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Post by megash0n on Oct 31, 2020 16:10:43 GMT -5
Lonnie, may I ask you a question that has reared frequently as there seemingly is conflicting information given. Sorry to derail for a moment. The XPA Gen 3 amp have the XLR pins reversed input wise ....... The question is whether Emotiva reverses the pins in order to compensate for internal inversion? For clarification: Pin1=SHIELD, Pin3=HOT/POSITIVE, Pin2=COLD/NEGATIVE. In other words say the source AV device has Pin 3 negative and pin 2 hot and then the signal goes into the amp where the input is pin 3 hot and pin 2 negative. The signal is then inverted through stage(s) so what is the result? Is the absolute polarity maintained from the source out to the amp out [minus anything in between]? If using all Emotiva gear AV device and XPA amps should the speaker wires be reversed from the amp to speakers positive to negative negative to positive in order to maintain absolute polarity? That is a good question. A long time ago when we first started building amps (long before the Emotiva days when we designed and built for other companies) the XLR standard followed the European way, which is now considered inverted phase. When the Emotiva amps were released the designs followed what we had done previously. Shortly after that the US standard (what is considered phase normal now) became popular. Internally we had many discussions about switching the amps over but we kept coming back to the same conclusion. If we do, and someone puts a new amp with an older amp, the phase of the system will be mixed and we will have some very upset customers. So we just kept the amps the way they were. It has nothing to do with which way performs better or whether or not the amp stage inverts or anything like that. It all boils down to making sure you can mix any gen of amp and it works. Now if you will give me a minute more, I would like to touch on a couple of other related things. First, your speakers don’t care and will not sound any different either way. A speaker works off of AC signals. That means it moves forwards from the center position and backwards from the center position. It doesn’t care if it moves forward or backwards first and the pressure wave it creates will be the same either way. Second, as long as you use all Emotiva amps, your speakers will be in phase with each other and that is what counts. But if you mix an Emotiva amp with a receiver or someone else’s amp, they may or may not be phase correct to each other. If they aren’t, just reverse the speaker wires on one of the amps and you are good to go. Lonnie this is what I gathered from all the reading on this topic. The strange thing is that I reversed the polarity of my xlr cable feeding my Behringer subwoofer amp and impulse response graphs show that it is not actually in phase with the rest of my gear... Which is all Emotiva. Not really a huge issue since you can swap wires or let Dirac fix it for you. It is stated to be a certain way, but for me, it doesn't work the way you say it does. Anyways, this is off topic for sure, but just wanted to add another name to the mix of people that still seem to fumble with this phase thing. |
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Post by megash0n on Oct 31, 2020 16:13:04 GMT -5
That is a good question. A long time ago when we first started building amps (long before the Emotiva days when we designed and built for other companies) the XLR standard followed the European way, which is now considered inverted phase. When the Emotiva amps were released the designs followed what we had done previously. Shortly after that the US standard (what is considered phase normal now) became popular. Internally we had many discussions about switching the amps over but we kept coming back to the same conclusion. If we do, and someone puts a new amp with an older amp, the phase of the system will be mixed and we will have some very upset customers. So we just kept the amps the way they were. It has nothing to do with which way performs better or whether or not the amp stage inverts or anything like that. It all boils down to making sure you can mix any gen of amp and it works. Now if you will give me a minute more, I would like to touch on a couple of other related things. First, your speakers don’t care and will not sound any different either way. A speaker works off of AC signals. That means it moves forwards from the center position and backwards from the center position. It doesn’t care if it moves forward or backwards first and the pressure wave it creates will be the same either way. Second, as long as you use all Emotiva amps, your speakers will be in phase with each other and that is what counts. But if you mix an Emotiva amp with a receiver or someone else’s amp, they may or may not be phase correct to each other. If they aren’t, just reverse the speaker wires on one of the amps and you are good to go. Lonnie Thank you for the clarification as I was having a difficult time in the beginning setup of my system utilizing active subwoofers w/ their own plate amps and an XPA-Gen 3 amp. To complicate matters more the subwoofers were using unbalanced inputs so I was mixing XLRs and RCAs. The phase issue wasn't really noticeable when high passing the mains and dedicating lows to subwoofers. The issue really reared its head when both mains were full range and subs overlapped the mains. At that time I struggled w/ the bass going away. Much appreciate you once again taking the time to answer. Enjoy, William Definitely look at the impulse response graphs when you get REW rolling today. Those should indicate whether each speaker is in phase with the others. |
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Lonnie
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Post by Lonnie on Oct 31, 2020 18:33:04 GMT -5
