Subwoofers: Does size matter?

Discussion in 'Archived Threads 2001-2004' started by Michael Harris, Oct 22, 2002.

  1. Michael Harris

    Michael Harris Screenwriter

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    I am looking at two subwoofers. One a 12" and another is 15". Can one get one that is too big? Right now my listening room is rather small but I want growth room. Any comments would be helpful.
     
  2. Dustin B

    Dustin B Producer

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    Comparing just on size doesn't tell you much. Also need to know linear excursion ability. A 15" driver with an 8mm Xmax will not produce anywhere near the bass a 12" driver with a 20mm Xmax will.

    Then you also have to consider the enclosure (size, design, etc) along with how much power the sub has and its' sensitivity. Having driver T/S parameters helps a lot too.

    With commercial subs you pretty much never have all this information. So you are left with any objective and subject data you can find on the net and from reviewers.

    The Hsu VTF2 (10" driver) will outgun a lot of 15" subs out there. The SVS PCi series and Adire Dharman will too (both use 12" drivers).


    As for having too much bass. You can always turn it down. So you can never have too much bass. But you can be wasting money buying a sub with way more headroom than you'll ever need.
     
  3. Brandon_M_S

    Brandon_M_S Agent

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    all thinks being the same, the 15 will reproduce the lower frequency's better. but all thinks are rarely the same. Dustin hits on the head, box style, power, sensivity, xmax will all vary. also right that you can't have too much bass, cause you can always tweak and turn it down now, and reset it back when you get into a larger room. If its too loud, your too old! :p
    [​IMG]
    brandon
    P.S. Now, anything larger then 18"s is too large. [​IMG]
     
  4. Jon Cheung

    Jon Cheung Stunt Coordinator

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    Yea, Brandon really said what I would say. Comparing a 12 to a 15, the 15 will play lower, I think quite lower than a 12. My sucky 12 only plays to about 50 hertz or so but I have lots of music that goes lower than that which sucks for me. If you want to really feel like your in an earthquake or you want a great back massage, get a 15.
     
  5. Dustin B

    Dustin B Producer

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    It's not the size of the driver that dictates how low it will play (A tweeter could do 20hz, just not at an audible level). There are other parameters combined with the enclosure that determine this. A proper bass reflex design with the 10" Dayton Titanic driver will have no problem toasting a pro audio 18" sub down below 20hz in output. The pro audio subs are design for higher efficiency and sacrifice extension to get it. Their sub 30hz output is almost non existant even though they use multiples of 18" drivers.

    None the less, it takes displacement to generate SPL down low. But there are two factors to displacement. Radiating surface area, and stroke. You multiply the two to get displacement.
     
  6. Shawn Solar

    Shawn Solar Supporting Actor

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    If all you would gain from going from a 12" ported sub to a 15" ported sub is 3db more headroom and 3-4hz lower extension than you might as well stick with the 12" and put the money into a parametric eq.

    Like already stated it is almost impossible to predict the performance of two subs with the same size drivers from different manufacturers so two different size woofers adds to the confusion as there is so many other parameters involved.

    when listening to subs its best to audition how low and how loud and when you get home then use an eq to flatten response in room. A $400 dollar sub with eq will most likely sound better than a $2000 dollar sub without eq(disregarding extension and spl). bass response is very dependant on room acoustics. What subs are you looking at?
     
  7. dave alan

    dave alan Second Unit

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    the answer to the question is short and simple. yes.

    comparable parameters is assumed in the general question.

    size matters...period. unless, of course, you rig the comparison as the above posts have....a tweeter?????

    by the way, i have a pair of 11 cu ft double reflex cabs with 1 evx180a in each....bring that 10" titanic on over any time. (i can hear those software databases humming already)
     
