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post #1 of 36 Old 05-20-2012, 06:19 AM - Thread Starter
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i have speakers rated at 250 watts max...

i have an amp rated at 500 wpc...

trouble on the horizon?
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post #2 of 36 Old 05-20-2012, 06:35 AM
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no, not unless you drive your amp to absolute maximum. What model amp to you have ? 500 wpc sounds like a "peak" or "music power" rating, not an RMS rating ????
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post #3 of 36 Old 05-20-2012, 06:46 AM - Thread Starter
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amp in question is a rotel rb-1092...speakers are focal 836w's


i am interested in this combo in particular...but speaking in general as well
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post #4 of 36 Old 05-20-2012, 06:50 AM
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An amp more powerful than the speaker rating only damages speakers when you turn it up too loud, at which point you'll probably hear the distortion.

You don't turn the water on full blast to fill a juice glass. The amp will only put out what you tell it, whether rated 10 W or 1000 W.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #5 of 36 Old 05-20-2012, 07:00 AM - Thread Starter
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Quote:
Originally Posted by DonH50 View Post

An amp more powerful than the speaker rating only damages speakers when you turn it up too loud, at which point you'll probably hear the distortion.

You don't turn the water on full blast to fill a juice glass. The amp will only put out what you tell it, whether rated 10 W or 1000 W.



which raises another question...

one amp rated at 200 wpc...

one rated at 500 wpc...

both are played at "reference" -10...would i assume correctly that neither amp is close to an output near their respective power rating...?
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post #6 of 36 Old 05-20-2012, 07:08 AM
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Pretty safe assumption... I a medium sized room, you might just reach reference maxing each the Focals at 300W, so 10 dB below that is 30W peaks.

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post #7 of 36 Old 05-20-2012, 07:21 AM - Thread Starter
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so then...

cranking the 500 wpc amp to "reference" would put the 250 watt speaker at "high risk" probabilities...?
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post #8 of 36 Old 05-20-2012, 07:34 AM
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^^^

no...

"reference" is a defined spl level... it really has nothing to do with "cranking the amp up all the way"...

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post #9 of 36 Old 05-20-2012, 07:40 AM - Thread Starter
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"reference" i used...


"cranking the amp up all the way"... i didn't
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post #10 of 36 Old 05-20-2012, 07:51 AM
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it does not matter whether it's a 500 watt or a 50 watt amp, really...

either the speakers (given enough power, which is highly dependent upon sensitivity) will produce a reference spl at a given distance, or they won't...

a 100db sensitivity speaker will push reference spl in a "normal room" with very little power...

an 83db sensitivity speaker will likely not, even if you hook a nuclear reactor up to it... in all likelihood, the speaker will meltdown if you even try...

of course, once you cross them to a sub, you are alleviating a big portion of the power demands...

also, VERY few listen at anywhere close to "reference level"... some do, but they are few and far between....

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post #11 of 36 Old 05-20-2012, 09:06 AM
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Quote:
Originally Posted by lefthandluke View Post

so then...

cranking the 500 wpc amp to "reference" would put the 250 watt speaker at "high risk" probabilities...?

Yeah, in all likelihood reference is near the max capability of your speakers. It's a fair assumption that you might bottom out the woofers with the 500 W amp, not that you wouldn't be risking damage with a 250W amp.

Play around with an SPL calculator and see:

http://myhometheater.homestead.com/splcalculator.html

92 dB sensitivity, 300 W into one speaker 15 feet away, consider wall gain and you get 106.6 dB, pretty close to 105 dB.

I think you are fine at 10 dB below... No need to ever rush to the volume control to turn it down. As long as the sub is good for reference minus 10 dB (105 dB plus any bass management add-ons)

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post #12 of 36 Old 05-21-2012, 03:09 AM - Thread Starter
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so at those high levels, the woofers are more vulnerable than mids or tweets, or are they all equally at risk...?
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post #13 of 36 Old 05-21-2012, 04:37 AM
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They're all vulnerable in one way or another.
Woofers are most vulnerable to "bottoming out".
Tweeters have more fragile magnet coils than do midrange speakers.

