Let's Talk AV12 Enclosures!

Discussion in 'Archived Threads 2001-2004' started by Baldemar Garcia, Sep 20, 2002.

  1. Baldemar Garcia

    Baldemar Garcia Stunt Coordinator

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    I'm having no fun trying to find the ultimate enclosure/alignment for this sub. I was excited to see the teaser from John about the EBS 5cuft(F3=16Hz) design. I expected to be able to get even better performance going to a slightly bigger box/lower tuning. But anything bigger, and the response really goes bad (IMO). Couple that with the fact that I'd like to stay with the 250/350W plate amps, and it seems to me that the DVC12 or Shiva (already have one of each) are better choices. The AV12 has the big edge in displacement, but I haven't found a way to get this thing moving! So what's the ideal design for this bad boy? It's a good looking driver, and I'd like nothing more than to remove a speaker grill and show off the beauty making all that bass, I just can't figure out how [​IMG] Any ideas...
     
  2. Jack Gilvey

    Jack Gilvey Producer

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  3. John E Janowitz

    John E Janowitz Second Unit

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    Hi Baldemar,

    In the 5 cubic foot EBS, with 350W input, the AV12 models to have a peak of about 14mm excursion at 23Hz according to BassBox. What we have found though is that this is actually the RMS excursion and to get the real world peak excursion you need to multiply by 1.4, so you are really at close to 20mm. Since most 350W plate amps can put out short peaks or bursts a good deal higher than 350W, an explosion in a movie could drive this woofer to upwards of 20mm excursion. The shiva on the otherhand will run out of excursion at about 250W input in the same enclosure.


    The other thing to keep in mind is that even if only taking advantage of under 20mm of excursion on the AV12, the driver will be extremely linear over this range. The BL in this driver at 20mm is only about 10% less than what it is at rest. As a result, distortion will be very low.

    One other thing to take into account is modeled vs real world performance. The shiva has a BL^2/Re of about 40, where the AV12 has a BL^2/Re of about 76. It has been proven through many tests that woofers with the highest motor strength(Bl^2/Re) will perform the closest to their modeled output. Tom Vodhanel from SVS has all kinds of real world data to support this.

    In any case, even with a 350W amp, the AV12 will have more headroom. You won't have to worry about bottoming since the suspension has much more capable travel. Down low you'll also have more output, and be closer to the simulations.

    John
     
  4. ChristopherW

    ChristopherW Agent

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    John,

    What would be the best amount of power to feed to the AV12 in a thunder 12 box? Is your 350 watt amp a good choice for this alignment?
     
  5. Sebastian

    Sebastian Second Unit

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    Yeah, What would be an ideal enclosure for this bad boy? and what to tune it to?
    3 cubit ft tuned (ported) to 19Hz?
     
  6. Brian Bunge

    Brian Bunge Producer

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    John,

    Sorry to do this here, but you'll probably see it sooner than an email since I sure you get plenty. Anyway, the tracking info. on my PR is the same. Billing information received.

    Brian
     
  7. Sebastian

    Sebastian Second Unit

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    Jack,
    Yeah, that thunder cabinet would be nice with two 15" PR's, but if I build a box for this sub i will not be able to afford the two PR's[​IMG]
    I think two PR's can be had for $100 right now at Acoustic Visions, no one quote me on this. Man, am I poor, time for less expensive hobby,[​IMG]
    I wonder what would be a good weight to use on the PR's 1500g?
    I wonder how much power (watts) would be acceptable to drive this sub, anyone?
     
  8. John E Janowitz

    John E Janowitz Second Unit

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    Brian,
    I'll send you an email about what's going on with that as soon as I'm done typing this.
    With regards to the Thunder12.3 enclosure for this woofer, anywhere from 1400 to about 1800grams looks good. I did a graph showing the two.
    [​IMG]
    Both give an F3 of between 18-19Hz, but the 1800gram PR's will give a little more extension, but a little less output in the mid 20Hz range.
    As far as power goes, the 350W amp will push these to pretty good levels. I'm planning on doing a special on the amps also for the preorder at $170. The woofer will be able to handle even more power than that, but you won't find a bigger amp right now that is that affordable. Keep in mind that the difference between 350W and 700W is only 3dB. For someone building a budget system, you should be more than happy with this combination.
    As far as max power handling, keep in mind the 500W rating is very conservative for this woofer. For a comparison, take the shiva. The shiva is rated at 650W. The VC in the AV12 is much longer than the one used in the Shiva, so there is much more copper to dissipate heat. The wire used is a much heavier guage, again increasing thermal capacity. The VC former is a heavier aluminum former that also is better at dissipating heat. There is also venting under the spider in the basket to aid cooling. The pole vent is flared which also aids in creating better air flow.
    A similar 2" VC that was tested at 77 volts measured on an RMS meter of 20-200hz pink noise for two continuous hours. The peaks were 110 volts. Using 2.97ohm as the DCR of this woofer, we see that current is 25.93amps. Power is I^2 x R, so 25.92^2 x 2.97, giving 1996W that the driver was tested at.
    The 500W rating I have given to this driver is very conservative. You don't have to be worried about throwing more power at it.
    John
     
