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Stereo Amplifiers >$500 (Not Integrated)

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#41
Consider NAD/Proton/Hitachi et al who 'gamed' and practically invented the 'high dynamic headroom' push in the 70s/80s. It gave spectacular transient numbers in lightweight packages at a low cost. But continuous high power amplifiers they were not.
Dear @restorer-john , i vaguely remember that you "promised" us in a post a new thread, with your recommended amps from 70-90s. My budget is so low that i can only have a proper amp from the second hand market - so I am always reading your comments on this subject. I am not urging you in any way, but please share your knowledge with us. TIA
 
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#42
Testing a Behringer Class D amp for anything other than how much power it can put into a subwoofer is probably a waste of time... Behringer's claim of .08% THD at 1kHZ is probably optimistic or at least semi-truthful (i.e. they admit how "not good" it is up front), the 20kHz THD (and IMD) are probably frightening, and the RMS rating is probably far lower than their "maximum" output. Any garden variety thrift store receiver is probably better. I can't imagine there is any useful information to be gleaned from testing one of these things. Unfortunately, there just aren't many current production "professional" products that are going to measure impressively. Most are designed to hammer out massive numbers of watts with little regard to silly stuff like distortion. Although, I suspect some of Yamaha's last generation pro gear like the P3500S might do okay. I ran across a bench test of one of them once, and recall being fairly impressed.
 

andreasmaaan

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#43
Testing a Behringer Class D amp for anything other than how much power it can put into a subwoofer is probably a waste of time... Behringer's claim of .08% THD at 1kHZ is probably optimistic or at least semi-truthful (i.e. they admit how "not good" it is up front), the 20kHz THD (and IMD) are probably frightening, and the RMS rating is probably far lower than their "maximum" output. Any garden variety thrift store receiver is probably better.
In the case of the (class A/B) A500, all of Behringer's published specs appear to in fact be conservative, i.e. the amplifier's measured performance meets or exceeds published spec on every metric.

Why would they spec their class D amps otherwise?
 

pierre

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#44
Testing a Behringer Class D amp for anything other than how much power it can put into a subwoofer is probably a waste of time... Behringer's claim of .08% THD at 1kHZ is probably optimistic or at least semi-truthful (i.e. they admit how "not good" it is up front), the 20kHz THD (and IMD) are probably frightening, and the RMS rating is probably far lower than their "maximum" output. Any garden variety thrift store receiver is probably better. I can't imagine there is any useful information to be gleaned from testing one of these things. Unfortunately, there just aren't many current production "professional" products that are going to measure impressively. Most are designed to hammer out massive numbers of watts with little regard to silly stuff like distortion. Although, I suspect some of Yamaha's last generation pro gear like the P3500S might do okay. I ran across a bench test of one of them once, and recall being fairly impressed.
The point of this forum is to go from from what you think to what has been measured. What you tell may be true or not.
Some Beringher products measure well. Some also do not failed often etc

Note: The Yamaha p3500s is at least 10 years old.
 
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#46
That's it. The graph scaling is awful, but you can see that it does .006% at 1kHz, with a small rise to about .03% at 20kHz, at 30W. At 100W, .003% and .018%. At full power it is even less, at least at 1kHz. Thus, it seems that distortion keep falling as power is increasing, which is what you want to see. Yes, 20kHz THD could be a little lower, but with over 350W available per channel, there is not much to complain about. This is better performance at 20kHz than probably 80% of the "high end" products out there, meaning that the design is more linear than a great many of them. Also, the fans apparently don't come on unless it is driven extremely hard. And if you really want lots of power, buy a p5000s or a p7000s.

There, amp shopping done. I am not sure if their newer series do as well. I haven't looked at the design. Many of the manufacturers are going all in for the weight savings and sacrificing distortion performance in the process. It's also worth noting that most pro products do not perform this well. Don't go thinking you can snag an old QSC or the Behringer copy and have behave this well. You can't. Products that ever performed like this were rare, and most are no longer in production since the landscape has shifted to higher power and lower weight. People went from schlepping 90 pound amps, to 40 pound amps, to 10 pound amps.
 
