How much power (wpc) is more than enough for most speakers and systems?

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bluegrassphile

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My main priorities for a new amp are superior sonics/outstanding tone/ superb sound...whatever you want to call it. I think you know what I mean. Next in line for me is output power, with enough to effectively cover transient peaks with inaudible distortion, with pretty much any speaker. In my case it would be Harbeth Super HL 5+ 40th Anniversary Model speakers. Just for the record the Harbeths are 6 ohm speakers.

So, given the info above, for you, how much power would meet the minimal requirement for most speakers and systems? Twenty five wpc? Fifty wpc? Eighty wpc? One hundred wpc? One hundred twenty five wpc? One hundred seventy five wpc? Two hundred fifty wpc? More? Keep in mind I'm not talking about any other feature of the amp. Just output power. I realize we're probably not talking about most class A amps as their output levels are usually less than 30 wpc x 2 into 8 ohms. Some class AB amps have a certain amount of class A bias. For example the Luxman 590axii. It is class A up to 30 wpc and then converts to Class AB and outputs approximately 90 wpc x 2 into 8 ohms, according to some magazine tests.

Anyway, how much power is enough for most scenarios? I would think 75 wpc x 2 into 8 ohms would do the job, except, for loud transients. And that's what concerns me most regarding minimum power requirements...higher volume transients, compression and distortion. How much output power is enough to confidently cover them?
 
I would think that in addition to considering the load of the speakers in question (6 ohms in your case), the efficiency of the speaker would also help to determine how many watts per channel you'd also need in order to have enough headroom for transients. Personally, I have relatively inefficient speakers (83 db/1w/1m), so I choose to go with a nice solid 200wpc amplifier. Obviously, if you're running highly efficient speakers, that might be overkill.
 
i have heard harbeths driven to perfection by mono-block amps putting out 75w rms into 8-ohms / 140w rms into 4-ohms

others here more knowledgeable might be able to correct me and certainly help out better, but it is my understanding that an associated consideration is the ability of an amp and its power distribution to sustain power delivery under "peak demand" circumstances such as loud transients.
 
bluegrassphile said:
Anyway, how much power is enough for most scenarios? I would think 75 wpc x 2 into 8 ohms would do the job, except, for loud transients. And that's what concerns me most regarding minimum power requirements...higher volume transients, compression and distortion. How much output power is enough to confidently cover them?
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Tom.......For well recorded music that has not been overly compressed during the mastering process it is not uncommon for dynamic peaks to rise 10dB above the average music level. With this in mind you must consider the typical average power you usually use when listening to music, be it 0.5 watts, 1 watt, 3 watts, etc. The Harbeth Super HL 5+ 40th Anniversary speakers have a sensitivity of 86dB/1W/1M. This means that 1 watt will deliver a comfortable average listening level, and that 10dB of dynamic headroom would require the amplifier to deliver slightly less that 10 watts to achieve approximately 96dB sound pressure for clean dynamic range. For every 3dB increase in volume the output power will double. If your typical music listening level with the Harbeth Super HL 5+ speakers is 92dB, then your power requirements will be in the range of 4 watts average, while 10dB peaks that create 102dB of sound pressure will need approximately 34 watts of reserve power. Using this information will allow you to figure out how much amplifier power you require to adequately accommodate your listening requirements.

There is nothing that says you cannot have more power than necessary to support your particular listening habits. It is always better to have more power than not enough, especially for the safety of your midrange and high frequency drivers. In my opinion, 75 watts to 100 watts per channel is a comfortable power level that will allow you to drive nearly any speaker to satisfying volume levels in small to medium sized rooms.
 
aKnyght said:
i have heard harbeths driven to perfection by mono-block amps putting out 75w rms into 8-ohms / 140w rms into 4-ohms

others here more knowledgeable might be able to correct me and certainly help out better, but it is my understanding that an associated consideration is the ability of an amp and its power distribution to sustain power delivery under "peak demand" circumstances such as loud transients.
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Yes, that's what I'm referring to..."peak demand circumstances." Enough power to cover almost any speaker at peak demand without any audible distortion. Speaking in generalities​, how much is enough for most speakers.
 
As has been stated, there are differences of opinions. For some people they can never have enough power. For others, such as myself, quality is the most important thing.

Dan's explanation above was very good and detailed, and I tend to agree with him. Quality power of 75-100 WPC is more than enough for me.

Obviously, your listening habits do come into play. I am not one that looks to knock the walls down... some people do listen at those levels :)...
 
MikeCh said:
300 to 500 watts per channel is more than enough for most loudspeakers.
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Yes, Mike, I would certainly agree with that, LOL! So would 1000 watts. But, again speaking in generalities, I'm just wondering what would be the minimum amount of output power you would want to have on tap for just about any speaker? Mike, you know more about this that I'll ever know. That's why I'm asking these questions of experienced and knowledgeable people on this forum such as you. I'm contemplating what the minimum power requirement might be for my Harbeth (6 ohm) speakers at higher volume? Would 125 wpc to 175 wpc x 2 into 6 ohms cover transient peaks with no audible distortion? Maybe it is indeed 300 wpc x 2 into 6 ohms? Most of the time I will not be playing my system at "higher volume levels". But I don't want to hear any distortion when I do. I'm guessing 100+ wpc might cover it. But with my lack of knowledge and experience I just don't know.
 
