Safe to mix 4ohm and 8ohm cabinet?

[Ironderby]

Well? thanks in advance.

[esa372]

That would depend on the amp.

[Firesalt]

Originally Posted by Ironderby

Well? thanks in advance.

Depends on the amp. Usually the answer is gonna be no. Most amps will only support either 8 ohms or 4 ohms. Running both in parallel will give you a 6 ohm load. Although this is between the two most amps are not designed to run at this impedance. Causes wear on the amp and will eventually cause it to fail. I've seen several manuals that recommend against mixing impedances.

[domdec314]

AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

[Ironderby]

ok thanks alot just wondering because i found a 4ohm cab i like, and i already have an 8ohm 410

[will33]

Originally Posted by Firesalt

Depends on the amp. Usually the answer is gonna be no. Most amps will only support either 8 ohms or 4 ohms. Running both in parallel will give you a 6 ohm load. Although this is between the two most amps are not designed to run at this impedance. Causes wear on the amp and will eventually cause it to fail. I've seen several manuals that recommend against mixing impedances.

It gives you 2.67, safe on a 2ohm capable ss amp or tube amp, otherwise no.

[Firesalt]

Originally Posted by will33

It gives you 2.67, safe on a 2ohm capable ss amp or tube amp, otherwise no.

Well there ya go...

[Bass_Pounder]

Originally Posted by Firesalt

Depends on the amp. Usually the answer is gonna be no. Most amps will only support either 8 ohms or 4 ohms. Running both in parallel will give you a 6 ohm load. Although this is between the two most amps are not designed to run at this impedance. Causes wear on the amp and will eventually cause it to fail. I've seen several manuals that recommend against mixing impedances.

Incorrect - in parallel the mixture of a 4 ohm cab and an 8 ohm cab will be 2.67 ohms. If connected in series, it would be a 12 ohm load.

As long as the amp is capable of handling a 2 ohm load (either tube or SS), you will be fine.

Originally Posted by will33

It gives you 2.67, safe on a 2ohm capable ss amp or tube amp, otherwise no.

Just to add..............

The 4 ohm cab will recieve 2/3 of the power, while the 8 ohm cab will only recieve 1/3 of the total power.

So, even though the answer to the OP is yes you can do it, without knowing what the two cabs are, it cannot be concluded if it will be worth doing or not.

[RickenBoogie]

+1 to that^

[will33]

Originally Posted by Bass_Pounder

Incorrect - in parallel the mixture of a 4 ohm cab and an 8 ohm cab will be 2.67 ohms. If connected in series, it would be a 12 ohm load.

As long as the amp is capable of handling a 2 ohm load (either tube or SS), you will be fine.




Just to add..............

The 4 ohm cab will recieve 2/3 of the power, while the 8 ohm cab will only recieve 1/3 of the total power.

So, even though the answer to the OP is yes you can do it, without knowing what the two cabs are, it cannot be concluded if it will be worth doing or not.

+1

My short answer was, one can fry your amp, the other won't but yes, more variables as to whether or not it's a good idea.

[Bassmec]

Also power balance is a big consideration, how many speakers are there and what are their individual impedances sizes and are they wired in series or in parallel. Is there tweeters in the cabs, it all counts you know. bit more info gets a better answer.

[HolmeBass]

Originally Posted by Firesalt

Depends on the amp. Usually the answer is gonna be no. Most amps will only support either 8 ohms or 4 ohms. Running both in parallel will give you a 6 ohm load. Although this is between the two most amps are not designed to run at this impedance. Causes wear on the amp and will eventually cause it to fail. I've seen several manuals that recommend against mixing impedances.

NO!!!! This is wrong. Running a 4 ohm and 8 ohm cab in parallel will give a 2 and 2/3 ohm load, so if your amp won't support a 2 ohm load (ie it only goes down to 4 ohms) then don't do this.

If your amp does go down to 2 ohms you're fine doing this.

