Xover PCB trace width and design recommendations

[unclejunebug]

Hello all,

I assume there are some users here that have done some Xover PCB design. I'm looking at designing a PCB for a build and I'm curious about the following...

1. Is there a minimum recommended trace width between components?
2. Are there any guidelines regarding routing signals beneath certain components? (i.e. never route a signal underneath an inductor, etc...)
3. Should all traces leading to positive and negative speaker terminal connections be kept on separate layers?
4. Any basic guidelines one should follow?

Thanks in advance for any feedback!

[01-0077]

Hi Unclejunebug,

Here is a pic of two xover pcb's I designed in easyeda/jlcpcb for an Overnight Sensation TMM build. My traces are 7mm (~ 9/32") wide. I kept all traces on the bottom side of the pcb to avoid having components sitting directly on the traces. I figured this way there is no chance of a component chafing through the soldermask causing a short. I went with 2oz copper but would have preferred 4oz. I found it easier to split the crossover into a bass/mid network and tweeter network. By doing this the pcb isn't as cluttered and you can keep the traces as wide as possible.

Hope this helps, John.

[unclejunebug]

Hi John,

Thanks for that info, that does help indeed! I was messing around with KiCad last night and going through some tutorials to put together an initial design. One thing I noticed while looking at PCBs that are available online was that all traces appeared to be on the back only so I will have to make that adjustment. I also started out with 3mm traces so I'll beef those up a bit.

You mentioned JLCPCB and that you would have preferred 4oz copper. Did you use JLCPCB to fab your boards? I have been playing around with their order form just to see what pricing comes out to with different sizes/options but I did not see a 4oz copper option. Is there one hiding somewhere? If there is, I shudder to think what it would do to the cost haha. Going from 1oz to 2oz triples it for me, though still a reasonable cost at $27.50. If there was a 4oz option that tripled it again I'd likely be in the category of "this is no longer worth it."

Thanks,
Steve

[JRT]

I assume there are some users here that have done some Xover PCB design. ...
Thanks in advance for any feedback!

There is advantage in point wiring in allowing easier changes in future design development revisions.

There is no advantage in using printed circuit board assemblies in this, unless you are planning to mass produce your loudspeakers.

[unclejunebug]

Yeah, I completely agree with that and see the benefit of the point wiring. The exercise of doing the PCB is more of a vehicle I can use to familiarize myself with board design and the tools available for hobbyists. And really a big part of it is that I just like the "finished" look of the PCB compared to the alternative and the satisfaction of using a board I designed and had fab'd.

[a4eaudio]

...And really a big part of it is that I just like the "finished" look of the PCB compared to the alternative and the satisfaction of using a board I designed and had fab'd.

I agree with this. I wouldn't do this for a budget build, or every build, but I'll be working on a pretty big, expensive project and think this would be a nice addition. Thanks for posting this thread, as I will probably try to do this also. Also, if you go through with it, please post the final result (and price).

[unclejunebug]

I agree with this. I wouldn't do this for a budget build, or every build, but I'll be working on a pretty big, expensive project and think this would be a nice addition. Thanks for posting this thread, as I will probably try to do this also. Also, if you go through with it, please post the final result (and price).

I imagine that I will end up going through with it and I’ll for sure post the finished board and cost if I do. The main reason I wouldn’t is if the cost gets too high, which for this project, is about $50. Right now my estimates with shipping are under that number.

[01-0077]

Hi Steve,

Yes I used JLCPCB to fabricate my boards and this is why I had to use 2oz copper as I am pretty sure this is the maximum they offer. The other thing that took some time was creating the footprints for the resistors, caps and inductors as they weren't available in the parts library. With regard to there being no advantage in using PCB's tell that to somebody who has OCD tendencies

[unclejunebug]

Yes I used JLCPCB to fabricate my boards and this is why I had to use 2oz copper as I am pretty sure this is the maximum they offer. The other thing that took some time was creating the footprints for the resistors, caps and inductors as they weren't available in the parts library.

Yeah, I didn't find any 4oz option either on their site. I tried every Base Material/Surface Finish combo I could and a 4oz option never showed up. Though I do think would likely be too expensive for this project if there was one. I have been using KiCad up to this point and have already created my footprints. I have been thinking about moving over to EasyEDA since it's got some integration with JLCPCB and I'm hoping I can port over my existing footprints. I'm not sure if those files use a standardized format or not.

Can you tell me what surface finish you used?

With regard to there being no advantage in using PCB's tell that to somebody who has OCD tendencies

RIGHT?!?!?!?!?!? And going with a PCB certainly doesn't make a design sound better, but added cool factor? Most definitely :D

[01-0077]

For surface finish I went with HASL(with lead), thought it may assist with my soldering efforts.

[unclejunebug]

One last question for you. Can you tell me the part numbers of the screw terminals you're using? If your traces are 7mm what is the pitch of the terminals? 10mm?

[01-0077]

The screw terminals are manufactured by Dinkle Corporation part number EK950V-02P, pitch of pins is 9.52mm. You can connect two together to form a 4 position screw terminal as you can see on the output side of my larger pcb, they just slide together. They make them with 2 to 25 screw positions, the numbers preceeding the P in the part number indicate the number of screw positions.

[unclejunebug]

Awesome, thanks, John! I appreciate the info! Looks like I need to make another footprint :D

[wogg]

Is JLCPCB really that cheap, provided you can create your own gerbers? Only $2 for a 100mm square 2 layer seems crazy cheap!

I've only used ExpressPCB, at significantly higher cost mostly due to their freeware design software since I don't have any CAD programs capable of proper board design and gerber output. What's a good freeware for gerber output?

Like above... I wouldn't do this for a speaker crossover board, my OCD level doesn't push me past point to point. I do however do some through-hole custom designs for stuff on occasion and I'm way past wanting to etch my own hand drawn boards.

[unclejunebug]

Is JLCPCB really that cheap, provided you can create your own gerbers? Only $2 for a 100mm square 2 layer seems crazy cheap!

I've only used ExpressPCB, at significantly higher cost mostly due to their freeware design software since I don't have any CAD programs capable of proper board design and gerber output. What's a good freeware for gerber output?

Like above... I wouldn't do this for a speaker crossover board, my OCD level doesn't push me past point to point. I do however do some through-hole custom designs for stuff on occasion and I'm way past wanting to etch my own hand drawn boards.

It is that cheap if you go with 1oz outer copper weight and all the bare minimums for five 100x100mm boards. Shipping is of course on top of that but 8-14 day shipping doesn't add that much for a small order. For the options I'm looking at with a size of 100x135mm my cost is just under $40 shipped. I find this totally reasonable for this type of thing. There are board house options in the states of course but they are more expensive.

I've been using KiCad and EasyEDA, both of which have Gerber output options and both are free. There is a really good KiCad tutorial series on Youtube on Digikey's channel. The series is about 4-5 years old now so the KiCad software in the videos is out of date but the videos are still very very useful. If you're already familiar with EDA tools then you may not need the series, but I'd think KiCad could do everything you'd need as far as Gerber output is concerned (One of the videos goes over this process).