Need more volume.

Discussion in 'Amps and Cabs [BG]' started by thenazz, Aug 5, 2013.

  1. thenazz


    May 9, 2011
    Pensacola, FL
    I play a '76 Precision thru a GK 800RB with 2 10" Celestion and a 15" Black Widow. Anytime I set the volume knob above 12:00, maybe 1:00, I start worrying about blowing speakers. Would adding more speakers to the equation help? Not looking to double my volume, just 25% or so more sound. Oh yeah, there is an open jack on the head. Thanks for any advice.
  2. You'll probably get a better response posting in the Amps forum - this is General Instruction.
  3. dwjazz54


    Jan 21, 2003
    Jersey City, NJ
    How do you set your EQ? It's often the case with problems such as you have described that the player EQs too much low end and not enough mids.
  4. butcher


    May 24, 2011
    What are the Ohm ratings on the speakers you already have? My guess is that the two 10"s are in one cab running 8Ohms and the 15" is in another cab running 8Ohms and you are running one cable out of the the amp to the 2x10 and then one from the 2x10 to the 15.

    If this is the case, you are already running your amp at 4Ohms which is the minimum load. You can't add more cabs to the existing setup.

    The 800RB also has a "high" speaker output that is intended for horns/tweeters and there is an internal crossover to select the crossover frequency.
  5. thenazz


    May 9, 2011
    Pensacola, FL
    I've been running one cable out of the jack that says "SPEAKERS HI" to my 2x10 cabinet and the "SPEAKERS LO" to my 15". There's two jack for each HI and LO (4 total). I don't run the bi-amp feature so should I plug both cabs into the LO jacks?
  6. Plucky The Bassist

    Plucky The Bassist ZOMG! I'm back from the dead! Supporting Member

    Jul 30, 2010
    I'd run both of them out of the speaker lo plugs. Something to consider would also be getting a similar set of drivers, matching cabs ideally. A lot of people mix cabs and like their results, but sometimes you can have issues by mixing driver sizes like in your current rig. Two cabs with 2x10s would be ideal, but IMO 15's sounds best when they are together in a 2x15 cabinet...just my $0.02.
  7. remainthesame


    Sep 24, 2008
  8. butcher


    May 24, 2011
    +1 on all of this.

    Additionally, the "Hi" power section of that amp was not designed to drive a set of 10" speakers unless they are intended for guitar, have a very high sensitivity and no bass response. It was designed to drive a really highly sensitive horn/tweeter that usually can only handle 25-50 Watts and frequencies upwards of 1,000 Hz.

    Are the cabs you have commercial cabs with stock drivers or custom built cabs or commercial cabs with replaced drivers (non-stock replacements)?
  9. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    1 again, plug both cabs from the Lo outputs, and leave that other set alone. That should get you a lot more volume right there. Then, dump one cab or the other, and get 2 identical cabs to get the most from your rig. Actually, you could dump both, and get a bigger 4 ohm cab, like a 610 or 215.
  10. iggy


    Jan 3, 2006
    Both lo outputs are for 4 ohm speakers so how can he plug 2/ 8 ohm speakers into both the lo outputs that are designed for 4 ohms? Shouldn't he use just one lo output jack and run the cabs in series?
  11. butcher


    May 24, 2011
    If his 800RB is like the one in the pic link, the 300W at 4Ohms is for a total minimum load which can either be achieved by connecting both 8Ohm cabs directly to the two "lo" amp outputs (which are likely wired in parallel together internally) or by connecting one cab to the amp and then connect the second cab to the first cab (technically, this would also be a parallel connection, not series).
  12. I beleive the option is there to run both amps mono. You'll get a little extra volume running both cabs off the 300W amp but it may not sound as clean.

    Or you can carry on biamping and add another identical 15 on lows and keep using the 2x10 vertical on top for mid+highs.

