How much is enough power? - AVS Forum
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post #1 of 11 Old 09-22-2012, 07:43 AM - Thread Starter
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I am evaluating whether it is better to go the route of an AV receiver, for example, Denon 4520, or the route of pre pro, like Marantz AV 7701 plus external amp, like Marantz MM 7055 or Parasound Halo A52. The focus of this particular thread is on the amp included in the AV receiver or in the dedicated amp.

The Denon literature indicates that it has 9 channels X 150 watts. The Marantz and Parasound amps offer 5 channels X 140 (Marantz) and 125 (Parasound) watts.

Question 1.

Are these numbers an apples to apples comparison. If all channels are driven for the Denon, Marantz and Parasound units, will they result in the 150, 140 and 125 watt amounts noted or will they result in a much lower number?

Question 2.

My rudimentary understanding is that in order to double the sound volume, you will need to increase the watts by a factor of 10. So if you want to hear something twice as loud at 10 watts, you would need a 100 watt amp. If this is the case, then I assume that the difference between a 150, 140 and 125 watt amp, is not that significant. Correct???

Question 3.

What are the other key factors, I need to consider in evaluating amps?

- speakers that will be used
- total harmonic distortion
- build quality
- music vs home theater use
- amp class (i.e. A, A/B, etc)
- cost
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post #2 of 11 Old 09-22-2012, 08:04 AM
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Quote:
Originally Posted by deeda View Post

I am evaluating whether it is better to go the route of an AV receiver, for example, Denon 4520, or the route of pre pro, like Marantz AV 7701 plus external amp, like Marantz MM 7055 or Parasound Halo A52. The focus of this particular thread is on the amp included in the AV receiver or in the dedicated amp.
The Denon literature indicates that it has 9 channels X 150 watts. The Marantz and Parasound amps offer 5 channels X 140 (Marantz) and 125 (Parasound) watts.
Question 1.
Are these numbers an apples to apples comparison. If all channels are driven for the Denon, Marantz and Parasound units, will they result in the 150, 140 and 125 watt amounts noted or will they result in a much lower number?
Question 2.
My rudimentary understanding is that in order to double the sound volume, you will need to increase the watts by a factor of 10. So if you want to hear something twice as loud at 10 watts, you would need a 100 watt amp. If this is the case, then I assume that the difference between a 150, 140 and 125 watt amp, is not that significant. Correct???
Question 3.
What are the other key factors, I need to consider in evaluating amps?
- speakers that will be used
- total harmonic distortion
- build quality
- music vs home theater use
- amp class (i.e. A, A/B, etc)
- cost

Id say there is no way the Denon actually puts out 150 per channel, Im sure that measurement is two channels driven. That's how most AVR's list it...it probably more like 90 watts all channels driven. The caliber of the amp makes the difference, along with room size, speaker efficiency and your ears! I was using an Outlaw pre/pro and Outlaw 7700(200x7) amp in a large room(20x38) for years and it sounded great. I moved and my room is now 15x20. I got rid of the amp and went with an Anthem MRX 500 receiver....100 watts rated but only 75 watts all channels driven and it sounds great! I tried a few other receivers and they didn't sound as good. I would see if you can do in home demo's with your own speakers.
If I were to choose one of the amps mentioned it would be the Halo by far! Buts thats just my opinion.....
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post #3 of 11 Old 09-22-2012, 08:21 AM
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Quote:
Originally Posted by vkowalski1970 View Post

Id say there is no way the Denon actually puts out 150 per channel, Im sure that measurement is two channels driven. That's how most AVR's list it...it probably more like 90 watts all channels driven. The caliber of the amp makes the difference, along with room size, speaker efficiency and your ears! I was using an Outlaw pre/pro and Outlaw 7700(200x7) amp in a large room(20x38) for years and it sounded great. I moved and my room is now 15x20. I got rid of the amp and went with an Anthem MRX 500 receiver....100 watts rated but only 75 watts all channels driven and it sounds great! I tried a few other receivers and they didn't sound as good. I would see if you can do in home demo's with your own speakers.
If I were to choose one of the amps mentioned it would be the Halo by far! Buts thats just my opinion.....
+1

Also the speaker to listener distance is important
http://electronics.howstuffworks.com/how-to-explain-speaker-sensitivity.htm
So first decide:
1/ which speakers, what's the sensitivity of them, are they 8 ohm or 4 ohm (tougher)
2/ distance to MLP and room size
3/ max preference SPL

Also in almost every AVR the power specs are for 1ch drivven, not two. So, from one to nine channels one can about divide the spec by three... On Audioholics, the AVR usualy sometimes goes into safety when they try to measure seven channels, let alone nine.

As always, if the budget comes into play, Emotiva makes great amps for the buck. An XPA-3 for LCR or an XPA-200 for LR are not expensive and are great to relieve strain from the AVR's most challenged speaker channels.

I want Auro-3D 13.3 Surround!
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post #4 of 11 Old 09-22-2012, 10:29 AM
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1. Although the marketed power spec for an AVR driving 8-ohm speakers generally only applies to 2CH driven, power specs for the predecessor model 4311CI are a little higher (2CH @ 175W and 5CH @125W) while for the SR7005 closer to average (2CH @121W and 5CH@91W). The 4311CI and successor 4520CI are both rated for 4-ohm speakers unlike the lower level Denon and Marantz AVRs. With the 4311CI or the 4520CI, it's unlikely you would need an external amp.
2. Generally yes.
3. Efficiency of the speakers (4,6,8-ohm) and whether you listen at loud reference level volume.

