DIY Aluminum Enclosure Speaker (CA5) Building Guide

[306xx]

This guide explains how to build a speaker with an aluminum enclosure. I designed the speaker using the waveguide for the SB26ADC made by @augerpro . Thanks to @augerpro for releasing all the drawings so that I could design the speaker. I hope this guide can inspire people who want to design their own aluminum enclosure speakers in the future.

PDF link: https://drive.google.com/file/d/1hTBLKORgGTOltmUg4CpEhTOgF5y6VoL5/view?usp=sharing

1. What to bring
https://docs.google.com/spreadsheets/d/1asfNiGf8bWuCD1tm__xDpQFnzZ7Du6s3C4IFWUEyy0k/edit?usp=sharing
Purchase all the supplies. Since this guide is made in Korea, the purchase links only work in Korea. You will need to search for suitable replacement parts yourself. There are drawings of the parts in the purchase link, so you should be able to find a replacement.
For the amplifier, you can buy any amplifier other than the Fosi V3. (You only need to match 4 channels)
For the aluminum CNC parts and 3D printed parts, you will have to make them yourself using the drawings or contact a machinist.
The final price depends on the machining costs, and I spent around $2000 for everything.

2. Machining
CNC drawing files: https://drive.google.com/file/d/1vK7v80REkIuRLbBdPThlD5r7apYcPClw/view?usp=drive_link
3D printing drawing files: https://drive.google.com/file/d/1ley7UBcsolubH278k8h1brl-dyQTPoFo/view?usp=drive_link
The README file in the zipped file explains the machining method and quantity.
Do your own aluminum machining and 3D printing as you see fit.

3. Assembly
① Attach the waveguide to the front panel. At this time, attach foam tape between the waveguide and the panel to prevent unnecessary vibration. (8 x M5-10mm wrench bolts)

② Disassemble the SB26CDC tweeter and mount it on the front panel. Apply foam tape between the waveguide and the front of the tweeter, and also between the aluminum bracket and the back of the tweeter. (Aluminum bracket, 2 x M4-60mm wrench bolts, several washers)

③ Mount 3 HBKTST5 and 1 HBKTST6 on the side panel. (3 x M5-10mm wrench bolts, 1 x M6-15mm wrench bolt)

④ Drill M8 tapped hole in the HBKTST6. (Use the hand tap set)

⑤ Mount four HBLCR5-S to the side panel. (4 x M5-10mm countersunk bolts)

⑥ Drill M6 tapped holes in the two HBLCR5-S located at the bottom of the side panels. (Use the hand tap set)

⑦ Assemble the opposite side panel in the same way and drill the tapped holes. (3 x M5-10mm wrench bolts, 4 x M5-10mm countersunk bolts, 1 x M6-15mm wrench bolt, 1 x M8 tapped hole, 2 x M6 tapped holes)

⑧ Apply foam tape to the back panel and join it with the side panels (4 x M5-10mm countersunk bolts, 2 x M5-10mm wrench bolts).

⑨ Apply foam tape to the top panel and assemble it to the enclosure. (4 x M5-10mm countersunk bolts, 2 x M5-10mm wrench bolts)

⑩ Mount 4 HBKTST5 brackets to the aluminum profile and assemble them to the enclosure. (8 x M5-10mm wrench bolts, 4 x LNTN6-20-5 profile nuts)

⑪ Apply foam tape to the front panel and mount it to the enclosure. Connect the wires before mounting. (4 x M5-10mm countersunk bolts, 2 x M5-10mm wrench bolts)

⑫ Apply foam tape to the bottom panel and mount it to the enclosure. At this time, apply foam tape to the bottom panel screw holes to prevent air leakage. (2 x M8-20mm countersunk bolts, 4 x M6-15mm countersunk bolts)

⑬ Install the SB15CAC30 woofer and the Neutrik NLT4MP-BAG spicon terminals and connect the wires. Since it is a 4-pin terminal, use crimp terminals to connect both the woofer and tweeter. (4 x M4-10mm countersunk bolts, 4 x M3-8mm countersunk bolts)

⑭ Attach the SB13PFCR passive radiator. (4 x M4-10mm countersunk bolts)

⑮ Assemble one more unit.

4. Tuning
① Place the measurement microphone at the same height as the tweeter as shown below and measure from 1 meter away.

② Measure the tweeter and woofer at the same location and set the time window to 5 ms. (The measurement position should be adjusted so that the first reflection is not heard within 5 ms.)
An example of the measured tweeter and woofer measurements is shown below.

③ Then, calculate the bass range measurements from the nearfield measurements of the woofer and passive radiator and add them to the existing woofer measurements. The detailed process can be found at the following link.
https://audiosciencereview.com/foru...ents-spinoramas-with-rew-and-vituixcad.21860/

④ EQ the tweeter and woofer measurements using REW's Auto EQ feature.

⑤ Apply 1.3 kHz L-R 48 dB/oct crossover filters to the flattened tweeter and woofer FRs.

⑥ Apply the resulting EQ and crossover filter values to the Minidsp 2x4 HD.

 

[306xx]

The CA5 was measured by @Nuyes using Klippel device. The measurements were as follows.
More measurements and explanations of the measurements can be found at the following link.
https://audiore.kr/ca5-diy리뷰/

 

[kongkong]

Nice works !

 

[Rick Sykora]

Congrats as this is an extraordinary effort and you managed a great result. I had already seen most of this over at diyaudio.com, but since you reposted here…

1. How much did the enclosure cost and what benefit did you achieve over using MDF?
2. Is there more detail posted somewhere on the minidsp crossover?

 

[306xx]

Congrats as this is an extraordinary effort and you managed a great result. I had already seen most of this over at diyaudio.com, but since you reposted here…

1. How much did the enclosure cost and what benefit did you achieve over using MDF?
2. Is there more detail posted somewhere on the minidsp crossover?