    The poster above is confused by the newfangled horn biamp. The old style adjustable crossover and 100W amp handles plenty of mids and highs, just perfect for a 2x10.
  13. butcher


    May 24, 2011
    If this is for his version of the 800RB, the schematic does show an option to bypass the crossover. However, with the spec indicating either an 8 or 16Ohm load on the 100W amp it would seem the design is intended to connect a cab voiced for electric guitar if not a high frequency driver. Doesn't seem like sufficient power to drive a modern 2x10 even if it is just the mid-high freq content being amplified. It would totally depend on the design of the cab being driven by the "hi" amp.
    So, if he has a pair of each set of jacks, his rear panel would be like this one then. Same principle applies, 8Ohm minimum total load on the "hi" amp and 4Ohm minimum total load on the "lo" amp.

    To the OP: what are the scenarios in which you feel like you need more power? What is your signal chain like going into the amp (bass settings, pedals, etc.)? Are you using the input attenuator? What do you have the master set at? When you say you are worried about blowing speakers, what is the cause of your worry - do the speakers sound like they are bottoming out or do you hear undesirable distortion etc.?
  14. There was a biamping GK cab back in the day with a 15 and two 10's, presumably intended for that amp.
  15. karl_em_all


    Jul 11, 2013
    Dimension X
    At lower volumes your set up is fine. But if you're playing at real loud volumes and pushing your amp what you need is two similar 8ohm cabs. Each cab is receiving the same amount of power from the amp and that power gets distributed to each speaker in each cab. With say 2 x 115 cabs, 2 x 410 cabs, or 2 x 210 cabs the power is evenly distributed within each cab and results in a more efficient set up (ergo you can then go louder and not destroy your speakers).
  16. butcher


    May 24, 2011
    +1 Well said. One of the potential problems with mixing different cabs to the same source or "asking" them to compete with each other is that more than likely one of them will reach its functional limit before the other one. When that happens, you can't push one of the cabs to its full potential and you run the risk of damaging the "lesser" cab. This happens not only with sheer volume knob but also eq settings.

    If you are going to keep this amp, which is fine and is a classic that is sought after by many players, then you will definitely want to consider the sensitivity of your potential new pair of cabs rather than the size or "power handling". Sometimes a cab that boasts a large wattage capability is actually less sensitive and requires a large amount of power in order to reach the same volume as a cab that is more sensitive. A large wattage rating does not tell you how loud a cab is but rather how much power it is capable of handling (and with some manufacturers not even that unfortunately). A better measure that is often not provided (let alone honestly/accurately) is "sensitivity" which is measured in dBs.

    A cab's functional sensitivity is dependent on the a combination of the size/tuning of the cab and the sensitivity of its drivers. As a general rule of thumb, the smaller the cab and/or the lower it is tuned the less sensitive it becomes or will not be as "loud" given the same amount of power. Relates to the notion "light, loud, low... pick two."

    With all this in mind, it is possible that you could find a pair of 8Ohm 2x10's that will be louder than a pair of 15" cabs or a 215. They won't be cheap though :)

    Often the better gear shops will let you bring your amp along to try out cabs. Since it is almost impossible to know what a cab or pair of cabs will sound like with your amp based solely on the provided specs you really need to try the combination for yourself (if possible). Hence the vast, vast, vast amount of threads in the amp/cab forums.

    Here are a couple of examples of the difference in sensitivity of drivers. These are two from the same company that are commonly used for bass cabs. The difference is about 6dB, the 15" driver being more sensitive. For reference there is a standard notion that doubling the cone area or doubling the amp power can (big emphasis on the CAN... not necessarily WILL) give you another 3dB of perceived/measured loudness.

    So, with the 10" linked below you get a potential of about 92dB with one driver, 95dB with two (double one driver) and 98dB with four (double two drivers). On the other hand the single 15" starts out with 98dB sensitivity. This means that 4 of the 10's will be as loud as the single 15 (in optimally designed cabs with certain frequency responses etc, etc.) given the SAME amount of power. However, the 4x10 cab has the potential to be significantly louder if provided enough power where the single 15 will have reached its mechanical limit. That's great if you have the extra power on hand, but if you only have the amount of power that the single 15 can handle then the extra potential of the 4x10 is not of much use. So the question "Which is louder, a 115 or a 410?" can only be answered accurately with "it depends..."

    There is much more to it than that, but this is a general/simple illustration just to get you thinking beyond the numbers that are stamped on the terminal plate on the backs of cabs :)

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