Can a cab's impedance be altered...

MadAsAHatter

MadAsAHatter

Well-known member
by adding an appropriate resistor across the output jack or something along those lines?

I ask because I'm wanting a specific bass cab. It only comes in 8 ohms and I need 4 ohms. Replacing the speakers isn't an option and something like a Z-matcher isn't rated for the higher wattage.
 
MadAsAHatter said:
by adding an appropriate resistor across the output jack or something along those lines?

I ask because I'm wanting a specific bass cab. It only comes in 8 ohms and I need 4 ohms. Replacing the speakers isn't an option and something like a Z-matcher isn't rated for the higher wattage.
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Re-wire from parallel to series or whatever.
 
MadAsAHatter said:
by adding an appropriate resistor across the output jack or something along those lines?

I ask because I'm wanting a specific bass cab. It only comes in 8 ohms and I need 4 ohms. Replacing the speakers isn't an option and something like a Z-matcher isn't rated for the higher wattage.
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How many speakers are in the cab you want?

Also, what do you not like about the cab being 8 ohm?
 
Floyd Eye said:
Re-wire from parallel to series or whatever.
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It's a 410 cab with 8 ohm speakers. 4 - 8 ohm speakers are pretty much impossible to rewire into 4 ohms.

Dave M said:
How many speakers are in the cab you want?

Also, what do you not like about the cab being 8 ohm?
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I'm wanting to get a Hartke 410 cab; the ones with aluminum cones. I had a 4.5 XL way back when, miss it, and want to get another or similar. For some unknown reason Hartke doesn't make 4 ohm cabs. They use 16 ohm speakers wired in parallel to make 8 ohm 210's. Not sure why they wouldn't use them to have a 4 ohm 410 option.

It's not that I don't like something about 8 ohms. The heads I'm planning to use them with (through an amp/cab switcher) either have 2/4 ohm taps or 4/8 ohm taps. 4 ohms is the common denominator so I need a 4 ohm cab.

I realize I can get 2 210 cabs and daisy chain them in parallel for 4 ohms, but it's counterproductive as I'd end up spending near 2x as much as a single 410 costs. The idea of altering the impedance is kinda the last ditch effort on the Hartke 410 before I abandon it and look at other things.
 
MadAsAHatter said:
It's a 410 cab with 8 ohm speakers. 4 - 8 ohm speakers are pretty much impossible to rewire into 4 ohms.
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Correct.
But, you could wire them as separate 4-ohm pairs. Don't know if that helps your situation.

MadAsAHatter said:
I'm wanting to get a Hartke 410 cab; the ones with aluminum cones. I had a 4.5 XL way back when, miss it, and want to get another or similar. For some unknown reason Hartke doesn't make 4 ohm cabs. They use 16 ohm speakers wired in parallel to make 8 ohm 210's. Not sure why they wouldn't use them to have a 4 ohm 410 option.

It's not that I don't like something about 8 ohms. The heads I'm planning to use them with (through an amp/cab switcher) either have 2/4 ohm taps or 4/8 ohm taps. 4 ohms is the common denominator so I need a 4 ohm cab.

I realize I can get 2 210 cabs and daisy chain them in parallel for 4 ohms, but it's counterproductive as I'd end up spending near 2x as much as a single 410 costs. The idea of altering the impedance is kinda the last ditch effort on the Hartke 410 before I abandon it and look at other things.
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BLUF: Even not knowing what amp(s) you plan to use, I would NOT recommend a large resistive element(s). It's not impossible, but it's not going to help with any appreciable power and/or loudness benefit.
I'm curious; what is the amp with only 2/4 ohm taps?
 
7704A said:
Maybe I'm missing something, but I don't think the OP cared about this? Just impedance matching?
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Agreed. But, I deviated off course a bit since it gets mentioned a lot. Sorry if it added any confusion.
The impedance matching is why I'm curious about the amps being used, especially the one he says is rated for 2 or 4 ohms (but apparently not 8).
 
