Efficient vs. Inefficient speaker - Page 2 - AVS Forum
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post #31 of 45 Old 05-13-2013, 05:05 PM
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The AES, I believe in conjunction with the BAS, reported peak-to-average in music as 17 dB, a power factor of 50. That is probably a reasonable headroom target. Few people know how much power their speakers are consuming at their listening level, however.... I have seen 25 - 30 dB reported for movies, but as Arny implies that is probably largely in the subwoofer region.

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post #32 of 45 Old 05-14-2013, 07:16 AM
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Quote:
Originally Posted by arnyk View Post


Reference level (85 dB) with 2 channels runs a watt or two in most systems, so peak levels might reach 100 wpc. Infrequent brief clipping is hard to detect.

Id like to explore this a bit.

Firstly, I agree infrequent clipping of the peaks is hard to detect audibly. But what are the other implications of peak clipping? A few candidates:

1) Compression
2) Speaker damage
3) Amp damage

1) Compression - at some point, you reach a threshold where you either A) bleed the power supply dry and/or B) surpass the output transistors maximum
2) Speaker damage - self explanatory?
3) Amp damage - regular and repeated exceeding of the amps rated output at the least shortens its life or worse. yes or no? (obviously this depends how far your pushing it)

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post #33 of 45 Old 05-14-2013, 10:00 AM
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Jim, whenever the amp clips, even if it's just lopping off a transient peak here and there, it produces high order harmonic distortion. This transient distortion is cumulative. Very little is tough to hear, but if enough piles up it becomes audible. It is the sort of distortion our ears find highly objectionable even in small amounts. It typically has you reaching to reduce the volume control. (That's a good response to have, as the amps at this point are starting to put out higher average power, putting your speakers at increased risk of damage.)

Inaudible, transient clipping is probably not much of a real problem for most folks or their gear, Jim, even though I suspect it happens all the time. If it still sounds good (open, effortless, neutral), it probably is safe. If it starts to sound steely, edgy, harsh, or flat, you're running in the red and should reduce the volume. If your amp runs hot, it will shorten it's life.
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post #34 of 45 Old 05-14-2013, 11:58 AM
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The additional distortion (and power) is actually much less than most people think but it is there, and biased towards the higher frequencies and thus the drivers with the least power handling capability. Look up the frequency spectrum of a square wave and you will see the harmonics actually fall off fairly quickly. IMO to cause any sort of damage you would have to be exceeding your speaker's power capacity routinely. Note that too much power can damage speakers, clipped or not.

Compression I associate with speakers that have exceeded their linear excursion range. A little further and the voice coil will hit mechanical limits, potentially damaging it physically. Overheating can warp the coil and eventually open the wire (preventing further damage but at the trade of no mode sound). Overdriven amplifiers will compress then go into hard clipping, fairly rapidly for SS, as power output rises past its capacity. The power of a square (clipped) waveform is higher than a pure sinusoid, and definitely higher than musical signals.

All this matters little if you are lopping off peaks of only milliseconds, as Wayne said, in the middle of a loud burst of music (or an explosion in a movie -- I defy anyone to distinguish between clipping and a loud blast or gunshot).

Arbitrarily choosing a pair 90 dB/W/m speakers placed 12' away but near a side wall, just 1 W of power will produce about 85 dB at the listening position. That is pretty durn loud. Going up, 10 W will produce about 95 dB, and 100 W about 105 dB, a level I personally find a bit painful.

My less sensitive speakers need about 200 W for the same output, which means an external amp but my Emotiva does just fine. Slightly more efficient speakers, say 93 dB, means you only need 50 W to hit 105 dB. Sensitivity matters, of course, but I am just not sure it is a thing of much concern given the sensitivity ratings of most speakers and the relatively large power output of AVRs and inexpensive amplifiers. Back in the 70's when 25 W/ch was considered average and 100 W/ch was huge, maybe, but not now...

Frankly, I think the bigger problem now is people playing their systems so loudly they are suffering hearing damage without realizing it.

All IME/IMO/etc. - Don (eh?)

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post #35 of 45 Old 05-15-2013, 01:08 PM
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Quote:
Originally Posted by jim19611961 View Post

Very likely considering not one person ive ever known has a 1000 watts (per channel) and given most amps people DO have would be driven to over 20% distortion TRYING to make a 1000w peak.

confused.gif

I powered a pair of 4" two ways, Klipsch RB15, with an EP4000 for a year or so, tickling the clip lights on occasion!

That's 450W@8ohms, and 635w@4ohms. The small, 9lb Klipsch bookshelves, have the most modest of drivers too. The "compression" rolleyes.gif tweeter is nothing more than a small magnet w/a heat sink attached, no bigger around than a big coin.

I prefer the high-sens/high-power approach, I'm currently utilizing 16.8kw in our modest, non-dedicated family room. The mains are 2kw each, surrounds 1kw each, two 2.4kw subs and a 2kw IB.

