# 3D printing of speaker enclosures



## deepthought (Jun 5, 2013)

Hello,

First post, be gentle.

I've been working on a project for some time, modelling some quite complex speakers in my 3D software with the intention of using a 3D printer to make them. I was interested to see if anyone has any links or experience in any equations that can be used to predict the resonances of a given material based on its density, stiffness etc. I have had a good look on the internet to see if there are any papers out there but couldn't see anything. If there isn't anything out there then I wonder if anyone of the forum have any empirical experience with the acoustic qualities of PLA plastic? I am getting me smaller prototypes made up but I'm interested to see if anyone has used PLA or ABS in a similar or related application. 
Thanks in advance.






:help:


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## NBPk402 (Feb 21, 2012)

I have seen on the internet where a speaker was made with a 3d printer... I think it would be awesome to make. Subscribed to see how it works out for you. :T


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## jaguar717 (Sep 8, 2014)

I'd also like to see how this goes...


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## jamesfrazier (Jul 24, 2011)

My roommate is an engineering major and have the software to design things like this. He also has the ability to use the new 3d printer now on campus. Looking forward to your project and may follow suite if it works well for you.


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## AudiocRaver (Jun 6, 2012)

Looking forward as well. Especially to what it sounds like. Could be fun.


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## deepthought (Jun 5, 2013)

I've just finished the first few parts of the enclosure in the printer. This is a VERY slow process. There are 8 pieces per speaker enclosure and the total print time is about 1000hours eek. The PLA material is really dense and seems quite non-resonant. Haven't done any proper tests yet but this stuff seems better than MDF - which is the material I am most familiar with from previous projects. Interestingly, MDF is about 700kg / cubic metre compared to PLA at 1300kg / cubic metre which is around twice the specific weight so perhaps this may contribute to its lack of resonance. Perhaps a materials scientist can offer some insight here?


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## AudiocRaver (Jun 6, 2012)

This really is a very interesting project. We are anxious to see pics when you are able.


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## deepthought (Jun 5, 2013)

Well I managed to hobble together some photos of the initial prints. Apologies for the quality - I am having issues with my DSLR camera and hopefully this will get sorted soon. 
These are the first 2 segments. I have 2 other ones completed that I still need to pick up from the people doing the 3D print. The larger part that will in part house the front woofer took, wait for it, 110 hours to print. We have tweaked the settings a bit and have gotten the total print time down to about 800hours per speaker. Yeah, do the maths on that one 
The dark brown material affixed to the inside of one of the panels is product from an Australian supplier called Megasorber D10. To quote the manufacturer "(it) is a polymer blend designed to provide high visco-elastic damping properties.". The product is faced with a glass-fibre mesh that reduced sound transmission - tests were done by a laboratory in Melbourne where they fixed it unto 25mm polyester foam found that "it boosted the sound absorption from NRC 0.55 to NRC 0.85". I haven't tested this in my application - I think I need to get hold of a guitar pickup and do comparative tests on the affects of a signal in a speaker enclosure with and without it applied - maybe a future project.

More photos and comments to come.


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## deepthought (Jun 5, 2013)

whoops.


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## deepthought (Jun 5, 2013)

More info":

Drivers are:
RS225-4, Scanspeak 10F, Seas 27TBFC/G. All nice safe bets - all low distortion and good value. I'm really trying to discover the limits of 3D printing and I don't want the extra stress of fiddling with crossovers as well .
This will be a 3 way obviously and I'm looking at crossover points of around 300hz and 5000hz as targets. Enclosure volume is 32litres.

I'm using a mix of Jantzen caps and coils with superior Z's on the tweeter, and standard Z's in line with the midrange. I'm not a capacitor obsessive so I'm going for a performance / price balance here. 

Using this type of design process allowed me to incorporate a lot of "difficult" design principles.
I have an offset in the front baffle to allow for the voice coil offsets between the tweeter and the mid-range. I also have a sub-enclosure for the mid and tweeter to isolate them from the woofer.
I have incorporated extensive horizontal and vertical cross bracing and the internal faces are reasonably complex to reduce internal standing waves.
The box is a sealed design. I'm not going to get into arguments about what's better but suffice it to say that I have wanted to execute an extended range sealed design for some time.
I have paid a lot of attention to baffle refraction - again the 3D printing process makes this quite easy to execute.


Happy to answer questions.


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## tonyvdb (Sep 5, 2007)

What are the costs involved in using a 3D printer for a project like this?


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## NBPk402 (Feb 21, 2012)

I remember a while back where the speaker driver was even made with a 3d printer. Not sure how the cone was made though... Not to mention a magnet.


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## deepthought (Jun 5, 2013)

Here is Australia, decent PLA starts at bout $26 a KG but you can get cheaper if you extrude the plastic from its pellet form rather than buying it ready-made. You can get down to $8 per kg's this way. Total weight of the speaker pair will be about 20kg.


