A gift for many? - The Mechano23

[technodanvan]

I've been thinking of making a set of gift speakers for a while now, something I could give to friends and family that wouldn't break the bank and was reasonably simple to manufacture quickly. In lieu of designing something for myself I think I have settled on the Mechano23, designed by Xmachinik. His website is linked below, as is the thread at ASR where it is well documented and discussed (and where I first discovered the design) and Amir's review of the design using his fancy gear.

Xmachinik Website
AudioScienceReview Post
AudioScienceReview Review by Amir

This speaker uses the affordably priced Scan Speak H2606/920000 tweeter ($47.80 at the time of this writing) and the even more affordably priced SB Acoustics SB13PFCR25-04 midwoofer ($36.80) in a roughly 8 liter box. Just under $170 USD (plus tax and such) is pretty darn solid for drivers these days, and with all the positive reviews from the various websites and users it was hard for me to ignore. I had originally pushed this project off with a reminder to look at it closer toward Christmas, but I came across a project on Makerworld that reminded me of it a bit sooner than expected.

Mechano-23-CS on Markerworld

This project was posted by user_1168315211 (no other identifier that I could find, but I wanted to be sure to call out their work) and appears to be intended for experienced builders and those new to DIY. The model is split into several parts: the woofer portion, tweeter portion, crossover boards, and port (which could be modified for various tuning). This was also seemingly intended for a variety of 3D printers with the woofer and tweeter portions split as they were. There was some effort to stiffen up the sides of the cabinet by adding some vertical ribs as well, though this is also a function of the infill density and wall loops, among other things that can be adjusted within the slicer software. I went ahead and printed one cabinet to see how it looked.






I noticed a few things about the build that I felt required a little attention, the most obvious one (to me) being the portions that would be adhered to each other could have a means of holding everything aligned during that process, but there were a few other small details I felt I could help with. I reached out to the original CAD / Slicer model but didn't receive a response, so I decided to recreate it myself. I'm not sure I'll share the files on Makerworld, but we'll see. I'm also not sure I'll 'only' make the Mechano23 with a printer but I figured I'd give it a go.

I had a few goals with this design.

1. First, the largest dimension is only 290mm, meaning it'll fit on my printer - I won't need to do a split cabinet design. However, there will still be a few separate pieces by necessity. The seams should be more natural though.
2. I want to minimize to the maximum extent possible the number of supports that need to be printed. I'm just not a fan of them and they can often be engineered out in designs such as this.
3. Glue should not be necessary.
4. Baffle and rear will be printed separately and bolted on.
5. The outer cabinet (sides and top) will be printed in one piece. The major downside here is the print time could be several days and use two or more rolls of filament per side. That's a long time for something to go wrong. Hard to avoid this.
6. Threaded heatset inserts will be used extensively.
7. Gaskets will also be printed from TPU (or, perhaps, cut from neoprene using the printer)
8. Braces will be integral to the design (and also printed).

Gotta run more to come...

[technodanvan]

Alright, back at it. My first intent is to create some 'shells' to prototype the models. This one I printed at 25% infill (i.e. not just a shell, which might just be 5%) with PETG-CF (carbon fiber) so it's really quite solid. I think in an ideal world I'd use CF for all parts but the available colors aren't going to work for every situation. I want to test this with regular PETG to see how much difference that might make. A couple key notes about the below baffle compared to the speaker design by Xmechanik and the original model on Makerworld:

