# Whats you take on power needs?



## rpearson (Jul 9, 2013)

I guess I should start by saying thank you to those who have continued to offer advice and information through all of my considerations and the indecision that come with making such decisions that one will live with as part of your HT for a long time.Thus far I decided to completely replace my pre-pro and amps. I also have added at the advice of you guys 4 of SVS’s - SBS-02’s two cover my RS, LS, RR and LR. These I just couldn’t pass on as such a value in sound for the money. 

So for reference my HT now consists of B&W 805’s for RF and LF and the B&W HTM2 matching center. As machined SVS’s doing all the rear stuff.
Irrelevant as it may be the only thing left in my rack at this point is a Monster AVS2000 power plant. 
So on to the new considerations. First off I’m all but sure that the Per-pro will be the Emotiva UMC200 unless something else is found more intriguing between now and time to buy.

The real obsessive decision that I am contemplating and need help with by way of a firm and decisive opinion is which amps to use. The difference one to the other seems to be a very subjective subject around here. There seems to be two schools of thought that I have noticed; one is enough power is enough and the other is no such thing as too much used responsibly.

Quire as it may seem I have heard both of these beliefs preached from layman and design engineer’s alike. The logic seems to be simple in explanation. 

•	If your speakers max wattage rating is 200 thin anything at or below within reason of this number is desirable. And gives you all the authority you will need to get all your speaker has to give running let’s say at ¾ + /- volume to reach cinema levels.

•	The never enough crowd argue that running say 600wpc into the same 200 max speaker offers much more control and response or vitality with all that is needed in power reserves if called on of course running responsible volume levels. So for instance I offer my system as an example, I am considering one of these three configurations to power the HT system I described above. 

(1) Qty. 1 each of Emotiva’s XPR-2 @ 600w x 2 @ 8ohms to power FR & FL and a XPR-5 @ 400w x 5 @ 8 ohms. to power the CC, RS, LS, RR and LR. 
(2) Qty. 1 each same configuration only with Emotiva’s XPA-2 Gen 2 @ 300w @ 2 @ 8 ohms and the XPA – 5 Gen. 2 @ 200w x 5 @ 8 ohms. 
(3)	The Sherbourn of which I know little PA-7X350 that offers 350w x 7 @ 8 ohms.

So what is your opinion or knowledge on the subject and what is your recommendation? Keep in mind that I do love the super cool look of the XPR offerings but have no desire of spending a lot more money for a minimal amount of improvement. 

I also should mention that it is very likely that I will be up grading my FR and FL speakers to B&W 804 towers in the near future.
Thanks for any input you might offer. REP


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## NBPk402 (Feb 21, 2012)

When you say max watt speaker rating... Do you mean max rms or peak? The advantage to having more power than your speakers are rated at is to provide clean power for your peaks. If your amp clips you can destroy your speakers. I say go with more power but use it wisely.


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## tonyvdb (Sep 5, 2007)

Under powered will cause distortion and damage but most speakers will reach reference levels with about 100watts of power that does not include the peaks. An amp thats rated to do 200watts will be able to do momentary peaks of twice that much so my point is that 200watts is plenty of power for almost any speaker out there.


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## fmw (Aug 11, 2013)

Not complicated. Assuming 805 matrix, the efficiency rating is 87 db. That means that, at a listening distance of 1 meter, the speaker will produce 87 db of sound pressure with 1 watt of power. 87 db is pretty loud - louder than I listen to be sure. Normally we like to to have about double the volume potential to handle peaks. That requires 10 times the power from the amp. So I would view 10 watts per channel to be a minimum requirement to play fairly loudly. If you want 90db at meter then you need 20 watts, 93 db would need 40 watts etc. I have tested my own system. I normally run about 1/2 watt playing jazz or classical music at a level that I would consider "live." The highest wattage I've seen is just shy of 20 watts on loud Blu-Ray movie passages. So anything more than 20 watts per channel is wasted for me.

