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More Drivers Vs. More Watts

Discussion in 'Amps and Cabs [BG]' started by pablomigraine, Oct 31, 2005.

  1. pablomigraine

    pablomigraine Commercial User

    Feb 9, 2005
    New York
    VP & Managing Director - Willcox Basses
    Experienced giggers, your opinions needed:

    The basic question is, ignoring arguments about SPL and which frequencies are more natually audible etc, which will achieve more volume? For Example: which would be louder:

    1200 Watt Head with a 410 cab
    600 Watt Head with a 810 cab

    Assume all components are top of the line.
  2. MikeBass

    MikeBass Supporting Member

    Nov 4, 2003
    Royal, Oak, MI.
    810 with 600 watts behind it.
    All things being equal (and again lets not get off on a tagent about SPL ratings, fraq responce blah blah blah) a 410 will only move a certin amount of "air".
    The 810 (if being basicly double of the 410-again all things being equal) will move more air.
    Will it be twice as loud?? No but it will be significiantly louder.
  3. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    Agree. The 810, unless it was run by a meager amout of power, and 600 watts should be sufficient for most circumstances.
  4. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    The 810 will be louder, as 600watts might be enough.
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That's a mighty big fly in the ointment, as sensitivity and frequency response has far more to do with acoustical output than either the number of drivers or the size of the amp pushing them, however, if you insist...
    They would be the same. Doubling the number of drivers also doubles the radiating efficiency of the system, resulting in a 3dB sensitvity increase. That 3dB advantage in sensitivity of the 8x compared to the 4x precisely nullifies the 3dB increase in power of 1200w versus 600w.
  6. tadawson


    Aug 24, 2005
    Lewisville, TX
    Seems like folks may be forgetting power distribution issues here. The 410 and should be louder in volume, since you can't make power out of nothing with speakers. What folks fail to consider is that when you go to eight drivers from four, each driver will get half the power, have half the cone excursion, and thusly, both boxes will move similar air. The 810 will (if loaded with the same speakers) have greater power handling, and potentially a better low frequency cutoff due to the larger enclosure, but efficiencies between the two, assuming both are the same type of cabinet, should be similar.

    Also, I am assuming when you talk about a "600w head" and a "1200w head" that you are talking about the power output from the head into that specific cabinet, since power output is obviously dependent on cabinet impedance, which you did not mention.

    Having said that, if the 810 is a 4 ohm cab, and the 410 is an 8, then the 810 will give more output on the same head, because it will be delivering more power . . . .

    - Tim
  7. there seems to be a whole bunch of technical blah* blah* blah* being thrown around here, but for anyone who has actually tried this, you know the 810 with the 600watts will "sound" louder - why exactly that is, I can't fully explain, it just is... (IMO)

    But if I had to make a guess based only on specs, I would have to agree with Bill.
  8. DubDubs


    Aug 23, 2004
    Los Angeles
    I get that you get 3db increase in the cab when you add more drivers and that you get a 3db decrease when you decrease the power by %50 which essentially cancels out but doesn't surface area have an impact on volume too? Shouldn't doubling the surface area of the drivers also have an affect on volume?
  9. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    It is that doubling of the radiating area that gives you the 3dB sensitivity increase.
  10. 12bass


    Jan 2, 2003
    Victoria, Canada
    And what about the matter of power compression?

    Power compression may negate the 3 dB advantage of doubled power into the 4x10" cabinet, especially given that 1200 W into a 4x10" is very likely to be overpowering by a considerable margin.

    I would say that, in practice, the 8x10" with 600 W would be louder (and less likely to have a blown driver too).


    [font=Arial, Helvetica, sans-serif]What is "power compression"? Speaker voice coils are made of copper or aluminum. As these voice coils increase in temperature during normal operation, the DC resistance of the voice coil increases. Greater voice coil resistance means less power transfer from the amplifier. As a result, the speaker will not play as loud when it's "warmed up" as it did when it was "cold". Some speakers may exhibit 3 to 6 dB of power compression. This means that power compression can have the same effect as taking away half of your PA![/font]
  11. DubDubs


    Aug 23, 2004
    Los Angeles
    whoops, missed out on that little fact. I see now.
  12. Power Compression!? Now thats something new to me...!

    I'm interested to see what Bill has to say regarding that?
  13. MikeBass

    MikeBass Supporting Member

    Nov 4, 2003
    Royal, Oak, MI.

    Tim, you state: "but efficiencies between the two, assuming both are the same type of cabinet, should be similar."
    If this is true, then why waste the time even getting a 810?
    All things being equal (both boxes are 4 Ohm, 600 watts from the amp @ 4 Ohms) your saying there is no advantage to a 810 over a 410??? Or did I mis-understand your post?
  14. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I'd say that the scope of the original question has now been greatly exceeded. He asked a simple question in search of a simple answer. Now other factors are being tossed into the equation, and while they are valid points I believe they are going into a level of detail that he didn't want to explore.
  15. tadawson


    Aug 24, 2005
    Lewisville, TX
    Greater power handling and lower frequency response, due to the larger cabinet primarily . . . . as I said above, IIRC.

