difflvl

XTI 4000 20hz - 20khz watts?

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I was wondering what are the wattage specs for the XTI 4000 at 20hz-20khz, instead of the 1khz rating. I looked all over the website and can't find it.

Thanks

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There are two standards that make it easier to compare amplifier output ratings the FTC and EIA ratings standards.

The FTC standard was established by the Federal Trade Commission and requires that a manufacturer’s stated power ratings must meet the advertised frequency range (usually 20 Hz to 20 kHz) at the rated THD (Total Harmonic Distortion) with both channels driven.

The EIA rating, established by The Electronic Industries Association, is the power output of a single channel driven at typically 1 kHz with 1% THD clipping. The EIA standard will typically be 10 to 20% higher than the FTC ratings.

We go one step further than the EIA ratings and drive both channels as we feel the fairest, most honest, and most revealing rating method is the obvious one: to specify power with all channels fully driven, as this is a more real world scenario. When fewer channels are being tested, the more power the ones that aren’t being used can deliver. This can artificially increase the apparent power output. By testing with both channels driven we are decreasing the standard 10-20% difference of one channel driven.

What does a 10-20% power difference mean in reality? For the average person to hear a difference in loudness/level, you would need to double the power to the speakers. You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won’t hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

To put it in a nut shell we basically provide a more conservative power spec of the EIA standard because we test with both channels driven during our tests not just one.

Since the differences between the two standards are really minimal, when you look at it, the more important questions should be things like amplifier features and reliability.

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There are two standards that make it easier to compare amplifier output ratings the FTC and EIA ratings standards.

The FTC standard was established by the Federal Trade Commission and requires that a manufacturer's stated power ratings must meet the advertised frequency range (usually 20 Hz to 20 kHz) at the rated THD (Total Harmonic Distortion) with both channels driven.

The EIA rating, established by The Electronic Industries Association, is the power output of a single channel driven at typically 1 kHz with 1% THD clipping. The EIA standard will typically be 10 to 20% higher than the FTC ratings.

We go one step further than the EIA ratings and drive both channels as we feel the fairest, most honest, and most revealing rating method is the obvious one: to specify power with all channels fully driven, as this is a more real world scenario. When fewer channels are being tested, the more power the ones that aren't being used can deliver. This can artificially increase the apparent power output. By testing with both channels driven we are decreasing the standard 10-20% difference of one channel driven.

What does a 10-20% power difference mean in reality? For the average person to hear a difference in loudness/level, you would need to double the power to the speakers. You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

To put it in a nut shell we basically provide a more conservative power spec of the EIA standard because we test with both channels driven during our tests not just one.

Since the differences between the two standards are really minimal, when you look at it, the more important questions should be things like amplifier features and reliability.

Thanks for the explanation. Just out of curiosity what is the watt output of the XTI 4000 with the FTC method?

Thanks

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There are two standards that make it easier to compare amplifier output ratings the FTC and EIA ratings standards.

The FTC standard was established by the Federal Trade Commission and requires that a manufacturer's stated power ratings must meet the advertised frequency range (usually 20 Hz to 20 kHz) at the rated THD (Total Harmonic Distortion) with both channels driven.

The EIA rating, established by The Electronic Industries Association, is the power output of a single channel driven at typically 1 kHz with 1% THD clipping. The EIA standard will typically be 10 to 20% higher than the FTC ratings.

We go one step further than the EIA ratings and drive both channels as we feel the fairest, most honest, and most revealing rating method is the obvious one: to specify power with all channels fully driven, as this is a more real world scenario. When fewer channels are being tested, the more power the ones that aren't being used can deliver. This can artificially increase the apparent power output. By testing with both channels driven we are decreasing the standard 10-20% difference of one channel driven.

What does a 10-20% power difference mean in reality? For the average person to hear a difference in loudness/level, you would need to double the power to the speakers. You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

To put it in a nut shell we basically provide a more conservative power spec of the EIA standard because we test with both channels driven during our tests not just one.

