How Risky is it to Run a 4 ohm Amp at 3 or 3.5 ohms??

interrupting to share a couple of thoughts...

perhaps get another g-k to run as a slave amp? buy used to save a few bucks.

adding another cabinet will help you achieve more 'perceived volume' even if you run it at the higher nominal impedance. i.e. i expect 6 speakers at 12 ohms will be noticeably 'louder' than 3 speakers at 6 ohms.
 
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Purely anecdotal and not related to your amp, but I ran a hartke lh500 at 2 ohms for quite a long time, and it's still kicking.

For me, I'd just run it and see what happens. if it works, then it's fine. If it goes up in a ball of fire, then it wasn't the right product for my needs, and I know not to do it again.
This is a great solution if:

Money is not an option and you don't do gigs where the auditorium is at capacity, the band is kicking at the high point of the show, and the sudden failure of the bass amp doesn't matter even though there's no DI to the FOH.
 
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Guy who designs audio gear here to tell you definitively:

I have no idea. If I had designed that amp, it'd be designed so pretty much no matter what, it'd protect itself from things that were likely to happen. It'd still have a lower limit of impedance where you get maximum power, but it wouldn't blow up if you hooked up another speaker.

Other designers may not be so conservative. So... it's a crapshoot, unless you can find the designer and ask what you can and can't get away with. Sticking with reccomended load impedance is a pretty good idea - unless you like living on the edge. In that case, enjoy the adventure. And have a spare.
 
I don't know if you ever stated what amp you are hoping to run this load with.
It matters because some are rated more conservatively than others.
Maybe yours is really good to 3.5, but they rate it at 4 to be safe.
Maybe it's really only safe to 4.5, but they call it 4 and hope for the best.
In any case, it will be more likely to last if it isn't running at it's minimum all the time.
 
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Z=Xc+Xl+R :D

For all practical purposes, R that you measured is the minimum Z.

It depends. If you are using an Ohm meter you are measuring the actual resistance only.
To measure the combined Xl and Xc you need an impedance bridge.
Or the individual reactance values can be determined mathematically or with the help of a Smith chart.

The resistance does not affect the values of reactances.
And the reactances do not affect the value of the resistances.
Though the resistor can affect certain properties of the combined reactances, by damping the oscillation of the LC circuit. But all of the individual values are still there.

Here's how I like to look at it.
Think of mixing paint. If you want orange, you mix yellow and red. These are your reactances working together. How much of each will affect the hue of the orange you get. But the values of red and yellow you mixed in are still the same. Now if you add a little bit of black, (resistance) you get a darker orange but the hue is still the same, only the brightness has changed.
You can measure the combined brightness with a light meter, but you can not measure the hue or the individual color values without more specialized equipment.
 
I remember working with imaginary numbers in high school calculus, but some of that other stuff that you so kindly summarized for me would take weeks of reading and many head-scratching sessions for me to understand. I do appreciate it, though -- suddenly the electronics "lab" that my folks got me in elementary school seems full of untapped possibilities -- and will try to understand some of it, though I make no promise to grasp the whole any time soon.

Man, if you can handle imaginary numbers, the rest of it will be relatively easy. It's just a matter of familiarizing yourself with the concepts.
They didn't have electronics labs when I was a kid. If I wanted to build an inductor, (electromagnet actually) I had to raid my dad's nail jar and salvage the wire out of some broken toy or appliance. Then I had to rob a zinc-carbon D cell from dad's flashlight. Or cash in a few pop bottles to buy one at the drug store.
 
They exist-- big but not heavy. As I stated in another post- another speaker in series would work better by producing sound instead of heat.
Size of resistors are mostly about how much heat they can handle. I have a couple of 10,000 watt dummy loads at work. The resistors in them are 500 Ohm, 1000 watts each, and they are non-inductive, which really ramps up the price tag. Each resistor is about 18 in long and about 1-1/4 in diam. Each load has 9 resistors.
The whole mash has to be cooled by a large fan.
The resistors are like a couple of hundred $ ea or more, retail.
 
