December 29, 2020 at 8:38 pm #12409
Hey guys, I’m Sam. I work in the manufacturing industry (specifically, CNC software support) and I am an avid woodworker that’s always trying to learn more and step out of my comfort zone. I recently got my hands on a small CNC router and I love the idea of making a set of custom speakers, as well as a subwoofer if possible. I have a ton of goals, but the first is to make a solid set of good to great speakers! Any help with crossovers would be greatly appreciated, as well as any hardware/driver recommendations – my goal would be to make 10″X6″ set of speakers for my computer setup. Thank you guys for welcoming me here and I look forward to learning from you all!
MemberDecember 31, 2020 at 4:27 pm
Hi Sam. you’ll probably do well by getting some extra equipment for speaker measurement if you’re planning on going for highest fidelity possible but if not you can more or less tune “by ear”, or guys in the forum can do it for you if you have driver data available.
ModeratorJanuary 1, 2021 at 7:43 pm
Welcome to the Forum! And Happy 2021!
So you’ve got the woodworking chops, which is a nice chunk of this hobby. Good.
For the design aspect, you state a 10″ x 6″ desktop (size of my first speaker build!). I’m going to guess that’s the face plate. Drivers, I wouldn’t go any bigger than about a 4″. Really, there are some 3″ drivers that would do well, such as the Dayton Audio ND91 and PC83, and the FaitalPRO 3FE25. What kind of depth are you looking at and what is the thickness of the material you are thinking of using? This’ll help determine some of the final performance parameters.
What kind of software are you looking at? There’s lots of free stuff out there, mostly for Windows, though any of the Excel based ones should be cross platform.
Go ahead and pick all of our brains, That’s what this forum is about. Here’s to success!
MemberJanuary 1, 2021 at 9:09 pm
First off, thanks for the warm welcome to the forum! and Happy New Year!
Awesome! It sounds like I’m on the right track. I plan on using 3/4″ MDF for the majority of the box with an oak or mahogany faceplate (with or without MDF behind it, depending on what you guys recommend!).
I’ve been watching a lot of KMA videos on Youtube as a guideline, but I’ve still got a couple questions.
I attached the image of the circuit I made using VituixCAD (V2, I believe), as well as the SPL graph.
Here are the questions I still have:
1) What other components do I need to assemble the Crossover itself? (I.e, Speaker wires, connectors, grounds, etc.)
2) Any Videos you would recommend for assembling the Crossover?
3) Any other general info that I’m missing?
Thanks in advance for your wisdom!
MemberJanuary 2, 2021 at 5:05 am
What is the issue with the resistor? Should I just have the tweeter have less resistance? I probably tripped myself up along the way somewhere and thought I had to add it. Electrical is something I am definitely learning from scratch.
ModeratorJanuary 2, 2021 at 6:14 am
Kirby’s been pretty quiet lately. Wonder what’s up.
Noticed that your cap on the tweeter was very small. a quick consult of a crossover chart shows that a 2.7 uF at 4 ohms crosses at about 14kHz. Should be a lot lower, say around 3kHz. I also wasn’t quite sure what you were doing with the shunts around the drivers.
Put your circuit into X-Sim to see if it would do anything different than VituixCAD. Looked similar. The curve looked a bit low in the middle, so I started playing around with some of the values and got it to flatten out, and also pulled the SPL up a bit. I wanted to check on Parts Express for their crossover parts values, just to make sure they were standard values you can get, but I can’t get into their site at the moment. When you look at the schematic, you’ll see that one of the resistors has a line through it denoting a short and one of the coils and caps have their centers missing denoting an open. That effectively removes them from the circuit.
Now, this is NOT the end all be all, since there are some things that could use further attention. But it does seem to be a bit more even. I welcome others to chime in.
Looking at the size you are going for and the mid woofer driver you chose, I don’t think you’d need 3/4″. Smaller panels are stiffer due to their reduced area. At that size, you “might” need to maximize interior volume, so thinner may be needed. You might be able to get away with 1/2″ or slightly less. Of course, if the required volume can be met with 3/4, then use it.
For the crossover, you’ll need wire to connect everything. Grounds are an electrical term for a connection to the “0” (zero) voltage point. In the speaker, that would be the negative terminal. You’ll also need something to mount everything to and either hot glue or maybe zip ties to hold things in place. As for videos, check out some of ToidsDIYAudio for some build inspiration.
What is the design volume and type of box you are going for? Sealed or ported?
BTW, this graph is at the same voltage as yours so you can easily compare.
MemberJanuary 2, 2021 at 3:04 pm
Thank you for the details!
So a couple more questions… What do you mean by shunt? What should my crossover point be? Also, I’m not sure if it makes a difference, but you’re using the 4ohm woofer and I am using the 8ohm. I changed it to a 4 woofer to match.
So, when I’m using things like Vituix, I’m picking my crossover point (which would be about the halfway point between the low hz of the tweeter and the high hz of the woofer?), then I am to achieve the lowest rate of change with impedance and as close to a straight line with the reference angle as possible?
I’ll go buy some 1/2 MDF, that’s no biggie. I was going to give ported a shot, but I haven’t really gone that far. Honestly, the crossover and the electrical scare me the most given my lack of experience with both. I am going to make a finished design once I have the drivers in my hand so I can make a final decision on height and width and then figure out the depth from there.
