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2x 10 vs. 4x10, loudness

Discussion in 'Amps and Cabs [BG]' started by MarkMcCombs, Jul 29, 2001.


  1. Is it really true that a 4x10 (or 8x10) will sound louder thru the same amp as compared to a 2x10? Other than efficiency, why or why not?
     
  2. If you double the amound of surface area for identical speakers you will move twice as much air.. the more air you move the more volume you get...
     
  3. There is an additional increase in loudness that comes from what is called Mutual Coupling. This occurs when the bass drivers are close together (less than 1/4 wavelength). What happens is an extra +3dB of loudness because the wave forms join and act as one.

    If you take two identical 2x10 cabs and split them on either side of the stage, you will get a certain SPL. If you stack these same two cabs, using the same amount of input power, they will be +3dB louder than when they are split apart. This is free noise.

    A 4x10 will be +6dB louder than a 2x10 of the same configuration. Everytime you double the input power, you get another +3dB in loudness. This happens when you double the 2x10 to a 4x10. The 2nd +3dB occurs from Mutual Coupling.

    I'd rather carry two 2x10 and stack 'em. Easier to carry.
     
  4. MikeyD

    MikeyD

    Sep 9, 2000
    Thermodynamicists would have a problem with this concept! ;) Strictly speaking, the acoustic power output of the two speakers, whether separated by some distance or stacked, is the same. It's as you suggested, the wavefront's shape is altered so more of that acoustic power is directed forward immediately, rather than wrapping around the sides and rear.
    - Mike
     
  5. Wow, is this right? If that's the case, there's not much sense in me getting more power, since 2x the power of the amp = +3dB ; the money would better be spent getting a bigger cab.(+ 6db )

    Which brings to mind the question of efficiency, if the a 2x10 is rated at 101SPL, and a 4x10 is also rated at 101SPL, is the 4x10 still louder? by 6dB?

    Sorry for my lack of techie/audio knowledge, these things are interesting buy blow my little mind.....!
     
  6. Picky, picky, picky :D

    Beg to differ, but since we're being picky, the wave form wrap around effect is not changed. Only the effective source "size" of the wave form is enlarged. The mutual coupling effect operates like a single driver, but with a larger cone. The benefit of mutual coupling is not achieved from wave form modification, but from the increased efficiency of the driver(s) operating with an effectively larger cone, but without the corresponding larger mass.

    Directional characteristics do not occur until Sd >= wavelength, then output drops -6dB at +/- 45 degrees from axis. This happens far higher up the scale than is used by an electric bass. Beaming begins at approximately 1700 Hz for a single 10" driver and 575 Hz for an 8x10 configuration.
     
  7. BassMisfit

    BassMisfit

    Dec 31, 2000
    Irwin, PA
    Either i'm really dumb, or you're all really smart :) The more I read on the more confusing the posts get, you guys should write a book for the less intelligent to understand this crap.
     
  8. Yep, more amplifier power by a hundred watts doesn't buy you squat. I went from an SWR Bass 750 to a QSC 3000a. I can't get 3,000 watts in real life unless I have the amp plugged into an arc welder outlet that provides 60 amps. Hardly what you find in a bar.

    Where more amplifier power comes into play is when you have more speakers to drive. If you drive a 2x10 with a 100 watt amp, you need a 200 watt amp to drive a 4x10 and still provide the same power to all the speakers. You'll make more noise because you are moving more air.

    SPL ratings are relevant to a specific input power. Some are measured 1 watt at 1 meter, others are measured 2.83 volts at 1 meter. Depending upon the impedance of the cabinet, this can vary. The 2.83 volts at 1 meter is ONLY comparable to the 1 w/1m spec when both cabs are 8 ohms. Using 2.83 volts on a 4 ohm cabinet produces +3dB higher SPL than it would on an 8 ohm cab. This is a Gotcha. 1w/1m is more honest, and easier to compare. A lot of the car subwoofer manufacturers (including JBL!) use the 2.84v thing, and 2 or 4 ohm coils, to get their SPL numbers up.

    As for the difference between the 210XLT and 410XLT ratings.. it must be the cabinet differences. The 4x10 is about 1.4x larger, external measurements. Since both use the EC-1060XL driver, something is mismatched. Doubling the number of drivers requires doubling the amount of cabinet volume. I suspect the 4x10 configuration is cramped on the low end, but they are making up for it using mutual coupling.

    I have no experience with either, but IMO a pair of 2x10 XLT stacked would out perform the 410XLT.
     
  9. whew, so would using a 4x10 w/my V4B be louder than using a 2x10 w/the same amp? I got a little confused when you mentioned 100 watts into a 2x10 and then 200 watts into a 4x10. What it boils down to, is that when I did have a 2x10 cab with my V4B, it wasn't quite loud enough (spare me the "how can that be"?), so I'm wondering if a 4x10 will provide me somewhat more volume than the 2x10 did. By the way, the 2x10 was a Bag End, the smaller one w/o the tweeter; but I think pretty efficient.

