There are factory positions for speakers in the trunk (vertical). I just replaced one of my speakers in my GS convertible last week.
I have done it but it seems to be a waste of time. Between the road noise wind noise and the joyous sounds coming from the engine compartment I can't hear any music anyway
On my LeSabre, from the factory the back speakers are mounted to the back of the back seats facing the trunk (weird I know). Works OK though they do sound better with the top up. Not familiar with what people do with Skylarks, but it's an idea.
You will be limited on the size of the 6x9 speaker you can use, they have to be thin to fit. You don't have much room to stuff them in from the trunk and I don't think (maybe you do) have access to the area if you remove the back seat. Maybe you can mount them backwards from inside the trunk so they face the back seat ? Mine had a single speaker in the back from the factory to give the Stereo effect for the factory 8 track player..... 1968 technology...
I've been thinking the same thing. The Wildcat has 1 speaker mounted behind the grill in the center of the seat back. With no closed in trunk there is little to no base response. Due to the canvas "bag" the top folds into there really is not much room to make any sort of box.
I refused to cut any panels in my verts so bought a set similar to this and mounted them under the front seat with two sided tape. They sounded surprisingly better than expected with the top down at high speed. https://www.truckid.com/pioneer/5-1...-2AQ-XROTKW1pGYUiTLS6I35wyBTG-IYaAvX7EALw_wcB
I just use my phone and a big bluetooth portable speaker on my back seat for longer trips. Usually I would rather hear just my engines music.
My radio has been on less that one hour total over the 21 years I have owned my GS. I fixed the back speaker just because it bothered me that it did not work.
This is what I did to help out: http://fixjet.ca/speaker.html It does make a big difference, the rear factory 6x9 locations with the top down is pretty much useless. I just can't bring myself to cut any panels and putting speaker boxes behind the front seat will work but then when friends want a ride it all goes out the window. The bluetooth portable speaker is a great idea!
I bought thin mount marine speakers to put in the back. They are decent enough to have some music but they aren't amazing by any stretch of the imagination. This winter I will build custom panels that will allow for higher quality speakers, but from what I've seen I'll have to modify some of the pieces behind it.
I too am not willing to cut holes, but I did replace the kick panels with ones designed to hold a a speaker (saved the original panels). I then I put a sub box and four boxed 6x9's in the trunk. Not amazing sound... but descent sound. Not too audible above my Flowmaster 40's at highway speeds though. If I had to do it again, I probably wouldn't. Going with a large Bluetooth speaker as already mentioned is the better option. -MIG
Based on my convertible experience, I would suggest that putting extra speakers in the rear is a waste of time. I can hear mine at a traffic light but on the highway..., I only hear the front speakers. If I had an A-Body, I would buy the replacement kick panel pieces that are molded with speaker enclosures. These are in the right spot and offer enough size to sound ok. You can easily swap back in the original panels if you ever change your mind...no cutting... I installed a used subwoofer in the trunk to add some bass - that works. Without a sealed cabin, there's only so much you can do to create decent sound, so no sense in dropping a lot of coin to literally chase the wind.
...waste of time/effort unless goal is to let other verts know at lights etc. what you listen to, everyone else has windows up and A/C on...
you can get mini amps and under seat subs etc... enough power and you really dont need rear speakers. just need enough power to hear it.