3D Printed Speaker Cabinet, Can we do better?

[theSven]

A coworker of mine found out I like speakers, and partake in the forum 😃. He shared a link with me that got me thinking can we do better with the designs shared on this site with the DIY community? My thought is yes, and this also would be fun to use the 3D printer for something other than printing Pokemon things for my kid.

Take a look at the video and share your thoughts on what you would do differently to take this design to the next level. Would Evil Twin keep the DSP design or go traditional? The cabinet design is interesting and I think it would be fun to work with Steve Manning on some of these designs. Of course I would have the most fun trying to paint the cabinet...

[technodanvan]

As far as the video is concerned, I don't think complicated shapes are necessary - the standard 'box' is a standard for a reason! Of course, I also only watched for a few minutes given my current time constraints.

All that said, I think 3D printing has a role to play in hifi beyond waveguides, ports, and prototyping, I'm just not sure exactly what it is. I think there would need to be a lot of experimentation to determine a good minimally resonant structure, but depending how it's made it could be nearly hollow so it could be filled with any manner of materials - sand, lead shot, epoxy, concrete....the list goes on, and it could be some combination of these (maybe lead shot with epoxy as a sort of damping material?). I could also see it being used for various speakers stands - short ones for sure, but even multi-component tall stands with integrated ports and hidden wire chambers could be possible. Again though, I'd think that would be best used in conjunction with other materials to ensure a strong, non-resonant structure.

[theSven]

As far as the video is concerned, I don't think complicated shapes are necessary - the standard 'box' is a standard for a reason! Of course, I also only watched for a few minutes given my current time constraints.

All that said, I think 3D printing has a role to play in hifi beyond waveguides, ports, and prototyping, I'm just not sure exactly what it is. I think there would need to be a lot of experimentation to determine a good minimally resonant structure, but depending how it's made it could be nearly hollow so it could be filled with any manner of materials - sand, lead shot, epoxy, concrete....the list goes on, and it could be some combination of these (maybe lead shot with epoxy as a sort of damping material?). I could also see it being used for various speakers stands - short ones for sure, but even multi-component tall stands with integrated ports and hidden wire chambers could be possible. Again though, I'd think that would be best used in conjunction with other materials to ensure a strong, non-resonant structure.

Did you see the part where plaster of Paris is used with glue? That was pretty interesting to a very affordable fill material. I agree with you 3d printing having a role. I have a lot to learn on the design side of things. My passion in DIY has been limited to assembly. I read so much on this site, especially lately as I'm trying to salvage all the posts that have images that don't link anymore. One thing HTGuide has is history, and with 20 years of history archived and searchable it provides a great resource to design into the future.

[JonMarsh]

Now, you KNOW I'm going to have a few comments- if I had more time (too much project stuff and house maintenance going on), I could have a lot more comments! But I went ahead and downloaded the video for future reference.

So, for today, I'm going to confine myself to his first statement (nice accent, BTW, reminds me of some of my friends...)

Well, OK, maybe just the title ("Building EXCEPTIONAL speakers using MODERN TECHNIQUES) and and his first statement ("Building homemade speakers that can compare favorably to manufactured units that have all manner of built in digital signal processors, precisely tuned ports, and calculated internal air volumes is hard! Simple boxes just aren't going to cut it anymore!")






Now, just a warning, my friends, you know I can't hear statements like these without considering it a challenge, if not a personal affront?


Especially his fundamental premise:

"Building homemade speakers that can compare favorably to manufactured units that have all manner of built in digital signal processors, precisely tuned ports, and calculated internal air volumes is hard! Simple boxes just aren't going to cut it anymore!"

Maybe we should have a vote, and the interested forum members can suggest which of a dozen or so systems selected at random from HT Guide best exemplify that you CAN do this?


And while we're at it, where can I get a 3D printer at reasonable cost (less than the total BOM budget for the speaker build) that will take care of printing this Mid-High module (forget the LF module... gotta be realistic, right?)