  8. Dustin B

    Dustin B Producer

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    What are these 11ft^3 cabs tuned to? I have no doubt that they would absolutely trounce a 10" Titanic above 30hz. But if they are tuned in the 30hz or higher range, and you take a 10" Titanic in a properly sized enclosure tuned to 20hz, I'm confident the Titanic would outgun them at 20hz. I'm also confident ProSound Lab12 basshorn(pair of 12" drivers) would outgun them above 30hz (http://www.prosoundweb.com/lsp/).
    My point was and still is that you cannot consider size of the driver in isolation and expect to tell anything of value about the sub (the only information given about the subs are one is a 12" and the other is a 15"). If you don't take the other parameters of a sub into account, size means absolutely nothing. If the 18" driver has a tiny Xmax, is put in a cabinet that is too small and tuned to high it could be easily beaten by an 8" sub with a long linear throw in a properly sized and tuned enclosure.
    But yes, if all the other parameters are equal. The larger driver has the same throw and is properly matched to an enclosure, it will outgun the smaller driver. Problem is, in commercial sub design this often isn't the case, especially with larger drivers. Hoffman's Iron law is a major pain the ass. But to my knowledge no one has figured a way around it yet.
    I'd take a 10" Hsu VTF2 over an AudioSource SW15 without hesitation. But there are other 15" subs that I would take over the Hsu without hesitation as well.
    Bottom line is driver size alone means nothing.
     
  9. Tom Brennan

    Tom Brennan Screenwriter

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    Dustin ---Good, sensible post.
    That said I'd rather hear a good big driver like an Altec 515 only going to 45hz than hear that 10"er going to 20hz if that was the choice. But that's a preference not a statement of fact.
    www.chicagohornspeakerclub.org
     
  10. Dustin B

    Dustin B Producer

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    For some things I would too. For other sources I don't think I would (especially action movies). The 10" Titanic driver is a very nice driver. In a smallish room I'm sure it would meet most peoples needs.
    That said [​IMG], I personally use a 260L (9ft^3) bass reflex (6" port tuned to ~16hz) 15" Tempest. As high Vd is tough to get with small drivers.
     
  11. dave alan

    dave alan Second Unit

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    dustin: the ev's have an active hp filter, so the drop below 30 is drastic, but, even down 23db @ 20hz, it's still producing 103db spl. with 600 watts.

    the problem with the dayton in a vented enclosure at 20hz, is unloading of the driver. crank the dayton down to where it's not distorting or clacking....the ev is equal or better @ 20hz.

    tell me more about the tempest. what do you power it with? does it hit x-max when abused? about where will it unload? i'm interested to hear about the details of this sub, and i trust your opinions on the subject.
     
  12. Dustin B

    Dustin B Producer

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    Well with a 20hz tune I'd think the Dayton could do pretty well at 20hz, below 20hz it would run into trouble quick. And I wouldn't be surprized if the roll off below tuning when combined with the highpass of the evx180 was faster than 24dB/octave. I couldn't find any excursion numbers on the evx180, you have them?

    My sub is powered by a 250W plate amp (that amp has been measured at 280W though from a third party). I've never bottomed it, and only heard it distort when I had the sub way hot playing music way louder than I should be on a select few occations.

    According to the sims I can get slightly past Xmax but no where near Xmech with this power at just over 30hz. And because of a rumble filter that kicks in at 18hz I don't pass Xmech below tuning either. So the only thing I can do it clip the amp.

    The 6" port is just over 4x it's diameter so port resonances shouldn't be an issue (and I've never heard any). The tune is somewhere between 16 and 17 hertz. I don't have the tools to measure the actual tune. With the 6" port LspCAD predicts my port air speed never passes 15m/s. And I've never heard any port noise from the thing.

    I've measured on the Rat Shack SPL meter (raw number off the meter) 117dB during the opening scene of LOTR when system is set to 10dB below reference (sub fluxates from 12-7dB below reference during calibration). I have a room mode at 40hz, but I think this peak output frequency (from the SVS waterfall graphs) is at 30hz where I don't have a roommode. I've also measured 117dB from TPM THX intro ball explosion at 5dB below reference.
     
  13. dave alan

    dave alan Second Unit

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    the evx-180a, x-max= 6.35mm

    interesting... my simulation of the tempest (by the way, how do you have it wired, seperate, parallel, or series?)
    shows some strain @ 25hz, vent air @ 20.5 m/s @ 18hz., 115db @ 20hz., 250 watts driven. i also see a rise in amplitude at 30hz from the 18hz high pass (do you know the Q of the high pass?)
     