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#47
That's it. The graph scaling is awful, but you can see that it does .006% at 1kHz, with a small rise to about .03% at 20kHz, at 30W. At 100W, .003% and .018%. At full power it is even less, at least at 1kHz. Thus, it seems that distortion keep falling as power is increasing, which is what you want to see. Yes, 20kHz THD could be a little lower, but with over 350W available per channel, there is not much to complain about. This is better performance at 20kHz than probably 80% of the "high end" products out there, meaning that the design is more linear than a great many of them. Also, the fans apparently don't come on unless it is driven extremely hard. And if you really want lots of power, buy a p5000s or a p7000s.

There, amp shopping done. I am not sure if their newer series do as well. I haven't looked at the design. Many of the manufacturers are going all in for the weight savings and sacrificing distortion performance in the process. It's also worth noting that most pro products do not perform this well. Don't go thinking you can snag an old QSC or the Behringer copy and have behave this well. You can't. Products that ever performed like this were rare, and most are no longer in production since the landscape has shifted to higher power and lower weight. People went from schlepping 90 pound amps, to 40 pound amps, to 10 pound amps.
I decided to follow this up with a little hint to a pro amplifier even better than this.

One thing that makes the Yamaha perform is that it uses, if I recall, a discreet dual differential, fully complementary front end, which is not all that often seen in cheap PA amps. I suspect it might be let down some, though, by its use of a rather overly complicated output stage, Yamaha's "EEEngine" which is sort of a Class D style amp layered on top of a Class AB amp. The idea is to make the rail voltage track the input signal, like some of the old Carver amps. Weight reduction.

If you just want a standard Class AB amp, there is one (and perhaps only one) that is inexpensive and has a state of the art traditional AB design (that isn't really spendy). Sometime in the mid 1990s, a rather well known pro sound company decided they wanted to sell power amps. So they let one of their designers run wild. Instead of copying the fairly cheap to produce Crown or QSC designs, they engineered what was arguably one of the more technically advanced products of its time. This was before the "phone an order to China" days, and the products were USA designed and assembled. Compared to the cost of other products at the time, this company still managed to do it cheap by using surface mount and plastic output devices, which legacy amps of the time did not. Somehow, I mentally filed away an old Arny Krueger (RIP) rec.audio post from 20 years ago praising these amps, which I remembered a couple of years ago when looking for cheap amps that might perform well. I pulled the schematics and service manuals, and ... there it was. An amplifier that had no reason to exist, that shouldn't exist, and would never be designed today, but for some reason made it past the bean counters.

Some fairly simple analysis reveals that this amp has perhaps the best low distortion circuitry ever designed and put into any mass market pro audio amplifier, and it bests most "high end" products to this day. It is chock full of distortion reducing principles which few high end amps follow, and almost no pro amps do. Dual differential, fully complementary front end, with an extremely good performing transimpedance (or VAS) stage, lots of cascoding, a very clever compensation scheme, all using parts that were among the absolute best ever designed for the purpose.

At 1kHz with these amplifiers, you should see at or under .002% THD at full power, with a rise to maybe .007% at 20kHz, at full power of 250w. Back it off a little and that should fall to .004% or less. If that doesn't sound that impressive, look through every measurement of every amplifier on the entire internet. Almost none come close to that level of linearity. Bryston, Cambridge, Benchmark, and perhaps Arcam are the notable exceptions. Even at 20kHz, the line for THD+N just keeps heading downward along with the noise floor, and only starts to flatten on when the amp is about to clip. Happily, the company included Audio Precision measurements for some of the amps that show this textbook performance (probably taken on an old System 1). Today, you can buy these things for $200 used all day long from Guitar Center or Music Go Round. You'll need to do a low speed fan modification, since they do have a fan. Also note that the noise performance at low power isn't as good as some of the new Bryston stuff. But that could be the input circuitry, since there is effectively a preamp circuit in line at most times. If you tacked on a pair of RCA jacks directly feeding the amp section, I'm sure things would improve.

Oh yeah. The amps are the dime-a-dozen Mackie m-1400. The manual specifies less than .012% THD at any power level or frequency into 8 ohms. That was conservative. Here's a link to a dozen of them for sale for about $220, shipped. https://www.musicgoround.com/products/PSPA/power-amps?search=mackie m1400&Brand=mackie&page=1. Just get some 1/4" jack to RCA adapters or use the balanced inputs and you're off to the races, since they do have binding posts instead of Speakons. I haven't actually measured one, but there's no reason they shouldn't perform as specified, and they probably won't burn up or blow up after this many years.
 