Follow up point: The two things have nothing in common- a 3D printer can print a good design or a mediocre design or a down right wrong design- 3D printer doesn't solve those problems at all.

It MAY be a useful tool for building some kinds of designs, but you know, woofers that are smaller than the midrange drivers is not how I usually approach things myself.

But then, I'd never call myself a "modern guy", either. Not with having been engaged in this activity for nearly 50 years.

Now, a nice high quality 3D printer for printing waveguides? Yeah, I think Auger Pro can tell you about that... and I think printing the front panel for the midrange-high frequency module I'm building could be easier, but I'm not sure the resulting part would be superior in performance to my maple Ply construction.

[JonMarsh]

Oh, and BTW, there's some things all manner of digital signal processing elements simply cannot do for a speaker crossover, which have been implemented in designs on HT Guide since 2005. And then, you're stuck with the local clocks and transmitters and formats used on those DSP boards- and the local DACs if analog outputs are provided.

[theSven]

Now, you KNOW I'm going to have a few comments- if I had more time (too much project stuff and house maintenance going on), I could have a lot more comments! But I went ahead and downloaded the video for future reference.

So, for today, I'm going to confine myself to his first statement (nice accent, BTW, reminds me of some of my friends...)

Well, OK, maybe just the title ("Building EXCEPTIONAL speakers using MODERN TECHNIQUES) and and his first statement ("Building homemade speakers that can compare favorably to manufactured units that have all manner of built in digital signal processors, precisely tuned ports, and calculated internal air volumes is hard! Simple boxes just aren't going to cut it anymore!")






Now, just a warning, my friends, you know I can't hear statements like these without considering it a challenge, if not a personal affront?


Especially his fundamental premise:








Maybe we should have a vote, and the interested forum members can suggest which of a dozen or so systems selected at random from HT Guide best exemplify that you CAN do this?


And while we're at it, where can I get a 3D printer at reasonable cost (less than the total BOM budget for the speaker build) that will take care of printing this Mid-High module (forget the LF module... gotta be realistic, right?)










Follow up point: The two things have nothing in common- a 3D printer can print a good design or a mediocre design or a down right wrong design- 3D printer doesn't solve those problems at all.

It MAY be a useful tool for building some kinds of designs, but you know, woofers that are smaller than the midrange drivers is not how I usually approach things myself.

But then, I'd never call myself a "modern guy", either. Not with having been engaged in this activity for nearly 50 years.

Now, a nice high quality 3D printer for printing waveguides? Yeah, I think Auger Pro can tell you about that... and I think printing the front panel for the midrange-high frequency module I'm building could be easier, but I'm not sure the resulting part would be superior in performance to my maple Ply construction.

I thought the concept was interesting to print small pieces and build them up, then fill in voids with the plaster of Paris and glue. It was interesting none the less I've never heard a crossover from you I haven't liked... If I had gotten into DIY in 2005 I'm sure I would have built many more kits that aren't available today. Modern is subjective... 50 years of knowledge is priceless!

[theSven]

I need to get a laugh button along with the like button. Your memes crack me up!

[JonMarsh]

Now, on the subject of MODERN design approaches, you know I can't let drop the idea of total design optimization using some of the best tools available, as exemplified in the SPK16 article, incomplete as the documentation is and as fuzzy as some of the critical pictures and graphs are...

🤣

I wouldn't be allowed to get away with that with my last day job!

https://purifi-audio.com/blog/tech-notes-1/spk16-reference-design-12

And the similarities between this and an "SMJ Internal" project currently on the back burner (Modula PWB, "Purifi-Wavecor-BlieSMa" which was evolving to Modujla PDB, "PuriFi-Dayton-BlieSMa" are significant, though a Visaton waveguide and BlieSMa tweeter combined with dual Dayton RSS210PR breaks rank- at least the woofer is the same, though there are two versions in consideration, one with the original PuriFi 6.5" paper cone 4 ohm and one with the aluminum NAA part.