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post #5 of 11 Old 09-23-2012, 08:42 AM
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Quote:
Originally Posted by deeda View Post

I am evaluating whether it is better to go the route of an AV receiver, for example, Denon 4520, or the route of pre pro, like Marantz AV 7701 plus external amp, like Marantz MM 7055 or Parasound Halo A52. The focus of this particular thread is on the amp included in the AV receiver or in the dedicated amp.
The Denon literature indicates that it has 9 channels X 150 watts. The Marantz and Parasound amps offer 5 channels X 140 (Marantz) and 125 (Parasound) watts.

A good amp is timeless, processing and connectivity not so much.
Quote:
Question 1.
Are these numbers an apples to apples comparison. If all channels are driven for the Denon, Marantz and Parasound units, will they result in the 150, 140 and 125 watt amounts noted or will they result in a much lower number?

About 65% less.
Quote:
Question 2.
My rudimentary understanding is that in order to double the sound volume, you will need to increase the watts by a factor of 10. So if you want to hear something twice as loud at 10 watts, you would need a 100 watt amp. If this is the case, then I assume that the difference between a 150, 140 and 125 watt amp, is not that significant. Correct???

Yup.
Quote:
Question 3.
What are the other key factors, I need to consider in evaluating amps?
- speakers that will be used
- total harmonic distortion
- build quality
- music vs home theater use
- amp class (i.e. A, A/B, etc)
- cost

Sound quality.
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post #6 of 11 Old 09-23-2012, 08:45 AM
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Quote:
Originally Posted by deeda View Post

Question 1.
Are these numbers an apples to apples comparison. If all channels are driven for the Denon, Marantz and Parasound units, will they result in the 150, 140 and 125 watt amounts noted or will they result in a much lower number?

Manufactures rate their products in a variety of different ways. For example, you'll see these variations on 100wpc:

All channels driven, 1khz
All channels driven, 20hz-20khz
One channel driven, 1khz
One channel driven, 20-20khz
All channels driven, at x% THD
One channel driven at X% THD

For example, look at this review for a mid-range Onkyo Reciever:

http://www.hometheater.com/content/onkyo-tx-nr414-av-receiver-specs

Note it's a multi channel reciever, but the amp is rated 80watts into only two channels. When tested, here's how it's amplifier compares:

"Two channels driven continuously into 8-ohm loads:
0.1% distortion at 75.8 watts
1% distortion at 105.0 watts

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 53.1 watts
1% distortion at 66.7 watts"

Because of these variations, it's best to take WPC claims with a grain of salt.
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post #7 of 11 Old 09-23-2012, 08:47 AM
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Quote:
Originally Posted by deeda View Post

Question 2.
My rudimentary understanding is that in order to double the sound volume, you will need to increase the watts by a factor of 10. So if you want to hear something twice as loud at 10 watts, you would need a 100 watt amp. If this is the case, then I assume that the difference between a 150, 140 and 125 watt amp, is not that significant. Correct???

Yes, that is correct.

All things being equal, you are not going to tell the difference between 125watts, 140watts, and 150 watts.

Something else to consider...

It takes double the power to increase SPL by 3db. So going from a 100watt amp to a 200 watt amp, is only going to give you 3db.
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post #8 of 11 Old 09-23-2012, 08:53 AM
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Quote:
Originally Posted by deeda View Post

Question 3.
What are the other key factors, I need to consider in evaluating amps?
- speakers that will be used
- total harmonic distortion
- build quality
- music vs home theater use
- amp class (i.e. A, A/B, etc)
- cost

Yes.

Speakers first, because of the resistance. Many budget amps are not happy driving loads under 8ohms. So, if you happen to have 4 (or 6) Ohm speakers, it'll limit your field of choices.
Second, sound. Different amps sound different. It's best to audition your speakers with the amps your considering. It's your money, and your ear.
Third, power. Room size, speaker efficiency (and speaker resistance) will determine how much power you'll need to reach reference levels. Most likely, anything north of 100wpc should be absolutely fine for 99% of all Home Theaters...
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post #9 of 11 Old 09-23-2012, 08:57 AM
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Back when I had separates with big vu meters I noticed that while playing music at a fairly loud level it would play at about 5 to 7 watts and when a dynamic passage would hit peaks of 120 to 125 watts was not uncommon so when keep in mind I was running full range stereo so since I moved to an AVR and crossover to a sub 70 to 80Hz the demand is not as bad and have found in 5.1 mode that a 100wpc has been very adequate.
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post #10 of 11 Old 09-23-2012, 09:00 AM
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Originally Posted by Robert Milwaukee View Post

A good amp is timeless, processing and connectivity not so much.

Yes, yes yes yes yes.

Amps have a very simple job. High quality amps have been manufactured for decades. You can easily pick up a fantastic piece of equipment for cheap on CL or eBay.

IMO, find the cheapest receiver that has the features you want. Then shop for a good used amp (or amps).
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post #11 of 11 Old 09-23-2012, 07:16 PM - Thread Starter
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Appreciate all of the feedback. Thanks
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