|
|
Post by Dan Laufman on Sept 20, 2017 15:41:35 GMT -5
Hi all, Ok, we pulled an XPA-2 G3 out of the warehouse this morning and tested it just like Stereophile does. We don't appear to have an issue. The IM testing shows the 1 watt 8 ohm second harmonic is down by 90dB. This around .0032%. The 60 watt (20% of rated power) test shows the second harmonic down by 75dB. This is about .018%. Very respectable. However, we do take issue with Stereophile's arbitrary 100 watt test point, as this is the same power point being used on 500+ watt mono block in the October '17 issue. I feel that 20% of rated power is probably a more realistic power point. In this case, we reference to 300 watts at 8 ohms. As you can see looking at the residual noise spectra, any spurious noise is down in the mud, and in no way affects the audible performance. I'm not going to spend time arguing the merits of sound quality from one amp to another. We believe we make a fine sounding amplifier that is very well behaved and neutral. I hope this helps calm everyone down. I'lll send my results to Stereophile for comment. I'm still trying to track that review unit down... Cheers, Big Dan XPA-2 1 watt 1920.pdf (167.3 KB) XPA-2 60 watt 19201.pdf (175.96 KB) |
|
|
|
Post by geebo on Sept 20, 2017 15:52:37 GMT -5
Hi all, Ok, we pulled an XPA-2 G3 out of the warehouse this morning and tested it just like Stereophile does. We don't appear to have an issue. The IM testing shows the 1 watt 8 ohm second harmonic is down by 90dB. This around .0032%. The 60 watt (20% of rated power) test shows the second harmonic down by 75dB. This is about .018%. Very respectable. However, we do take issue with Stereophile's arbitrary 100 watt test point, as this is the same power point being used on 500+ watt mono block in the October '17 issue. I feel that 20% of rated power is probably a more realistic power point. In this case, we reference to 300 watts at 8 ohms. As you can see looking at the residual noise spectra, any spurious noise is down in the mud, and in no way affects the audible performance. I'm not going to spend time arguing the merits of sound quality from one amp to another. We believe we make a fine sounding amplifier that is very well behaved and neutral. I hope this helps calm everyone down. I'lll send my results to Stereophile for comment. I'm still trying to track that review unit down... Cheers, Big Dan View Attachment View AttachmentI'm certainly enjoying the sound of my Gen 3 XPA-2. Very much so. And the top end using the T2's is crystal clear. The combination is better than my monoblock XPA-1Ls and the ERT 8.3s. |
|
|
|
Post by garbulky on Sept 20, 2017 15:55:26 GMT -5
How well do EMO amps do when confronted with highly reactive loads? It depends on how reactive they are. Sometimes they say "Calm down, Sir. I didn't mean it like that" Other times, "excuse me?!" and "well, I never!" |
|
|
|
Post by jimangie1973 on Sept 20, 2017 16:14:53 GMT -5
If the amp is clean at rated power (300W) with a single tone in the 19-20 kHz range, it should be clean with the 19+20 KHz IM signal at 1/2 rated power (150W). These two signals have the same peak signal level, with the IM signal having a larger peak to average ratio. So if the spec says low THD out to 20KHz, the unit is not meeting it's spec if it can't do this.
|
|
|
|
Post by ryanmh1 on Sept 21, 2017 9:30:17 GMT -5
The 60 watt (20% of rated power) test shows the second harmonic down by 75dB. This is about .018%. Very respectable. However, we do take issue with Stereophile's arbitrary 100 watt test point, as this is the same power point being used on 500+ watt mono block in the October '17 issue. I feel that 20% of rated power is probably a more realistic power point. In this case, we reference to 300 watts at 8 ohms. I'm not going to spend time arguing the merits of sound quality from one amp to another. We believe we make a fine sounding amplifier that is very well behaved and neutral. I hope this helps calm everyone down. I'lll send my results to Stereophile for comment. I'm still trying to track that review unit down... Reassuring. The apparent slew limiting that was happening on their review unit does not show up. I too have never cared for their frequency sweep test. The power level is NOT standardized, but it is at least better than ages past when they always ran it at an often pointless 2.83V. Now they perform it at an arbitrary level intended to get the distortion high enough to show the distortion rising out of the noise floor. They OUGHT to run it at full rated power. The sadly departed Audio magazine used to do this, and also ran sweeps at 20Hz, 1Khz and 20kHz. That's a better test, and reveals whether the amp meets a proper FTC power specification, e.g..: "200wpc into 8r with less than .0X% THD+N from 20Hz to 20kHz." If an amp pulls that off, and has a low noise floor, it is highly unlikely it will have audible issues except to people who claim to hear things that don't exist <ducking for cover>. Unfortunately, almost no one even publishes FTC specifications anymore. To your credit, you guys do, albeit using a standard .1% threshold, which is more typical of pro amp specifications. |
|
|
|
Post by leonski on Sept 21, 2017 12:33:12 GMT -5
To Stereophile's credit, they DO precondition amps at 1/3 rated power for a time BEFORE doing some tests. This is worst case for an A/B amp.
