FTC ratings were also aimed towards home audio and, Crown is not obligated to use them because they left the home audio market 30+ years ago.
What matters is performance. And Crown has always been notorious for their low-end performance for decades.
Now if you still want to know the answer, you'll need to deduct the 1 KHz wattage at the given impedance by 10-20% to achieve the FTC rating of 20 - 20,000 KHz. Then, deduct the FTC frequency response to your sub frequencies (Wherever your starting and cutoff point is) at the given impedance to find the answer.
Other than gloating on having a few insignificant watts over your competitor you are not gaining anything.
If the 20hz-20khz rating is for example 1000 watts, that tells me that i will get minimum 1000watts anywhere in that range, so how do you figure it wont tell me how much my subs are getting?
You are not feeding the amplifier 20 Hz - 20 KHz. You are feeding it whatever’s your starting & cutoff point when using your crossover on your subs. So, you will be getting more wattage, which the FTC measurements won't tell you. How much more can only be answered if you bench test the amplifier at the given frequencies.
There is also impedance which fluxuates according to the cabinet design. In other words just because the sub says 8 ohm doesn't mean you will get 8 ohms at all times. Impedance rise & dips happens to every speaker, which is why there is a nominal & re of a loudspeaker.
So, unless you are going to measure everything, you will only get an approximation of the wattage you are feeding the woofer.
Exactly. Without taking in account the impedance, distortion level and, how robust the power supply is, you will only get a ruff estimate. This applies to all amplifiers. Which is why many bench test amplifiers if they must know.
As I mentioned previously, you need to take into account the load on the amp when benching an amplifier. It doesn't matter what the test tone is if you don't take the load into consideration. Download any of Crown's Macrotech Series manuals and look at their test tone comparisons between 20 Hz and 1 KHz under various impedances. You'll find the wattage difference is 1 dB at best, which is insignificant for us to hear.
I fully agree the 20 - 20Khz method needed for a full range cabinet. However, for subs it’s not important because we feed subs limited frequencies. Not to mention having enough headroom while achieving the desired SPL is more important for us doing Pro Audio. We are not concerned on exactly how much wattage each woofer is getting. Our concern is having an amplifier that can give the woofer it’s maximum output without amplifier clipping in the process.
Home Audio amplifiers were always questionable about their wattage (As with car audio). Which is why FTC standards were brought to the table. I cannot think of any Home Audio amplifier that will stand up to a pro audio amplifier in terms of abuse (2 ohms per channel @ full tilt for hours) other than the old McIntosh MC Series, and Krell. I mean let's be honest. If all home amplifiers could deliver the amount of current needed in a 2 ohm per channel load you wouldn't find many home audio users moving to wards Pro Audio amplifiers.
FTC only gives you the wattage under a full bandwidth. Nothing more. You are using a limited bandwidth so FTC measurements won't tell exactly how much wattage you are feeding your woofer. Stress comes from a low impedance loads. How the woofer interacts in the cabinet at the given frequencies will dictate the impedance load. And just for the record, a test tone is more taxing to the amplifier than music. Music is not a steady state whereas, a test tone is.
You'll need to bench test the amplifier with the frequencies you are currently feeding the amplifier at the given load to get that answer. You'll also need to take into account the impedance rise/dips of the subs as well. If you purchased good subs you can get the chart from the manufactures website. If you didn’t you’ll need to test your subs as well. FTC measurements won't help you there because you are not using the amplifier from 20 - 20 KHz. You are using limited frequency. Subs don't get 20 - 20 KHz therefore, FTC measurements will not give you the accurate answer. All it will give you is a ruff estimate.
Keep in mind what I use for subs, what you use for subs and, what the next guy use for subs varies a lot. This plays a heavy factor on how much wattage each woofer will get from any amplifier. You'll need to bench the amp to find out what you are looking for.
This is why there are amplifier shootouts, subwoofer shootouts and things of that nature.
BTW if you don't see me post for a while you can shoot me a PM on PSW.