Multiple small drivers-What's up?

Discussion in 'Archived Threads 2001-2004' started by Steve WC, Mar 9, 2002.

  1. Steve WC

    Steve WC Stunt Coordinator

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    What's the theory behind multiple small drivers(Especially in a two way system but also in general)?

    When I went speaker shopping the "small" speakers had 1" tweater and one 4,5,6, (take your pick) inch woofer.

    The "medium" speaker had 1" tweater and two 4,5,6,(take your pick) inch woofers.

    The "large" speaker had 1" tweater and three or more 4,5,6, (take your pick) inch woofers.

    What is really gained by adding more small driver's?

    Volume and a somewhat lower response?

    If this is bad for one speaker company should it not be bad for all?

    Thanks for your replies.

    Steve
     
  2. Dustin B

    Dustin B Producer

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    It doesn't gain you any lower response. It just gains you output.

    Curious, why have you come to the conclusion that multiple small drivers is a bad thing?

    I don't know of any audiophile speakers that use 4" drivers. There are a few that use 5.25" drivers. The majority use 6-7" drivers. There are a few that use 8" drivers.

    Also remember that they aren't always two way systems. Sometimes they are 2 1/2 way systems. Which means the tweeter and usually the higher mid/woof are a two way system. Then the lower driver just has a lowpass filter that allows it to help out the other driver usually somewhere from 250-500hz and down.
     
  3. Marc H

    Marc H Second Unit

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    Basically, smaller drivers have less air to push against so they can respond faster and more accurately than larger drivers. The control of the bass is tremendously better and distortion is lowered.

    As long as the over all surface area is maintained, several small drivers can match the extension of one big driver but with better clarity.

    That can be seen in the professional world too; bass players rarely use 12" or 15" drivers anymore but now favour the clarity and speed that multiple ten inch or eight inch drivers have.
     
  4. Dustin B

    Dustin B Producer

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    Exactly how does multiple drivers get you lower extension?

    Take one of those 8" minisubs from Paradigm for example. Take as many of them as you want. I guarentee you it won't matter how many of them you stack together you won't improve the extension beyond what one of them could do. They will just be able to play the range that one could louder and louder.

    There is a lot more to accuracy and transient response than cone size. The enclosure and motor strength has a lot more to do with it than cone size.
     
  5. Marc H

    Marc H Second Unit

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  6. Dustin B

    Dustin B Producer

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    Yes it takes air movement to generate bass, and lots of it to generate the really low stuff (which is why currently there is almost next to nothing that can do good bass with less than a 12" cone). But extension isn't a factor of air movement, its a factor of some other T/S specs. You can get a 3" driver to produce 20hz, just not very audibly. And there are some 15" and 18" drivers out there that can't do 20hz.

    Adding more drivers increases the amount of air you can move and hence the Spl you do over the freqeuncy range the driver can produce. Adding more drivers won't change this frequency range, it will just increase Spl over the same frequency range.

    As a side note, very rough calcualations here, the surface area of a 6" circle is approximately a 1/4 that of a 12" circle. So a pair of 6" drivers would have to travel twice as far as a 12" driver to move the same amount of air. Now keeping that motion linear at the extreme excursion required for the 6" drivers will be very hard compared to the 12" driver. A much bigger factor than the mms difference between the two drivers.

    Also the mms of a 12" driver is around 125grams. Given how strong speaker motors are today that is not a problem to move. I don't know for sure, but I'd be will to bet that the ratio of motor strength to mms of a good 12" driver will be greater than the ratio is in a good 6" driver.

    Also that 125gram cone made out of kevlar impregnated compressed paper is strong enough to have a person stand on it without collapsing. Breakup of a 12" driver at 2000hz may be an issue, but at 20-200hz I highly doubt it.
     