    Mark
     
  10. Yes
    :D
     
  11. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Hmm, something sounds funny here (maybe just my relative ignorance).

    First, if what you say is true, why is Eden's XLT only 2 dB more efficient than the 210XLT? It seems that you're assuming a 410 will be mechanically equivalent to 2 210s stacked, which I don't think is necessarily the case. For one thing, I think all of the drivers in the 410 occupy the same space, which is not the case with two stacked 210s (each of which has its own sealed space). Could there be some internal resonances that counterbalance the mutual coupling effect? It seems odd to say confidently that a 410 will be 6 dB louder if actual measurements don't bear that out.

    Second, how is adding more speakers equivalent to doubling the input power? It has nothing to do with input power, as far as I can see; that's the amp's job, isn't it? If anything, the power delivered to each individual speaker would be halved, according to what you said in another post, with the total input power delivered unchanged (leaving aside impedance issues). Isn't it rather a matter of enhancing the conversion of the same input pwoer, so that acoustic output is increased?

    Third, I can't see why a 410 would *necessarily* be 3 (or 6) dB louder if its impedance is double that of a corresponding 210, which, as you know, is often though not always the case. If an amp delivers 150 W into an 8 ohm 410 and 300 W into a 4 ohm 210, is the 410 really going to be 6 dB louder on the gig?
     
  12. No, I am stating a pair of 210XLT stacked will be +6dB louder than a single 210XLT. The 210XLT and 410XLT are NOT the same configuration even though both the 210 and 410 cabinets use the same EC-1060XL drivers. I think the +2dB rating of the 410 model is due to the drivers used in the 410XLT being squeezed into too small a volume.

    Yes, the 410 drivers all share a common space, as does the 210XLT, so the 410 should have twice the internal cabinet volume of the 210 for the drivers to perform identically. Since the 410 is only 1.4x larger (exterior), the 410 performance HAS to suffer because each of its 4 drivers has less individual operating volume than does each driver in the 210 cabinet.

    Mutual coupling is a function of multiple driver cones being within 1/4 wavelength of each other. It is not dependent on resonances. As for +6dB louder, actual measurements DO bear this out. Time, and time again. Search the JBL Sound Engineering manual and the ElectroVoice engineering manuals for "mutual" and you can see the math and the real world measurements.

    Given: SVT4Pro amp head capable of 1200 watts.
    Given: 210XLT rated at 350 watts
    Given: 410XLT rated at 700 watts

    Using the 210XLT, the SVT can only deliver 350 watts before the 210XLT smokes. With the 410XLT, the SVT can deliver 700 watts. This looks like doubling the input power to me.

    This discussion is not about limitations of amplifiers, so sufficient input power is assumed. The 210XLT is going to accept 350 watts no matter what its impedance, as long as the amp can deliver the power. The 410XLT will accept 700 watts.


    At 350 watts input power, the Eden specs guarantee the 410XLT will only be +2dB louder on the gig, than a single 210XLT. However, the 410XLT can accept 700 watts, which is twice the input power (+3dB). At 700 watts, the 410XLT will be +2dB+3dB = +5dB louder than the 210XLT at 350 watts. Again, amplifier limitations are not applicable.
     
  13. MikeyD

    MikeyD

    Sep 9, 2000
    Whew - so many posts, so little time!

    Richard - I think what was meant was that the mutual coupling gives up to 3 dB more sensitivity (note: at low frequencies), and that double the speakers could mean half the impedance, so that the amp might deliver twice the power - hence the second 3 dB boost. I think your focus on the 210XLT vs. the 410XLT is analogous to one I did awhile back comparing the 410XLT with the 810XLT. In both cases, a 2 dB increase in sensitivity was claimed by Eden. If the sensitivity was measured at 1 kHz alone, or using some wide-band noise average, + 2 dB seems reasonable, given that the mutual coupling effect works primarily at very low frequencies.

    bgavin - your post is certainly intriguing, and I have a "top of my head" response, but conversing with you requires employing more science. I guess I'll have to fire up my Bessel Function Guided Missiles! ;) Yuck - I still have some outstanding research in other areas (e.g., horn loading) to do before I can be comfortable jousting on this stuff. It is fun, but very time-consuming. Maybe we'll take it up later.

    In my recollection, for a source to radiate as a point source (omni-directionally with a perfectly spherical wavefront), the wavelength has to be on the order of 10 times (alternately read: "much bigger than") the greatest dimension involved. Here you have to consider not only the diameter of the driver(s) but the surface of the baffle as well. For example, a 15" driver mounted in a 20"x20" baffle will have different directivity characteristics than the same driver in a 200"x200" baffle. The mathematics of diffraction get very messy, and I cannot get into it at the moment. Food for thought, anyway. It is fun.

