Thinking about an 18"

Discussion in 'Amps and Cabs [BG]' started by BigTed, Jul 24, 2003.

  1. BigTed


    Jul 1, 2002
    San Diego
    An engineer buddy of mine who builds super-high-end home theater speakers has decided to help me build a Speaker cabinet. I'm debating building it with a 15" or an 18" speaker. Either would be Eminence Kappas.

    I'm currently using a Avatar 410 with a SansAmp BDDI and behringer mixer as my pre-amp /effects loop (i'm still shopping for a real preamp.) My power amp is a carvin dcm1000.

    My main questions for you all are: Is there any point in building my cab with an 18" if my future Preamp does not have a crossover? Would an 18" be pointless if it's running full-range with the 410 via daisy chaining?

    I play in a spacey Reggae / Funk band. I use a passive jazz with the DOD FX25 on 99% of the time, and various synth effects about 25% of the time.

    Any help or suggestions are a appreciated.

  2. Lockout


    Dec 24, 2002
    I don't think running an 18 full-range would sound very good. However, you could just buy a separate crossover, they usually aren't very expensive. :)
  3. mikemulcahy


    Jun 13, 2000
    The Abyss
    18's at full range sound like a well executed fart. I went the 410-118x2 route. If you dont have the equipment to cut the range going into the 18, stay with the 410 alone until you can.

  4. I ran an 18 full range, and it was fairly tight in the bass region, midd region, with a vintage sounding high end...I'd do it again in a heartbeat...Just gotta have the power to kick the 18's ass....
  5. I ran an old Peavey 1810 and vastly prefered bi-amping it. In my experience, running an 18'' full range has generally sounded like butt-mudd. Pre-amps with crossovers are not that hard to come by. Check out the Max Bass Pre-Amp from Peavey. Plenty of features and a great price. Money wasn't an issue on my latest gear purchase and I still went with the Peavey.
  6. BigTed


    Jul 1, 2002
    San Diego
    Cool... Thanks for the input. I had a feeling that the 18 would need to be bi-amped. Next question:

    Since It looks like i'd biamp it, Would 350 watts (4ohm) be enough to get a descent sound from the Emenince Kappa 15" (4ohm) which is rated at 500 watts RMS?

    Also, where (manufacturers) should I start looking at seperate crossover units?

    Thanks again for the help.

  7. redneck2wild


    Nov 27, 2002
    Memphis, TN
    An 18 would work well for a Reggae / Funk band since it will give you that extra low end. You probably want to use a crossover if you are using a cabinet with an 18 as there is usually a Mid Hump.

    Rolls makes a cheap 2 way active crossover that works well for bass because the crossover frequency can go down to 50hz:
    It also works well as a high pass for use with cabinets that cannot produce frequencies below a certain point. We use one on our monitors set to 75Hz - it really cleans up the monitor sound as opposed to running full range.

    Another thought would be to use a passive crossover though it may be expensive to find a Passive crossover that handles alot of power.

    Some speaker designs will limit the amount of Mids and Highs being put out - such as a Folded Horn or a Down firing design. The Mids and Highs are lost inside the cabinet. It is still better in these types of designs to crossover the signal than to send a full range signal.
  8. Petebass


    Dec 22, 2002
    QLD Australia
    These's an easier way to eliminate the high frequencies from the 18. Whack an inductor in the cab. The value will depend in the speaker and the desired crossover frequency. But a simple 10mH inductor like THIS ONE will give a 6dB per octave rolloff starting at 160Hz for an 8 ohm cab. It should cost all of US$14.00. You can pick whatever crossover frequency you want and adjust the value of the inductor accordingly.
  9. Why?

    The Kappa 18 is a high Qts driver that requires between 12 and 18 cubic feet cabinet volume for correct operation. It is not as sensitive as either of the Eminence Magnum 18" drivers, nor does it have as much Xmax (linear cone movement).

    If you want a loud, super punchy 18" that doesn't sound like a well executed fart, look into a JBL E155. If you want something with more bottom than a JBL, the Magnums will do it for you, but you will need something above 1,200 Hz to handle the highs.

    IMO, it is a complete waste of time and energy building a nice cabinet to house a cheap 18" driver. BTW, I'm a big fan of 18s, but not cheap ones.
  10. BigTed


    Jul 1, 2002
    San Diego
    Thanks for the info. I picked the Eminence Kappa's mostly because I've had good experience with their 10s. I'll take a look at the JBLs. What should I be looking for though, in an 18"? I can't play through them to test which I like, and I'm still learning about frequency response and resistence and crossovers etc.

    Thanks again

  11. Get my spread sheet. Sort DRIVERS by driver size and look it over.

    Look for the calculated sensitivity. This will give you an idea how much juice is required to drive it. A very low sensitivity rating (89 for me) will require multiple drivers and lots of power to get full SPL. At the other end, compare it to the JBL E155 18" or E-V 18BX, which are the top of the sensitivity chain.

    Look for the box size, tuning frequency, and last of all the F3 value. The SBB4 has better transients and is tuned lower, but rolls off higher up than the QB3. This could be perfect for 5 or 6-string players who want to hit low A without farting.

    You will find a loud (efficient) driver that goes low, requires a large box. A loud driver with not much bottom (JBL) will run in a very small box. The JBL has significant rolloff in SBB4, but is tuned at 30 Hz, making it fart proof for 5-strings. I suspect the E155 is the most punchy of the bunch.
  12. Bg,

    I'm about to stick a Peavey Black Widow 18" in a sealed cabinet that is 32" tall by 24" wide by 22" deep. What can I expect?

  13. Frequency response and SPL performance nearly identical to the Carvin RL210.


    Based on your box size and standard bracing, etc, I figure about 7.28 cubic feet net volume in the cab. The Peavey 1801-8 requires 33 cubic feet for B2 operation in a sealed box. It has an EBP of 64, which means it favors a sealed box anyway.

    It has a very high Qts of 0.61

    This driver is gonna ring, for sure. Stuffed into this cabinet, it will have a Qtc of 0.98 with the characteristic mid-bass hump and rapid rolloff. The F3 is around 51 Hz.