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homeskizzle

How much power is really needed?

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Another thing that people don't think about when buying an am is... Amps are designed to run at a certain power (as an example say arbitrarily 2/3 of max), when you buy a large amp, and are say at 1/3 power you are listening to your amp at a higher distortion than if you had an amp that was matched better to your setup.

How much distortion are we talking about? I didn't realize this was an issue. They don't seem to make external low power home theater amps though. You get a 5-7 channel amp and it's nearly always going to be 125-200 watts per channel. Even with inefficient speakers and playing at pretty high levels you're not going to constantly be running it at 2/3 power.

 

A friend of mine works for a Company that designs and builds amps and he told me I should have went with smaller amps because of the efficiency of my speakers.  My bass bins are running around 1 watt on peaks with a 250wpc amp, and my horns are in the less than 100th of a watt with my 25wpc amps. One of the advantages of horns is low distortion and I hate to see that advantage go to waste by adding distortion back by getting too big of an amp. I too looked for low power amps for multiple channels and couldn't find any... I am assuming that they are not out there because most people do not have that efficient of a speaker, and people think more power is better.

 

Is he a designer?  An engineer?

 

I don't know, but I've heard that some amps have significantly higher distortion at very low output, and others don't.   Some early solid state amps (late '60s) had that reputation.  A few amp manuals have distortion graphs (e.g., my old Luxman).  I've also heard that THD+Noise graphs can be misleading.  I would hate to give up headroom.  I'm more or less in the dark about this.

 

I don't know if my friend is a engineer or not... All I know is he has worked at there for about 25 years and helped in the design and building of their amps as well as repair other brands.

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The question about transients.

 

I seem to recall that historically it was thought that transients on live music were about 18 dB above the average.  This article say 20 dB.

 

http://en.wikipedia.org/wiki/Audio_power

 

I expect that the percussion section was responsible for that.

 

There are a couple of implications.

 

We have to dig out the Klipsch papers about the big demo systems Bell Labs set up but I think that 0 dB reference on the line was indeed about 18 dB below the max for the system.   And these days with digital of honest to gosh recordings without compression, the average on a system should be 20 dB below any big peak.

 

As far as playback on speakers, it seems that PWK got it right. 

 

80 dB average is pretty loud.  At least an 80 dB test tone is about as loud as you'd like on a test tone.  Try it with a test tone and an RS meter and you'll see what I mean.

 

So 100 dB transients (that extra 20 dB) brings us up to the 1-watt level of a K-Horn at 1 meter and with two K-Horns and some extra distance at 104 dB actual sensitivity we'll call it even.

 

When he quipped that the world needs a good 5-watt amp, that was really just some headroom.

 

WMcD

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the average on a system should be 20 dB below any big peak.
 

 

That is pretty much the cinema standard.  THX, Audyssey (and others) require 105 dB maximum level from each of their main speakers (and 115 dB maximum for the subwoofer channel).  The 105 dB is just 20 dB above their band limited (500 to 2K) pink noise test signal which is adjusted to 85 dB.  Some confusion arises from Audyssey lowering their test "pings" from 85 dB to 75 dB, for the home, because of customer complaints about the loudness of the "pings."  Audyssey still has our HTs max out at 105 for each main (115 dB sub).  It's dificult to talk about an "average" with classical music, or movie music, because they are so varied,  but, in my experience toting SPL meters to orchestra rehersal (and standing about 5 rows back) 85 dB is loudish, and ff might be 100/105dB ... but ... higher happens.  PWK thought that a good sound system that would bring you the "blood stirring" levels of a symphony orchestra should be able to produce "115 dB at your ears."  He would have known, given his experience recording symphony orcestras.  I think he probably was referring to very brief peaks.

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I think the question at hand is "How much reserve power is required"?  Reserve power INMHO is much more of a factor in a speakers performance than the number of watts being thrown at it.  Reserve power gives you the headroom required for difficult passages or loads.  I run a 250 WPC Channel power amp which provides close to a 100,000 PUF of storage power capacity.  Strictly 2 channel setup with forte II.  A good quality SS amp with 200 WPC + will not provide any more distortion than a 40 WPC amp. Most preamps will muddy the waters more than an amplifire.

 

Best regards,

John

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This is a hotly debated topic in HT circles, and shows up here about annually.

 

My approach to this is entirely practical. Meaning, I really have a hard time lusting after that Bulter Audio 5150 or Krell power amp when my Fluke (which can capture a single impulse peak at up to 4 kHz) is clearly indicating that even my paltry, little 65W Panny has 12 dB still on tap while the La Scala are dishing out an F5 tornado in the living room

 

The fully horn-loaded crew get to work this discussion from an entirely different angle....while eating our ice cream of course. Power is simply not the issue. 

