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Post by gus4emo on Oct 10, 2019 19:46:00 GMT -5
Hi all, question, isn't it the norm that an amp would double the watts from 8 to 4 ohms, if so, why does the XPA7 GEN2, which I own, goes from 520 watts for 8 ohms to 315 watts for 4 ohms in stereo, just curious....
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Post by emofrmcgy on Oct 10, 2019 19:58:42 GMT -5
Hi all, question, isn't it the norm that an amp would double the watts from 8 to 4 ohms, if so, why does the XPA7 GEN2, which I own, goes from 520 watts for 8 ohms to 315 watts for 4 ohms in stereo, just curious.... I can't find 4 ohm 2 channel specs.. 200 @8ohms 315 @4ohms ALL CHANNELS DRIVEN 520 @8ohms TWO CHANNELS DRIVEN |
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Post by gus4emo on Oct 10, 2019 20:06:54 GMT -5
Hi all, question, isn't it the norm that an amp would double the watts from 8 to 4 ohms, if so, why does the XPA7 GEN2, which I own, goes from 520 watts for 8 ohms to 315 watts for 4 ohms in stereo, just curious.... I can't find 4 ohm 2 channel specs.. 200 @8ohms 315 @4ohms ALL CHANNELS DRIVEN 520 @8ohms TWO CHANNELS DRIVEN That would be my next question, why so much power in stereo if a lot of speakers might not handle it when pushed hard? |
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Post by AudioHTIT on Oct 10, 2019 20:24:43 GMT -5
I can't find 4 ohm 2 channel specs.. 200 @8ohms 315 @4ohms ALL CHANNELS DRIVEN 520 @8ohms TWO CHANNELS DRIVEN That would be my next question, why so much power in stereo if a lot of speakers might not handle it when pushed hard? It shows what a good power supply that amp has, I even drove my Maggies with it and it really had the juice. Plenty of speakers can handle the power, and often people have their best speakers for L/R so that lets them shine when your listening to stereo. I like the design. |
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Post by jackfish on Oct 11, 2019 5:51:36 GMT -5
...isn't it the norm that an amp would double the watts from 8 to 4 ohms... No, it is not the norm. There are some that can, and many of those do not do so at equivalent frequency response and THD+N values; actually meaning that they don’t. |
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DYohn
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Post by DYohn on Oct 11, 2019 9:02:08 GMT -5
It depends on the power supply.
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Post by gus4emo on Oct 11, 2019 11:28:07 GMT -5
It depends on the power supply. I believe there's a big reason the XPA7 GEN 3 went back down to 300 watts per channel in stereo....what's your take? |
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DYohn
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Post by DYohn on Oct 11, 2019 11:32:45 GMT -5
It depends on the power supply. I believe there's a big reason the XPA7 GEN 3 went back down to 300 watts per channel in stereo....what's your take? I suspect you are correct, but I do not have direct knowledge. |
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Post by emofrmcgy on Oct 11, 2019 12:16:12 GMT -5
It depends on the power supply. I believe there's a big reason the XPA7 GEN 3 went back down to 300 watts per channel in stereo....what's your take? But it doesn't go back "down" to 300... The stereo 4ohm spec is not listed.. |
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Post by garbulky on Oct 11, 2019 13:36:06 GMT -5
Hi all, question, isn't it the norm that an amp would double the watts from 8 to 4 ohms, if so, why does the XPA7 GEN2, which I own, goes from 520 watts for 8 ohms to 315 watts for 4 ohms in stereo, just curious.... Your xpa7 is a beast. It’s pretty much what the xpr7 would have been. Remember that 4 ohm rating is for all channels driven rms which is worst case bMost of the time only two channels are absorbing power so it will shunt some of the excess power to the channels that need it. Also most of the time your power needed for a channel is about 1-2 watts |
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KeithL
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Post by KeithL on Oct 11, 2019 13:43:29 GMT -5
Everything happens for a reason.... but not all reasons are a big deal. (The power output of every amplifier on Earth is limited by something.)
And, when it comes to amplifiers, their output power is going to be limited by either voltage or current. They cannot put out more voltage than the voltage rails on their power supply can deliver... And they cannot deliver more current than their power supply is able to deliver... (And remember that, while the voltage stays the same for all the channels, each additional channel uses incrementally more current.)
