Disassembly and analysis of the internal structure of Amazon's fourth-generation smart speakers

Amazon focused so much on improving audio quality with the 4th-gen Echo Dot that I had to buy one for myself specifically for teardown purposes. I suspect the 4th-gen Echo Dot's larger size than its predecessor means there's a larger acoustic suspension cavity behind the speaker, which is the root cause of Amazon's claimed bass-centric sonic improvements.

In my April 2021 teardown of Amazon’s third-generation Echo Dot “smart speaker,” I wrote:

"The latest 4th-gen model is more radical in appearance, though given how common it seems to be to mount the Echo Dot stand to a wall, connect it vertically to an outlet, etc., I suspect the "friendlier" (for such configurations) 3rd-gen model still has a noteworthy future."

Aesthetic issues aside, Amazon focused on improving audio quality when it launched the new model in September 2020:

“It’s compact, yet features powerful 1.6in front-facing speakers that produce crisp vocals and balanced bass, giving you full sound in any room of your home.”

So I had to buy one for myself (on sale for $24.99 during Amazon's Prime Day sale in June 2021, bundled with a free smart bulb, which I tore down in August of the same year) specifically for teardown purposes. I suspect the fourth-gen Echo Dot's larger size than its predecessor (same diameter, but about twice as tall) means there's a larger acoustic suspension cavity behind the speaker, which is the root cause of Amazon's claimed bass-centric sonic improvements.

Let's see if I'm right. As usual, I'll start with some unboxing shots... starting with the box:

Finally, a close-up of the bottom label:

Time to open the top:

The cardboard insert on the right holds the barrel-plug power supply:

Its specifications are shown in the close-up below:

There are two thin files under our teardown object:

Now for some overview photos of the Echo Dot (3.9×3.9×3.5in, 12oz), with a US penny (0.75in/19.05mm diameter) for size comparison as usual:

There are two connectors on the back; the aforementioned barrel-plug power input, and a 3.5mm TRS for audio-out purposes (if, for example, you want to connect the Echo Dot to a more powerful external speaker rather than using the integrated transducer).

From this specific perspective, another interesting (to me, at least) design change from the third to fourth generation Echo Dot is that the open mesh covering no longer extends all the way around the device, as opposed to the similarly spherical Apple HomePod mini in the image below:

The resulting sound output is not omnidirectional, a fact Amazon acknowledges; note the reference to "front-facing speakers" in its early press release quotes. Turn the Echo Dot upside down and, unsurprisingly, you'll find a round rubber "foot":

Also unsurprisingly, based on my past teardown experience, peel it back and you'll find four exposed T6 Torx screw heads underneath:

Here’s a close-up of the still-intact product label, recording the FCC certification ID and other information details; the cluster of production line test and programming contact points for the exposed PCB on the bottom are also now clearly visible (the purpose of the circular holes in the exposed PCB on the top, which I’ll come back to later, was less obvious to me, and readers are welcome to suggest them):

Remove the screws:

The two halves of the housing separate cleanly and easily:

This is what the inside of the base looks like:

Note that in previous Echo generations, the status LED ring was on the top of the device, but this time it’s on the bottom. The translucent plastic ring spreads the LED illumination more evenly around the base. Speaking of LEDs, let’s take a look at the PCB that’s now exposed on the other half…

Note the 12 multi-color LEDs around the circumference. Managing them is a Texas Instruments (TI) LP5036 36-channel I2C constant-current RGB LED driver, which can be found on the bottom of the PCB. To the right of it is a group of passive components, exposed to the outside through the aforementioned circular hole in the base… again, readers are welcome to suggest them. Above them is a Faraday cage, and what’s inside is always a curiosity, so hold on to that thought. In the upper left corner of the PCB is another Texas Instruments IC, this time the company’s TAS5805M high-efficiency dual-channel closed-loop Class-D audio amplifier, which I believe is what drives the (mono) speaker. To the right of it is a MediaTek (MTK) chip labeled MT6398AN, the functionality of which eluded me despite numerous Google searches. Research for the article “Amazon Echo Dot 4th Gen Smart Speaker Teardown” was equally fruitless, but its author Brian Dorey suspects this particular IC is a switching power supply. Below and to the right of it is a Diodes PAM8908 dual-channel 25mW headphone amplifier, which is used to drive the Echo Dot's 3.5mm TRS audio output. Speaking of which... before removing the screws that I suspect are holding the PCB in place, let's take another look at those power and audio output connectors:

