opening up the space between the trunk and the cabin will have almost no effect in a miata. the thin sheet metal does pretty much nothing to block low subwoofer frequencies.

Have you tried it? I have done it both ways.

What about the three layers of insulation that covers the parcel shelf? The carpet, padding/batting layer and rubberized layer of the uphostery along with the panel absolutely mute the amount of sound coming from the trunk. The apparent volume was much louder after I cut out the parcel shelf AND upholstery, then covered the hole with a speaker grill.

In addition, I removed the fuel line cover in the trunk, opening the pathway down the left side of the trunk just as it is on the right side. No cut-out of the parcel shelf on the left side yet, though I was thinking I might add one just to make it symmetrical. The woofer is a lot closer to the passenger side opening so I doubt I'd get much benefit from opening up the other side.

The parcel shelf was already partially cut to accept the roll bar - just cutting out a bit more material along with the upholstery was not difficult and it made a big difference.

No spoiler. All I have on it is some home depot dynamat that I put on there a week ago. It never lifted the lid on it's own to begin with. It will hold it in place wherever I leave it. Function is the same with the marginal added weight of the dynacheap. I may spec out a strut with more lifting capacity if I find some free time.

Jumbo, how many watts does that tube sub consume? I have an Image Dynamics IDQ12V3 in a .8 cu ft sealed box (Soon to be a ported box, 12 more db at 42hz OH YEAH) stuffed with polyfill hooked up to a RF 700watt rms amp. Also have 120watt rms powering 6.5" Polk door speakers. I am weary of cutting or removing the parcel shelf because my Walbro 190HP fuel pump whines like my girlfriend. For me, removing the shelf would outweigh the advantages of barely increased low frequency SPL.

I really went cheap on all my components. I had a very specific philosophy in the audio build. Be like Bose. Crap quality, but using crossovers you can tune each speaker to produce the absolute best range it was capable of. The Pyle subwoofer was leftover from an old project. It's got it's own switched power supply rated for 800W. I have the gain set to about half because more than that leads to distorted sound.

The rear channel speakers are hooked into the 100W/Ch amp and the front speakers are hooked into the aftermarket head unit/amp. The gain is down on the amplifed rear channel as well - in order to match the front channel volumes. Playing with the crossovers and gains took a couple weeks but once dialed in, I rarely have to change settings.

The small space in the Miata works well with this gear, but I can tell it is on the edge of capability. Trying for more volume usually results in clipping or low frequency distortion. I'd have to upgrade the front & rear speakers to take it to the next level but probably won't since it ain't broke as it stands.

the "bose" method is ok to a point. cheap components usually have much higher levels of nonlinear distortion when used near the boundaries of their comfort zone. without the proper equipment, it's hard to know where that is. you can compensate by playing things at lower volume, but you can't eliminate it.

That trunk sub better sound ------- amazing...cause there's no reason to take up the entire trunk with one.

I have a 2000 Miata, is it worth replacing the door speakers with a component setup? Will I need an amp to power it?

I am sooooo ignorant about car audio, just want something louder and clearer so I can hear it with the top down.

Thanks!

If you have a bose head unit you will have to get a different one as they use a difference speaker impedance.
But no, a decent head unit will be more than powerful enough to drive the door speakers.

It really depends on the speakers. If they're efficient (> 93 db/2.83V@1m sensitivity), it's like getting a free volume boost. if they're inefficient (<88ish) then they will do best with some amp power behind them.

Each 3 db you go up in sensitivity is equivalent to twice as loud / double the power. so if you compare a 90 to a 93 db speaker, the 90 will require twice the power to get to the same volume level. (assuming both are the same impedance)

Now... You dont need component if you replace them, but you should get a multi-driver setup. Coaxial is fine.

This has inspired me to attempt to make a sub woofer box for an 8" sub. I don't want to have to remove woofers and amps to travel in the car since my wife and I use our Miata to travel 'round Texas and further at times.