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post #14 of 36 Old 05-21-2012, 07:30 PM - Thread Starter
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just wondering how speaker ratings are dished out...

my previous speakers had 1" aluminum tweeters and 6" mid/woofs...rated at 500 watts max

present speakers have 1" alum/magnesium tweet and 6 1/2" mid woofs...rated at 250 watts max

what's the determining factor as to max power ratings...?
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post #15 of 36 Old 05-22-2012, 04:48 AM
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The electro-mechanical design of the speaker drivers determines the maximum power they can handle. Simplistically, heavier gauge wires in their electromagnets can carry larger currents and thus more power, for example, while the placement of those magnets determines how great their excursion can be, and thus the volume of the sound.

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post #16 of 36 Old 05-22-2012, 05:11 PM - Thread Starter
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well...looks like if i use the 500 watt amp i need to use caution. my integra processor allows me to set "maximum volume"...maybe just setting at -10 would do the trick.


downside of that scenario being the wide variations of mastering levels used in music AND movies...
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post #17 of 36 Old 05-22-2012, 06:13 PM
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I think you're still missing the big picture. You are not going to overdrive your speakers due to a "higher rated amp" unless you are really foolish or deaf. Your speakers will start to distort and this will be very audible. Your speakers are rated at 92 db sensitive@ 1 watt/meter so with every doubling of power you add 3 db (if i've read all these other posts right!), so using half of your amps rated power (256 watts) you would be pushing 116 db@ 1 meter from your speakers. That might translate to 105 db at the listening position. The question is: Are your speakers capable of handling this? I can't answer that, but i'll assume many on here can. I know my previous speakers (swan diva 6.2's) were rated 92 and cannot handle reference cleanly without distortion. There is a thread on here about high sensitivity reference style speakers. Another question you should not ignore was asked earlier: Are you going to ever listen at reference? It's loud. Especially more so if you do not have a treated room. With a properly treated room, reference can sound great. Without, it will make your ears bleed. Like a previous poster suggested: Get a spl meter and see what levels you like listening at.
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post #18 of 36 Old 05-22-2012, 07:39 PM - Thread Starter
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well, you guys make some good points...


but i have spent a lotta time treating my room and i do use a spl meter and have run audyssey xt32...reference IS loud, but does sound clean and exciting

now, don't get me wrong, i NORMALLY listen anywhere from -25 to -10, depending on material...and mood. but on occasion (usually every 5-6 weeks or so) i have a group of friends over for what we call "music-fest"...and as the evening progresses, the enthusiasm and the volume seems to increase in kind. i control the remote, but i still am concerned about the speakers ability to handle even short term reference levels.
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post #19 of 36 Old 05-22-2012, 07:57 PM
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Quote:
Originally Posted by lefthandluke View Post

so then...

cranking the 500 wpc amp to "reference" would put the 250 watt speaker at "high risk" probabilities...?

No. Movie sound tracks with a lot of dynamic range have 27-31dB difference between average and peak levels and voice coil temperature has more to do with the average level which takes a tiny fraction of a Watt.
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post #20 of 36 Old 05-22-2012, 08:24 PM
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Quote:
Originally Posted by lefthandluke View Post

just wondering how speaker ratings are dished out...

my previous speakers had 1" aluminum tweeters and 6" mid/woofs...rated at 500 watts max

present speakers have 1" alum/magnesium tweet and 6 1/2" mid woofs...rated at 250 watts max

what's the determining factor as to max power ratings...?

What it takes to melt something (the voice coil, the glue connecting it to a tweeter dome, etc.) using an IEC test signal consisting of pink noise with a 6dB crest factor, 12dB/octave high-pass at 40Hz, and 12dB/octave low-pass at 5KHz which they claim to represent an average musical signal.

Caveats are that

1. You can melt tweeter parts long before that with non-musical signals, like if you keep turning up the volume once the system is clipping (the frequencies with more power clip first and stop getting louder; but the high frequencies with less power keep getting louder).

2. You can usually run your speakers out to their mechanical limits (which can cause permanent damage if the drivers are designed such that the voice coil former hits the motor back plate before the spider limits travel) long before that.

Here are a few maximum linear SPL numbers 1 meter from the speaker - at your listening position loudness is likely to be 6dB less.

Size Driver Sd (cm^2) x xmax (mm) 80Hz 40Hz 20Hz
6 1/4" Seas L16RN-SL 104 x 6 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 95dB 83dB 71dB

The Seas W18 has xmech of 19mm peak-to-peak; or another 5.6dB before it bottoms.