Now for those T5 Torx screws:

Hey, I was right! Judging from the heat tape, I guess there's a processor underneath this Faraday cage:

Let's disconnect that ribbon cable to free the PCB completely from the tether:

Speaking of cables… In the process of finishing this post, I came across this mini teardown from iFixit. Notice that the 4th-gen Echo Dot they tore down has two cables between the PCB and the rest of the top half of the assembly: the same ribbon shown here (connected to the top switch and microphone, and any associated circuitry for them), and another ribbon that connects to the auxiliary LED panel. The top auxiliary LED panel appears to have been removed from my version of the device. While I’m on the subject of interconnects, note the two electrical contacts on the speaker housing, at the top of the earlier photo. They match up with the two contacts on the bottom PCB in the same photo. I’m guessing this is how the Class D amplifier on the PCB connects and drives the speakers. Back to the PCB:

Now focus on the side we haven't seen yet:

At the bottom is MTK's MT7653BSN combo 802.11ac Wi-Fi + Bluetooth 4.0 controller. You can also see the associated embedded antennas on either side of the PCB, along with the traces between them and the IC. And of course, at the top are the power and audio connectors. Before we move on to removing the Faraday cages on either side of the PCB, let's take a look at two more views from the side:

Now to take off the top of the Faraday cage! Normally, a thin flathead screwdriver would be enough, but these cages are way too stubborn. I eventually did the trick by first using a solder loosening heat gun on them, then using the screwdriver as a lever arm. First side (bottom) first:

The IC that is now exposed is a strange IC from a closed perspective: Kioxia (formerly Toshiba Semiconductor) TC58CVG2S0HRAIJ 4Mb serial NAND flash memory. The chip with the same function from Micron was used in the Echo Dot that Brian Dorey disassembled earlier. Flip the PCB:

We are only halfway there:

Time to get out the heat gun again:

After wiping it clean with alcohol, we can now clearly see:

On the left is the "brains" of the system, MediaTek's MT8512BAAV 2GHz dual-core Arm SoC, which interestingly also integrates Amazon's AZ1 Neural Edge processor core. Next to it is a vaguely marked Micron chip: Fortunately, by cross-referencing with Brian Dorey's teardown, his Echo Dot used an SK Hynix H9HCNNN4GUML, which I know is a 4Gb LPDDR4 SDRAM. Now let's turn our attention back to the rest of the Echo Dot's top half:

Removing four more screws, these Torx T8 ones, allows us to see the speaker and microphone and switch cluster on the top of the device:

Let’s focus on the speaker first, as the fourth-generation Echo Dot’s claimed sonic improvements are key to Amazon’s sales:

Here's a close-up of the marker in the previous photo:

Oddly enough, the speaker itself is the same size as in the third-generation Echo Dot (1.6in/40mm), but if you remove the screws:

It's lifted in the wrong place, and then the relatively large acoustic suspension cavity behind it becomes visible:

Also note that I was right, the other end of the cable connected to the speaker also connects to the contacts on the back of the speaker housing mentioned earlier. Last but not least, let's take a look at the inside of the upper housing (the ribbon cable is already glued to the side of the speaker housing and can be easily peeled off):

As mentioned before, my Echo Dot does not have the auxiliary LED panel mentioned in the iFixit teardown. But here is a close-up of the auxiliary PCB that is still there:

Remove the screws:

Re-use the screwdriver as a lever arm:

Disconnect this end of the ribbon cable:

We can now see the PCB in all its glory:

The notable IC on this side of the board is TI's TLV320ADC5140, a quad-channel 768kHz audio ADC (analog-to-digital converter), which is obviously fed by a quad-microphone array also visible on this side of the PCB. Flipping the PCB over, the first thing you see is a gasket:

It pops up easily:

Here's what's originally pressed against the other side of the gasket: four switches and the external sound inlets for the four microphones mentioned earlier:

That's it for this teardown. Having finished it, I admit that I forgot to listen to this 4th-gen Echo Dot before breaking it in (both in absolute terms and compared to the two 3rd-gen Echo Dots currently paired with my Echo Sub). As always, readers are welcome to share their thoughts in the comments!