Hi, thank you for your interest in my project.
1. my enclosure was made by an aluminium CNC specialist, I paid around $500 for it. In my opinion, the advantages of aluminium enclosure over MDF are as follows
1-1. no need for clamps and large workspace.
One of the inconveniences of making MDF enclosures is that you need a large, well-ventilated workspace, but aluminium enclosures are more like building Lego, so all you need is a desk, screwdriver, and bolts. This is a huge advantage for DIYers who don't have a garage.
1-2. No resonance.
I used 10T aluminium and the bracing is also made of aluminium profiles. There is no unnecessary resonance.
1-3. Large internal volume for its size.
MDF is thicker than 18T and requires bracing to suppress resonance, but aluminium enclosures are more rigid even with half the wall thickness, so they can be designed compactly. In my opinion, when designing speakers for desktop PCs, aluminium gives you the best performance to size ratio.
1-4. The most important advantage is that it looks cool.
Black anodised aluminium is sexy, isn't it?

2. I have never written much about the minidsp crossover settings.
I set the crossover via VituixCAD simulation and found that using the LR48 filter at 1.3khz was a very simple way to make the vertical directivity wide.
I designed these speakers for a nearfield desktop PC, so wide vertical directivity and compactness were the main design directions. I designed an aluminium enclosure for the compact size, and for the wide vertical directivity, I kept the CTC distance as short as possible and used a low crossover frequency and steep crossover filter.
Thanks to a good waveguide and tweeter, the 1.3khz crossover did not damage the tweeter and I was able to achieve wide vertical directivity. I built my crossover setup with a 70-point off-axis measurement, but others only need a single on-axis measurement.
Because of speaker unit variation, I think it's better to take your own measurements to set the crossover, but if you need the filter I use, I'll upload it.

 

[DWPress]

Congratulations on the project - great to see something so obviously well thought out. Even better it measures as well as I bet it sounds.

$2000 seems reasonable for prototyping, raw materials and finding the machinists to create the pieces even here in the USA.

 

[SSS]

My ACRON full aluminum case loudspeakers from 1976 which I still use at my PC. Still sounding good.

 

[MCH]

Hi, thank you for your interest in my project.
1. my enclosure was made by an aluminium CNC specialist, I paid around $500 for it. In my opinion, the advantages of aluminium enclosure over MDF are as follows
1-1. no need for clamps and large workspace.
One of the inconveniences of making MDF enclosures is that you need a large, well-ventilated workspace, but aluminium enclosures are more like building Lego, so all you need is a desk, screwdriver, and bolts. This is a huge advantage for DIYers who don't have a garage.

You have very good points here. I have just checked at jlcpcb and it would cost roughly 600 eur for the pair shipping and tax included to EU, and this for decent size speakers. I hope projects like this become more common.

 

[Timcognito]

Very Cool. Thanks for sharing.

 

[jcr159]

everything has a resonance frequency... have you run some impedance sweeps and/or impulse waterfalls that might show any ringing?

folks falsely think that concrete cabinets don't resonate, but they do... aluminum does as well, but I'm guessing the frequency is pretty high rather than low. Not sure if it makes any difference in the sound or not...

Anyway, interesting build and super unique!

 

[Salt]

Next step: sandwich

 

[306xx]

have you run some impedance sweeps and/or impulse waterfalls that might show any ringing?

I have never done any measurements that would intuitively show cabinet resonance, and I apologize for claiming that there is no resonance without any objective basis.
I know that stereophile.com uses accelerometers to measure resonance, so I will try that in the future.
I have measured the resonant frequencies of haptic devices with accelerometers during my master's degree, so I don't expect it to be difficult.
Let me explain why I claimed that there is no resonance.

I've used DIY MDF speakers before.

These speakers had very good directivity performance, but they had a lot of cabinet resonance, which showed up as high-order harmonic distortion (HOHD) in THD measurements. So I assumed that strong cabinet resonance could be shown using HOHD measurements.

These are the measurements of those MDF speakers. (Thanks again @Nuyes )

You can see that the CA5s have very low HOHD measurements, unlike this MDF speaker, so I assumed that the resonance had disappeared with the aluminum cabinet.

However, to show conclusively that the resonance frequency does not exist within the audible frequency, an accelerometer measurement is required. Again, I apologise for my hasty logic.

 

[jcr159]

I have never done any measurements that would intuitively show cabinet resonance, and I apologize for claiming that there is no resonance without any objective basis.
I know that stereophile.com uses accelerometers to measure resonance, so I will try that in the future.
I have measured the resonant frequencies of haptic devices with accelerometers during my master's degree, so I don't expect it to be difficult.
Let me explain why I claimed that there is no resonance.

I've used DIY MDF speakers before.

View attachment 386554

These speakers had very good directivity performance, but they had a lot of cabinet resonance, which showed up as high-order harmonic distortion (HOHD) in THD measurements. So I assumed that strong cabinet resonance could be shown using HOHD measurements.

These are the measurements of those MDF speakers. (Thanks again @Nuyes )

View attachment 386548
View attachment 386549
View attachment 386550
View attachment 386551
View attachment 386552

You can see that the CA5s have very low HOHD measurements, unlike this MDF speaker, so I assumed that the resonance had disappeared with the aluminum cabinet.

However, to show conclusively that the resonance frequency does not exist within the audible frequency, an accelerometer measurement is required. Again, I apologise for my hasty logic.

Thanks for the response. an accelerometer measurement would be interesting for sure. typically folks run a set of impedance sweeps of each driver mounted in cabinet using something like the Dayton DATS device... those impedance graphs will show "jaggies", or irregularities where resonances are impacting the system...

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