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interrupting to share a couple of thoughts...

perhaps get another g-k to run as a slave amp? buy used to save a few bucks.

adding another cabinet will help you achieve more 'perceived volume' even if you run it at the higher nominal impedance. i.e. i expect 6 speakers at 12 ohms will be noticeably 'louder' than 3 speakers at 6 ohms.

Oh sure! Interrupt a thread that went off the rails a long time ago. ;)

Seriously... what you say makes a lot of sense.
 
I have a 6 ohm 310 and just ordered a second one (Berg HG310). I know I can run them in series for a 12 ohm load and then use them with virtually any SS amp.

The amps I have are only rated down to 4 ohms. Is this similar to the situation with watts in that you can overpower a cab so long as you use good judgement and common sense? Can I hook them up in parallel for a 3 ohm load and not worry about my amps going up in smoke if I don't push too hard?

Also, what about pairing with an 8 ohm cab (Markbass combo amp) which would result in a 3.5 ohm load?

GK tells me I should be ok with my Fusion 800, but the protection circuits may kick in if it's pushed.

I'm sure @agedhorse has some thoughts on this.

I assume you want more power ...

So if you want to run completely mismatched cabs without a bad ohmage problem ... use 2 bass heads ...

Or if you have a nice bass amp already, then add a powered sub to it for additional power and let the sub produce the bottom end and let your existing amp produce low mids, hi mids and treble, and get pa support for bigger gigs.
 
It depends. If you are using an Ohm meter you are measuring the actual resistance only.
To measure the combined Xl and Xc you need an impedance bridge.
Or the individual reactance values can be determined mathematically or with the help of a Smith chart.

The resistance does not affect the values of reactances.
And the reactances do not affect the value of the resistances.
Though the resistor can affect certain properties of the combined reactances, by damping the oscillation of the LC circuit. But all of the individual values are still there.

Here's how I like to look at it.
Think of mixing paint. If you want orange, you mix yellow and red. These are your reactances working together. How much of each will affect the hue of the orange you get. But the values of red and yellow you mixed in are still the same. Now if you add a little bit of black, (resistance) you get a darker orange but the hue is still the same, only the brightness has changed.
You can measure the combined brightness with a light meter, but you can not measure the hue or the individual color values without more specialized equipment.

I was just teasing him because his seemed ready to split open anyway. I don't blame him either, imagine all this stuff with no electronic background! The way I see it, Xc is insignificant, unless you do something ridiculous with cables, Xl can't go below 0 ohms, and R is freq. stable. So if Xl goes close to 0 ohms, you essentially are at R. This is only for driver(s) on a SS amp output. There is plenty of fun to be had with input Z :D I good HP filter should help prevent Xl from going really low. But then you have some Xc :D Aside from commercial home stereo speakers with passive crossovers, I have been passive crossover free and usually one driver per output channel since the late 1980's, which keeps life simple :D Oh, I do have factory front speakers in my Jeep that are two way component speakers. That's the only exception I can think of.

As far as the OP goes, it's simply safest to run cabs with nominal impedance at or above the amp's rating, in this case 4 ohms. It was stated above to just wire them for 12 ohms, and I think that is the best safe bet, then get another if it is not loud enough and parallel the two 12 ohm wired cabs for a 6 ohm total nominal Z and the amp should be very happy. The other option already stated is to get a 2 ohm stable amp. Probably costs less than a 2nd cab. Check Carvin. Use existing pre-amp into that if OP finds the Carvin tone stack is not his cup of tea. Could also just get a power amp and run his pre into that. Of course, know before buying if the existing amp has a line out (effects loop) and the carvin has line in/effects loop. I know the higher wattage amps do, no so sure if the 250 watt does. 500 probably does, but might as well get the 700 for the most bang for the buck. Balanced DI out to a power amp with a bal DI in would be a nice solution. There are some 2.66 (?) ohm rated amps as well, but those eliminate future use of 2 4 ohm cabs in parallel. Many 2 ohm options...

Sorry OP if I made you split open. Your no dummy, just not heavy on electronics training/experience etc. AND smart enough to ask. Please put me in your will for all your gear just in case you do split open trying to get this to work. I hope you find a safe and effective solution. If you make a decision and post your plan, your get the right answers as far as amp safety.
 
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