• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Power Amp Questions

I used the Crown Audio calculator and it came up with 20 watts for normal listening and 300 watts for when I want to make some serious noise, so my Schiit Tyrs are perfect for my system (200W @8 ohms /350W @ 4 ohms, my speakers are 8 ohm but dip down to 3.1 ohms).
 
Dan13105 said:
This is why your speakers determine what you need. This is what is power is required to get unclipped signal, with 2 of my sets of speakers, at THX spec level of 85Db with 105Db peaks. The first speaker is my very efficient Infinity SM150 View attachment 3232530
Only 18W, not bad. Just about any receiver can drive them being they're 8 ohms as well. Now let's look at my Acoustat Spectra 1100 electrostats that are much harder to drive at only 86Db sensitivity, and impedance that dips to 1.1 Ohms

View attachment 3232532
Wow, 715W! Quite the difference in power requirement. Let's try a more average speaker spec of a Pioneer S-T300 that is 6 Ohms and 88Db sensitivity.

View attachment 3232534


Still 451W required. But notice how just a 2Db change in sensitivity requires 264W less. This is why there is no simple answer to how many watts one needs or can use. If you listen louder or quieter, closer or farther, or use more or less sensitive speakers, all drastically affect the power requirements. This is why I use Crown's amp calculator on their site. When I was shopping for my Acoustats, I knew I needed an amp that could handle occasional 1 Ohm loads, and high current capacity. I bought a very capable amp that came from a THX theater. IT truly doubles down on power when impedance halves from 300W at 8Ohms , to 600W at 4 Ohms, and it still isn't powerful enough for true THX levels with my electrostats. Try the calculator out, you may find you need way more or less than you thought
Click to expand...
Interesting. Thanks for this resource. I’ll be using it for sure.
 
BMWCCA said:
Of course not!
Here in America they buy $100,000 SUVs with 500-hp to do that. :crazy:
Click to expand...

True for a portion of the population, but not everyone owns (or thinks they need) one.
I assume they also use it for other things, so at times the engine is loafing and other times it's not.
 
My impression is that the reason for higher power isn't just the peak power available, its when the typically class AB design shifts from class A to class B. A is usually thought to sound better, and more powerful amps make the switch at higher power levels, so most of the time you are listening in class A. But the OP has a class A amp, and with efficient speakers (such as the JBLs) there may be no advantage to more AB power.
 
Class AB is bias based for transition from A to B or A to A/B and higher power does not equal higher class A wattage.
Some amplifiers are high bias, many are not.
 
Last edited:
opnly bafld said:
True for a portion of the population, but not everyone owns (or thinks they need) one.
I assume they also use it for other things, so at times the engine is loafing and other times it's not.
Click to expand...
I have a 485 HP Dodge Charger which sits in the garage 9/10 of the time (piss poor gas mileage). We usually drive the wife's 300HP V-6 Dodge Charger- it got 36mpg on our trip to Durango last week. I have a 300WPC @8ohm/ 500WPC @4 ohm Parasound A21+ used sparing in the office- it probably never uses more than 25 watts.
 
opnly bafld said:
True for a portion of the population, but not everyone owns (or thinks they need) one.
I assume they also use it for other things, so at times the engine is loafing and other times it's not.
Click to expand...
And not everyone owns Hi-Fi speakers the size of a desk, either. But plenty here do!

Cars are like amplifiers: Horsepower costs money. How fast do you want to go? :beerchug:
 
Nat said:
My impression is that the reason for higher power isn't just the peak power available, its when the typically class AB design shifts from class A to class B. A is usually thought to sound better, and more powerful amps make the switch at higher power levels, so most of the time you are listening in class A. But the OP has a class A amp, and with efficient speakers (such as the JBLs) there may be no advantage to more AB power.
Click to expand...

This is always dangerous turf but here goes ..

It's about dynamics and transient attack, not just SPL's and decibels ..

If you had a 2wpc amp and a 20wpc amp, they both sound about the same when they're almost inaudible at a level that can't even overcome the background noise ..
As soon as the volume is increased to a an audible level that overcomes the background, they will sound very different from each other ..
The 20wpc amp will be richer, fuller and more realistic .. truer fidelity to the music ..the bass is evident, notes and instruments will be more easily identifiable

The reason for that change is dynamics .. the ability of the amp to quickly and accurately reproduce the instantaneous peaks in the music ..
The 2wpc amp is truncating the peaks .. that truncates subtle transient detail.

So it is about peak power ability ..
Not necessarily just the sonic differences between Class A and Class B which can often be pretty subtle ..

A car crash and a gunshot can have the same SPL but they certainly don't sound the same .. that transient detail is important stuff ..
 
Last edited:
I think I got it.
If my system ever makes Led Zeppelin :thumbsup: sound like the Beatles :thumbsdown: I will know my system is missing the transient detail :rolleyes: and I need to get something better fast or just take everything to recycling.
 
Akustic said:
This is always dangerous turf but here goes ..

It's about dynamics and transient attack, not just SPL's and decibels ..

If you had a 2wpc amp and a 20wpc amp, they both sound about the same when they're almost inaudible at a level that can't even overcome the background noise ..
As soon as the volume is increased to a an audible level that overcomes the background, they will sound very different from each other ..
The 20wpc amp will be richer, fuller and more realistic .. truer fidelity to the music ..the bass is evident, notes and instruments will be more easily identifiable

The reason for that change is dynamics .. the ability of the amp to quickly and accurately reproduce the instantaneous peaks in the music ..
The 2wpc amp is truncating the peaks .. that truncates subtle transient detail.

