I’ve just ordered 2 MEMS Adafruit clone mics on AliExpress to test a stereo mic input and Raspberry 3.5 jack output to put voice-engine/ec and pulseaudio to the test.
I also like the idea of not being stuck with specific expensive hardware so I can easily fix faulty parts if needed 
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I’ll report back if I can get something up and running once the package arrives.
Yeah if its any help I found butchering some 12" Pi jumper leads worked well with stereo you just need 5 wires if you loop out gnd one side and vcc the other on the L/R select.
Managed to lightly solder a loop and force it into the back of the corresponding female connector.
I actually quite like because unlike hats it then becomes quite easy to place and position your mics in a enclsoure as they are just a tiny board on the end of a wiring loom.
This sort of thing, you end up using more than 5 but the connection to the pi is just 5.
Great minds think alike
This also leaves GPIOs free for a LED ring or a display to get fancy. 
Exactly another reason I don’t like some cards even if I2c can be handy, far better to have easy access to all the gpio not used.
The usb and powered analogue mic modules works really well also even the electret microphone are sensitive and you can adjust gain via gpio with gnd/vcc/float to a single pin.
Again completely leaves the GPIO apart from vcc/gnd pins used.
AGC seems to be a bad idea with EC as it seems to confuse the algorythm, not really sure about the math behind it.
Its not because its cheaper as for me it has many advantages and now see it as a prefered hardware choice with the Pi.
The ultra-cheap I2s far field could of been better and was far less sensitive than the active analogue going to a usb soundcard.
I meant to do a routine using gpio to select the gain on the analogue but never bothered as had the gain slider practically at zero.
If you can pickup one of those edimax usb soundcards in France I suggest you do as cheap stereo mic in and worth the test with analogue modules also.
I am always confused with the mems in terms of orientation and don’t think they are all the same but many seem to want to be at 90’ of the orientation you would have with a facing electret,
To clarify a little here.
The general options you’re recommending are;
A comodity USB sound card, e.g. Enermax AP001E DreamBass with I assume some off the shelf stero-microphone plugged into the stero jack?
A card that attaches to the pi via the gpio headers, (for the respeaker cards specifically, a respeaker 2 mic array hat, or a 6 mic array hat seem to be the ones with an output jack or speaker out.)
You say driver support is shoddy, how about for similar products? If I no longer care about hardware AEC, any idea how the Matrix Voice stacks up?
Daisy chain a few i2s microphone breakout boards, then split off the audio channel from the hdmi. Could you clarify the advantages / trade-offs with the microphones you mention? Active analog vs… I can see mems comes in both forms, so passive microphones? I’m not clear on the distrinction of these components here.
I’m not personally fused about the GPIO headers being consumed by the sound card hat. If I want expansion, I’ll do something shoddy like ram an arduino nano in there. As a lot of these boards still free up i2c, so I could communicate easily enough.
Any comodity USB sound card but rather than some off the shelf passive mic use active analogue modules as the Pi has the power sources.
Enermax mentioned as its stereo ADC but mono is just as valid as is also how many mic modules you use on a input.
Most soundcards get a bad reputation not because of the mic input but because the passive mic used is relatively insensitive.
You can get relatively sensitive active mic modules , some are much better than others but all are not much more than a few $ and really lend themselves to those who are going to DiY an enclosure.
The respeaker card drivers (not usb versions) lock you down to a specific kernel version and why its shoddy is actually there would seem to be no real reason apart from they have chosen to do so.
The simplesoc drivers they use are very similar to the free drivers adafruit use and its bit of a mystery to me why they are so problematic with common linux software like pulseaudio.
There is also a slight bit of snakeoil with all the far field microphones where command voice has to be the predominant volume.
The work great in distrubtuted noisy environments where the command voice is predominant or from a distance in silence.
Across what can be very common noise sources such as TV or HiFi where the command voice becomes less predominant far field recognition reduces drastically.
They do work but tend to be high value comodity product that don’t work as well in common situations as many presume.
Prob the 2mic Respeaker is the best as its cheap and if the drivers bug you it was cheap.
USB wise they tend to completly throw out of whack where I would see a completed voiceAI land price wise.
Matrixvoice never tried as think for price its a crazy solution.
Cheapest route is the Pi has an I2S interface and x2 I2S mems mics can be sourced for a couple of $ download the adafruit drivers and there you go.
Analogue use on a soundcard, I2S use if you don’t have a sound card. There is another I2S interface on the PI but I think its purely a current driver problem that they conflict with things like 4x I2S mics or 2x and a DAC.
I don’t know the full in and outs of I2S spec but you can not ‘daisy’ chanin I2S mics like you can parallel analogue.