That is a good question. A long time ago when we first started building amps (long before the Emotiva days when we designed and built for other companies) the XLR standard followed the European way, which is now considered inverted phase. When the Emotiva amps were released the designs followed what we had done previously. Shortly after that the US standard (what is considered phase normal now) became popular. Internally we had many discussions about switching the amps over but we kept coming back to the same conclusion. If we do, and someone puts a new amp with an older amp, the phase of the system will be mixed and we will have some very upset customers. So we just kept the amps the way they were. It has nothing to do with which way performs better or whether or not the amp stage inverts or anything like that. It all boils down to making sure you can mix any gen of amp and it works. Now if you will give me a minute more, I would like to touch on a couple of other related things. First, your speakers don’t care and will not sound any different either way. A speaker works off of AC signals. That means it moves forwards from the center position and backwards from the center position. It doesn’t care if it moves forward or backwards first and the pressure wave it creates will be the same either way. Second, as long as you use all Emotiva amps, your speakers will be in phase with each other and that is what counts. But if you mix an Emotiva amp with a receiver or someone else’s amp, they may or may not be phase correct to each other. If they aren’t, just reverse the speaker wires on one of the amps and you are good to go. Lonnie this is what I gathered from all the reading on this topic. The strange thing is that I reversed the polarity of my xlr cable feeding my Behringer subwoofer amp and impulse response graphs show that it is not actually in phase with the rest of my gear... Which is all Emotiva. Not really a huge issue since you can swap wires or let Dirac fix it for you. It is stated to be a certain way, but for me, it doesn't work the way you say it does. Anyways, this is off topic for sure, but just wanted to add another name to the mix of people that still seem to fumble with this phase thing. This leads to the next step. The difference between electrical phase and acoustic phase. Just because something is electrically in phase, does not mean it is in acoustic phase. In fact, electrical phase has very little to do with acoustic phase if I’m being completely honest. This is easier to explain with a white board where I can draw pictures, it is easier for me to explain things when I can draw pictures, but I will do my best here. Audio signals are AC. Which means when there is no audio at all and the amplifier idling the output of the amplifier is at 0 volts. Now the audio signal will move from 0 to positive voltage and then to negative voltage along the sine wave. Also picture this. When a speaker is not playing the cone and voice coil are centered on the top plate, basically a 0 point as well and the cone can move forward as well as backwards from that center point to match the AC signal coming in. So when both are electrically in phase the cone will pull backwards when the output of the amp is at a negative voltage and will move forward when the amp is sending out a positive voltage. This creates a pressure wave that starts to move through the room. Both positive pressure and negative. This pressure wave alternates as it propagates along the length of the room. So depending on where the microphone is placed relative to the wave front, the microphone can read either a positive or negative part of the wave (usually somewhere in between). Move the mic and the readings will change depending on the frequency and the length of the wave. So while the cone of the speaker may be electrically in phase or wired opposite for inverted phase, it does not mean that what you measure will be the same. That is determined by wave propagation and distance. Now you also have to take into account that any measurement is a relative reading. Everything is measured relative to something else. So a room correction system is generating a tone. That tone starts in the DSP, moves to the DACs, then to the pre-amp outputs, On to the input of the Amp, through the amp stage and then onto the speaker wires, then through the speakers crossovers (which cause boat loads of phase shift), then to the speaker drivers themselves, which then generates a wave front in the room. That travels across the room where it gets picked up by the microphone element. Which goes through the microphone preamp, onto the Analog To Digital converts, on to the processor who’s clock has been running all this time. It then looks at how long did it take to try and calculate distance and it probably looks at the wave front as it hit the mic element. Between the two, it then runs an algorithm to determine phase relationship. Since all the speakers are in different locations, that means the phase of each speaker will be different as it is measured, but if the time delay is accounted for properly, it will assume a constant and declare a speaker is in phase or not. When the real truth is that all of the speakers are somewhere in between and not at one end of the spectrum or the other. I hope this make some sense. Lonnie |
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Post by megash0n on Oct 31, 2020 19:47:54 GMT -5
this is what I gathered from all the reading on this topic. The strange thing is that I reversed the polarity of my xlr cable feeding my Behringer subwoofer amp and impulse response graphs show that it is not actually in phase with the rest of my gear... Which is all Emotiva. Not really a huge issue since you can swap wires or let Dirac fix it for you. It is stated to be a certain way, but for me, it doesn't work the way you say it does. Anyways, this is off topic for sure, but just wanted to add another name to the mix of people that still seem to fumble with this phase thing. This leads to the next step. The difference between electrical phase and acoustic phase. Just because something is electrically in phase, does not mean it is in acoustic phase. In fact, electrical phase has very little to do with acoustic phase if I’m being completely honest. This is easier to explain with a white board where I can draw pictures, it is easier for me to explain things when I can draw pictures, but