Since the differences between the two standards are really minimal, when you look at it, the more important questions should be things like amplifier features and reliability.

Thanks for the explanation. Just out of curiosity what is the watt output of the XTI 4000 with the FTC method?

Thanks

I am also very keen to know this

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Yeah id like to know this as well. I own the Xti 4000 and I think its great. Why are these specs only released on the I-techs? You said the EIA rating is typically 10-20% higher than the FTC rating. Lets say it's 15% higher. That means the rating of the Xti 4000 into 4 ohms would be 1020 watts per channel. I think it's safe to say the FTC rating of the Xti 4000 into 4 ohms is about 1000 watts per channel.

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The EIA rating IMO is useless. It doesn't tell me how much power my sub will get or anything else for that matter.

Are you guys not sharing the XTI4000 FTC figure because it is low? I know you have the figures so please share them.

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Are you guys not sharing the XTI4000 FTC figure because it is low? I know you have the figures so please share them.

I don't think they are low. It's rare that the FTC ratings are shown. I've only seen them shown with really high end amps like the I-tech. I don't think all other amps out there that are under 2K are crap. Most companies I have seen don't show this spec.

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The FTC rating is mostly used by commercial audio products and occasionally you will see a Pro Audio Product listed with an FTC rating.

Crown does a more conservative testing of products using the EIA standard than the EIA standard requires. We test with all channels driven not just one. In this scenario if the power supply sags because of trying to push a lot of current to the load the output power will go down. This is something most manufactures do not what you know. That under full load their amps don't meet the specified output power

When you compare Crown amps to others you can be guaranteed that Crown amps will meet or exceed the specified output power per channel under a full load. :)

The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

The FTC ratings were done on an the ITech amplifiers because it is our Top of the line amplifier and we wanted to. :wacko::(:wacko:

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The FTC rating is mostly used by commercial audio products and occasionally you will see a Pro Audio Product listed with an FTC rating.

Crown does a more conservative testing of products using the EIA standard than the EIA standard requires. We test with all channels driven not just one. In this scenario if the power supply sags because of trying to push a lot of current to the load the output power will go down. This is something most manufactures do not what you know. That under full load their amps don't meet the specified output power

When you compare Crown amps to others you can be guaranteed that Crown amps will meet or exceed the specified output power per channel under a full load. :)

The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

The FTC ratings were done on an the ITech amplifiers because it is our Top of the line amplifier and we wanted to. :wacko::(:wacko:

Thanks David,

I understand you guys test both channels simultaneously and other people test only one. I know you guarantee your rated wattage but my question is what are the FTC numbers available for the XTI 4000?

I want to know how much power the XTI 4000 is sending to my subs (30-150hz range) hence the reason I ask for the 20hz-20khz. I bought 3 of these amps and would like to know what its putting out. I don't mean any disrespect here but it seems you posted the ratings for the ITech because they are virtually the same as the EIA ratings. I find it hard to believe the engineers at crown have not tested the XTI 4000 wattage across the full frequency range. I don't think its too much to ask for as an owner of this amp to get the 20hz-20khz power rating. If you want me to keep quiet about it I will just PM me. My suspicion is the FTC rating must be a lot lower and that is the reason you guys don't want to publish it.

difflvl

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The FTC rating is mostly used by commercial audio products and occasionally you will see a Pro Audio Product listed with an FTC rating.

Crown does a more conservative testing of products using the EIA standard than the EIA standard requires. We test with all channels driven not just one. In this scenario if the power supply sags because of trying to push a lot of current to the load the output power will go down. This is something most manufactures do not what you know. That under full load their amps don't meet the specified output power

When you compare Crown amps to others you can be guaranteed that Crown amps will meet or exceed the specified output power per channel under a full load. :)

The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

The FTC ratings were done on an the ITech amplifiers because it is our Top of the line amplifier and we wanted to. :wacko::(:wacko:

Thanks David,

I understand you guys test both channels simultaneously and other people test only one. I know you guarantee your rated wattage but my question is what are the FTC numbers available for the XTI 4000?