I do use a powered subwoofer and that handles most of the power requirement, leaving my receiver with a fairly easy job to handle.

There is some input for you. I'll leave it up to you to decide how much power you need.


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## tonyvdb (Sep 5, 2007)

I dont know anyone who sits just one meter from the speakers. Room acoustics, furniture placement and other factors play much more into that number and make those kind of readings meaningless to a point.


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## rpearson (Jul 9, 2013)

fmw said:


> Not complicated. Assuming 805 matrix, the efficiency rating is 87 db. That means that, at a listening distance of 1 meter, the speaker will produce 87 db of sound pressure with 1 watt of power. 87 db is pretty loud - louder than I listen to be sure. Normally we like to to have about double the volume potential to handle peaks. That requires 10 times the power from the amp. So I would view 10 watts per channel to be a minimum requirement to play fairly loudly. If you want 90db at meter then you need 20 watts, 93 db would need 40 watts etc. I have tested my own system. I normally run about 1/2 watt playing jazz or classical music at a level that I would consider "live." The highest wattage I've seen is just shy of 20 watts on loud Blu-Ray movie passages. So anything more than 20 watts per channel is wasted for me.
> 
> I do use a powered subwoofer and that handles most of the power requirement, leaving my receiver with a fairly easy job to handle.
> 
> There is some input for you. I'll leave it up to you to decide how much power you need.


Thanks, my 805 are their Nautilus offerings. Your information is quite conservative compared to most. 
Thanks for the consideration.


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## fmw (Aug 11, 2013)

tonyvdb said:


> I dont know anyone who sits just one meter from the speakers. Room acoustics, furniture placement and other factors play much more into that number and make those kind of readings meaningless to a point.


You think my wattmeter is inaccurate?


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## fmw (Aug 11, 2013)

rpearson said:


> Thanks, my 805 are their Nautilus offerings. Your information is quite conservative compared to most.
> Thanks for the consideration.


Conservative in what way? I just explained how much power I use. I asked you to decide how much you need.


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## tonyvdb (Sep 5, 2007)

fmw said:


> You think my wattmeter is inaccurate?


Your not taking into consideration distance to the seating position, room acoustics, room size, speaker placement even altitude and humidity can effect the volume that reaches the seating position.


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## fmw (Aug 11, 2013)

tonyvdb said:


> Your not taking into consideration distance to the seating position, room acoustics, room size, speaker placement even altitude and humidity can effect the volume that reaches the seating position.


Of course it does. The wattmeter is at a speaker terminal. I, however, am seated comfortably on my sofa 800 feet above sea level with fairly low humidity in the summertime because the air conditioning is running. That is where I adjust the volume to my liking. It is also fairly dry in the winter thanks to forced air heating. I believe I made those measurements in the Winter when the air is dry. How much difference do you think I would have measured in Spring or Fall? Would the power consumption rise or fall?


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## tonyvdb (Sep 5, 2007)

The altitude and humidity make subtle differences but the other factors make huge differences. Your original post was at 1mtr distance. Either way your readings are flawed. Bottom line is 20 watts is not near enough power to run most speakers to reference levels at 80Hz-20kHz.


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## fmw (Aug 11, 2013)

My original post explained that I use 1/2 watt in normal listening and that the highest level I've measured in my system is just shy of 20 watts. My speakers have an efficiency rating of 88db which is fairly average and similar to that of the OP's speakers. 

I'm not sure what you view as a reference level but, on my system that would be zero DB on the receiver readout and that would drive me out of the 18X20 foot room. My listening distance, by the way, is 3.5 meters. Again I spoke about the power levels I use. I recommended the OP decide for himself how much power he needs. The great majority of audio people have an inflated concept of the amount of power they need and use. I was trying to ease the OP's concerns. Hopefully, I have eased yours as well. Happy listening.


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## rpearson (Jul 9, 2013)

fmw said:


> Conservative in what way? I just explained how much power I use. I asked you to decide how much you need.