On the Pi it send left/right in a low bytes / high bytes so as well as the interface clk it also has a channel clock where x2 I2S mics will multiplex in the low/high bytes of the I2S word.
With a single mic one is just missing.
Passive mics just send a very low level signal to a soundcard that is then amplified and often the gain and level on the sound card doesn’t give great gain and the signal is very susceptible to noise (actually the noise is just amplified geatly as the signal is)
Active mic is just a little gain circuit at the mic source where the oppisite is true, less likely to pick up noise as the signal is much bigger and will need much less amplification on the soundcard.
I said above some are better than others but its more a matter of getting a reasonable match in signal level and soundcard amplification.
So here is a recap and because the high end offerings are not all that spectacular in terms of price hike some see the lower cost offerings as acceptable and even preferable.
Prob easiest is any USB soundcard with and active mic as the passive sensitivity can be lack lustre and low.
Anything other than mono on USB audion seems to be extremely rare apart from the edimax that does give the possibility of 2 channels and any number of summed mics on a channel if you wish.
If your not bothered about HiFi quality but just want resonable voice output then the 3.5mm is acceptable and all you need is 2x I2S mics and it creates a very cheap and effective system.
If you then think that 3.5mm audio wise is a bit damn awfull you can still have an upgrade to a hdmi2hdmi+audio without making your I2S mics a waste of time and money.
This is just opinion but self contained singular consumer array microphones are probably a misnomer as essentially the where the consumer encapulation of wide array conference microphone systems into a single consumer unit via some heavy DSP lifting that many still struggle to do well with what is available.
Due to the speed of sound its pretty obvious the distance it takes between mics on a small consumer array units a couple of inches in diameter is much different to the distance a wide array conference room as it quickly changes from sub millisec processing time to a few millisecs.
Then you get predominant noise interference where a wide array has a huge advantage as 1 mic is likely to be nearer to noise and another is nearer to command voice and cancelation and detection is hugely simplified by positioning.
We have a current fad of trying to shoehorn audio capture in singular consumer devices where it can even be more costly than several wide array capture points and in many ways it doesn’t make any sense and its likely we will see more satellite systems become the norm as they are better by pure and simple physics of sound, distance and positioning.
Respeaker 2 mic.
Is a great little piece of hardware all-in-one button, mics, i2c, audio out and a couple of leds.
Brilliant piece of hardware such a shame about the drivers as without doubt if they sorted them its a killer $10 HaT.
It allows you to stick it on a Pi and go. Only problem after that for many is how to get it into an enclosure effectively. Brilliant if your going to just stick on a Pi but from a point of an enclosure you left scratching your head of why they created it so.
Some of us like the more DiY options as even if it does take a soldering iron and a bit of building its actually far more felixible and dependending on skill levels can give some really polished end product.
Many when first viewing see cards and high end modules as far superior but get to the end of a project or 2 this can often change.
Same with EC many don’t think its needed then after completeion some media playing activity comes to the fore and getting the thing to stop apart from walking up to the mic and screaming “Stop” does little.
I have a 2 Mic and 4 mic respeaker on my desk gathering dust and yeah they where great but that is all they are likely to do now (gather dust) they are a great all in one starter but very inflexible in terms of a finnished enclosure unless that is all you want as apart from the driver the 2 mic is great.
@rolyan_trauts I think they sorted out the kernel issue for the Respeaker 2 Mics Hat (the fix has been pushed into the Raspbian kernel a few months ago). When I installed the drivers, it skipped the specific kernel headers download.
Hopefully as pinning to an old kernel version was far from good.
I may brush off mine and give it a try, might not though.
Haven’t got a working AI at the moment don’t like the KWS options and a few other things with 2.5.
I do have x2 enclosures with snapcast 50watt amps and 8cm speaker running over wifi.
I say running don’t really use them, but they may stay assembled for a while.
When we get an alternative KWS prob will become a voice with x1 being a Pi4 and the sever with my fave of the Pi3A+ as a satellite mic in a stereo pair and part of my wide array microphone.
Not done much but check the forums for whats new and to reply on the likes of the above.
@andywm PS my stereo is a bit lobsided as was more of a test than anything.
One side has a
The other.
Did not pay that much for the tectonic speaker think it was under £20 but link just shows model (might of been £25 can not remember now).
I was just doing some tests on quality difference and actually the cheap visatron and cheaper amp seems very little difference to the more expensive ones.
There are quite a few Class D 50watt amps out there all pretty good even the couple of $ cheap china ones produce pretty much the same audio quality as its the same chip.
The ratings are all FuBar as often rated as 100watt but that is with 10% THD into 2 ohm and good luck finding a 2 ohm speaker and sod running with 10% THD.
