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Post by mgbpuff on May 7, 2018 12:17:07 GMT -5
O.K. Now you are just showing your lack of understanding of both mathematics and engineering principles. Perhaps you should stick to subjective opinions which are valid even though they often defy explaination. That's a totally fare statement, I might not know as much as you do about mathematics or engineering principles. I'm happy to learn (seriously). What can this test teach us about how the amplifier's in question will sound or perform under a given real world scenario? This particular test is indicative of an amplifier's linearity, thus its amplified faithfullness to the unamplified input.
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Post by pknaz on May 7, 2018 12:31:51 GMT -5
That's a totally fare statement, I might not know as much as you do about mathematics or engineering principles. I'm happy to learn (seriously). What can this test teach us about how the amplifier's in question will sound or perform under a given real world scenario? This particular test is indicative of an amplifier's linearity, thus its amplified faithfullness to the unamplified input. My understanding of IMD testing is that (usually) a low frequency and high frequency are (typically) used for this test, not two high frequencies? Such as defined by SMPTE? Edit: Adding additional questions. What benefits does conducting the test in question with two high frequencies (in this case, 19k & 20k) bring to the analysis?
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Post by leonski on May 7, 2018 12:35:57 GMT -5
IMD is not a meaningless test. Especially if it's showing -35 db distortion spikes. -35 db is audible in certain instances and not a good measurement. However, those were at 100 watts of power which you wouldn't always be listening at. If you assume all your music is at 0 db then you get an idea for 30 db. However your music is not a steady state and can vary between 15-40 db normally. So if you have a zero db peak, you may be having musical information at -30 db. If the music peak was recorded at say -10 db on peaks to prevent clipping, then you have to factor that in too because your -30 db musical content would be -40 db . Old 78 rpm records had about -40 db dynamic range which quickly got worse to -30 db. For comparison, CD's have about 90 db of dynamic range and cassettes about 50. Listening however will tell you how an amp is supposed to sound to you. To answer some other folks who chimed in, Tests like this are meant to be 'worst case'. Really not much in the musical world will stress an amp in this manner. I'm less sure about some of the effects-laden Movies we are all prone to watch. I think a more fruitful way to go at it rather than distance, because after all, WHO can go from 5 feet from your speaker to 35 feet, instantaniously to get this effect? I'd rather go at it from a power and dynamic range view. And i won't beat it to death, but rather note that most rock music is highly compressed and dynamic range abused. 10db? That's STILL 10x power ratio so if you are kicking along at 5 watts, peaks will be 50. By the time you are talking 20db or more, which starts to include the better 'boutique' recordings and 'quiet' hall live stuff, you BETTER not only have plenty of power, but a quiet listening area, too. The question remains: Would such an IM test be audible? Would it matter in many cases? I personally would not take the chance. I know I've heard stuff which is ANNOYING and infrequent when using a 'D' amp. I junked out the amp and went more.....conventional....and no longer have the issues I noted.
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Post by pknaz on May 7, 2018 12:42:47 GMT -5
Do you ever listen to continuous signals at 19khz and 20khz? Ever wonder why a test like this would even be performed? Kinda like rating power at only a 1khz input signal, with one channel driven, at 10% THD, do you know anyone who listens to content under that type of a scenario? To me, this screams of "hey, we need a test that makes some amplifiers look bad on paper" If the IMD doesn't manifest until after a period of time, than this test is meaningless If the IMD doesn't manifest under real world musical content, than this test is meaningless O.K. Now you are just showing your lack of understanding of both mathematics and engineering principles. Perhaps you should stick to subjective opinions which are valid even though they often defy explaination. To be fare, I'm not saying that IMD tests, in general, are meaningless. I'm suggesting that this particular test doesn't tell me anything (or even the original tester, in this case) as it was intentionally devised to show an extreme example. If you're able to derive meaning from this test, I think there would be a large number of people (not just on this forum) who would be interested in your analysis. I'm not attempting to be antagonistic here, I am genuine in my comments.
