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Acoustic coupling of 10s

Discussion in 'Amps and Cabs [BG]' started by Rockbobmel, Nov 11, 2002.


  1. Rockbobmel

    Rockbobmel Supporting Member

    I was planning on getting an Eden D-410XST to put on top of my D-410XLT. I can't even find one new. Except BC, which a trade deal makes shipping prohibitive.

    So, do you think another XLT would give me the 8-10 coupling wall of sound effect?

    Also, if I stack them sideways, will thet help/hinder the effect? All 8-10s would be closer together than standing.

    Would I lose definition if I stood them on the floor side by side?

    I am using a Mesa 400+
     
  2. Bass coupling depends on the location of the listener, RockBobby. Theoretically you can pick up 3db every time you double the number of the same type drivers. In practice the result is generally a bit less than 3db, but let's use that for grins.

    Couple things you need to know about bass coupling. First, the drivers need to be in phase - this generally isn't a problem.

    Second, you lose the effect when the difference in distance between the listener and the first and last drivers in the chain is greater than about 10% - that's why an 8x10 will sound louder than a 4x10 placed at each end of the stage - unless you're in that narrow row that's still the same distance from both speakers.

    You want to keep the cabs as close together as you can, but whether they're stacked on top of or next to each other makes no difference.

    hth -
     
  3. Rockbobmel

    Rockbobmel Supporting Member

    How specific do you mean by the same driver?
    Would mixing an Eden XST and an XLT matter? The XST has "XS" drivers, whatever that means.
    Also the box is tuned different.
     
  4. Mutual coupling requires the driver centers be within 1/4 wavelength of each other. This is frequency dependent. Two 15" drivers with their centers separated by 30" will mutually couple from 100 Hz and lower.

    Link to PDF: Search for "Mutual"
     
  5. Andrew Jones

    Andrew Jones Banned

    Feb 28, 2001
    Northampton Mass

    A long time ago Rick turner or someone who worked at alembic in the early days wrote a artical for bass player mag preaching the advantages of stacking a large colum of bass speakers. He was constantly refering to phil lesh's section of the "wall of sound " PA system they were using in 74 phil had 2 colums of 18 speakers stacked single file virtically on eather side of the stage.

    I think his main point was that the Frequency that we are trying to produce is 28 feet long so in best case senerio youd have a 28 foot speaker but reality say that a speaker that big wouldnt move fast enough to create the transiants needed as well as being impossible to transport.So stacking a colum as high as 28 feet gave a similar effect.

    The part I remember clearly waas him say to this day no modern PA has reproduced bass the way that system did.

    AJ
     
  6. geshel

    geshel

    Oct 2, 2001
    Seattle
    True, it does have an effect (stacking vertically v. stacking horizontally). But the difference is in dispersion - where the sound goes. A vertical speaker column will radiate sound over a wide horizontal area, but a limited vertical area. Same but the opposite for a horizontal column (though the floor gets in way). For two 4x10s I wouldn't expect it to make a lot of difference.
     
  7. Exactly. Lots of PA systems are using vertical line arrays to control vertical directivity down to about 60Hz these days. Like V-DOSC, JBL Vertec, EV X-Line. Actually, even the non-line array EV X-Array system (Rolling Stones, etc) uses vertical line arrays of 2x18 boxes to get vertical directivity at low frequencies. It works quite well :D

    You'd get a bit more from boundary loading if you put two 410s side by each on the floor, but probably not enough to be concerned about.

    Different types of cabinets stacked could have strange effects because the frequency and phase responses would be different. It might sound great, it might not depending on how the cabs interacted. Hard to tell without trying it..
     
  8. Rockbobmel

    Rockbobmel Supporting Member

    When I use my 410+210XLT, I lay the bottom cab on its side, bringing the top 2 10s closer to the bottom 4. It's only 3 inches, but when I use 2 410s the upper and lower ports will separate the two quads of 10s by 8-9"
    If i lay both cabs down, all the 10s will be equidistance.However all the ports will be vertical.
    I am wondering if that makes any difference because the cabs were designed with upper and lower ports.??

    Bruce Gavin probably already answered this, but the 1/4 x cone, tuned thing confuses me.
     
  9. vanselus

    vanselus

    Sep 20, 2000
    Boulder, CO
    None
    Regardless of the science or what other people say, just try different placements. You may hear they sound different. Bring a musician friend to a gig and try different things to see what works & what doesn't. That's the only way you can tell what works for you.

    However, normally people stack their speakers up to ear level so they can hear themselves on stage better...
     
  10. I stack mine to fit the venue requirements.

    We have one regular gig where two 1x15 are side by side, drivers on top, and the 10s are on top of the 1x15 pair, and the rack is on top of the 10s. The entire rig sits out of sight in an alcove on a small stage and faces sideways, straight into the conga player and drummer's left ear. They get the full brunt from the engine room.

    Since bass is non-directional, the big thud and thump gets out to the audience just fine, but the highs get lost. This is the only configuration open to me at this venue, but it works well enough to make the club owner very happy. He says he can't hear my rig so much as can feel it.

    I'm using a dbx 120a sub-synth with this rig, and it takes full advantage of the coupling from the side-by-side closeness of the two 1x15. The cone centers are about 20" apart, so I figure the coupling is good from 150 Hz and down.

    There is a lot of merit in having a Bass spotter in the audience to adjust your levels. Unless you have a wireless, there is no way to accurately determine your levels from the stage. I can barely hear myself on stage, but I'm pounding down the walls at the audience position.