Now, the SPK16 cabinet shown is a well designed box, with nicely radiuses corners and nice internal bracing- reminds me a bit of of the PSAudio FR30, and which... drum roll please... is made of MDF.



But speaking of my former day job, I'm still contacted frequently by the CAD vendors I worked with, and now I have a webinar scheduled on June 22 with... (another drum roll, please...) COMSOL, about speaker and microphone modeling. Ahem.

Too bad I don't do this for a living... being just an aging DIY curmudgeon.

So, maybe I SHOULD try this approach...






But you know, the pockets just aren't as deep these days as three years ago!

[JonMarsh]

Well, there is no try, only do or do not...

But, what about post, or post not? This discussion sort of revealed my hand prematurely about the Modula PBD project, and since I've got a few spare minutes before I leave on an errand, let's just say that the barebones concept is inspired by the SPK16 project, except that I knew nothing about that project, being as it hadn't been posted by PuriFi yet, and while ET can reportedly read minds and see the future via the Force, it's not one of my talents, not remotely.


But teasing you folks? That's right up my alley... my apologies that this is not NEW design work, but stuff we've been sitting on, because the engineering staff of me, myself, and I are pretty swamped in 2023...


Just two plots... first VituixCAD SPL plot with just PTT6.5X04-NAA measurements in a 16L sealed beveled edge cabinet, not rounded, no PRs, with TPL075 on tweeter duties (this is also one of the early "Scarlatti" concepts).


But I DO have a big honking roundover router bit, so doing something more like the SPK16 is quite feasible, cabinet wise...


And the current PR proposal, with a custom weighting configuration (the "goldilocks" version, as with the stock weight steps, you either wind up with "mama bear" or "papa bear"). 16L, two Dayton RSS210PR. You may be figuring out I like the look of the RSS210... and the performance, too.





This would probably be the smallest speaker system I've done in Eons, possible forever. 16 L net. Is that a speaker cabinet, or a cigar box?!?!!


And for those who say I should get off my duff and work faster, well, let me tell you, this is what my life feels like right now...

[theSven]

This would probably be the smallest speaker system I've done in Eons, possible forever. 16 L net. Is that a speaker cabinet, or a cigar box?!?!!


And for those who say I should get off my duff and work faster, well, let me tell you, this is what my life feels like right now...

Hmmm smallest cabinet ever... And that could lead into trying to print out a cabinet for a challenge to see if I could even figure out how to break the pieces down into sizes that would fit on the printer I have and then figure out how to fill it with Plaster of Paris and glue... Even though I know wood would be the perfect choice it's one of those why not try and learn something moments... My son has tons of media to use up for printing.

[technodanvan]

After discovering I have all the parts and plans necessary for 26 individual speakers and 2 subwoofers ranging from small to ginormous (i.e. BIGGER and HEAVIER than the SDX12 cabs!) - plus some additional parts on top of that...I don't know if I could stay married if I added a Purifi-based design to the list with even more Dayton PRs!

...but maybe I'll try anyway, cuz 17L sounds nice and this might replace my Helios aspirations since purchasing a few other Bagby designs. I need to be more selective though, so it better be good Jon. Like, really good. Like, approaching the best-you've-ever-done good. No pressure!

[JonMarsh]

Pressure? Try working as a Distinguished Engineer for an international semiconductor coordinating with teams in APAC and Europe. Especially when you have to convince some of them that how they're modeling and designing some classes of resonant converters is the wrong way to do it, just because the math is easier... and demonstrating the difference.

So, yeah, as needed I'm going to steal ideas to finish up this little baby up to your standards- that means I'll dig out those pricey oversized round-over router bits I have, and unlimber Shapr3D some more!

As a former Danish colleague was fond of saying,

"Steal from the best
and ignore the rest!"