Since the W18 is an 88dB sensitive driver, it will reach its mechanical limits given a 12.1V input at 80Hz (18W into 8 Ohms) and 3V at 40Hz (1.1W into 8 Ohms).

Actual power consumed reaching the mechanical limits is less since impedance rises as a speaker approaches resonance.
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post #21 of 36 Old 05-22-2012, 08:34 PM
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Quote:
Originally Posted by chrischaos View Post

I think you're still missing the big picture. You are not going to overdrive your speakers due to a "higher rated amp" unless you are really foolish or deaf. Your speakers will start to distort and this will be very audible. Your speakers are rated at 92 db sensitive@ 1 watt/meter so with every doubling of power you add 3 db (if i've read all these other posts right!), so using half of your amps rated power (256 watts) you would be pushing 116 db@ 1 meter from your speakers. That might translate to 105 db at the listening position.

It'll probably be more like 110dB at the listening position, since domestic rooms tend to have a 3dB/distance doubling draw-down factor (4 meters, 13').

Quote:
The question is: Are your speakers capable of handling this? I can't answer that, but i'll assume many on here can.

Most can't. The 7" Seas in my example will reach its linear limits when delivering about 90dB at 80Hz (or 96dB with an 80Hz sub-woofer cross-over).

Quote:
Are you going to ever listen at reference? It's loud.

You'll get there listening to well-recorded jazz with an 85dBC average SPL which isn't that loud (but might sound that way with distorting speakers).
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post #22 of 36 Old 05-22-2012, 08:37 PM
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Quote:
Originally Posted by lefthandluke View Post

so then...

cranking the 500 wpc amp to "reference" would put the 250 watt speaker at "high risk" probabilities...?



What the hell does "reference " mean?????
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post #23 of 36 Old 05-22-2012, 08:45 PM
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Originally Posted by PHOSCHEKER View Post

What the hell does "reference " mean?????

Dialog at 74dB SPL, main channel peaks up to 105dB (101dB with typical Dolby Digital encoder settings), and LFE peaks to 115dB (111dB).
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post #24 of 36 Old 05-22-2012, 09:11 PM
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What tool is used to find out how many watts an amp is pushing out at any given volume to a speaker?

AVR: Onkyo 3009...Onkyo 609 (Old)
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post #25 of 36 Old 05-22-2012, 09:35 PM
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It's different for every room and speaker

Good place to start
http://www.crownaudio.com/apps_htm/d...ct-pwr-req.htm

No subwoofer I've heard has been able to produce the bass I've experienced in the Corps!

Must..stop...buying...every bluray release...
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post #26 of 36 Old 05-22-2012, 09:37 PM
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Quote:
Originally Posted by freeyayo50 View Post

What tool is used to find out how many watts an amp is pushing out at any given volume to a speaker?

Arithmetic.

Power = 10 ^ ((loudness at 1 meter - efficiency in dB/1W/1 meter) / 10)

Real rooms tend to a 3dB/distance doubling draw down rate from point source approximations; so loudness at 1 meter is 10 log distance (in meters) dB higher than at the listening position.

With typical listening positions in the 2 (6.6 feet) - 4 meter (13.1 feet) range the sound looses 3-6dB getting to you,
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post #27 of 36 Old 05-22-2012, 09:54 PM
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Quote:
Originally Posted by pokekevin View Post

It's different for every room and speaker

Good place to start
http://www.crownaudio.com/apps_htm/d...ct-pwr-req.htm

The calculator is very wrong (off by a factor of 8 for a 4 meter seating distance for our discussion purposes) except for people listening out doors or in anechoic chambers who are not interested in the power needed to achieve reference level home theater.

_Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms_ summarizes various studies showing that indoor listening space volume neither looses 6dB per distance doubling nor acts like a diffuse field. It looses about 3dB.

To use the calculator for indoor use one should take the square root of the listening distance (ex : square root of 2 = about 1.4, 4 = 2) and use that.

Reference level home theater assigns a SPL to 0dBFS, which is the highest possible signal with a 0dB crest factor. Consumer amplifiers are rated using sine waves with a 3dB crest factor (a sine wave with 100W RMS power into 8 Ohms has a 28.3V RMS voltage with peaks at 40V and therefore peak power 200W).

To apply the calculator to power required for digital movie sound tracks you must consider this and get rid of its headroom compensation which has already been accounted for by adding 3dB to the speaker sensitivity rating box and setting the Amplifier Headroom box to 0dB (all negative values are treated as zero).