Take no offence friend, I'm simply referring to your scientific approach and its verifiable information of which I found quite useful. Variables aside; I understand the benefit of taking the information that you provided and applying to my application in order to determine my need. :T
Many thanks.


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## fmw (Aug 11, 2013)

rpearson said:


> Take no offence friend, I'm simply referring to your scientific approach and its verifiable information of which I found quite useful. Variables aside; I understand the benefit of taking the information that you provided and applying to my application in order to determine my need. :T
> Many thanks.


I'm not offended. I'm just trying to be helpful. You were getting some information that wasn't really helpful in my view and I thought I would stick my nose into the thread. Much of the information in audio magazines and forums like these is based on common belief rather than facts. The manufacturers feed the misinformation like crazy. It is popular to take extreme situations and describe them as typical in the audio world when, in fact, they are extreme and unusual. There are extreme and unusual amplifier requirements in audio but yours isn't one of them.

My advice is to use amplifier power typical of what you would find in any modern AV receiver. It is more than enough for speakers like yours and overkill if you use a powered sub woofer. Anything more is just spending money for reasons unrelated to driving your speakers.


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## lcaillo (May 2, 2006)

Please be careful about making generalizations. If you believe manufacturers are providing misinformation, you have every right to that opinion and may state it. To be fair and most helpful, however, providing some specific examples not only inform others but it would support your perspective. 

Frankly, I have been involved in the audio and home theater business for over thirty years and never got the impression that amplifier manufacturers were overstating the need for power. I have made similar measurements to yours and concluded that somewhat more power is typically used in my case, but I tend to listen at lower levels than most. When you extend the modeling of expected power needed by considering levels at normal listening distances, many people may need more power than your typical AVR. Many won't. I don't, generally, but when I listen loud, it is nice to have more headroom.


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## nova (Apr 30, 2006)

You can place me in the control and response category. The Denon receiver always drove the speakers loud enough in all situations and all rooms but, once I added the Acurus amp I could really hear a difference in the bass.


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## fmw (Aug 11, 2013)

lcaillo said:


> Please be careful about making generalizations. If you believe manufacturers are providing misinformation, you have every right to that opinion and may state it. To be fair and most helpful, however, providing some specific examples not only inform others but it would support your perspective.
> 
> Frankly, I have been involved in the audio and home theater business for over thirty years and never got the impression that amplifier manufacturers were overstating the need for power. I have made similar measurements to yours and concluded that somewhat more power is typically used in my case, but I tend to listen at lower levels than most. When you extend the modeling of expected power needed by considering levels at normal listening distances, many people may need more power than your typical AVR. Many won't. I don't, generally, but when I listen loud, it is nice to have more headroom.


I'm surprised at that. I've been involved in audio for about 60 years and have seen nothing but an unending string of overstatements from all the manufacturers. Back in the 1950's, we were all content with 20 watt amps and those had plenty of headroom for a typical user. They were tube amps so there were a bit more forgiving if they were overdriven but they sure weren't very powerful. 

It wasn't until the 60's that everyone became enchanted with the concept of "100 watts per channel" and every manufacturer did eveything possible to hit the required price points while still delivering 100 watts - RMS, Peak, whatever. That didn't matter. It was the magic 3 digit number that mattered. We're still enchanted with it. 

I've seen novices say, that receiver doesn't even have 100 watts per channel. It has 80 and the difference between that and 100 is less than a single inaudible DB. What I suggested is that the OP's system was not for an auditorium and the speakers are not a challenging impedance load. The power available in any modern receiver would get the job done for him. That's just a fact. I stand by what I said.

I don't have a problem with people buying things they want and don't need. I just think that they should have a clear understanding of what the product will or will not do. I'm one of those people who has been seriously involved in bias controlled listening tests and, frankly, I bristle a little at many of the claims I read about and in the audio business. I tend to recommend against expensive wires and outboard DACs, for instance, which have no sound but are nevertheless popular with audiophiles. I don't care if they buy them. I just think they should understand what they are getting.

