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Watts verses ohms

0

082752

Jan 1, 2009
28
0
#1
Which one is closer to the truth
Using 200 watts at 4 ohms
Scenario "A" or Scenario "B"
***************
Scenario "A"
200@4 ohms would be 100@8ohms and 50@16
***************
But I have read here instead of cutting it in half you get 2/3 power on the next higher ohms.
***************
Scenario "B"
200@4 ohms---133@8ohms---90@16ohms
***************
 
#3
I'll try to answer this as I understand it.

A tube amp will give the same maximum power into all of the impedance taps. This is what the output transformer does for you.

While a SS amp will give you less power into a higher load the actual ratio depends on the amplifier topography. If the amp supplies 50W into 16Ω it will try to supply 100W into 8Ω, 200W into 4Ω and 400W into 2Ω. How close it gets to these theoretical figures depends on both the output stage and the ability of the power supply to provide the needed voltage and current draw.

Paul
 
#5
It's ruled by Ohms Law. Volts times amps equals watts. Do the math and you can figure it any way if you have two of the variables. Tube amps drive the same power into a load because of their output transformer. What it is designed to do is give your power tubes a certain load at all times. This happens by matching up your speakers to the proper tap on the other side of the output transformer. This is why it is important to match speakers and taps on a tube amp, because if you go too far from the desired impedance, you can cause problems for your tubes.
 
#8
082752 said:
Which one is closer to the truth
Using 200 watts at 4 ohms
Scenario "A" or Scenario "B"
***************
Scenario "A"
200@4 ohms would be 100@8ohms and 50@16
***************
But I have read here instead of cutting it in half you get 2/3 power on the next higher ohms.
***************
Scenario "B"
200@4 ohms---133@8ohms---90@16ohms
***************
Click to expand...
None of the above. At low power levels pure Ohms law applies, but at full power levels amplifier power supplies can't meet the demand that Georg places on them. Real world at full power halving the impedance will only get about a 70% increase in power.
 
#9
I have a Peavey Mark IV 300watt@2 ohms>>210@4 ohms
What I'm trying to find out is if I will hear any noticable difference in volume if I change out my 15" 16 ohm speaker to a 15" 4 ohm speaker.
I don't have a clue how much power is getting to the 16ohm.
 
#10
082752 said:
I have a Peavey Mark IV 300watt@2 ohms>>210@4 ohms
What I'm trying to find out is if I will hear any noticable difference in volume if I change out my 15" 16 ohm speaker to a 15" 4 ohm speaker.
I don't have a clue how much power is getting to the 16ohm.
Click to expand...

I'd imagine the difference would be audible. Instead of your volume being on "5" on the amp, you might get the same level spl's at "4". Just for example - not actual numbers.

Then again, it depends on cabinet design, speaker efficiency, etc etc...
 
#11
I took the back off of the cabinet and what's in there is a 8 ohm speaker. I just ordered a Eminence Basslite C2515 15" 4 ohm Bass Speaker: Link Removed
Will 210 watts and this speaker knock the pictures off of the wall and rattle the windows or am I going to need two speakers for 2 ohms for 300 watts to do it.
I realize if I wanted to start a house demolition company I will need power.
 
#14
you won't hear much of a difference. but i had that head back in the day and it is hella loud into a couple of fifteens. I don't know what the impedance of the 2x15 pv cab was that i used it with but it was LOUD.
 
#15
Ok that's kinda what I wanted to hear. I don't have any problems with building a new cabinet, maybe I'm looking for an excuse to do just that. So what do you think about building a cabinet for 2>8 inch and one 15 inch:
Link Removed
Link Removed
2-8 ohm 8" and 1-15" 4 ohm wouldn't that equal 2 ohms
 
#16
082752 said:
Ok that's kinda what I wanted to hear. I don't have any problems with building a new cabinet, maybe I'm looking for an excuse to do just that. So what do you think about building a cabinet for 2>8 inch and one 15 inch:
Link Removed
Link Removed
2-8 ohm 8" and 1-15" 4 ohm wouldn't that equal 2 ohms
Click to expand...

Only if the cab was designed to be run full range.

Doing that though will kill the 8's real quick.

Building a cab like that with a passive crossover in it will still only be 4 ohms.
 

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