1. The original baffle (in addition to all other sides) called for 18mm of Baltic birch. Obviously this is a great starting point for a small speaker! However, I'm working with plastic here and the interior will probably be ~75% air in the finished model. I felt I needed to go thicker to shore up the strength a bit, so I elected to go with 36mm. This will also increase the volume a little, which I'll need later.
2. I couldn't tell if the original design called for carving out the back of the baffle around the woofer. The 3D printed version did not. I have included this in my redesign.
3. The original design has no chamfer or roundover on the edges of the baffle. Given how well it measures and the reception it has received I guess this works just fine. However, that seems kinda boring to me, and it must have to the 3D printed modeler as well since they included a pretty good roundover on the vertical edges. Normally I would do that same, but a 3D printed roundover in which the baffle is constructed from back to front ends up looking a little rough. I think it looks really quite nice with a relatively steep chamfer instead, which I placed on all four edges.
4. This baffle is held on by eight 1/4-20 bolts. Six would have been fine, but I decided having 4x arranged around both the tweeter and the woofer would look nice. The current print uses the low profile 316 stainless hex top bolts I have set aside for another project, thinking they would be nice here too. These are expensive, something like $10+ apiece. There will also be eight on the back, so that would be $160+ per side, or in other words, WAY too much for ~$170 worth of drivers total, especially if I'm making multiples. Making the change to 82 degree countersunk hex bolts (still 316 stainless) runs about $1 each for the same size. Still pricey for what amounts to a pretty (but nice) bolt, but FAR more palatable to the wallet. I'll see if I can find a way to buy some in bulk.
5. The drivers will be attached with M3 bolts (for the tweeter) and M4 bolts (for the midwoofer). I haven't priced these yet, but I'm obviously hoping they'll be cheaper still.

The other side of the baffle is currently flat. I have thought about including guide pins, or a groove for the gasket, or even a groove that might fit a corresponding protrusion of sorts on the cabinet itself. I do not think these are necessary - the bolts will essentially be pins that will aid in alignment. I learned from the AliExpress 'sub' box that having a groove on both the cabinet and the baffle is kind of a pain to align and keep in place while clamping down, and I have a groove located on the cabinet already. The current baffle also does not require any supports when printed back to front.

[technodanvan]

So this is where things started to look a bit more complicated than the print I did from Makerworld. Here are the individual parts shown (or, at least, mostly shown) in the images below, along with a few features.

1. Cabinet (sides/top/bottom)
   1. Can be printed in one piece with supports only used for one of the grooves. All the angles shown are important in order to make this possible. It could be printed from back to front or front to back, but I'd probably go with the former.
   2. This would be a 3-day print at 25% infill. That's twice as long as anything I've done, but having minimal supports (and in this case, no supports after the first hour or two) really increases the likelihood of success.
   3. This would be a minimum of 2 kg of filament per cabinet.
2. Top brace/port
   1. 180 degree roundover on the inner port
   2. Slides into the cabinet from the back. Unknown how these tolerances are so that'll be something to watch for
   3. Printed with only a support for the groove in the back for the gasket.
3. Mid brace
   1. Not much to say here, other than I might make this go closer to the driver yet. Need to measure the tolerances for that.
   2. Slides into the cabinet from the back.
   3. Printed with only a support for the groove in the back. I opted to have the gasket 'seal' the braces so there would be contact with the rear. Might help a little with resonances.
4. Bottom brace/crossover bracket
   1. This is designed around a PCB someone made for the crossover, which I'll be using (and linking later). This should speed up assembly if I'm making multiples.
   2. Slides into the cabinet from the back.
   3. This might be the smallest piece in terms of filament usage (other than the gaskets) but it's the most complicated in that it'll currently need more supports. I am considering a way to print this such that it would need less. That would entail changing the way it attaches on the sides and I'm not sure I want to do that.
5. Baffle gasket
   1. Pretty straightforward, but one thing (that should have been obvious) I learned from the AliExpress subwoofer cabinet is you don't make the gasket the same size as the groove. It fit on one side with some effort, but there was no chance it would go into the corresponding slot on the baffle. This time, I made the gasket a little smaller than the groove so it'll easily fit. It's 3mm thick with a 2mm deep groove too, which is a bit thinner that I had used previously as I observed little compression. This'll be trial and error as well to get right.
6. Rear gasket
   1. No notes here, same thought process as stated in previous bullets.

So here's the question then: Is there anything obvious I'm missing from the design so far?

Other than the entirety of the back, of course!

[technodanvan]

It was pointed out to me that I could improve the port geometry by looking into the work augerpro has done, in addition to the effort STV has done at DIYAudio. This seems to be realized in a fantastic little website by Naturlyd (also at DIYAudio) that can output the port in a printable format.

Optimal Port Designer

Now, there are some potential issues here that I need to experiment with:

1. Should I keep the ~45Hz tuning that Xmechanik used?
2. What volume do I actually have when this is all said and done? (original spec was around 8L)
3. Do I want to use the port as a brace as originally intended?

