This evening I had the opportunity to compare the GK Neo 112 II and the Hartke Hydrive 112 side by side using a GK MB500 head and a Fender MIA Precision 5 string bass. Sorry if this post is too long. MY results:
Hartke: smaller cabinet size, EXCELLENT bass response, smooth sounding horn and a little less volume than the GK. Could not get the 12" speaker to fart out with a lot of bass dialed in at the instrument and the amp pushing a lot of watts. There wasn't any annoying cabinet vibrations. Turning the horn off, the speaker had an exceptional full range sound to it. The 4/8 ohm selector is a major plus!
Got to hand it to you Larry, you could really just leave the horn out of the cabinet and it would sound good. Your 12" speaker is one of the best sounding 12"s for bass I have ever heard. ( would be nice if it was a 400 watt speaker

)With the horn turned off, add a little bit of treble on the amp and it would make any slapper happy.
The chrome corners have to go! I would much rather prefer plastic locking corners (would help in vertically stacking two cabinets). If I end up getting two of the Hydrives that's the first thing I would do. The single??? handle I would rather have on the horn side of the cabinet. The handle would be better black instead of chrome. That's just my preference. The rear jack plate needs to be recessed further. If it is laid on it's back the switches for the horn and 4/8 ohm selector could be damaged.
GK: A little more volume than the Hartke but you better not play the B string if the amp is turned 1/2 of the way up and you have some bass turned up on the amp and guitar. Hitting the B string with a hard attack made a popping sound through the 12" speaker. This was not a noise from the cabinet, it was from the 12" speaker. Sounded like cardboard being hit with a drumstick. Not as much bass response as the Hartke.
The horn is loud. It can be adjusted with a rotary control. When the horn is turned off, the 12" speaker is well to me....dull sounding.
I removed the 12" speaker out of the GK cabinet to look inside. Two of the wood screws that held the speaker in were only partially through the wood. During assembly the speaker was not centered properly in the opening so the screws barely made any contact with wood. There wasn't any annoying cabinet vibrations.
NO DAMPING material!! Well I'm not a cabinet expert, maybe it doesn't need any? The Hartke had damping material I could see through the bass port. The GK electronic crossover assembly had two replaceable light bulbs mounted on the circuit board. Wonder why it's not mentioned in the owner's manual?
I have two of the GK Neo 112 II I bought new without hearing them first....my mistake. Using them together running the GK MB500 at half volume, they will not handle the B string on my passive Precision when digging in. The GK cabinets seem to get favorable reviews that's why I got them without listening to them first. Won't ever make that mistake again. I'm not impressed with them. I'm searching for alternatives to the GKs.