  7. Steve WC

    Steve WC Stunt Coordinator

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    one bump
     
  8. Tom Brennan

    Tom Brennan Screenwriter

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    Marc H---You are confused. Smaller drivers have more of an impedence mismatch to the air in the room that must be moved, thus they have to move farther (and make more distortion) than larger drivers for a given volume and frequency. Multiple small drivers ameliorate this somewhat. Speed is related to high freqency response and such response is a function of motor to mass, power to weight ratio so to speak. There are 15" drivers with powerful motors and efficient coil-gap relationships (read expensive) that respond well past 2000hz and there are many weak-motored small woofers with heavy plastic cones that won't. I think the real advantage to small drivers is simply one of economics; several small drivers are often cheaper than a single large one and they allow the maker to keep the cabinet small and cheap to build and ship. Narrow cabinets are fashionable and easier to sell than wider ones too.
     
  9. ThomasW

    ThomasW Cinematographer

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  10. Brett DiMichele

    Brett DiMichele Producer

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    A speaker can only be as "fast" as it's motor structure

    and suspension system allows it to be. Yes a gross generalizatiuon

    could be said that a cheap large speaker will have slower

    transient times than a expensive smaller speaker. But the

    real truth is that any high quality driver (even an 18") can

    be "fast" if it uses strong magnets, Huge Voice Coils with

    perfect gaps, Tight Spiders and a good floating suspension!

    Right?
     
  11. Steve WC

    Steve WC Stunt Coordinator

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    There has been much useful information gained from this thread but to move it to simpler terms(at least for me):

    Speaker A:

    One 1" tweater

    One 6.25" woofer

    Speaker B:

    One 1" tweater

    Two 6.25" woofers

    Would speaker A sound the same as speaker B if all other factors(room size,cabinet size,power supply etc.) were the same?
     
  12. Dustin B

    Dustin B Producer

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    Given identical baffel layouts (second 6.5" just lower), tunings if ported, crossovers and proportional box volume then yes they should. Just B will be able to go louder, and will require less power than A to reach the same level.

    Provided the tweeter isn't already running out of jam when you push the A to it's limits.

    But if B is an MTM 2way then they definately won't. Should still be close, but they will be different. I don't know what to say if B is a 2 1/2 way though.
     
  13. ThomasW

    ThomasW Cinematographer

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    Brett
     
  14. Tom Brennan

    Tom Brennan Screenwriter

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    Brett---Yes indeed. Saying that a typical hi-fi, mud-magnet motored 6.5" woofer is "faster" than an Altec 515 15" with it's edgewound voicecoil, precise underhung gap and 4.5 pounds of Alnico is like saying a Beetle is faster than a Street-Hemi. And let's not forget that the 15" doesn't have to move as far either. I'm not sure how this analogy actually relates to loudspeaker performence ( I think the impression of speed has more to do with low distortion and good system damping than anything else, which still means the 15 wins though, and sometimes "speed" is simply a lack of bass) but it makes people think.
     
  15. Tom Brennan

    Tom Brennan Screenwriter

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    Steve WC---The speaker with the 2 woofers will have lower distortion in the range the woofers work, also more output in that range. As for other things that effect sound such as dispersion, which will change with the 2 woofers, I cannot say.
     
  16. Tom Brennan

    Tom Brennan Screenwriter

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    Brett---Those used to be in the Parts Express catalog. I never heard them but they seemed to be intelligently designed, I would think they would sound good, they meet my prejudices. :)
     
  17. Brett DiMichele

    Brett DiMichele Producer

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    Tom,
    I you are most likely not a Car Audio nut so bear with me.
    One of the bragging rights of Car Audio is SPL (Sound Pressure Levels)
    While I do not adhere to that school of thought (I am into
    SQ Sound Quality) I know a guy who used all Aura components
    to be "diffrent" and his Aura 18's (free air) running off
    a paultry 85 watts per channel RMS managed to hit 135Db which
    is phenominal at that wattage range!
    The magnet structure is pure neodydium and they are a very
    unique speaker.
    I want to see some images of your gear when you get some
    online. I would like to see some driver pictures of those
    old Altec's too if possible! [​IMG]
     
  18. Tom Brennan

    Tom Brennan Screenwriter

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    Brett---Just hit the www-house icon on one of my posts for a link to my horn website. Some of it's out of date now, email me and I'll email you back some photos of my current rig--Altec VOTs with Edgar saladbowl horns, dual JBL 4648 prosound subs.
     

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