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Need advice on adding a sub to my B-18

Discussion in 'Amps and Cabs [BG]' started by JohnP, Jun 9, 2001.


  1. JohnP

    JohnP

    Jun 9, 2001
    Chicago
    Endorsing Artist: Rick Turner Guitars, DTAR, Seymour Duncan,
    Here's my situation- I play dub and freefunk style music using a pbass with flats and a Ren fretless. No slap, no pick, no geddyleeguitarbass, etc. Over the years I have really come to love and know how to use my Ampeg B-18..in a studio I use that and a sansamp or demeter DI to the board. As we all know however, there's not much low end on stage from a B-18, which is rolled off at what sounds like about 100hz to me. (and thanks to Bruce Gavin's sweep generator, I just proved it! )

    I wouldn't care so much if this was the good ol' days when i could count on a real PA and sidefills..i'd just mike the B-18 and run the sans to the mains; hear the lows through the mains/fills..but I find myself lately in a lot of semi-pro/low level gigs where there's no real PA to speak of, not to mention sidefills.. And playing bass in a dub stylee, I need LOW end on stage.

    What i want to do is run a sub that is flat from about 40 to 100 hz, x'overed to the B-18 at around 100hz. Is anyone in this forum doing a rig like this?

    I have tried the EBS powered sub-not enough lows..next on the list is the new Mackie powered sub (outrageous spl claims...), and a Yorkville powered sub, if I can find one here in Chicago. The commercially available PA stuff like Cerwin Vega and Ev is too big to move around. I don't feature spending $2K+ for a bagend elf/pamp/$$$$1x15 either.
    if I had the serious $$, I'd get a Meyers 2x15.

    I am open to doing a DIY sub..and i just started getting the drift on the Sonotube subs.

    I never took this stuff that deep until I started playing a Ren bass, which produces a fundamental you can hear and feel.

    So how about it, anybody have a clue as to what i should do?
    jp
     
  2. MikeyD

    MikeyD

    Sep 9, 2000
    You gave a lot of good info on the type of sound you want, but there are a few things that are still not clear to me:
    1. What is your dollar limit?
    2. How big/heavy a cabinet are you willing and able to haul around?
    3. How much clean power can your amp put out, and at what impedance? Are you willing to upgrade your amp - and if so, how big?

    Answer these, and I'm sure you will get a lot of advice. Getting a fat low end is a tradeoff between efficiency, size/weight, and low-freq. extension.
    - Mike
     
  3. JohnP

    JohnP

    Jun 9, 2001
    Chicago
    Endorsing Artist: Rick Turner Guitars, DTAR, Seymour Duncan,
    :You gave a lot of good info on the type of sound you want, but there are a few things that are still not clear to me:
    1. What is your dollar limit?
    2. How big/heavy a cabinet are you willing and able to haul around?
    3. How much clean power can your amp put out, and at what impedance? Are you willing to upgrade your amp - and if so, how big?
    --------------------------------------------------

    ok..maybe this will help me clarify it a bit better too-

    1) $$ limit - less than $800 for the whole thing, which is why I am leaning toward a powered sub with built in xover, ala the Mackie, or a DIY cab with a used p amp and xover.

    2) size-Nothing "too big". (sorry) Something about the same weight and size as the B-18..possibly bigger, but not an svt or Earthquake jr. I really liked that Earthquake jr.

    3) WHATTS? - right now my amp "puts out" 30 watts..the B-18 that is- the Mackie (I have yet to try) puts out 600watts, and claims an OUTRAGEOUS spl of 120+..which I doubt...so the power amp end of it is up in the air. I know about watts and low end..at least i am beginning to know..but you guys please keep in mind, I "only " need this to go to 41 hz. and be hopefully flat from 40-100 hz

    thanks for any help,
    john
     
  4. Working with flat to 41 Hz defined as -1dB to 41 Hz or lower:

    10" Diamond M5102.8, SPL=85, 0.75 cubic feet
    12" Diamond M3121.4, SPL=89, 1.9 cubic feet
    10" Cerwin-Vega 10D4, SPL=92, 1.7 cubic feet
    10" Cerwin-Vega Stealth 10.4, SPL=93, 2.4 cubic feet

    These all fit into cabs that are not overly large, and the price on these should be fairly reasonable. The Cerwin-Vegas will make more noise which is important if you want to avoid carrying a 3,000 watt amp around.

    IMO, the Rane MX22 is the best 2-way crossover you can buy. They appear regularly on eBay, which is where I got mine.

    You *must* find the rated SPL output of your B-18 so you can correctly power the sub. If your 30 watt B-18 is rated as SPL=95 and you opt for a sub where SPL=92, you will need a 60 watt amp for the sub.

    Also, the B-18 must have an effects loop or line out/in so you can insert the crossover, then pipe the highs into the B-18 and the lows to the sub amp.

    [ edit ]

    This is a simpler method (thanks Joris!) that might be the superior solution:

    Use the subwoofer cabinet simply as a passive crossover connection. A 1st or 2nd order crossover is easy to do for 30 watts, and no electronics or 2nd amp would be necessary. You would ALWAYS be taking the sub cabinet and the B-18 and using them as a pair. This could even be gotten around with a switch, etc that would run in either crossover mode, or B-18 direct mode.

    This would probably require using an L-pad attenuator for under $10 or so to balance the B-18 speaker with the subwoofer. A passive crossover can be built with parts from Madisound at http://www.madisound.com for a reasonable cost.
     
  5. JohnP

    JohnP

    Jun 9, 2001
    Chicago
    Endorsing Artist: Rick Turner Guitars, DTAR, Seymour Duncan,
    Thanks, i am beginning to understand. i will try to get the spl of the B-18.

    I don't think though that using an extension cab powered by the same 30 watts is going to give me enough stage volume..which is what I am trying to achieve here. even if the sub was a bit "louder", i.e. unbalanced to the b-18, I don't know, that wouldn't be such a bad thing in my book.

    This is more in what I have in mind, though the claim of 127db spl seems pretty out there, no?

    http://www.mackie.com/Products/Active/SRS1500/SRS1500specs.asp

    Bruce, where do i look to get the spl levels of the various speakers? and what 15" from Mackie could crank 127 db @ 600 watts??
    jp
     
  6. That's not an outrageous SPL number. It's a full-power SPL rating. 600 Watts adds 27,8 dB to the sensitivity rating of the driver. If the sensitivity is 99,2 dB, then the max SPL is 127 dB. Simple as that. For a 15 inch, a sensitivity rating of 99 dB is not at all uncommon.

    If your 30 watt combo has always been loud enough for you then you might go with a 10" hifi woofer. Hifi speakers have low sensitivity (around 90 dB) but fabulous low end in a very small box. You may need 100-200 W to power it, and to balance it with the B-18.