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Amplifier Power test


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1 hour ago, jjptkd said:

 

15 years ago or so I use to throw regular house parties with my Chorus II's usually cranked so loud in the living room that the bulk of the party would migrate to the kitchen / dining room to mingle and even there would have to talk kind of loud over the music. At that time I cycled through many solid state amplifiers and determined that 200wpc would only get me to about 80% volume without hearing distortion, they would simply run out of gas. It took 300 watts minimum to be able to crank them up as loud as I wanted and still sound clear. 

Parties are for music, not talking...lol

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2 hours ago, LTusler said:

Here are my Klipsch Jubilee results.

Measured 60dBA, 402 Horn w/AXI 2050, .18V

Measured 82dBA, 402 Horn w/AXI 2050, 2.7V

Measured 60dBA, KPT-KHJ-LF, .14V

Measured 82dBA, KPT-KHJ-LF, 1.8V

 

 

 

Very good thank you!

 

The 402 horn average power is an astonishing 33mW of power

KPT-KHJ-LF average power is also astonishingly low at 20mW

 

Your maximum power values I will write out for 8 ohms, same as above, if anyone wants to be prudent just double the power level for 8 ohms to be safe and that will be the power needed for 4 ohms.

 

402 horn maximum power is 7.29 watts

KPT-KHJ-LF maximum power 3.24 watts

 

 

As I mentioned even if you doubled for a 4 ohm load you are looking at a 15 watt amplifier that will drive your Jubilee's to the maximum level you established. Hopefully this gave you some insight or you may have already known this. Either way thank you so much for contributing to the database.

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You're quite welcome.  Yes they are all 8 ohm.

 

So I guess the 2 QSC PLX1104's powering the horns and bass bins are adequate!  Plus the 2 Sunfire True Subs make for a nice sounding system.

 

Thanks for you input. 

Time to put the beer ears on!

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2 hours ago, captainbeefheart said:

 

Very good thank you!

 

The 402 horn average power is an astonishing 33mW of power

KPT-KHJ-LF average power is also astonishingly low at 20mW

 

Your maximum power values I will write out for 8 ohms, same as above, if anyone wants to be prudent just double the power level for 8 ohms to be safe and that will be the power needed for 4 ohms.

 

402 horn maximum power is 7.29 watts

KPT-KHJ-LF maximum power 3.24 watts

 

 

As I mentioned even if you doubled for a 4 ohm load you are looking at a 15 watt amplifier that will drive your Jubilee's to the maximum level you established. Hopefully this gave you some insight or you may have already known this. Either way thank you so much for contributing to the database.

How are you calculating power?

Why not W=(V^2) / 8 ?

which would be

4mW and 2.45mW averages,

0.9W and 0.4W maxiums

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6 hours ago, LTusler said:

Here are my Klipsch Jubilee results.

Measured 60dBA, 402 Horn w/AXI 2050, .18V

Measured 82dBA, 402 Horn w/AXI 2050, 2.7V

Measured 60dBA, KPT-KHJ-LF, .14V

Measured 82dBA, KPT-KHJ-LF, 1.8V

 

 

More power going into mid and high frequencies than the lows? This surprises me.

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5 hours ago, pauln said:

OK, but your figures appear to be 9db higher than mine... where is the other 3dB?

 

Say you measure 1.8v

 

1.8*4= 7.2

 

7.2/1.4 = 5.14 rms

 

5.14^2= 26.44

 

26.44/8= 3.3 watts

 

The math works out for an 8 ohm load to just square your voltage measurement.

 

1.8*1.8= 3.24

 

EDIT: the error difference of .06v was because I used 1.4 as the voltage ratio of -3db (RMS) which is rounded off and creates the very slight error.

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25 minutes ago, geezin' said:

I'm having trouble with meters. Damn. Need to get now test leads for the good one. Oh well.

 

This is a Klipsch forum so the majority of us are running crazy efficient speakers, this may put a lot of you in the region where a meter that only has a 200v scale just will not work. Over to diyaudio there are many different people using many different speakers including power hungry audiophile types so more people over there got away with 200v scale meters.

