This may sound silly, I am considering using a guitar head with a 2x12 bass cabinet, is this a doable setup? The head can be 16, 8 or 4 ohms.

  • I am thinking of using a guitar head, sorry. – Slames_James Jan 23 '18 at 17:19

That will work, as long as the impedance (the Ohms) of the cabinet is equal to or more than the impedance of the head. What will be different about it is that a bass cabinet is usually intended to reproduce the full frequency response that is fed to it and therefore will likely sound more fizzy and or boomy than a guitar cabinet would.

Also pay very careful attention to the impedances because I think many bass cabinets are made with lower impedances than guitar cabinets. This is because bass heads are often solid state which can more easily be designed with arbitrarily low output impedances.

  • My Hartke head is 8ohms, Trace and Ashdown both 4 ohms minimum, and I use them mainly with 8 ohm cabs. I'd say that as long as one isn't driving any where near flat out, it won't be a problem. I guess most guitar amps will be either 4 or 8 ohms. An obvious to do is to measure both ! – Tim Jan 23 '18 at 17:54
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    @Tim Many older amps are 16 Ohms. I wouldn't try to measure an output or input impedance. Both should be rated by the manufacturer and clearly labeled. I don't even know how one would measure them, especially the output impedance. – Todd Wilcox Jan 23 '18 at 17:58
  • True about output, but input is straightforward with a meter. Some cabs have the magical disappearing impedance plate. – Tim Jan 23 '18 at 17:59
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    A meter can measure DC resistance but not nominal load impedance, which is a specific point on a curve. Cabinet manufacturers also may tweak rated load impedances to take into account quirks of their designs if a cabinet is overly resonant at any one frequency. You would have to do a sine wave sweep with a tone generator and measure the current through the load to get the impedance curve and then you could get a typical nominal impedance from that, but who has all that equipment and know-how? I just don't use cabinets that have lost their impedance labels. – Todd Wilcox Jan 23 '18 at 18:02
  • Oh. It's just that every speaker I've checked comes max.+/- 10% of the marked impedance. Near enough for jazz... – Tim Jan 23 '18 at 18:06

Back in the '60s, the favourite guitar rig was the Fender bass combo, so it's not a new idea. It will work fine, given Todd's caveats, but you may find it lacks a bit of top end. That will be very subjective - guitar, you, style, and actual cab chosen.

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    Wouldn't it have too much top end? My bass cab definitely has a lot more top end than any of my guitar cabs. I mean my bass cab even has a tweeter and my guitar cabs definitely don't. – Todd Wilcox Jan 23 '18 at 17:58
  • Probably not with 2x12". I put a bullet in a 15" cab, but that was as much for keys as bass. My 4x10" has no tweeter, (although I did build the 2x10" with switchable tweeter), and sounds balanced with either guitar or bass. Must try it with keys! – Tim Jan 23 '18 at 18:03
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    All but three of the 2x12 bass cabinets on Sweetwater's web site have tweeters. Of those three, two of them specifically list a frequency response up to 16 kHz, which is more than an octave higher than a typical guitar cabinet that tops around around 5 kHz. The last one actually might have a tweeter that is just not discussed in the details, it's not clear. It seems to really be meant as a powered sub for a bass rig that also has a top in the form of a 2x10 with tweeter or something like that. An old used cabinet from the 70s probably doesn't have a tweeter. Modern ones usually do. – Todd Wilcox Jan 23 '18 at 18:14
  • Interesting. I'd have though, theoretically, that a cab designed for guitar would have a higher range (register, tessitura?!) than a bass cab, given the main difference between the two instruments. But properly crossed over, it might not make much difference. I do know that p.a. cabs (with tweeters) are great for both keys and bass. – Tim Jan 23 '18 at 18:30
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    Basses need the high end for articulation. Guitars need the high end rolled off to make distortion not sound like a swarm of angry bees literally inside your ears. Guitar amps are really specialized and aren't good for anything else. As you say, keyboard and bass amps are often quite similar and one can be used for the other in a pinch. PA cabinets are much closer to keyboard/bass/acoustic cabinets but usually have even wider and more even frequency response and higher power handling, except for the low end models. – Todd Wilcox Jan 23 '18 at 18:34

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