If you run off 24VDC into 4 ohm its a good match to the approx 30watt RMS speakers that are avail and the TPA3116 amps are prob the best choice and theres a lot of versions avail.
I like the above 2 as they have a standby input as there is a slight hiss with no media from them that you can enable standby from gpio to stop that.
It was a toss up with the Tectonic or a dayton audio but wanted to give a BMR a go. Prob now for keep with the cheaper speakers and TPA3116 as better amps there was quite a jump up in cost and better class produce far more heat, heatsink far more space.
Everything is a compromise but TPA3116 and those reasonabilly cheap Vistron cones are actually really effective for what they do.
Memory came back as RS do them far cheaper than anyone else and was under £20.
Cheers for the infomation.
I’m just going to get the ball rolling and order some stuff.
I have a power budget of 60W, as I want to run the thing off one of those USB C fast chargers. I ordered a TPA3116D2 amp board. For now everything will be 5V, but I want to get a USB C power distribution board, like a ZY12PDN, to give me a higher voltage rail for the amp to bring the current down a bit.
Going to stick with a single speaker for testing (and I don’t have budget for another 30W speaker), the Dayton Audio RS75-4 3 I mentioned in my original post. I may revise this if mono sound sounds awful…
Mic wise, I’ve gone for the ReSpeaker 2 Mic board for initial testing, just to give me something to write an initial configuration against. But I’ve also ordered some mems mics (still passive, will look into analogue active mics), and a Enermax AP001E DreamBass to evaluate. I want to also try HDMI audio if that proves to be an annoyance, but I’d like to find a digital to analogue converter for the signal that isn’t a giant box. Surely there’s a nicer solution for that.
You will never get the wattage with 5v. 24V gives a max of just over 40watt, 12 obviously is half that.
I use a 24Vdc and just a simple Buck regulator for the Pi.
Again cheap as chips and also its 5.1v if via a type-C.
I already had some CCTV 5.5mm barrel terminals and some type-c adapters so a little unorthodox but works.
I just set the buck to 5v with no load plugged it it and upped the volts a touch to 5.1.
But your on the right track its prob a choice of Usb or hdmi and USB is prob better apart from the dreambass for some might not be so dreamy.
Prob something in the region of 100nf DC blocking cap (in series) would attenuate the bass if it really annoys.
Mono sound sounds great as even with x2 speakers if there isn’t physical spacing it will be mono with x2 speakers mixing both channels as that is how our ears work.
I just have x2 units one a master and another slave running snapcast in a stereo pair, but these 2 speaker jobs in a tiny single enclosure are just a misnomer.
Your single speaker will be fine and those dayton audio are supposed to be great.
If you don’t have 24V you will get no where near 60W.
As a tester cause they are so cheap try one of these on 5v and then give it 24v.
60W is my budget, it’s the max power the fast charger can deliver. The speaker is only 30W.
Yeah, I do have a handful of LM2596 based bucks actually. Let’s see then;
Speaker Impedance is 4 Ohms
We need to provide 30W for max volume.
Power is P = I*V, and Ohm’s law is V = IR.
So our target voltage is P = V^2/R ==> V = sqrt(PxR)
V = sqrt(30x4) ==> 10.96 V
and current is I = sqrt(P/R) ==> 2.74 A max current draw.
So I’m currently providing about half the power I need, which is fine for testing I think…
Got the amp today, it’s bloody loud enough already.
I don’t currently have any microphones, so I can’t test any further. But I might at least dd an OS onto an SD card for the pi. Speaking of which, when did the Pi switch to these micro connectors for everything. I don’t own a single device I can plug into micro-hdmi, nor do I have micro usb keyboards. SSH will be fine, but they’ve definitely complicated the out-of-box experience with these niche connectors.
Yep a pain in the A changing the format. The Pi4 really is a set top box chip and it had another HDMI so they used it, but changing the connectors has had same effect on me.
To be honest my fave for $ is the Pi3A+ and at least that still keeps original connectors.
Pi4-2gb is great value also.
If you got some I2s mics I have found the cheap seem to be as good as the GY-SPH0645 ones.
If you want Pi3 perf with audio out and x4 i2s mics with dsp VAD then that Rockpi-S is a killer price @ $13.99.
There was a great post on editing the DTS.
Just remember she has a custom rom so if using the official check the dtb name.
I might have a go with the usb audio gadget as with the ec software even if not a kws satellite these will prob make great wifi speaker/mics if I struggle to get usb audio gadget up and running.
Need to add a softvol and up the volume a bit and also do the same with the dtb and enable the VAD.
We have had a lot of conv always surrounding the Pi but for 4mics with stereo out the inbuilt codec and i2s is by far the cheapest option.
Its actually 8mic as it has 4x Din for I2S L/R pairs but the DSP VAD only works with 4 max.