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## deepthought (Jun 5, 2013)

I'm not sure how successful that would be but it could be fun to try. You'd need a very high resolution on the print and a material with a very good weight / strength ratio I'd imagine. Interestingly there is an ABS filament that has carbon fibre embedded in it in what would be random shards - much like a paper-composite driver. I am not going to attempt this though as I'm more than happy to leave the creation fo the drivers to the experts!


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## alfa-74 (Aug 31, 2013)

Subscribed, this project looks very interesting


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## deepthought (Jun 5, 2013)

Well "speaker 1" has been pushed out of the printer in its entirety. What a time consuming process that was!
Got some pictures of everything ready to be finished and slotted together. Speaker 2 is started to get printed today. Hopefully with the lessons learnt and without the false-starts that come along with learning how to get the printer working reliably this will be a lot smoother. I really have to thank the 3D Printer guy who did all this for his patience and help!
 

 

 

I'll post next about the crossover design.


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## deepthought (Jun 5, 2013)

BTW, PLA plastic is very dense. It weighs in at 1.6kg per litre, or 1.6 tonnes per cubic metre. That puts it at about 2-3 times denser than MDF. In terms of resonance I am very pleased with the result. I am going to get hold of a piezo guitar pickup at some point to try to do some comparisons. That's a long term project though.


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## NBPk402 (Feb 21, 2012)

Looks great! So how expensive was it to make one cabinet (materials not including 3D printer)?


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## deepthought (Jun 5, 2013)

Ok, so I got my new laptop, my Behringer UMC204, my calibrated Dayton EMM-6 mic and set the speakers up in an outdoor measuring area.

This is a spliced "full range" frequency graph - though note that there is a high-pass at 70hz on the measurements so I expect an F6 of about 45hz. I am very pleased with the flatness of the response and this is without any conjugate network measures. I did choose "safe" drivers for a reason - I wanted ones that would get me a flat response without having to wrestle with their response. The design of the enclosure assisted me in achieving a simple (if not text book) crossover without even having to use a zobel on the midrange!

 

The graph shows the midrange wired out of phase (as it should be in a 2nd order crossover) and in-phase. Note the deep nulls at the crossover points. If you look in more depth at the graph you can see a reasonably recessed midrange with a rising upper midrange - treble. Perhaps this is not to everyone's tastes but I like it and after all I am the one who has to listen to it. Another surprise (shock) that you might see is the midrange to tweeter crossover point of about 8500hz. What was I thinking (you're thinking). Well the Scanspeak 10F is intended as a full range driver and the baffle tapers as it rises so extending the crossover point up seems to have done no harm - the 10F has a naturally rising midrange - treble region so this would mean that the off axis should if fact flatten out and not be recessed as it would with say a 5½ or 6½ mid/bass. Don't believe me?

 

I took measurements at 15 degrees off axis and on-axis. 
Green is "on axis" that is, the mic is at about 550mm (nearfield) aimed directly at the point between the centre of the tweeter and the midrange - I was trying to simulate the listener's perceived response here. 

Blue is 15 degrees off axis horizontally to simulate the response if the speakers are not toed in to the listener. No surprises here perhaps but thanks to the SEAS 27TBFC/G tweeter, the F6 is still at about 18 kHz - not so shabby. Plus the phenomenon of the dropping response in the SS 10F actually makes the upper midrange flatter which I think is perceived as a slightly less "presence" but without any ugly hollowness or aberrations in balance.

Red is 15 degrees of axis above the speaker. I felt that since these speakers were going to be on my TV unit when I install them at home, a lot of listening will be done with my head above the speaker. A few things to note. NO SUCKOUT at the crossover region! I did some tests with crossovers at more conventional frequencies - in fact I was originally aiming for 5khz and when I did off-axis measurements with this setup I got a 6-8dB dip at that frequency. I did quite a few measurements to make sure this was correct - I actually couldn't believe it was that good. :blink: This measurement does seem to show up some recessing of the midrange but you can't defeat the laws of physics I guess......

I have some questions on the measurements for the midrange to woofer crossover in my next post so if anyone can offer opinions that would be appreciated.


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## deepthought (Jun 5, 2013)

This is where I ask for a bit of input into my measurement technique. I was (am) concerned about the means to accurately measure the mid/woofer response. The crossover is in the 300-400hz region. My calc's tell me that a nearfield measurement should theoretically only be useful up to about 480hz given the width of the baffle and the woofer diameter. My concern is that any inaccuracies are pretty much inside the critical crossover point and that this will impact on the accuracy of the tests.

 

I am confident of the levels between the 2 drivers. I did a lot of nearfield and farfield comparisons on levels. I even did some tests using an SPL meter as a sanity check. I also did testing of nearfield without any attenuation on the midrange. Once I added the L-pad, the levels dropped to what I had estimated in my design software so I am convinced this is correct to within +/-1dB.