I will do my best here. Audio signals are AC. Which means when there is no audio at all and the amplifier idling the output of the amplifier is at 0 volts. Now the audio signal will move from 0 to positive voltage and then to negative voltage along the sine wave. Also picture this. When a speaker is not playing the cone and voice coil are centered on the top plate, basically a 0 point as well and the cone can move forward as well as backwards from that center point to match the AC signal coming in. So when both are electrically in phase the cone will pull backwards when the output of the amp is at a negative voltage and will move forward when the amp is sending out a positive voltage. This creates a pressure wave that starts to move through the room. Both positive pressure and negative. This pressure wave alternates as it propagates along the length of the room. So depending on where the microphone is placed relative to the wave front, the microphone can read either a positive or negative part of the wave (usually somewhere in between). Move the mic and the readings will change depending on the frequency and the length of the wave. So while the cone of the speaker may be electrically in phase or wired opposite for inverted phase, it does not mean that what you measure will be the same. That is determined by wave propagation and distance. Now you also have to take into account that any measurement is a relative reading. Everything is measured relative to something else. So a room correction system is generating a tone. That tone starts in the DSP, moves to the DACs, then to the pre-amp outputs, On to the input of the Amp, through the amp stage and then onto the speaker wires, then through the speakers crossovers (which cause boat loads of phase shift), then to the speaker drivers themselves, which then generates a wave front in the room. That travels across the room where it gets picked up by the microphone element. Which goes through the microphone preamp, onto the Analog To Digital converts, on to the processor who’s clock has been running all this time. It then looks at how long did it take to try and calculate distance and it probably looks at the wave front as it hit the mic element. Between the two, it then runs an algorithm to determine phase relationship. Since all the speakers are in different locations, that means the phase of each speaker will be different as it is measured, but if the time delay is accounted for properly, it will assume a constant and declare a speaker is in phase or not. When the real truth is that all of the speakers are somewhere in between and not at one end of the spectrum or the other. I hope this make some sense. Lonnie Your theory makes perfect sense, and I thank you very much for the thorough response. It doesn't necessarily change what I am seeing, but I do understand all the specific nuances that you are trying to depict in a short text message. I would much enjoy the whiteboard session for sure. 🙂 |
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Post by Gary Cook on Oct 31, 2020 20:20:39 GMT -5
The way I see it is, if my subwoofer is 2.5 metres away from me while the FL & FR are 2 metres away and I play a tone with a 1 metre wave length then the sub will be acoustically 180 degrees out of phase to fronts. I can fix that by setting the distances in the processor or by adjusting the phase shift in the subwoofer. Or have I missed something?
Cheers
Gary
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Post by rbk123 on Oct 31, 2020 20:28:16 GMT -5
That’s good for 1 frequency, but as you move away from it, it gets worse and then improves as you approach the next multiple of that freq.
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Lonnie
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Post by Lonnie on Oct 31, 2020 20:42:47 GMT -5
The way I see it is, if my subwoofer is 2.5 metres away from me while the FL & FR are 2 metres away and I play a tone with a 1 metre wave length then the sub will be acoustically 180 degrees out of phase to fronts. I can fix that by setting the distances in the processor or by adjusting the phase shift in the subwoofer. Or have I missed something? Cheers Gary You are correct Gary. That will align the sub to the main speakers for that specific frequency. Now your scenario does not account for surfaces between you and the speakers or the room size itself, but for the purposes of what we are discussing here, you are dead on. Lonnie |
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Post by chops on Nov 1, 2020 1:06:09 GMT -5
Sorry I don't agree with some of your comments. As stated in my initial post, page 1 of this thread, I have the DR-1's as well as a DR-3 and also own the XPA-1's and by any listening measure the new DR series of amps are noticeably quieter in my room. There is no transformer hum/buzz with the Gen 3 amps, but there certainly is with the Gen 2 series and one can easily hear the noise generated at the speaker level with the Gen 2 amps. Don't get me wrong I totally enjoyed the Gen 2 amps while they were installed and think they sound fine, but to my ears the Gen 3 amps are on a different level. Not agreeing with your comments regarding the speed of these newer amps either. Anecdotally one of the first comments from an old friend who was very familiar with my setup stated these amps sure are a lost faster. I concur. Not sure why you are not hearing it that way, speakers perhaps? I find the new Gen 3 amps to be neutral, yet dynamic, but certainly not dry and in your face. Music is conveyed with more texture, nuance and timbre with these amps in the system versus anything else I have had in there and its been a lot of different amps over the years all with big honking transformers except one. The sound is clean, clear, transparent and precise for sure but I wouldn't confuse that with dry. Not trying to be denigrating here, just have not had the same listing experience you are describing with the Gen 3 amps. Thanks Well sorry you don't agree, but just because you stated something in your initial post doesn't mean that's what everyone hears in their systems as