There are also some limitations elsewhere in the design of the circuitry itself.
Assuming I had an amplifier that could deliver 100 watts into 8 Ohms and 200 watts into 4 Ohms... Would you be pleased that "it can double down on its 8 Ohm rating into 4 Ohms"? Or would you be disappointed that "it can only deliver half of its 4 Ohm rating into 8 Ohms"? (Both are equally true - and are simply different ways of saying exactly the same thing.)
With the balance between voltage and current capability that we've chosen for our XPA Gen3 amps.... - With only two or three channels driven they can pretty much deliver twice as much power into 4 Ohms as they can into 8 Ohms. - But, with all channels driven, the available current is the limiting factor, and, while they can still deliver more power into 4 Ohms, the difference isn't quite as great. - However, driving all channels, at full power, continuously, into 4 Ohm loads, is something you'll only ever do on the test bench, and never happens when playing music.
Therefore, their performance at full power with two or three channels driven is a more realistic representation of what you're likely to experience when actually playing music with them. In the old days many amps were rather badly under-designed...
So, back in those days, showing that an amp that was rated for 8 Ohm operation "could double down into 4 Ohms" was offered as proof that it was reasonably well designed. (And many modern AVRs are still so badly current limited that their all-channels-driven rating, into 4 Ohms or 8 Ohms, drops pretty badly.)
However, with modern well designed power amps (like ours), this simply isn't a big deal any more.
It depends on the power supply. I believe there's a big reason the XPA7 GEN 3 went back down to 300 watts per channel in stereo....what's your take? |
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Post by gus4emo on Oct 11, 2019 15:01:45 GMT -5
I believe there's a big reason the XPA7 GEN 3 went back down to 300 watts per channel in stereo....what's your take? But it doesn't go back "down" to 300... The stereo 4ohm spec is not listed.. But, isn't it listed for 8 ohms? |
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Post by gus4emo on Oct 11, 2019 15:10:56 GMT -5
Everything happens for a reason.... but not all reasons are a big deal. (The power output of every amplifier on Earth is limited by something.)
And, when it comes to amplifiers, their output power is going to be limited by either voltage or current. They cannot put out more voltage than the voltage rails on their power supply can deliver... And they cannot deliver more current than their power supply is able to deliver... (And remember that, while the voltage stays the same for all the channels, each additional channel uses incrementally more current.)
There are also some limitations elsewhere in the design of the circuitry itself.
Assuming I had an amplifier that could deliver 100 watts into 8 Ohms and 200 watts into 4 Ohms... Would you be pleased that "it can double down on its 8 Ohm rating into 4 Ohms"? Or would you be disappointed that "it can only deliver half of its 4 Ohm rating into 8 Ohms"? (Both are equally true - and are simply different ways of saying exactly the same thing.)
With the balance between voltage and current capability that we've chosen for our XPA Gen3 amps.... - With only two or three channels driven they can pretty much deliver twice as much power into 4 Ohms as they can into 8 Ohms. - But, with all channels driven, the available current is the limiting factor, and, while they can still deliver more power into 4 Ohms, the difference isn't quite as great. - However, driving all channels, at full power, continuously, into 4 Ohm loads, is something you'll only ever do on the test bench, and never happens when playing music.
Therefore, their performance at full power with two or three channels driven is a more realistic representation of what you're likely to experience when actually playing music with them. In the old days many amps were rather badly under-designed...
So, back in those days, showing that an amp that was rated for 8 Ohm operation "could double down into 4 Ohms" was offered as proof that it was reasonably well designed. (And many modern AVRs are still so badly current limited that their all-channels-driven rating, into 4 Ohms or 8 Ohms, drops pretty badly.)
However, with modern well designed power amps (like ours), this simply isn't a big deal any more.
I believe there's a big reason the XPA7 GEN 3 went back down to 300 watts per channel in stereo....what's your take? Hi Keith, I like to listen to music loud, would you use the XPA7 520 watts per channel in stereo near zero decibels, say minus 2 decibels, I have done it, but would you do it for hours? |
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Post by emofrmcgy on Oct 11, 2019 16:34:27 GMT -5
Everything happens for a reason.... but not all reasons are a big deal. (The power output of every amplifier on Earth is limited by something.)
