T2a inductance

[Klipschguy]

OK, it is my understanding from

reading a recent post that the inductance of the T2a (+ a capacitor) protects the squawker by giving an effective slope of about 10-12dB/octave.  What effect does it have on the tweeter leg of the circuit (like the E Network)?
 

PWKs use of the autoformer in his networks was brilliant. 

[henry4841]

I do not think protects the mid driver is correct because unlike the tweeter most mid drivers can take lots of power. The T2 is not in the tweeter circuit but then I have not seen the schematic you are referring to. Some cheap speakers only have a cap on the tweeter for a crossover network and nothing else and depend on the inherent rolloff of of the bass speaker and driver for the bass and mid crossover point.

[mboxler]

55 minutes ago, Klipschguy said:

 

What effect does it have on the tweeter leg of the circuit (like the E Network)?
 

 

I don't think I have a REW voltage plot for this, but here's a simulation of the Type E network that may help.  As you said, the squawker filter (green) is 10-12db per octave due to the inductance of the T2A.  The tweeter filter (red) is actually third order (16-18db per slope) up to 400hz, the turns second order.  It is kinda cool. 

 

Mike 

 

 

[Klipschguy]

Brilliant! Thanks for posted the plot, Mike. 
 

If you don’t mind me asking, what if one took the E Network from “tap 3” to say “tap 2” in the tweeter leg, how would it impact the roll off?

[mboxler]

52 minutes ago, Klipschguy said:

Brilliant! Thanks for posted the plot, Mike. 
 

If you don’t mind me asking, what if one took the E Network from “tap 3” to say “tap 2” in the tweeter leg, how would impact the roll off?

 

It may come as a surprise, but moving the tweeter from tap 3 to tap 2 has no affect on the squawker.  Here's the new simulation.

 

 

[Klipschguy]

1 hour ago, mboxler said:

 

It may come as a surprise, but moving the tweeter from tap 3 to tap 2 has no affect on the squawker.  Here's the new simulation.

 

 

Interesting. The slope is indeed constant, albeit there is about 3 more dB roll off for the tweeter relative to the squawker at 1KHz (20dB vs 17dB).  Thank you for your insight and taking time to run these curves. 

[Klipschguy]

 

The Type A network has the tweeter leg at “tap 5” but after the 13uf capacitor. I would assume the T2a would still provide some degree of the protection even though it seems the K77 is being run “wide open”?  

[mboxler]

1 hour ago, Klipschguy said:

 

The Type A network has the tweeter leg at “tap 5” but after the 13uf capacitor. I would assume the T2a would still provide some degree of the protection even though it seems the K77 is being run “wide open”?  

 

Correct!  Since the taps used on the A have more inductance, the slopes are not as steep and level off quicker. 

 

The green and brown plots are the normal taps.  The red and blue are when I moved the tweeter to tap4.

 

 

[mboxler]

Another interesting point I'd like to make is the squawker attenuation.  Even though the Type A squawker  is on tap 4 (-3.3db), you'll notice the attenuation never gets above around -4.8db.  This is due to the fact that two circuits are tied to the 13uf capacitor in parallel.  As the tweeter load starts to drop, the load on the capacitor starts dropping as well.  Eventually the value of the 13uf capacitor is too small for the parallel load and the voltage across the squawker stops increasing.  

 

Oh well, I find it interesting.

[Klipschguy]

Thank you, Mike. I also find the information quite interesting. Cheers to PWK (and you as well).