[technodanvan]

Alright, so I have a little more time and a few things have finished printing. First up is the cabinet sides and top - this was a test run so I had it printing fast and basically hollow, but it works for what I need right now.



First impressions are pretty good. I'm continually impressed with what these machines can do even under stress. To go with the cabinet I also printed the original port and crossover platform so I could test fitment. Looks pretty good! It was a bit of a challenge to shove them in the last inch or so, but once they're in I really don't think they're coming loose. Could use epoxy to be sure but I'm near certain it isn't necessary.



Of course, there were problems too. Printing things this large tends to have the corners pull up off the plate. I'm not sure how to counter this, but I've seen it before. I can use better adhesive but sometimes that doesn't help, the plate just comes up with the corners.



Another potential issue are the mounting holes on the front (I printed face down, so they were supported). I think this is because they aren't considered one of the first few layers anymore, leading to the printer moving very fast through this section. I think I can counter this because I'll be having it print more layers on the faces themselves (at 100%) and I'll be slowing the printer down for the real print. Remember, this only took one night (~10 hours) to print where the real thing will take 3 days.



I also printed the new port. I like it!

[JonMarsh]

A lot of good looking work there- I'd suggest a little time spent with Unibox or VituixCAD to asses if 45 Hz port tuning is optimal for what you intend and need. But for 8 L, it's probably close to maximally flat, assuming you plant to crossover say, around 80 or 100Hz. If this is stand alone, I'd have gone for the 100Hz size and an F3 of 50 Hz.

Regarding the Scanspeak tweeter, I'm still of the opinion that the DA25TX is the best $300 tweeter you can buy for about $50-$60 dollars; looking at the specs on that short horn loaded Scanspeak, especially upper extension, off axis response, and lower frequency extension don't change my mind. I suspect ET would use stronger language if he were to chime in!

[technodanvan]

Hi Jon!

Well, keep in mind this is someone else's driver selection and crossover design, as I was hoping for something quick and easy I could model in CAD then print while working on other projects (or actually working for my job). This is proving a bit more than I bargained for and further improvements are coming. I have enough drivers for a pair already so I'll definitely be making one set either way. I'll be further optimizing the port; several other folks have stated it should be tuned a bit higher (say, 50-55 Hz) and I'm not super sure what volume I'll have just yet. That said, the port will be removable and easily replaced, so I can try a few things here. I REALLY like the optimized port website I linked earlier. Fantastic work by several individuals led to that development.

* * * * *

But of course, you have me thinking. I already have five pairs of the DA25TX sitting in storage (along with two pair of the DA32TX) as I was paranoid PE would stop selling them almost as soon as they started again. I had plans for some of these but those are dissolving quickly. So not only is the DA25TX a high value proposition tweeter it costs me nothing to use them...unless I insist on having more stored away for a rainy day. Someone else was asking about the Audio First Fidelia kit and if such a baffle could be used for the Mechano23. While I do not believe that effort would be super worth it for those parts, it may be worth it for the DA25TX. I do not believe I am the one to create such a baffle though as my CAD skills are pretty limited when it comes to complex curves, but I'd be happy to print and test them, and I suspect I would be very okay with a compact traditional waveguide as well.

That leads us to an appropriate woofer. As much as I would like to upgrade to a 6" driver I would prefer to keep the same form factor as most folks I'd gift these to are not accustomed to anything other than a Bluetooth speaker or soundbar. I also can't go too much larger otherwise I risk not being able to print these and would instead actually have to get my hands dirty. So we're sticking with ~5" midwoofers. I'm seeing the below as possible candidates, but there are so many more out there I probably missed something. Ideally we're looking at around $50 (or less) per driver, but several of these are up to (and even a little over) double that value:

