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[Debbie Dunkley]

I was wondering if someone could help me out with this question....
When i check out the specs on my amp for running at 8ohm bridge, it has 2 listed sets of figures. first is 1300 watts @ 8 ohms, 20 hz- 20 khz, 0.1% THD and the second shows 1500 watts @ 8 ohms, 1 khz, 0.1% THD. How do I know which rating is correct for my application - 1300w or 1500 watts???

Thank you in advance............

[Scott Harris]

What is the amp & model?  I wouldn't trust the spec too much unless I knew the brand name.  Many ratings are stretched to meet marketing goals.  (I will take a guess at this being a qsc rmx2450 in which case the rating is believable.)

The difference between the 2 ratings you have listed are related to the bandwidth.  It is telling you that it has 1,300 watts across the full audible spectrum while it can reach 1,500 watts at 1,000 Hz which is a marketing number.  (If you are using this to power a sub you care about the 10-10Khz rating and the 1khz number is useless as you want the power output from 20-200Hz or where ever you plan to use it.)  The good thing about what your spec is the 0.1% THD portion which means it is measured at no audible distortion.  The difference from 1,300 watts to 1,500 watts is irrelevant in the real world.

[John Roberts {JR}]

I was wondering if someone could help me out with this question....
When i check out the specs on my amp for running at 8ohm bridge, it has 2 listed sets of figures. first is 1300 watts @ 8 ohms, 20 hz- 20 khz, 0.1% THD and the second shows 1500 watts @ 8 ohms, 1 khz, 0.1% THD. How do I know which rating is correct for my application - 1300w or 1500 watts???

Thank you in advance............

Are you operating the amp at 1kHz only or 20-20kHz... ?

This is a common question that has been answered many time before, with more detail.

JR

[Debbie Dunkley]

What is the amp & model?  I wouldn't trust the spec too much unless I knew the brand name.  Many ratings are stretched to meet marketing goals.  (I will take a guess at this being a qsc rmx2450 in which case the rating is believable.)

The difference between the 2 ratings you have listed are related to the bandwidth.  It is telling you that it has 1,300 watts across the full audible spectrum while it can reach 1,500 watts at 1,000 Hz which is a marketing number.  (If you are using this to power a sub you care about the 10-10Khz rating and the 1khz number is useless as you want the power output from 20-200Hz or where ever you plan to use it.)  The good thing about what your spec is the 0.1% THD portion which means it is measured at no audible distortion.  The difference from 1,300 watts to 1,500 watts is irrelevant in the real world.

Thank you for the response Scott.......this is more of a question for me to learn something. The amp in question is an older Behringer EP2500 that I got used cheap. I know Behringer is well known to inflate their numbers. It is my back up amp - all the amps in my rack are Crowns. It was simply something I had come across before but did not know the difference and it seemed a good time to ask. If I use it, it will be for stage monitors OR if one of my Crowns goes down and I will drop in the Behringer to use bridged at 8 ohms.

[Debbie Dunkley]

Are you operating the amp at 1kHz only or 20-20kHz... ?

This is a common question that has been answered many time before, with more detail.

JR

Hi John...this is just a back-up amp which will only get used if one of my other amps goes down so it could be for sub, mid or horn use.

[David Parker]

I was wondering if someone could help me out with this question....
When i check out the specs on my amp for running at 8ohm bridge, it has 2 listed sets of figures. first is 1300 watts @ 8 ohms, 20 hz- 20 khz, 0.1% THD and the second shows 1500 watts @ 8 ohms, 1 khz, 0.1% THD. How do I know which rating is correct for my application - 1300w or 1500 watts???

Thank you in advance............

here's the big deal. compare apples to apples. If you are comparing two amps, make sure the specs are the same. If the specs are not identified, they are useless, especially some cheap amps that give "peak" power. Another thing, you have to double the watts to get 3db increase in volume, which is generally considered to be the least increase that matters. So if one amp is 10 or 20 percent less than another, that usually is not a meaningful difference. I'd suggest buying only amps from reputable manufacturers, such as crown, QSC, peavey, and then there are others that are a lot more expensive. Many have had good luck with behringer amps, but you have to watch their specs, they use their own ratings, and they make their amps look a lot more powerful than they are.

[Don Boomer]

How do I know which rating is correct for my application - 1300w or 1500 watts???

Not that you asked ... but even though 200W might seem like a substantial difference, the two numbers are only about .6 dB different.

[Debbie Dunkley]

Not that you asked ... but even though 200W might seem like a substantial difference, the two numbers are only about .6 dB different.

Hi Don...yes it's really not the extra power that I am interested in as much as the difference between the 2 stated ratings but thanks for reminding me that the 200w difference would be inaudible in real terms....

[Tim Perry]

The1 kHz spec is easiest for a service tech to use in testing. you can simply calculate the peak-to-peak expected voltage, operate channel into a nonreactive known load measure with an oscilloscope (and maybe a distortion meter)

As most music does not consist of continuous single frequency sine waves, the marketing department insists on a variety of confusing and sometimes fraudulent ratings.

As amplifiers have grown so large these days, obtaining a non-reactive load has become a non trivial matter. (think if you had to service equipment all day in the summer with a several thousand watt space heater nearby with a loud cooling blower running)

[John Roberts {JR}]

Hi John...this is just a back-up amp which will only get used if one of my other amps goes down so it could be for sub, mid or horn use.

As Boomer pointed out that is less than 1dB difference between those two power levels so no big yup.

To give you more information than you need, amplifiers require much larger capacitors in the power supply to make the same power at 20 Hz as 1 kHz, because they are only getting topped off at 2x the mains frequency rate. 

Audio signals that are higher frequency than the rate that the PS caps are getting topped off, pull roughly half power from each the + and - rail, because they are AC signal. Very low frequency audio, stays high or low for multiple recharging cycles, so draw 2x the current of the HF signal while mostly high or mostly low.

This only makes a very small difference at very low frequency. There are much more important things to worry about. Amps are pretty mature technology and well sorted.

JR

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