Audio terms BS and not BS

GrimSurfer

GrimSurfer

Senior Audioholic
You could also use high level outputs, if your subs have that option. Powered subs have really high impedance, so driving them from the B output doesn't put any appreciable load on your amp (which sounds like a high current one, based on the specs).
 
T

TankTop5

Audioholic General
You could use a splitter on the pre-out main-in to get signal for a sub...
I don’t think so, I think the bridge on the line level pre outs disconnect the receivers amplifier.


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T

TankTop5

Audioholic General
You could also use high level outputs, if your subs have that option. Powered subs have really high impedance, so driving them from the B output doesn't put any appreciable load on your amp (which sounds like a high current one, based on the specs).
Thought of that, I’d like to get a nice quality sub but Rel and SVS don’t make subs with high level inputs.

This should probably be a new post. Who makes a sub with high level inputs? Please keep in mind I’m trying to do this on a budget, pre owned is fine by me. I know Polk makes subs with high level inputs, would those compliment my Focals?


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GrimSurfer

GrimSurfer

Senior Audioholic
The SB/PB 1000s have high level inputs. They're budget priced.
 
mtrycrafts

mtrycrafts

Seriously, I have no life.
I thought someone posted a link before....

This site has not only the equations, but a calculator built in as well.... https://www.allaboutcircuits.com/tools/rms-voltage-calculator/
I saw that. Nowhere it mentions RMS power or how it is derived. Obviously you cannot tell me how, what products are used like Vrms or Irms.
I see that Vrms is .707 of Vpeak so the current must be the same.
I guess I could get peak power just by Vpeak x Ipeak. Would that be used to get RMS power? Or is there are secret function?
Could you tell me what is the power with 10 Vrms and 10 Irms is? Or that is , 100W but is that RMS or just continuous .5 of peak power? After all, RMS has a fixed function for sine waves. I can tell you that power is not .707 of the power peak so it cannot be RMS.
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lovinthehd

lovinthehd

Audioholic Jedi
I don’t think so, I think the bridge on the line level pre outs disconnect the receivers amplifier.


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If disconnected, sure. If you split the signal out of the pre-outs, then that would allow you to reconnect the amp section of the Nad and another connection for a sub. Use y-split rca cords for example...
 
T

TankTop5

Audioholic General
If disconnected, sure. If you split the signal out of the pre-outs, then that would allow you to reconnect the amp section of the Nad and another connection for a sub. Use y-split rca cords for example...
Something like this?




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T

TankTop5

Audioholic General
Or this would be even easier.




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GrimSurfer

GrimSurfer

Senior Audioholic
Just be sure to check the input impedance of the amp and powered subs before buying to ensure the input levels will be appropriate after the signal is split.
 
T

TankTop5

Audioholic General
Back to the other rabbit trail. Forgive me for asking but why is power measured in watts, a measurement of heat? Without knowing either volts or amps isn’t a wattage a useless number?


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GrimSurfer

GrimSurfer

Senior Audioholic
Watts are a valid measure of electricity... have been for years

It would be better if we knew both volts and amps, though I can see situations where these might peak differently.

More important than the metric (pun intended) is the method. If the method of measurement is the same (ie. standard) used for everything, then a valid comparison between gear can be made.

So what is the best method?

In my mind (and that of the FTC, IEEE and other bodies that operate independent of the audio industry or retail operations),a method that rates sustained and steady output over the entire range of frequencies that make up the audible spectrum is the better than ones that do not.

People and companies that like big numbers because, well, they're big, prefer methods that result in the highest peak values. Personally, I think this is an absurd way to measure power because not only can results vary, but it relies on values that occur over an astonishingly short period of time or narrow range of frequencies.
 