It takes less power than you'd think.

After reading Siegfried Linkwitz's opinion that rooms were like diffuse fields (once you get past the critical distance where direct sound and reverberant field strengths are equal the total SPL can't drop more than 3dB; with 2-4 feet matching the directivity index of typical speakers) I got curious and made some measurements with sub (corner loaded) and center (on a short stand 3' off my screen wall) both with claimed sensitivity a bit over 90dB/2.83V/1 meter and nominal impedance around 6 Ohms. My room was 13x19x8' with big openings to the rest of the house, seating 11' off the screen wall. The sub was about 12' away and center 9' away measured to the drivers. The sub was a Citation 7.4 with a 14.5" driver in a ~3 cubic foot ported box and should be typical for reasonably sized subs; the center a Definitive C1 which should be typical for a medium consumer market sized MTM speaker. I used my Rat Shack SPL meter with C-weighting so sub-output may be a little under reported. I used an HP true RMS volt meter which is spot on at no worse than -2% against the calibration terminal on my Tek scope which is .17dB. The sub tune is around 30Hz so the voltage within the sub's pass-band may be over-reported (pink noise has equal power in each octave and I'm missing at least part of one, and I never looked at the frequency spectrum from my Lexicon DC-1 to see where its cutoff was). Any errors led to sub sensitivity being measured as less than it really was. Extrapolation to reference level output disregards thermal compression although the Citation 7.4 uses a JBL pro-sound driver with a 4" voice coil and shouldn't suffer too much arround just 100W.

My mains were actively tri-amplified dipoles that would be too messy to make sense of so I didn't measure them.

I measured .88 VRMS for pink noise at 75dB SPL (at my listening position) from my 6 Ohm center which is .13W. A 101dB peak (reference level Dolby Digital main channel maximum with typical encoder settings) would take 50W; although that's 0dBFS and could be done with an amplifier rated at 25W into 6 Ohms or 19W into 8 Ohms.

I measured .34 VRMS to produce pink noise at 76dB SPL (at my listening position) from my 6 Ohm corner loaded sub-woofer which is .02W. A 101dB peak would take 6W, 111dB (reference level Dolby Digital LFE maximum with typical encoder settings) 60W; although that's 0dBFS and could be done with an amplifier rated at 30W into 6 Ohms or 23W into 8 Ohms.

In my room, 125W and 150W respectively would get me a full 105/115dB on a potential DTS track track with the volume knob in the same position and take amplifires good for 47W and 56W into 8 Ohms for center and sub.

LFE headroom is 10dB over the screen channels so the voltage is 10 ^ (10/20) = 3.2 times each screen channel and mixing in five screen channels with correlated bass (and nothing else happening!) could boost the sub-woofer output by 20 log ((3.2 + 5) / 3.2) = 8.2dB or multiply the power requirement by 10 ^ (8.2/10) = 6.6X thus suggesting a sub-woofer amplifier good for 370W into 8 Ohms.
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post #28 of 36 Old 05-22-2012, 10:07 PM
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Whats more important is the damage you do to you're hearing listening at sustained levels that high.
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post #29 of 36 Old 05-22-2012, 10:30 PM
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Quote:
Originally Posted by ccotenj View Post

of course, once you cross them to a sub, you are alleviating a big portion of the power demands...

That's a myth for music.

Some one with more interest could extract motion picture sound tracks and see how they work in practice. If some one wants to rip screen channels to .wav files I'll provide the GNU Octave/Matlab commands that will show the average and peak power decrease using a sub-woofer cross-over.

The IEC musical power spectrum approximation has a second order high-pass at 40Hz and second order low-pass at 5KHz or about 7 octaves with significant energy.

About 1/7th of that would be sent to a sub-woofer in a musical system which is inconsequential for power requirements (but _very_ significant for bass driver excursion).

Quote:


also, VERY few listen at anywhere close to "reference level"... some do, but they are few and far between....

The vast majority of consumer speakers are audibly distressed when people try.
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post #30 of 36 Old 05-22-2012, 10:34 PM
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Quote:
Originally Posted by oztech View Post

Whats more important is the damage you do to you're hearing listening at sustained levels that high.

Reference doesn't involve sustained levels that high. Reference level dialog (and therefore the average level) is only 74dB SPL.
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