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THD % at rated continuous power.

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Hello.

 

Does anyone know what is the percentage of THD at Klipsch's rated continuous power for their speakers?

 

Personally, I've got three R-51M that I'm running as front channels for movies.

With a voltage output at 0 dBFS RMS as 12.35 Vrms per speaker, what amount of distorsion might there be?

 

Thank you.

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Doesn't matter what the amount is. As long as you don't clip the amp, you are ok. Don't get hung up on specs, listen with your ears.

 

Shakey

 

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22 hours ago, Frontino said:

Hello.

 

Does anyone know what is the percentage of THD at Klipsch's rated continuous power for their speakers?

 

 

Thank you.

is that even a knowable factor?

THD% is a factor for amplification.

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And, please explain farther or reprhase your question as to what you are actually looking to find.

Welcome!

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23 hours ago, Frontino said:

Does anyone know what is the percentage of THD at Klipsch's rated continuous power for their speakers?

In general, this isn't a single number, but a curve of THD vs. frequency...like the following plot:

 

139474548_TADJubiileeTHDvs.Frequency100dB.jpg.8853940f6e4c507531ee035ceae7345e.jpg

 

The harmonic content of the THD figure is likely dominated by second harmonic distortion (as it almost always is, which itself is almost inaudible as harmonic distortion only, but not as an indicator of modulation distortion).

 

If the R-51M sensitivity is actually about 90 dB @ 2.83v (Klipsch stated sensitivity ratings are consistently between 3 and 6 dB overstated). Then at 12 volts input --this corresponds to about 96 dB on axis at one metre.  My guess is that you're looking at between 1% and 10% THD at that voltage level, but I don't have an R-51M to test.  I'd use the figure of 10% THD at 2.83v as a general rule of thumb.  Almost all of the distortion will be from the small woofer in the R-51M.

 

Chris

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 @Chris A 

Chris,

if I read your graph correctly you measured with a sound volume of 100dB but the distance is not mentioned. As the sensitivity of the Jubilee is around 105db it is reasonable to assume your input power was around 1 Watt maybe a little more. 

If one is to inject a sine wave of 12Vrms to measure the THD over the frequency range of the R-51M speaker this corresponds to an input power between 18 and 36 Watts (8 to 4 ohm) I'm quite sure that poor tweeter will have a short life in the course of that test. 🙂

 

 

 

 

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49 minutes ago, JefDC said:

if I read your graph correctly you measured with a sound volume of 100dB but the distance is not mentioned...

 

I pretty much always take my measurements at 1 m--all of them.  Sometimes I'll move the microphone back to the listening position for subwoofer EQing, but that's the only time I'll usually do that. I dial-in the subwoofer-->bass bin time delay/polarity using 1m microphone spacing, since the subs are directly behind the Jubs.  There are good reasons for this.  In general, don't take measurement from the listening position--because you can't isolate the non-minimum phase reflections if you do.  This is actually the Achilles heel of "room correction software" why so many people have so much trouble with using those applications.

 

49 minutes ago, JefDC said:

As the sensitivity of the Jubilee is around 105db it is reasonable to assume your input power was around 1 Watt maybe a little more. 

I think you're getting "lost in the metaphor" here.  I posted the first REW file that I could find that was calibrated at higher SPL on-axis.  The measurement is a pretty old one that I generally don't refer to nowadays.  For that measurement, I'm not sure that I had enough absorption on the floor to intercept the floor bounce, and I might have been dealing with connectivity issues within REW and the PC that created harmonics and other overload conditions during the sweep, etc. So again, I wouldn't read much into anything that I posted on the Jubilee at 100 dB.  If you want that info, then I recommend starting a thread on that subject (i.e., not this one) and ask the question there.

