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# Bi-amping B&W CM10 - Page 7

Quote:
Originally Posted by whoaru99

Quote:
Originally Posted by arnyk

There's an obvious situation with data input to the calculator that is unlikely to be common to most home theaters

and that doesn't look right, either.

I was able to come to the same result using this calculator that shows more detail.

..including the assumption that its a mono system: "1 speaker"

So you are assuming that everybody listens to mono?
Quote:
If you add 3dB on top of the actual requirement (28.5W) to hit 100dB it comes out to the same 57 watts. What is factored in certainly is more clear in the calculator I usually use.

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Quote:
Originally Posted by whoaru99

That absolutely IS peak level and peak power requirement.

If you want even higher peak SPL then obviously you will need more power.

If it is a dB level that was measured on a SPL metre then it is only the top of the average sound pressure level. Peaks can be 6 to 25dB higher for very brief moments too quick for a SPL metre to accurately measure.

It's all part of the problem and limitations of relaying real life through a medium. Say for example you are standing out in a swamp and you can just hear a mosquito buzzing around. The next moment you start to hear a swamp boat approaching and go past you. The noise from the swamp boat is about a million times louder than the mosquito. Now think about the problems of relaying that dynamic range through the audio system in your lounge.

Photography has the same problem of relaying the dynamic range of light in the real world that we see over a medium that is much more limited in its light output than what the sun can do out in the real world. At some point the dynamic range has to be compressed to fit our limited output range.
Quote:
Originally Posted by arnyk

So you are assuming that everybody listens to mono?

You questioned where the numbers in that calculator came from. I provided one possible scenario.
Quote:
Originally Posted by arnyk

The calculator presumes that the amp and speakers have flat response over the frequency range of interest.

Ok, but how do you know that?
Quote:
Originally Posted by kiwi2

If it is a dB level that was measured on a SPL metre then it is only the top of the average sound pressure level. Peaks can be 6 to 25dB higher for very brief moments too quick for a SPL metre to accurately

Do you really not get it, or are you simply trying to obfuscate the matter?

The number you put in IS the peak number. If 105dB is not the peak you are shooting for then put in a different number.

If you believe the peak you need to hit is 140dB then put that in the calculator.

That said, I think 105dB peak is a decent number to discuss. That means (in this example) it takes 75wpc to hit 105dB peaks. If your music has 20dB peaks above average that means you could run 85dB average with 0.75 watts per channel average, with 20dB headroom available for the 105dB peaks.
Quote:
Originally Posted by whoaru99

Do you really not get it, or are you simply trying to obfuscate the matter?

The number you put in IS the peak number. If 105dB is not the peak you are shooting for then put in a different number.

It just says "dB SPL at listening position"

That would be a dB level a SPL metre would register. That is not the same as very brief peaks that exist in musical recordings that peak headroom allows for.
What part of "put in the peak SPL you are shooting for" is unclear to you?

Now where is the facepalm smiley?

Sorry for all the edits....darn tablet
Edited by whoaru99 - 12/29/13 at 2:20pm
Quote:
Originally Posted by Heinrich S

Yeah but at what frequencies? Isn't that relevant for audio?

It's relevant, in the context of amp ratings, but it's really not much you need to worry about. Also keep in mind these things are just crude tools to help determine the lower limits of required power. If the calculator says you use x watts peak, then you pick an amp that (at minimum) can do x watts over the whole audio band, from 20-20k, into a load at least as difficult as your speakers. That covers your peak power needs at all frequencies. If those calculators are even off by a little, you may genuinely need considerably more power than they indicate, so I don't think it's wrong to get "more than enough" power, provided the speakers are up to the task.
Quote:
Originally Posted by Wayne Highwood

It's relevant, in the context of amp ratings, but it's really not much you need to worry about. Also keep in mind these things are just crude tools to help determine the lower limits of required power. If the calculator says you use x watts peak, then you pick an amp that (at minimum) can do x watts over the whole audio band, from 20-20k, into a load at least as difficult as your speakers. That covers your peak power needs at all frequencies. If those calculators are even off by a little, you may genuinely need more power than they indicate, so I don't think it's wrong to get "more than enough" power, provided the speakers are up to the task.

Okay, but if it says I need 100 watts to hit 100 dB for example, at 1kHz for all I know, then for 40 Hz, 50 Hz, or any lower frequency signals that power may be significantly more. It's easy to look at the calculator, punch in some numbers and get a SPL value, then buy an amp that has similar power from 20 Hz to 20khz, but again, if the values punched into the calculator only derive results based on a single frequency, for instance, then the power figures would be completely misleading if we are talking about real world audio signals.

