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Who wants to measure how much power (voltage) is REALLY needed?


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7 hours ago, alzinski said:

 

Do you have the EQ set flat? Or do you have loudness setting on?

 

Oooops! Glancing over at the amp--I can see EQ is not flat. I'm embarrassed to say I was not conscious of this during the test... so, I need to do this again.

Thank you for spotting that.

 

I suffer from frequency specific hearing loss, and I'm nearly always correcting for my ears... With others around, I flatten it back out. What I like might be unbearable to good ears.

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Ok, with the helpful guidance of Alzinski, my second trial might yield more correct results:

 

•120 Hz: 93.0 dB at 12', 2.2 volts

•220 Hz: 91.5 dB at 12', 1.1 volts

 

Amp = YAMAHA SS, 70W+70W @ 8 Ohms; one pair '83 Cornwalls, with B3 crossovers

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Ok, I went back and read the instructions. This, taken from DIYaudio.com:

 

"Any scale 20V or lower should be OK. Meters with only 200V AC scale won't be accurate enough for this test. "

 

My meter's lowest AC setting is 200V. My results are rubbish.

 

I should be a spectator in this and not a participant. [Imagine: An NBA fan jumps out of his seat during play and, full of enthusiasm, runs down onto the court, only to embarrass himself]

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2 hours ago, mike stehr said:

That's a lot of current for 93 decibels.

 

I think that is supposed to be volts.

 

My Fluke is probably only accurate on 60Hz. Most meters are only good for a few different frequencies. A scope would be better.

 

Bruce

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^yes, thank you. I wrote "amps" where it should have read "volts" I went back and changed it. Yikes, I need to get off the court and go back to the bleachers. I fear I have crapped all over this thread, without meaning to.

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9 hours ago, Marvel said:

 

 

My Fluke is probably only accurate on 60Hz. Most meters are only good for a few different frequencies. A scope would be better.

 

Bruce

The Fluke meters offer excellent accuracy at the test frequencies, and it is rare to find meters which can't hold up when measuring a 220 Hz sine wave.

 

Maynard

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On ‎5‎/‎16‎/‎2017 at 3:27 PM, garyrc said:

I believe that PWK found that in an ordinary room, neither outside, nor in an anechoic chamber, doubling the distance caused about a 3 dB decline in SPL.  In his experiment, three doublings reduced the SPL by an average of "8 or 9 dB."   It seems this is true in the critical bass areas, as well, occasionally rising to 10 or 11 dB for three doublings.  His room (I believe) was about 16 x 24 feet, ceiling height not reported.  Most of this is in a humorous article criticizing reverberant field speakers, called "THE GREAT MAJOR BREAK THROUGH No. 29," but the curves are for real. 

 

 

In my room going from 4 ft to 8 ft drops the SPL by 6 dB. From 8 ft to 16 ft it drops 4 dB. It depends on room gain, and generally the larger the room the less the gain. Acoustic absorption also has the effect of reducing room gain.

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On 5/9/2017 at 2:11 PM, tube fanatic said:

I suspect that it is going to come as a big surprise when folks discover that they don't need 500 wpc to their K-horns for even extremely loud levels!

 

0.75V on the La Scala L&R channels

4V across the subwoofer

 

No surprise there really. B) In the past I could never tap out my previous AVR's either, much less the incredibly stout Pioneer. Even our pair of, relatively more thirsty, CAT40's required less than 2V to drive an entire block party.

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7 hours ago, Quiet_Hollow said:

 

0.75V on the La Scala L&R channels

4V across the subwoofer

 

No surprise there really. B) In the past I could never tap out my previous AVR's either, much less the incredibly stout Pioneer. Even our pair of, relatively more thirsty, CAT40's required less than 2V to drive an entire block party.