well. It's what you hear in your system. If you were "easily" hearing transformer hum/buzz in your system with the Gen 2 amps, then there was something wrong with your amps, your system, or cables or something else. I have zero, and I mean zero noise of any kind emitting from my speakers or subwoofers with my Gen 2 amp, or any other amp I've had in this system. Not agreeing about the speed of the amps is not noteworthy either. I've listened to the same material through both my Gen 2 and my brothers DR2, and there's absolutely nothing that stands out saying one amp is "faster" than the other. Speakers, sure, amps no. Your old friend could have been hearing totally different music at a totally different volume from the last time he heard your system with the other amps. He could have been in a slightly different mood. The weather could have been different. It could have been a different time of day. All of those aspects effect what someone perceives the sound to be when compared to what they think they heard before. And memory of sound is one of the worse things to try and rely on, especially over a long period of time. And please don't try and point fingers at my speakers. They're electrostatics, some of the most reveling speakers out there. If one system is going to sound faster than the other, it's going to be mine since my brother uses traditional dynamic driver speakers, typically stand mount monitors at that. Also, when I described the DR2 as being in your face with a little dryness, I said "just a little bit more". Meaning it's noticeable but not drastic. Meaning if I didn't have the Gen 2 to compare the DR2 to, I most likely wouldn't have noticed it at all. Not to mention that my brother admits to noticing it as well, and he loves the DR2 and has no regrets buying it. And stop me if I'm wrong (and I'm not), but it looks like Lonnie tends to agree with much of what I said. Chops, Great feedback and very much appreciated. I completely agree with you about the two power supplies being indistinguishable in the real world. You are 100% correct. Just like a S/N ratio of 100db vs. 110db. The room noise is the limiting factor here and you won’t hear a difference. It is no different from a lot of specs these days. A properly designed piece of gear will not be the limiting factor to what you hear. But on a daily basis we have people calling in because they have been anguishing over a spec they saw from some other manufacterer that is a few db different in one way or another. So while it won’t make a difference in what they hear, there is a good percentage of people that put a lot of stock in the numbers. To that end, we work hard to design and build solid gear with really good specs (which we back up with real data). Now the way an amplifier, pre-amp or whatever sounds is a whole different thing. The core design of all our amps is one that was developed roughly 15 years ago and was or is used in the Gen 1, Gen 2 and Gen 3 models. The big difference between the Gen1 or 2 and the current Gen 3 is obviously the power supply and the main amp stage is now Class H ( or rather a modern day version of our first amp the MPS). Our first amps were class H but we went to Class A/B because they were lower in cost and easier to build. The current Gen 3 is a modern iteration of the original MPS. Modular in design, Class H drive stage and such. However, the core part of the amplifier stage is Class A/B just like the Gen 1 and 2. Where the Class H comes into play is in how the power from the power supply is delivered to the main output transistors. Rather than just connecting the main output transistors directly to the high power rails, we employ a variable control system that feeds the main output transistors a bit more than what they need to. That way the audio stage is running at it’s maximum efficiency. Now if they sound lean or dry, that would most likely be from the dual differential, which is actually the input stage of the amp. The current sources that power the dual diff are cross linked so they stay in perfect balance at all times, but there is a current control and if we were to increase this a little, it would most likely fatten up the sound. As we developed new generations, we try to keep the sonic signature the same from gen to gen, but it really doesn’t take much to slightly shift how something sounds. So I will look into this. Lonnie Hello again Lonnie, and thank you for the detailed response! As far as published numbers are concerned, I usually only use them as a loose reference, just to get an idea. I don't ever make any purchase decisions on numbers alone. I take in professional review to an extent, and even more so those of actual owners of the gear in question. If anyone is going to be honest in their reviews of gear, it's going to be owners as they aren't going to benefit from stretching the truth or sugar coating a review. Professional reviewers have a totally different agenda with their reviews than the general public does. Kind of like what Spock said in Star Trek, "The needs of the many outweigh the needs of the few", I say... "The reviews of the many outweigh the reviews of the few". The many being the owners, vs the few being the actual reviewers. If you get a bunch of similar results from a bunch of owners reviews vs some mixed views from professional reviewers, I'm going to go with the owners reviews every time. As you said, "Now if they sound lean or dry, that would most likely be from the dual differential, which is actually the input stage of the amp. The current sources that power the dual diff are cross linked so they stay in perfect balance at all times, but there is a current control and if we were to increase this a little, it would most likely fatten up the sound". That might just be what everyone is hearing with the new Gen 3 amps. Again, I'm not saying the new Gen 3 amps are bad or lesser amps. Just that from what I have heard, I prefer my Gen 2. And it would be ridiculous to think one amp is better built or sounds better just because it weighs more than another. Thanks again Lonnie for your time. |
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