 

49 minutes ago, JefDC said:

If one is to inject a sine wave of 12Vrms to measure the THD over the frequency range of the speaker this corresponds to an input power between 18 and 36 Watts (8 to 4 ohm) I'm quite sure that poor tweeter will have a short life in the course of that test. 🙂

The tweeter won't see that power, however, but the woofer does, and the passive crossover network also sees that power.  It's like driving your car by pressing down on the accelerator, then using the brake to modify the speed.  That's not a very good way to do things--but most "audiophiles" think there is no other way to do it.  That's the greater part of the downside of passive crossovers.  They usually eat a lot of power--or they store it and try to give it back to the amplifier output at the wrong times (reactance).  That's why direct coupled drivers/tri-amping or bi-amping using DSP crossovers is a far superior way to drive loudspeakers--and the ear usually concurs...

 

Chris

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On 20 April 2021 at 5:10 PM, Chris A said:

 

If the R-51M sensitivity is actually about 90 dB @ 2.83v (Klipsch stated sensitivity ratings are consistently between 3 and 6 dB overstated). Then at 12 volts input --this corresponds to about 96 dB on axis at one metre.  My guess is that you're looking at between 1% and 10% THD at that voltage level, but I don't have an R-51M to test.  I'd use the figure of 10% THD at 2.83v as a general rule of thumb.  Almost all of the distortion will be from the small woofer in the R-51M.

 

Chris

Thanks to all of you for your inputs.

 

According to my math, from 2.83 to 12.35 V there should be a 12.8 dB gain, no?

 

Considering that I get 85 dBC per speaker with Dolby's noise at 1 meter with my RX-V381 set to -9.5 and that full scale sine wave at 2.83 V stands at -22.3, what are the chances that the R-51M is already going into power compression at 0 dBFS?

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2 minutes ago, Frontino said:

...what are the chances that the R-51M is already going into power compression at 0 dBFS?

Very likely.  But it will probably only do this at woofer frequencies using R-51M bookshelf loudspeakers.  If you buy yourself a UMIK-1 and plug it into your USB bus (after loading the shareware Room EQ Wizard), then you can see the effects of SPL on harmonic distortion and on power compression by taking in-room measurements with the microphone at 1 metre from the front of each loudspeaker under measurement (measurements taken one loudspeaker at a time). Once you plot the SPL at a lower SPL, you can measure at 0 dBFS, then move the trace downwards (using the "Controls" menu on the plot, and "trace arithmetic") to subtract the relative SPL measurement difference to match the lower SPL trace to directly read the degree of power compression that you're getting.

 

Chris

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On 21 April 2021 at 6:16 PM, Chris A said:

Very likely.  But it will probably only do this at woofer frequencies using R-51M[...]

 

Chris

With the movies I tested so far at reference (Ad Astra, Tenet and Annihilation), the unpleasant resonances I hear come mostly with nasal sillables from both female and male voices and with music passages through midhigh octaves (so, above 1K).

 

Considering that the R-51M stand along the front border of a MDF desk in an untreated room, do you think those factors could be more influencial than high voltage transients?

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Well, the crossover frequency from the woofer to the compression driver is 1660 Hz.  That means that the second harmonic of the woofer can be as high as 3320 Hz (and as low as 120 Hz), third harmonic as high as 4890 Hz (and as low as 180 Hz), and fourth harmonic as high as 6640 Hz (and as low as 240 Hz), etc. These higher harmonic frequencies are generally above the fundamental frequency of most instruments and voices.  The sibilance syllables are in the 4-8 kHz region, so you're probably hearing higher order harmonic distortion of the woofer--higher than third harmonic distortion frequencies.

 

Additionally, modulation distortion will be quite prevalent up to that 1660 Hz, forming side bands around the higher frequencies that play simultaneously (the difference and summed frequencies at the second frequency f2, shown below), thus leading to a thick and opaque sound up to the 1660 point (which happens at the same time the loudspeaker is also producing harmonic distortion):

 

csm_distorted_two-tone_signal_24b8d2b0fc.jpg

 

More on this subject here:

 

And a fairly famous paper on that subject of "The Mud Factor" by Paul Klipsch:  https://community.klipsch.com/applications/core/interface/file/attachment.php?id=162634

 

(Note: horn-loaded acoustic drivers simply do not have modulation distortion like direct radiating acoustic drivers---which is something that almost all loudspeaker reviewers miss.)