If you look at this graph you can see the two nearfield measurements that I used to get the woofer and midrange response. I was able to get a good long gate time for the woofer so the lower response looks pretty much as I expected. There also don't seem to be any strange things going on as the frequency rises on the graph so that looks quite positive.

On the other hand, I did have issues getting a long gate time on the nearfield of the midrange. I have a sub enclosure for the midrange and the tweeter and I have filled this with acoustic baffle but I was still unable to get a measurement that didn't seem to have some back-reflection on the sub-enclosure wall (I think) so I am a bit dubious about the low frequency fall-off of the midrange. If I manually ignore the gateing and push it out in time, I do get a different falloff which (intuitively) seems to be more realistic. I don't know if that would be an acceptable practive though! :R

The graph below shows the midrange falloff using the programs estimation of the first reflection (i.e a relatively short gate time). I can get a nice deep null if I calculate the difference between these 2 graphs (see previous post), but, is this a fiction? :help:
Needless to say, if I push the gate time out manually then I get a quite different result. 

So I guess my question is, would anyone have any insight into how I can get better measurements than this and on the flip-side can I (or should I) push the gate time and ignore the reflection picked up in Holm Response?

Awaiting any thoughts..........


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## deepthought (Jun 5, 2013)

Ron, I used about 26kg of PLA all up. I Australia you can get this from $26 a KG for the 2 cabinets. So about $670 plus drivers plus crossover, parts, damping material and so forth for whole build. Not a budget build by any stretch of the imagination but I did integrate a lot of design goals into the enclosure such as time alignment, low baffle refraction, enclosed midrange, internal bracing etc. without any extra cost. In 3D printing, complexity generally costs the same as simplicity!


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## deepthought (Jun 5, 2013)

Just wanted to "bump" the thread. Has anyone had any thoughts on my last question?


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## robbo266317 (Sep 22, 2008)

Maybe you should post the question in the REW forum, where it will get the attention it requires, and link to this thread . 

I must say it is a nice looking speaker you have designed and the cost is reasonable for such a bespoke item! 
You mentioned that you thought internal cabinet reflections may be an issue, have you thought about lining the rear with something like carpet underlay?

BTW Why are you up at 12:45 am?


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## deepthought (Jun 5, 2013)

I'll post that part of my question over there - I didn't think of that. 

To address the issue of possible vibrations, I purchased a sheet of Megasorber D10. These guys are in Melbourne BTW. The D10 is a self adhesive sheet of "polymer alloy" finished with a coating of a product called "soundmesh". The polymer acts as a damping material and the soundmesh acts to internally absorb reflections. I am coating the internals now and I'm yet to do some tests to see how effective it is. I will also being using acoustic blanket internally. Inside the mid/tweeter enclosure I am using a product called Ecopanel from an aussie company called Wovenimage. This is a 50mm thick panel made of PET that has an NRC of .95 - I will place this on the rear of the sub-enclosure to absorb back reflections. 

In terms of cost, due to the fact that I knew a guy who kindly volunteered to do the print "at cost" I was able to get the thing done at some reasonable figure. For the majority of people, they would either have to pay a 3D print shop to do it - which based on my estimates was going to cost me thousands OR buy a printer. The good part about buying your own printer is you get to reuse it later of course. You can get some good printers with reasonably large print volumes such as the UP! Plus 2. The prices are only going to go down on these printers which is good news.

On your last question, I do go to bed late, it was 11.45PM local time when I posted (Brissy).:yawn:


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## robbo266317 (Sep 22, 2008)

deepthought said:


> In terms of cost, due to the fact that I knew a guy who kindly volunteered to do the print "at cost" I was able to get the thing done at some reasonable figure. For the majority of people, they would either have to pay a 3D print shop to do it - which based on my estimates was going to cost me thousands OR buy a printer. The good part about buying your own printer is you get to reuse it later of course. You can get some good printers with reasonably large print volumes such as the UP! Plus 2. The prices are only going to go down on these printers which is good news.
> 
> On your last question, I do go to bed late, it was 11.45PM local time when I posted (Brissy).:yawn:


I agree, the cost will fall over time and I expect to see the use of more exotic materials as well to fill niche markets.

As for the time, I guess up north you don't need daylight savings.


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## NBPk402 (Feb 21, 2012)

deepthought said:


> Ron, I used about 26kg of PLA all up. I Australia you can get this from $26 a KG for the 2 cabinets. So about $670 plus drivers plus crossover, parts, damping material and so forth for whole build. Not a budget build by any stretch of the imagination but I did integrate a lot of design goals into the enclosure such as time alignment, low baffle refraction, enclosed midrange, internal bracing etc. without any extra cost. In 3D printing, complexity generally costs the same as simplicity!


I was just curious... I knew it would be expensive to go this route, but with time the prices will come down, and there will be a lot of DIYers doing this too. It also is a custom speaker that you designed, and should be very proud of. Keep up the great work! :T:T


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