stacking cabs with different impedance? HELP

[hcstdbass]

Up until now i've run a behringer BX4500h head through my ampeg SVT 4x10hlf cab. i wanted to add a crisper bottom end since i play in drop C tuning (the 10's are great but get a little muddy when you're playing that low) and figured i could do so by adding a 15' speaker to my stack. Recently i got a good deal on a used ampeg SVT 1x15 cab at my local guitar center, so i picked it up. when i got back to my practice space i noticed that the 4x10 has a 4 ohm impedence, and the 1x15 has an 8 ohm impedence.

my question is, will this be a problem, and are their any draw backs to running two cabs with different impedances? i just don't want to blow my amp or any of the speakers. when i hooked it all up it sounded nice enough. the 15' driver really cleared up my bottom end.

any help i could get would be greatly appreciated. i apologize if this topic has already been covered in another thread. i searched, but couldn't find anything on my specific problem.

oh, and be nice? i'm new.

 

[enim]

The problem isnt the differing impedences, but the overall impedance.

Your amplifier is safely rated to drive a 4 ohm load. That would be 2 8-ohm loads, an 8 and 2 16's, etc. What you have is a 4 and an 8, which equals 2.67 i believe ( 1/(1/8+1/4)).

Your amplifier isnt rated to handle that low of an impedance, which could cause it to heat up excessivly, shut down non-violently, or something worse that I don't know of.

Moral of the story: I wouldn't do that to the amplifier.

 

[billfitzmaurice]

There are many differences between cabinet sensitivities and response, so a simple answer to this question doesn't exist. The only sure way to know how the two cabs will work together is to try them. But by and large you wouldn't want one fifteen getting the same amount of power as four tens, so this probably will work out.

 

[agreatheight]

Yes, you would be running a total imepdance of 2.67 ohms with both cabs and unless your head goes down to 2 ohms it's NOT GOOD.

EDIT: The BX4500h has a minimum load of 4 ohms so this is a BAD SETUP!

Here's a useful link for figuring out impedance and such:
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Good luck!

 

[hcstdbass]

I really appreciate the help guys. i have an ampeg SVT 4x10he as well that's sittin around in my drummer's basement. it has an 8 ohm impedance, so i guess i'll have to stack that and the 1x15 instead of the 4x10hlf . Atleast until i get a new head for christmas that can handle a 2 ohm load.

ANY RECCOMENDATIONS ON JUST SUCH A HEAD?

thanks again guys.

 

[JustOpenYourMind]

With mismatched cabs like these, the 4 ohm cab will get twice the power that the 8 ohm cab gets and will be louder.

So even if your head runs safely at 2 ohms. the output of the two cabs will be uneven.

So just use the 410he and 15 together when you need more volume and use the hlf as a single cab. it'll sound better this way.

 

[agreatheight]

With mismatched cabs like these, the 4 ohm cab will get twice the power that the 8 ohm cab gets and will be louder.

So even if your head runs safely at 2 ohms. the output of the two cabs will be uneven,

Which could be OK, tone-wise. It won't hurt the amp or speakers (assuming they can handle the power, aka watts). I ran a similar set up for a while, with a 4 ohm 15 and an 8 ohm 410 and liked the tonal balance. The OP may not.

 

[agreatheight]

Many SWR heads run down to 2 / 2.67 ohm.