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Am I going to blow out my cab?

Discussion in 'Amps [BG]' started by JeffVanter, Jan 19, 2014.

  1. JeffVanter

    JeffVanter

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    Hi there, I really could use some help.
    I'm using a cab I got from my local music store because I wanted to support the shop but I may have found that this wasn't the way to go. I also got the head that came with the cab, but the cab was made by somebody. "Ampeg speakers" is what the worker told me they were, but now I may be doubting it.

    It's 240 watts at 8ohms (the cabinet.) No option for 4 ohms.
    The head is suppose to be 350 watts at 4 ohms and something like 240 watts at 8 ohms. On the back of the head, there is NO option for 4 ohms though. Only the 8. Theres two of them in fact.

    The head is this: Hartke HA3500C

    Anyways, my cab is coming out distorted during our practice and I'm unsure why. It's pushing 240 watts at 8 ohms through both the head and cab, and the volume is definitely on full blast with both the tube and solid state control on FIVE. EQ is completely flat.

    The cab OR HEAD also isn't loud enough. Is there a way to push for that full 350 watts even though there is only an option for 8 ohms? Why isn't there an option for 4 on the back of the head?

    Thanks to everyone who puts up with my questions all of the time. I'm trying to learn from those who know about this sort of thing and I understand some people might get frustrated with me. We also have a gig coming up and the thing is on full blast and it isn't LOUD ENOUGH. Sadly :rollno:

    Edit: The only problem I have with being a bassist is the fact that I can never find equipment loud enough to compete with those way too loud guitar players. It really bothers me!

    Attached Files:

  2. swamp_bass

    swamp_bass I love it when a groove comes together Supporting Member

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    Ok, just a review of the quickie checklist:
    • Your bass guitar volume is at max volume with tone controls set to middle?
    • On the amp, compression is set to zero, contours are at zero?
    • Bass guitar is plugged into passive input, not active input?
  3. BawanaRik

    BawanaRik Supporting Member

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    That head should push some air. Supporting the local guy is OK if he supports you.

    That might not have happened in this case. Do some online research and check craigs.

    Or you can try to get guitars turned down. ( Hand me the map)
  4. nashvillebill

    nashvillebill

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    The head is a solid state head, meaning it's output comes from transistors. Most amplifiers of this type (there are a few rare exceptions) are designed with the transistors directly driving the speakers: they do not need, and do not use, a transformer to couple the output to the speakers, like tube amps.

    What does that mean? The solid state amps are limited by the amount of current they can produce at maximum power output. (This limitation comes from the power supply, the transistors, and the heat sinking.) For some amps, they can handle a maximum load of 2 ohms...(the lower the number of ohms, the higher the load). Many amps like yours have a 4 ohm maximum load rating...you should not attempt to run a 2 ohm load on them. (A few amps only can run 8 ohms).

    So--your amp puts out 350 watts into 4 ohms. Why does it only produce 240 watts into 8 ohms? Solid-state amps essentially are constant voltage devices, meaning the voltage they put out at full power is about the same, whether the load is 8 ohms or 4 ohms. And one of the electrical theorems, called Ohm's Law, tells us that V=IR. So if voltage V is constant, and resistance R (your speaker load) goes from 4 to 8, then current I must drop in half. (The numbers you gave aren't exactly half, in the real world, there's a couple of inefficiencies that affect the numbers just a tad).

    Bottom line: there is no "4 to 8" adjustment possible, no way to get your full power into 8 ohms (well theoretically you could put an impedance matching transformer back there, but it's inefficient and heavy, so that's only a theoretical point).

    I would suggest using your EQ to cut your bass and bump your mids up to get more volume.

    Also, check all of the speakers for proper operation. Disconnect the speaker cab from the amp. Take your speaker cable and touch the cable to a 9 volt battery (tip on one battery pole, shield on another) Watch the speaker cones move in and out. Are all of them moving, and are they all moving the same direction? You don't want 3 cones that move in when one moves out!
  5. mbelue

    mbelue Supporting Member

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    How ever many speakers your guitarists have, get double that. That would be a great place to start to be loud enough.
    Homemade cabs for the most part are crap for bass. Really needs to be done right for good results. Sounds like you aren't happy with your cab to me. Craigslist that dud and try and find something you like more, better yet get two.
    Good luck!
  6. Zooberwerx

    Zooberwerx Gold Supporting Member

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    Well, the Hartke head is a known quantity and quite popular here on the forum...the cabinet is not. Unless you can provide some addt'l detail (markings, pic of the jack plate, etc.), our hands are tied. The enclosure could very well be a flaming piece of junk. That being said...

