Stereo Receivers

[Razor]

Quote:

Originally Posted by sailor I think you might be a victim of creative marketing. Assuming both receivers have same speakers (let's say sensitivity 90dB / 1W /1m for easy calculations) and you could really get the indicated power levels into the speakers, the 25W would provide loudness of 103.9 dB of and 100W would get 110 dB. While these levels would be distinguishable from one another, I would hardly call it "an extreme difference".

I am talking from experience. To fill up a good size hall with sound a 25watt/ch stereo will not do the job, but a 100watt/channel will. The difference between 100db and 110db is actually quite a bit. An increase of 10 db is a tenfold increase in sound.
There is a huge difference in a car stereo with 20 watts/channel and one with 100 watts/channel. I know, I upgraded the unit in my Corvette and now can only turn the volume up half way without discomfort.
In normal listening 25 watts/channel is fine but there definitely is a difference between 100 and 25.

[Texas Proud]

Quote:

Originally Posted by Razor I am talking from experience. To fill up a good size hall with sound a 25watt/ch stereo will not do the job, but a 100watt/channel will. The difference between 100db and 110db is actually quite a bit. An increase of 10 db is a tenfold increase in sound. There is a huge difference in a car stereo with 20 watts/channel and one with 100 watts/channel. I know, I upgraded the unit in my Corvette and now can only turn the volume up half way without discomfort. In normal listening 25 watts/channel is fine but there definitely is a difference between 100 and 25.

Most of the watts are used in bass.... the highs just don't take that much...

AND, you are probably using only 1 or 2 watts when listening to music unless you wish to blast away.... so the difference in 25 and 100 is mostly marketing... as long as everything else is the same...

Now, having said that... usually 25 watt systems are made with a lot more distortion than 100... but not always... as I said, a tube system would blow away your 100 watt system in sound quality and driver ability...

Someone tell me... IIRC, a doubling of watts only produce 3 db more sound... so would it not only be 6 db louder? not 10?

[sailor]

Quote:

Originally Posted by Razor I am talking from experience. To fill up a good size hall with sound a 25watt/ch stereo will not do the job, but a 100watt/channel will. The difference between 100db and 110db is actually quite a bit. An increase of 10 db is a tenfold increase in sound. There is a huge difference in a car stereo with 20 watts/channel and one with 100 watts/channel. I know, I upgraded the unit in my Corvette and now can only turn the volume up half way without discomfort. In normal listening 25 watts/channel is fine but there definitely is a difference between 100 and 25.

LOL
I think you might be a victim of creative marketing
1. Would you consider Carnegie Hall a good size? It can be easily "filled up" with 25W of power available. Imagine a "cheap consumer grade" Klipschhorn driven with 25W and we are talking about 118 dB at 1m
2. 110 minus 103.9 is 6.1, not 10.
3. Have you wondered why such logarithmic scale was introduced for measuring the loudness? Based on workings of the human ear/brain system. So while 110 dB sound will be 10 times more powerful (in absolute values i.e. W/sq m) than 100 dB sound but the ear does not perceive it as that much of a difference.
4. Have you verified manufacturers claims for 20W/channel and 100W/channel? I did measure several car stereos and about 2/3 of them did not measured up. The only visible benefit to me for higher power amps were typically lower THD at the moderate and high volume levels (>10W). Since I never use it this way it's worth nothing to me. OTOH you might need it in your Vette.
FWIW I use 50 mW/channel on my commute and around 1W/channel on my boat for normal listening.

[sailor]

Hmm, I guess I should learn how to do multiple quotes

Quote:

Originally Posted by Texas Proud Someone tell me... IIRC, a doubling of watts only produce 3 db more sound... so would it not only be 6 db louder? not 10?

Yes. For example look here: Decibel - Wikipedia, the free encyclopedia

[Razor]

Definition and examples

The decibel (dB) is used to measure sound level, but it is also widely used in electronics, signals and communication. The dB is a logarithmic unit used to describe a ratio. The ratio may be power, sound pressure, voltage or intensity or several other things. Later on we relate dB to the phon and the sone (units related to loudness). But first, to get a taste for logarithmic units, let's look at some numbers. (If you have forgotten, go to What is a logarithm?)

For instance, suppose we have two loudspeakers, the first playing a sound with power P1, and another playing a louder version of the same sound with power P2, but everything else (how far away, frequency) kept the same.
The difference in decibels between the two is defined to be

10 log (P2/P1) dB where the log is to base 10.

