Stereo amp with different impedances

[gblier]

I have a recently purchased 4X10 cab at 4Ohms, and although it sounds good by itself I can't help but think about adding a single 15" SWR (8ohm) which I own under it. Is it ok to Y-split the inputs to my Stewart World 1.2 Stereo Power amp and run one side at 4 and the other side at 8 ohms? There are gain controls, so I should be able to balance the cabinet levels.

[bassmanbiff]

yes

[Hactar]

Yes, 'twill be fine.

[randysmojo]

and you can adjust the seporate gains to maximize tone! If it sounds better with one a little higher than the other etc.....

[BassmanPaul]

Originally Posted by Hactar

Yes, 'twill be fine.

no you won't. No commercial 1x15 has a chance of keeping up with a 4x10. The 1x15 WILL fail!

[alec]

Originally Posted by BassmanPaul

no you won't. No commercial 1x15 has a chance of keeping up with a 4x10. The 1x15 WILL fail!

Only if it's driven too hard, surely.

[sad_katz]

Originally Posted by BassmanPaul

no you won't. No commercial 1x15 has a chance of keeping up with a 4x10. The 1x15 WILL fail!

As long as each cab get their own gain/volume and the 410 is adjusted accordingly, the 115 might have a chance of surviving.

Will it sound good? No one can say ...

PS: get another of the same 410, especially if you (OP) like the tone of one and need more volume. Combining different cabs is more of a gamble than anything.

[Hactar]

Originally Posted by BassmanPaul

no you won't. No commercial 1x15 has a chance of keeping up with a 4x10. The 1x15 WILL fail!

I was not taking into account whether the OP's rig will sound excellent, rather, I was simply informing him that from a purely technical standpoint, his power amp will be perfectly happy with mismatched loads.

I do agree that acquiring another 4x10 is vastly preferable, however, I think that saying "no commercial 15 can keep up with a 4x10" is at best a generalization. Certainly true in some cases though.

[will33]

It won't hurt the poweramp any. You can control the individual cab volumes separately so you don't destroy your 15. That also means the 15 will be adding very little to your overall output, really not even enough to bother with it other than to serve as a stand for your 410, putting it up at ear level where it will sound louder.

[BassmanPaul]

Originally Posted by alec

Only if it's driven too hard, surely.

Let's look from an electrical POV. The thermal power rating of a 1x15 would be maybe 2-300W. That's excursion limited to about half of that. A typical 4x10 will handle about twice what a 1x15 can. you use the level controls on the amp to balance the cabinets. The 1x15 is now trying to be as loud as the 4x10 which it cannot do. It will fail. Simplistic terms I know but I hope you get the point.

[alec]

Fair enough, if you were trying to make the 8Ω 15" as loud as the 4Ω quad, but I wouldn't do that. Just take what it can give you.

[lbwdog]

Put the 4x10 on bottom and the 1x15 on top.

[randysmojo]

I actually used to put my 115 on top of a 410 with crazy good results.

[babebambi]

Originally Posted by alec

Fair enough, if you were trying to make the 8? 15" as loud as the 4? quad, but I wouldn't do that. Just take what it can give you.

Yup, I never understand the mentality to have one cab "keeping up" with another cab ...

[RickenBoogie]

Originally Posted by babebambi

Yup, I never understand the mentality to have one cab "keeping up" with another cab ...

Well, that's simple. If one cab cannot "keep up" with the other, what would be the point of using it? If cab A is cruizing along loudly, and cab B is lost beneath the sound, what benefit are you getting from it?

[randysmojo]

I havrn't tried so I'm just saying in my hypothetical, theoretic mind, if cabinet A is running 250 watts and cabinet B is running 100 watts although B wouldn't be by any means as loud as cabinet A wouldn't it still be somewhat audible and add some color to the tone, therefore making a contribution to the overall sound and volume even if not as much as cabinet A?

[JHAz]

Originally Posted by randysmojo

I havrn't tried so I'm just saying in my hypothetical, theoretic mind, if cabinet A is running 250 watts and cabinet B is running 100 watts although B wouldn't be by any means as loud as cabinet A wouldn't it still be somewhat audible and add some color to the tone, therefore making a contribution to the overall sound and volume even if not as much as cabinet A?

A little at least. But you can't do it just off of power. In your example cab B is getting something like four dB less signal. Now, what do the speakers do with the electrical signal? If B is a 115 and A is a 410, it's at least possible that A, with about twice the radiating area, is 3 dB more sensitive than B, which would make A, in total, about 7 dB louder than B. About one notch below twice as loud. How they add, I'm too lazy to look up an SPL addition tool right now . . . .

[RickenBoogie]

Originally Posted by randysmojo

I havrn't tried so I'm just saying in my hypothetical, theoretic mind, if cabinet A is running 250 watts and cabinet B is running 100 watts although B wouldn't be by any means as loud as cabinet A wouldn't it still be somewhat audible and add some color to the tone, therefore making a contribution to the overall sound and volume even if not as much as cabinet A?

In your example, the 2 cabs do not see different wattage. If the amp is putting out 500 watts, (max), then each cab gets 250 ea. It's what they DO with that wattage that counts.

[randysmojo]

In my example they do get different wattage because it's my hypothetical world!!!

[grendle]

Originally Posted by randysmojo

and you can adjust the seporate gains to maximize tone! If it sounds better with one a little higher than the other etc.....

I do this currently with a peavey 4x10 and a Hartke115.