    Try the Hartke head with another speaker enclosure. It is capable on powering one 4 ohm enclosure, or up-to-two 8 ohm enclosures.

    Riis
  7. Masher88

    Masher88 Believe in absurdities and you commit atrocities

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    "The only problem I have with being a bassist is the fact that I can never find equipment loud enough to compete with those way too loud guitar players. It really bothers me!"

    Welcome to the world of Bass playing! You've just described my life for the past 20 years. ;)
  8. BawanaRik

    BawanaRik Supporting Member

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    A 500 watt micro head into an efficient cab is a lot better than schlepping a couple hundreds pound of gear to get a hundreds watts of power.

    Times are good Technology is your friend. A 900 watt micro head and a 610 Schroeder weigh about the same as an SVT head.

    Blast away!
  9. Masher88

    Masher88 Believe in absurdities and you commit atrocities

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    "Also, check all of the speakers for proper operation. Disconnect the speaker cab from the amp. Take your speaker cable and touch the cable to a 9 volt battery (tip on one battery pole, shield on another) Watch the speaker cones move in and out. Are all of them moving, and are they all moving the same direction? You don't want 3 cones that move in when one moves out!"

    THIS!!! DO IT! I've had cabs from big name companies come brand new from the factory with cones out of phase.
  10. aggrokragg

    aggrokragg

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    Have you (can you?) open up the cabinet or remove the grill to ensure one of the speakers isn't damaged? Maybe there is a tear in one of the cones causing it to distort.

    If you have any other music stores near you I'd take that Hartke head to the store, tell them you're shopping around for cabinets, and have them hook the head up to a cab that you know is properly rated and will throw the 350 @ 4 ohms. If you crank it up and it's loud and clear then at least you can isolate the problem is with the cabinet, which I'm guessing it more likely anyway if it's homemade by an unknown source.
  11. Masher88

    Masher88 Believe in absurdities and you commit atrocities

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    I was being facetious, but lemme guess that you don't play in a metal band with 2 guitarists w/half stacks and 100 watt tube heads...and a drummer that hits the skins like they owe him money? ;)

    I regret having to sell my SVT-CL and 8x10...times got tough and I don't have a truck.:bawl:

    My PLX amp is pretty light at 20lbs, though. I am mulling over an additional 410hlf cabinet. :bassist: :D
  12. GreggBummer

    GreggBummer

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    This is an excellent and detailed description of the relationship between the amplifier and speaker enclosure. Short and sweet.
  13. georgestrings

    georgestrings Supporting Member

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    +1...


    - georgestrings
  14. BawanaRik

    BawanaRik Supporting Member

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    I play with a bunch of geezers. I use an Eden with a 110 cab.

    It gets louder than it has any right to.

    And sounds pretty good too.
  15. hastingsbass

    hastingsbass

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    If your cab is an 8 ohm cab, add another 8 ohm to your rig. That will put a 4 ohm load on your amplifier and your amplifier will put out 350 watts. That will give you much more output.
    What you don't want to do is reduce the load (ohms) below your amplifier's load rating. If you add too many speakers you will fry your output device…no matter whether it is tube or solid state.
    If adding another cab doesn't make a big difference, your cab may be the problem. The drivers could be out of phase or…the cab may not be designed properly for the drivers or…the cab speakers may not be very efficient.
  16. BawanaRik

    BawanaRik Supporting Member

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    In general the extra watts won't be noticed.

    A better cab will be noticed.
  17. JeffVanter

    JeffVanter

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    Does it have to be another 4x10?
  18. JeffVanter

    JeffVanter

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    Tone controls are completely flat. EQ is flat. Compression is set to about 2. Bass guitar is plugged into ACTIVE.
  19. BurningSkies

    BurningSkies

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    Having used a 3500 in the past, I can say that the preamps both at noon could be part of your problem. You very well could be clipping the pre in that amp. I found that with passive Jazz and Precision basses it was easy to send too much level to the front end of that amp at '5'. I usually ran mine down in the 9-10 o'clock range and had a healthy amount of signal to drive the amp.

    Also, if you're running the power amp full out and both pre-sections at 5 you're probably also giving that poor cab way too much power.
  20. JeffVanter

    JeffVanter

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    Do I put both tube and solid state at 9 o clock? Or just one?

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