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Irvrobinson

Irvrobinson

Audioholic Spartan
Back to the other rabbit trail. Forgive me for asking but why is power measured in watts, a measurement of heat? Without knowing either volts or amps isn’t a wattage a useless number?
A watt is a measure of power, and power can be expressed as a measure of heat. It's all energy. One watt is one joule of energy expended in one second, or it's the heat dissipated by one ampere at one volt conducted through one ohm for one second. As a measure of power, for example, one horsepower equals about 746 watts, and in the automotive industry engine output is often specified in kilowatts as well as horsepower.

Watts are especially useful in specifying audio amplifiers when combined with impedance, because to maintain a constant level of volts into lower impedance requires increasing power, hence watts, which is expensive to implement. 10 volts into 4 ohms requires twice the watts as 10 volts into 8 ohms, looking at watts ratings into 8 ohm, 4 ohm, and 2 ohm loads can be very revealing. However, a lot of manufacturers have historically made their amps look better at 2/4 ohm loads by very conservatively specifying their 8 ohm rating so as to meet the 2/4 ohm specifications without so rigorous an output stage.
 
GrimSurfer

GrimSurfer

Senior Audioholic
A watt is a measure of power, and power can be expressed as a measure of heat. It's all energy. One watt is one joule of energy expended in one second, or it's the heat dissipated by one ampere at one volt conducted through one ohm for one second. As a measure of power, for example, one horsepower equals about 746 watts, and in the automotive industry engine output is often specified in kilowatts as well as horsepower.

Watts are especially useful in specifying audio amplifiers when combined with impedance, because to maintain a constant level of volts into lower impedance requires increasing power, hence watts, which is expensive to implement. 10 volts into 4 ohms requires twice the watts as 10 volts into 8 ohms, looking at watts ratings into 8 ohm, 4 ohm, and 2 ohm loads can be very revealing. However, a lot of manufacturers have historically made their amps look better at 2/4 ohm loads by very conservatively specifying their 8 ohm rating so as to meet the 2/4 ohm specifications without so rigorous an output stage.
I was agreeing with you... until the last part.

How can a "less rigorous" output stage at 8 ohms double (or nearly double) output at 4 ohms, then double (or nearly double) it again at 2 ohms? Answer: It can't. Increasing power inversely proportional to impedance is one of the toughest tests for an amplifier.

If a manufacturer uses trickery at 8 ohms, then that trickery will likely show itself when impedance drops from 4 to 2 ohms... unless everything is underrated, which defeats the whole point of the trickery to begin with.

You touch on a good point though... If one keeps there eye on the ball and observes the rate of output change with halving of impedence then it is easy to see through all kinds kind of industry flummery.

But, to do that, it is important to start with a solid rating system like continuous power, or RMS, etc. Why? Because, like all meaningful power ratings, work is about effort. The longer the time a level of work can be done, then more flexible and useful it becomes.
 
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Irvrobinson

Irvrobinson

Audioholic Spartan
I was agreeing with you... until the last part.

How can a "less rigorous" output stage at 8 ohms double (or nearly double) output at 4 ohms, then double (or nearly double) it again at 2 ohms? Answer: It can't. Increasing power inversely proportional to impedance is one of the toughest tests for an amplifier.

If a manufacturer uses trickery at 8 ohms, then that trickery will likely show itself when impedance drops from 4 to 2 ohms... unless everything is underrated, which defeats the whole point of the trickery to begin with.

If you keep your eye on the ball and observe the rate of output change with halving of impedence then it is easy to see all kinds kind of flummery.

But, to do that, it is important to start with a solid rating system like continuous power, or RMS, etc. Why? Because, like all meaningful power ratings, work is about effort over time. The longer the time a level of work can be maintained, the more useful it is.
You've misunderstood my point.

I'll be more specific. Let's say that an amplifier is rated 100/200/400 watts per channel into 8/4/2 ohms. What you sometimes find is that their actual, measured, continuous output into 8 ohm loads is more like 150-200 watts, ~250 watts into 4 ohm loads, and then they squeak by the 2 ohm spec right at 400 watts. Krell and Levinson used to do this with their lesser amps years ago. Does the amp output really double as impedance halves? IMO, no, but by the specs, yes it does.
 
