I used to own a car audio shop and have herd countless systems. I also had 6 dedicated systems for my old car that went in and out depending on what brand was being demoed.... My top 3 were.... #1: JL Audio W7's in a closed box.. Overpriced loudness.... #2 Alpine R10 in a ported box. Hit harder than my 12 or 15's, best bang for the buck IMO..... #3 was a tie between 3 JL W3 (8" sub") in a closed box. Or the 2 kicker solobaric (square) subs in a closed box.
I like the W7 for quality at low level but they were also stupidly loud... And expensive
Dual Alpine R10's was my every day rig, these sound as good or better than the JL at low volume. When you turn them up they punch like nothing else accept maybe the alpine type X... Hits harder than JL in a proper box but overall slightly less loud at 100%
The W3 rig was made to demo for trucks with little space. The system sounded better than any pancake or shallow mount sub I had ever herd. Lots of clarity, not so much on the loud part.
The Kicker was always a fun one because it was just so much cheaper. They are not as clear or loud as the others but finds a happy medium. Good for someone on a budget or who really can't hear the difference.
I ran everything on an JBL Grand Touring Amp. Subs were tuned to there acoustic crossover point and checked for phase alignment using SMAART.
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