Rockford R300x4 Wattage

[Stephen B]

I just finished installing a stereo for my son and with him being 17yrs old, I decided on all Rockford Prime amps for his first stereo. The amps are actually not bad, I have 2 R300X4 bridged for the front and Rear DD-Audio 6.5 components, and a R500X1D for his Sundown 12. Here is my question when setting the gains the R500 was with Oscope and then checked with DMM to see the watts, it came out to around 36volts which translated 648 watts at 2ohms. Here is where it got interesting to me. When we set the gains bridged on the 2 R300X4 the voltage after we set the clean signal with the oscope was 35volts for each bridged channel that's 300watts for each channel bridged. This amp is supposed to only put out 150x2 bridged, how is it putting out 300 X 2 bridged, am I missing something? I have attached a couple of pictures. This is just baffling me...

 

 

 

[biscuitownz]

How are you translating volts to watts? Without power factor you won't get an accurate watts measurement

[Stephen B]

I have been using the calculator here. http://www.rapidtables.com/calc/electric/ohms-law-calculator.htm

It's been adding up for me, correct me if I am wrong though... I might be wrong, I need to get the amps and the voltage. I'll do it again later.

[WalledSonic]

34 minutes ago, biscuitownz said:

How are you translating volts to watts? Without power factor you won't get an accurate watts measurement

I dont believe thats true. The speaker will draw a real load based on impedance. The amp will have to create and dissipate more power based on the power factor of the load. Please correct me if im wrong

[Stephen B]

I looked it up, I need the amps in the equation with the voltage. I was using volts and ohms. I'll correct my post as soon as I get a chance to use and amp clamp with it. I have a feeling that the amps X the voltage is going to probably closer to the 150X2 RMS.

[biscuitownz]

1 hour ago, Stephen B said:

I looked it up, I need the amps in the equation with the voltage. I was using volts and ohms. I'll correct my post as soon as I get a chance to use and amp clamp with it. I have a feeling that the amps X the voltage is going to probably closer to the 150X2 RMS.

Using a clamp meter and multimeter still won't give you power factor which is what you need for AC. Your method will give you apparent power (VA). Take a look at the SMD AMM-1 which factors in the power factor when it is measuring real time wattage. In DC you can do volts*amps to get wattage, with AC it is volts*amps*pf

1 hour ago, WalledSonic said:

I dont believe thats true. The speaker will draw a real load based on impedance. The amp will have to create and dissipate more power based on the power factor of the load. Please correct me if im wrong

A speaker is a reactive load vs. a resistive one. The impedance of it will change with frequency, which can also be seen with the SMD IM-SG. Unless your amp has technology like Rockford's constant power where it's suppose to do the same power at 1 and 2 ohm loads, you will get less output as the impedance goes up. 

[WalledSonic]

Or if you know your impedance at a frequency, then V^2/R is the same thing.  

[MrSkippyJ]

1 hour ago, WalledSonic said:

Or if you know your impedance at a frequency, then V^2/R is the same thing.  

Tony D'amore disagrees with you.

[bolanorthhighlands]

I have a r300x4. It says 2 ohms in the specs. But I think U can run it at 1 ohm. Following 

[WalledSonic]

On 8/8/2017 at 6:28 PM, biscuitownz said:

Using a clamp meter and multimeter still won't give you power factor which is what you need for AC. Your method will give you apparent power (VA). Take a look at the SMD AMM-1 which factors in the power factor when it is measuring real time wattage. In DC you can do volts*amps to get wattage, with AC it is volts*amps*pf

A speaker is a reactive load vs. a resistive one. The impedance of it will change with frequency, which can also be seen with the SMD IM-SG. Unless your amp has technology like Rockford's constant power where it's suppose to do the same power at 1 and 2 ohm loads, you will get less output as the impedance goes up. 

 

On 8/8/2017 at 8:26 PM, MrSkippyJ said:

Tony D'amore disagrees with you.

After some more reading on power factor, I get it now.  Sorry for convoluting the thread with misinformation.

So when people clamp the amplifier power in competitions (and for hobby), this value is really VA?  My interpretation is that certain SPL classes require the amplifier's apparent power to be in a bracketed class, but if you optimize your power factor (thus the real power being output by the subs), then thats the real key to being successful in competition.  A competitor would need to optimize box/port resonance, cabin resonance, impedance, AND power factor to have a real edge.

From what I found on MECA and Digital Designs websites, the use of the term "true power" seems to refer to "apparent power".  I believe this is a misnomer, or, perhaps I am wrong again.  There is no power factor being taken.  Can one of you gents clarify please?  I think this will also help @Stephen B get the measurement he's looking for. Thanks.

http://ddaudio.com/faq/clamp-testing/

http://www.mecacaraudio.com/2017SPLRuleBook.pdf (page 8, number 3)