One thing that deserves acknowledgment over and over again is how much power and analysis and design capability is at our fingertips in VituixCAD for DIY users- it's why I have a monthly contribution setup. Only seems fair. It goes so far beyond the capabilities of past tools that it is frankly amazing. We all owe a debt of gratitude to Kimmo.

Oh, and regarding those router bits...

Those are 1/2" shafts. 1.5" radius.

MLCS does these.




Keeping the crossovers small enough will probably be the tricky part.

[JonMarsh]

Hmmm smallest cabinet ever... And that could lead into trying to print out a cabinet for a challenge to see if I could even figure out how to break the pieces down into sizes that would fit on the printer I have and then figure out how to fill it with Plaster of Paris and glue... Even though I know wood would be the perfect choice it's one of those why not try and learn something moments... My son has tons of media to use up for printing.

Let a thousand schools of thought bloom in the sunshine...

[theSven]

Keeping the crossovers small enough will probably be the tricky part.

Maybe we can print the box that holds the crossover then and put it outside of the cabinet to admire? Some of these crossovers members have made on the forum are worth looking at and shouldn't be hidden inside the box in my honest opinion.

[JonMarsh]

Could be connected via a 4 conductor speak-on cable connector

[JonMarsh]

Which I checked my recollections, and located the bin of connectors and prebuilt 4 conductor cables...

[Steve Manning]

A coworker of mine found out I like speakers, and partake in the forum 😃. He shared a link with me that got me thinking can we do better with the designs shared on this site with the DIY community? My thought is yes, and this also would be fun to use the 3D printer for something other than printing Pokemon things for my kid.

Take a look at the video and share your thoughts on what you would do differently to take this design to the next level. Would Evil Twin keep the DSP design or go traditional? The cabinet design is interesting and I think it would be fun to work with Steve Manning on some of these designs. Of course I would have the most fun trying to paint the cabinet...

Conceptually a good idea, not new though. If done "right" you would be looking at something more along these lines.

[technodanvan]

Interesting design process, I wonder how the damping material is injected. Must be pretty dense if it's over 100 pounds by itself.

Proposal:

Create an inner box of 1/2" / 12mm Baltic birch. Well braced internally with 1/2"-3/4" ribs externally - also probably Baltic Birch, but aluminum stock (C-channel or square stock) could also be used at a 'relatively' low cost if we want to mix materials. Ideally the ribs would be glued, not screwed to the inner shell. Mount external shell with an epoxy or other adhesive - NOT screws - which could be additional birch or a 3D printed polymer. Use fine grain polymerized concrete to fill the gaps. This could be used on the baffle as well if you replaced the ribs with circular rings for the drivers.

https://en.wikipedia.org/wiki/Polymer_concrete

[JonMarsh]

Interesting ideas, Danny. I think I'd have to get that COMSOL setup and simulate it to see if it would make a functional difference compared with what I'm doing lately.

Otherwise, being an aging curmudgeon, I'd be inclined to employ the "KISS" principle (no, not YOU, Gene Simmons!). I probably already do things that are overly complicated for the desired results...


But I'm even thinking in terms of two possibilities for this Mini Modula, including a budget version with the original paper cone PuriFi woofer, plus my favorite budget SB Acoustics tweeter (SB26CDC-C0004) or that PT2522 in some modified version...

[JonMarsh]

After discovering I have all the parts and plans necessary for 26 individual speakers and 2 subwoofers ranging from small to ginormous (i.e. BIGGER and HEAVIER than the SDX12 cabs!) - plus some additional parts on top of that...I don't know if I could stay married if I added a Purifi-based design to the list with even more Dayton PRs!

...but maybe I'll try anyway, cuz 17L sounds nice and this might replace my Helios aspirations since purchasing a few other Bagby designs. I need to be more selective though, so it better be good Jon. Like, really good. Like, approaching the best-you've-ever-done good. No pressure!

