Ohm my god... I just don't get it...

Discussion in 'Amps and Cabs [BG]' started by Joe Nerve, Jun 13, 2021.

  1. Joe Nerve

    Joe Nerve Supporting Member

    Oct 7, 2000
    New York City
    Endorsing artist: Musicman basses
    I just bought an Hartke LX8500. They keep saying its 800 continuous watts, and I have no idea what that means, BUT...

    At 8 ohms its 525 watts.

    If I plug that into an 8 ohm 400 watt cab is that going to damage it, or only if I crank the amp? Is it going to sound like garbage, distort, or whatever?

    Should I have gone for the lower wattage Harktke?

    I will be using it mostly with a GK Neo 212 (600 watts), but are there advantages I might not know about using an amp with less wattage? The other model is 500 @4 ohms and 300 @ 8. I always think that more is better, but I starting to question if I just threw an extra hundred and change out the window
    bassballs27 likes this.
  2. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    If you turn it up too much, it will sound like garbage, distort, and damage the cab. If you don't turn the amp up past the cab's limits, you'll be fine, and you'll have lots of clean headroom.

    You're more likely to damage the cab if you boost the bass frequencies too much, or if you play your bass really hard. A high-pass filter would be a good investment.

    What kind of 400 watt cab is it? And what kind of music will you be using it for?
  3. JRA

    JRA my words = opinion Supporting Member

    no. common sense: can't turn everything up to 10.
    that's right.
    if it does: turn it down...quick...
    no, i think you did the right thing --- if only because i would have done the same! :D
    it doesn't always work the way we want, but if the amp can 'out-do' the cabinets = not a bad thing...back to common sense. ;)

    you're experienced and you'd know if something was goofy. if you think you'd like that piece then it's worth finding out how it can work for you. good luck, joe! :thumbsup:
  4. Joe Nerve

    Joe Nerve Supporting Member

    Oct 7, 2000
    New York City
    Endorsing artist: Musicman basses
    Thanks guys.

    Its a Carvin 115 Micro cab. I probably WON'T be using a whole lot with that, but want to know if its even an option. I have 2 of them and in most instances would be using it with both...

    Hmm.... which raises the next question:

    Do two 8 ohm 400 watt cabinets add up to the 800 that I'm hoping they do? I'm not THAT bad at math, but I still don't really understand how this works.

    I'm also keenly aware of what happens sometimes when you DON'T get this ohm thing right. While in The Nerve we once plugged mismatched speakers into our PA head, and the club had to be cleared out. Thankfully it was a small place and we caught it quickly.
    OogieWaWa and Spidey2112 like this.
  5. No matter the difference, it's only a few db up or down.
    Joe Nerve likes this.
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I'm going to suggest that you are even more careful because in my experience, cabinets like that are not capable of more than 200 watts RMS below say 60Hz. No need to damage your cabinet because of an incorrect assumption that the cabinet can safely handle 400 watts RMS.

    I also suggest that you use both of them, that will take a lot of stress off of the low frequency demands of each speaker due to how the low frequencies couple. I think you will be MUCH happier with the performance this way.
  7. Joe Nerve

    Joe Nerve Supporting Member

    Oct 7, 2000
    New York City
    Endorsing artist: Musicman basses
    Truth be told, I probably will never need to use the 1X15. I have a 1X10 combo that's as loud as anything I'd ever attempt using the single 15 for.

    Are there any advantages to lower wattage heads? Or is it really basically a money thing?
  8. LBS-bass


    Nov 22, 2017
    This is kind of how we did things back in the day. If it starts sounding bad, just back it off. I wouldn't worry about blowing things up unless you're not paying attention.
    31HZ, JRA and Joe Nerve like this.
  9. Matty Koff

    Matty Koff

    Aug 21, 2014
    If it's a tube amp you can saturate the tubes for some overdrive with a lower decibel level with a less powerful amp.

    Other than that, if it's a solid state amp, I generally would opt for the higher wattage amp because it has a volume knob and I can turn that down. Don't get me wrong. I don't think I've ever actually needed 500w. But I would opt for headroom if the choice was between say a 300w amp and a 500w solid state amp. My current 800w beast was more about the brand and the design than wattage though.

    If you think about it, even with cabinets rated equal to or more than the RMS rating of your amp, you could still blow the cabs. If you were to plug in a hot bass and then just dime the input gain and volume something bad is likely to happen, despite all the numbers matching up.

    That being said.. I typically make sure my cabs RMS rating is equal to or more than my amp's output capability because it makes me feel a little safer, but in the end, I still have to use my ears.
    Joe Nerve likes this.
  10. I personally don’t see an advantage to a less powerful head, unless your amp provides drastically more power than the speaker cab can handle.

    This isn’t your first rodeo, you will be able to tell if you’re pushing the speaker too hard. And you know the answer isn’t a smaller amp, it’s add another speaker cabinet.
    Joe Nerve likes this.
  11. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    You'll be fine. Just use your ears. The cab will tell you when it's getting too much.