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maty

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#48
At 1kHz with these amplifiers, you should see at or under .002% THD at full power, with a rise to maybe .007% at 20kHz, at full power of 250w. Back it off a little and that should fall to .004% or less. If that doesn't sound that impressive, look through every measurement of every amplifier on the entire internet. Almost none come close to that level of linearity...
https://www.mc2-audio.co.uk/products/s-series/

MC2-S800-specs.png


MC2-S-series-specs.png


[PDF] https://www.audio-pro.ro/files/manuals/34/s_series_manual.pdf

https://www.soundonsound.com/reviews/mc2-audio-s-series

https://www.hifiengine.com/manual_library/mc2-audio/s800.shtml

Problem, to me: low SNR at max power.

S800: 106 dB (475 watts) -> about 79-80 dB at 1 watt.

And, with very low THD, I assume they have very high NFB, so I discarded it years ago.
 
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#49
https://www.mc2-audio.co.uk/products/s-series/

Problem, to me: low SNR at max power.

S800: 106 dB (475 watts) -> about 79-80 dB at 1 watt.

And, with very low THD, I assume they have very high NFB, so I discarded it years ago.
Well, .01% THD+N (-80dB) at 1W is pretty much standard across the board except for a tiny handful of products. As for negative feedback... again, who cares? It is not the evil gremlin it is made out to be. Also, this amplifier also costs about $3000 USD. No schematic available online. And its performance claims of .03%THD at 20kHz aren't even close to as good as the one I posted. Which is $200.
 
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maty

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#50
Standard with Pro amps maybe but not with SS to Hi-Fi if you want to listen very good recordings with high/very high DR. If you only listen to modern commercial recordings, as badly recorded and with low or very low DR must be OK. At home, we need < 10 watts continuous. It is important, I think, that they have little/very little distortion and a SNR-A (1 watt) closer to 90 dB than 80 dB.

To listen to that kind of recordings (modern) it is illogical to spend a lot of money on amplification and other types of audio hard, I think.

Well, in class A or class AB amps (class D is other "world") I think how much dB of NFB is important. I agree that others do not think the same.

As far as possible / reasonable I want the music I listen to, basically created with acoustic instruments and voices without excessive treatment (vade retro Autotune), to be as realistic as possible. Too many audio systems sound spectacular but they rarely get the listener excited. I know, it is a subjective appreciation.

As for the schemes and so on, that is why I have tried lately to find a DIY design that can satisfy my demands. That can reproduce all kind of music, well recorded, be simple or complex as an orchestra. To move the speakers of my second system, with 85 dB/W/m (KEF Q100).

In class A I have already selected one, as well as the DAC (not diy) and/or the preamp. But I still have not found a class AB that meets, on paper, with my demands. :(

From Pro, I have selected, years ago, a very good german power amp < € 600.

During all this time I focused on cleaning up my terrible mains, which was the most logical thing to do. Finally I think I have achieved it. The problem now is that I have such good sound that a new amplifier is just a whimsical option!
 
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#51
Standard with Pro amps maybe but not with SS to Hi-Fi if you want to listen very good recordings with high/very high DR. If you only listen to modern commercial recordings, as badly recorded and with low or very low DR must be OK. At home, we need < 10 watts continuous. It is important, I think, that they have little/very little distortion and a SNR-A (1 watt) closer to 90 dB than 80 dB.
I keep forgetting that in Europe you have much smaller spaces. Even then, 10W isn't enough unless you listen at very low levels. I did the math in another thread. Whatever the case, you're distracting from the point, which was good amplifiers under $500. What I just posted is possible the best amplifier for the price available. Find a better specified or measuring one at a similar price and then come back and tell us about it... :) NOTE: Not interested in 1kHz measurements unless you have 20kHz measurements to go with it, or a 19+20kHz IMD measurement. These are the two most important standard measurements for revealing potentially audible problems.
 

maty

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#52
I have written it so many times that I feel lazy. I listen to about 65 dB continuous. As I listen to recordings with high / very high DR, I need 15 dB more to the peaks. I have a lot of tracks with DR15 and more.