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post #36 of 45 Old 05-15-2013, 02:39 PM
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Quote:
Originally Posted by FOH View Post

confused.gif

I powered a pair of 4" two ways, Klipsch RB15, with an EP4000 for a year or so, tickling the clip lights on occasion!

That's 450W@8ohms, and 635w@4ohms. The small, 9lb Klipsch bookshelves, have the most modest of drivers too. The "compression" rolleyes.gif tweeter is nothing more than a small magnet w/a heat sink attached, no bigger around than a big coin.

I prefer the high-sens/high-power approach, I'm currently utilizing 16.8kw in our modest, non-dedicated family room. The mains are 2kw each, surrounds 1kw each, two 2.4kw subs and a 2kw IB.

I didnt say no one had a 1000 watts. I said no one I have known has.

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post #37 of 45 Old 05-16-2013, 12:16 PM
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^ ^ ^

Gotcha

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post #38 of 45 Old 05-16-2013, 01:40 PM
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Quote:
Originally Posted by FOH View Post

^ ^ ^

Gotcha

confused.gif

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post #39 of 45 Old 05-16-2013, 09:47 PM
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"Gotcha" = "I understand"

In your case, "I unnerstan, y'all" smile.gif

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post #40 of 45 Old 05-17-2013, 07:56 AM
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I should've made myself more clear.

Thanks Don, good lookin' out cool.gif

Regional dialect, it's a funny thing. .. "Oh excuse me stewardess, I speak jive ... " biggrin.gif

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post #41 of 45 Old 05-17-2013, 09:13 AM
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Quote:
Originally Posted by FOH View Post

I should've made myself more clear.

Thanks Don, good lookin' out cool.gif

Regional dialect, it's a funny thing. .. "Oh excuse me stewardess, I speak jive ... " biggrin.gif

Well good, got that clear.

Anyways, you are one who certainly doesnt have problems with max spl, headroom, dynamic range or running out of juice biggrin.gif

16.8kw ? Do your ears still function? wink.gif

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post #42 of 45 Old 05-17-2013, 02:37 PM
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Quote:
Originally Posted by jim19611961 View Post

Well good, got that clear.

Anyways, you are one who certainly doesnt have problems with max spl, headroom, dynamic range or running out of juice biggrin.gif

16.8kw ? Do your ears still function? wink.gif


As everyone likely knows;
10dB peaks require 10x power
20dB peaks require 100x power
30dB peaks require 1000x power

We listen at relatively modest levels nearly all the time. However, the ability to reproduce the phenomenal peak energy that's all too often associated with much of the content we enjoy.

Do the math to deliver ref levels at the LP, it's staggering. Then, upon examining the lowest octaves of the LF range, consider how truly unbelievable what is required to meet the "ref level @LP@20hz", then to plunge to 10hz, a quadrupling of that displacement, and a commensurate elevation of power,...it's staggering.



cool.gif

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post #43 of 45 Old 05-17-2013, 03:15 PM
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Quote:
Originally Posted by FOH View Post

Do the math to deliver ref levels at the LP, it's staggering. Then, upon examining the lowest octaves of the LF range, consider how truly unbelievable what is required to meet the "ref level @LP@20hz", then to plunge to 10hz, a quadrupling of that displacement, and a commensurate elevation of power,...it's staggering.


So driver displacement is a x4 multiplier each time your drop an octave. Can you (or anyone) please remind me what the power multiplier is each time you drop an octave? Formulae? I did see this somewhere, but it didn't sink in! rolleyes.gif
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post #44 of 45 Old 05-17-2013, 03:39 PM
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Originally Posted by GIEGAR View Post

So driver displacement is a x4 multiplier each time your drop an octave. Can you (or anyone) please remind me what the power multiplier is each time you drop an octave? Formulae? I did see this somewhere, but it didn't sink in! rolleyes.gif

There's no inherent change.

Obviously approaching driver + enclosure resonance power required to hit a given SPL goes down.

Dropping below the system's high-pass poles (two for a sealed enclosure, ultimately producing a 12dB/octave roll-off) the power for a given program SPL doesn't change apart from the impact of the driver + enclosure's impedance curve; although the power to counter the roll-off and reach a given SPL is increasing at 12dB/octave.

The astute reader will note that with the excursion limited SPL dropping 12dB/octave, a clever individual can come up with driver + enclosure + amplifier combinations which have the amplifier clipping before the driver reaches its mechanical limits so the user can have both loud bass at higher frequencies and low bass at lesser listening levels. Commercial manufacturers do this in sealed designs.

At higher frequencies where the baffle is becoming acoustically large you have decreased power requirements as the speaker's radiation transitions from half space to full space. The -3dB point is where the baffle is 3 wavelengths or 376Hz for a foot wide baffle.
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post #45 of 45 Old 05-18-2013, 05:36 AM
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That's great. Thanks for the explanation Drew.
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