GrimSurfer

GrimSurfer

Senior Audioholic
You've misunderstood my point.

I'll be more specific. Let's say that an amplifier is rated 100/200/400 watts per channel into 8/4/2 ohms. What you sometimes find is that their actual, measured, continuous output into 8 ohm loads is more like 150-200 watts, ~250 watts into 4 ohm loads, and then they squeak by the 2 ohm spec right at 400 watts. Krell and Levinson used to do this with their lesser amps years ago. Does the amp output really double as impedance halves? IMO, no, but by the specs, yes it does.
I totally get your point, Irv. I'm just adding that once you know how things should work, then it's easy to see through a trick like the one you first described... as long as there are three data points.

Electrically speaking, output should double when impedance halves. That's what we call an "expected result" under Ohm's Law.

Provided the power and output stages of an amp are of good design, then there's no reason why Ohm's Law shouldn't apply. But most often they are not. That doesn't stop the application of Ohm's Law and the interpretation of manufacturer specs.

Honestly rated gear may not double with halving of impedance but it will still increase power inversely proportional to impedance eg. 120W @ 8 ohms, 240 @ 4 ohms, 480W @ 2 Ohms.

What it can't do under Ohms Law is deviate from proportionality (eg. 120W @ 8 ohms, 240W 4 ohms, 400W @ 2 ohms) without some reasonable explanation that tells us where the watts went between 4 and 2 ohms. Manufacturers who don't make it clear where the power went can be legitimately accused of having a design with some shortcomings. Typically, this occurs from limitations connected to the power supply, output stage, or heat sinks (electrical resistance in metals increases with heat).

The real crime, however, is when there is an unproportional increase of power when impedance decreases (120 --> 240 --> 500). This is a clear violation of the laws of physics and, in almost all circumstances (except the one I outline below) evidence of a serious mistake or purposeful misdirection. Why? Because it makes no sense whatsoever that output should increase disproptional to impedance.

This only holds true when comparing like things (ie. 2 channels driven OR 1 channel driven). It doesn't necessarily apply when comparing two different things, like 4 ohm --> 2 ohm output @ 2 channels driven versus 1 channel driven @ 2 ohms in a bridged amp. Why? Because comparing two unlike things equally ignores the possibilities of efficiency gained through bridging.

So whenever I see stats that deviate from Ohms Law in any logical or meaningful way, I question whether the data is valid or invalid.

I hope this clarifies my previous post... it wasn't as much about what you wrote as the principles under Ohm's Law can be easily used to spot industry flummery.
 
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T

TankTop5

Audioholic General
A watt is a measure of power, and power can be expressed as a measure of heat. It's all energy. One watt is one joule of energy expended in one second, or it's the heat dissipated by one ampere at one volt conducted through one ohm for one second. As a measure of power, for example, one horsepower equals about 746 watts, and in the automotive industry engine output is often specified in kilowatts as well as horsepower.

Watts are especially useful in specifying audio amplifiers when combined with impedance, because to maintain a constant level of volts into lower impedance requires increasing power, hence watts, which is expensive to implement. 10 volts into 4 ohms requires twice the watts as 10 volts into 8 ohms, looking at watts ratings into 8 ohm, 4 ohm, and 2 ohm loads can be very revealing. However, a lot of manufacturers have historically made their amps look better at 2/4 ohm loads by very conservatively specifying their 8 ohm rating so as to meet the 2/4 ohm specifications without so rigorous an output stage.
Thanks, I’m very visual and I need to be able to visualize a consent to understand it. Just before I read your statement someone else gave me virtually the same response...

Not my words btw.

“Because James Watt who contributed to the invention of the stern engine established the WATT as a unit of power to define the capacity of a steam engine. One Watt = one Joule per second. One Watt = 0.00134 British Horse Power. George Simon ohm discovered a law of electrical principles that power (watts) is equal to voltage times current and voltage is always equal to current times resistance. Watts (P) = E x I and E = I x R.”


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