A vs. AA networks for the Khorn/LaScala

[ClaudeJ1]

In the old A and AA networks for Khorns and LaScalas, I noticed the tweeter
connection come AFTER the midrange capacitor instead of before it, like most
parallel networks.

1) What are the benefits of doing this?

2) Does the 13 uf capacitor act as a secondary rolloff for the tweeter?

3) does the tweeter represent an additional load to the 13 uf cap, and if
so, does if affect it's value?

I'm willing to bet that the difference is lower IM distortion in a tweeter
because you are feeding the tweeter a dual-frequency high pass filter before
the attenuation of the Autoformer.

Here's a quote from Tom Danley of Danley Sound Labs (the tapped horn dude):

Normal 0 MicrosoftInternetExplorer4 /* Style Definitions */
table.MsoNormalTable {mso-style-name:"Table Normal";
mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes;
mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in;
mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt;
font-family:"Times New Roman";}

<<"An example of the down side of a first order
filter.

Lets say you had a 1 inch dome tweeter, it was producing 2KHz and at a level
which was 85 dB in the listening chair 4 meters away.

If the dome were a piston, it would have to move .01 inches peak to peak to
produce that sound and more if it were not a ridged piston.

Assuming a first order filter at 2KHz and lets say
its fundamental resonance is 500Hz then one can estimate the excursion based on
a first order slope.

Now lets say your feeding in a signal at the same level but descending
frequency.

We see the excursion do the following.

At 1 KHz .02”pp

At 500Hz .04”pp

At 250Hz .04”pp

At 125Hz .04”pp

At 60Hz .04”pp

Now, once stiffness controlled (below the lowest resonance), the excursion
does not increase further but in this case, one can see the final excursion is
4 times (+12dB) the level at 2KHz and keeping in mind distortion is very
strongly motion related, one should not make it move any further than
necessary.

While this issue is not a concern for a woofer, it is a major technical flaw
of the first order high pass on a
tweeter">>

In defense of the first order of the original Klipsch "A" network,
it was being used on a HORN tweeter @ 6,000 Hz. So, the 3X higher frequency
would have less excursion than the 2 Khz.example in TD's quote above (9 times
less??). The horn loading should further reduce the excursion requirements by
10 X or more, by way of the 10 X greater efficiency and "throwing
power" of it's directional control. So, the another question arises when
doing this very thing in Klipsch related products.............is there an
Audible amount of distortion in the tweeter horn? If so, does putting the
tweeter's capacitor connection on the output side of the Squawker capacitor
instead of the common input reduce this distortion further?

I was always under the impression that the 3rd order slope of the
"AA" network tweeter filter, along with the Back to Back Zeners, was
there for "double protection" rather than distortion reduction.
Perhaps only Roy and Jim Hunter know for sure.

[Don Richard]

In Sound System Design, 3rd edition, Dr. Eugene Patronis calls that congiguration an "improved first order network". The rolloff rate is at 6 dB/octave for the first 2 octaves below the cutoff frequency, then increases to approx. 12 dB/octave below that. There is little sonic difference at normal listening levels but the tweeter would be better protected from low frequencies with such a configuration.

[sunnysal]

I assumed it was to protect the tweeter. I have not heard anyone say otherwise, but perhaps someone will chime in...regards, tony

[Guest " "]

" In the old A and AA networks for Khorns and LaScalas, I noticed the tweeter
connection come AFTER the midrange capacitor instead of before it, like most
parallel networks."

it's like this in the AK-4 and AL-4 as well.

Most folks only think of voltage source networks which are parallel circuts for each of the woofer, mid, and tweter.

But current sourced networks are another design which put in seires the woofer, mid, and tweeter circut.

And of course, there can certainly be combinations of both.