    - Mike
     
  14. Jousting is not intended, nor is flaming or wearing one's IQ on their shirt sleeve. When a vigorous discussion descends into nit picking, nobody wins. However, being asked to defend a point isn't nit picking. It has crossed my mind that maybe one of the young fellows here reading all this might go on as a leader in the acoustics field. Despite being 2001, we are only on the raw edge of discovery.. so much more is waiting to be found.

    As for Eden specs, I am waiting to be convinced otherwise about the accuracy of their SPL claims. I know we disagree about the degree of involvement that marketing has with a company's products, but I would like to see Eden (and all) state ALL their specs. JBL is the only company that comes to mind for compliance. JBL tells you exactly how the SPL is measured, the frequency range they use during the sweep, the input power, etc etc etc.

    As for horn loading, I have an article about a character who has hooked a ported compression chamber to a bass horn, and gotten a signficantly lower bass response by careful choosing of Fob. All has not yet been discovered.. not by a long shot.
     
  15. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    No, I don't see that. How much power a speaker can handle has nothing to do with how much it's actually getting, surely? The whole point of comparing loudness is to do it at *equivalent* power inputs--otherwise it means nothing. That's why efficiency is usually measured, as you pointed out, according to a standard level of power--1 W @ 1 m. Thus, maximum power handling is beside the point.

    Unless you're saying the cab is *not* louder at equivalent power inputs, which is what I thought we were talking about, but only louder when it receives close to the maximum of its power handling capability (i.e., twice that of the same cab with half as many speakers)? If so, I don't see what advantage a 4-10 could have. To say that a cab is louder when it's getting twice as much power would be a trivial point--of course it would be louder!
     
  16. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    This can't be quite right, can it? In the first place, in practice doubling the speakers often means doubling the cabinet impedance rather than halving it (e.g., Carvin's 2-10 is 4 ohms, but their 4-10 is 8 ohms). In any case, efficiency measurements, if done correctly, as bgavin points out, are not affected by impedance (or, I might add, by either the amp's maximum output or the cab's maximum power handling): 1 W into a speaker is 1 W, no matter how much or how little resistance had to be overcome to get it there. Therefore, if a 4-10 has an efficiency of 104 dB at 1 W @ 1 m, and a 2-10 has an efficiency of 101 dB at 1 W @ 1 m, then the difference can't logically be explainable by a difference in power delivered.

    I admit I'm not an expert, just somebody trying to look at this logically. I wonder if the explanation has something to do with more speakers effectively constituting a larger driver, or with reinforcement of key frequencies, or with simply "moving more air."

    I'm not trying to pick a fight with either of you guys. I'm just trying to understand this, and it's not quite hanging together for me from a logical point of view.
     
  17. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Let's think of the original question again. The guy's V4B can't put out anywhere near the peak continous handling capacity of either the Eden 210XLT or the 410 XLT. So the maximum handling capacity of the two cabs is irrelevant, because it won't be reached. Let's say the amp puts out 200 W at full tilt, and let's assume it will put out that power into either cab (it's a tube amp). According to Eden, there will be a 2 dB difference between the two at equivalent power inputs. So what I'm straining to understand is:

    (1) If the 4-10 were *correctly* proportioned as you suggest (exactly twice the volume of the 2-10), what should the difference between it and the 2-10 be? 3 dB? 6 dB?

    (2) Would a correctly proportioned 4-10 have exactly the same response as two 2-10s?

    As far as the guy's original question goes, though, surely it's not correct to tell him, as a blanket statement, that a 4-10 is going to give him 6 db more than a 2-10. Ideally, that may be true, but I just don't see it proved that this is the case in the real world--in terms of what he can go into a store and buy from a maker like Eden.
     
  18. Then I'm sorry, as I can't think of any other way to show you.
     
  19. Richard Lindsey

    Richard Lindsey

    Mar 25, 2000
    Metro NYC
    Nah, the point wasn't that I don't know the difference between 350 and 700 W. The point was twofold:

    (a) It's incorrect to say that doubling speakers doubles input power, because the amount of power a cab can accept does not necessarily control what an amp puts out. If an amp can only put out 100 W, and it's being run at full tilt, doubling speakers does absolutely nothing to change the amount of pwoer actually reaching the input.

    (b) In any case, power handling is irrelevant to comparative efficiency, which can only be meaningful if input power is kept constant.that it's irrelevant to comparative efficiency, which can only be meaningful if input power is kept constant.
     
  20. thanks, Richard Lindsey. But does anyone know if I've gotten an answer to my original question?

    thanks, by the way, for everyone's input thus far....