Some amps with marginal heat sink capacity can get hot enough to 'cook on'.
And the 2.83v testing? Isn't that 1 watt @8ohms? That is the first watt situation. Who wants 200 watts when the FIRST WATT is awful? You are far mor elikely to use 5 watts per side with
50 watt peaks (10db) or maybe 300 watt peaks (about 18db) where you'll probably not hear problems due to the brevity of the issue.
|
|
|
|
Post by ryanmh1 on Sept 21, 2017 15:22:51 GMT -5
To Stereophile's credit, they DO precondition amps at 1/3 rated power for a time BEFORE doing some tests. This is worst case for an A/B amp. Some amps with marginal heat sink capacity can get hot enough to 'cook on'. And the 2.83v testing? Isn't that 1 watt @8ohms? That is the first watt situation. Who wants 200 watts when the FIRST WATT is awful? You are far mor elikely to use 5 watts per side with 50 watt peaks (10db) or maybe 300 watt peaks (about 18db) where you'll probably not hear problems due to the brevity of the issue.
Right. The preconditioning at 1/3 power was an old FTC requirement. They changed to 1/8 power 17 years ago since the 1/3 requirement was, to summarize, stupid. And yes, 2.83V is one watt. Many of their frequency sweeps back in the 90s basically showed you the noise floor of the amplifier.... IMHO, the "first watt" theory is mostly silly. If the amplifier measures wonderfully at full power, it will usually be perfectly fine with one watt. Nothing is being stressed at one watt, and the distortion is often still buried in the noise (ii.e. you can't hear it anyway). In any event, I did finally cave and by an XPA-5. But it was a Gen 2 refurb off ebay...  It should be enough power for surround duty. I was debating getting a used Rotel or a new Monolith, but this was cheap and new and had a short warranty. I just needed a solution other than a receiver amps or using a stack of two channel amplifiers (which I already have, but that's a low WAF). I'll just use a different amp on the mains to get enough power on them. I have plenty of them. There's just a rather low WAF to putting a stack of four hundred pound amplifiers in your living room. And then subs , an speakers, and wel... You know. |
|
|
|
Post by Gary Cook on Sept 21, 2017 15:56:38 GMT -5
There used to be some correlation between the amplifier testing criteria of the audio magazines, 1 watt and 20% of its rated power was the rule of thumb. Conceptually that was to represent what the consumer of that particular amp would expect/experience in the real world. Even I could see the logic in that, 1 watt to give a base line and then 20% to represent the most likely common maximum continuous volume whilst leaving room for dynamic peaks.
These days reviewers use all sorts of criteria, with little agreement/alignment, which a number of people have said to me is deliberately done to stop reviewer to reviewer comparison. For example it's next to impossible now to compare 2 amps tested by 2 different reviewers as we can't put the numbers next to each other and do a line by line comparison, I believe that the idea behind it is that we can only compare tests done by the same reviewer, so we have to wait/buy/read reviews from the same source of the different amplifiers in our range of possible purchases. Increased audience and increased advertising revenue being the drivers.