I want to know how much power the XTI 4000 is sending to my subs (30-150hz range) hence the reason I ask for the 20hz-20khz. I bought 3 of these amps and would like to know what its putting out. I don't mean any disrespect here but it seems you posted the ratings for the ITech because they are virtually the same as the EIA ratings. I find it hard to believe the engineers at crown have not tested the XTI 4000 wattage across the full frequency range. I don't think its too much to ask for as an owner of this amp to get the 20hz-20khz power rating. If you want me to keep quiet about it I will just PM me. My suspicion is the FTC rating must be a lot lower and that is the reason you guys don't want to publish it.

difflvl

Yes we would all like to know, When deciding to purchase multiples of these amps as I am for 8 mixes of active monitors, I'd appreciate the piece of mind (at the least), considering all other cheaper options I have had a look at display the FTC, quest, phonic etc (admit idly without inbuilt DSPs) ... dont tell me crown arnt up to the same testing as these brands? . Its like 'this is our top speed on the straight, but we wont tell you the horsepower nor torque'

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If crown is refusing to give me ratings for a product that I bought from them and giving me a run around, then that is the last time I buy a crown amp. I'll be sure to let everyone know about this BS runaround you guys are giving me and how you guys do not want to give out the real power of the amp that you guys sell, just the "useless" 1khz figure. I have been a crown loyal until now, this really *beep*es me off.

1khz is BS marketing gimicks that companies that make weak amps use to up their wattage. Its very similar to gas mileage on a car, everyone knows the EPA ratings are with a granny driving and not normal driving. Same thing here, they use this BS 1khz to be able to publish higher wattage numbers. Who cares what the wattage is in at a single point out of the whole frequency spectrum.

Thanks for showing me what kind of company you guys really are!

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If crown is refusing to give me ratings for a product that I bought from them and giving me a run around, then that is the last time I buy a crown amp. I'll be sure to let everyone know about this BS runaround you guys are giving me and how you guys do not want to give out the real power of the amp that you guys sell, just the "useless" 1khz figure. I have been a crown loyal until now, this really *beep*es me off.

1khz is BS marketing gimicks that companies that make weak amps use to up their wattage. Its very similar to gas mileage on a car, everyone knows the EPA ratings are with a granny driving and not normal driving. Same thing here, they use this BS 1khz to be able to publish higher wattage numbers. Who cares what the wattage is in at a single point out of the whole frequency spectrum.

Thanks for showing me what kind of company you guys really are!

I strongly suggest you stop and take a breather.

First. Lets look at the FTC ratings. It is measured from 20 - 20,000 KHz. Unless you are using a full range cabinet the FTC ratings doesn't hold any weight for frequencies ranging from 30 - 150 Hertz. Reasons being you are delivering a limited frequency bandwidth, which the FTC ratings (20 - 20 KHz) cannot answer. So, you are back at square one.

David Glass answered your question right here;

The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

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.

Best Regards,

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If crown is refusing to give me ratings for a product that I bought from them and giving me a run around, then that is the last time I buy a crown amp. I'll be sure to let everyone know about this BS runaround you guys are giving me and how you guys do not want to give out the real power of the amp that you guys sell, just the "useless" 1khz figure. I have been a crown loyal until now, this really *beep*es me off.

1khz is BS marketing gimicks that companies that make weak amps use to up their wattage. Its very similar to gas mileage on a car, everyone knows the EPA ratings are with a granny driving and not normal driving. Same thing here, they use this BS 1khz to be able to publish higher wattage numbers. Who cares what the wattage is in at a single point out of the whole frequency spectrum.

Thanks for showing me what kind of company you guys really are!

Easy there Ray.

I have requested the 20-20 Khz numbers for you from our engineering department. When they are able to get to the request they will get me the info and I will get it to you.

