.375"
    Weight: 10lb
    Total Height: 4.900"
    Displacement: .05 ft³
    Outside Diameter: 8.375"

    thats the 8's spec.
     
  8. pedro quiroga

    pedro quiroga Well-Known Member

    Ω 2ohms x2

    fs 25.5hz

    qts .76

    qms 6

    qes .85

    vas 136

    xmax 15 mm

    re 3.8

    power 750/1500

    sens 89

    15's specs
     
  9. pedro quiroga

    pedro quiroga Well-Known Member

    which is the better sub if you go by the numbers?

    just curious is all. i dont know what all the numbers mean.
     
  10. aznboi3644

    aznboi3644 Full Member

    damn the 15 has a high QTS....more suited for IB and large sealed enclosures.

    Ported it will likely sound very peaky and muddy.

    Ok well well after crunching some numbers the 15 can sound decent in a 4th order bandpass if you wanna try one Pedro.
     
    Last edited: Jun 8, 2009
  11. geolemon

    geolemon Full Member

    Actually there's a lot that's noteworthy about that comparison...

    Just a generalization, but by the specs, those look like some beefy, high capability eights.
    And, by the specs, the 15" looks like a cheapo, save for having high powerhandling.

    The eights have strong motors - very low Qes and Qts. Of course, they don't have much mass to push, even though it looks like they have pretty heavy cones as eights go. And, the suspension on them is pretty soft, very high mass - gives it a very low resonant frequency, that's very low for an eight. And, it must have a pretty wide diameter spider and long voice coil (I'm assuming it's overhung), because a 14mm Xmax is very long for an eight - if that's a real (meaning one-way) Xmax that's listed there. With a coil that long, I'd also guess it handles a decent amount of power - more cooling area, and I'd guess with that kind of moving mass, a good part of that is a heavy duty voice coil... the efficiency is pretty low for an eight, so that all adds up. Bottom line - those are some really nice eights, at least by design (apparently not by execution).

    The 15" by comparison... I'm not the slightest bit impressed by a 15mm Xmax on a 15" sub... even purpose-built nearly even-hung SPL subs have that for excursion. And, that Fs is pretty middle of the road... seems like there's not much moving mass there, usually that means the components used are light, maybe cheap... very surprised to see 750w powerhandling even. It's not a strong motor, that is a tremendously high Qts and ludicrously high Qes... which, if nothing else, means that sub is going to sound bad in a vented box. That sub says "seal me" all over it.

    I agree with asnboi3644... a 4th order bandpass might be one way to get around that last issue there... in a 4th order bandpass box the rear chamber IS sealed, and you can manipulate the SPL skyward by playing with the tuning on the front chamber (the vented one). I didn't model this up in anything, but I'm guessing that regardless, this sub is going to be wanting a pretty huge box... and in this case, these weird specs might mean you wouldn't want to send 750w into it at any rate, in an enclosure that large.

    Really interesting comparison...
    Now I'm really curious, because there's no advantage at all in excursion, Fs is virtually identical between them, and if you end up going from four eights vented to one fifteen sealed.... the four eights will definitely have the single fifteen in SPL, by these specs. ;-)
     
  12. pedro quiroga

    pedro quiroga Well-Known Member

    hmmm. my friend wanted to try a 4th order bandpass with it. now i dont think i want to use it.

    i was thinking sealed to keep it simple, but now.....

    it is a cheap ass sub too. i looked it up and new they sell for 89~99. the power handling is 1000/2000 . i looked at he wrong subs info. it sure dont feel like it can handle that at all.

    i think i'll keep the 8's a while longer.
     
  13. pedro quiroga

    pedro quiroga Well-Known Member

    been giving it some thought since my last post.... how big of a sealed box?

    i can do 38.5 X 17 X17 thats a lil over 5cf. too much?
    i read somewhere that the bigger the sealed box the deeper the bass can play.

    would a box that big and over 800 watts be too much?
     
  14. pedro quiroga

    pedro quiroga Well-Known Member

  15. aznboi3644

    aznboi3644 Full Member

    that would work...but the 4th order would be 5 cu ft net (both chambers) using two 6" round ports.
     
  16. geolemon

    geolemon Full Member

    I assume that's a different sub, not those cheapos?

    Also, as an option, I know the owner of Pro Tech, and he's basically ending life on the company... he's got these very nice beefy eights (I used two in a dual-chamber vented enclosure, and it was easily as loud as a twelve) that I can get my hands on to you for $30 each I'm sure. They were sold for $99.

    Site is down, I'll have to get you the new page with the specs... but they rock in vented boxes, and four of them would replace yours. I think they are single 4 ohm IIRC.
     
  17. pedro quiroga

    pedro quiroga Well-Known Member

    im keeping my 8's for now. so far the one has yet to die.lol.
    i might do something with the 15 one day. maybe a simple sealed box, but not in my truck as i do need the room for luggage and my cooler. so a big box is a no go.

    30 each is an awesome price,but im broke as hell. i remember pro tech from back in the day.
     
    Last edited: Jun 15, 2009
  18. aznboi3644

    aznboi3644 Full Member

    I'm interested in those 8's
     
  19. pedro quiroga

    pedro quiroga Well-Known Member

    bump!

    im getting the box made on friday. gonna run it at a show on the 19th. same place CC came too.

    any other box ideas to get me loud and low off my nine.5??