ISO 2004 NB Door Speakers
Time to replace the original speakers - particularly the driver side one which only works when it feels like it! Looking for something reasonable, would even consider stock speakers, and don't want to spend a arm and a leg for them.
First of all, make sure it's the speaker that's not working. When the driver's side door speakers in my '03 randomly quit working the problem turned out to be a failing head unit, not the speaker itself. The random nature of the failure drove me crazy. Well, OK, maybe a little more crazy.
I chose Clearwater speakers for my NB: http://www.clearwateraudio.com
They cost an arm and TWO legs, but they sound wonderful and they're plug-and-play in the Miata. I enjoyed listening to them whenever I drove the car and never regretted the expense.
My favorite source for car audio components in general has always been Crutchfield: https://www.crutchfield.com
They have a pretty good selection, and they provide all the necessary adapters, connectors, instructions, etc, for a clean, hassle-free installation.
One caution: if your Miata has the Bose system your speaker selection may be limited. If you don't have the Bose you should have no problem finding speakers.
2017 RF Club, 6MT, Arctic White