So it is about peak power ability ..
Not necessarily just the sonic differences between Class A and Class B which can often be pretty subtle ..

A car crash and a gunshot can have the same SPL but they certainly don't sound the same .. that transient detail is important stuff ..
Click to expand...
Thank you Akustic! I was reading this thread and hoping someone would jump in with this message. I'm glad you did.

To the OP, I once thought I had an opportunity to get a pair of Klipschorns. Well, to my disappointment, they turned out to be Cornwall 1s. I renegotiated the price and they came home with me. All 108 lbs each!

Once I got them into the house, they were huge. With some reorganizing we got them placed, and I made a deal with my wife. I told her lets try them out for two weeks, and if you don't like them, I will sell them. Well, I am selling them, but this is 10 years later! After a week, my wife told me these speakers are keepers! She only agreed to let them go when I bought a pair of Kef 107s that were going to go into the critical listening room. They are here now in the living room, and the Cornwalls have been listed. In the end, they didn't take up much more space than the Kef Concertos that were in that place before. Another excellent sounding pair of vintage speakers. Very under priced and under the radar. But they need big short solid stands to sound their best.

Honestly, I would try and talk your wife into trying out the Forte.

You may not need all that extra power, but your bass will thank you if you feed it with all it wants. I rarely went over 18 watts with my Cornwalls. But they sounded better on my McIntosh MC-2205 than they did with my McIntosh MA-6200 for amplifier power using the C26 for preamp for its sound signature.

You might ask why if all it is is 18 watts of power? Both amps have ample supply of that. But it really isn't about power. It is about current. Power only gives a part of the story. It is instantaneous current availability that prevents deep transients from swallowing up your highs. And those Cornwalls have 15 inch woofers. When the dynamics get crazy, the control of the woofer is crucial. I really notice the differences between the two amps if I played Avril Lavigne SK8TR BOI or BTO's Not Fragile. The quality of the bass is unmistakeable on the MC-2205.
 
El Gato said:
So, I usually find an answer to my questions here Fairly quick, but with all the posts about power amps I still don't see any answers. Close...but yet so far.
Ok. I have a Luxman L-550AXII integrated amp, Class A @ 20 watts P/channel. I have a pair of Klipsch Heresy IV's hooked up to them. The Heresy's are most likely getting moved to another room. A lot of the replacement speakers I'm looking at do not have the efficiency that the Klipsch possess. I'm thinking I may need a decent power amp between the Luxman and the new speakers in order to boost wattage if the efficiency is too low for 20 watts.
If that's the case, is the end result wattage pre amp + power amp or whichever amp has the highest wattage?
Is the resulting sound dominated by the pre or power amp or combination of both?
If I'm going about this problem wrong, let me know why. Any recommendations, advice or opinions? Thank you.

James
Click to expand...
Hi James,
20 watts is not very much, especially if it is peak output. Depending on the music you enjoy listening to, it may very well be enough, if your new speakers have reasonably high efficiency, say 90db or so. Amplifier power is all about "control" of the speaker, especially the bass. If your preference is for ruckus metal and hard rock, like mine, 20 watts will definitely not be enough. If you enjoy chamber music and classical (great with a Class A amp) instead of Sabaton and Deep Purple, then 20 watts may be all that you need. I am not familiar with the Luxman 550, but are you sure you can actually hook a power amp to it and it has the appropriate pre-outs? :)
 
opnly bafled: I believe that the transistors that can handle high power typically can transition from A to B at higher power, and typically are. But I'm sure you are right that not all do.
 
Dan13105 said:
This is why your speakers determine what you need. This is what is power is required to get unclipped signal, with 2 of my sets of speakers, at THX spec level of 85Db with 105Db peaks. The first speaker is my very efficient Infinity SM150 View attachment 3232530
Only 18W, not bad. Just about any receiver can drive them being they're 8 ohms as well. Now let's look at my Acoustat Spectra 1100 electrostats that are much harder to drive at only 86Db sensitivity, and impedance that dips to 1.1 Ohms

View attachment 3232532
Wow, 715W! Quite the difference in power requirement. Let's try a more average speaker spec of a Pioneer S-T300 that is 6 Ohms and 88Db sensitivity.

View attachment 3232534


Still 451W required. But notice how just a 2Db change in sensitivity requires 264W less. This is why there is no simple answer to how many watts one needs or can use. If you listen louder or quieter, closer or farther, or use more or less sensitive speakers, all drastically affect the power requirements. This is why I use Crown's amp calculator on their site. When I was shopping for my Acoustats, I knew I needed an amp that could handle occasional 1 Ohm loads, and high current capacity. I bought a very capable amp that came from a THX theater. IT truly doubles down on power when impedance halves from 300W at 8Ohms , to 600W at 4 Ohms, and it still isn't powerful enough for true THX levels with my electrostats. Try the calculator out, you may find you need way more or less than you thought
Click to expand...
What really costs power is bass hits. It depends on what you are listening to, as to how much power you really need. I do agree that the efficiency of the speakers is a critical parameter.
 
You must log in or register to reply here.
Back
Top Bottom