So, I need 80 dB at normal listening, which is quite loud in a house. But sometimes the music excites me, then I need 95 dB. And that the amplifier supplies it without having to force it.

My KEF Q100 has a true sensitivity of 85 dB/W/m and 3.9 Ohms about 230 Hz. They are more 4 nominal speakers than 8 (as KEF says).

https://www.diyaudio.com/forums/full-range/334614-markaudio-fare-kef-ls50-post5718555.html

https://www.doctorproaudio.com/content.php?2273-calculators-proaudio-sound-dmx&langid=1#calc_spl

85 dB/W/m, 50 watts, random phase, 3m -> 95.5 dB.

Some days ago I had others calcs. KEF LS50 wireless vs KEF Q100 and Q150 at MAX power.

https://www.audiocircle.com/index.php?topic=161371.msg1731343#msg1731343
 

andreasmaaan

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#53
@ryanmh1 would you mind sharing your rough calculations?

I tend to agree with @maty that 1W continuous (per channel) is about as much power as most people normally use when listening at moderate levels. I'm in Europe too of course.
 
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#54
@ryanmh1 would you mind sharing your rough calculations?

I tend to agree with @maty that 1W continuous (per channel) is about as much power as most people normally use when listening at moderate levels. I'm in Europe too of course.
Pulled in from the "Overkill Amp Madness" thread (quoting myself here):

"An amplifier with properly implemented clip lights will quickly show that you need large amounts of power to listen to "big" music without clipping. Let's say we want to average, oh, 90dB on a symphonic piece. There will likely be transient peaks in that piece of music which hit +25dB over the mean, for about 115dB peak. Now, assume that the speakers are 90db/1W/1m. Put the listening position out at 2m. The inverse square law is not our friend. 1W will provide all of 84dB at 2M. The second speaker will increase this somewhat, but only if the signals are correlated. So we'll assume we get nothing out of the second speaker since a transient peak will not necessarily be shared equally by both channels. Thus, starting from 84dB, it takes us 100W to get to only 104dB. 107dB will require 200W. 110dB, 400W. You get the idea. Now, there will be some boundary reinforcement or speaker coupling that might provide another, say, 6dB, maximum.

"Various measurements have been made of front row symphony seats having 115dB to 125dB peaks. As you can see, either highly efficient speakers or prodigious amounts of power are required, preferably both."

Note that 90db/1W/1m is probably overly generous. For many large floorstanding speakers, and quite a few bookshelfs, 87dB is probably more usual. Thus, 1W gets you all of 81 decibels at listening position. I took "10 watts continuous" to mean you need a "10 watt RMS amplifier". 10W gets you all of 91. I think 250 watts should be a minimum for any serious system dedicated to anything resembling semi-realistic volume levels.
 

andreasmaaan

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#55
Pulled in from the "Overkill Amp Madness" thread (quoting myself here):

"An amplifier with properly implemented clip lights will quickly show that you need large amounts of power to listen to "big" music without clipping. Let's say we want to average, oh, 90dB on a symphonic piece. There will likely be transient peaks in that piece of music which hit +25dB over the mean, for about 115dB peak. Now, assume that the speakers are 90db/1W/1m. Put the listening position out at 2m. The inverse square law is not our friend. 1W will provide all of 84dB at 2M. The second speaker will increase this somewhat, but only if the signals are correlated. So we'll assume we get nothing out of the second speaker since a transient peak will not necessarily be shared equally by both channels. Thus, starting from 84dB, it takes us 100W to get to only 104dB. 107dB will require 200W. 110dB, 400W. You get the idea. Now, there will be some boundary reinforcement or speaker coupling that might provide another, say, 6dB, maximum.

"Various measurements have been made of front row symphony seats having 115dB to 125dB peaks. As you can see, either highly efficient speakers or prodigious amounts of power are required, preferably both."

