Our customer has owned this NC Miata MX-5 for a few years and was looking to improve the sound quality in her car. It did not have the Bose option and she found the system to be lacking in bass response. On a convertible like this, it's important to get a speaker that can handle higher power as the volume needs to be cranked up when the top is down.
For these non-Bose MX-5's the door speaker size is a 6x8" which is a common size for Ford vehicles. The nice thing about this is that if you purchase an aftermarket 6x8" speaker, it will bolt in without any modification or spacers/brackets. You will still need to adapt the harness for the aftermarket speaker however.
Alpine R-Series 6x8
Our customer picked the Alpine R-Series after comparing on our soundboard with a few other speakers including the Kicker KS. The R-Series is one of the best speakers in the industry with solid performance throughout the range. The silk dome tweeters offer exceptional clarity and the high sensitivity (89dB) speaker sounds great even with a weaker factory system. The neodymium magnets are also compact making this lineup an easy fit for many vehicles.
This specific Alpine R-S68 model has 100W RMS rating meaning that it'll take just about any 4-channel amp upgrade you throw at it. Our customer wanted to keep the radio looking factory and original for now but a newer amp with high-level inputs will offer the best of both worlds.