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SVT cab/load tech question.

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danomite726

May 31, 2011
21
1
#1
So I got a amp/tech question for you awesome members of the TB Boards!

I have my two SVT classic rigs, one of them I run in 4 ohm mode because I am running it with two 8 ohm cabs, A SVT18 and a SVT 410hen anniversary cab. The svt as you all know has three outputs, one speakon cable, and two 1/4 inch outputs.


So the idea is, if I plugged in a 3rd cab, could this work if it is a 4 ohm load? Technically that would put everything at 2 ohms I think... ??

Just figured I would run this past you guys. Obviously its not necessary as I have enough power from both cabs and the head alone, but...hey, if I can...why not right?? :)
 
#2
First: I don't know how your amp is wired, but on my SVT-2 Pro the speakon terminal is wired in parallel with the two 1/4" phone jacks, and I have a slider to choose between 4 ohms and 2 ohms. Because the three ports are wired in parallel, it doesn't matter what combination of ports you use.

Second: if you put two 8-ohm cabs in parallel, the resulting load would be 4-ohms. If you put another 4-ohm cab in parallel, you would indeed end up with a two ohm load.

the problem, though, is that the power won't be shared evenly by the cabinets.
 
#5
with a 300 watt amp, and 3 paralleled cabs that are 8, 8 and 4 ohms, the result is that you have a total load of 2 ohms, and each 8 ohm cabinet gets 75 watts of output and the 4 ohm cabinet gets 150 watts of output.

The 4 ohm cab might be louder because it gets more power. That all depends on things like speaker efficiency, the number of drivers, where you put the cabs, etc. but it will work. have fun experimenting.
 
#6
Wow! this will be so awesome. Thanks so much for your help guys!

the 4, ohm cab I will be using is one of those old rare ampeg 2x15 fridge size cabs! That in combination with the 18 will make for a huge low end, and the 4x10 to top it off! I am excited like its christmas!
 
#7
danomite726 said:
Wow! this will be so awesome. Thanks so much for your help guys!

the 4, ohm cab I will be using is one of those old rare ampeg 2x15 fridge size cabs! That in combination with the 18 will make for a huge low end, and the 4x10 to top it off! I am excited like its christmas!
Click to expand...

FWIW I find that most commercial 410's have more usable low end than their 15" based counterparts.
 
#8
danomite726 said:
Wow! this will be so awesome. Thanks so much for your help guys!

the 4, ohm cab I will be using is one of those old rare ampeg 2x15 fridge size cabs! That in combination with the 18 will make for a huge low end, and the 4x10 to top it off! I am excited like its christmas!
Click to expand...

As always.............just because you CAN do something, does not mean that you SHOULD do it.

Mixed driver sizes, power distribution problems, etc, etc., etc.........:rollno:
 
#10
Gentlemen, my apologies for not responding back to this sooner, and I want to first off take the time for all of you who took the time to reply.

To clear up, I hope you all understand that I am certainly not trying to have extra speakers/cabs for the sake of it. The room I will be using it for practice in is a large open room and at times can be a little on the bright or "dead" side of sound, and I was in the thought that perhaps adding this cabinet could help fill it up a bit and If I didn't have to run a second head, even better.

So, if this is a safe thing to do/try please let me know, I really really do appreciate any input anyone has.
 
#11
The unfortunate thing to remember is there is a point of diminishing returns in a room. You hit the point where it is all noise (mud) and then severe cancellation starts with more speakers or power. You might be miles ahead to explore better placement of the cabs and treatment of the room acoustics.
 
#12
Heed the B! Heed the B!

(Uh...... in other words..... try what B String said first. It would be a lot less complicated to try moving your cab around a couple of times to find a sweet spot than it would to try and make a speaker garage sale come together from a physics standpoint.)
 

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