 

If a power amp is to surpass my current AVR in sound quality, it'll be not because of more headroom, but rather that it can do something else differently upstream. I don't discount the possibility of something sounding better one bit, but at this point the addition of discrete channel EQ, better filters, and time alignment would yield more profound improvements to my sound than simply an additional 3-4 dB of headroom.

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This is a hotly debated topic in HT circles, and shows up here about annually.

My approach to this is entirely practical. Meaning, I really have a hard time lusting after that Bulter Audio 5150 or Krell power amp when my Fluke (which can capture a single impulse peak at up to 4 kHz) is clearly indicating that even my paltry, little 65W Panny has 12 dB still on tap while the La Scala are dishing out an F5 tornado in the living room

The fully horn-loaded crew get to work this discussion from an entirely different angle....while eating our ice cream of course. Power is simply not the issue.

If a power amp is to surpass my current AVR in sound quality, it'll be not because of more headroom, but rather that it can do something else differently upstream. I don't discount the pohssibility of something sounding better one bit, but at this point the addition of discrete channel EQ, better filters, and time alignment would yield more profound improvements to my sound than simply an additional 3-4 dB of headroom.

When talking power Horn speakers compared to conventional speakers are like comparing motorcycles to cars. 120HP motorcycle is hard to hold onto but pathetic in an SUV.

VRDs in Penta mode, 60w channel, is more than required at 9 feet - if 1 watt for 104dB at 3 feet, 9 watts are required at 9 feet. Throw in a few watts for headroom there you go. PWK only need 5 watts for music since at the time recording was limited to 80dB range and he was listening to classical not watching Transformers.

Speaker placement, wall location, wall rigidty and materials are biggest factors in sound quality. If room is not correct shape, walls are flimsy getting good sound without room correction is impossible.

Edited by BE36

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On 3/4/2015 at 7:22 PM, Ron E said:

Correct me if I am wrong please, Power consumption long term would be less, correct?

 

Yes, it would be less.

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On 3/4/2015 at 5:15 PM, homeskizzle said:

If I get my hands on some solid extension cords, I'll hook up my Sherbourn 7X150 amp and report my findings. So far, my sound quality is outstanding IMO, but who knows - maybe the Sherbourn "outboard" will make a difference. Heck - at my current power usage rate, I could put it on the same breaker for shiggles.

 

However, I'll admit this - I'm jaded to thinking that in my current room and setup, I don't need an external amp. For me, letting my HK3600 do the grunt work, I get more than enough punch and power to my La Scalas. Maybe if I moved to a much larger room then I would benefit from external amplification. I mean - I have 3 La Scalas sitting (at the max) 7.5 feet from me. 

 

Enjoying the discussion! I'm always eager to learn and hear from others! 

 

If you're looking for heavy duty extension cords, look for air conditioning or block heater cords.  Or go to Home Depot or the like and get 14 or 12-gauge construction type cords.  They're not that much more expensive, and are much safer.

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On 3/3/2015 at 7:10 PM, derrickdj1 said:

For me, Idel or -80 on the avr has a system usage of 121 watts.  If I go to -30 I use around 121 watts, lol.  Horn speakers are pretty sweet on the power demands.  121 watts include the TV, BDP, power console, two I Nuke amp, power amp and avr.  If I ran all speakers as large it would go up a wee bit.

 

If you're including the TV, that's where most of the power is going.  They use a lot of juice!  The clue is the power cord.  If the TV power cord looks like it came off a heater, you know the TV likes the juice.

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On 3/4/2015 at 11:19 AM, Ron E said:

 

Big amps are made for outdoor use or with low efficiency speakers... Not for high efficiency speakers used in your home.

 

Once you find out the amount of power you are using stick an Scope on their and see how much distortion your big amp is putting out for running at such a low power output. .. You will see that you are running your amp at the highest distortion since you are running your amp at a lower level than it is optimized for. Get an amp that puts out the amount of power you really need and you will have less distortion then running too big of an amp..

 

There are power amps, and there are power amps.  Pro amps, which can seem tempting, because they're pretty cheap in terms of watt per dollar, are not usually the best choice for home listening.  This is because they're designed to run at near max power most of the time.  Accordingly, this is where they have less distortion, and maybe less noise as well.

 

Home audio amps are quite different, in that they're designed and optimized to sound clean at typical home volume levels, which are much lower than concert levels.  For example, the Yamaha MX-D1 dual-mono power amps that I use to power my JubScala IIs can put out 500 watts per channel.  Their lowest distortion range is from 6 to 10 watts, and most listening with Klipsch Pro or Heritage speakers (or combinations thereof) require less than that most of the time.  This means clean sound at typical listening levels, and massive headroom whenever it's called for.

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Our 65" 4k tv sucks power big time. I checked my rack the other day, and with 3 power amps, preamp, MiniPC, Dune player, and NAS... power consumption was 198w. TV is way more.

 

Sent from my SM-T550 using Tapatalk

 

 

 

 

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