Power, how much do you really need ?

steve f · « **on:** 21 Mar 2012, 03:43 am »

An audiophile friend of mine died recently. I brought home some of his stuff with the intent of helping his widow sell his collection.
I placed a Mac 150 power in my system instead of one of my tube amps. (we are talking 150wpc vs. 1.5 or 25wpc) I was amazed watching the meters, by how little power I actually use for my normal listening. Most of the time, I used about a 1/4wpc with peaks of only 1-2wpc. Once again Roger's ideas about amp size is proven. My speakers are efficient at 95 db. So why the horsepower race?

Steve

mjosef · « **Reply #1 on:** 21 Mar 2012, 03:52 am »

Not everyone has 95dB speakers. Speakers @ under 90dB need those 100+s-watt amps.
My speakers are just around 90dB, and I can get by with 40W tube/125W SS...but a 250W SS amp brings another quality to the table.

*Scotty* · « **Reply #2 on:** 21 Mar 2012, 05:48 am »

I would say first off, don't believe the meters on the Mac 150 they are mechanical meters and will not be particularly accurate when it comes to measuring instantaneous peak power demands. You could easily be using as much as ten times the power on peaks that you are using on a long term average basis.
That being said you still may not be using more than 25 watts on a peak basis, it depends on your room and the material you are listening to. I have speakers with similar sensitivity of around 95 or 96 dB. While I have never heard my amp clip my system does see double duty reproducing the audio when we watch DVDs so it has the potential to actually need the 108 watts/8 ohms that I have on tap when the explosions happen.
Scotty

Rclark · « **Reply #3 on:** 21 Mar 2012, 06:22 am »

Well I have Maggies, and in their current state (nice pun, huh?), they bring my 87 watt amp to its knees when pushed hard. And my amp is on batteries and it's a very beefy 87 watts.

How much power do I really need? I'll let you know when I have 400 watt monoblocks.

Ericus Rex · « **Reply #4 on:** 21 Mar 2012, 03:47 pm »

Quote from: mjosef on 21 Mar 2012, 03:52 am

Not everyone has 95dB speakers. Speakers @ under 90dB need those 100+s-watt amps.

Since 3db of volume gain requires roughly double the power if you use a 92db efficient speaker and listen to music the same level as Steve you'd still use only 1/2 watt most of the time with 2-4 watt transients. 89db speakers would be 1 watt with 4-8 watt transients. 86 db = 2/8-16 watts etc. Unless you listen to REALLY LOUD MUSIC you should be just fine if you double the transient peak; i.e. 32 watt amp into 86db cone speakers would work just fine for most listeners. My 40 watt tube amp into 90 db cone speakers will shake the foundation of my house.

Panel speakers are a different beast altogether. I certainly would recommend megawatt SS amps for planars and electrostats.

Devil Doc · « **Reply #5 on:** 21 Mar 2012, 04:08 pm »

There's no such thing as too much power. Too little power will get you in trouble every time. IMO, of course. 8

Doc,

medium jim · « **Reply #6 on:** 21 Mar 2012, 04:31 pm »

Ericus:

Planar speakers sound wonderful with tube amplification! I have no problem with only 70wpc of tube driving a pair of magnepan 2.5's that are rated at 83db. I do have a pair of subs taking a lot of the grunt work.

I also have a BGW 500D amp that in 4ohm is over 400wpc, I like the tube's better. Granted the SS amp is louder, but not by much.

Jim

rbwalt · « **Reply #7 on:** 22 Mar 2012, 01:50 pm »

i bet the tube amp really has to work hard driving the 2.5's. how many hrs do you get out those output tubes?

steve f · « **Reply #8 on:** 22 Mar 2012, 11:15 pm »

We must remember that there are a lot of factors in the load a speaker presents to an amp. I've been playing around with both tiny tube amps (a class A OTL) to amps of over 250 wpc (transistor, just the thought of buying a couple dozen output tubes scares me.) My speakers are a benign 8 ohm load. Your milage will vary. I'm still amazed, and yes I took better measurements than a meter face on an old Mac, how low the average power requirements at moderate listening really are. For my use, I love the OTL tone wise, but I suspect twenty really great watts would be just about perfect for my listening habits. My speakers can easily play at live rock band levels, but I must be getting old. I don't like to crank it up much anymore.

Steve.

Ericus Rex · « **Reply #9 on:** 23 Mar 2012, 01:13 am »

Save up your pennies, Steve. Roger is working on a low power OTL. No idea when it will come to light though.

rpf · « **Reply #10 on:** 23 Mar 2012, 01:42 am »

Quote from: Ericus Rex on 21 Mar 2012, 03:47 pm

Since 3db of volume gain requires roughly double the power if you use a 92db efficient speaker and listen to music the same level as Steve you'd still use only 1/2 watt most of the time with 2-4 watt transients. 89db speakers would be 1 watt with 4-8 watt transients. 86 db = 2/8-16 watts etc. Unless you listen to REALLY LOUD MUSIC you should be just fine if you double the transient peak; i.e. 32 watt amp into 86db cone speakers would work just fine for most listeners. My 40 watt tube amp into 90 db cone speakers will shake the foundation of my house.

Panel speakers are a different beast altogether. I certainly would recommend megawatt SS amps for planars and electrostats.