If the second produces twice as much power than the first, the difference in dB is

10 log (P2/P1) = 10 log 2 = 3 dB.

If the second had 10 times the power of the first, the difference in dB would be

10 log (P2/P1)= 10 log 10 = 10 dB.

If the second had a million times the power of the first, the difference in dB would be

10 log (P2/P1) = 10 log 1000000 = 60 dB.

[Razor]

Quote:

Originally Posted by sailor LOL I think you might be a victim of creative marketing 1. Would you consider Carnegie Hall a good size? It can be easily "filled up" with 25W of power available. Imagine a "cheap consumer grade" Klipschhorn driven with 25W and we are talking about 118 dB at 1m 2. 110 minus 103.9 is 6.1, not 10. 3. Have you wondered why such logarithmic scale was introduced for measuring the loudness? Based on workings of the human ear/brain system. So while 110 dB sound will be 10 times more powerful (in absolute values i.e. W/sq m) than 100 dB sound but the ear does not perceive it as that much of a difference. 4. Have you verified manufacturers claims for 20W/channel and 100W/channel? I did measure several car stereos and about 2/3 of them did not measured up. The only visible benefit to me for higher power amps were typically lower THD at the moderate and high volume levels (>10W). Since I never use it this way it's worth nothing to me. OTOH you might need it in your Vette. FWIW I use 50 mW/channel on my commute and around 1W/channel on my boat for normal listening.

Back in college we had some huge outdoor parties and the high watt amps would blow away the entry level 25 watt units. Watts is about loudness and lack of distortion at high levels.
You must have never heard some of those high watt car stereos. There is a huge difference in volume.
I have had a half dozen amps in my life and I guarentee you the 500 watt units would blow away the 100. You could hook the largest speakers in the world up to a 25 watts and the loudness would not compare.

[Texas Proud]

Quote:

Originally Posted by sailor LOL 2. 110 minus 103.9 is 6.1, not 10.

DOH.....

Thanks... at least it is what I was thinking...

[free4now]

I used to consider myself an audiophile, but I did enough blind listening tests to discover that most of the things "audiophiles" obsess over are not audible.

Amplifiers operating below their clipping levels all sound the same these days. In fact there is an unclaimed $10,000 prize for anyone who can hear such differences:

Richard Clark Amplifier Challenge FAQ

However, DACs (the digital to analog converters inside receivers that convert digital signals from toslink optical connections to analog) do sound different, and the lower quality ones can definitely be picked out on a high end system. The difference is minor, and much less than the differences between say mp3 encoders. So unless you have very high end speakers it's not worth worrying about.

I strongly agree with the advice to shop receivers for features and reliability not sound quality. AV switching and surround decoding are the features that most people care about. I haven't bought a new receiver since I bought one of the first dolby digital receivers (with outboard decoder) 12 years ago. Whenever a new type of video connection appears (e.g. S-Video, component, VGA, HDMI) I buy an outboard switcher box for $100-200 rather than spending $1000 on a new receiver.

If you aren't going to be switching video just buy whatever seems easiest to use.

[mathjak107]

Quote:

Originally Posted by Razor I disagree. If you hook 2 recievers to speakers that can handle 200 watts. One reciever has 25 watts/channel and the other has 100 watts/channel there will be an extreme difference in loudness in the two when cranked up. Been there done that. Best done outside though. Car stereos with 15 watts/ch do not compare with those with 100watts/channel. to

ABSOULETLY NOT TRUE! there is far more interaction going on then power. theres dynamic headroom which is far more important, theres speaker efficiancy and most important is the amplifiers ability to deal with low impedence loads and complex speaker loads. . more ofton than not current falls off drastically in poorer designs to the point of barly having much output at low impedences or impedences approaching 1 ohm at times. i can guarantee you i can take some well designed 25 watt amps with 3 to 6db dynamic headroom , my 25 watt bedini i used to have and blow away the typical 100 watt receiver power amp

[mathjak107]

Quote:

Originally Posted by Razor I am talking from experience. To fill up a good size hall with sound a 25watt/ch stereo will not do the job, but a 100watt/channel will. The difference between 100db and 110db is actually quite a bit. An increase of 10 db is a tenfold increase in sound. There is a huge difference in a car stereo with 20 watts/channel and one with 100 watts/channel. I know, I upgraded the unit in my Corvette and now can only turn the volume up half way without discomfort. In normal listening 25 watts/channel is fine but there definitely is a difference between 100 and 25.

ever here 10 watts into a klipsch design speaker? its deafining

[mathjak107]

you have to understand a loudspeaker isnt like an 8 ohm test resistor. a loudspeaker depending on design, volume and frequency has an impediance curve that can vary all over the place.

a speaker being an inductive load generates a current that flows back up stream to the amplifier just as if it was a lil generator as it moves in and out.

its that back emf that creates havic and takes a 300 watt behemouth and makes it barely squeaks out 10 watts at times , even shutting down to protect itself . i have tested some huge amplifiers that could barely put out any current into high impedence loads or low impedence loads. they werent even capable of 10% there rating at times.

[free4now]

If you listen to music loud you MIGHT find 25WPC too little. I've heard the difference between 100WPC and 25WPC, and there's no question 100WPC sounds cleaner when driving a speaker that handles high power at high power. But in the end it doesn't really matter, since these days nearly all receivers have at least 60WPC, which is enough for nearly all speakers at normal listening levels.

[Razor]

Are you still trying to say a amp with 100 total watts(25 per channel) is just as loud as a amp with 500 total watts(100 per channel) with the same speakers?

[mathjak107]

again depends on the current output and dynamic headroom in each design. i can tell you my 25 watt bedeni plays cleaner at loud levels than a 300 watt pioneer sx1980 i had owned

[mathjak107]

picture this, when a speaker load is complex it causes current and voltage to become disjointed. the current lags behind the voltage and has to fight its way thru.
take a 300 watt amplifier and lets make the numbers easy to use. 300 watts into a test resister would be 10 volt at 30 amp.

now when going to a loudspeaker which is inductive and not resistive the voltage may be at 10 volt but the current remember is lagging . its fighting its way passed that back current coming back up stream. it may hit a point of 2 amp while the voltage is peaking. thats a 20 watt output from your 300 watt behemouth. the better the amplifeir design the closer to behaving as if it was feeding a test resister the amplifier gets. some huge amps under actual loads fall apart and distort at very low outputs as there voltage peaks but current is very low and shouldnt be

[Texas Proud]

Quote:

Originally Posted by Razor Are you still trying to say a amp with 100 total watts(25 per channel) is just as loud as a amp with 500 total watts(100 per channel) with the same speakers?

No.... what we are trying to say is that at almost all listening levels there is no difference....

I have an OLD Pioneer receiver that has 35 watts.. you hook it up to a pair of speakers and crank it up and you can not be in that room long...

I have also hooked up a '100 watts' per channel surround sound receiver to the same speakers and it would clip... could not drive them at high levels... shocked the heck out of me that I could not even get close to the level that I could with my ordinary stereo receiver without the sound dropping out...

NOW, the advantage of the extra power (and this I am pulling out of the dark recesses of my brain, so if I am remember it wrong.... you are warned!!!)... is that if there is a low impedance speaker and there is a bass note.. and you do not have enough power to produce that note, it goes up an octave or two or something with a lot of power... and that is how you blow out speakers... (again... I am sure some engineer will tell the REAL story, but this is my memory)

SO, having extra power is good protection for your speakers, but as for loud.... I have not met anyone who can run an amp at full volume for very long... so it does not matter in the end...

[mathjak107]

now lets talk about another important aspect DYNAMIC HEADROOM

see in order to gert a power rating an amplifier according to the ftc has to play a continious test tone for 30 minutes or so and not exceed its rated distortion level when tested into a test resister of 8 ohms.

now picture an amplifier with a lot less continuos power so it cant go 30 minutes straight but picture a design like carver , hafler , sun etc that when allowed to breath for a millisecond and recharge the power supply that amplifier is capable of double or triple its rating with absolutly no increase in distortion. thats dynamic headroom. some amps have 6 db dynamic headroom thats an amazing amount of current avail for music while keeping the rating of the amplifier at a far lower rating by ftc standards

at one of the audio shows nad had an exhibit called guess the power. it was amazing as we all guessed 75 watts, 100 watts ,150 watts. well it was all of 20 watts. a high current ,feed any load design that blew the audio world away.

ask any audiophile about the nad 2030 reciever. it was a rude awakening that power didnt matter. like a porche with bald tires, its all about coupling that power to your speaker



ever watch a lesser designed high power amplifier try to drive a pair of electrostatic speakers which are a highly capacitive load? once again its all about getting that power to where it matters. the little quick silver amps will blow away most high power designs in getting that power translated to sound

[free4now]

Quote:

Originally Posted by mathjak107 picture this, when a speaker load is complex it causes current and voltage to become disjointed. the current lags behind the voltage and has to fight its way thru. take a 300 watt amplifier and lets make the numbers easy to use. 300 watts into a test resister would be 10 volt at 30 amp. now when going to a loudspeaker which is inductive and not resistive the voltage may be at 10 volt but the current remember is lagging . its fighting its way passed that back current coming back up stream. it may hit a point of 2 amp while the voltage is peaking. thats a 20 watt output from your 300 watt behemouth. the better the amplifeir design the closer to behaving as if it was feeding a test resister the amplifier gets. some huge amps under actual loads fall apart and distort at very low outputs as there voltage peaks but current is very low and shouldnt be

Like all audiophile debates, this is probably getting out of hand but I can't resist continuing

Mathjak, while you are technically correct that some amplifiers are capable of supplying more current than others with the same rating, in actual practice it's of little consequence. The custom built speakers I am listening to right now are biamped, meaning I have separate amplifiers for the tweeters and the woofers, partially because the simpler loads don't exhibit the problem you describe with the inductive loads of crossovers causing some power to be wasted. I know where you are coming from.

But after studying this stuff a while I realized that this effect can't suck more than about 5-15% or so out of the amplifier power, nowhere near the 20W vs 300W that your example implies. In fact there could very well be instants when the inductive load "pushes" back more current than the amplifier can supply, giving you a negative current flow between the crossover and amp when you wanted positive 10A. But we are saved by the fact that audio is an AC waveform and inductive loads can only push back what they have stored from the amplifier power itself. The effect you described can only happen at one part of the waveform, not over the whole waveform.

And so called "high current" amplifiers are really just normal amplifiers that are underrated and whose voltage-producing abilities may be crippled. They are designed that way because rich audiophiles believe that they are better, not because they actually drive normal speaker better.

The one exception is extremely low impedance loads like say a 1 ohm subwoofer driver, but I think it's safe to say that the OP isn't planning anything exotic like that.

[free4now]

Quote:

Originally Posted by mathjak107 now lets talk about another important aspect DYNAMIC HEADROOM see in order to gert a power rating an amplifier according to the ftc has to play a continious test tone for 30 minutes or so and not exceed its rated distortion level when tested into a test resister of 8 ohms. now picture an amplifier with a lot less continuos power so it cant go 30 minutes straight but picture a design like carver , hafler , sun etc that when allowed to breath for a millisecond and recharge the power supply that amplifier is capable of double or triple its rating with absolutly no increase in distortion. thats dynamic headroom. some amps have 6 db dynamic headroom thats an amazing amount of current avail for music while keeping the rating of the amplifier at a far lower rating by ftc standards at one of the audio shows nad had an exhibit called guess the power. it was amazing as we all guessed 75 watts, 100 watts ,150 watts. well it was all of 20 watts. a high current ,feed any load design that blew the audio world away. ask any audiophile about the nad 2030 reciever. it was a rude awakening that power didnt matter. like a porche with bald tires, its all about coupling that power to your speaker ever watch a lesser designed high power amplifier try to drive a pair of electrostatic speakers which are a highly capacitive load? once again its all about getting that power to where it matters. the little quick silver amps will blow away most high power designs in getting that power translated to sound

Yet another case of selling the spec to audiophiles who are buying that spec. Sure you can make an amplifier that will produce transients equivalent to 100 Watts but is only rated at 20 Watts. It's easy in fact... just take a normal cheapo 100 Watt amplifer and remove the heatsink so it overheats when it produces more than 20 Watts continuously. Then you can sell the crippled amplifer to people who get excited about DYNAMIC HEADROOM for several times what it would otherwise be worth.

[mathjak107]

not exactley what dynamic head room is. try removing a heat sink and see what happens. (poof)... dynamic headroom is a very popular way of building many well designed amplifiers. it has nothing to do with cheapness, it has to do with heat, and the overall sound of running a class "a" amplifier which is fully biased all the time and has absolutley no switching distortion . typical high power amps run in an a/b fashion.

the solid state devices wait until they see a signal and then turn on usually causing a distortion called switching distortion in a/b amplifiers. a class "a" amplifier is fully biased and on full all the time. the gourgous sound of a 25 watt bedini is magical. however the heat is horrible, you can actually cook an egg on mine.

so take an amplifier and now derate it by keeping rail voltages much lower but pack in huge power supplys and run it in class "a" mode with the ability to generate huge amounts of output when needed and thats the idea behind an amp with a large dynamic headroom. these amps are far from cheap,
Sound and Vision Magazine - The Amplifier Power Ratings Game