  9. Pete Mazz

    Pete Mazz Supporting Actor

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    I'm thinking of 4 of the Av12s sealed in a "soffit sub" ~15 cu ft with a LT. [​IMG]
    BTW, do these have the inductance hump of other high excursion drivers?
    Pete
     
  10. Jack Gilvey

    Jack Gilvey Producer

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    John, thanks for the education on motor strength and on Pe...this thing is really sounding good.

    I've often wondered what determined the performance of a woofer around Fb in reflex, as excursion is approaching its minimum. We (well, I) always talk about a certain SPL achieveable at, say, 18Hz, by various high-excursion drivers, but this is usually very close to Fb, and I wouldn't think the "high-excursion" part would come into play at all. Given a certain resonator displacement and power, I guess what's left is motor strength. All else being as equal as possible, how would the performance of two woofers with different strength motors differ near Fb, when excursion is minimal?
     
  11. Baldemar Garcia

    Baldemar Garcia Stunt Coordinator

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    Guys,

    Thanks a bunch for the feedback. I was just making sure I wasn't overlooking something in Bassbox.

    Jack,
    I guess I'm too used to looking for a 'flat' response, so I was a bit disappointed in the AV12 model in this size box. Maybe John was just drawing a comparison to the popular Shiva app, where it's hard to beat.

    John,
    Good info about the conservative power rating. I was kinda scratching my head figuring this driver is best suited in smaller enclosures, which kind of calls for more power to extract max performance. But then I thought we may be thermal limited at 500W. Good to know that's not the case.

    I'll see how my Shiva performs in its EBS enclosure sometime soon (w/250W plate amp), and see if it meets my expectations. Then I'll have some sort of 'baseline' to shoot for or exceed.

    There's still much to learn.
     
  12. Chris.Brunhaver

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    I'm looking at buying either an AV12 or AV15 and still weighing my options. I have an Adire PR15X (the one that was on sale) and one of their 250 watt plate amps. I was looking at doing the 3 cubic foot box tuned to 19 hz with this combo. Though it won't take full advantage of the AV12's excursion, this looks like it would work fine because the PR only runs into trouble at the limits of the amp's power. My other thought was to try to sell my amp and PR and put the money towards a bigger amp and do something vented. Ideally I'd like to do something high power with a couple PR's but I'm pretty short on cash right now. Hmm, have all of these new cool drivers coming out is making life difficult...


    -Chris
     
  13. Chris, you could always get a second PR and a bigger amp when money permits. The 550watt Bash amp may do it for you [​IMG] I wonder how close the cutout fit is between your current amp and the bash amp.
     
  14. Brad Dixon

    Brad Dixon Stunt Coordinator

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    Chris,
    I'm in a similar situation. I'd REALLY like to go with 120L(internal before driver and bracing) max box. So for close to the same money I could go with an AV15 sealed in 105-110L heavily stuffed powered by a QSC rmx850. My other option is an AV12 with 2 PR's in 90L with the 350w plate amp.
    AV15/amp = ~$450
    AV12/PR's/amp = ~$400
    An issue for me is the AV15 route leaves more upgrade room IF I decide to later go with a larger PR'd box(or another HE driver) but I don't really have the room for the amp.[​IMG] To do the AV15 justice it looks like 4 PR's would be needed with ~800w, at least that's my impression when modeling with unibox.
    I have a question about PR'd boxes though. Is placement very critical? The sub will be an end table basically. It will be just a few inches from the sofa. Will this cause problems since one of the PR's will be firing directly into the side of the sofa?
    Brad
     
  15. Magnus Lindqvist

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    John, is it possible to buy the 350W amp at Acoustic-Visions to that price 170$ during the preorder or does one have to get it from you?
    //Magnus
     
  16. John E Janowitz

    John E Janowitz Second Unit

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    Hi guys,
    In case you missed the other thread, the preorder has begun on the website now. http://www.stryke.com
    Magnus,
    We can work out something on that amp for you. Send me an email.
    John
     

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