dynamic power vs. RMS power ?

[audioman00]

Anyone tell me the difference? My yammi rx-v870 tells me 130wpc dynamic, 80 wpc RMS 0.016 thd. Will i more likely see more than 80 watts clean? or maybe less, this thing is definately built in and out good enough to push more than 80wpc IMHO. The transformer has some serious looking 14awg wire coming to and from it. the caps are rated 63v 10,000 micro farad. anyways, thanks for the help in this matter. -Brandon

 

[gene]

Don't put too much stock in "Dynamic Power Measurements". They are based on a very short term transient power condition which does provide some indication on what the amp can deliver with respect to short term peaks, but does not imply the amp can sustain those peaks. This is similar to other amplifier manufacturers touting "Instantaneous Current" in their specs. Loud sustained clean audio requires continuos power thus when determining how much power you may need, this is the # you should base it on, with all other things being equal.

 

[Unregistered]

so you are saying look at the RMS ??

 

[markw]

Yes.

When comparing, apples to apples is always best. Even then, read the fine print carefully.

How do they arrive at this RMS figure?

Using a 1khz test tone? ...or perhaps over a range of 20 - 20khz. The former will always be greater.

With one channel driven? ...or with all channels being driven simultaneously? Again, the first will always be greater.

Look at Dynamic power as a form of headroom, for those occasional times when you would otherwise exceed the power ratings of your unit.

The only company (I can recall) that seems to reference dynamic power is NAD, but they don't pump this as much as many would like to think. When specing their ad copy, they use the RMS ratings, notthe dynamic power. And, FWIW, their RMS power ratings are quite honest in their derivation.

 

[Hawkeye]

Its just not as simple as you would hope as there is a lot of "fudgery" in stated numbers. As markw states, "With one channel driven? ...or with all channels being driven simultaneously?" Many companies, unfortunately, rate the output at two channels driven not all channels driven, thus artificially inflating their numbers.

One test, Sound & Vision, Dec. 2002, found the NAD T752 hit 92 wpc before clipping even though it was only rated at 80 wpc--conversely, the Denon 2803, rated at 90 wpc by Denon, clipped at 61 wpc when five channels were driven. Granted this is but one test and done a couple years ago, but it helps to support the "fudgery" I'm speaking of.

In the end numbers are numbers and should only serve as a guide. The true test is whether YOU like what you're hearing.

 

[jeffsg4mac]

A lot of companies do fudge their numbers, however, in defense of Denon, NAD and some others, they do state their numbers as x2 channels driven not all. And, as someone stated in another thread, it is not likely you would ever have a signal that would tax the amp in that way, no movie or music track I have ever heard drives all the channels full out for any length of time. It just never happens. The closest I think I have found are the storm scenes in Master and Commander, I had it cranked to realistic levels and my 2803 didn't even sweat. Just a little warm to the touch. So with these receivers, when something comes through that needs some power to a channel or two, it is not likely that the others are going at full tilt as to rob the channels needing the power. But I do agree some companies really fudge their numbers.

 

[annunaki]

NAD states all of their power specifications as all channels driven simultaneously to continuous power below clipping into 8/4 and sometimes 2 ohms (2 ohm operation usually for 2 channel, amps and 2 channel operation only).

 

[Hawkeye]

NAD states all of their power specifications as all channels driven simultaneously to continuous power below clipping into 8/4 and sometimes 2 ohms (2 ohm operation usually for 2 channel, amps and 2 channel operation only).

That would be exactly how I read the following:

http://www.nadelectronics.com/power/power_main.htm

From everything i've heard and read NAD UNDERSTATES their power. With that said, jeffsg4mac is correct in saying you would rarely, if ever, drive all channels full-out.

 

[jeffsg4mac]

Yes but as so well explained by Dan B, that power envelope, dynamic stuff is a bunch of BS. Any amp that can do it rated power can also have enough dynamic power for short term.

 

[markw]

Who is Dan B?

Did he input on this thread?

 

[jeffsg4mac]

No, read about it here

 

[markw]

Oh, now I see.

but, before you attempt to vilify NAD, please be aware that their RMS power ratings are among the most conservative in the industry.

 

[jeffsg4mac]

You are talking to person who has two pieces of NAD in his house at this moment and has had 3 other units One of their first AV receivers and an older Monitor series power-tracker 140x2 amp. My father is using the receiver and the amp needs some repair. I want to drive an SVS sub with it. They are no more conservative than ROTEL, ADCOM or Parasound, ect. and they are overpriced for what you get. One of their new products is very gimicky, that receiver with the built in DVD player, Junk. I am not trying to bash NAD, but they are not the company they used to be in my opinion of course

 

[annunaki]

I understand the dynamic vs. continuous debate. I have a problem with companies saying 100 watts x 7 and claiming it is a 700 watt receiver when they used a two channel FTC method for the numbers. You know and I know that that receiver would not be able to deliver 700 watts all at once. If it cannot do it it sould not be stated. Receivers using the FTC two channel method should not be able to state their power x 7. it should be stated as: Seven channel receiver capable of no greater than the sum of the FTC 2 channel power at any given time.

Here would be an example:

XYZ 7 channel receiver

120 watts x 2 FTC power two channels driven simultaneously

35 watts x 7 all channels driven simultaneously

There is no bs here, it is plain as day, this is what you are paying for. the companies that choose to rate more conservatively would benefit from this I suppose.