• Denovo Audio 5.5" Anarchy, of which the 8 ohm is still available at Cinergy Audio (but it probably won't be restocked once gone)
• SB Acoustics SB15CAC (it exceeds $100 per unit but is a solid performer for sure, the cone color may also go favorably with several color pairs I'll be using)
• SB Acoustics SB15NBAC is very interesting to me but is an unknown performer - it might be new?
• The Peerless NE149W-08 can still be found at PE (but only 10 of them, and it may not be restocked after they are gone)
• Dayton Audio RS125?
• Dayton Audio ND-140?
• Dayton Audio SIG-150?
• Midwest Audio Club MAC-05? (Researching this on the MAC forum right now, the cone color is also interesting to me as it has a silver appearance similar to that of the SB CAC line)
• FaitalPro 5FE120 (this one is VERY interesting to me and I'm going to model it at some point for bass performance)
• Aurum Cantus AC120/50CK is even more pricey than the SB CAC line at $120/per but I REALLY like the appearance.

[JonMarsh]

Well, you know Danny, everyone has an opinion, right? A few from me...

Some of this is like a list of drivers I have bought because I believed they would be a cut above for certain applications...

In that category,

• Anarchy 5.5" (availability has been a problem for various Anarchy models, unfortunately)
• SB Acoustics SB15CAC, have some, considered as a midrange role, smooth extended response, fairly ideal Qts (flexible for applications), possible to get some low end.
• SB Acoustics SB15NBAC- not quite seeing the value proposition, would have to measure and compare. Based on published SPL vs Price.
• Peerless NE149W- have a couple, great to look at, lacks in low end, top end, and smoothness, but priced attractively.
• Faital Pro 5FE120 - have some, was in consideration for a more pro oriented three way or a mini-monitor. VERY smooth extended top end; Qts best for sealed alignment. I think it would be a hoot to make a small two way with this and a DA25TX.

Considering the pricing of some of the parts you're looking at, I'd also give consideration to the Satori MW13TX-4

[technodanvan]

Well, you know Danny, everyone has an opinion, right? A few from me...

Thank you Jon, good stuff as always. I think I have to eliminate anything over $100 per. As much as the DA25TX would deserve that I suspect I'd blow the budget when it came to deserving crossover components.

I should also point out these gifts will be aimed at people who are not, at this time, audiophiles. One of which includes my goddaughter, who can currently count her age on one hand. While in her case I hope this will be a door to new and wonderful things as she grows up with them, the rest of the Gifties (working name) will go towards people who just love music, movies, and video games without critical listening being a thing. Given this context, and that other comparisons/studies have shown that, all else being roughly equal, folks will choose speakers with better/more bass than others, I feel bass performance of a given midwoofer needs to be near the top of the requirements list. Unfortunately, that is hard to come by in 8L!

In any case, our budget now being sub $100 that leaves the below available:

• Anarchy 558 - $66 - alleged F3 of 48 Hz in a bass reflex cabinet - I'm guessing I have 4-8 of these on hand already, maybe more. Some are probably the 554 though, which is NLA.
• MAC-05 - $25 - F3 of 86 Hz in a sealed cabinet as it does not seem to like small bass reflex enclosures - I have 2 on hand
• Faital Pro 5FE120 (or in this case, perhaps the 5FE125) - $55 - F3 of 108 Hz sealed, ~90 Hz ported - zero in my inventory
• Peerless NE149W - $86 - F3 around 84Hz - zero on hand

I'm crossing the NE149W off the list. I really want to like it but it's more expensive and doesn't do what the others can. The Anarchy is looking really good, plus I have a few of them already. The other two I don't know what to think about, I really want to use the MAC-05 to both support the MAC forum AND because I really like the silver look. Just tell me this doesn't look killer with purple! I also think it would go well with a slew of nonstandard colors, which I will indeed be using for the boxes.



Like you said though, the FaitalPRO also has some really nice things going for it. Problem is, bass performance on both the FE120/125 and MAC-05 is maybe a little lackluster.

For the record, here is the response and distortion on the $25 MAC-05 on an IEC baffle. I suspect you haven't had an opportunity to work with these so wanted to share to get your thoughts.









Keeping in mind I want to make around five (5) sets of these over the next two or so years, I'm at a point where the MAC-05 and Anarchy 558 would probably cost around the same due to the stock I already have in both, but I'd need to purchase the remainder NOW for either of them since both may be NLA once online stock is gone. The FaitalPRO seems to have high availability so I could purchase as I go, which would be convenient, and probably sounds the best (outside of bass performance) but also isn't as attractive as the MAC-05. It would also cost the most overall, depending on crossover design. I think any of them would play cleaner than most anything any of these folks have heard before.

