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WMcD

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 It will take a year of discretionary spending to build up the parts but I'd like to build an F6.  I thought I'd get NP's thoughts.

 

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From me to NP with re: Sensitive Speakers and Sweet Spots. (August 2018)

 

Dear Pappa,

Thank you for all the DIY articles and opportunities to learn.  I have a question about sensitive speakers and sweet spots, if you have the time.

I have Klipsch LaScalas.  You might know their input impedance goes down to 4 ohms in the bass region.  The midrange is about 10 ohms at the driver but the crossover uses an autotransformer and so the impedance roughly doubles.  Midrange impedance goes even higher on other models (to reduce sensitivity).   And, importantly, for the LaScala, Belle, and K-Horns, sensitivity is 104 dB/watt/meter. 

To steal a line from Olsher, “The first milliwatt is the most important.”  Well, maybe the first 10 milliwatts.  And I think a microwatt is audible in theory.

So.  I’m serious about building an F6 and have enjoyed reading your thoughts on the benefits of second harmonic distortion and also your thoughts on “sweet spots.”  Question: Are the characteristics of the F6 amp and these speakers such that we’re away  from a harmonic sweet spot.  If so, do you have any suggestions?  Maybe bi-amping with single ended for the mid? Resistors?

 

I'd like to share whatever you have to say with the Klipsch Community where you have fans.  Okay?

Thank you again.

WMcD

 

 

 - - - - - - 

From NP:

 

F6 works great with La Scala’s, in fact the biggest FW dealer uses those

loudspeakers.  If you follow the threads on the F6 on DIYaudio you will see

discussion on the adjustment of the potentiometers in the circuit so as

to be able to adjust the harmonic distribution arbitrarily - the source of much

entertainment.

 

Of course I’m happy to share anything with Klipsch fans....

 

End of message from NP.

 

 

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This should work with either color scheme (and this exchange is so cool, thank you @WMcD for posting it!):

 

From me to NP with re: Sensitive Speakers and Sweet Spots. (August 2018)
 
Dear Pappa,
Thank you for all the DIY articles and opportunities to learn.  I have a question about sensitive speakers and sweet spots, if you have the time.
I have Klipsch LaScalas.  You might know their input impedance goes down to 4 ohms in the bass region.  The midrange is about 10 ohms at the driver but the crossover uses an autotransformer and so the impedance roughly doubles.  Midrange impedance goes even higher on other models (to reduce sensitivity).   And, importantly, for the LaScala, Belle, and K-Horns, sensitivity is 104 dB/watt/meter. 
To steal a line from Olsher, “The first milliwatt is the most important.”  Well, maybe the first 10 milliwatts.  And I think a microwatt is audible in theory.
So.  I’m serious about building an F6 and have enjoyed reading your thoughts on the benefits of second harmonic distortion and also your thoughts on “sweet spots.”  Question: Are the characteristics of the F6 amp and these speakers such that we’re away  from a harmonic sweet spot.  If so, do you have any suggestions?  Maybe bi-amping with single ended for the mid? Resistors?
 
I'd like to share whatever you have to say with the Klipsch Community where you have fans.  Okay?
Thank you again.
WMcD
 
 
 - - - - - - 
From NP:
 
F6 works great with La Scala’s, in fact the biggest FW dealer uses those
loudspeakers.  If you follow the threads on the F6 on DIYaudio you will see
discussion on the adjustment of the potentiometers in the circuit so as
to be able to adjust the harmonic distribution arbitrarily - the source of much
entertainment.
 
Of course I’m happy to share anything with Klipsch fans....
 
End of message from NP.

 

 

 

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Guest wdecho

All you need to adjust for amount of 2nd harmonic is some software like Arta, what I use, and some attenuation on the output of the amplifier. I have some more info on attenuation box somewhere if serious. Must have to properly set up most FW clones. From all I have read and seen on videos comparing Arta to an expensive spectrum analyzer it works just as good for this kind of job. I have an old HP distortion analyzer I rebuilt and the distortion figure is much the same with it as with Arta for the amplifiers I have tested. 

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