Cheers
Gary
|
|
|
|
Post by leonski on Sept 22, 2017 0:15:16 GMT -5
To the extent that the preconditioning 1/3power is 'stupid', I must disagree. It IS worst case scenario and will stress an amp in ways the vast majority of users never will. It will also perhaps 'accelerate' the lifetime process and give you some idea of reliability. I personally can't see the point of some of these Mondo Amps, run on 15 amp circuits and if redlined would need a 20 amp circuit. And than, if you did have the proper power to the amp, they have insufficient heatsink to support such output Many amps require a variac to keep from 'sagging' the input power. Something not even I am nutty enough to own. Too much emphassis is placed on 'measurables'. However, I will concede that measurable and hearing can go together. The stereophile test of the G3 may be an example of hearing something in review while later finding something in the measurables to account for what you heard. I'd love to see the Re-Test data with some listening comments. But the basic measures? Nearly worthless, especially without analysis and some knowledge of how various factors interact. Simple RMS power into a resistor and distortion don't really tell you how the amp responds to a real speaker. No standards yet exist, though many simulated speaker loads are viewable online. Reviewers? Who cares? Unless you know what the reviewer values, you might have trouble (will, I suspect) when trying to compare. The job of the reviewer is maybe to 'find value' which is why you read so few Poor reviews. You CAN compare, but need to know about the reviewer as much as What he or she is reviewing. I have not read enough reviews to reach any conclusions about modern reviewers. In this case, I'll side with Nelson Pass who named one of his companies 'First Watt'. If you really think you gotta turn it up Loud....NO, Louder! I'd recommend a real search for high sensitivity speakers with large power handling, too. If I were starting over today, I'd be searching for such speakers and a good amp to match. My very low sensitivity panels really DO need a lot of power but are fortunately not that bad a load, at least if the amp can produce sufficient 4-ohm current. A search for some modern Field Coil speakers will show you what 5 or 10 watts can really do. My 7watt x 2 amp in the garage does wonders. Maybe one day I'll experiment with some high sensitivity speakers rather than the cast-off sealed speakers now in service. I WISH I could get away with something like the Krell KSA-50 or perhaps the Pass XA-30.5 or the XA30.8 Either are perfect into higher sensitivity speakers and have arc-welder like power supplies. And also weigh maybe up to 1 pound per watt or more. Your 2x300 amp would go 300lb and require a fork-lift to move. |
|
|
|
Post by ryanmh1 on Sept 22, 2017 13:07:43 GMT -5
To the extent that the preconditioning 1 /3power is 'stupid', I must disagree. It IS worst case scenario and will stress an amp in ways the vast majority of users never will. It will also perhaps 'accelerate' the lifetime process and give you some idea of reliability. [SNIP] But the basic measures? Nearly worthless, especially without analysis and some knowledge of how various factors interact. Simple RMS power into a resistor and distortion don't really tell you how the amp responds to a real speaker. No standards yet exist, though many simulated speaker loads are viewable online. [SNIP] It was bad as part of a standard because it represented an unrealistic condition that was requiring excessive heatsinking and other maladies. As a way to try to break something that normally would never break? Great test. Seems it might have broken the Gen3, but who really knows. Basic, comprehensive measurements tell you whether the amp is linear or now and whether it will color the sound. A simple 1kHz test? Worthless. A full power sweep? Great test. Stereophile also tests a simulated reactive speaker load. If the frequency response remains flat, you're probably in perfectly good shape. The PowerCube is a great test for real world performance. It's too bad no one uses it. While we're on the subject of Stereophile's review, there's another curious anomaly worth pointing out. On the frequency vs power graph the THD+N is effectively the same into both 8 and 4 ohms. Odd. That normally would not happen. The drop in impedance ought to increase either the noise floor or the distortion. And then, suddenly the noise drops right at 20V (50W/100W into 8r/4r respectively). I have no idea what is causing either of these anomalies. It if was a Class G amp, it's common to see a big blip where the amp switches rails. But this is a class H, where the rails "track" the signal. If you look at Emotiva's own AP results, there is a "blip" right around 60W. Could be an anomaly, but it's interesting that it's right around the same point within a reasonable margin of error. The test posted above was for a 19+20kHz IMD test at 60W. Good, but on second thought, not really good enough. We're talking about pro audio amp technology (SMPS+Class H) that has always been problematic for high frequencies, reportedly being tamed for high end use. I don't doubt that Emotiva cured many of the Class H/SMPS issues that have been out there, but I still think a 20kHz power sweep would be nice to see, along with a high power frequency sweep. That would reveal a lot, and what I suspect is probably a pretty remarkable engineering achievement. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 22, 2017 14:24:55 GMT -5
Too much emphassis is placed on 'measurables'. However, I will concede that measurable and hearing can go together. The stereophile test of the G3 may be an example of hearing something in review while later finding something in the measurables to account for what you heard. I'd love to see the Re-Test data with some listening comments. But the basic measures? Nearly worthless, especially without analysis and some knowledge of how various factors interact. Simple RMS power into a resistor and distortion don't really tell you how the amp responds to a real speaker. No standards yet exist, though many simulated speaker loads are viewable online. This made me think of something I personally wondered upon reading the Stereophile review. There appears to be speculation by JA at the end of his measurement section that the IMD behavior measured from his review sample amplifier was responsible for the observation of "transistor sound" or "hard/masculine sound" by Herb, never mind that HR was making the comparison between the Emotiva and his TUBE-based PrimaLuna amp driving the same speakers, when the sonic character of tubes, and the technical reasons behind that character, are both well known and are the subject of profound biases by many reviewers, owners, and listeners. It remains extremely specious to directly correlate measured characteristics of a piece of gear with its audible characteristics, let alone another person's impression of those characteristics, without first demonstrating the universality of that correlation (as in, "most or all listeners will perceive X measured characteristic as Y audible characteristic"). Your ears aren't a microphone, and your brain isn't a calibrated test instrument, no matter how many pieces of gear you have heard, so your impressions, while relevant to a buyer who is not technical and will enjoy the piece of gear by listening to it, cannot always be necessarily correlated to small measured variances by a calibrated and highly accurate electrical instrument. Measurements of a certain type and outcome don't guarantee that you will or won't like the sonic character (or lack of a desired character) of the piece. Measurements only provide quantitative (and when graphed, visual) analysis of specific types of behavior of the gear, for which there are preferred ranges, thresholds, and tolerances. The measurement gear can only tell you how the thing performs according to certain criteria; it can't "hear" the piece of equipment for you and tell you if you personally will like it. You can only hope to establish some sort of correlation between measured results and audible results for yourself, and not somebody/everybody else, because auditory experience is known to differ from person to person, as are the preferences around those experiences. (The studies by Toole, et. al. at Harman have only substantiated a 'consensus view' about what people tend to like, but they do not eliminate outliers, nor do they prove that those with non-mainstream tastes are somehow not actually enjoying the systems they have assembled to cater to those tastes.) The way I see it, the XPA Gen 3 review by Stereophile held mixed conclusions because the review piece was placed by the editorial staff into the care of a reviewer with known biases and preferences (tube sound, or SS gear with tube warmth baked-in), even though the product was not designed to cater to those biases, and then the assessment of the measurement results attempted to paper over that inconsistency by trying to associate what criticism there was of the unit's sound with a particular measurement that didn't turn out as well as JA would like, even though our own evaluation of an equivalent production unit using Stereophile's IMD test turned in better results than JA's unit did (as did a prior production unit tested by Secrets of Home Theater and Hifi), and furthermore it hasn't been well established that the result of that particular measurement would reliably or universally lead to HR's particular assessment of the unit's sound (the classic correlation vs causation issue). Stereophile has an enviable status among review magazines but that's no guarantee that things don't go pear-shaped for a review here or there because the reviewer's preferences are not especially catered to. The Gen 3 amps (as with all Emotiva amps) are designed to be an uncolored lens on the input signal, and not to impart any coloration to the sound, however desirable, because it isn't strictly accurate. In that sense, it should be unsurprising that the Gen 3 amps were so well liked by Herb's pal "Mr. Objective", because they were designed for him. And I was happy to see that Herb was charitable enough to frame the disconnect in his article to show that his tastes for/against a particular piece of gear might not be the absolute among listeners, and it is important to consider the source. This is my own view, not the official position of the company on this review or Stereophile as a publication. I like reading Stereophile, and I've met Herb in person, and he's just as nice a person as can be. He is the kind of listener I want to be when I grow up. I also think of him and Jana D. as the "friendly face" of Stereophile, and I hope they both stay friendly. |
|
|
|
Post by leonski on Sept 22, 2017 14:52:48 GMT -5
I've been posting the odd link for the Power Cube system for over 5 years now. In that regard you're preaching to the Choir. Stereophile merely reports the phase data for the speaker, not generally for how an amp performs INTO various reactive loads. Except for some comments in the speaker measurment section about 'needs a good 4 ohm rated amp' or 'easy to drive'. IMO, amplifier designers and speaker designers simply do NOT communicate well. Who's idea was it to sell the 1 ohm Apogee Scintilla? Or how about most Electrostats which are massively reactive for the top octave? Many other examples, some from entire lines of speakers, some isolated. How is it possible to have 'excessive heat sinking'? How many listeners are equipped to deal with phase data or the single chart version, called the Smith Chart? All that talk of Class G and Class H leaves me cold. They are ALL driving conventional A/B output stages. I'm not qualified to comment on measurment artifacts, but DO know that in the case of my old amp, now sold, that it had B&O ASP 'd' modules which include on-board PS. When tested, using a test I consider a good marker, but not yet mentioned, that of the 10khz Square Wave, you could see a sawtooth which was clearly the switching frequency of hte PS. Audible? I found these amps to be a little weird in the highs. I eventually sold them for a conventional, Linear PS, A/B amp. My Carver Cube (m400t) had some kind of tracking PS, too. Amp ran very cool until pushed right to the limit for longer time periods and when being so pushed, would flicker the house lights in time to the music. I think the amp clipped the voltage peaks on the power line. The measures you mention are not an assurance of good OR bad sound. Some correlations exist, but still and all, some amps which don't measure particularly well sound find while others, which measure fine can have some problems, usually poor sales. And than you have the odd amp, like the (ancient) Phase Linear 400 which would go ultrasonic and emit all the smoke at once. OOOPS! I'm attaching a link to the B&O models: www.icepower.bang-olufsen.com/files/solutions/icepower1000aspdata.pdfGeneral specs and some interesting graphs to mull over. I no longer see what I was looking for. Amp MIGHT be whatever powe rating but for Short Time Periods. Either 30 seconds or 60 seconds, depending on module, as well as severe power limits at higher frequencies due to risk of burning up the output Zobel. ALL amps in this series have phase shift issues at higher frequencies due to limited bandwidth. You might say, they go well past sudibility but at the same time, the phase shift is awful. I think THAT's what caused my long term problems with these amps. The Comments by Rory are a fine example of why reviews, at least the text part, are nearly worthless UNLESS you know about the reviewer and his values. The measurment part, too, must be taken with a grain of salt since a lot of conflict revolves around exactly WHAT they mean and why. Best of luck. |
|
|
|
Post by jimangie1973 on Sept 22, 2017 16:31:58 GMT -5
In this case, with the Stereophile review of the Gen3, the measurements show clearly that the amplifier is not linear in the top octave. It's not only in the dual tone IMD, it's also clearly seen in the single tone THD above 10kHz. You can say all you want about whether or not it's audible or not, but it is a fact that it is not linear. In my case, I don't want an amp that cannot cleanly reproduce the audio spectrum when so many amps exist than can. I'm disappointed too because I was considering the Gen3 prior to seeing its measurement data.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 22, 2017 16:36:36 GMT -5
In this case, with the Stereophile review of the Gen3, the measurements show clearly that the amplifier is not linear in the top octave. It's not only in the dual tone IMD, it's also clearly seen in the single tone THD above 10kHz. You can say all you want about whether or not it's audible or not, but it is a fact that it is not linear. In my case, I don't want an amp that cannot cleanly reproduce the audio spectrum when so many amps exist than can. I'm disappointed too because I was considering the Gen3 prior to seeing its measurement data. Hello Jim, I think you missed these: emotivalounge.proboards.com/attachment/download/27995 emotivalounge.proboards.com/attachment/download/27996These are our measurements of a production unit. As you can see, our measurements under identical conditions don't confirm the Stereophile data. Instead, they show an amplifier that is quite linear. See the prior post by Big Dan for explanation: Hi all, Ok, we pulled an XPA-2 G3 out of the warehouse this morning and tested it just like Stereophile does. We don't appear to have an issue. The IM testing shows the 1 watt 8 ohm second harmonic is down by 90dB. This around .0032%. The 60 watt (20% of rated power) test shows the second harmonic down by 75dB. This is about .018%. Very respectable. However, we do take issue with Stereophile's arbitrary 100 watt test point, as this is the same power point being used on 500+ watt mono block in the October '17 issue. I feel that 20% of rated power is probably a more realistic power point. In this case, we reference to 300 watts at 8 ohms. As you can see looking at the residual noise spectra, any spurious noise is down in the mud, and in no way affects the audible performance. I'm not going to spend time arguing the merits of sound quality from one amp to another. We believe we make a fine sounding amplifier that is very well behaved and neutral. I hope this helps calm everyone down. I'lll send my results to Stereophile for comment. I'm still trying to track that review unit down... Cheers, Big Dan |
|
|
|
Post by jimangie1973 on Sept 22, 2017 17:06:38 GMT -5
Hi Rory,
I saw that, but it was not the identical conditions as the Stereophile review. Stereophile ran IMD at 100W and Emo did it at 60W. Until I see a plot of IMD at 100W, I'll assume the Stereophile data is valid. The problem I'm having is Emo advertises the Gen3's performance as 0.1% THD at full power 20Hz-20KHz. Clearly it cannot meet 0.1% at full power above 10KHz. If that's how it performs, so be it, but don't spec it as something it's not.