Since there is an absence of reliable information concerning these calculators I can only speculate. But if you are listening to the 1812 Overture, for example, that has significant bass in there and quite loud too, and you listen at 100 dB peaks, the figure of 40 watts, or 50 watts (whatever the value was for a 90 dB speaker at 3 meter distance) might require 100 watts, or 200 watts because of significant energy in the lower spectrum. The calculator can't account for bass signals.

I would think the power demands placed on the amp would be significantly higher when involving bass. Wouldn't you agree?
If its that critical then contact the speaker mfg to gain a better understanding of their sensitivity number, as I eluded to earlier.

In the absence of specific data then it is what it is...a generic calculator, much better than nothing, not as good as a site specific survey. The latter of which I dont believe has ever been the intent. They're general guidelines.
Edited by whoaru99 - 12/29/13 at 2:33pm
I would, but also I think Arny was correct when he said these calculators presume that the amps and speakers have flat response across the band in question, so it's been accounted for. These calculators are just that, rather crude tools to give the end user a reasonable guestimate of power requirements. Don't take their peak power ratings as anything more than that.
Quote:
Originally Posted by Wayne Highwood

I would, but also I think Arny was correct when he said these calculators presume that the amps and speakers have flat response across the band in question, so it's been accounted for.
The issue here is the sensitivity of the speaker. It is that which contributes to the SPL. Here are the impedance measurements of a random speaker from stereophile:

We see two large peaks of impedance at 20 and 50 Hz. Here is the frequency response (in black):

How do you go backward from frequency response to determine the impedance (and importantly the phase)?
Quote:
Originally Posted by kiwi2

Quote:
Originally Posted by whoaru99

Do you really not get it, or are you simply trying to obfuscate the matter?

The number you put in IS the peak number. If 105dB is not the peak you are shooting for then put in a different number.

It just says "dB SPL at listening position"

That would be a dB level a SPL meter would register. That is not the same as very brief peaks that exist in musical recordings that peak headroom allows for.

Through your comments I sense a belief that a peak-reading SPL meter is pretty much a waste of time because it couldn't possibly capture short term peaking. How do you know that is true?

Whatever they are, they are among the best tools that we have. Sitting around feeling defeated because our tools might be imperfect is not a very productive thing to do. Most successful people work with imperfect tools and situations and do the best they can with them. Do you want to be successful?

I sometimes get this feeling that in some people's minds I'm a big bad meanie standing between them and something that they want. If that is the case why not stop wasting everybody's time and just run right out and obtain some multi-killowatt amplifiers?

One alternative is to establish some kind of an offset between what the SPL meter reads and the very brief peaks that exist in musical recordings that peak headroom allows for. 3 dB seems to be a good example of that.

The other alternative is use a measurement that SPL meters might make more accurately such as average levels, and add a far larger offset to that, such as 20 dB.
Quote:
Originally Posted by amirm

Quote:
Originally Posted by Wayne Highwood

I would, but also I think Arny was correct when he said these calculators presume that the amps and speakers have flat response across the band in question, so it's been accounted for.
The issue here is the sensitivity of the speaker. It is that which contributes to the SPL. Here are the impedance measurements of a random speaker from stereophile:

We see two large peaks of impedance at 20 and 50 Hz. Here is the frequency response (in black):

How do you go backward from frequency response to determine the impedance (and importantly the phase)?

Looks like a rabbit hole to me. Why worry about this? Why not follow accepted standards and use the 2.83 volt level as our reference?
Quote:
Originally Posted by Heinrich S

Quote:
Originally Posted by Wayne Highwood

It's relevant, in the context of amp ratings, but it's really not much you need to worry about. Also keep in mind these things are just crude tools to help determine the lower limits of required power. If the calculator says you use x watts peak, then you pick an amp that (at minimum) can do x watts over the whole audio band, from 20-20k, into a load at least as difficult as your speakers. That covers your peak power needs at all frequencies. If those calculators are even off by a little, you may genuinely need more power than they indicate, so I don't think it's wrong to get "more than enough" power, provided the speakers are up to the task.