    An HPF would not only help keep you from damaging your speakers, but will also "tighten up" your tone. If you decide to go that route, ignore any amd all advice from everyone in the universe as to where to set it. Just start playing with it all the way down. Slowly dial it up until it's time to stop. Your ears and cabs will tell you exactly when it's time to stop. It's just too hard to describe what happens when it crosses that threshold.
  12. JimChjones


    Aug 6, 2017
    SE England
    One thing that seems to be confusing you, and its a damn confusing topic, far more complicated than it appears to be.
    Watts ratings of amps are a measure of how much power the amp can deliver without excessive distortion. This does have a relationship to eventual volume. But if you crank an amp up to horrible distortion it may deliver a lot more power than the theoretical rating.
    Watts ratings of speaker cabs are a measure of how much power a speaker cabinet can handle without damage. This doesn't have a significant relationship to volume output*. So if an amp is delivering 50W it doesn't matter if the speaker is rated at 50W, 100W or 500W, you'll get the same volume.

    The result of these two measures in the same units having being of rather different things is the source of myths, confusion and contradictory advice. One school of thought says that your speakers should be rated about double what the amp is, so there's no fear of overloading the speakers if you crank the amp up. Another school of thought says that its good to have plenty of reserve power in the amp so there's no risk of distortion, and all that's necessary is to avoid being stupid with the loud pedal and the amp should be rated maybe up to about double what the speakers are. Neither school of thought is wrong**!

    *There's a measurement called sensitivity which is about how much noise you get per watt.
    ** Especially in hi fi circles you'll find mention of something called underpowering speakers. This is basically a myth, but there's a tiny grain of greatly misunderstood truth at the back of it.
    Last edited: Jun 14, 2021
    byacey and Joe Nerve like this.
  13. ardgedee


    May 13, 2018
    Two 8 ohm cabinets in parallel present a 4 ohm load to the amp. Each cabinet receives half the power and its 400 watt limit doesn't change. What is the amp rated at 4 ohm?

    The reality is that all these numbers are models and averages of complex behavior. The limits of amplifiers are difficult to describe accurately with a couple simple numbers. Any single speaker varies in impedance at different frequencies, and in the bass range reproducing low fundamentals requires more energy (to reach a given level of volume) than higher frequencies, which is one of the ways a high pass filter helps. And speaker sensitivity is also a factor, because a more efficient speaker is louder at a given power level. The combined cabs will be more efficient together than either cab driven alone.

    All of which is to say you should treat the numbers as a guideline for safe use rather than absolute boundaries dividing safe and unsafe: the closer you get to the published limits, the more risk you assume. Echoing comments above that if you use the setup carefully and go easy on the master volume nothing should break.
    Last edited: Jun 14, 2021
  14. yodedude2

    yodedude2 Supporting Member

    Nov 19, 2005
    san antonio, texas
    great points. boldface added for emphasis.
    Joe Nerve likes this.
  15. Black Out Jazz

    Black Out Jazz Suspended Supporting Member

    Mar 2, 2021
    location is overrated
    LX8500 800 watts @ 4 ohms
    525 watts @ 8 ohms
    Joe Nerve likes this.
  16. sxaxsx


    May 23, 2012
    Harrisburg PA
    So your amp is 800 watts at 4 ohms and 525 watts at 8 ohms and you have two 8 ohm 400 watt cabs?
    Then yeah you are good.
    If you use both cabs you have a 4 ohm load with 400 watts going to each cab, so perfect match.
    If you only use one cab you only have a 8 ohm load with 525 watts going to one cab rated for 400. You will be fine as long as you don't blast it with only one cab, if you need more volume plug in the second cab.
    Joe Nerve likes this.
  17. Joe Nerve

    Joe Nerve Supporting Member

    Oct 7, 2000
    New York City
    Endorsing artist: Musicman basses
    Thanks everyone. I still love talkbass... Even after all theses years :) .
    Holdsg, Helix, wave rider and 3 others like this.
  18. JeezyMcNuggles

    JeezyMcNuggles Supporting Member

    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    You're good bro
    Joe Nerve likes this.
  19. chris_b


    Jun 2, 2007
    I was once told by a cab designer that my "high quality" 300 watt 112 would probably only handle 100 clean watts. That was a surprise to me, but as it turned out, the "lack of volume" wasn't an issue at all.

    I used to run a 500 watt amp into 2 of those 112 cabs and it was loud, loud enough for a guitar trio and sounded great. So 200 watts into cabs rated at 600 watts from a 500 watt amp. With this kind of ratio I'm loud enough, get a great sound and keep my gear safe. IMO all the quoted numbers should be taken as a guide, not fact.
    Last edited: Jun 14, 2021
    Joe Nerve likes this.
  20. Spirit of Ox

    Spirit of Ox Supporting Member

    Feb 2, 2012
    Chelsea Mass
    On another note, Joe, how is the LX8500? One of my favorite amps was the old Hartke HA3500. How does it compare to the old amps? I know they've gone through some design changes Hartke always had a nice solid transparent tone.
    I've been rockin a couple GK heads nowadays so not familiar with the new Hartke stuff.
    DrMole and Joe Nerve like this.
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