Yet another impedance question

[banjo5]

I had an SVT 4 pro years ago. Sold it and regretted it ever since. So, I just got another one. I have several 8 ohm cabs that I can run but I’m trying to figure out the best configuration. If I run the cabs in parallel (in one, out of that one into the other) and run that from one side, it will be 4 ohms from one side at 625 watts. That will split the power evenly between the cabs and give me about 300 watts per cab. The other option is to run one cab per side. So, 8 ohms per side at 350 watts per cab. This seems like a better option since 8 ohms per side should be less load per channel and it should run cooler, right? Or, it it better to run one channel at 4 ohms to drive the power amp a little harder? Or, am I just way over thinking this?

 

[Wasnex]

The logic you using makes sense, but I believe you got some of the specs wrong.

Ampeg's web pages says:
RMS Power Output: 300-Watts x 2/900 (mono-bridged @ 8 Ohms)
RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms)
RMS Power Output (2 Ohms): 600-Watts x 2


Running the amp at 8 ohms is less of a load than running the amp at 4 ohms. But in dual mono, each channel is rated for 2 ohms, so I would not be overly concerned about running one of the outputs at 4 ohms.

If you run both cabs in parallel off one side of the amp, you 490W RMS; which is 245W per cab.

If you run each cab off one side of the amp, each cab gets 300W.

The decibel differenced between 245 and 300 watts is about 0.88dB. You should not hear any difference in volume. The feel may be slightly different as I believe impedance will have some impact on damping.

A final option is to bridge the amp to get 1200W at 4 ohms (two 8 ohm cabs). Then each cab will get 600W. This taxes the amp the same as running dual mono at 2 ohms.

 

[banjo5]

The logic you using makes sense, but I believe you got some of the specs wrong.

Ampeg's web pages says:
RMS Power Output: 300-Watts x 2/900 (mono-bridged @ 8 Ohms)
RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms)
RMS Power Output (2 Ohms): 600-Watts x 2


Running the amp at 8 ohms is less of a load than running the amp at 4 ohms. But in dual mono, each channel is rated for 2 ohms, so I would not be overly concerned about running one of the outputs at 4 ohms.

If you run both cabs in parallel off one side of the amp, you 490W RMS; which is 245W per cab.

If you run each cab off one side of the amp, each cab gets 300W.

The decibel differenced between 245 and 300 watts is about 0.88dB. You should not hear any difference in volume. The feel may be slightly different as I believe impedance will have some impact on damping.

A final option is to bridge the amp to get 1200W at 4 ohms (two 8 ohm cabs). Then each cab will get 600W. This taxes the amp the same as running dual mono at 2 ohms.

Hmmm, this is what I got from the manual, from their website. Seems like they may have a print validation issue. Never the less, I think we’re saying the same thing. Either situation/configuration seems like it will provide the same(ish) volume but one may be slightly easier in the amp.

 

[Wasnex]

Hmmm, this is what I got from the manual, from their website. Seems like they may have a print validation issue. Never the less, I think we’re saying the same thing. Either situation/configuration seems like it will provide the same(ish) volume but one may be slightly easier in the amp.

Yes we are saying pretty much the same thing.

The specs from manual provide two figures RMS and Continuous. The website says RMS but I believe they equal the Continuous specs from the manual. No idea what Ampeg means with the distinction between RMS and Continuous.

Pretty sure running the amp in bridge mono would give you some extra SPL, providing your cabs have sufficiently high power handling.

 

[banjo5]

Yeah that’s the part I should have mentioned. My cabinets of choice today are a Goliath III AND A Goliath Jr. The Jr is only rated at 350. Probably wouldn’t hurt either to run in bridged mono, but I’d have to be careful about the throttle pedal.