  14. Dustin B

    Dustin B Producer

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    VC are in parallel. Here's a quote from Adire's site on the rumble filter in the AVA250 plate amp:

     
  15. dave alan

    dave alan Second Unit

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    i'd be curious to know what your program says if you input the following:

    Vb= 6.373 (excluding parts displacement)
    Lv= 21.57 ( both ends flared)
    Vd= 4"
    interior damping: minimal
    active 2nd ord hp= Fx-16.05 Qx-1.93
    Fb= 15
    DVC= parallel
    input 600 watts

    you can build a (much) smaller box for other drivers that see F3 around 20hz, but can take 600 watts without nearing x-max.

    the difference in power brings them much closer to equal output around 16hz, but takes up much less of your living room.
     
  16. Dustin B

    Dustin B Producer

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    Well a Tumult in a 60L sealed enclosure with 1600W and an appropriate LT circuit should be good for over 100dB from 16hz on up (upwards of 110dB once you get above 25hz).

    The trade off you make with the Tempest is size. Tough to do a sub that will compete with a large Tempest that is both small and cheap (Tumult will run you over $1000 by the time you are done, Tempest can be done for less than $400).

    I'm unfamilar with some of the abreviations you are using. Vb is in cubic feet correct? I've never seen Vd related to an inch number before. Assuming Vb is in cubic feet and you want the port tuned to 15hz when 21.5" long, the port would have to be 4" in diameter. Too small for a Tempest IMO.

    Dan has posted a design similar to this before. It will work well, but I feel it limits the Tempest somewhat. If you want similar performance to a Tempest in a smaller enclosure, I'd be looking at the AV12 Stryke should have out by Christmas (but it will require more amp power than a Tempest does).
     
  17. dave alan

    dave alan Second Unit

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    dustin:

    sorry, yes Vb is in cubic feet, Vd is vent diameter. i followed stryke a fews years back, but they showed drivers with no info other than coming soon and never updated their site. i liked one 12" driver they had listed in particular, but could never get info i needed from them.

    amp power is readily available these days, so i don't see that as a big issue.

    tell me about the under $400 deal. the cab must be not much to look at at that price, and doesn't include power, x-over, phase control, etc?

    how important is sub 20hz reproduction?

    it looks like i may need to update my database. it lists the tempest (dec 2000), as having x-max of 16.9 mm. is that incorrect? this might be why i passed on it, as i could never model it to perform near it's Pe rating of 750 watts (parallel).

    sorry for the barrage of Q, but i do value your opinions.
     
  18. Dustin B

    Dustin B Producer

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    Yes, at $400 the finish won't be much (depends on how good you can make inexpensive finishes look), but that price can include a Parts Express 300-794 plate amp (which is essentially identical to the AVA250, just $50 cheaper). Both have a 2nd order butterworth low pass filter variable between 40 and 160hz, 0-180 continously variable phase, level control and a piece of junk highpass fixed at 125hz. Spend a couple hundred more and you can get a HS series amp that has a proper 4th order LR crossover (both high and low pass variable) and a single parametric EQ band. But I rely on my processor (right or wrong) so the subs crossover is bypassed.
    Up it to $500-$600 and you could put a very nice veneer finish on a box style sub. For around $500 if you choose carefully on sock material and use some nice decorative wood on the endcaps and bass plate, you could get a very nice looking sonotube based Tempest.
    16.9mm is correct, but that is one way. So 32.8mm P-P which results in a total linear Vd of slightly over 2.5L. Or a 1L more than the evx180 (assuming the number you gave for Xmax was one way).
    When you build a Tempest in the Adire allignment, EBS allignment or somewhere in between you don't need anywhere near the Pe value to reach the linear excursion limits. If the drivers Pe value is higher than you need to reach Xmax, all is good. The problem comes when it is the other way around. Then you end up destroying the driver before you reach its' travel limits.
    On most music 20hz isn't needed. On some it is. But where you really notice the difference between a sub that can do the last octave well and one that can't is the big action movies. Titan AE (this one is neat, there are a few scenes where I feel the couch and me shaking, but don't hear any rumble [​IMG]), TPM, Matrix, The Haunting and many others all have many scenes that are a very different experience when that last octave can be belted out.
    Stryke has a bunch of stuff actually available now. Check there site again now.
     

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