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Bag End 15" cab for GK 150

Discussion in 'Amps, Mics & Pickups [DB]' started by greitzer, Aug 21, 2005.

  1. Thinking about getting an extension speaker for my GK MB 150 combo amp, I spied a used Bag End S-15D speaker for $299. It's 15-inch and its impedance is 8 ohms, which would work with the GK 150 combo amp. The Bag End speaker is rated at 400 watts, whereas the GK 150 amp only puts out 150. So it seems like wattage overkill, but the price sure is right.

    Anyone have experience pairing this speaker to the GK 150 combo amp? Anything to watch out for? Thanks in advance.
  2. Ric Vice

    Ric Vice Supporting Member

    Jul 2, 2005
    Olivette, Missouri
    I have owned the GK MB series and one of the first Bag End 15's but since I owned them at different times I never got a chance to run them together.
    The GK Spec Sheet says it will work, so you don't have to turn of the internal speaker. That said, you will be running at 4 ohms (is that right?) with a head that is designed to run optimally at 4 ohms, and that will effect the overall volume of the rig, it should increase some what, however you are driving two size speakers.
    Different size drivers speak differently. To my ears, the bigger the driver has the better the bass response, but smaller drivers respond (recover I guess is the correct term) faster. Techies feel free to chime in and help here. The closest thing I've had to this rig was a GK Series II and the powered extension cabinet that they used to make. It sounded bigger,
    but tended to feed back because of the power increase. I'm not a fan of
    dual cabs for DB, but I hope it works for you.

  3. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    There is no fundamental difference in speed between small and large cones. Bigger cones have more mass, but can be coupled to voice coils capable of supplying greater force. Acceleration (which determines sound pressure) is proportional to the ratio of force and mass. It's like having to think about the power-to-weight ratio in a sports car.

    Of course the above point only applies to what you can do in theory. A more important issue is simply how different speakers are designed to meet their respective market expectations. Bigger drivers are typically tuned lower, which I believe gives rise to the sensation of having slower response. One reason is that you can get deep bass out of a bigger driver with less of an efficiency penalty.

    As an experiment, I tuned a DIY 15" cab with the same response curve as a more typical 10" system, and it sounds quite punchy and responsive. It also turned out to be reasonably compact and inexpensive. But a commercial 15" PA cab is likely to be tuned for more bass, as described above. YMMV, but this is not the tone that is typically desired for upright bass.
  4. Aleph5


    Feb 24, 2004
    That means nothing. You don't need to match wattage ratings. In my 30 years of following audio equipment, I know of no spec more misunderstood and over-emphasized than speaker "wattage." It should be a rough guideline, only, of how much power should be safe before damaging the speaker. BUT... MUCH lower power CAN damage a speaker if it has the right harmonic structure and much higher wattage CAN be safe if it has the right harmonic structure and has lower AVERAGE power. So please don't pay so much attention to wattage. I ignore it almost completely.

    The things I would consider are 1) how it sounds and how it blends tonally with the GK speaker, 2) whether the impedance load is safe, which it is per above--4 ohms total, and 3) will there be a volume balance problem due to the efficiencies (or sensitivities) of the two speakers being different, that is--one being louder than the other for the same signal input.

    People can debate the first point. I don't know. The Bag Ends aren't current favorites for URB; the LDS 1x8 is only $100 more, the Ampeg closeout 10s are $100 less, but Bag Ends still have a good rep, I suppose, and the 15 might put out a lot, if you need volume. On point 3, the GK probably won't match the volume level of the GK, but in my experience it may be close enough to sound like the two speakers generally enhance each other.
  5. I have the GK amp and, as a test, I once paired it with a 15" Flite cabinet. I didn't like the sound. There was something about GK's 12" speaker competing against the boomier 15" speaker - I couldn't set the EQ for a sound that made both of them sound decent. Eventually, I purchased the GK Microbass extension cabinet (12" speaker) and that setup sounds much better.

    Actually, I've experimented with several 15" speakers and I haven't found any that have been suitable for my gear. I'll stick to 12" drivers….
  6. Thanks to all for your replies. These are good points to think about.

    Rob -- ihow much of a noticeable difference is there in volume or sound when you use the GK extension cabinet, as opposed to just the GK amp itself?
  7. There's some additional volume there, sure, but it's not an overwhelming amount. The sound remains more-or-less the same as when using the single speaker.

    The benefit (to me) is that I put the amp in front of me and the extension cabinet way behind me or to the side, but aimed at me. This allows me to crank up the volume - without feedback - when I play with an exceptionally noisy 17-piece swing band.
  8. That would do me just fine. I'm in a similar situation and could use the same benefit. Thanks for your info.