I changed my circuit to match what you had. #1 is the tweeter (in red) and #2 is the woofer (light blue). Isn’t that a large overlap? if not, I apologize! I’m trying to figure this out.
Thanks for all of your help guys! It’s greatly appreciated
ModeratorJanuary 2, 2021 at 6:53 pm
You’re welcome. I hope to help anyone who asks.
A shunt is an electrical term for basically a “bypass path” for electricity. In our case it is a frequency dependent bypass, sending a range of frequencies above or below the filter, depending on type.
Crossover point is usually set to around 2x’s the resonant frequency of the next in line driver. Since you re doing a 2-way system, that would be the tweeter. The TD20F lists it at a little above 1600 Hz, so normally you could go with whatever it would be ( 3200-3300 +- ), but you also have to look at your mid-woofer. It drops off at 5000 Hz, so you need to cross over a bit sooner. 3000 Hz is fair game, giving both some room to roll off in their respective directions. Since it’s a little tight between them, you might want to go with a steeper slope. Currently, this design is a 1st order which rolls off at 6dB /octave, so a 3rd order should give a tighter crossover, keeping the less useable areas of the drivers out the graph. This helps to keep distortion and breakup away. For a better explanation of crossover orders, just Google “speaker crossover orders” to see some of the differences and designs available. Also, watch some of the videos I linked above. They should help too.
As to the TCP115, I chose the 4 ohm version since the tweeter is a 4 ohm. It is a general assumption that isn’t always right. 😀 You can mix and match impedances, but it is easier to design a crossover if you try to keep the drivers the same equivalent impedance. I say equivalent since you may sometime want to use more than one of a driver in a design, say 2 woofers and a tweeter. Depending on the tweeter impedance, you can get woofers that can be wired to be the equivalent of the tweeter impedance. So say you need to match to 8 ohms, you can wire 2 – 4 ohm woofers in series to get 8 ohms or 2 – 16 ohm woofers in parallel to get 8 ohms. ‘Nuff of that for now.
Back to the crossover, you want to try to get a flat as possible line. Though you’ll find that once you put it in a box, that will affect it. That’s why CAP mentioned some measurement equipment to help out. I suggest you try designing a box and then take another look at the crossover once you’ve added the box into the mix. I think VituixCAD does that, though I can’t say for sure, since I don’t have it. Anyway, it looks like a box of around 0.081 Cu.Ft. will get you tuned down to about 60Hz. Pretty respectable for a 4″. You’ll have to check port size for velocity and then build that into the interior volume. Or, if it’s long enough, you could be a bit Cyberpunk and put it on the outside. Just a thought. If you need some idea how port size and length and tuning are interconnected, checkout the guys listed in the Sound-Advice YouTube podcast. There’s some good tutorials there.
Oh, I checked a rough box size for the 0.08 Cu.Ft., and you can use your 3/4″ MDF and still keep it around that size.
For the overlap, I was just messing with your values until I liked, more or less, what I saw. Give it a try with this new information and a fresh design and see what you come up with. It’s all worth the learning experience.
** As a reference, here’s a Capacitor X-over chart to give you an idea of what you should be seeing at first.
MemberJanuary 2, 2021 at 8:08 pm
So a shunt is equivalent to a Highpass/lowpass? and when you refer to “next-in-line” you’re referring to the first driver coming from the power source?
The general idea of increasing order makes sense – you get more “control” of the sound the higher order you go.
I’m going to take a step away from the crossover for a little bit, because I’ve spent 2 days sitting behind my computer at this point. Here is where I’m at:
I hope this looks better.
I’ll take a step back and look at making an enclosure.
I’ll also look at some of the sources you guys have posted and if there are any other sources you suggest I look at, let me know!
Again, thanks for all of the help.
ModeratorJanuary 2, 2021 at 8:50 pm
A shunt is more of a “bleed” in our case. For example, if you have a spike at a certain frequency, you can design a filter that can “shunt” or bleed” some of that energy to ground in order to smooth things out. Hope that better explains it.
That graph looks much better than the first. Let us know what you come up with for a box and port, then we can go from there.
Gotta get some stuff done around he house. Catch you later.
AdministratorJanuary 3, 2021 at 8:52 am
the issue with the resistor in front of the woofer, is the woofer sees the majority of the power. So by adding that there, it will heat up fast and stop doing it’s job. Really you typically only want to add a resistor in front of a tweeter for this reason. There is a power dissipation, that goes on in loudspeakers. The basic premise is the lower you go in frequency the more power it will receive. The higher, the less power. As an example, if you gave that speaker 50w, your tweeter would probably see less than 5 watts of it.
MemberFebruary 2, 2021 at 2:33 pm
Alright… SO I have made my speakers! (I’ll gladly post the end results once I’m completely done and content) I just have one problem… the speakers cut in and out above half power using my stereo amplifier (Lepai LP-2020TI). I ran out of time last night to start troubleshooting, so I am at square one. What are possible issues and where do I start? Thank you in advance for your time guys! Thanks for helping me get this far already!
AdministratorFebruary 3, 2021 at 5:42 am
Show us your impedance plot. If it is the one pictured above it is probably due to you impedance dropping to 2 ohm at 2.5khz. I missed where you posted the last picture, otherwise I would have said soemthing. This is common though with your first build, to focus only on frequency response.