Okay, but if it says I need 100 watts to hit 100 dB for example, at 1kHz for all I know, then for 40 Hz, 50 Hz, or any lower frequency signals that power may be significantly more. It's easy to look at the calculator, punch in some numbers and get a SPL value, then buy an amp that has similar power from 20 Hz to 20khz, but again, if the values punched into the calculator only derive results based on a single frequency, for instance, then the power figures would be completely misleading if we are talking about real world audio signals.

This has been covered several times. If the amp and the speaker have reasonably flat response then there are no significant frequency response variations to worry about.
Quote:
Originally Posted by Heinrich S

Quote:
Originally Posted by arnyk

The calculator presumes that the amp and speakers have flat response over the frequency range of interest.

Ok, but how do you know that?

Flat response is inherent in how the calculations are done. Seeing no evidence that the calculations are sensitive to frequency, I presume with good confidence that they they aren't sensitive to frequency.
Quote:
Originally Posted by amirm

The issue here is the sensitivity of the speaker. It is that which contributes to the SPL. Here are the impedance measurements of a random speaker from stereophile:

We see two large peaks of impedance at 20 and 50 Hz. Here is the frequency response (in black):

How do you go backward from frequency response to determine the impedance (and importantly the phase)?

I was just about to comment on the importance of finding a speaker that measures as linear as possible, and amirm provides an example that proves my point.

The 20Hz peak is of no concern since the speaker is clearly not designed to reproduce a 20Hz frequency (-20dB). The frequency plot indicates that the useful bottom range of the speaker is just below 40Hz. The 50Hz pinch doesn't bother me personally, since my subwoofer delivers that frequency much more admirably.

In short. I wouldn't buy that speaker
Quote:
Originally Posted by whoaru99

What part of "put in the peak SPL you are shooting for" is unclear to you?

Where are you quoting that from? I see no mention of that on the calculator page you provided. In fact you don't even enter desired SPL as you enter speaker sensitivity and your amplifier power and it calculates SPL from that.

What I do see written there that is relevant is... "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening position."
Quote:
Originally Posted by arnyk

Through your comments I sense a belief that a peak-reading SPL meter is pretty much a waste of time because it couldn't possibly capture short term peaking. How do you know that is true?

None of the SPL meters I own display peaks that only last for a fraction of a second even when in fast average mode.

A good relevant discussion in this thread here...

And...

http://en.wikipedia.org/wiki/Sound_level_meter#LCpk:_peak_sound_pressure_level
Quote:
Originally Posted by kiwi2

Where are you quoting that from? I see no mention of that on the calculator page you provided. In fact you don't even enter desired SPL as you enter speaker sensitivity and your amplifier power and it calculates SPL from that.

What I do see written there that is relevant is... "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening position."

kiwi2,

The confusion seems to be peak SPL versus dynamic headroom. The calc is based upon a RMS amp rating, not the amps peak value.

Of course, you could enter peak amps and get meaningful feedback, but the calc is designed to guide the user to choice of rms values. My understanding..
Quote:
Originally Posted by kiwi2

What I do see written there that is relevant is... "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening position."

That's right. Why? Because it's much easier to provide a simple calculator and expect the user to apply grey matter in determining irregularities specific to their system.

In other words, here is what SPL you will reach with the power listed, and at the distance listed, in open air with a speaker that has a flat FR. This is absolutely the correct way to do things because it's not making wild guesses about your or anyone elses system that can be affected by any number of things.

I can use the calculator and apply adjustments specific to my setup. I don't need to subtract adjustments made by some arbitrary guess for room gain or any other manner of wild guesses.

Amplifier dynamic headroom is the amps ability to supply power over and above its rated power rating. So while your amp might produce 100w which you plug into a SPL calculator and gives you 101dB, it doesn't allow for any dynamic power available over and above this. Why? Because not all amps have the same dynamic headroom. Again, it's left to the reader to understand this is a basic calculator, and apply some grey matter.

Same with off axis listening position. Speakers have different off axis response, to apply some arbitrary figure in a vain attempt to satisfy the needs of a user not able to apply grey matter is beyond stupid.

If you're looking at how things such as the above apply to your system. Then you need to move past a simple SPL calculator. Study how each of these specific things effect SPL. Then you can return to the basic calculator and apply that knowledge to the output given by the calculator.

It boggles my mind that something as simple as an SPL calculator is causing so much confusion in a specific forum such as this!
Edited by Audionut11 - 12/29/13 at 7:43pm
Quote:
Originally Posted by kiwi2

Where are you quoting that from? I see no mention of that on the calculator page you provided. In fact you don't even enter desired SPL as you enter speaker sensitivity and your amplifier power and it calculates SPL from that.

