Switching cabinet Ohmage via resistors

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by aortizjr, Aug 17, 2005.


  1. aortizjr

    aortizjr Member

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    So I have a Splawn cabinet that is 16 ohms. I also have an ENGL Vintage cab that is 8 Ohms. Combining these two appearantly will cause some interesting tonal issues since the ENGL will be forced to push more air that it may not be ready to handle. Personally I haven't tried this yet, it was what Scott told me at Splawn

    I would like to convert the Splawn to 8 Ohms, but that will take some speaker swapping and cost some money. And unfortunately 16 Ohm speakers are harder to sell than 8 Ohm speakers.

    But I was searching around and found this:

    https://weberspeakerscom.secure.powweb.com/store/zmatch.htm

    From what I can gather, that is only a switchable array of resistors. But I can probably get two 8Ohm 50 Watt resistors and wire them up to make the cab 8 Ohm.

    Will that work? Will it have any effect on tone? If so what kind? Will it hurt my transformers, speakers, etc?
     
  2. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    First, I dunno that you'll find 50W resistors.

    Secondly, a resistive load will change the sound of the cab because, unlike the resistors, the speakers' resistance varies with frequency.

    Rather than do that, I'd just get a dummy load or attenuator and run it in parallel with the cab.
     
  3. aortizjr

    aortizjr Member

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    Well most dummy loads are made out of just 50 Watt resistors. I can find them as well.

    But it looks like the Weber Z-Matcher is probably just that or his speaker engine dummy load. I will ask him. But basically it looks like it is exactly just a dummy load in parallel or serial.

    But with the resistors I was basically going to do that. Or maybe just build it into the cab itself. The difference is that I can get the 50 W resistors from a few dollars from Ted Weber or Mouser. Add a box and some jacks, maybe $15, but I didn't think about the resistance vs. frequency info. Hmmm...
     
  4. John Phillips

    John Phillips Member

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    The Weber Z-Matcher is an auto-transformer, not a dummy load or resistor network.

    What power is your amp? What power handling is the Engl cab? What impedance outputs does the amp have?

    If the Engl cab will handle at least 2/3 of the power of the amp, and the amp has either 4-ohm or 8-ohm speaker outputs, you don't have a problem anyway. Just plug both cabs into the amp. Yes, there will be an impedance mismatch (the combined load is 5.33 ohms, which is safe from either 4 or 8-ohm amps), and 2/3 of the power will go to the Engl, which may make it sound a little louder, but not that much and it will work perfectly well.

    The loss of power (and frequency change as Alec mentioned) caused by diverting some into a load resistor will mess up the balance between the cabs anyway, so there's really no benefit.
     
  5. aortizjr

    aortizjr Member

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    My amp is 100 Watts. The ENGL cab handles like 240 Watts (4x Vintage 30's) or something. I am not worried about blowing up the cab at all.

    I am sure that it will be safe. 5.33 into 4 is no problem. I should probably just try it out...

    But I guess running the cabs at different powers and the impedance mismatch could have an interesting effect on my tone. I know that Mesa in the Mark series actually recommends doing that, so it might work out.

    Anyway.. so with the Z-Matcher, since it is a transformer, will it make the cabs get equal power? Or will the effects on power to each cab be the same as not having it?

    I figure if nothing else, it will make sure the OT is running at 4.
     
  6. aortizjr

    aortizjr Member

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    Just got an E-mail back from Ted Weber. He said that his Z-matcher will even out the power to the two cabinets.

    Eh... for a $100 bucks it is worth it and I am sure it will come in handy later in life.

    Thanks for all the info!
     

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