And, when it comes to amplifiers, their output power is going to be limited by either voltage or current. They cannot put out more voltage than the voltage rails on their power supply can deliver... And they cannot deliver more current than their power supply is able to deliver... (And remember that, while the voltage stays the same for all the channels, each additional channel uses incrementally more current.)
There are also some limitations elsewhere in the design of the circuitry itself.
Assuming I had an amplifier that could deliver 100 watts into 8 Ohms and 200 watts into 4 Ohms... Would you be pleased that "it can double down on its 8 Ohm rating into 4 Ohms"? Or would you be disappointed that "it can only deliver half of its 4 Ohm rating into 8 Ohms"? (Both are equally true - and are simply different ways of saying exactly the same thing.)
With the balance between voltage and current capability that we've chosen for our XPA Gen3 amps.... - With only two or three channels driven they can pretty much deliver twice as much power into 4 Ohms as they can into 8 Ohms. - But, with all channels driven, the available current is the limiting factor, and, while they can still deliver more power into 4 Ohms, the difference isn't quite as great. - However, driving all channels, at full power, continuously, into 4 Ohm loads, is something you'll only ever do on the test bench, and never happens when playing music.
Therefore, their performance at full power with two or three channels driven is a more realistic representation of what you're likely to experience when actually playing music with them. In the old days many amps were rather badly under-designed...
So, back in those days, showing that an amp that was rated for 8 Ohm operation "could double down into 4 Ohms" was offered as proof that it was reasonably well designed. (And many modern AVRs are still so badly current limited that their all-channels-driven rating, into 4 Ohms or 8 Ohms, drops pretty badly.)
However, with modern well designed power amps (like ours), this simply isn't a big deal any more.
Hi Keith, I like to listen to music loud, would you use the XPA7 520 watts per channel in stereo near zero decibels, say minus 2 decibels, I have done it, but would you do it for hours? Insert obligatory "you're going to damage your hearing" warning here... Lol |
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Post by gus4emo on Oct 11, 2019 16:42:17 GMT -5
Hi Keith, I like to listen to music loud, would you use the XPA7 520 watts per channel in stereo near zero decibels, say minus 2 decibels, I have done it, but would you do it for hours? Insert obligatory "you're going to damage your hearing" warning here... Lol Lol....no seriously, it's not ear shattering, just awesome sound, of course I back off when a song is louder, meaning that one song was recorded louder, you know your favorite music... |
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KeithL
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Post by KeithL on Oct 11, 2019 16:57:34 GMT -5
Excluding the hearing warnings.... sure.
Here's also something to keep in mind - about amplifiers and power usage. As a very general guideline, with normal music, the loudest peaks tend to be between 10x and 20x the average level. That means that, if you're not actually clipping badly, and the peaks are hitting 500 watts, you're probably using between 25 watts and 50 watts average. (That's why amps get so hot when you test them at "continuous full power" - but not nearly so hot with music.)
Everything happens for a reason.... but not all reasons are a big deal. (The power output of every amplifier on Earth is limited by something.) And, when it comes to amplifiers, their output power is going to be limited by either voltage or current. They cannot put out more voltage than the voltage rails on their power supply can deliver... And they cannot deliver more current than their power supply is able to deliver... (And remember that, while the voltage stays the same for all the channels, each additional channel uses incrementally more current.)
There are also some limitations elsewhere in the design of the circuitry itself.
Assuming I had an amplifier that could deliver 100 watts into 8 Ohms and 200 watts into 4 Ohms... Would you be pleased that "it can double down on its 8 Ohm rating into 4 Ohms"? Or would you be disappointed that "it can only deliver half of its 4 Ohm rating into 8 Ohms"? (Both are equally true - and are simply different ways of saying exactly the same thing.)
With the balance between voltage and current capability that we've chosen for our XPA Gen3 amps.... - With only two or three channels driven they can pretty much deliver twice as much power into 4 Ohms as they can into 8 Ohms. - But, with all channels driven, the available current is the limiting factor, and, while they can still deliver more power into 4 Ohms, the difference isn't quite as great. - However, driving all channels, at full power, continuously, into 4 Ohm loads, is something you'll only ever do on the test bench, and never happens when playing music.
