Impedance question...sorry...

[blastjv]

If I wanted to build a 3x15 cabinet and have the resulting cabinet be either 2 or 4 ohms to match my SVT head, is it viable to run two 8ohm speakers and one 4ohm speaker all in parallel? What would be the drawback of doing so? Would the 4ohm speaker see more power than the either of the 8ohm speakers? Would that really be an issue with a 300 watt amp and three 400 watt speakers? I am thinking of using three Faital Pro 15PR400 speakers.

Also, what about using three 8ohm speakers in parallel for a 2.67ohm load with my SVT (which I believe I would need to set at 4ohms, not 2 as I previously suspected?) Cause for concern?

Thanks,

-John

 

[mjmeche]

The 4 ohm with the 2 -8 oh ms would give you 2 ohms , but I wonder the 4 would be louder. I would not select the 4 ohm setting for the 3-8ohms that would cause a problem since the impedance would be 2.6667 ohms

 

[blastjv]

This is an all tube SVT-II.

 

[seanm]

The 4 ohm speaker will get 1/2 the power and the two 8 ohm speakers will each get 1/4 the power.

 

[BassmanPaul]

It simply is not a good idea to do what you suggest. Manufacturers can end up with any impedance that they want 'cos they buy the quantities needed to do this.

 

[jlepre]

Nope not a good idea

 

[RickenBoogie]

+1 bad plan. You want the spkrs to get equal power, and be balanced. No way to do that with 3 spkrs. Just do a 4 ohm 2x15. You could run a pair of them, (4x15) if you wanted to.

 

[OkieDownLow]

IIRC that head is stable to 2 ohms. (Regular SVT II, not a II Pro, correct?) Three 8-ohm speakers in parallel is 2.67 Ohms. Not a nice round number but safe for your amp. With 16 Ohm drivers it comes out to 5.33.

 

[Groovy_Gravy]

just make a 4x15 and call it a day

 

[tjh]

... not to mention a 2x15 is going to be a lot more manageable to handle/transport/etc than a 3x15 ... and if you have TWO 2x15's, you are now modular ...

 

[walterw]

Three 8-ohm speakers in parallel is 2.67 Ohms.

set your SVT to 2Ω and it should be OK i think.

maybe not perfect, but better than some series/parallel rig-up that ends up with half the amp power all going to one speaker.

 

[OkieDownLow]

set your SVT to 2Ω and it should be OK i think.

maybe not perfect, but better than some series/parallel rig-up that ends up with half the amp power all going to one speaker.

Exactly.

You just have to decide how much you care about squeezing every last watt out of your rig vs. having the cabinet configuration you want. I doubt you'd be able to tell the difference in loudness between 2 and 2.67 ohms. But the main thing is you won't frag your amp as long as it is stable to 2 Ohms..

 

[Oobly]

You could use the three 8 ohm drivers in parallel to get 2.67 ohm and run the amp on the 4 ohm setting. In general, tubes prefer lower loading than the tap rating.

You may find the tone changes slightly, but it shouldn't harm the amp or cabinets.