Seriously, Danny, we don’t want to mess up your marriage. Due to my formal education in psychology and doing a couple of “interventions” with colleagues, I’ve actually helped save a couple of marriages, and feel somewhat responsible for an unplanned girl later in life who is now 13- so let’s keep that in mind!

So, I do think I should challenge you, though, to publish a list of all those drivers you have on hand… show us your hand, and I’ll show you mine!

[1Michael]

A new Modula project? I'm in. 😁 This time I might even be able to afford one of Steve's cabinets.

[technodanvan]

So, I do think I should challenge you, though, to publish a list of all those drivers you have on hand… show us your hand, and I’ll show you mine!

I'm pretty sure you have me beat a few times over, in both variety and sheer numbers! Most of my parts are spoken for:

Known Builds (parts in hand or on the way, including built crossovers for all but Jon's designs):
Carmody - Overnight Sensations TMM (Dayton ND20FA6, 2x B4N)
Carmody - Speedsters TMM (Fountek NeoCD 1.0, 2x Tang Band W4-1720)
Salin - Keramiskas (SB15CAC, HiVi ribbon of some variety)
Bagby - Auricle (RAAL 70-20, Satori MW16P)
Bagby - Revolution (Satori TW29TXN-B-4, Racetrack PR)
Bagby - Kairos (MW16P, TW29R)
Marsh - Natalie P Ultra LE (x3 [x5?], Peerless unobtanium tweeter, 2x RSS210HF woofers, probably sealed)
Marsh - SMJ-40 PE (one pair, GRS mid and tweeter, 4x RSS210HF woofers, 4x RSS265PRs)

Proposed Builds (parts in hand):
technodanvan - Ensemble Crescendo x3 - (large tower and center channel, each comprised of 1x Seas "King Coax" C18EN002/A, 4x DIY Soundgroup Anarchy 708 woofers, and 4x RSS265-PRs)
technodanvan - Ensemble Staccato x4 - (medium-ish tower each comprised of 1x MR18REX/XF coaxial and 2-4x DIY Soundgroup Anarchy woofers, probably ported)

Proposed Builds (parts NOT in hand):
Marsh - Modula PBD (one pair)
Linkwitz - LX521 (one pair)
technodanvan - JL Gotham Klone XL (one pair, RSS460HO x2 w/ DSP)
technodanvan - Possible upgrade to the Ensemble Crescendo using the Misco BWX-6502 XBL^2 or the Wavecor SW182BD-04
technodanvan - something with the CSS LD25X XBL^2 tweeter, perhaps with the Misco XBL^2 driver

Other drivers that I can remember...probably several more that I have forgotten in storage.

Epique 7" x2
Epique 5.5" x2
Baby RAAL x2 (64-10)
Ultimax 15 x4

Edit: I should add that the one thing I'd like to add to this list is a Linkwitz design, probably the Orion (scratch that the new[er] version, the LX521...I'm getting old I guess). It irks me a bit the manufacturer in the video a few posts above calls their speaker the Orion as well.

Edit2: Added a few more builds and clarified some others.

Edit3: Updated a few more things.

[tktran]

It’s alright, but unnecessarily heavy and large. 3-D printing is ideal for reducing cabinet size and weight. More scientific approach to reducing resonances via ribbing and/or use CLD approach Ala Augerpro than load it with plaster and turn it into a rock.

also venting via long ports could be replaced with passive radiators if you want small cabinets. And almost everyone does in this style of speaker.