|
|
|
|
Post by wilburthegoose on Sept 22, 2017 17:29:30 GMT -5
But does it sound better than a Gen 2? |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 22, 2017 18:42:37 GMT -5
Hi Rory, I saw that, but it was not the identical conditions as the Stereophile review. Stereophile ran IMD at 100W and Emo did it at 60W. Until I see a plot of IMD at 100W, I'll assume the Stereophile data is valid. The problem I'm having is Emo advertises the Gen3's performance as 0.1% THD at full power 20Hz-20KHz. Clearly it cannot meet 0.1% at full power above 10KHz. If that's how it performs, so be it, but don't spec it as something it's not. I will leave it up to Dan or Lonnie to present any further test results, but the assertion is that the amplifier tested to produce our published specifications did in fact meet them at the time they were generated. I would think that whatever led to the erroneous IMD measurement appearing in Stereophile could also be linked to the rise in THD above 10kHz, and thus the THD vs F plot could also be in error, but my understanding is not deep enough to say for sure. |
|
|
|
Post by Jim on Sept 22, 2017 19:42:47 GMT -5
I don’t put much faith in the Stereophile measurements given how they conveniently left out the fact they they weren’t even testing a production unit.
Oversight? Perhaps. Terribly important? Perhaps not. But never the less, it dents their credibility.
I have no doubt that if you stopped by Emotiva on a quiet day, they’d run a test right in front of you. I believe that AP tests are part of the QA process as well.
I lost interest in Stereophile after drowning in ads that didn’t interest me.
Given how Emotiva typically does publish AP data, it’s rare to see a test scenario that looks like it is selected just to obtain favorable measurements.
The published module AP data says that it’s .1 THD at 300W, using a 20hz-20khz. Who tests with only a band of say, above 15khz?! It’s not even audible for most people. Is it just choosing an arbitrary measurement that looks bad?? Sure. Maybe 15khz-20khz has higher THD. So what? It’s like evaluating how well a car can fly.
|
|
|
|
Post by rbk123 on Sept 22, 2017 20:02:41 GMT -5
If measurements were so important, no one would buy tube amps. To put so much blind faith into ears that aren't yours and data that isn't your own, never ceases to amaze me. Why wouldn't you just get the Emo amp yourself and try it out for free? Send it back if it doesn't sound good; zero risk.
Can people not determine for themselves whether something is good, if someone in the press says otherwise? I guess one can't impress one's fellow golden-ears if Stereophile says it's not to snuff.
|
|
|
|
Post by bolle on Sept 23, 2017 3:11:18 GMT -5
I will leave it up to Dan or Lonnie to present any further test results, but the assertion is that the amplifier tested to produce our published specifications did in fact meet them at the time they were generated. Well if it is so easy why don´t you just publish that exact same measurement? Otherwise we are comparing apples with - whatever.  |
|
It should be enough power for surround duty. I was debating getting a used Rotel or a new Monolith, but this was cheap and new and had a short warranty. I just needed a solution other than a receiver amps or using a stack of two channel amplifiers (which I already have, but that's a low WAF). I'll just use a different amp on the mains to get enough power on them. I have plenty of them. There's just a rather low WAF to putting a stack of four hundred pound amplifiers in your living room. And then subs , an speakers, and wel... You know. 
