dual smaller woofers/mids vs. 1 larger woofer?

Discussion in 'Archived Threads 2001-2004' started by MikeMcGrew, Nov 8, 2002.

  1. MikeMcGrew

    MikeMcGrew Stunt Coordinator

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    I am curious as to some of the advantages or disadvantages of having dual 6.5" or dual 5.75" mids/woofs in a speaker like the axiom M22Ti's (listed as a bookshelf) vs. a bookshelf like the JBL s38's which have an 8" woofer. Will the bass/low end on the smaller woofs still be as full/dynamic as the larger woofers because there are two of them or what? I want these speakers for music only and my budget is limited. I am happy with my HT set up (for now) but my fronts aren't great music speakers. The JBL's have kind of a subdued midrange to them and I'm getting a lot or reccommendations for the Axioms. I like the JBL S36's but not much bass there. I'm wondering if the added 5.75" woofer might do the trick. Please, any information would be helpful. Also, is $400.00 a pair about right for the Axioms? Is there another site that maybe has them a little cheaper? Thank's, Mike.
     
  2. John Garcia

    John Garcia Executive Producer

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    The same signal applied to two speakers in a single enclosure yeild a +3dB gain in output. Low end response is not really changed, but the added sensitivity is roughly equivalent to doubling amplifier power. The two midbass drivers can, and often are, crossed over differently. In the end, if executed right, you get better midrange with this type of design. To me, an 8" driver is a bit too large to be effective in the upper midrange.

     
  3. felix_suwarno

    felix_suwarno Screenwriter

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    john can you please describe the definition of a better midrange, in that case?

    thanks
     
  4. John Garcia

    John Garcia Executive Producer

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    I don't think I can describe exactly what the difference is, but there is a noticable difference between the Paradigm's Mini Monitor and the Monitor 5 (V2), as well as the Studio 20 compared to the Studio 40 (though the 40 uses a different bass driver, as do the v3 5s).

    This is not just the difference in volume, because I recalibrated after switching from Minis to 5s (required a -2dB adjustment for the 5s), but the midrange is quite a bit clearer and more full, even though the low extension of the two is not much different. I don't know if it is an effect of the x-over design, or just the fact that there are two mid-bass drivers. The drivers are identical between the Mini V2 and the 5 V2, but the x-overs have to be different (2-1/2 way, I believe). Maybe it is that there is more midrange, not necessarilly better sound. Does that make any sense?
     
  5. AlanZ

    AlanZ Screenwriter

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    I found similar results as John.....I was using a pair of Mini-Monitors as mains until my Monitor 5's showed up, and I was really surprised at the difference between the two. The soundstage is a bit larger, imaging is better, and they seem to reproduce with a bit less effort than the Minis. That's not to say the Mini's aren't a really nice speaker, cause they are. But IMHO, the 5's are significantly better. I would rather have two smaller drivers than one larger.
     
  6. felix_suwarno

    felix_suwarno Screenwriter

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    more midrange? does that mean that the midrange frequency is louder? does that also mean that the frequency response is not flat?
     
  7. Brian Bunge

    Brian Bunge Producer

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    As a general statement, a small driver will have better quality midrange than a larger one. I've compared small to medium sized monitors with 1 or two 5.25" woofers against towers using a single 8" woofer in a two-way speaker. The vocals are a bit muffled with the speakers using an 8" woofer. Vocals are much clearer and more life-like with the smaller drivers.

    Also, the biggest difference I noticed moving from a pair of GR Research A/V-1's (TM design) to the A/V-1+'s (MTM design) was greater power handling, higher sensitivity, and more midbass punch.
     
  8. RichardH

    RichardH Supporting Actor

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  9. Shawn_McCann

    Shawn_McCann Auditioning

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    I have two questions, one about impedance and another about internal wiring in speaker cabinets:

    I've had CSW Tower speakers for almost two years. I have never been happy with the bass output, and could not understand why reviewers said things like "deep, powerful bass". Deep, yes, but anemic for sure. I upgraded from a Sony to a Marantz SR8000 receiver, sounded better but still not much improvement in the bass. I've also tried moving the speakers to different positions in the room, but this doesn't help. This past weekend I decided to open up the cabinets to see what's inside.

    The two 8" bass drivers were wired in series, as are the two midranges and tweeters. I left the midranges and tweeters alone, but rewired the woofers in parallel. Definite improvement in bass output - this is what I was expecting from the speakers in the first place.

    While the sound is much better than before, should I be concerned with the change in impedance this must have caused?

    Also, after spending the money to install 12 gauge wire from the receiver to the speakers I was disappointed to find relatively thin wire inside the cabinets. Would it be worthwhile to replace the speaker cabinets' internal wiring? It appears to be 16 gauge.

    -- Shawn McCann
     
  10. John Garcia

    John Garcia Executive Producer

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  11. Michael R Price

    Michael R Price Screenwriter

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    No, you do increase efficiency by 3db when doubling the amount of drivers regardless of impedance (6db increase of sensitivity from paralleling two drivers). It's just when you start getting near perfect efficiency (well, over 100db at least) when this no longer works the same way; I don't know why but it makes a bit of sense that you couldn't get 200% efficiency by paralleling 100 drivers.
     
  12. John Garcia

    John Garcia Executive Producer

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    Regarding a 3dB gain, I was also incorrect, it is actually a +6dB increase for two drivers with the same signal. However, in this case we are not talking about two drivers reproducing the same frequencies. Each driver is separately crossed over, and reproducing a limited frequency range with the x-over slope between them, still yeilding roughly a +3dB RMS increase overall.
     
  13. Michael R Price

    Michael R Price Screenwriter

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    John and others,
    There are a lot of speakers that run 8 ohm woofers in parallel with baffle step compensation. The impedance is around 8 ohms in the midrange but in the bass it can be 4 ohms or lower because the woofers are effectively in parallel with no resistance in front of them. In this case, the bass sensitivity is increased 6 db because each woofer sees the same signal and hence the output has twice the amplitude.
    Efficiency (1W, 1m) increases 3db for each doubling of drivers (series, parallel, whatever). The sensitivity (2.83v, 1m) increases 6db for each doubling of drivers if they are all in parallel, and stays the same if they're in series; it is a function of the efficiency and the impedance. If you wire two identical 4 ohm woofers in series to get an 8 ohm load, the efficiency increases 3db but the sensitivity remains the same because the resistance is doubled.
    Oy, what a confusing mess! Just buy whatever sounds better. [​IMG]
     

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