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What happens when two speakers are used together?

Discussion in 'Amps and Cabs [BG]' started by cjazz50, Aug 6, 2002.


  1. Suppose you have one speaker puting out say, 90 dB. What happens when you put two of them together and they are both putting out 90 dB? Does the acoustic energy simply double and the volume go up by 3 dB? Or is there some other effect?
     
  2. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    From what I understand that yes you get a 3db bump. But when I added a second cab to my rig I noticed that the tone became deeper and richer (for lack of a better term) also.
     
  3. FalsehoodBass

    FalsehoodBass

    Jul 22, 2001
    Denver, CO
    Yea... since the dB scale is logarithmic, 2X the power equals a rise in 3dB. It gets tricky because the human ear isn't linear either. In general, a 10dB increase is percieved to the human ear as a doubling of volume.

    Swingbass, the deepness added is due to an effect called mutual coupling. If two speakers are within 1/4 wavelength of each other, they act as a single, larger cabinet with twice the power in the direction they're pointing. Since lower frequencies have longer wavelenghts, the effect works better for bass frequencies. This is the reason that an 410 will, in general, have better bass response than a similiarly built 210, and an 810, more so than a 4...
     
  4. Golem II

    Golem II

    Jan 4, 2002
    Macon, GA, USA
    Stacking cabs also elevates the top cab, increasing the apparent volume without decoupling the rig from the floor. Height is yet another reason why 8x10's are louder than 4x10's.

    I'd like to know, how does speaker surface area factor into the volume equation?
     
  5. FunkySpoo

    FunkySpoo Supporting Member

    Feb 6, 2002
    (Groovy Austin Powers voice on) I wanna hear more about the mutual coupling, grrrrr, yea baby yea. (groovy Austin Powers voice off)
     
  6. You get a bunch of baby speakers. :D
     
  7. me too, can anyone explain in detail, maybe joris? i was looking at specs the other day and noticed that a given 4x10 has lower frequency response than a matching 2x10.
     
  8. geshel

    geshel

    Oct 2, 2001
    Seattle
    That's probably because of either or both:

    1. larger per-driver volume in the 4x10
    2. lower tuning frequency in the 4x10 because it's easier to tune a larger box to a low frequency (can use shorter ports relative to the box dimensions)

    GolemII, speaker surface area is factored into the sensitivity spec to begin with. So a 15" gets an inherent dB boost over a 10" because of the larger area. Problem is, that's countered by increased mass. Depends on the details to know which effect is greater.

    Also, if anyone was curious, I think 100% efficiency turns out to be something like 114dB 1w/1m. So, if a Goliath Sr. is really 110dB 1w/1m, it's still under 50% efficient! A really inefficient hifi speaker at 84dB 1w/1m is only 0.1% efficient: 99.9% of the power is wasted!
     
  9. so if you play a 2x10 and then add another 2x10, you won't extend your frequency response?
     
  10. geshel

    geshel

    Oct 2, 2001
    Seattle
    I don't think so. They'll reinforce each other a bit in the bass range, so the whole band will get a little louder relative to the mids and highs, but it won't go any deeper.
     
  11. FalsehoodBass

    FalsehoodBass

    Jul 22, 2001
    Denver, CO
    i disagree. If you ever get a chance, take your two 210's, and run them on opposite sides of the stage. Listen.
    Now stack them together and notice the difference. The lows are accentuated. This is due to the effects of mutual coupling. The speakers, when placed close enough together work effectively as a single, larger speaker. Shorter wavelengths (highs) aren't as affected because the speakers are too far apart in relation to the wavelenths. Since only lower frequencies experience this, you hear the lows being boosted.

    If you've ever had physics in high school or anything, remember young's double slit experiment. The farther the seperation of the slits (speakers) in relation to the wavelength, the less the effect.

    If you don't believe me...
    Click here for a thread about a year ago where i learned about this stuff. I've since taken an optics course that described the effect a little more in depth.

    Dance & Swing.... if you check out that thread I think most of your questions will be answered.
     
  12. geshel

    geshel

    Oct 2, 2001
    Seattle
    Isn't that exactly what I said? The lows will be boosted. They won't go any deeper however! If 30Hz was 10dB below 40Hz, it still will be. It might be 3dB higher relative to 200Hz than it was before, but with the rest of the bass lifted too that won't be noticeable.