On 23/5/18, a friend encountered an error during installation (it produces *too much* bass) - sometimes this specific Alpine mentioned simply burns easily, especially in the circuit it refers to (low frequencies).
They work perfectly with a simple Hertz amplifier in a GolfVI.
I highly recommend them for genuine Hi-Fi sound - they are more balanced than many Focal speakers, and better than the equivalent Alpine ones, but they can be played with Audison (e.g. Voce)...
Overall, it has a lot of bass for such a speaker, controlled, sweet, generally very balanced and high-quality in sound and construction.

I have had them for about a month in my Ford Mondeo. I made a hole for the tweeters and installed adapters from oval to 6.5 inches. I also installed soundproofing inside the doors. Previously, I had Pioneer coaxial 3-way oval speakers. I am using them with a Pioneer source with a very good quality screen and an Alpine PDX 4.100 4x100 watt amplifier. I don't know if the amplifier is not sufficient or if it was affected by the fact that the door position was originally for oval speakers, but the Hertz speakers do not produce as much bass compared to the Pioneer ones. They have a little more intensity and clarity and without distortion, and of course, the highs are incomparable now that the tweeters are higher and with high-quality crossovers. They also require high-quality files or CDs, otherwise, they do not show their capabilities and sound worse than the Pioneer ones. Also, the tweeters must be on-axis as much as possible, otherwise, they lose significantly. I noticed a difference with the subwoofer on and at high volume. When I need space and remove the sub, I am bothered by the complete lack of bass that I had before. Are they worth 2.5 times the money of the Pioneer ones? No. Unless, as I said, it's my amplifier's fault. But if I were to buy speakers again, I would look for oval components and not round ones.