What I do see written there that is relevant is... "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening position."

Keep thinking about it. Sooner or later it will click.

One thing to get sorted out is dynamic range of music vs. amplifier headroom. The other calculator you've been using has caused confusion for you in this regard.
Edited by whoaru99 - 12/29/13 at 8:21pm
Quote:
Originally Posted by UndersAVS

kiwi2,

The confusion seems to be peak SPL versus dynamic headroom. The calc is based upon a RMS amp rating, not the amps peak value.

Of course, you could enter peak amps and get meaningful feedback, but the calc is designed to guide the user to choice of rms values. My understanding..

Yes, it is based on rated amplifier power but the SPL calculated is the max/peak SPL you can get with that rated power. If you want to factor in dynamic range of music then you need to subtract that from the max/peak shown by the calculator for your inputs to get the average SPL it could support/sustain

As in the example I posted previously...

The max/peak SPL based on the inputs was 105dB. If you have music with 20dB dynamic range then that has to be subtracted from the calculated number. So 75wpc in the example posted and in consideration of the music dynamic range of 20dB, facilitates 85dB average level with peaks to 105dB.

If you listened to music with less dynamic range, say 10dB, the max/peak SPL of the system doesn't change, it's still 105dB, but the average level would rise to 95dB.

It's pretty straightforward.
Quote:
Originally Posted by kiwi2

In fact you don't even enter desired SPL as you enter speaker sensitivity and your amplifier power and it calculates SPL

You're correct. I did mis-state that you put in the SPL, however that's only material to how you work with the calculator. Doesnt change the message.
Quote:
Originally Posted by whoaru99

Yes, it is based on rated amplifier power but the SPL calculated is the max/peak SPL you can get with that rated power.

You're still blathering about that calculator? Yeah, of course its straightforward. If the bold letter's at the top of the page "HOW LOUD WILL IT GO" weren't enough, then the description just below might be somewhat of a tipoff. "This calculator will compute the predicted maximum sound pressure level (loudness) at the listening position."
_
Quote:
If you want to factor in dynamic range of music then you need to subtract that from the max/peak shown by the calculator for your inputs to get the average SPL it could support/sustain

Grammar that could only be cultivated by one of this nation's fine institutions of public education. Almost as good as a 3rd grade elementary school student living in Germany.
_
Quote:
If you listened to music with less dynamic range, say 10dB, the max/peak SPL of the system doesn't change, it's still 105dB

And if I listen to no music, the system's peak SPL is still the same. But... if I moved my chair back three feet, max SPL decreases. Three feet forward and it increases. Now can I be excused from my lessons for recess?
Oh oh, the Grammar Police are out. LOL!

By the way, the lessons weren't intended for you. They were intended to build off what you said. So, in that regard, you totally missed the boat. Go stand in the corner for making the false asssumption.
Edited by whoaru99 - 12/29/13 at 11:10pm
Quote:
Originally Posted by whoaru99

Oh oh, the Grammar Police are out. LOL!

If they were, you would be the first arrested.
Quote:
By the way, the lessons weren't intended for you. They were intended to build off what you said. So, in that regard, you totally missed the boat. Go stand in the corner for making the false asssumption.

Uh huh. So when you busied yourself pointing out to everyone (other than me) that the wattage variable is used in the online SPL calculator to determine... SPL, did it occur to you that grammar really does count. It ain't "straight-forward," if you can't write it so.

BTW If you're reading this message. It isn't intended for you. It was written for someone else.
Quote:
Originally Posted by whoaru99

If you listened to music with less dynamic range, say 10dB, the max/peak SPL of the system doesn't change.

Max and peak are different things. Max may be an average of 0.2 of a second. Peak may be a brief moment that happens much quicker than that. Peak refers to single information in the recording itself.
Quote:
Originally Posted by UndersAVS

If they were, you would be the first arrested.
Uh huh. So when you busied yourself pointing out to everyone (other than me) that the wattage variable is used in the online SPL calculator to determine... SPL, did it occur to you that grammar really does count. It ain't "straight-forward," if you can't write it so.

BTW If you're reading this message. It isn't intended for you. It was written for someone else.

LOL.
Quote:
Originally Posted by kiwi2

Max and peak are different things.

I agree they can be different.

What's your point relative to the calculator or isn't that your point?
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