Larger rear speakers possible in factory 4" driver locations?

I have searched and read about fitment of 8" speakers in the doors, but has anybody put larger drivers in the back? I have preference not to take up the already limited cargo space in non factory speaker locations. I have used four inch drivers in a few cars before, and I prefer to not use 4" drivers. I was not impressed with the sound even when using expensive ones. Likewise I have had good experiences using 6.5" and 8" drivers in the past. I figure there are two obvious methods. It should be possible to hole saw out the plastic of the rear four inch driver spots and fit slim riser mounts above the plastic panel, then use the branded grills. Secondly, you could mount six and a half inch drivers below the four inch holes if there is clearance down there. If you have done anything back there similar to this, please post up in the thread. I guess the other way to go is just install a small subwoofer under the seat. I may do that if I get swayed away from trying this stunt. I like the idea of just having four basic drivers performing well in four standard locations. I would welcome any advice before I get the hole saw out.

Just saw this, may have to copy Mavrik. Seems like a good way to go without compromising the interior space. https://www.caymanoc.com/forums/topic/2065-9872-rear-speaker/

If you don't want to drastically cut up your car, the 4's are the only thing that's going to fit. Personally I went with Focal IC100's back there in the factory spots, and they're more than adequate for what rear fill is supposed to supply. They're only $100 a pair, and the tweeters are angled, so they sorta-kinda face forward, you just have to make sure you mount them in the correct orientation. IC-100 - Focal Integration 4" 2-Way Coaxial Speakers <ul> <li style="text-align: left;">2-way 4" speakers (pair)</li> <li style="text-align: left;">Polyglass woofer with butyl rubber surround</li> <li style="text-align: left;">Processed aluminum inverted dome tweeter</li> <li style="text www.woofersetc.com

Nice, yes maybe I'll do fours combined a under seat shallow mini sub. Still looking at universal non-987 specific "risers" which would mean a 6.5" rear magnet section is all that would need to fit in the 4-ish inch sawed out hole. Have to do some tape measure measuring to see the amount of height which can be added before it hits things. The top surface of that panel does not look like there is much extra space to work with. Just put in a 7" touch screen gps carplay capable head unit to update the 2008 base car up to more of a 2018ish upper spec type setup.. still sounding terrible for now though.

Instead of an underseat mini-sub, grab a factory Bose subwoofer off of eBay, remove the Bose speaker and amp, and fit a Skar EVL-65. It's FANTASTIC for the $55 it costs!

I will look that one up on ebay. This or one of the 8's combined with the 4" rears should sound similar to larger coaxes. Not trying to rattle my neighbors windows, just want it to sound as good as a like a factory 2018 Corolla stereo. Which it doesn't now. This would probably fill in the bottom plenty for me. Does that mean I got to get new floor mats if I do this..

The Bose floormats are indeed different from the regular floormats. I just got some Weathertech mats, and as you can see, trimmed them a bit with some scissors. Plus the Weathertechs do a great job protecting your carpet from nasty shoes!

The plastic strut tower covers (and adjacent plastic trims) that support the factory 4" speakers are not what I would consider sturdily mounted enough to consider mounting a 6.5" inch speaker. The much larger driver will be moving a fair bit more air both in front and behind the cone which I think would create a lot of rattling with the plastic trim panels, the small and very few screws that attach the panels to the body don't seem to be conducive to supporting heavy speakers for any real duration. If you were so inclined to put in a bigger speaker back there I would consider doing away with the storage bins on each side (cut them out below the top/lid surface) and constructing a speaker frame/support a 6x4 speaker off of the bodywork. Then replace the storage lid with speaker grill mesh or even a 3D printed cover that matches the factory grill pattern. Cheers, Julian

I tried messaging mavrik on OC but it seems he has left that forum. Here is his setup pic. Also for anybody who wants to the cut and splice in plan with 4x6.. there are risers out there. I have never used 4x6 speakers so I am not sure it would be worth the effort versus just using 4" speakers. Seems like a lot of work for little gain. I think the conclusion is for this thread is... if you hate 4" speakers, just use them anyway.

To me, that looks like @$$. I've been messing with car stereos since I got my driver's license in 1987. I even competed in IASCA back in the early 90's, (best finish was a 3rd in class at one small show). I've never liked oval speakers. My Silverado has 4x6's in the rear doors, so what did I do? Enlarged the holes for 5¼'s! So yeah, in our cars, just do the 4's. Or, honestly, don't do anything. Rear speakers are always optional anyway. Think about it this way: when you go to a pub or concert to listen to a band, you don't sit with your back them do you? Nope. So almost all of your sound should be coming from in front of you anyway!

Right. If you mean the 4x6 risers look like ***, yes I agree. I figure somebody motivated enough could graft the 4x6 mount into the OEM plastic storage compartments as Julian suggested. It does indeed seem possible to fit 4x6" speakers after looking at the physics of the plastic storage bins. I do not think anything larger such as 5 1/4" or 5x7" or 6x8" or larger will go in there reasonably well. I've always had good luck with just four coaxes run off a head unit in my cars in the past, and enjoyed them without subs or amps. I like the idea of a simple system like this. That is really the reason for the thread. I guess I'll cave and try a little active sub.

I found that the odd 4x10" is also a standard sized coaxial speaker that exists. The "cone area versus narrowness ratio" would be ideal for a custom graft on to the storage plastic piece. There does not seem to be an off the shelf plastic pod for this one like there is for the 4x6 however. Closest thing I found is an adapter piece. I've never used a 4x10" speaker before. I'm tapping out on this idea in any case. I will leave it to somebody else to try if they wish. BTW I have used these storage bins exactly zero times in all the years of driving this car..

4x10's were common in GM vehicles in the 80's. None of them, not even the aftermarket ones from people like Pioneer were very good, so that size really didn't last at all. But if you want to see what they look like, here's some. Amazon.com: Pioneer A-Series TS-A4103 4” x 10” 2-Way Speakers (Pair) – 120W Max, Balanced Sound + Smooth Treble, Enhanced Bass, Great Stock Replacement : Electronics

Right I suspected the fact that people were using the above adapter to switch away from that size.. That was not confidence inspiring. I have been looking at dimensions of the under seat subs and most of them are too tall to fit in a Boxster/Cayman . Really the goal here is just to get as much low end fill as a good set of 6.5" co-axials would have put out. So I have that going for me. Appreciate you sharing your method for modifying the front bose woofer. I may end up doing that if I don't find a lazier way to do things.

So to close out the topic, I ended up getting a small Kenwood under seat powered subwoofer. It is 2 3/4" in height so it should clear the bottom of the passenger seat. Nothing mirror rattling, but it should fill in that under 120hz area at least as well as the missing pair of 6.5's. Those idealistic days of being able to enjoy the elegant simplicity of quad coaxial systems will live on in memory.