See what type of company we are.

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If crown is refusing to give me ratings for a product that I bought from them and giving me a run around, then that is the last time I buy a crown amp. I'll be sure to let everyone know about this BS runaround you guys are giving me and how you guys do not want to give out the real power of the amp that you guys sell, just the "useless" 1khz figure. I have been a crown loyal until now, this really *beep*es me off.

1khz is BS marketing gimicks that companies that make weak amps use to up their wattage. Its very similar to gas mileage on a car, everyone knows the EPA ratings are with a granny driving and not normal driving. Same thing here, they use this BS 1khz to be able to publish higher wattage numbers. Who cares what the wattage is in at a single point out of the whole frequency spectrum.

Thanks for showing me what kind of company you guys really are!

Easy there Ray.

I have requested the 20-20 Khz numbers for you from our engineering department. When they are able to get to the request they will get me the info and I will get it to you.

See what type of company we are.

Thank you

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If crown is refusing to give me ratings for a product that I bought from them and giving me a run around, then that is the last time I buy a crown amp. I'll be sure to let everyone know about this BS runaround you guys are giving me and how you guys do not want to give out the real power of the amp that you guys sell, just the "useless" 1khz figure. I have been a crown loyal until now, this really *beep*es me off.

1khz is BS marketing gimicks that companies that make weak amps use to up their wattage. Its very similar to gas mileage on a car, everyone knows the EPA ratings are with a granny driving and not normal driving. Same thing here, they use this BS 1khz to be able to publish higher wattage numbers. Who cares what the wattage is in at a single point out of the whole frequency spectrum.

Thanks for showing me what kind of company you guys really are!

I strongly suggest you stop and take a breather.

First. Lets look at the FTC ratings. It is measured from 20 - 20,000 KHz. Unless you are using a full range cabinet the FTC ratings doesn't hold any weight for frequencies ranging from 30 - 150 Hertz. Reasons being you are delivering a limited frequency bandwidth, which the FTC ratings (20 - 20 KHz) cannot answer. So, you are back at square one.

David Glass answered your question right here;

QUOTE

The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

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.

Best Regards,

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 cannot accurately calculate the FTC rating by using a %. I have seen amps where its 10% and amps where its a 30% difference. That percentage can also be 10% at one frequency but 30% at another frequency, so that isn't a good way to find out, its good for a guess.

With the EIA method you only need to drive 1 channel (i know crown does both channels) at 1khz, thats it. With the FTC method you need to drive both channels at 20hz-20khz. Needless to say its a lot more stringent and more accurate representation of an amps true power. Play a 1khz test tone and a 20hz test tone through the same amp, see which tone draws more power. The FTC method imo is the only good method to measure wattage as it test the whole frequency range, with both and really tests the power supply a lot more than the EIA method.

In the case of home theater amps, some (cheap ones who don't provide the FTC rating) wont even complete the FTC test they will just shut down because thats how stringent the FTC method is. The FTC method also requires about a hour of testing at each individual impedance (2ohm, 4ohm, 8ohm). Same thing with these pro amps as well thats why you will rarely see the FTC for 2 ohm because most likely the amp cannot and will not handle the FTC test at 2 ohm impedance, thats why most amps that give you the FTC rating only give it to you for 8 and 4 ohms.

All the great amps out there I-Tech included have the FTC rating. I don't care what the MAX output of an amp is, I want to know what the sustained power is under stress and the EIA rating hardly stresses the amp. Maybe the EIA is fine if you are using the amp & speakers for voice or something weak like that but if you are actually pumping music with hard beats and bass through it, its a different story.

So now you tell me which rating is going to accurately tell me how much punch my amps will deliver when both channels have been on at almost full blast hours on end?

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I strongly suggest you stop and take a breather.