I lost interest for a bit but think I am going to spend some time with this and do a write up as Quad-core Cortex-A35 with all the audio just connect to amp and I2s mics.
It does have 8x ADC but given up trying to work out the wiring and setup, hence the I2S.
@rolyan_trauts I’m looking forward to your write up on how to get the RockPi S to work with both audio MEMS mics input and amp audio output 
Not looking good as looking like its firing out on the i2s-O0 which sort of negates the whole point if you have to fit a DAC.
I am just going to go back to analogues and work it out myself as if the voltage kills the adc, it kills it as given up waiting for radxa to publish something.
Well dunno why I waited for so long as just thought what the hell connected 3.3v to vcc of the module and gnd with a parallel gnd running back to the mic-n pin with out to the mic-p pin.
Analogue mems seem a bit quiet but fine and the electret with the Max9814 mighty sensitive as usual.
I just connected without dc blocking caps and yeah both have a dc buzz, but much less than my lazy approach expected as thought without the caps it would be horrendous but ok to test.
Really wish there was a mems avail on that Max9814 as they are much smaller and less prone to vibration but hey ho.
Got some parts ordered so will do a write up on the RockPiS when I put this together with software.
Have you tested the mics sensitivity in far field conditions (a few meters away)? Is the MEMS performing better than the electret in this situation?
Electret due to the MAX9814 mic amp is far more sensitive. With the 50db gain and 13.5 on the codec seems a sweet spot.
The 60db gain on the Max9814 (gain pin floating) I think is more optimism than anything as induces hum.
Yeah it’s really sensitive and far field in my flat would need a tardis effect 
so can not give you definitive.
I live by the sea and did notice in the recording I could hear a seagull outside and also a car that went past.
I have a feeling they will be really good for far field but quite a pain to isolate from vibration and noise and need really good isolation.
The sensitivity and cost of the electrets has perked by interest and the Rock-Pi-S has onboard mic bias.
And due to the sensitivity its perked my interest especially on cost as Micbias goes to Electret+ and Gnd to Eletret- and then on the RockPiS those Electret +/- is just fed through a 100nF DC blocking cap on the MicP & MicN on the GPIO.
I2S is the same as all the mems are actually quite good far field but to my surprise they don’t seem to be as sensitive as plain old electrets.
Yes they have better isolation and are conveniently tiny and don’t lose charge over time but if that way is OK then the rockpis and electrets is just so cost effective.
It does have a rake of interfaces and its biggest problem is the 2x 26 pin headers isn’t enough but PDM is there also.
There $3.50 each but wow -26dB ±3dB @ 94dB SPL kicks the hell out of the analogue and I2S so far tested.
Should of got them from adafruit but found them first on aliexpress
Still scratching my head how to write to the onboard registers say echo 0x60 0x40ff0168 > /sys/kernel/debug/vad/reg as baseaddress and offset is making zero sense to me.
Pretty sure you can switch the onboard dac to the I2S_O but external dacs and mics both work on 8 channels.
Address: Operational Base + offset to what I am reading just isn’t making sense or working.
Seems a typical technical translation where things like “The difference between a duck is that one of its legs is both the same”!
The PDMs will work with internal dac as its RX only unlike I2S but the down side is they are not cheap or at least not cheap compared to others, especially just plain old electrets driven by the board micbias.
Guess I should do an update on the RockPiS and its been a fair old pain in the proverbial.
Sadly in its present configuration my suggestion is a $4 I2S Dac & the $2 I2S mics only.
I say sadly because analogue wise there is a noise source somewhere that using board gain just amplifies the inherent noise.
The 8 channel ADC is great, the gain is great but where the noise comes from has annoyed me greatly.
Cheap electrets via a resistor and a cap would work great but you have to use much gain so welcome to noise.
The MAX9814 due to providing gain offboard and then providing a large signal you can get away with the board noise as with no board gain its minimal, but try one with the caveat you may need to go I2S.
The 5 pin Adafruit MAX9814 really are amazing little boards due to tristate AGC & Gain pins.
If you get any mono really cheap USB sound card you can parallel mics and the AGC will balance them dynamically which is great when your stuck with a mono input.
Whilst raving about an old electret board the AGC timing cap 100nf tC that adafruit for me is too low for Voice. Its Ok if you leave it float with the longest Attack/Release and prob would of been better with a 680nf where gnd would hold it at a mid point and you have a selection of usable AGC but hey (soldering iron needed )
PDM mics for some reason came in real low in volume I mean really low and being digital slightly perplexed to why but think something is going wrong in the PCM conversion set up by the board DTB.
So bit of a bummer but unlike the Pi it can run I2S Dac & Mics concurrently ( 8 of them, 4 on DSP VAD).