Universal Schematic.

[Deang]

X-0 is -15dB. Dude, you have no midrange. 

[geoff.]

@mboxler, I am in the process of acquiring the parts for a Universal crossover and was wondering why the .3 mH inductor is placed before the autoformer.

 

My only thought was less un-needed signal going in is better?

 

But having adjustable taps for the tweeter makes even more sense. To me...

 

There must be a reason ALK didn’t do this originally.

 

Parts Express sent me 6 mH coils instead of the 2.4s I ordered or I would probably be finishing at least one board by now, maybe that was for a reason.

[mboxler]

18 minutes ago, geoff. said:

@mboxler, I am in the process of acquiring the parts for a Universal crossover and was wondering why the .3 mH inductor is placed before the autoformer.

 

This was done so one could use an 8 or 16 ohm midrange and the load on the second order low pass filter will still be close to 8 ohms (due to the swamping resistor).  As long as you don't plan on switching back and forth between 8 and 16 ohm drivers that "Universal"  feature isn't as important, in my humble opinion.  Not sure how many 8 ohm squawkers are in use.

 

Mike

[Deang]

There are quite a few that people are using that are 8 ohms. The Selenium D405 and B&C DCM50 immediately come to mind. 

[Deang]

11 hours ago, mboxler said:

 

Has anyone experimented with placing the low pass to the squawker after the autoformer? 

It’s so much easier just to pad down the tweeter if you need to. Almost everyone I ever built them for, ran them without attenuation.  Exceptions were those running the Beyma CP-25 and JBL 2404H. 

[mxs8106]

On 4/10/2022 at 3:52 PM, Crankysoldermeister said:

X-0 is -15dB. Dude, you have no midrange. 

IMG_3285.HEIC

 

You're right, I looked at it wrong. Its X & 4 

 

[Deang]

That setting is -5.5

 

Y and 2 on the 3636 is -5.42

[Deang]

[Curious_George]

8 hours ago, Crankysoldermeister said:

I see you are getting more efficient in your builds... very nice.

[geoff.]

Question?

 

What value cap would I shunt across the woofer If I wanted cross at 400hz using the 2.4mH inductor in series?

 

And would I need to change the polarity of any drivers?

[jcn3]

12 hours ago, Crankysoldermeister said:

 

Beautiful work!

[Deang]

13 hours ago, Curious_George said:

I see you are getting more efficient in your builds... very nice.

Hmm, it’s always a form follows function thing with me. You’ve only got so much real estate and the parts kind of dictate what you can do. I take criticism much better than I used to, so if you have an example of something I could have done better on any of my prior builds, I’m totally open to hearing it. 

[mboxler]

3 hours ago, geoff. said:

Question?

 

What value cap would I shunt across the woofer If I wanted cross at 400hz using the 2.4mH inductor in series?

 

And would I need to change the polarity of any drivers?

 

The more I learn about crossovers, the more confused I get.  When one refers to a crossover point, is one referring to voltage or SPL?

 

Since a crossover can only control voltage, I took a wild guess. I tested the voltage across a Khorn K-33E with a 150uf shunt, and it came pretty close to a second order, 400hz filter.  The filter had to be underdamped to get to that point, hence the slight bump in voltage before it drops.  

 

Not sure how it would blend with the first order high pass to the squawker, though.

 

Mike

[Deang]

We have good measurements for some of the small mods people do on the Klipsch networks, so we know what is going on there. With this, you are basically going off into no man's land. 

 

What you need is a schematic for his AP12-400 and adding the high pass elements from the Universal to it (AP15-6000).

[geoff.]

3 hours ago, Crankysoldermeister said:

Hmm, it’s always a form follows function thing with me. You’ve got so much real estate and the parts kind of dictate what you can do. I take criticism much better than I used to, so if you have an example of something I could have done better on any of my prior builds, I’m totally open to hearing it. 

 

 

I immediately noticed the the red and black, in and out leads to the autoformer.

 

That just makes sense.

 

Not choking the capacitors with tightened zip ties makes sense too. 

[Deang]

Those capacitors are in metal containers, so zip ties would have been fine. I'm also tired of the drilling and the screws. I would have used adhesive years ago but could never find anything I was completely happy with. I will probably still use the ties for some builds.

 

BTW, zip ties are fine if you wrap them around the epoxy end caps and not the body of the capacitor. I take bigger issue with the mounts and the sharp corners. Those can be used, but something should be underneath the capacitor - and then a light touch on the cinch.

 

 

 

 

[Curious_George]

On 5/15/2022 at 12:18 PM, Crankysoldermeister said:

Hmm, it’s always a form follows function thing with me. You’ve only got so much real estate and the parts kind of dictate what you can do. I take criticism much better than I used to, so if you have an example of something I could have done better on any of my prior builds, I’m totally open to hearing it. 

The main item I noticed missing from the latest picture you posted was the lack of those single screw solder terminals. I know they provide a secure tie point for a solder connection, but they also seem to make the board "busy". I like the look much better without them. 

[Curious_George]

On 5/15/2022 at 1:50 PM, mboxler said:

The more I learn about crossovers, the more confused I get.  When one refers to a crossover point, is one referring to voltage or SPL?

The crossover point is simply a "reference frequency" measured in dB, so technically, it is SPL on a graph. The point where the frequency is -3dB. However, depending on the type of crossover, the crossover point could be -6dB, such as a Linkwitz-Riley 12dB/octave.

[Dave MacKay]

On 5/15/2022 at 1:50 PM, mboxler said:

 

The more I learn about crossovers, the more confused I get.  When one refers to a crossover point, is one referring to voltage or SPL?

 

Since a crossover can only control voltage, I took a wild guess. I tested the voltage across a Khorn K-33E with a 150uf shunt, and it came pretty close to a second order, 400hz filter.  The filter had to be underdamped to get to that point, hence the slight bump in voltage before it drops.  

 

Not sure how it would blend with the first order high pass to the squawker, though.

 

Mike

 

 Like @mboxler, I'm confused too.

 

I've been trying to understand how the 1st order filters used in the woofer section of the A and AA networks work. The filter consists of just a 2.5 mH inductor. When I calculate the crossover frequency into the K-33E (which is rated at 4 ohms), I get a crossover frequency of 250 Hz, not the 400 Hz that I was expecting.

 

Even if the K-33E was 8 ohms, the filter would crossover at 510 Hz, not 400 Hz.

 

I know that driver impedance isn't constant, and that it varies with signal frequency. When I vary the woofer impedance based on a curve that @Trey Cannon posted sometime ago, I find that the crossover frequency varies between 220 Hz and 1210 Hz in the frequency range applicable to the woofer. 

 

I had hoped for a nice clean drop-off starting at a specific frequency, but that doesn't seem to be how the filter works.

 

i thought that higher impedance = higher crossover frequency = more attenuation = lower SPL but that's not what my REW measurements show.

 

I must be failing to understand something. What am I missing?

[Deang]

In-network impedance plots for the Klipschorn, La Scala, Cornwall, and Heresy. 
 

What matters is the impedance at the crossover point. This is derived by combining the driver response, in the box, with the network - which is massaged until you get the acoustic response you want. 
 

You will not be able to make any sense out of any of this using any of the online calculators, which don’t account for the reactance between the parts, or the out of network acoustic response.