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2 Cabs on Stage: Stacked or Separated?

Discussion in 'Amps and Cabs [BG]' started by frets4fun, Mar 22, 2006.


  1. frets4fun

    frets4fun

    Mar 15, 2006
    My rig:

    Ampeg B2R (200W @ 8ohms, 350W @ 4ohms)
    Ampeg BSE410 (200W, 8ohm)
    Musicman Stingray

    Mostly play at parties and bars/small clubs.
    Not running bass through PA

    I want to add an extension cabinet--either a 1x15 or a 4x10. Most folks seem to stack these, but why wouldn't you place a cab on either side of the bass drum? Seems like this would allow for better dispersion of the sound AND allow the rest of the band to hear the bass better. What are the advantages of stacking?

    I have a gig next weekend and plan to use my Ashdown EB-180 (1x15) speaker as the extention cab.

    Thx
     
  2. Bobb Nagel

    Bobb Nagel

    Aug 30, 2000
    Chicago area
    I happened to be on the SWR website yesterday and came across this question in the Q&A section. The third paragraph in the response is one answer to your question of extension cabinet placement, but only when the ext cab is identical. I always stack my cabinets, mainly because it puts the sound closer to my head and the preamp within easier reach.

    Q: My rig isn't loud enough, do I need more power?
    A: To effectively double the volume heard by the human ear, it would be necessary to increase the power output rating of the amplifier by a factor of 10. A more effective way to increase the volume from your system is to add additional speakers. Speakers move air, and the movement of air creates pressure in a room. This as commonly known as "sound pressure," and it is measured in decibels (dB).

    Decibels are measured in a logarithmic fashion not unlike the Richter scale. If you are reading 103 dB on a meter and you increase the volume to 106 dB, you've effectively doubled the perceived volume. By adding speakers, you're moving more air, thereby increasing apparent volume.

    There's an interesting phenomenon known as "coupling gain," which happens when like speaker cabinets are placed next to each other or on top of each other, causing them to "couple" and creating a situation where the whole becomes greater than the sum of the parts. You get a "free" 6 dB of gain when the cabinets are placed together. If you normally play at or around 100 dB and you place an identical cabinet on or next to the original, you will more than double the volume perceived by the human ear. Split the cabinets, and you'll hear the volume decrease.
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Destructive phase issues will occur if you have two sources placed 1/4 wavelength or more apart. At 100 Hz 1/4 wavelength is 2.8 feet. Multiple cabs should be placed either very close together or very far apart.
     
  4. +1 to everything above, good info.

    I place my cabs together side by side rather than stacked because they are from different manufacturers (SWR Big Ben 18" & Hartke 4x10XL) so they don't stack quite right, lol. I want to be sure I don't want to loose half my rack and / or my head on top. So side by side it is - and I think it sounds fine that way.
     
  5. MacGroove

    MacGroove Brother of the Groove with a 'Pocket Full of Funk'

    Oct 5, 2005
    Calif.
    If you place them side by side, you'll get more bass responce with cabs on the floor. Stacked if you'd like it closer to your head level to hear or if limited of stage space.
     
  6. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    What a crock.
     
  7. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    More crock. Not only do they not represent the true figures but they seem to be unaware that 10 dB is perceptually equated with "twice as loud".
     
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    They're also unaware that mutual coupling gives an additional 3dB of sensitivity, not 6dB. If the cabs are parallel wired another 3dB of level increase will result, for a total of 6dB, but it's far from free. It's the result of the halved impedance, which doubles the current draw and thus the wattage delivered by the amp.
     
  9. chaosMK

    chaosMK

    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    I would go with the vertical stack. If anything, for the looks.
     

  10. Can you explain please what you mean?
     
  11. anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    I tried placing cabs, (and playing 2 amps), set on either side of the drummer. It worked on some stages, but lots of the clubs I play, have trashy acustics,(boomy-reflective) and with bass cabs split apart, it only seemed to make it worse. For a loud band, I like cabs stacked, (so you can hear yourself). At lower volume gigs, or in a good sounding room, try all 3 setups, and see what works best for you. (If you stack), try your 15 on top.
     
  12. jokerjkny

    jokerjkny

    Jan 19, 2002
    NY / NJ / PHL
    i'm shallow, too. ;) :p

    if i put cabs on both sides of the drum riser, i feel like i'd be intruding on my bandmates' own personal stage space.

    *shrug*
     
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    When outputs from two sources are less than 1/4 wavelength apart their outputs are additive. At 1/4 wavelength they begin to cancel each other out. At 1/2 wavelength apart (180degrees out of phase) they cancel each other completely.
     
  14. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Yeah, that was part of it. But I had such disgust at the time that I didn't stick around to do all the details.

    But it might explain the laughable state of their cab specs ; }

    Incidentally, the amp has to have twice the wattage available to actually GET all the additional non-free dB. I know you are aware, but I'm clarifying for those who aren't.
     
  15. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
  16. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That's actually referred to in the audio engineering community as Allison Effect, after Roy Allison (inventor of the dome tweeter), and is similar to but not the same as cancellation from multiple sources. But the advise is the same, speakers should be placed very close to or very far from boundaries.
     
  17. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Well, basically related, and if one understands one, they have a grasp on the other.
     
  18. Got it, thanks a lot
     
  19. A few weeks ago I saw a nationally known blues band. We arrived early to eat dinner and I noticed the bass setup was an Eden WT1205 into two D410XLT cabs. The cabs were spread out about 5 feet apart with a board across them supporting the amp. I thought that was rather strange. The room is wide and shallow and somewhat difficult to EQ. The stage is about 10 feet deep and 30 feet across, so there is plenty of room for a typical band and this one was only the guitar, bass and drumkit. The room is about 50 feet deep and 125 feet across. I've played this room before with an AG 500 into stacked S210 and S410 cabs, but I thought since this guy is a nationally touring pro, he must know more about the room than I do. Wrong. He was total mud from everywhere in the room. I would stack the cabs.
     
  20. LiquidMidnight

    LiquidMidnight

    Dec 25, 2000
    Our guitarist sets his Mesa 2x12 cabs next to each other, but I think that it may have more to do with the physics of the boxes than anything having to do with sound. They're both slant cabs on fixed casters, so stacking really isn't an option. They're also pretty tall, and would probaly put his rack out of reach if they were stacked.
     

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