Note that 90db/1W/1m is probably overly generous. For many large floorstanding speakers, and quite a few bookshelfs, 87dB is probably more usual. Thus, 1W gets you all of 81 decibels at listening position. I took "10 watts continuous" to mean you need a "10 watt RMS amplifier". 10W gets you all of 91. I think 250 watts should be a minimum for any serious system dedicated to anything resembling semi-realistic volume levels.
Assuming people do have speakers capable of these levels (which is untrue in the case of most home audio speakers), you've forgotten to take into account a couple of factors IMHO.

Firstly, there's the the added power from room reflections. Not boundary reinforcement (which BTW typically gives between 6 and 18dB, not a mere maximum of 6dB), but room reflections generally. In typical listening rooms and with typical speakers, the critical distance actually tends to a be <1m.

Moreover, the 6dB figure you use for decrease in SPL per doubling of distance is correct only if we assume a 100% omnidirectional source - which is never the case with conventional speakers (except in the bass).

For these reasons, beyond the first metre or less - in a real room with real speakers - there tends to be only a very slight decrease in SPL as the listener moves further away from the speakers.

So, for example, a speaker producing 83dB anechoically @ 1m is likely to produce almost the same 83dB at the listening position, whether that's 2, 3 or 4m from the speakers (and indeed more than 83dB in the bass due to room reinforcement/pressurisation). And in stereo, there will be two speakers whose outputs are correlated at least part of the time.

Now in reality, music is (or should be) mastered at about 83dB continuous. This also happens to correspond to a typical domestic speaker's power sensitivity. I'd suggest that few of us listen much louder than this much of the time (we're talking continuous here, not peak).

I more or less agree with you in other respects about maximum necessary peak power requirements for front-row level full-scale symphonic music - subject to those few provisos I mentioned above regarding room reflections, critical distance, boundary reinforcement, room pressurisation, etc.
 
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maty

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#56
To finish with the calculations.

How much watts I need to have 80 dBSPL continuous - loud in a home? 2 speakers, random phase, 3m.

https://www.doctorproaudio.com/content.php?2273-calculators-proaudio-sound-dmx&langid=1#calc_spl

* 85 dB/W/m - 2 watts - 81.5 dB

* 88 dB/W/m - 1 watts - 81.5 dB

* 91 dB/W/m - 0.5 watts - 81.5 dB

You know, Nelson Pass thinks that the first watt is very important, in home audio. But I need to more watts to the peaks, and lot of more watts with very good recordings with high/very high DR, like some jazz, acoustic groups and a lot of good orchestral recordings.

And more with modern movies! (DR17 - DR20).

https://www.audiosciencereview.com/...-marantz-av8805-av-processor.6926/post-155147
 
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Willem

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#57
Some time ago Harbeth's designer Alan Shaw did a demo in the Netherlands of his M40.1 speakers, using a beefy power amplifier with accurate and fast power meters. On music peaks the amplifier was delivering more than 500 watts per channel. Even he was surprised.
In my own case, I originally played my Quad 2805 electrosats with my old 2x45 watt Quad 303 power amplifier that I had also used with the ESL-57s that I had used before. Since the 2805s are less efficient, and since this was in a larger room than I had used ever before, symphonic music sounded a bit strained. So I concluded that I needed more power and I bought a refurbished 2x140 watt Quad 606-2. Playing softly and with not very dynamic music there was no audible difference. Playing symphonic music at semi realistic levels there was a clear difference. Since then I have added a subwoofer with its own 400 watt amplifier, but even so I think I would still benefit from more power. The question is now what would be the best strategy: a second subwoofer, given that it is the low frequencies that use most of the power, or a pair of Quad QMP monoblocks?
 
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#58
Assuming people do have speakers capable of these levels (which is untrue in the case of most home audio speakers), you've forgotten to take into account a couple of factors IMHO.

Firstly, there's the the added power from room reflections. Not boundary reinforcement (which BTW typically gives between 6 and 18dB, not a mere maximum of 6dB), but room reflections generally. In typical listening rooms and with typical speakers, the critical distance actually tends to a be <1m.

