8 ohm v 4 ohm

[kawika5150]

If you have two 4x10 4 ohm cabs and replace them with two 4x10 8 ohms, how much of a difference in volume would be the result? Barely noticeable?

[Pollinator95]

Depends on the wattage difference. BUT having an extra cab (someday) will more than make up for it.

[spaz21387]

depends on your amp tube amps can run at 2 ohms( running 2 4 ohm cabs) but most amps dont like being ran at 2 ohms. running 2 8 ohm cabs puts you at 4 which is ideal and draws the most power from your amp.

[Sartori]

Er, saying "tube amps can run at 2 ohms" is misleading. You seem to be implying that all tube amps can do this, when many most certainly cannot.

[Gintaras]

there are a lot of heads that can run 2 ohms. i have a Genz Benz Neopak that I run (2) 4 ohm cabs. Also some or most of the Carvins.
There is a thread on this forum that has a list of 2 ohm capable heads.

[Pilsener]

Half the impedance will double the output power. Doubling the impedance will halve the power.
At least theoretically, according to Ohm's law.

BUT: This depends on the amp's construction.
An ideal amp will do this, and I have seen a few, yet very very expensive, hi-fi amps that offers such specs.

Most amps will not double the effect due to limitations in the amp's construction and power supply, but you will probably get ca 50% increase in output power by halving the impedance.
As an example, a Peavey Tour 700 bass head is rated 500W/8 Ohms and 700W/4 Ohms.

HOWEVER: Check the manual for your amp to see what the minimum impedance load rating is. To lower from 8 to 4 Ohms is in most cases OK, but not all amps can handle 2 Ohms.

Regarding tube-amps: If the output transformer has a 2 Ohm tap, then it will be OK. Don't attempt to run 2 Ohms load on the 4 Ohms tap on a tube-amp.
It will overload the output tubes and/or the output transformer and/or the power transformer (whatever burns out first).

[billfitzmaurice]

Originally Posted by Pilsener

Doubling the impedance will halve the power.

Only at low power. At full power the difference is closer to a 40% reduction in power. That's moot in any event, as power is only 1/3 of the equation of power/sensitivity/excursion that determines output capacity. Worst case you'd lose 2dB output, in most cases you don't lose anything.

[JonnyAngle]

To be honest, its not worth spending the money on the new cabs. The 4ohm cabs will be louder, however not that much louder. If you need more volume, you're better off spending the money on a more powerful amp

[MuzikMan]

In many cases driver discplacement limitations will dictate max volume, not power. If your speakers can't move any farther then it doesn't matter if you add 10 times the power, they won't get any louder. This scenareo happens more often than not.

[T-Bird]

Hi.

Did You guys read the op?

Originally Posted by kawika5150

If you have two 4x10 4 ohm cabs and replace them with two 4x10 8 ohms, how much of a difference in volume would be the result? Barely noticeable?

Or are people so used to other people asking how to squeeze the last watt out of their rigs, they automatically assume that it's always the case?

The way I read it, OP asks about replacing the 4Ohm cabs with 8Ohm ones. Or perhaps I misunderstood the question.

OP, if the sensitivities and other parameters are close to eachother, You won't notice anything volumewise after the cab swap. IME anyway.

If it's a SS amp You're using, you will most likely notice a drop in the chassis/heatsink temperature and/or reduced fan speed or less frequent fan duty cycle.

Regards
Sam

[kawika5150]

Sam, yes that was what I was aiming for, and I'm sorry if I wasn't clearer in my OP.

Btw, I'm powering the cabs off of a SVT 4 PRO. My immediate impression was that I wouldn't really notice a significant loss of volume if I make this swap, but wanted to hear the others chime in on their experience.

Thank you.

[MuzikMan]

Oops, I DID read it as an 8 ohm to 4 ohm switch because so many people ask about that direction. Well, the same rules apply except the perspective would be reversed. You won't notice a significant drop in volume.

[kawika5150]

I thought just as much. Thanks all for your input.

Orange...here I come!