I've had a different experience. I have 87db efficient speakers with a relatively easy impedance curve. They are a nominal 8 ohm and drop, at their lowest, to 3.9 ohms. I was told that a 60 wpc tube amp would drive them well but I always felt - after several tube amps of 50-70 wpc - they were lacking drive and dynamic impact. I don't listen particularly loudly but it's not about that. All of these amps would play loud enough but just didn't have the dynamics and drive to be fully enjoyable. It took 90-100 tube wpc to make the speakers come alive.

jhm731 · « **Reply #11 on:** 23 Mar 2012, 02:04 am »

I also have speakers that are rated at 87db efficient. My 32 watt Leben CS600 drives them just fine, but when I hooked up a 900 watt Magtech things got really interesting.

rpf · « **Reply #12 on:** 23 Mar 2012, 02:13 am »

I should have also noted that I have had a 40 wpc amp in my system that sounded more powerful than a 55 wpc one and a 90 wpc amp that sounded more powerful than both a 100 and a 120 wpc one (all tubed).

So power ratings have to be taken with a grain of salt also.

Ericus Rex · « **Reply #13 on:** 24 Mar 2012, 01:10 pm »

Quote from: rpf on 23 Mar 2012, 01:42 am

I've had a different experience. I have 87db efficient speakers with a relatively easy impedance curve. They are a nominal 8 ohm and drop, at their lowest, to 3.9 ohms. I was told that a 60 wpc tube amp would drive them well but I always felt - after several tube amps of 50-70 wpc - they were lacking drive and dynamic impact. I don't listen particularly loudly but it's not about that. All of these amps would play loud enough but just didn't have the dynamics and drive to be fully enjoyable. It took 90-100 tube wpc to make the speakers come alive.

I also have a 90 watt tube amp that sounds more dynamic and powerful than my 40 watter. But I've never considered the sonic differences to be purely b/c its higher wattage. The 90 watter is far more expensive and has a more compicated circuit, as well as having a much larger power supply. So I'm more inclined to say the difference is due to the more sophisticated design of the 90 watter. I suspect most 40 watt amps are considered 'budget' designs by the manufacturer so the circuits are simpler and parts may not be of as high a quality. Conducting a true A/B comparison between a low and high watt amp may actually be near impossible.

mfsoa · « **Reply #14 on:** 24 Mar 2012, 01:17 pm »

From the Roger Sanders interview on Dagogo:

Quote

As an aside, I continue to be amazed by the fact that most audiophiles are not aware that they are using underpowered amplifiers that are clipping and distorting most of the time. It is easy to show that most speakers need around 400-500 W/channel to play dynamic music at the loud levels audiophiles enjoy. If you doubt this, just connect an oscilloscope to your speakers and watch it. You will see the trace run into an invisible "brick wall" when the amplifier runs out of power and clips. In most systems, you will see the amplifier clipping constantly on musical peaks.

opnly bafld · « **Reply #15 on:** 24 Mar 2012, 01:47 pm »

A quote from Tom Danley on another forum in a thread about the need for high power amps:

"For me this happened when I had a chance to be in an official ABX listening test of a number of amplifiers. I brought in my trusty Threshold stasis as my known reference and used speakers I had designed at work and had at home as well.

There was plenty of time and I went through a number of my reference CD’s to find a few passages that brought out the differences best and then went to “without knowledge” listening. At this point one could still hear some differences between them but they generally fell into two groups which I could reliably hear. What I heard were differences in the decay part of the sound which I have no explanation for (I used to build amplifiers too).

A funny and unexpected thing also happened which is why I am writing, in comparing the various pro-amps to my Threshold, I found that one group and it were indistinguishable except the Threshold began to sound “less dynamic” as I increased the level. AS the Thresholds VU led scale showed the peaks were -20dB or so down, I was puzzled. Connecting an oscilloscope to the output revealed the truth.

At a point WAY below one could hear it as a “flaw”, at a point that indicator showed peaks as 1/100th rated power, there was instantaneous voltage clipping.
To be very clear, this WAS NOT audible at all as a flaw or heaven forbid the familiar “clipping” the only clue was that compared to a much larger amplifier, the Threshold was somehow less dynamic above a modest level.

At that point, I switched to a larger pro-sound amplifier at home too. Currently my upper speakers (SH-50’s) are about 100dB 1w1m and I use an 800W/ch power amp on these above 80Hz.
With any commercial recording or movie soundtrack, this is more than enough headroom to never breathe hard but I can still reach instantaneous limiting with the fireworks recording.

Anyway, the big and unrealized advantage of having more power is that the short voltage clipping events reduce the dynamics long before it’s audible as a flaw. This can be seen (when present) by using an oscilloscope to examine the Voltage waveform going to the loudspeaker.

To be clear, just as a subwoofers job is to extend the response and that is not the same as “turning up the bass”, this IS NOT the same as “cranking it up” although a larger amplifier lets you do that too if your speakers are up to it.. This is about reproducing the peaks (in the “good” recordings) which are often clipped off much more often than people realize."

A quote from me: "

I still love my low power tube amps.

"

Lin

dflee · « **Reply #16 on:** 24 Mar 2012, 02:20 pm »

Is the Threshold Stasis a high current amp?

Ericus Rex · « **Reply #17 on:** 24 Mar 2012, 05:51 pm »

I hope Roger chimes in on this topic soon.

I'd also like his opinion on that paper (was it a paper? or just an article in a hobby mag?) by the scientist who claimed you had to have a 3,000 watt system to accurately reproduce a full orchestra. If that is true then my 40 watt amp (at almost 1/100th the recommended wattage) should sound absolutely horrible and unrealistic...but it doesn't!

steve f · « **Reply #18 on:** 25 Mar 2012, 02:35 pm »

I hope Roger joins this thread too.

Freo-1 · « **Reply #19 on:** 25 Mar 2012, 02:53 pm »

Quote from: dflee on 24 Mar 2012, 02:20 pm

Is the Threshold Stasis a high current amp?

Yes. The amount of current depends on which model (Stasis 1, 2, or 3). I used to own a Stasis 2 and a Stasis 3. The Stasis 2 was 200 wpc, and the Stasis 3 was 100 wpc.