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Post by mgbpuff on May 7, 2018 13:11:19 GMT -5
This particular test is indicative of an amplifier's linearity, thus its amplified faithfullness to the unamplified input. My understanding of IMD testing is that (usually) a low frequency and high frequency are (typically) used for this test, not two high frequencies? Such as defined by SMPTE? Edit: Adding additional questions. What benefits does conducting the test in question with two high frequencies (in this case, 19k & 20k) bring to the analysis? www.ap.com/technical-library/more-about-imd/
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Post by mgbpuff on May 7, 2018 13:28:20 GMT -5
This is pretty neat - it gives you an audio source file of an SMPTE IMD test. Listen to it. If it warbles at the 7kz, then whatever you are listening to it through has appreciable IMD distortion. The SMPTE test of 60hz and 7khz is perhaps just easier to hear than some other frequency combinations. www.audiocheck.net/testtones_imd.php
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Post by bluemeanies on May 7, 2018 14:57:08 GMT -5
IMD is not a meaningless test. Especially if it's showing -35 db distortion spikes. -35 db is audible in certain instances and not a good measurement. However, those were at 100 watts of power which you wouldn't always be listening at. If you assume all your music is at 0 db then you get an idea for 30 db. However your music is not a steady state and can vary between 15-40 db normally. So if you have a zero db peak, you may be having musical information at -30 db. If the music peak was recorded at say -10 db on peaks to prevent clipping, then you have to factor that in too because your -30 db musical content would be -40 db . Old 78 rpm records had about -40 db dynamic range which quickly got worse to -30 db. For comparison, CD's have about 90 db of dynamic range and cassettes about 50. Listening however will tell you how an amp is supposed to sound to you. To answer some other folks who chimed in, Tests like this are meant to be 'worst case'. Really not much in the musical world will stress an amp in this manner. I'm less sure about some of the effects-laden Movies we are all prone to watch. I think a more fruitful way to go at it rather than distance, because after all, WHO can go from 5 feet from your speaker to 35 feet, instantaniously to get this effect? I'd rather go at it from a power and dynamic range view. And i won't beat it to death, but rather note that most rock music is highly compressed and dynamic range abused. 10db? That's STILL 10x power ratio so if you are kicking along at 5 watts, peaks will be 50. By the time you are talking 20db or more, which starts to include the better 'boutique' recordings and 'quiet' hall live stuff, you BETTER not only have plenty of power, but a quiet listening area, too. The question remains: Would such an IM test be audible? Would it matter in many cases? I personally would not take the chance. I know I've heard stuff which is ANNOYING and infrequent when using a 'D' amp. I junked out the amp and went more.....conventional....and no longer have the issues I noted. I am not a specs person nor do I listen to music through SS EQUIPMENT...so for me specs mean just about nothing. What's important to to me is what I hear..my ears determine the good, bad and the ugly. For years I let impedence, damping factor, mega WATTS ( which seem to be popular on the EMO forum) control my listening habits. It's a combination, it's the Total EQUATION that makes music sing. That real life in the face experience. That jazz musician 👨🎤 sitting in your listening room, the sound of the ivory, and the VOICE of clarity and realism.
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Lsc
Emo VIPs
Posts: 3,337
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Post by Lsc on May 7, 2018 15:00:30 GMT -5
If it’s a glowing review it counts but if it’s not so great then the tests are invalid. 😊
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Post by chicagorspec on May 7, 2018 15:35:21 GMT -5
If it’s a glowing review it counts but if it’s not so great then the tests are invalid. 😊 Who gives a crap? It's not like anyone here owns a Gen 3, anyway. About the only Gen 3 discussion that ever takes place here is "Doesn't anyone have one of these to give me some listening impressions?", followed by crickets. Just something else to spend time on in the endless circle jerk of the Lounge.
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Post by garbulky on May 7, 2018 15:45:48 GMT -5
If it’s a glowing review it counts but if it’s not so great then the tests are invalid. 😊 Who gives a crap? It's not like anyone here owns a Gen 3, anyway. About the only Gen 3 discussion that ever takes place here is "Doesn't anyone have one of these to give me some listening impressions?", followed by crickets. Just something else to spend time on in the endless circle jerk of the Lounge. Though I don't own it, I have listened to the XPA-2 gen 3 and so has B'zilla.
