That’s incorrect. If the box is flexy, like the one I made using the plastic glovebox, it will sound terrible. There’s no ambiguity whatsoever. It’s no longer subjective when the install is compared with a sub enclosure that’s already proven to work well.
“Localized and flat” as a location problem
Location is not the reason for that problem. This is a problem with a plastic enclosure that flexes too much. I made a box out of the plastic glovebox like this guy:
It sounds like you’re conflating “glovebox location” with “glovebox enclosure”. I guess its kind of hard to describe without pics. Check out the thread by TURBOROADSTER above. I tried making a subwoofer box out of the glovebox just like he did.
Anyways, it sounded like a great idea so I tried it and it just does not work. The sound changed dramatically after I took out the glovebox enclosure and installed the sub back in using the body as the enclosure. Right now, the only thing wrong is that it probably has the wrong volume.
In your case, you’re comparison method is faulty which leads to a faulty conclusion. You should be listening at both locations using the same enclosure you made for the glovebox location. Unless you do that, you can’t say this is a location problem.
If the one in the corner sounds much better compared to the one in the glovebox location, then the “problem” is either the sub or the box (volume, leak, polarity, etc)
Different drivers will sound different. My Infinity Perfect 10 VQ on the left sounds a lot different than than the Infinity Perfect 10.1 on the right. The 10.1 is much more efficient (i.e. louder) but produces slightly less bass than the VQ version. The VQ version requires much more power to produce the same SPL.
This is my tested locations and types of drivers:
1) Back trunk - 1.0 ported box , 1.4 ported box
2) Front seat - 1.0 ported box
3) Right glovebox area - Perfect 10.1 using the body as enclosure
4) Left glovebox area - Perfect 10 VQ using the body as enclosure
**Boxes were all Perfect 10.1s
I know that location is the least likely sound problem. There is no difference between under strut and trunk area. With the front seat removed, I had the 1.0 box in there and it does sound slightly different, but not a big deal. Location is not that big of deal because a properly functioning sub’s low-frequency sound waves are non-directional; unlike tweeters, where high frequencies are directional.
Although I haven’t tested the corner area, I suspect it would sound the same as the trunk and under strut which is only a couple feet difference.
The “corner loading” claim sounds like a marketing thing that originated from installers. Installers will sell the easiest build locations because the quicker they can build it, the more money they can make. That corner location is “easy”. You just remove a few pieces. The glovebox area is much more difficult. The seat and plastics need to be removed, the holes plugged up, the volume correct for each driver. Because of the different vol. requirements for different drivers, you’d have to make sure the volume is correct which is almost impossible to do without taking time to test it. Testing the glovebox area using the “body-as-enclosure method” is too time consuming. And don’t forget the contortions to the body to build within the glovebox space. You can’t money if you get injured. Smart installers would rather sell the “corner loading.” and spend more time building a good-looking install. If the install looks professional, the sound (even if faulty) will sell itself to the client.
Side note: Same with kick panel pods. Note how you don't have to run wires through the molex on the door. It saves time and you can sell the client some pods.
I forgot to mention this in my past posts. I took out all the plastic and stuck some thin closed cell insulation on the panels before I installed them back. I used the kind with foil on top. I peeled off the foil because when that falls off, it will give off these “tinkling” noises. This took some time but it was worth it. I do not have any plastic rattles. Dynamat will do nothing to reduce plastic rattles. Dynamat is only used for reducing resonance and you don’t need much to do that.
Left side: Infinity Perfect VQ, with 460 rms watt amp, ported out the back using the body as the enclosure. No rattles other than the rear window distorting. The sound is properly non-directional.