I am torn.

[technodanvan]

So um...this 'simple' project kind of blew up.

Maybe it's because I didn't sleep much last night, but I started thinking about other possibilities. Perhaps I shall have more than one design ready to go depending on parts availability? I'm am now considering making all of the following designs as "ready to manufacture". Volume needs to stick around 8-10L total with a baffle no taller than ~12" in order to fit on my printer. Width can vary, but 7-8" seems most likely. If possible, I will try to use the same cabinet for each build. Crossovers need to be reasonably simple and elegant to fit in the cabs.

Mechano23 - CAD work nearly complete. New test baffle complete and looking like it may be the final version. Awaiting crossover PCB manufacture and arrival before finalizing the crossover brace(s). One set of tweeters and woofers in hand, so it'd be silly to not make at least one, but both parts are readily available and the BOM crossover parts are only around $100 USD shipped (sourced at Solen). I don't think I'll stray too much away from that design and will probably make several of these since I ordered 10 crossover boards (they were cheap and the minimum orders were either 5 or 10 so it made sense). This is kind of the baseline for comparison to the others, and costs around $162 for a pair of tweeters/woofers (Madisound).





Gifties - SB Acoustics SB26ADC tweeter in an augerpro elliptical waveguide and Midwest Audio Club MAC-05 midwoofer. Note I chose the aluminum (ADC) tweeter for this pairing because I was concerned the ceramic (CDC) tweeter color would not match the MAC-05 silver well. Part of the rationale for this tweeter is the ready availability of various elliptical waveguides from augerpro's website - a round waveguide may be too 'tall' given the height restriction of the speaker. My intent is to integrate the waveguide into the baffle as one piece and also have a version where the waveguide is simply attached to the baffle. Why? Mostly for color options. I have a weird intent to make a bright green cabinet, bright yellow baffle/rear, and bright orange waveguide/port. There will probably also be a white/light pink/light blue variant, among others. Anyway, I confirmed I have two MAC-05 drivers and will acquire some more shortly. I do not have any of the ADC tweeters, but they seem to have high availability. Around $166 USD for a pair of woofers and tweeters (Madisound and Jule Fidelity), should be a great value.

Gifties Extreme - SB Acoustics SB26CDC tweeter in an augerpro elliptical waveguide and Cinergy / Denovo Audio Anarchy 558 midwoofer. Same as above, probably make two different baffles here. Should be simple enough. I seem to have six 558 midwoofers (with more apparently available at Cinergy Audio for $66) and four of the 554. I'm also pretty sure I have a pair of the CDC tweeters lying around, though I didn't look for them this morning (and they may be dedicated to another project already). Basically $132 for a pair of these (for 2x tweeters, Madisound) unless I decide to make more than three sets, in which case it would be around $264 per pair. This would be the most expensive of the three variants if starting from scratch.

Gifties Supreme - Peerless DA25TX tweeter and FaitalPRO 5FE12X midwoofer. The 5FE120 has a sort of truncated bracket, the 5FE125 is round, either is easy with 3D printed baffles so it's mostly just a preference thing...and what will fit on the baffle given the large size of the Peerless mounting plate. I looked through my parts this morning and found 11 DA25TX tweeters, so all I'd need are the midbasses, which seem to have high availability at the time of this writing. JonMarsh, are you interested in helping with this one as you have all the parts tested already? Since I have 11 tweeters, I considered trying to tear one apart to see about making it fit one of augerpro's waveguides. Is that worth the effort given the stock performance? I'm open to thoughts. Since I have so many tweeters it'd just be the cost of the woofers, so the 'Supreme' would actually be the most affordable of any of these at $110 for a pair of the woofers (US Speaker), or $222 if starting from scratch (US Speaker / Parts Express).

So that's a lot, but I'll be indoors a lot too (due to the pending heat) and the CAD work is relatively simple, just time consuming. So then it's just the measurements and crossover work, which could be fun!