[JonMarsh]

I'm pretty sure you have me beat a few times over, in both variety and sheer numbers! Most of my parts are spoken for:

Known Builds (parts in hand or on the way, including built crossovers for all but Jon's designs):
Overnight Sensations TMM (Dayton ND20FA6, 2x B4N)
Speedsters TMM (Fountek NeoCD 1.0, 2x Tang Band W4-1720)
Keramiskas (SB15CAC, HiVi ribbon of some variety)
Auricle (RAAL 70-20, Satori MW16P)
Revolution (Satori TW29TXN-B-4, Racetrack PR)
Kairos (MW16P, TW29R)
Natalie P Ultra LE (x3, Peerless unobtanium tweeter, 2x RSS210HF woofers, probably sealed)
SMJ-40 PE (one pair, GRS mid and tweeter, 4x RSS210HF woofers, 4x RSS265PRs)

Proposed Builds (parts in hand):
King Anarchy x3 - (large tower and center channel, each comprised of 1x Seas "King Coax" C18EN002/A, 4x 'Exodus' Anarchy 708 woofers, and 4x RSS265-PRs)
Mr. Rex Anarchy x4 - (medium-ish tower each comprised of 1x MR18REX/XF coaxial and 2x 'Exodus' Anarchy woofers, probably ported)


Other drivers that I can remember...probably several more that I have forgotten in storage.

Epique 7" x2
Epique 5.5" x2
Baby RAAL x2 (64-10)
Ultimax 15 x4

Edit: I should add that the one thing I'd like to add to this list is a Linkwitz design, probably the Orion. It irks me a bit the manufacturer in the video a few posts above calls their speaker the Orion as well.

I like the way you organized your response... but my replay is in someway simpler, and may be less complete, depending on how much time I'm willing to spend enumerating things on "hold" for now!


No commercial builds or kits.


Known design studies/builds in process with drivers on hand, some being updated, some near completion:


Isiris Update: RSS315HF, PTT6.5M04-NFA-01, BlieSMa T34B/T34A

Kurosawa: AS190-9-252, C173-6-724, D2908/7140 Tweeter, PRS223BD02

CC Supreme: PuriFi PTT8.0X04-NAB-02, PTT6.5MF04-NFA-01, Beyma TPL150H

Ardent PSB Supreme: PuriFi PTT8.0X04-NAB-02, SIG180-4, Beyma TPL150H

Saint-Saëns Planar: RSS210HF-4, PT-5010, TPL75

Modula PDB: PuriFi PTT6.0X04-NAA-08, TPL75 or T25B-6, RSS210PR

Modula ABD Supreme: Accuton C168-6-890, RSS210PR, TPL75

NeoDv JDV: Jantzen JA-6012, Vintage RS52AN, Visaton KE 25 SC

JADS- NatP HT: SIG180-4 with SB26CDC-C0004

Compact CCd: (Duelund three way) with SIG180-4, SB26CDC-C0004, mid TBD.

Compact Pro oriented CC: SST1 horn with DFM2635 or B&E DE500 driver, ES180TIA-8

Arvo Pärt Is dipole: UM10-22, PTT8.0X04-NAB-02, PT6816-8

Modula MX: NSD1095+XT1086 or DE990+ME90, Satori W024P-4, RSS265PR

Dual Force 15: STW-350F

DeathStar/JANUS Bandpass Sub: 15NW100, 15SW115-8

[technodanvan]

Was the Natalie P Ultra LE a Sith Lord project? I get them all jumbled up...

[technodanvan]

Anything to avoid actual work, of course! I should see about sourcing another pair of tweeters for a full 5 channels. Think it could make for a nice reasonably compact game room setup. Someday...

[JonMarsh]

That's really an ET project that he's farming part of the work out to me while he gallivants around in his Imperial shuttle. The days of Star Destroyers have gone by...

[JonMarsh]

theSven; Steve and I have talked about that and your interest, and I have set aside tweeters for you, from my NIB inventory.

[JonMarsh]

So, yeah, I should have listed that, too... like I said, easy to forget stuff, and this is now the closest thing I have to a "master list".

But there are wood parts already cut out, though not finished and assembled yet, and drivers on hand...

[JonMarsh]

A few updates to the project list above.

[technodanvan]

A few updates to the project list above.