Dave M said:
But, I deviated off course a bit since it gets mentioned a lot.
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Ah ok, carry on. I do hear it mentioned every now and again. I assume you're stating it won't help in the sense that even delivering half the power to the resistor only cuts 3dB from the speaker output?
 
Dave M said:
I'm curious; what is the amp with only 2/4 ohm taps?
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It's my Blue Voodoo 300, the one that utilized an SVT power section. I run SVP-CL and SVP-Pro preamps through the return for a makeshift SVT. It sounds pretty darn good like that. Not exactly like a vintage one, more like it was one of the various iterations Ampeg released over the years. Bonus that I can run the Voodoo as is for a different flavor that works well too.
7704A said:
Maybe I'm missing something, but I don't think the OP cared about this? Just impedance matching?
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Yeah, I'm not looking for volume or power benefits, just matching the impedance and not blowing anything up. I read a few things on car audio that do put a resistor across a speaker to match impedance and wondered if it could apply to guitar cabs.
 
MadAsAHatter said:
It's my Blue Voodoo 300, the one that utilized an SVT power section. I run SVP-CL and SVP-Pro preamps through the return for a makeshift SVT. It sounds pretty darn good like that. Not exactly like a vintage one, more like it was one of the various iterations Ampeg released over the years. Bonus that I can run the Voodoo as is for a different flavor that works well too.

Yeah, I'm not looking for volume or power benefits, just matching the impedance and not blowing anything up. I read a few things on car audio that do put a resistor across a speaker to match impedance and wondered if it could apply to guitar cabs.
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Ah, tube amp with no 8-ohm tap.
I also run a SVPCL. Great sounding preamp.
 
MadAsAHatter said:
by adding an appropriate resistor across the output jack or something along those lines?

I ask because I'm wanting a specific bass cab. It only comes in 8 ohms and I need 4 ohms. Replacing the speakers isn't an option and something like a Z-matcher isn't rated for the higher wattage.
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Not really. Resistance is applicable to DC where’s impedance is more applicable to AC and the impedance is not linear across all frequencies. Impedance measures
different at different frequencies will yield different reading.
 
You’d be hard pressed to find a factory 4ohm 410 I think. They were generally made thinking they’d be stacked with another cab. Hail Mary but maybe reach out to Hartke support and see if they would make them for you?
 
How much power? If it’s not too much you could use a reactive load box in parallel. It would just be a silent speaker…eating power and probably punch tho.

I remember an old bass player I played with used a 1x15 with a 2x10 on top. But they weren’t the same impedance, one was 4 ohm and one was 8 ohm. That’s around 5.3 ohms but I can’t remember what he set the amp at. It was a Peavey SS head and that rig sounded amazing. Only mentioning it for ideas.
 
SpiderWars said:
How much power? If it’s not too much you could use a reactive load box in parallel. It would just be a silent speaker…eating power and probably punch tho.
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He mentioned a Blue Voodoo 300 which Crate says is 300W RMS at 4 ohms.

SpiderWars said:
I remember an old bass player I played with used a 1x15 with a 2x10 on top. But they weren’t the same impedance, one was 4 ohm and one was 8 ohm. That’s around 5.3 ohms but I can’t remember what he set the amp at. It was a Peavey SS head and that rig sounded amazing. Only mentioning it for ideas.
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4 and 8 ohms parallel are actually 2.66 ohms.
 
Dave M said:
He mentioned a Blue Voodoo 300 which Crate says is 300W RMS at 4 ohms.



4 and 8 ohms parallel are actually 2.66 ohms.
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Oops, 5.3ohm is 16ohm and 8 ohm in parallel, not 8 and 4. But I just pulled that 5.3 number from memory. So now I don’t remember wtf he had. But it sounded killer because the 2x10 cab sort of dominated the 1x15 cab. The 1x15 just gave it more depth and muscle.
 
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