Trying to understand crossover diagrams

[Clienthes]

I just read The Loudspeaker Design Cookbook, which was incredibly informative. I think I understand a lot more of what y'all are talking about now. Some of the stuff I had kind of pieced together, but Mr. Dickason's book really helped me put more of it together.

After reading the book, I went back to look at a couple of the crossovers from the Mission Accomplished section to see if I could figure out what was going on. Of course, now I have questions.

I hope its not a party foul to paste the crossover diagram here



I'll start with the stuff in the woofer section that I don't understand. I think I get everything except the Cw2 bit. I don't understand why its routed back to the thingy that runs through the Cw1 bit. Also, is Cwz1 and Rwz1 an impedence equilizer?

In the tweeter, what is Ct3 for? Again, is that an impedance eq and a notch filter on there?

The mid just blew my mind. If someone could explain what some of the bits in this circuit are doing, I'd be grateful.

Of course, I'm sure if I tried to figure out the values, I'd be even more lost, but for now I just want to understand what all the parts are for. I'm trying to wrap my mind around why all this stuff works. Is there an electronics book that I might be able to get hold of that could clear up some of the basic circuits stuff I don't get? Maybe even not directly related to speaker building. I'd like to note I haven't taken a math class in like 12 years, so if it wasn't calc based that'd be great

I'm sure as I go over a couple other crossovers, I'll have more questions, if y'all don't mind me asking. Thanks to cjd for the very educational crossover.

[rj45]

Yokay!

I am _not_ an expert, but let me muddle along, and see what we come up with.

Woofer section:
LW1 and CW1 form a standard 2nd order crossover.
Cwz1 and RwZ1 are a Zobel, which flattens out the standard rising impedance of the woofer and makes it easier for the crossover to do what you want it to do.
LW2 and CW2 form a trap (or notch) filter, which is designed to attenuate (kill) the breakup modes of the RS270. You often see a resistor in parallel with the L and C.
The resistor (if present) can tune the depth of the notch filter.

The Dayton metal cones (and most metal cones) have breakup modes that require notch filters. You typically don't need a notch filter with paper or poly cones - they roll off smoothly on the top end.

Suggestion: download Speaker Workshop. There is a filter scratchpad inside where you can build arbitrary crossovers and see the results on driver output. I've learned a lot by inputting crossovers "real designers" have used to tame difficult drivers (ie: RS 180)

HTH,
-Don

[cjd]

Heh. Nothing like a thoroughly overdone (ok, so maybe not overdone, simply complex) crossover (I can say that, it's mine) to start with. Every so often I wonder if I can go back and simplify it. And then I balk at the concept. Spent plenty of time on it already, and, well... yeah. Plus, folks have built this, it sounds good, and I'd hate to discover we could have saved a few bucks more.

The tweeter has two impedance compensation circuits - one to deal with Le (voice-coil inductance - this is a traditional RC zobel) and one to deal with the Fs peak (this one may not really be 100% necessary in this design any more - I started with lower crossover points for the tweeter than I ended).

The CL pairs you've noted (woofer and mids have C + L wired in parallel, series to the drivers, tweeter has C+L in series, parallel to the driver) are indeed "notchy" but are more specifically how Jon has taught us all to achieve a cauer-elliptic filter. He has some very good posts on this subject that may help you here and there on this site. I think one of the M8a/n threads.

If you really want some fun, take a peek at the series networks I posted in the "CJD MTM" thread. :lol: For some reason those seem to confuse people even more despite being, well... not really that complex.

FWIW, when posting a diagram it's probably a good idea to say where it's from so someone curious about the rest of the design can find it.

[Clienthes]

I think I did take a look at your MTM crossovers. I'm pretty sure I understand what the bits do on those ones, for the most part. Probably not as thoroughly as I'd like, if I knew what I was missing. Anyway, it did seem much simpler (go figure, a two-way simpler than a three-way). I also looked at the x-overs for the tmww; those also seemed a lot simpler, and while there was quite a lot I didn't understand, I could at least identify the different...um, not sure what the technical term is...sub-circuits (maybe?) were. I looked at a few other x-overs. Jon's made my brain hurt.

Anywho, the things about the crossover above that I really wanted to know were concerning Cw2 and ct3.

The basic circuit in the book showed the Cw2 part going all the way from the top of the circuit to the bottom (+ to -?). Yours goes back around to the cw1...erm, technical terms again...thingy. What effect does that have?

Also, nothing like the ct3 component was in the book at all. I'm just wondering what it does.

Edit: I think you already answered that, but I just didn't get it...
So looking at this x-over:



Edit #2: Nope, still don't get the cauer-elliptic thing...

Any thoughts on a good book that might explain more about the subject than speaker-design specific books do? I'd really like to learn more. And I'd really like to learn what to call the bits and pieces...

[Clienthes]

I think I tried to DL speaker workshop at one point, but I couldn't make it do anything without the measurement files. Maybe I'm thinking of the wrong program...I'll take another look.

[KJP]

Parts Express has measurement files you can download for a lot of the drivers they sell.
These are great for playing with in Speakerworkshop.

[cjd]

I'm not aware of any speaker book that'll discuss cauer-elliptic filters. Jon's write-up on this site is probably one of the best resources for these filters.

I have a zillion crossovers for the MTM - the series options aren't published on my website though, just linked in a post near the end of the thread.

C