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What does more watts per channel get you?


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19 replies to this topic

#1 of 20 RobWil

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Posted March 24 2003 - 01:45 PM

Well the server search is currently disabled so I'll ask something that's prolly been asked many times.

All things being equal, what does more power get you in terms of 2-channel music listening?
Given the same set-up and the choice between 65WPC and 85WPC using large, efficient, full range speakers.
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#2 of 20 Craig_Kg

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Posted March 24 2003 - 01:46 PM

bragging rights
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#3 of 20 Steve Schaffer

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Posted March 24 2003 - 01:55 PM

For 2 channel music with efficient speakers I doubt that you'd hear any difference at all between 65 and 85 wpc.

Power difficiency is, I think, much more of a factor when driving 5 to 7 speakers during a demanding passage in an action/adventure movie.

Most receivers are much more likely to meet or exceed their rated power at a nice low distortion level when driving 2 channels for music than when driving a full HT speaker array.

Back in the 80s I got great room-filling sound with 2 channel stereo receivers rated at only 35 wpc. driving fairly efficient full-range speakers with 10 or 12 inch woofers.
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#4 of 20 RobWil

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Posted March 24 2003 - 02:31 PM

Thanks for the replies, although Steve's was slightly more informational Posted Image
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#5 of 20 Kevin. W

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Posted March 24 2003 - 03:30 PM

For every 3db increase you need to double the wattage. Lets say your speakers were rated 89db/1w/1m sensitivity.

eg:

1watt/1meter: 89db
2watt/1meter: 92db
.
.
16watt/1meter: 101db
.
.
etc

Wattage is not the only factor when looking at equipment. SNR, slew rate, THD, #/type/size output devices and capacitors, etc

Kevin

#6 of 20 RobWil

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Posted March 24 2003 - 06:21 PM

Hmmm... that's a little technical for me, but I kind of get your point. But in terms of sound quality, bass tightness, sonic ambiences, etc. instead of in terms of just 'loudness' would there be even a slight difference given a good ear.
To be more specific, I'm trying to decide between an HK AVR 520 (85x2, 75x5) and an AVR 320 (65x2, 55x5) w/ Klipsch KG5.2's (sensitivity 96db@1W/1m) in a fairly small room and I think I hear a slight difference in favor of the AVR 520 but I don't know if it's because I'm trying to justify it or if it's actually real.
So basically they are identical in terms of SNR, THD, etc....the only difference is in the power.
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#7 of 20 Craig_Kg

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Posted March 24 2003 - 06:41 PM

Sorry for being facetious.

All the above posts are true and also, an amp's power rating into a particular load is fairly meaningless as it does not show how the maximum output varies with load (basically a function of the power supply capacity and rail voltage).

For most receiver ratings, power is limited by the normal rail voltage as they measure the output into a test load with only one or two channels driven. Given that P=V*V/R and that the peak voltage for a sine wave is sqrt(2) greater than the RMS value, it isn't hard to calculate the rail voltage and also calculate the POTENTIAL power output for different loads. The reason I use the word potential is that, as the power supply is loaded, it will tend to saturate and it's output voltage will drop and so the rail voltage will drop. Very few (if any) receivers have power supplies that don't sag when all channels are loaded.

This is why some brands (eg HK, NAD, Rotel), which measure power output with all channels driven, seem to have low power ratings relative to similar costing receivers from other brands.

Also, if the load impedance is less than that at which the receiver's power rating was measured, the power supply will saturate even earlier (since the lower impedance requires more current flow to maintain the same voltage).
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#8 of 20 Chu Gai

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Posted March 24 2003 - 07:52 PM

if you're going to focus on the power as the decision maker, then you'll have to find a way to dig up some technical reviews of the two receivers to find out how they're actually delivering on their stated claims. the klipsch are pretty sensitive and don't need much to drive them to levels that'll ruin your hearing and get the cops to pay you a visit at 11 pm at night.

#9 of 20 Andy Kramer

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Posted March 25 2003 - 12:58 AM

An interesting point aside, I have found (through my late nights at my local tweeters) thats the more watts per channel the clearer and more rich sound is. There is just more power to handle the spectrum of sound. Dont know if there is any truth to this but i have heard a difference. But when i noted the difference the range was more of 50 wpc to 100 wpc. Hope that might help give some insight.
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#10 of 20 BrentPollard

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Posted March 25 2003 - 12:59 AM

"First you get da power, then you get da wattage then you gat de women.Posted Image

#11 of 20 Rick_Brown

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Posted March 25 2003 - 01:07 AM

More watts gets you more "headroom", i.e., more power to handle peaks in the sound without distorting.

#12 of 20 Paul Clarke

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Posted March 25 2003 - 09:41 AM

Quote:
To be more specific, I'm trying to decide between an HK AVR 520 (85x2, 75x5) and an AVR 320 (65x2, 55x5) w/ Klipsch KG5.2's (sensitivity 96db@1W/1m) in a fairly small room and I think I hear a slight difference in favor of the AVR 520 but I don't know if it's because I'm trying to justify it or if it's actually real.