 

On 4/22/2021 at 2:25 PM, Frontino said:

Considering that the R-51M stand along the front border of a MDF desk in an untreated room, do you think those factors could be more influential than high voltage transients?

Well, not having boundary gain supporting the R-51M woofers is going to be a fairly big factor, and pushing the R-51Ms back to the rear wall (and re-EQing them to flat response) will delay the point of transition to overwhelming harmonic and modulation distortion by few dB and a few Hz.  I'd certainly try putting the R-51Ms into boundary gain, if possible.  You can also form an artificial backstop touching the back of the loudspeakers with a "false corner" or a little wall just behind the loudspeaker.  Any size of this backstop up to about 56 inches (1/4 wavelength at 60 Hz) would help the sound quality at higher SPL.

 

Chris

 

 

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I forgot to mention that I set speaker distance manually in my AVR (with active sub channel, but nothing connected, because I hate low frequencies and also because it's the only way to apply crossover to all 3 front speakers).

 

Could that lead to unnatural phase response for the speakers, since adjusting the distances in the AVR changes the phase of each channel?

 

I ask that because, if phase is frequency dependent for speakers, wouldn't changing the phase in the AVR (by setting distance) cause phase issues depending on type of sounds in the soundtrack?

 

Do cinemas adjust speakers phase  too?

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On 4/24/2021 at 2:12 PM, Chris A said:

Well, not having boundary gain supporting the R-51M woofers is going to be a fairly big factor, and pushing the R-51Ms back to the rear wall (and re-EQing them to flat response) will delay the point of transition to overwhelming harmonic and modulation distortion by few dB and a few Hz.  I'd certainly trying putting the R-51Ms into boundary gain, if possible.  You can also form an artificial backstop touching the back of the loudspeakers with a "false corner" or a little wall just behind the loudspeaker.  Any size of this backstop up to about 56 inches (1/4 wavelength at 60 Hz) would help the sound quality at higher SPL.

 

Chris

 

 

 

Just to confirm that approach with my RF42IIs. Tried that years ago, and it makes the difference.

Still not quite right, but much more listenable speakers than placing them further in the room like most audiophiles with their mini monitors do. Boundary gain is noticeable.

 

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I looked into the specifications sheet of the powered model R-51PM and it says the following:

 

MAX OUTPUT 107.3 dB

TOTAL SYSTEM POWER 120W Total System Power (140W Peak) 60W per channel cont. @ <%1 THD

 

Considering that the R-51M are rated at 85 W of continuous power, what kind of performance should I expect at 12.5 V input?

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This is the fundamental + harmonic distorsion of the R-41M. Does it look good? How much could the R-51M best that? Do you know where I can find a similar measurement for the KL-650-THX?

image.png

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My comment...as per your request:

 

That rise in harmonic distortion at 200-300 Hz looks like an issue.  I don't know what that is.  It could be a measurement issue. 

 

If it isn't a measurement issue, then it would be a pretty interesting woofer/box issue that would likely be audible at the 95 dB (on-axis--and I assume the microphone is at one metre from the loudspeaker). 

 

The data sheet on the R-41M (https://d2um2qdswy1tb0.cloudfront.net/product-specsheets/R-41M_Spec-Sheet_v01.pdf) mentions that the crossover frequency is 1730 Hz, so that harmonic distortion (HD) is solely in the domain of the woofer and its box. 

 

I would say that the R-41Ms are really suited for lower level listening as compared to other/larger Klipsch loudspeakers, based on the above measurement.  Having harmonic distortion levels that are only 30 dB down (at 95 dB on axis at 1m) indicates to me that there are also pretty audible modulation distortion issues that would be audible at the 200-300 Hz (about an octave below A440 tuning fork frequencies) and above--up to the crossover frequency of 1730 Hz.

 

Chris

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Some of the answers to the OP's question are funny. Speakers don't cause distortion or it doesn't matter how much or what type-----I don't care who you are that there is FUNNY.

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