Ditto! This isn't a bad place to keep a list, seeing as how I don't have one anywhere else.

To get back on the topic a bit, I am considering using my proposed build (with polymer concrete aka epoxy granite) in at least one of these. The question is, do I start with it on a small 2-way or go all out and make a several hundred pound monster tower?

Probably the 2-way, I guess. I'm tempted to use it on the Keramiskas even though I have technically started those by gluing the base/top/sides together. The baffle could still be used...

[JonMarsh]

I agree with you that the smaller system might be a much more practical “learning curve” experience!

You now, I don’t set out to build systems weighing over 100 lb, they just seem to “evolve” that way… the individual panel pieces of the Saint-Saëns certainly hint at “weight issues”, but what do you expect with maple ply and bamboo ply?

[technodanvan]

Where do you source your maple, Jon? A few online distributors I've seen only have thick (>1") wood available for pin blocks. I was curious if 1/2" - or even 3/8" - could be sourced. Perhaps bamboo should be the way to go for this...

[JonMarsh]

The maple I use is piano pin block, in 1-1/4" thickness. I source this from Vanda King piano showcase, who has several thickness. It's made from northern rock maple, and ain't cheap... neither are Magico or Wilson speakers.

Bamboo ply might be a reasonable choice- the original Isiris build was done with fossilized bamboo ply, which is used for flooring, and is very hard and strong. Also not cheap. Talk to Steve, he can fill you in more about the current market situation for bamboo ply. My last purchase through "normal" channels was in 2013.

For small builds I do use 12" wide bamboo strip boards from Woodworkers source. easy to handle, and very stable- used these in the Ardent D build for the sides.

The cabinets I'm building use the Maple Ply for front panels, top and bottom panels, and the back. The sides are a pure evil recommendation from ET, 1" bamboo desktops from Amazon. from VWINDESK- nice appearance, very stiff, and several sizes available- I use the 48" x 27". Not much waste cutting them to dimensions for the sides, and one panel can do both sides of the MF-HF modules. I'm using these on my NatalieP Ultra LE build, also- pieces already rough cut. Much easier to manhandle than 4' x 8' sheets.

[technodanvan]

Thanks Jon! I'm dangerously close to actually using my undergrad degree (materials engineering) on this one. I'll probably lean on others research instead of trying to reinvent the wheel though. Seems machinists use this stuff a lot and have done a lot of experiments.

Interesting ideas, Danny. I think I'd have to get that COMSOL setup and simulate it to see if it would make a functional difference compared with what I'm doing lately.

We'll have to figure out a way to compare based on more than just a knuckle test. Assuming 3/4" material would be employed using bamboo ply for most sides of the 'average' small 2-way project we'd need to calculate the total cost in bamboo vs ~1-1.25" of sandwiched polymer concrete. I can't see going thinner than that (1/4" ply on both sides, 1/2"-3/4" epoxy granite in the middle) since you're either compromising the forms (too thin and it might flex when setting) or it would be really difficult to pour (1/2" gaps seem like they'd work depending on how viscous the final product is, but wider would probably be better).

I priced out some aluminum bar for the ribs and it would probably make the total cost start approaching pin block levels - except I remembered 2020 T-Slot exists. Not only would that probably be stronger (based on its structure, and it's a fair bit larger than a 1/2") it would also have far more surface area for the epoxy to grab on to. It's also more affordable since manufacturers produce a lot of it. That said, for my first attempt I think sticking to plywood ribs would probably be fine.

Now I need to price out a DIY vibration table.

[JonMarsh]

Thanks Jon! I'm dangerously close to actually using my undergrad degree (materials engineering) on this one. I'll probably lean on others research instead of trying to reinvent the wheel though. Seems machinists use this stuff a lot and have done a lot of experiments.

Well, I'm having a "Dickinson" moment here, ya know, like, "Great Expectations"!

