https://www.sonicelectronix.com/compare/items/4007_69574/JL-Audio-12W7-3-vs-JL-Audio-12W6v3-D4
Is it worth it to spend 300$ for a sub to be 1db louder, 25/64th's of an inch (10mm larger), and more distorted? Then go with the W7, it also has 2 Hz lower frequency range than the w6, which means it can produce lower frequency notes. The impedance of 4 ohms (w6) will produce cleaner sounding audio, however the 3 ohm (w7) will be more powerful. The w7 features a 10mm (.3 in) larger cone excursion than the w6. The w6 has a dual voice coil, while the w7 has a single voice coil.
Most car amplifiers provide specified amounts of power (wattage) at common impedance ratings measured in ohms. The
MTX THUNDER1000.1 mono channel amplifier for subwoofers is rated at 350 Watts wired to 4 ohm impedance load (speaker combination), 600W RMS at 2 ohms impedance load, and 1000W RMS at a 1 ohm load. A 2 ohm, single voice coil sub has a fixed 2 ohm impedance rating, so would draw 600 watts from this amplifier. The same 2 ohm sub with a dual voice coil would offer 1 ohm and 4 ohm connections, depending on whether you wire the two voice coil terminal pairs in series or in parallel. Choosing the 1 ohm wiring method for this sub would make 1000 watts available from the same amplifier. Dual voice coils have more wiring flexibility, however single voice coils are easier to wire in series, combination or parallel (easier to wire multiple single voice coils). The RMS wattage isn't really a direct measurement of sound considering it is just what is required to power the specific size of the speaker in question, so 600 vs. 1000 watts doesn't tell you much, considering the actual potential power of the subs is way higher (1000 watts for the w6 & 2000 for the w7).
The last thing to talk about is that the RMS (root mean square) or the amount that sub can handle on a regular basis of the w6 is 600 watts, which is perfect for a 500 watt amp because it has a lower max wattage. The only thing to look out for is that even though a amp may be labeled 500 watts, it might put out even more power at different impedance levels, dual voice coil subs like the w6 will allow you to take advantage to keep the sub in the recommended RMS wattage. Some 500 watt amps can put out 650+ watts at certain ohms. The RMS of the w7 is 1000 watts, so you would want to go with a 750-1000 watt amp for the w7. (750 watt to be safe).
So in conclusion:
w7 - louder, although not by much at all (+1db), lower frequency range (-2Hz), higher max wattage potential, larger cone excursion, single voice coil, easier to wire with other subs
w6 - quieter, although not by much at all (-1db), more sound clarity because of higher impedance (+1 ohm), dual voice coil, more amp-sub ohm wiring options, highly reviewed