Rob,

Correct me if I'm wrong but are you using CD play to listen for differences? The 520 has HDCD but I believe the 320 does not. This could also play a role in the slight difference you think you notice, whether or not the CD may be HDCD encoded or not.

I have both the 310 and the 510 and have run exhaustive comparison tests on both models. There is a +1.25->1.33dB edge to the 510 as you might expect when using their internal amps. The sound quality and frequency response measurements are very close when they are tested as pre/pros with a very slight edge in the high treble to the 310 out of these two samples. I prefer using the 510 as pre/pro in my system however for two reasons: the Main Ins allow great flexibility in powering speaker setups when using external amps...and the HDCD which I do not have in any of my players.

It currently is paired with a Parasound 855A passive bi-amp configuration driving 4 88dB, 6 Ohm towers and a 6 Ohm CC in a 17x12 room.
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#13 of 20 RobWil

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Posted March 25 2003 - 11:51 AM

Thank you for the responses guys Posted Image
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#14 of 20 RobWil

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Posted March 25 2003 - 11:56 AM

Paul....I'm using the analog audio output on my CD. Funny but it seemed to sound best.

"COLOR=blue]I have both the 310 and the 510 and have run exhaustive comparison tests on both models. [/color]"

I hear ya! Exhaustive is definitely the word!

"The sound quality and frequency response measurements are very close when they are tested as pre/pros with a very slight edge in the high treble to the 310 out of these two samples."

Hmmm...surprising!

"First you get da power, then you get da wattage then you gat de women."

Naw....I'm too old for women....I'll take the power and the wattage any day!
that's my story and I'm stickin' to it!

#15 of 20 Paul Clarke

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Posted March 25 2003 - 05:12 PM

Rob,

I hear you back. Sometimes it seems there's no end to the decision process. Posted Image In my case, the slight differences in measured response overall favored the 510...especially in the mids. Lows were equivalent and the highs were only marginally better with the 310.

Without hearing each sample, I would suspect the 520 should be the better choice. Your speak's are very sensitive but the HCC +/- 45amps, the Main Ins and the HDCD are a killer package.

BTW, I also generally prefer the analog path and run mirror connections to the 6 channel direct for simplicity in setup with the towers when running subless. The analog in this system seems more detailed...especially in the mids and highs...digital sounds smoother but slightly rolled off/compressed. Of course HDCD CD's are a different story. There the digi path shines.

Good Luck in choosing.
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#16 of 20 RobWil

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Posted March 25 2003 - 06:24 PM

""The analog in this system seems more detailed...especially in the mids and highs...digital sounds smoother but slightly rolled off/compressed.""

Wow!....that is exactly what I have found but didn't really know how to describe it. The digital did sound smoother, the analog maybe slightly on the bright side but a fuller, more expanded sounding soundstage with sharper highs. The bass was comparable.
Anyway, after switching back and forth a couple more times tonite I decided to go with the 320...I think it's more compatible with my high efficiency speakers. At best I would attach an amp to go 6.1 or 7.1 and I'm not too sure HDCD is going to become a standard. Besides the analog sounds so good I don't see myself switching just for HDCD.
But then again, I've never listened to HDCD!....and....the great thing about this is you can always upgrade later! Posted Image
Anyway...thanks for the input! Cheers!
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#17 of 20 Kevin. W

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Posted March 26 2003 - 01:20 AM

Quote:
More watts gets you more "headroom", i.e., more power to handle peaks in the sound without distorting


Rick, wouldn't it be the storage capacity in the reciever that offers the headroom? Wouldn't a reciever with 50w/100,000uf capacitors storage vs 100w/30,000uf have more headroom for those peaks?

Kevin

#18 of 20 Philip Hamm

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Posted March 26 2003 - 03:43 AM

Low bass takes a lot more power to reproduce than higher frequencies. For most of our systems our mains are only being driven from 80Hz (or even higher) up, seriously reducing the amount of power that the amp needs to deliver to produce a nice clean signal.

So somebody who owns a decent sub, with say a 135wpc 5 channel 70lb behemoth of a dedicated amplifier driving small efficient bookshelf speakers is seriously in the overkill zone.







...But that doesn't mean I don't like it. Posted Image


By the same token, if you're driving large full-range speakers, you need gobs of power to pump ou that low bass.
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#19 of 20 RobWil

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Posted March 26 2003 - 04:57 AM

Yeah....I have an Infinity IL120S on the way so I'm anxious to see the difference in the mains once they no longer have to handle 80Hz and below.
In my case I think even going with the HK520 w/ 85wpc(with the high-current design is actually more like 110wpc)is overkill for my extremely efficient speakers (although they definitely wouldn't be considered small!). They're actually only rated at 100wpc RMS, 500w peak I believe.
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#20 of 20 Rick_Brown

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Posted March 26 2003 - 05:57 AM

Quote:
Rick, wouldn't it be the storage capacity in the reciever that offers the headroom? Wouldn't a reciever with 50w/100,000uf capacitors storage vs 100w/30,000uf have more headroom for those peaks?


Kevin, I'm sorry but I don't have enough technical knowledge to answer your question. I was giving RobWil a simple rule of thumb in answer to his question, all else being equal. Cheers!





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