Sounds like caps they will filter out the bass so the speakers will play only mids and highs if they are caps they r connected on the + pos terminal of the speaker. Wire from deck or amp in and out to the speaker.
Hope this helps.
yeah and if you have an amp and subs, or dont it really improves the clearness of the sound. Unless you have an electronic x over or an amp with it built in. An electronic x-over is better than a passive x-over which would be caps and coils.