[T-Bird]

Hi.

42

Regards
Sam

[Sav'nBass]

Originally Posted by Ironderby

ok thanks alot just wondering because i found a 4ohm cab i like, and i already have an 8ohm 410

I was in a similar boat.. I suggest you try to get that 4 ohm cab in an 8 ohm version so you can pair it with your amp and your current cab.. I dont think there will be a huge be a huge difference between the sound of an 4 ohm cab and an 8 ohm cab.. it may be a little louder because it's pushing more power.. or maybe a little cleaner depending on the specs of amp & cab .. but when I went from a 4 ohm 1212L to an 8 ohm 1212L basically for the same reasons.. I wanted to match cabs and I had a 4 ohm 1212L & an 8 ohm B212 which I couldn't use together so when I found a great trade here on TB of the same cab in an 8 ohm config I jumped on it ..

I didn't notice much difference in the 1212L between the two (which doesn't mean that there wasn't one.. just that it wasn't noticeable to me.. )

[gumtownbassman]

If your going to match the 4 & 8 ohm cabs, you might as well leave the 8 ohm one unplugged and use it as a stand for the 4 ohm cab.
Atleast it will look like a cool stack.
Another 8 ohm cab would be a better option (IMO) to match with the existing one.

[HolmeBass]

Originally Posted by gumtownbassman

If your going to match the 4 & 8 ohm cabs, you might as well leave the 8 ohm one unplugged and use it as a stand for the 4 ohm cab.
Atleast it will look like a cool stack.
Another 8 ohm cab would be a better option (IMO) to match with the existing one.

This is not necessarily true. It does depend on the relative volumes of both cabinets (sensitivities) because the 4 Ohm cabinet is going to get twice the power that the 8 Ohm one gets. But if both cabinets have the same sensitivity, that's only a 3 db difference in the louder cabinet. If the 4 Ohm cab is less sensitive than the 8 Ohm one the difference in volume will be even less.

In fact I do this with an 8 Ohm Eden 210XLT (103 db @ 1w/1m) and a 4 Ohm GB212 UB (102 db @ 1w/1m) and they blend nicely, the 212 being a bit louder but the 210 still contributing quite a bit. And it is *much* louder and fuller than just the 212 by itself.

I lucked out on these two boxes sounding good together, they don't seem to suffer from phasing issues. I don't know how 'beamy' it is (the GB is pretty beamy by itself- it beams sound in a narrow dispersion pattern) but on big stages it has been working for me, and sound people seem to like it as well- only compliments so far, for two years running.

[JTE]

First, read through and learn about parallel impedance calculations. It's simple math, very simple..

I^T=(I¹*I²)/(I¹+I²)

So for a mismatched 8Ω and 4Ω cabinet, the math becomes...
(8*4)/(8+4) = 32/12 = 2.67Ω.

Then read about YOUR amp. Is it rated to work into a 2Ω load? If so then you won't hurt anything running the rig that way. However, as pointed out above, it may or may not (and most likely not) work well and give you better sound.

Specifics- what exact amp, what cabinets, etc.

John

[seanm]

Originally Posted by gumtownbassman

If your going to match the 4 & 8 ohm cabs, you might as well leave the 8 ohm one unplugged and use it as a stand for the 4 ohm cab.
Atleast it will look like a cool stack.
Another 8 ohm cab would be a better option (IMO) to match with the existing one.

I hope this is a joke But don't do this. The unplugged speaker will actually act like a parasite and suck power out of the plugged in speaker.

[will33]

Originally Posted by seanm

I hope this is a joke But don't do this. The unplugged speaker will actually act like a parasite and suck power out of the plugged in speaker.

I hope that's a jole.

[gumtownbassman]

Being more cynical about it really,
but the second paragraph is serious, I reckon a cab matched with the same as the first cab would do, and chances are most likely (without having specific details but i'll take a stab in the dark) that the amp will work only down to 4 ohm.