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Post by rbk123 on May 7, 2018 16:12:04 GMT -5
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Post by siggie on May 14, 2018 23:02:20 GMT -5
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Post by mrranting on Jun 23, 2018 17:04:34 GMT -5
My 600 dollar onkyo rz810 is thx certified... and junk. It struggles to hit reference levels at 10ft without distortion on rf7ii, which have a 101db efficiency.
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Post by leonski on Jun 29, 2018 15:15:10 GMT -5
Yes, but I think it actually helps if it identifies that certain topologies are sonically superior. If you take The Absolute Sound’s original premise, or the “straight wire with gain” concept, then all amplifiers are (should be) trying to create the same sound (or lack of), even if they come at it from different directions. Right, but "sonically superior" cannot be derived just from comparing the specs - especially specs across different topologies - that's my point. "Straight wire with gain" is an idealistic notion and each configuration gets there with their own pros and cons. You guys are both RIGHT and slightly off-center, at least the majority of the time. Amps SHOULD, IMO sound remarkably alike driving a resistor. Which as Near as I know, does NOT exist as a speaker driver. The differences in amps derive from the various abilities to drive REAL Reactive loads. 'D' amps from B&O place limits on the CAPACITANCE the amp will drive. And I think that even 'D' amps output stage runs in A/B. This simply calls out a condition of BIAS to the output devices. That those same devices are either ON or OFF at a very high rate, doesn't change the BIAS applied to them. I would further think that the 'Best' of stuff might have different sonic signatures, but STILL be pleasing to listen to. Regardless of other conditions, the Best should generally be preferred to the Worst. Than factor in a substantial variance for what people listen for or 'value'.
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Post by boomzilla on Jun 30, 2018 2:54:13 GMT -5
This IS Emotiva's lounge, and, as I understand or recall what Mr. Levkof has previously said (please correct any misconceptions here, Keith) - 1. The specs aren't "bad." They're within spitting distance of everyone else's. - But the specs that garbulky posts seem to contradict this claim. There's a HUGE difference between an iM distortion spec of -105 dB & one of -30 to -38. 2. The upgraded blade amplifiers are specifically designed to work with the new power supply. - But from what I've read, the consensus from users seems to be that the generation 3's overall sound quality isn't what it was with generations 1 & 2 of the same amplifiers. The previous sentence will be controversial - so I'm not stating it as a fact, only as my impression, based on what I've read. 3. Some specs are more important than others. I can't argue this. Some are sensitive to IMD, others aren't. I've personally owned generations 1, 2, & 3 of Emotiva's amps. I would say that IMHO, the generation 3s definitely sound differently from the earlier models, but I'm not yet ready to say whether that difference is better or worse. There may also be some expectation bias in the Emo-verse... Some (and I'd include the Gar in this comment) are heavily specs-oriented and firmly believe that new changes in power supply technology don't provide as good a quality power as did the "traditional" power supplies with "heavy-iron" transformers and banks upon banks of power supply storage capacitors. I, personally, am an agnostic on that question. It seems to me that DC current is DC current, and however you provide it, its critical measurements would be noise, ripple, speed, and avoidance of voltage dips under peak demands. So in theory, if the DC is clean and never dips (even on a very short term basis) when under transient power demands, that HOW you provided that DC should be academic (battery = conventional power supply = switching power supply). But in practice, I don't know. An interesting experiment for an Emofest would be to have two generation 3 amps of the same model on display - one with a generation 3 power supply, the other with a generation 2 power supply. In a level-matched blind test, can listeners tell any difference?
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Post by leonski on Jul 2, 2018 19:44:10 GMT -5
Have a selection of speakers available and properly setup. At least one set of some kind of 'awful' load, maybe a higher end Thiel or equal.....Than you might start hearing differences.
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Post by rbk123 on Jul 2, 2018 19:58:40 GMT -5
An interesting experiment for an Emofest would be to have two generation 3 amps of the same model on display - one with a generation 3 power supply, the other with a generation 2 power supply. In a level-matched blind test, can listeners tell any difference? A better experiment would be to switch cases and put the guts in the other and let them listen non-blind but not knowing they were switched.
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Post by leonski on Jul 3, 2018 0:55:11 GMT -5
That's just MEAN. And funny.
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Post by pedrocols on Jul 3, 2018 9:03:27 GMT -5
If my company had to pay premium money for a certification you can bet your ass I wuld definitely brag about it even if it is useless.
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