Therefore, their performance at full power with two or three channels driven is a more realistic representation of what you're likely to experience when actually playing music with them. In the old days many amps were rather badly under-designed...
So, back in those days, showing that an amp that was rated for 8 Ohm operation "could double down into 4 Ohms" was offered as proof that it was reasonably well designed. (And many modern AVRs are still so badly current limited that their all-channels-driven rating, into 4 Ohms or 8 Ohms, drops pretty badly.)
However, with modern well designed power amps (like ours), this simply isn't a big deal any more. Hi Keith, I like to listen to music loud, would you use the XPA7 520 watts per channel in stereo near zero decibels, say minus 2 decibels, I have done it, but would you do it for hours? |
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Post by emofrmcgy on Oct 11, 2019 17:08:18 GMT -5
Insert obligatory "you're going to damage your hearing" warning here... Lol Lol....no seriously, it's not ear shattering, just awesome sound, of course I back off when a song is louder, meaning that one song was recorded louder, you know your favorite music... Preaching to the choir here dude.. it's why I use 99db efficient speakers and front loaded horn subwoofers capable of 130db @20hz... 😉 |
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KeithL
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Posts: 9,917
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Post by KeithL on Oct 11, 2019 17:09:32 GMT -5
Here's the way it works.....
You'll notice that, as you add more channels into 8 Ohms, the rating "per channel - all channels driven" de-rates a little. (If I remember correctly, into 8 Ohms, it's 300 x 2 and only 200 x 7.)
And, if you're running only two channels, it almost doubles into 4 Ohms.
However, because the limit is partly dictated by a current limit, as you use more channels, the EXTRA POWER you get by going from 8 Ohms to 4 Ohms will decrease. (I don't have an actual number, but, with all seven channels driven, continuous, the power will probably be about the same into 8 Ohms or 4 Ohms.)
HOWEVER, because music rarely asks for full power in more than one or two channels at once... AND, because music is dynamic, and so isn't "continuously driven" anyway... In practice, and with actual music, you'll get pretty much the same power into 4 Ohms as you did with the "two channels driven" rating.
This happens for two reasons: - with music, you'll never need full power on all the channels at once - the amp actually can deliver that much power to all channels at once DYNAMICALLY (and music is dynamic and not continuous - like a test signal would be) But it doesn't go back "down" to 300... The stereo 4ohm spec is not listed.. But, isn't it listed for 8 ohms? |
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Post by gus4emo on Oct 11, 2019 19:49:48 GMT -5
Lol....no seriously, it's not ear shattering, just awesome sound, of course I back off when a song is louder, meaning that one song was recorded louder, you know your favorite music... Preaching to the choir here dude.. it's why I use 99db efficient speakers and front loaded horn subwoofers capable of 130db @20hz... 😉 Are you talking about Klipsch speakers? |
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Post by gus4emo on Oct 11, 2019 19:56:06 GMT -5
Here's the way it works.....
You'll notice that, as you add more channels into 8 Ohms, the rating "per channel - all channels driven" de-rates a little. (If I remember correctly, into 8 Ohms, it's 300 x 2 and only 200 x 7.)
And, if you're running only two channels, it almost doubles into 4 Ohms.
However, because the limit is partly dictated by a current limit, as you use more channels, the EXTRA POWER you get by going from 8 Ohms to 4 Ohms will decrease. (I don't have an actual number, but, with all seven channels driven, continuous, the power will probably be about the same into 8 Ohms or 4 Ohms.)
HOWEVER, because music rarely asks for full power in more than one or two channels at once... AND, because music is dynamic, and so isn't "continuously driven" anyway... In practice, and with actual music, you'll get pretty much the same power into 4 Ohms as you did with the "two channels driven" rating.
This happens for two reasons: - with music, you'll never need full power on all the channels at once - the amp actually can deliver that much power to all channels at once DYNAMICALLY (and music is dynamic and not continuous - like a test signal would be) But, isn't it listed for 8 ohms? My XPA7 generation 2 is listed as 520 watts per channel in stereo, for movies it's a beast, as it is for music, my main focus was why make it so heavy or should I say so powerful in stereo... |
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