As I state loudly and frequently, I'm just the wires and sparks guy, not a real wood woodworker, and I'm winging it somewhat on mechanical design.

You can do the advanced stuff and I'll just bobble along with my old school approach for now.

Hey, maybe we could have a friendly contest of sorts on HT Guide, come up with the definition for the HT Guide answer to the SPK16 paper (definition as regards drivers, cabinet volume, external crossover) and let's see what entertaining variants in construction can be developed!

[tktran]

I think define the external cabinet volume

then go nuts!

[JonMarsh]

You take the high road, I’ll take the low road- I’ll define the internal volume needed for drivers, then go nuts!

I already have some ideas, roughly based on the Minerva project regarding construction and appearance style… and using Bamboo on hand and some other scrap materials. And yeah, I’ll probably go with an external profile like the SPK16 blog.

BTW, I attended a COMSOL webinar last week on speaker and microphone design; after I get home, I’ll post that here (it’s not proprietary) (heck, it’s’ an ad for COMSOL!). I spotted a COMSOL price list on Scribid So I’ll dig up my password and download that- note that the “Academic” version with Acoustics module is $895, so I shudder to think what normal folks would pay!

[Norm]

I have yet to personally do much 3D printing for my speaker projects. Most of the full speaker projects I have seen were little micro monitors of little interest. The one exception is a project by Benjamin Christian I learned of while following The HiFi Podcast. I have scooped the pics and description off Instagram and post them here to add to the discussion. I admire this design and build because they address some of the challenges, issues, and opportunities using additive vs subtractive processes. Such as:

• For a full size speaker, it will take so much filament and machine time. Christian has days, weeks, (months?) of print time in this pair. He is obviously an accomplished user of 3D CAD and has broken the needed shapes into clever subassemblies. I would love to ask him about total filament cost and scrap rates for this pair.
• Surface finish. In the many forms of 3D printing currently available when one spends enough very fine levels of finish are available. With that high cost often comes (at the present SOTA) smaller build volume capability. Christian addressed that by using the affordable filament DIY friendly printer and adding cost in as his sweat equity as the hours (oh so many hours) filling and sanding then painting.
• Material properties. Again, bring the money and sky is the limit, laser sintered titanium tweeter pod anyone? At medium cost level the carbon fiber filled filaments are approaching the strength of CNCed aluminum. I admire Christian’s solution to print with cost attainable material, assemble, then fill with a damping compound.
• Print what you cannot machine. I really admire the use of gyroid structures as visible through the open woofer holes. These are examples of a feature useful to the devices function that would be extremely difficult if not impossible to machine that is easy with layer based additive processes.

Link to and quote from The HiFi Podcast Instagram account description.
“https://www.instagram.com/p/CUbiGV8MVsa/”
Listener Benjamin Christian sent us photos of and the story behind his amazing DIY speaker project. From Benjamin:
“The speakers are my own design with Mark Audio 10p and 12pw drivers, they have an SB Acoustics beryllium tweeter. All the drivers are mounted in compression by threaded rings (like an individual lens in a larger camera lens) and are completely decoupled by o-rings. The woofers are a single unit and force cancel. The overall design is inspired by the work of Lawrence Dickie.
The cabinet is unique and is 3d printed in 3 main sections. It features a hollow 18mm wall which is later filled with 80 durometer pourable rubber. the bracing is created by an infill structure called gyroid which is highly isotopic yet permeable in all directions... like a highly rigid foam I guess. The result is an incredibly rigid and dampened structure. The two main cavities of the speaker feature my approximation of an exponential absorber and are both sealed.”
Bravo! We are incredibly impressed by his artistic skills and engineering acuity. Wish we could hear these beauties!

[technodanvan]

Interesting choice of drivers for that project! I like the honeycomb-style support structure, and I think using pourable rubber is a really solid idea. I can't imagine how much CAD work this required, it'd be well beyond my current skillset for sure.