Didn't PWK write a paper about driver alignment not being that important

[Chief bonehead]

On 8/21/2016 at 3:36 PM, Chris A said:

Sorry for the delay in response on this one. 

 

What I've found is that, at least in the case of the Cornwall 1.5 (1979 model), and perhaps just by chance...but probably not, the Cornwall balancing network seems to be "phase aligned", in other words, the balancing network and the position of the drivers in the cabinet pretty much adjusts the phase delay of the midrange and tweeter to be multiples of 360 degrees of phase to one another.  While this isn't as good as full time-alignment in terms of the listening experience, it definitely cuts way down on the phase/time delay distortions that would otherwise detract more seriously from the listening experience. 

 

So from this observation, it's clear to me that PWK knew about phase/time delay issues and actually worked to minimize their effects-probably going back to the beginning--whatever year "AD" that happened to be. (By the way, PWK himself mentioned that phase and time delays are the same thing in the referenced article he penned.)  I assume that PWK also took steps to do the same with the other Heritage loudspeaker models.  If you can't fully correct the time delay issues, then you should at least phase align the drivers via the balancing/crossover network at multiples of 360 degrees from each other. 

 

Chris

is the phase curves of the driver/horn combos are consistent (not acting weird) and wavelength displacement are short, you can adjust it in the passive.

[Chief bonehead]

On 8/21/2016 at 2:45 PM, Chris A said:

If you look at a couple of the plots in the Belle tri-amping thread, you'll see an instance where I didn't set the delay correctly, and you see symmetric "side-band distortions" in the phase response, such as this plot:

 

 

This is a case where I was learning about how to measure and set correct delays, and Greg Oshiro patiently and calmly suggested that I take a some time to "get the hang of it".  That exercise was very instructive and informative as it turns out.  I wouldn't trade that experience now.  Using REW (freeware), a calibration microphone (about $100, with small mixer to provide phantom power to the microphone and to digitize its output back to my laptop) and a digital crossover to dial in changes and see the effects--was a very useful experience.  I highly recommend it to anyone that's a bit more serious about their loudspeaker performance if they get a chance to use a digital crossover such as an ElectroVoice, Ashly, Xilica, etc. and stereo amplifiers to tri-amp their 3-way loudspeakers.  The events around producing that Belle tri-amping thread was a fun and very useful experience.

 

Chris

you should show one that is corrected for comparison.

[JL Sargent]

24 minutes ago, Chief bonehead said:

are they hornloaded?

 

Of course! My Belles for example.

 

Now lets get back to the important stuff: Have you ordered your Whopper Plopper yet?

 

[Chief bonehead]

9 minutes ago, JL Sargent said:

 

Of course! My Belles for example.

 

Now lets get back to the important stuff: Have you ordered your Whopper Plopper yet?

 

i didnt order them....i went and bought them!!  looking forward to using them on lake fork!!

 

[JL Sargent]

6 minutes ago, Chief bonehead said:

i went and bought them!!  looking forward to using them on lake fork!!

Awesome! I'll be expecting your thoughts on the matter afterwards.

 

[Marvel]

1 hour ago, Chief bonehead said:

the phase curves of the driver/horn combos are consistent (not acting weird) and wavelength displacement are short, you can adjust it in the passive.

 

So it would also make even more sense to use a tractrix horn with a direct radiator and the horn depth is shallower and more than likely closer in alignment with the woofer. Would that be true? If so, then a tractrix would be more out of alignment in a Klipschorn or La Scala since the woofer is farther back?

 

Bruce

[USNRET]

17 minutes ago, Chief bonehead said:

i didnt order them....i went and bought them!!  looking forward to using them on lake fork!!

 

Lived 15 minutes from Fork for several years. When looking at homes I toured one that had the owner's photos on wall. He had caught the record big mouth there (what 17 + lbs IIRC).

[Chief bonehead]

9 minutes ago, Marvel said:

 

So it would also make even more sense to use a tractrix horn with a direct radiator and the horn depth is shallower and more than like closer in alignment with the woofer. Would that be true? If so, then a tractrix would be more out of alignment in a Klipschorn or La Scala sine the woofer is farther back?

 

Bruce

yes and yes. but whether is 18 inches versus 24 inches...its still hard to make that displacement up.

[Chief bonehead]

5 minutes ago, USNRET said:

Lived 15 minutes from Fork for several years. When looking at homes I toured one that had the owner's photos on wall. He had caught the record big mouth there (what 17 + lbs IIRC).

i will be taking the pic of the new state record that i will catch....

[Chris A]

8 hours ago, Chief bonehead said:

you should show one that is corrected for comparison.

Here is my on-axis/1 metre 3-way JuBelle with Beyma CP25 tweeter that I last used before switching to the "new center" (i.e., multiple-entry K-402 horn).  I crossed the JuBelle at 450 Hz and at 8000 Hz using a ElectroVoice Dx38 crossover using L-R 24 dB/octave filters :

 

 

That little dip at 100 Hz was due to the floor boundary cancellation (1/4 wavelength) of the microphone...34 inches off the floor.

 

Chris

[Chris A]

Here is a plot of the excess group delay of that same measurement:

 

 

This is the measurement (excess GD) advocated by D'Appolito in his book on loudspeaker measurements...to check for correct phase delay in the crossover regions.

 

Chris

[Chief bonehead]

13 hours ago, Chris A said:

Here is my on-axis/1 metre 3-way JuBelle with Beyma CP25 tweeter that I last used before switching to the "new center" (i.e., multiple-entry K-402 horn).  I crossed the JuBelle at 450 Hz and at 8000 Hz using a ElectroVoice Dx38 crossover using L-R 24 dB/octave filters :

 

 

That little dip at 100 Hz was due to the floor boundary cancellation (1/4 wavelength) of the microphone...34 inches off the floor.

 

Chris

from the phase curve there is no way to tell where the crossovers are.  looks really good.  can you overlay the freq response of the lf, mf and hf?

[Chris A]

3 minutes ago, Chief bonehead said:

can you overlay the freq response of the lf, mf and hf?

 

I'll have to set up for that and take the individual channel measurements, unfortunately.  At the time (3 Dec 2014), I only needed the combined response.

 

Right now, the K-402 multiple entry horn (MEH) is in the place where the 3-way JuBelle was.  Both of these units (JuBelle and K-402-MEH) are a bit large to manhandle on and off their 2 1/2 foot riser in the center between the Jubs (I use a riser to get the centerline of the mid-frequencies at the same vertical height axis as the Jub K-402s on either side).  So it will have to wait a until I move the JuBelle back into position when I start working on the K-402-MEH horn again.  That will happen when the outside dew point is below 70 and the dry bulb is below 80--that's my goal to start up again.  That may be within the next 4-6 weeks. 

[Chris A]

A link to the settings used in the above Belle bass bin + K-510/K-69-A + Beyma CP25: