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Turning an 8 ohms cab in a 2 ohms cab

Turn the HX into a 2 ohms cab

  • Do it, switching back to 8 ohms is not complicated

    Votes: 7 22.6%

  • Trade/sell it, it's safer/better

    Votes: 15 48.4%

  • Don't, it's too risky and complicated and could become an amp killer

    Votes: 9 29.0%
  • Total voters
    31
baxter_x

baxter_x

Nov 27, 2013
5,013
5,362
EU
www.hellofaride.fr
#1
Hello,

I own three Hartke 410 Hydrive cabs (one HX and two HL). All of those cabs are 8 ohms.
I also own 3 amps: Ampeg SVT2, SVT 7 and Sadowsky SA200. Only the SVT 7 can't be used at 2 ohms which is ok as it's mainly used as backup.

My frustration is I can not use my SVT 2 with any single cab as it's a 2/4 ohms amp. I did use it with a single 8 ohms cab but it doesn't seem to perfom very well.
I could use it with two cabs but it's overkill since I don't tour much for the moment. Also, the cab will be used mainly for rehearsing. The HL will be used for big stages and touring.

I could sell/trade the cab for a 4ohms one, but I'm considering turning it into a 2 ohms cab.
There is an thread about it on Talkbass but I can't find it anymore.

Is it easy to do?
Is it a good idea?
 
#6
baxter_x said:
My frustration is I can not use my SVT 2 with any single cab as it's a 2/4 ohms amp.
Click to expand...
Since you have the SVT 2 and the cab you can convert from 8-ohm to 2-ohm, I would try it with the expectations it will only be marginally better. Then, if it’s significantly better, you’ll be happy, but if it’s only marginally better, you won’t be equally frustrated…
 
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#7
I probably would have done it just to see what would happen when I was young and curious. After that I probably would have returned it to 8 ohms. At this point I consider it too much hassle and unnecessary (YMMV)

IMHO leave the cabs alone. Use the SVT 2 when it makes sense to use both cabs. Other wise, choose one of your other amps. This may mean you mainly use the SVT 2 to doink around in you basement or jam space. Not a problem IMHO. Since you only need one cab for gigging these days, you could leave the SVT 2 permanently hooked up to the other two cabs and consider it your practice rig :bassist:.
 
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#12
@Wasnex and @agedhorse
Can you dummy load an amp with resistors to match the amps recommend impedance?
Never tried it myself and it sounds like something that could go wrong fast.
But in theory if you had an 8 ohm cab with a large enough 8 ohm resistor wired parallel with the speaker cab would this let you run the amp at 4 ohms?
Would anything short out or burn out?
 
#14
AK Bass Guy said:
@Wasnex and @agedhorse
Can you dummy load an amp with resistors to match the amps recommend impedance?
Never tried it myself and it sounds like something that could go wrong fast.
But in theory if you had an 8 ohm cab with a large enough 8 ohm resistor wired parallel with the speaker cab would this let you run the amp at 4 ohms?
Would anything short out or burn out?
Click to expand...
You can, but the losses would be worse than any mismatch. The load resistors would need to be large enough to dissipate the additional heat, not trivial.
 
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#15
AK Bass Guy said:
@Wasnex and @agedhorse
Can you dummy load an amp with resistors to match the amps recommend impedance?
Never tried it myself and it sounds like something that could go wrong fast.
But in theory if you had an 8 ohm cab with a large enough 8 ohm resistor wired parallel with the speaker cab would this let you run the amp at 4 ohms?
Would anything short out or burn out?
Click to expand...


It can be done but it's not really a good strategy.

8 ohm cab in parallel with 8 ohm resistor. The resistor will dissipate half of the power as heat. So resistors tend to get hot. As long as you don't exceed the resistors long term power rating, it shouldn't burn out. However the power rating may be dependent on using a heat sink or actively cooling. In other words the power rating may be much lower without the required heat sink.
 
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#16
Wasnex said:
It can be done but it's not really a good strategy.

8 ohm cab in parallel with 8 ohm resistor. The resistor will dissipate half of the power as heat. So resistors tend to get hot. As long as you don't exceed the resistors long term power rating, it shouldn't burn out. However the power rating may be dependent on using a heat sink or actively cooling. In other words the power rating may be much lower without the required heat sink.
Click to expand...
Going in this direction, of course costing more than just some random resistors, are reactive speaker loads. There are some that are 8 ohm and handling 150 watts, or you could try getting TWO Two Notes Captors in 16ohm version, hook them up together to form 'one 8 ohm 200W cab load', and have your regular cab as the other 8 ohm load, thus getting down to 4 ohms in total. One half of the power goes to the cab, the other to the loadbox(es), that additionally might have other features like DI, headphones, cab sims etc.
 
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#18
Balog said:
Doesn’t speaker impedance vary with frequency though? So if you have a resistor that doesn’t do that how would it interact with the speaker’s total impedance?
Click to expand...


The resistance of the resistor remains the same, regardless of frequency.

The impedance of a speaker varies by frequency. The impedance rating is a nominal value.

The combined impedance would still vary by frequency and I believe you can calculate impedance for a specific frequency using:
1749848586673.png
 
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