First. Lets look at the FTC ratings. It is measured from 20 - 20,000 KHz. Unless you are using a full range cabinet the FTC ratings doesn't hold any weight for frequencies ranging from 30 - 150 Hertz. Reasons being you are delivering a limited frequency bandwidth, which the FTC ratings (20 - 20 KHz) cannot answer. So, you are back at square one.

David Glass answered your question right here;

The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won’t hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear.

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.

Best Regards,

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.

You cannot accurately calculate the FTC rating by using a %. I have seen amps where its 10% and amps where its a 30% difference. That percentage can also be 10% at one frequency but 30% at another frequency, so that isn't a good way to find out, its good for a guess.

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.

With the EIA method you only need to drive 1 channel (i know crown does both channels) at 1khz, thats it. With the FTC method you need to drive both channels at 20hz-20khz. Needless to say its a lot more stringent and more accurate representation of an amps true power. Play a 1khz test tone and a 20hz test tone through the same amp, see which tone draws more power. The FTC method imo is the only good method to measure wattage as it test the whole frequency range, with both and really tests the power supply a lot more than the EIA method.

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.

In the case of home theater amps, some (cheap ones who don't provide the FTC rating) wont even complete the FTC test they will just shut down because thats how stringent the FTC method is. The FTC method also requires about a hour of testing at each individual impedance (2ohm, 4ohm, 8ohm). Same thing with these pro amps as well thats why you will rarely see the FTC for 2 ohm because most likely the amp cannot and will not handle the FTC test at 2 ohm impedance, thats why most amps that give you the FTC rating only give it to you for 8 and 4 ohms.

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.

All the great amps out there I-Tech included have the FTC rating. I don't care what the MAX output of an amp is, I want to know what the sustained power is under stress and the EIA rating hardly stresses the amp. Maybe the EIA is fine if you are using the amp & speakers for voice or something weak like that but if you are actually pumping music with hard beats and bass through it, its a different story.

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.

So now you tell me which rating is going to accurately tell me how much punch my amps will deliver when both channels have been on at almost full blast hours on end?

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.

Best Regards,

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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.

Right I will not be feeding the sub amp 20hz-20khz, BUT if the amp can provide for example 1000 watts into a 4ohm load per the ftc method, than my subs should see at least that number.

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.

I agree, but regardless of its intended use, in my opinion the FTC method is a very good way to test any amp be it home or pro.

The reality is that even many "pro amps" on the market will not drive a 2 ohm load @ full tilt for hours, especially amps that don't have a 2 ohm FTC rating. It depends on what you are playing through it but like I said if you are playing some real vigorous bass through the subs, the amp will most likely thermal.

In the case of the XTI4000, it uses 4 MJ21193/MJ21194 transistors which can do up to 250 watts a piece @ 25C. So if we add that up, we can only handle max 1000 watts/channel @ 25C regardless of impedance, regardless of what you do, you cannot sustain any more than that for long periods of time. Now realistically the more you push it the hotter the transistors will run and they lose about 1.4watts/1C so if you are running at 45C then you essentially lose 28 watts per transistor for a total loss of over 100 watts, so now you are left with only 900 watts.

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Forgive me if I'm wrong here but 4 of each output device equals 8 in total.

4 for negative and 4 for positive.

In a push/pull arrangement so they have 1000W capacity for each phase giving a total of 2000W.

Taking into account losses due to heat and tolerences etc.. would give you more realisitc ratings.

1200W @ 4 Ohms is a realistic figure for continous rms output.

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What I got back from the engineers is that the XTi series for FTC rating is measured at being down 1db in out put from the EIA spec (both channels driven). So what does that mean well lets look at the math for XTi4000 8-ohm spec.

The XTi4000 is EIA (both channels driven) for 650 watts into 8-ohms.

To do this we will need to calculate for the 20-20k output voltage spec. (Vspec2) and then we can calculate the output power.

1) First lets calculate the output voltage for the EIA (both channels driven) (Vspec1).