I assume that the .75V measurement was with the -12 db test tone (which frequency did you use?).  That correlates with a power need of no more than 563 MILLIwatts/channel (into 8 ohms) regardless of what recording you play at the particular volume control setting that you used.  Truly no surprise to me either.  That amount of power into LSs should provide a level of around 92 db @ 15 feet.  Certainly, that's loud enough for many listeners.  And measurements like yours explain why so many users of flea power amps with Klipsch speakers find the former to be well up to the job.

 

Maynard  

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Is 12 dB enough?  One recording I found has a 24 dB crest factor. Ravel Orchestrations. Reference Recordings.  (Am I looking at the numbers correctly?  The difference between average and maximum?)

 

I also found some Telarc recordings with about 20 dB even without cannons or dinosaurs.

 

The software is ocenaudio.  The sample and hold meters are interesting.  But . . . it seems to me show higher peaks than what the statistics report gives (by a smidge).

 

BTW, I found the error in my back of the envelope calculations. Typical stupid math error.

 

WMcD

 

 

Alborada Del Gracioso.jpg

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You can't go past 0db.

 

In your screen cap peak amplitude for channel 2 is -0.05db.

 

For dynamic range 12db isn't enough but that's not what this test is about, he could have ran the test tone at -24db and change the maths around, either way it would tell you the same thing.

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On 6/6/2017 at 5:06 AM, tube fanatic said:

I assume that the .75V measurement was with the -12 db test tone (which frequency did you use?).  That correlates with a power need of no more than 563 MILLIwatts/channel (into 8 ohms) regardless of what recording you play at the particular volume control setting that you used.  Truly no surprise to me either.  That amount of power into LSs should provide a level of around 92 db @ 15 feet.  Certainly, that's loud enough for many listeners.  And measurements like yours explain why so many users of flea power amps with Klipsch speakers find the former to be well up to the job.

220hz... just a touch over where I have the high pass set.  It also explains why I've never blown a tweeter either. :emotion-55: Suffice to say, brief exploration into the single digit territory usually warrants a change of underwear.

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Finally got around to doing this, and not sure what to make of it....

 

At the very upper edge of "loud enough" for me, which is  95db.

 

Test tones played from a laptop, thru iTunes, then input to Oppo 105D USB DAC port, out to Mcintosh C32 preamp.

 

Measured at the speaker terminals of an MC225.

 

Khorns - 4.96 vac at 120hz, 5.02 vac at 220hz (equates to almost 25 watts)

 

La Scala - 3.54 vac at 120hz, 3.62 vac at 220hz (equates to approx. 12.5 watts)

 

Belle - 3.51 vac at 120hz, 3.56 vac at 220hz (equates to approx. 12 watts)

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I ran across this today as I was reading through Dope-from-Hope articles (Vol.16, No. 1). I thought it might be of interest to anyone reading this thread. Chance to see how our individual experience squares with previous findings. I especially like PWK's notes/commentary on the left margin that describe the increasing sound levels:

 

 

Screen shot 2017-06-10 at 9.54.00 PM.png

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3 hours ago, Endo said:

I ran across this today as I was reading through Dope-from-Hope articles (Vol.16, No. 1). I thought it might be of interest to anyone reading this thread. Chance to see how our individual experience squares with previous findings. I especially like PWK's notes/commentary on the left margin that describe the increasing sound levels:

 

 

Screen shot 2017-06-10 at 9.54.00 PM.png

This is a good table.  It should be pointed out that PWK considered 115 dB as "Too damn loud" for continuous or average levels, but also said that you need 115 dB PEAKS at your ears to produce the "blood stirring" levels of a symphony orchestra.  These peaks would be very, very brief, possibly measured in milliseconds.  Sounds of this short a duration are not covered in any chart of tolerable sound pressure levels.  OSHA says that 115 dB is tolerable for 15 minutes, some other countries would say that level is tolerable for only a few seconds -- both of these durations are far longer than the leading edge of a cymbal crash, or other very brief peaks.  So, in the above mentioned 3,000 cu.ft. room, a Klipschorn could produce a pretty loud 100 dB sound with only 2 watts needed, but would need 63 watts -- just for a moment -- to produce a 115 dB peak.

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