It is misleading when it is stated like this:

120 watts x 2 front L/R

120 watts center

120 watts x 2 rear L/R

120 watts x 2 surround back L/R

If it is going to be listed that way then it should look like this:

120 watts x 2 front L/R (if they are the only channels running)

120 watts center (if it is the only channel runnning)

120 watts x 2 rear L/R (if they are the only channels running)

120 watts x 2 surround back L/R (if they are the only channels running)


Even if all channels are not running all out, one would still not get the power they claim. Here is an example. Say there is a large explosion or action in the front left partial right and center that lasts for 5 seconds. The volume is at reference level and the front left partial right and center speakers would require (we will use the 240 watt amp from above 120 ftc x 2) 100% of the power the receiver has for the explosion (80% for the center and left, 96 watts each and 20% for the right 48 watts). Now let us say that the explosion or action sets off another one that lasts for seven seconds (it is now supposed to be louder)but now is asking for 80% power across the front three speakers (64 watts each)and requires 20% of that 240 watts for the rear and surround back channels (12 watts each) for falling debris. Because the receiver does not have the capability to run all the channels simultaneously to the same power high power level ther has been a reduction in dynamic range from the original explosion about -1.5 db in the front.

Now let us say the same scenario exists with a receiver designed to do 75 watts continuous all 7 channels driven simultaneously. For the first explosion the left and center would receive 75 watts a channel and the left probably about 45 watts. With the second explosion the front three would STILL RECEIVE THE SAME AMOUNT OF POWER and more than the first explosion or action with no loss in dynamics. The rear channels would receive roughly 15 watts each. While there is not much audible difference in the second scenario between receivers, there would be a negative difference between the first an second scenarios with the first receiver. And a positive one with the second receiver.
The second action sequence is supposed to sound bigger and more dynamic (which it does on receiver 2) but on the first FTC derrived receiver it stays about the same overall volume.


Sorry for the long post guys.

 

[Hawkeye]

You are talking to person who has two pieces of NAD in his house at this moment and has had 3 other units One of their first AV receivers and an older Monitor series power-tracker 140x2 amp. My father is using the receiver and the amp needs some repair. I want to drive an SVS sub with it. They are no more conservative than ROTEL, ADCOM or Parasound, ect. and they are overpriced for what you get. One of their new products is very gimicky, that receiver with the built in DVD player, Junk. I am not trying to bash NAD, but they are not the company they used to be in my opinion of course

I also own NAD and would agree their receiver/dvd unit combo is cheesy at best. Though I would also agree they may not be quite the company they once were, I don't feel they're really overpriced. Compared to a lot of junk on the market, NAD can be had at a reasonable price if you shop carefully and don't mind buying last year's models. Matched with the right speakers thay can sound fabulous.

 

[Rip Van Woofer]

That's Dan Banquer, resident amp guru and BS exterminator. Do a search. The relevant thread was a month or two ago.
EDIT: Oops, I didn't see p.2 of this thread -- I see Jeff already posted up a link. Never mind. Talk amongst yourselves...

 

[markw]

HT receivers skewed the entire equation.

They don't have to post specs using the same stringent standard the FTC applied in the early 70's. They are free to use, let's say, "more creative" methods of reporting power. ...not unlike autosound manufacturers.

Where NAD shows it's mettle is in good ole fashioned two channel amps, either integrated or power. That's their forte and I think they are hard to beat in that arena, when weighing sound and dollars.

With multi channel receivers I also tend to think they (NAD) are a little on the pricy side. And, I'm a whole less picky when listening to a movie as opposed to pure stereo. I'm more than satisfied with a Denon 2802 and some Athena speakers.

Stereo is another story. I'm quite a bit more critical when listening to music. FWIW, my stuff is listed at Audio Asylum member systems under "markw*" ... don't ask, long story.

 

[av_phile]

There really shouldn't be any debate between dynamic power and continuous power.

From a technical point of view, dynamic power is simply peak power. And anything that has as RMS value has a peak value. The current and voltage going to the speakers included.

Some audiophiles check the dynamic power abilities because they aver that real music as captured in an exquisite recording consists of dynamic signals that give off energy bursts in short durations. Hence to them dynamic power is important.

Ofcourse, if you listen at "normal" levels, continuous power rating is all that is needed. Those short musical bursts can be well taken care of if you listen well below the rated continuous power. It is this notion that prompts many to get the most powerful amps they can afford, all other things considered ok. An amp straining to deliver the SPLs you want is the worst sounding amp of all. But even with recordings of 90db dynamic range, you can hardly strain an amp that has more continuous power than you'll ever need to listen with.

 

[av_phile]

I understand the dynamic vs. continuous debate. I have a problem with companies saying 100 watts x 7 and claiming it is a 700 watt receiver when they used a two channel FTC method for the numbers. You know and I know that that receiver would not be able to deliver 700 watts all at once. If it cannot do it it sould not be stated. Receivers using the FTC two channel method should not be able to state their power x 7. it should be stated as: Seven channel receiver capable of no greater than the sum of the FTC 2 channel power at any given time.

Here would be an example:

XYZ 7 channel receiver

120 watts x 2 FTC power two channels driven simultaneously

35 watts x 7 all channels driven simultaneously

There is no bs here, it is plain as day, this is what you are paying for. the companies that choose to rate more conservatively would benefit from this I suppose.

It is misleading when it is stated like this:

120 watts x 2 front L/R

120 watts center

120 watts x 2 rear L/R

120 watts x 2 surround back L/R

If it is going to be listed that way then it should look like this:

120 watts x 2 front L/R (if they are the only channels running)

120 watts center (if it is the only channel runnning)

120 watts x 2 rear L/R (if they are the only channels running)

120 watts x 2 surround back L/R (if they are the only channels running)

Couldn't agree more. Unfortunately, such an amp or receiver will not sell to most number conscious consumers.