 

If any members are in New England and want to have a beer I'll bring my meter over and help with the test. Or if anyone that doesn't have a good meter and has an electrician as a friend or in the family they'll be happy to lend you one of theirs as they most likely have multiple multimeters, say that fast 20 times 🙃

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On 2/23/2022 at 9:40 PM, 314carpenter said:

Sounds defensive. Didn't think my post implied offensive connotations. It was about the math. Relax. Where's my participation trophy?

I do believe yer toaster wuz held up at the border…..

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2 hours ago, babadono said:

More power going into mid and high frequencies than the lows? This surprises me.

 

Glad I am not the only one that thought that was strange, that or I didn't understand what he was labeling where he was measuring.

 

I should maybe add for people to set their EQ to flat. I take for granted people know that and shouldn't.

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1 hour ago, captainbeefheart said:

 

Say you measure 1.8v

 

1.8*4= 7.2

 

7.2/1.4 = 5.14 rms

 

5.14^2= 26.44

 

26.44/8= 3.24 watts

 

The math works out for an 8 ohm load to just square your voltage measurement.

 

1.8*1.8= 3.24

 

That 1.8V is what the file produces when the volume is set to one's maximum digital media listening level. The listened level is an rms voltage corresponding to standardized ballistics (called "Fast" or "Peak" on meters designed for monitoring radio modulation of adult male "announcer voice" for commercial broadcast a very long time ago. Its ballistics accumulate energy about the rate of spoken syllables, which is what vu meters, spl meters, and watt meters display). There are at least 13dB additional dynamics above that level (instantaneous transients) that don't show up in the meters.

 

But the file is a sine wave. It is also rms but does not have any instantaneous transients - if the file is down 12dB in order to present the range to 0dB as the overhead for transients, it is not enough.

 

Why is 1.8V multiplied by 4?

 

Dividing by 1.4 is converting from peak to rms but the measurement is already rms when read.

 

Can you show the actual calculation with an explanation of all the numbers and units?

 

.

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19 minutes ago, pauln said:

That 1.8V is what the file produces when the volume is set to one's maximum digital media listening level. The listened level is an rms voltage corresponding to standardized ballistics (called "Fast" or "Peak" on meters designed for monitoring radio modulation of adult male "announcer voice" for commercial broadcast a very long time ago. Its ballistics accumulate energy about the rate of spoken syllables, which is what vu meters, spl meters, and watt meters display). There are at least 13dB additional dynamics above that level (instantaneous transients) that don't show up in the meters.

 

But the file is a sine wave. It is also rms but does not have any instantaneous transients - if the file is down 12dB in order to present the range to 0dB as the overhead for transients, it is not enough.

 

Why is 1.8V multiplied by 4?

 

Dividing by 1.4 is converting from peak to rms but the measurement is already rms when read.

 

Can you show the actual calculation with an explanation of all the numbers and units?

 

Anything you can think of to ask has been covered here: https://www.diyaudio.com/community/threads/a-test-how-much-voltage-power-do-your-speakers-need.204857/

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I can express the math a different way for you.

 

The maximum rms power from a sine wave is -3db and the recording is already at -12db then we need to gain +9db

 

That's a voltage difference of 2.83

 

Now you can multiply your test voltage by 2.83, square it  and divide by load

 

For the 1.8v example

 

1.8*2.83= 5.094

 

5.094*5.094= 25.94

 

25.94/8= 3.24

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3 hours ago, captainbeefheart said:

I looked over there including the FAQ; it looks like the assumption is that +12dB is assumed to be enough dynamic headroom to not clip, but +12dB over what level? Average level or metered "fast"/"peak" level?

 

I know, its -12dB down from full scale, but that is not enough.

 

If +12dB over average, that is actually the middle of the range of recorded dynamic range (metered fast/peak over average) which means for the half of recordings that exceed that there is no more margin, and does not begin to include the additional 13dB required for transients.

 

If +12dB over metered fast peaks, the transients are still not being fully powered.

 

I think the dB level for the test file needs to be more like about -30dB in order to account for recordings with up to +18dB dynamic headroom above average and +13dB more for transients. This would cover just about everything except test recordings and those from a handful of specialty studios.

 

The assumption that the listening levels are not clipping perhaps is not being met.

 

Off to play records with milliwatts in the teens... :)

 

edit... The more I think about it, the more I think I may be incorrect. Maybe the -12dB level of the file is arbitrary, just a way to calculate what the listened level power would be at full scale in order to access rated power required. 

 

 

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