    In terms of VOLUME for a given input, if both are the same ohm cabinets, then no, you WON'T get more volume - whoever said another 3db for double the driver count is flat out wrong - unless, doubling the driver count takes the cab from 8 to four ohms, where the 3db comes from the additional power it will draw, not from the driver count. As I said before, 8 drivers on 600 watts will simply each work half as hard as 4 drivers on 600 watts . . . . but the power converted to sound will still be very close to the same.

    There are advantages to an 810, but getting more level for a given power than a 410 is not one of them . . . . and my previous comments about cabinet impedances still apply . . . .

    - Tim
  16. AGCurry


    Jun 29, 2005
    Kansas City
    Here's what I wonder about:

    Let's take a single driver, rated to handle, let's say, 100 watts. Is its excursion twice as much at 100W as at 50?

    The power handling capacity of a driver is simply the limit above which the manufacturer says that it might fail. But given the PHYSICAL resistance of the driver, is its response to changes in power linear?

    I suspect it is not. I suspect that there is a point of maximum efficiency - dependent on power and frequency - above which the loudness increase flattens out proportional to the power increase.

    I also suspect this is why, in practice, eight drivers are louder than four, even with less power.
  17. I don't think so. Follow your logic to the end, and let's try the old reductio ad absurdum. For a 4-10 to have the same output as an 8-10, you would have to say that they have the same sensitivity--that is, the same volume for a specified level of input. Yet, by and large, they don't. For example, Acme's B-1 (1-10) has a sensitivity of 90, the B-2 has a sensitivity of 93, and the B-4 has a sensitivity of 96. These figures are obtained with the exact same input, 1 w. And cab impedance would have nothing to do with it--that's only if you're trying to put it in terms of voltage. The three cabs have the exact same drivers--but the B-1 has one, the B-2 has two, and the B-4 has four.

    If your argument is correct, and the only thing that matters is watts per driver, then the relation ought to hold true for any number of drivers. IOW, 800 W into an 8-10 should yield exactly the same volume as 800 W into a 1-10 (assuming the use of identical 10" drivers). If 800 W yields the same volume into either cab, then 1 w should yield the same volume into either one. Since sensitivity is usually figured with 1 W at 1 m, this means that the 8-10 and the 1-10 have exactly the same sensitivity.

    Many, many manufacturers state specs which say the opposite of this.

    Do you know of any cases where a 1-10 has the same sensitivity as an equivalently made 8-10 with the same drivers? I doubt it.
  18. MikeBass

    MikeBass Supporting Member

    Nov 4, 2003
    Royal, Oak, MI.

    Wow, 20 years into this and I was wrong all this time!! :D
    I guess you learn something new everyday!!

    For some crazy reason, I thought a 810 (again all things being equal) it would be louder than say a 410.

    So, is the same principal applied when going from say a 210 to a 410? If so, then wouldn't the 210 be the same as, say the 810? (if it's equal to the 410, and 410 being equal to the 810)

    Having played both 810 cabs and 410 cabs provided as back line gear on many stages/tours, I'll tell ya, from dead on experence a 810 is louder.
    I'm kinda a gear nut and like to know what it is I'm plugging into. And how the experence of that particular rig works comparred to what I own and use(d).
    A 410 while getting the job done quite well, when it comes time to move some air and get loud, an 810 will win hands down.
    Up to a point, yes, it's about equal between the two. And I would say 70% of the time, why bother with a 810 at all.
    But my Carver PM900 bridged is 900 watts @ 8 Ohms, so I usually ask before I plug it in so I don't fry the thing, is louder into a 810 than a 410.

    I can get a 810 Megolith (SWR) stupid loud comparred to their 410. (for the record-I don't like the SWR 810 or 410, but having used both a single SWR 410, stacked 410's & 810, that 810 can get loud as hell!)

    Maybe it's the 4 cylinder Pinto vs. the V8 Caddy-both will do 90MPH, but one isn't gonna do it without an argument!
    The 810 will move more of the frequencies more efficient at a given high volume than a 410, thus being percieved as "louder" IMO.

    I understand what your saying Tim, and for the most part agree with you, but Pinto or Caddy........
  19. MikeBass

    MikeBass Supporting Member

    Nov 4, 2003
    Royal, Oak, MI.
  20. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The technical term for the increased sensitivity resulting purely from using more drivers is called 'Mutual Coupling' and it is a very real phenomena. If you not only double the number of drivers but also wire them in parallel and maintain the same voltage input the resulting sensitivity increase will be 6dB, 3dB from the doubling of the radiating area, 3dB from the doubling of power into the halved impedance load.
    Irrespective of the impedance with an equal wattage input the 8x will be 3dB louder. If the 8x has half the impedance load of the 4x and an equal voltage signal is applied the difference will be 6dB, as per above. No offense intended, but I suspect that you're out of your level of expertise here. One of the earlier references to Mutual Coupling can be found in the article by Klapman in the Journal of the Acoustical Society of America, January, 1940.
    Correct, more or less, there does come a point where mutual coupling ceases to provide any additional sensitivity and all further output gains are purely power derived. With direct radiating drivers that's at about 25% efficiency, or 114dB/watt sensitivity, more or less, depending on the driver and alignment.