Vspec1=SQR(650*8)

Vspec1=72.11 volts

2) Now for the heavy math and reverse calculating the 20-20k output voltage spec (Vspec2) for 1db down.

-1db=20 log(Vspec2/Vspec1)

-1db=20 log(Vspec2/72.11)

-1db/20={20log(Vspec2/72.11)}/20

-0.05=log(Vspec2/72.11)

Antilog -0.05= Vspec2/72.11

.89125= Vspec2/72.11

Vspec2=.89125*72.11

Vspec2=64.27

;)

3)Now use the power formula to calculate the 20-20k output power from the Vspec2 voltage.

W= V2/8

W= Vspec22/8

W= 64.272/8

W= 516.3 watts output for 20-20k

Continuing along the same line you come up with the following chart.

XTi1000

Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec

8-ohms_______275w___________220w____________________218w

4-ohms_______500w___________400w____________________397w

XTi2000

Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec

8-ohms_______475w___________380w_____________________377w

4-ohms_______800w___________640w_____________________636w

XTi4000

Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec

8-ohms_______650w___________520w____________________516w

4-ohms______1200w___________960w____________________953w

From this you can see that, taking into account tolerances between components in different amplifiers, the XTi series sits right at the 20% difference between our EIA (with both channels driven) spec and their 20-20k output power. :)

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What I got back from the engineers is that the XTi series for FTC rating is measured at being down 1db in out put from the EIA spec (both channels driven). So what does that mean well lets look at the math for XTi4000 8-ohm spec.

The XTi4000 is EIA (both channels driven) for 650 watts into 8-ohms.

To do this we will need to calculate for the 20-20k output voltage spec. (Vspec2) and then we can calculate the output power.

1) First lets calculate the output voltage for the EIA (both channels driven) (Vspec1).

Vspec1=SQR(650*8)

Vspec1=72.11 volts

2) Now for the heavy math and reverse calculating the 20-20k output voltage spec (Vspec2) for 1db down.

-1db=20 log(Vspec2/Vspec1)

-1db=20 log(Vspec2/72.11)

-1db/20={20log(Vspec2/72.11)}/20

-0.05=log(Vspec2/72.11)

Antilog -0.05= Vspec2/72.11

.89125= Vspec2/72.11

Vspec2=.89125*72.11

Vspec2=64.27

;)

3)Now use the power formula to calculate the 20-20k output power from the Vspec2 voltage.

W= V2/8

W= Vspec22/8

W= 64.272/8

W= 516.3 watts output for 20-20k

Continuing along the same line you come up with the following chart.

XTi1000

Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec

8-ohms_______275w___________220w____________________218w

4-ohms_______500w___________400w____________________397w

XTi2000

Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec

8-ohms_______475w___________380w_____________________377w

4-ohms_______800w___________640w_____________________636w

XTi4000

Imp.________EIA Spec._______Calc.20%____________1db down 20-20K spec

8-ohms_______650w___________520w____________________516w

4-ohms______1200w___________960w____________________953w

From this you can see that, taking into account tolerances between components in different amplifiers, the XTi series sits right at the 20% difference between our EIA (with both channels driven) spec and their 20-20k output power. :)

David thank you very much. :)

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From this you can see that, taking into account tolerances between components in different amplifiers, the XTi series sits right at the 20% difference between our EIA (with both channels driven) spec and their 20-20k output power. :)

We have just purchased a pair of XLS 402s for the Lab here, so I thought I would join the Forum. Many thanks Dave for the informative Specification Calculator. Impressive FTC power outputs for a very reasonable price.

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nice info there!!

what about 2ohm though?If someone could calculate it would be great, im too lazy to do math rite now :(

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nice info there!!

what about 2ohm though?If someone could calculate it would be great, im too lazy to do math rite now :(

If you take the 2 Ohm figures quouted in the Specs, and subtract 20.5% from the figure, you should be within 1 watt or so of David's FTC figures for the 4 Ohm and 8 Ohm ratings he has posted. ;)

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