extract from my post on mx5klubpolska forum https://www.mx5klubpolska.pl/forum/viewtopic.php?f=28&t=32065&hilit=nc+audio)

questions about mk3 Mx-5 audio are quite common. Over years I tested lots of my idea about it - heare you can find conclusions. You dont have to make my mistakes

its about stock non-Bose system with 6 speakers

in stock form sounds really bad. CD a little better, FM nightmare, no other sources


SOUND
main issues with sound in mk3 Miata are
– mid-woofers (oval wideband speakers with 2 membranes). I found these speakers are deteriorated and you can replace them immediately. One thing you can reuse from them are connectors to connect new speakers without cutting harness and plastic water guards

I recommend using 165mm woofers on MDF adapters. You can use Speakers up to around 70 mm depth (from mount to window slider is 66mm, adapters are around 6mm thick)

mid-woofer replacement is a mustWithout this sound will be still very bad, believe me


– lack of sound deadeningDesing is not that bad but additional sound deadening helps a lot. I recommend doing this. Thread about this (in polish ;-) )
viewtopic.php?f=28&t=34763

- if tweeters are ok there is no need for replacement. This will not help much without relocating to A-pillars

- later model NC2 headunit sounds slightly better than early NC1 ones. Good aftermarket units will be even better but dont expect anything without replacing woofers and preparing doors. Warning! later model headunig has slightly different shape, can be installed in NC1 but does not look very nice.


FUCTIONALITY
At first you have to take decision of keeping stock headunit or replacing

1. to replae headunit you need something like this

and 1DIN or 2DIN aftermarket headunit, choose you like


2. keeping stock headunit but having desire to add more sources like AUX, BT, USB there are few options. I start with best bang for a buck ones


this BT module (aliexpress). There are versions with microphone or without, around 15 euro. For me this is best solution for stock radio. Cheap but good enough, if you want more replace whole headunit

- decent sound quality, slightly worse than WEFA, better than FM transmitters and AUX cables. Supports only SBC codec so remember to set your source volume level slightly below maximum
- acceptable useability
- installation a little more complicated than WEFA. You have to connect GND and +12V for instance for ANTENNA/REMOTE wire. In that case module starts only if headunit is on It is very convenient
- module is small, fits easily behing headunit
- works with early and later model headunits


CD changer emulator for instance WEFA. There are few different units, with different inputs and with or without microphone. I used top model WEFA-606

around 80 euro
- good sound quality, much better than FM transmitters and Aux cables, but only if your BT device volume level is not too high! Set 2-3 clicks below maximum then it sounds similar to CD
- steering wheel control works, also with phone calls
– flaw I found is automatic connecting to phone regardless headunit is on or off. In case is off and someone calls us you will not hear him. This was for me unacceptable so I sold WEFA


- FM transmitter

Very simple and relatively inexpensive. Connect to lighter socket, find it on FM and thats all. Tested 2 Baseus units (15 euro each) and more expensive Roidmi 3S. Last one is best but
- sound quality acceptable but not all the time. Sometimes our local station will interfere
- not very convenient to use
dont recommend


- AUX cable for MEDIA input

around 10 euro. Connected to your phone (if has jack output) or add BT module for another 10 euro.

Not very expensive, sounds better than FM transmitters but volume is low even with maximum volume from phone

dont see much sense for this when BT module described above are avaliable



headunit removal necessary to install AUX cable, changer emulator or another module

in short

• remove 2 plastic triangles from left and right side of headunit
• remove plastic steel trims below steering column
• remove bolts. The worst one is hidden from drivers (LHD) side. I recommend throwing it away after removal

when your audio starts to work decent I recommend installing Bass Shaker units Yes - it can be even better!