Moreover, the 6dB figure you use for decrease in SPL per doubling of distance is correct only if we assume a 100% omnidirectional source - which is never the case with conventional speakers (except in the bass).
Apart from very low bass frequencies, boundary reinforcement does not happen in most setups. In order to operate in half space instead of free space, you need to be with about 1/8 wavelength of the boundary. Speakers should not be placed that close to a boundary. As for "room reflections" ... I have no idea. Room treatment should be used to stop that mess. So far as the inverse square law, it will apply to a speaker operating as point source, which is most of them. You might defeat this with a line array, but only to an extent unless the array is fairly long. See https://www.prosoundtraining.com/2010/03/15/line-array-attenuation-ideal-vis-actual/ for measurements of a 1M array.

Thus, I think the original calculations actually do hold true. Any increases will be nominal, unpredictable, and unreliable. Unless you have very efficient speakers or horns, more power is better. Better to use a clean PA amp like a Mackie or a Yamaha for a few hundred than to burn $2000 on some 40W "high end" amplifier, assuming your preferences are other than solo guitar, chamber music, or flute music.
 

andreasmaaan

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#59
Apart from very low bass frequencies, boundary reinforcement does not happen in most setups. In order to operate in half space instead of free space, you need to be with about 1/8 wavelength of the boundary.
Where does your 1/8 figure come from? 1/4 of a wavelength is plenty. That will usually mean 6dB up to about 200 or 300Hz from the floor alone, then an additional 12dB from the front and side walls up to 100 or 200Hz perhaps, depending on placement (less a small amount for losses in homes with lossy plasterboard walls of course).

In any cases, for wavelengths that are too short to be reinforced by room boundaries, the sound will still be reflected back by a surface at some point and will continue to contribute to the total SPL in the room (see my next point and the link).

As for "room reflections" ... I have no idea. Room treatment should be used to stop that mess.
Unless you turn the room into an anechoic chamber, room reflections will dominate the sound pressure at any position greater than the critical distance, which may be 1m or less in a typical domestic room. Room treatment is not designed to kill reflections, but to absorb or diffuse specific reflections at specific points in the room. Even a very large amount of absorption (by home audio standards) will not make a large dint in the overall relative levels of direct and reflected sound (or to look at it another way, the critical distance).

There's an excellent discussion of this aspect of room acoustics - and in particular critical distance and the relative levels of direct and reflected sound in typical rooms - here.

So far as the inverse square law, it will apply to a speaker operating as point source, which is most of them. You might defeat this with a line array, but only to an extent unless the array is fairly long. See https://www.prosoundtraining.com/2010/03/15/line-array-attenuation-ideal-vis-actual/ for measurements of a 1M array.
You're right about arrays, but wrong that any speaker that is not an array obeys the inverse square law. The law applies to (idealised) omni sources and omni sources alone, it's that simple. For all non-ideal omni sources, it's a question of degree.

Better to use a clean PA amp like a Mackie or a Yamaha for a few hundred than to burn $2000 on some 40W "high end" amplifier, assuming your preferences are other than solo guitar, chamber music, or flute music.
This we both agree on. Most decent amps exceed human hearing in terms of noise and distortion, and it's always better to have some headroom.
 
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#60
My last post about this. We're getting a little too deep into the weeds about acoustics on an amplifier thread.

1/4 wavelength placement will result in boundary reinforcement, but this is only 94Hz for a 3' placement. So you get pretty much nothing about that. Unfortunately, that 1/4 wavelength placement will also cause significant boundary cancellation. 1/8 wavelength placement helps, but this results in speaker placement that is too close to the wall to prevent an insufficiently delayed first reflection. So, if smooth response is important, boundary reinforcement should NOT be relied upon to "increase" effective amplifier power. Using EQ to fix, say, a 6dB suckout just increased the power requirements by four times.

re: critical distance, right at the critical distance you gain only 3dB. Closer than critical distance, you don't get even that. The limited vertical dispersion of many direct radiating speakers (such as an MTM) can and does push the critical distance much farther from the speaker than it would be for something with controlled dispersion, even in a small room. In my room, which has a 56 square foot opening into a hallway that extends teh effective length of over 50 feet, the critical distance is somewhere out past the back wall of the room, for better or worse.

It's probably fair to simply say that all rooms and situations will be different where acoustics are concerned. I think it's best just to calculate your power requirements based on the level of directly radiated sound using the standard simple equations. If you somehow beat them, lucky you. :)
 

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