Crossover Layout OK?

[samtny]

Hi all,

Building Zaph's ZBM4 bookshelves, a pair, this is my first project, and thus also my first crossover build.

Am I committing any terrible sin/s with this layout?



I guess I'm already fairly confident, such that I will begin soldering shortly, but just looking for any input you all may think it is needed.

Love these forums! Everyone has been very helpful so far,

Sam T

[sdclc126]

Hi samtny,

I'm not an expert here, but I am not seeing where the positive lead comes into the crossover network from your amp/receiver, and I don't see the negative lead either. Also don't see where the equivalent leads go out to the drivers.

It appears that the woofer and tweeter circuits are connected, forming one large circuit, and they should be separate - the positive lead from amp should split in two and each of the two split leads should feed to the circuits for the drivers, and then all should have a common negative dump.

I like to build my XOs with woofer and tweeter circuits out on either side of the board, and a common negative circuit going down the middle.

Without disassembling at this point, can you use whatever software you have on your computer to draw in the +ve and -ve connections, and repost the edited photo? This will make interpretation and guidance (at least for me) much easier.

Thanks.

[auplater]

Actually, as long as you connect to the correct points as in Zaph's diagram, your connections look ok.

I assume you'll connect the input between the two "corners", (upper left/lower right), lower right being the common or ground connection.

The tweeter would then connect in between the 2 resistors and the lower right ground.

The woofer connects between lower right ground and between the 3.3uF cap at the bottom and the large inductor (iron core)... if I'm interpreting your components correctly.

Upper mid to right section = tweeter

lower left 2 components = woofer section...???

John L.

[samtny]

auplater; You got it! Great, it seems I'm on the right track then. Boy, you must've read a lot of xover diagrams before to be able to just pick it right out like that, cool... So I guess my inductor/component placements relative to each other must look okay, then, as well.

sdclc126; I had the same conceptual difficulty with it as you initially, but the tutorial at this link straightened me out pretty quick;

http://www.partsexpress.com/resource...-crossover.cfm

I just re-conceptualized Zaph's xover layout as not 2 separate circuits, but a single circuit where everything "flows" in one end and out the other (i.e., in through the "+" lead and out through the "-" or ground lead.

Thanks for the responses.

[sdclc126]

Pardon my useless advice!

I just don't think in relative abstract terms - I'm a very geometric person - the first crossover I built was for Zaph's BAMTM (never built the speakers actually) - I built it exactly according to his layouts, and I've been doing that ever since.

[auplater]

here's a 3.5 way (sort of) I designed and built ~ 2 years or so ago, complete with baffle step compensation, variable xover points for all the drivers, etc...:



if I can find the time, I'm gonna re-do it on solid cherry base with gold plated connections, etc... "pretty it up"...

..and the speakers where they're used...



glad I could help...

John L.

[samtny]

I just hooked up my leads and did all the soldering (a piece of cake having started out modding circuit boards!). Hooked up the drivers and plugged it in and tested the thing with my amp - sounds good! Which is to say, the tweeter is tweeting and the woofer woofs. Cranked it up *a bit*, just to give it a little workout- it was fun to watch the woofer cone bounce!

Now I can throw together the other one, test that and then its on to enclosure building in a friends workshop in a couple weeks.

One thing about this design so far, the sound seems to come off rather "shrill", and I don't mean the lack of bass/midrange because of the lack of enclosure. I have seen the frequency response curve from Zaph's site, so maybe this is just "more accurate" and I'm hearing more of the higher sound range, but when I switched back to my original Sony bass reflex minis I was relieved to get rid of the higher "hiss" sounding toprange.

No matter! I'm having loads of fun building this thing!

P.S.; auplater; HOLY CRIPES! There is no way my wife is letting me in the house with that towering thing! YOW! Does that thing break windows when you crank it up???

[sdclc126]

The "shrill" sound you are hearing in the top end may indeed go away once you've put the drivers into the cabinets and got everything placed where you want it.

You may also simply be hearing a more accurate treble reproduction that extended listening will verify. Your older speakers may not have a very strong top end and you could just be used to hearing it that way, so it sounds "normal" to you.

Give it some time and if it still seems shrill you could consider padding the tweeter with higher resistor values.

[samtny]

Here's the now-soldered xover, with the +'s and -'s drawn in;



Now I think I need to buy a wire cutter because the ends sticking out are bothering my sense of neatness.

Also bothering me; the fact my resistors are measuring "4.5" and "5.5" ohm resistance instead of "4.0" and "5.0", as they are marked... Posting this now to another thread - is this typical, that the measured resistance is different from what's marked???

[ocool_15]

Originally posted by samtny

Also bothering me; the fact my resistors are measuring "4.5" and "5.5" ohm resistance instead of "4.0" and "5.0", as they are marked... Posting this now to another thread - is this typical, that the measured resistance is different from what's marked???

Did you account for the test lead resistance? Just connect the test leads together and check. They are usually 0.5-0.6 ohm on the cheaper multimeters I have.