As an example, the post following yours claims that a Denon receiver drove his speakers competently but when he added an external amp, he heard more bass. If, indeed, he heard more bass then the Denon receiver did not drive his speakers competently. If he heard more bass without a bias controlled listening session then that extra bass may not have actually been there. Our brains tend to let us hear what we expect to hear. In order to get to what we can actually hear, we need to remove external influences and personal biases. 

I do have a tendency to attack misinformation in the audio world. It isn't meant for any other purpose than to help. If you don't want me to do that, just say so. It is your forum. I don't want to destabilize anything.


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## tonyvdb (Sep 5, 2007)

fmw said:


> I'm surprised at that. I've been involved in audio for about 60 years and have seen nothing but an unending string of overstatements from all the manufacturers. Back in the 1950's, we were all content with 20 watt amps and those had plenty of headroom for a typical user. They were tube amps so there were a bit more forgiving if they were overdriven but they sure weren't very powerful.


Agreed, but also keep in mind that that was in the days of analog only recordings with far less dynamic range and thus much less demand on the amps.


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## fmw (Aug 11, 2013)

tonyvdb said:


> Agreed, but also keep in mind that that was in the days of analog only recordings with far less dynamic range and thus much less demand on the amps.


Of course, but not enough to require 100 watts per channel to drive 8 ohm speakers of average sensitivity in a typical home theater, particularly with a powered sub handling the deep bass. As I said, I'm not against neat amplifiers, I just think people should know what they are buying and why. I have a 50 lb. 300 watt per channel (into 8 ohms) amplifier sitting in a closet because I don't need it in any of my three systems. I've even owned expensive tube gear in my less experienced days.


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## lcaillo (May 2, 2006)

fmw said:


> I do have a tendency to attack misinformation in the audio world. It isn't meant for any other purpose than to help. If you don't want me to do that, just say so. It is your forum. I don't want to destabilize anything.


If the facts destabilize something then so be it. I just don't see manufacturers making the case for high powered amps. The do sell greater power as a feature assumed to be of value, and the ratings do not always correspond to useful output, but I don't see them, in general, pushing the need for extremely large amps. Just produce some quotes from ads to justify your statement.

Now salespeople often do sell up to higher power than users need. Also, many people do need very large amps. Some do expect rather inefficient speakers to produce very loud sound. I have seen many people drive their receivers to clipping or to shutdown and need more power. You would be in the minority in feeling that 20 watts will do. I can assure you after many years in sales, service, and installation, that I had far fewer complaints from users that they had too much power than the reverse.


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## nova (Apr 30, 2006)

I did not hear "more" bass with the addition of the amp. I hear tighter more defined bass. I would also say that loud enough and competently are not one and the same. The speakers are not an easy load to drive but then not really a difficult load either with a Frequency Response of 27Hz-20kHz (±3dB), Sensitivity 88dB (2.83V @ 1 Meter) and 4 Ohms Impedance. Of course I would not rule out any biases and I may think I hear what I want to hear. In the end I am very happy with my current setup and that all that really matters to me.


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## fmw (Aug 11, 2013)

nova said:


> I did not hear "more" bass with the addition of the amp. I hear tighter more defined bass. I would also say that loud enough and competently are not one and the same. The speakers are not an easy load to drive but then not really a difficult load either with a Frequency Response of 27Hz-20kHz (±3dB), Sensitivity 88dB (2.83V @ 1 Meter) and 4 Ohms Impedance. Of course I would not rule out any biases and I may think I hear what I want to hear. In the end I am very happy with my current setup and that all that really matters to me.


It is all that should matter to anyone. It is recreation after all.


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## chashint (Jan 12, 2011)

For the math to hold up for SPL vs distance you have to make the measurements outdoors or in a anechoic chamber.

In a typical room there's much less SPL loss for distance or for the picky room reflection offsets SPL loss.

I too think most people (including myself) use significantly less amplifier power than they think they do.

In this thread there is person posting that has actually measured the wattage at the speaker terminals and correlated that to SPL at the listening position.

Unless someone else wants to do that measurement and refute his numbers any further discussion is simply speculation or nitpicking. 

For no particularly good reason I want my amplifier section to be minimally rated below 0.1% distortion @ 100w RMS into 8 ohms. 
I probably never use more than 10-20 Watts max, but mentally 100 is my number.

I am not real hung up on the all channels driven spec either....real world material is not a steady tone nor is it ever applied to multiple channels simultaneously.

I think people should get what they want or at least get something that does not create lingering doubts.

For me I would rather have a top tier AVR instead of an entry level separates system....but that's just me.

If the choice was between a top tier separates system and an AVR I would want the separates but still buy the AVR because I am not made out of money. 

Does the existing electric service e support going all in on amplification?
Do you have to consider how much will it cost to run multiple dedicated 20 amp circuits? 
Will you need a bigger breaker box or a higher service rated box?
Is the service line to the home adequate? 

My vote is for a very good AVR and call it good.


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## bkeeler10 (Mar 26, 2008)

Yeah this is what I kept thinking as I was reading through this -- a guy has actual measured data and he knows how much power it takes to drive his system to the levels he wants to listen to.

On the other hand, one must remember that to get an additional 3 dB of output (which is a noticeable but subtle increase in volume) requires twice the power. To get a 10 dB increase in output (which our ears perceive subjectively as a doubling of volume) requires 10 times the power. Which means that power requirements for those who truly like to listen at reference (not me!) can quickly get out of hand. 

fmw said that the highest power he has seen going to his speakers is 20 watts. Let's assume that fmw listens to his blu rays at 15 dB below reference level and he requires 20 watts of clean power to do so at the peaks. Since you don't want to ever ask the amp to deliver max output, he would be wise to have a solid 40 watts of power on tap to do that. 

Now suppose the OP likes to listen much louder -- subjectively twice as loud. That would be 5 dB below reference which is 10 dB louder than fmw listens. His power requirements are an order of magnitude higher (10 times higher) than fmw's. That's 200 watts at the peak, in which case you'd want to have 300 - 400 watts of capability in your amp. (This is all assuming a similar room size and acoustical absorption and listening distance and speaker sensitivity).

It's worth noting because even though those of us who listen at sane levels (IMHO) do not need much power (only a handful of watts), power requirements quickly (exponentially) increase for those who really like to listen loud.


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## tonyvdb (Sep 5, 2007)

chashint said:


> For the math to hold up for SPL vs distance you have to make the measurements outdoors or in a anechoic chamber.
> 
> In a typical room there's much less SPL loss for distance or for the picky room reflection offsets SPL loss.


Although outside or in a chamber is going to yield true readings I dont agree that room acoustics will have less of an effect on SPL output. You would be surprised as to how much a sofa or carpet or a well treated room will absorb/block sound. 
I did an test of my own EVs (that are 97db efficient) last night. If I sit 1 meter from the speaker and play pink noise at 75db my Samson servo 600 amps meters (300watts per ch) are showing a signal of -18db if I move back to my listening position at 12ft I have to increase the volume that shows to almost 0db on the meters to reach that same 75db level on my SPL meter.


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## chashint (Jan 12, 2011)

bkeeler10 said:


> On the other hand, one must remember that to get an additional 3 dB of output (which is a noticeable but subtle increase in volume) requires twice the power. To get a 10 dB increase in output (which our ears perceive subjectively as a doubling of volume) requires 10 times the power. Which means that power requirements for those who truly like to listen at reference (not me!) can quickly get out of hand.


Agreed with entire post...

If SPL is very important more can be accomplished with selecting high efficiency speakers than throwing more power at it.

I think there is often times a desire to justify what is "wanted" by "needing" it....Absolutely nothing wrong with that, I have "needed" so many of my toys it is silly....There's also the opposite where lacking the funds to get what is "wanted" leads to selecting something less costly and justifying it with "not needing" it....Been there & done that too....

In the end the OP should get what he/she wants tempered by what's affordable.


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