Question: Ohm sweet ohms

Knox in Box

Knox in Box

Rustbelt refugee.
So I have an incoming for my birthday and a question.

The amp I ordered is a 2x10 Fender Vaporizer that has an 8ohm output and 2 16ohm speakers in parallel.

My stupid question is, if it turns out to be somewhat loud at light breakup for my tastes, will I be able to just disconnect one speaker and have it more manageable?

I know the 16ohm load won't cause a problem or damage the amp, I just need to know if my reasoning is correct that it will be quieter. Or will it just lose body?
 
No!!!

Speakers are designed to move air. Removing one speaker will do several things: 1) mismatch the impedance of the output section causing the volume to be lower but makes the amp work harder. 2) If the amp was Solid State, the amp would blow.

The amp is only 12 watts so it really won't be that loud unless you are playing only at home.
 
Modern Saint said:
No!!!

Speakers are designed to move air. Removing one speaker will do several things: 1) mismatch the impedance of the output section causing the volume to be lower but makes the amp work harder. 2) If the amp was Solid State, the amp would blow.

The amp is only 12 watts so it really won't be that loud unless you are playing only at home.
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Tube amp: One step lower "16 ohms to 8 ohms or 8 ohms to 4 ohms", you will probably get away with it.

SS amp: One step up "4 ohms to 8 ohms or 8 ohms to 16 ohms", you will probably get away with it.

That's what I understand anyways. Been wrong before... So, my thinking what he wants to do would be OK if it was SS, big no no for a tube amp.
 
Bob411 said:
Tube amp: One step lower "16 ohms to 8 ohms or 8 ohms to 4 ohms", you will probably get away with it.

SS amp: One step up "4 ohms to 8 ohms or 8 ohms to 16 ohms", you will probably get away with it.

That's what I understand anyways. Been wrong before... So, my thinking what he wants to do would be OK if it was SS, big no no for a tube amp.
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Tube amp yes because the Output transformers will take the load. Typically solid state amps do not have Output transformers. Reducing the speaker impedance will increase the current through the Power transistors possibly blowing the transistors or making them run way to hot. Running to hot will cause thermal runaway causing the transistor short and blow.
 
Modern Saint said:
Tube amp yes because the Output transformers will take the load. Typically solid state amps do not have Output transformers. Reducing the speaker impedance will increase the current through the Power transistors possibly blowing the transistors or making them run way to hot. Running to hot will cause thermal runaway causing the transistor short and blow.
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OK. What about increasing the impedance in SS?

Back to lowering impedance, with SS, what about something like this:
http://www.musiciansfriend.com/amplifiers-effects/fender-rumble-500-2x10-500w-bass-combo-amp

The combo by it's self is 350 watts "8 ohms", only 500 if you add an extension speaker "bringing it to 4 ohms". Is it different because it's class D?
 
Most modern tube amps are robust enough to take a 2x mismatch either higher or lower (it will go through tubes faster though). With SS amps the impedance is a minimum, mismatching higher is fine (lower can quickly cook the transistors)
 
Bob411 said:
OK. What about increasing the impedance in SS?

Back to lowering impedance, with SS, what about something like this:
http://www.musiciansfriend.com/amplifiers-effects/fender-rumble-500-2x10-500w-bass-combo-amp

The combo by it's self is 350 watts "8 ohms", only 500 if you add an extension speaker "bringing it to 4 ohms". Is it different because it's class D?
Click to expand...

Class D only applies to the operational characteristics of the Transistors (typically Mosfets). The class applies to the on/off time of the transistor improving low distortion characteristics.

Rumble 500 Head only

upload_2018-1-30_9-35-25.png


Rumble Combo

upload_2018-1-30_9-36-35.png


https://www.fmicassets.com/Damroot/Original/10002/237030_bamp_manual_all_revA.pdf

Page 8=9
 
Relative to the OP...

Tubes are reactive. They don't behave linearly like a solid-state components. The output wattage will probably only drop a couple of watts at RMS because of the higher reflected impedance (depending on the output transformer ratio...heck...it could even rise). The big difference in volume will be from the loss of the coupling effect of two speakers. But if you are expecting to halve output...don't count on it. The detrimental effects of a mismatch (flyback voltage) would insignificant in this application.

For academic purposes, solid-state amps behave (relatively) linearly. If you double the speaker load, you will halve the output wattage. You can increase the speaker load as much as you want to dampen the output. But as others here have noted SS amps have a MINIMAL speaker impedance, because the opposite is true and if you go below the minimum, voltages will exceed the parts specs and things will fry.
 
Thanks guys, I'll just wait until it shows up and see if it is too loud for my apartment at slight breakup.

If so I'll either look into an attentuator of some sort of just return it and get a Katana 50 at the same price.
 
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