One thing to keep in mind. Some power amps handle transients better than others. For example - the 2 box Devialet has a lot of watts (1,000w) but it couldn't keep up with a Accuphase A-70 (60w). This was going into Raidho speakers.
 
tino27 said:
I would think that in addition to considering the load of the speakers in question (6 ohms in your case), the efficiency of the speaker would also help to determine how many watts per channel you'd also need in order to have enough headroom for transients. Personally, I have relatively inefficient speakers (83 db/1w/1m), so I choose to go with a nice solid 200wpc amplifier. Obviously, if you're running highly efficient speakers, that might be overkill.
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I like overkill. My main speakers are 92 dB sensitive 2-way monitors at 8 Ohm impedance, and I use an amp of 100W/ch into 8 Ohms (130 W/ch into 4 Ohms). The monitors can easily be driven with great dynamics by a 15 W/ch amp (have tried it). But with my current amp dynamics are even better.

My JL Audio subs each have an internal amp of 1800 W.

I would agree though with what has been pointed out, that high power does not guarantee great transient performance. Larger amps sometimes are more sluggish, so it all depends. Better judging with your ears rather than a rulebook.
 
There is more than Watts to be considered when designing a good amp. As Jock notes in Post 10 a relatively low power amp such as the A-70 might do a better job on some speakers than a significantly higher rated one. I found this when I moved from 1.2k's to the original Momentum's. Dan's amps were much better at controlling the difficult to drive MBL 111f'.

Then again there is Relentless. :P
 
Dan, that was great info and a very helpful post. Sincere thanks to you and everyone else on this thread. It sounds like 75 watts would indeed be adequate and perhaps a comfortable minimum for most situations. That's great to know and very timely since I will be visiting Suncoast Audio soon to decide on an amp to go with my Harbeths. There'll be a LOT of listening to do and I just wanted to make sure I pick something with enough power reserve to drive my speakers at about any volume level without distortion.

I know Suncoast owner, Mike Bovaird, will very competently guide me. But I'm just trying to get a feel for how much output power I'll need. I'm sure I won't be playing my system loud enough to require 300 wpc x 2 into 6 ohms. But I want to have enough of a margin to do the transients justice. OTOH, I don't want so much power that I could accidentally or otherwise fry speakers or an amp. I think the Harbeths are rated at 150 watts. Unless I'm under-powering or over-powering them they should be pretty safe. I might be very occasionally playing them somewhat loud...maybe about 30% to 45% on the volume control, max. Most of the time I'll be operating at maybe 25% to 30%. Anyway, I think you get what I'm talking about. I also think, with the info Dan presented here, and with the amps I'm considering, output power won't even be a factor.
 
bluegrassphile said:
Dan, that was great info and a very helpful post. Sincere thanks to you and everyone else on this thread. It sounds like 75 watts would indeed be adequate and perhaps a comfortable minimum for most situations. That's great to know and very timely since I will be visiting Suncoast Audio soon to decide on an amp to go with my Harbeths. There'll be a LOT of listening to do and I just wanted to make sure I pick something with enough power reserve to drive my speakers at about any volume level without distortion.

I know Suncoast owner, Mike Bovaird, will very competently guide me. But I'm just trying to get a feel for how much output power I'll need. I'm sure I won't be playing my system loud enough to require 300 wpc x 2 into 6 ohms. But I want to have enough of a margin to do the transients justice. OTOH, I don't want so much power that I could accidentally or otherwise fry speakers or an amp. I think the Harbeths are rated at 150 watts. Unless I'm under-powering or over-powering them they should be pretty safe. I might be very occasionally playing them somewhat loud...maybe about 30% to 45% on the volume control, max. Most of the time I'll be operating at maybe 25% to 30%. Anyway, I think you get what I'm talking about. I also think, with the info Dan presented here, and with the amps I'm considering, output power won't even be a factor.
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I've heard your speakers with mono block tube amplifiers of 24W in Class A.
The amps had tight grip on the Harbeths.
I think the example of the Accuphase above tells a lot: not the Watts count, it's the current an amp can produce.
 
My experience with amps is that wattage is not always the most appropriate way to judge an amp. I had a B&K amp years ago rated at about 220wpc. But I kept burning fuses and ribbons in my Maggie's. I replaced the amp with a high current amp from another manufacturer but similar wattage and the problem pretty much went away. That said, the interaction between the speaker and the amp may be more important that the wattage.
 
I found with 800/watts per channel I would occasionally have clipping. After upgrading to 1200/watts per channel I no longer have that issue. I did have to install a separate circuit for each amp to prevent the breaker from tripping when both amps were on one circuit. Now it is pure musical bliss.
 
It depends on the speakers. I’m experimenting with the B&W 800D3’s at the moment and they love power. I put the ARC REF160M’s on them and it sounded beautiful, but the REF6 was at 75 and the sound lacked dynamics. Switch to the Luxman M900u Monos (about 750 watts/ch in bridged mode) or the Gryphon Mephisto and WOW! They come to life.

The Bryston 28SST2’s would be excellent, Hegel H30 Monos, SimAudio monos. Constellation Taurus monos was good too.

Agree with Jock on the Devialet. I had the 400’s and it sounded like 40.


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