mx5cartalk.com

Hmm
possible, but you would need to find 8\" subs that are free air subs (don't require a sealed or vented volume) otherwise you could quickly ruin them and they would sound crap
also there is more power required to move the larger 8\" drivers so you might find that you want an amp anyway

other than that it should be fine, just get some passive crossovers inline with the tweeters (most standalone tweeters will come with a crossover of some sort already set up at the proper frequency)
you might be lacking in mids though

I made a three way split system using Jaycar's 6\" carbon fiber woofer and 2-way 4\" drivers. The tweeter was on axis, meaning in the centre of the 4\" driver, but had it's own wiring. I made up the following crossovers from coil inductors and capacitors from Jaycar

Tweeter - 5khz highpass @12db/oct
4\" driver - 5khz lowpass @12db/oct and 500hz highpass @12db/oct (wired out of phase)
6\" driver - 500hz highpass @12db/oct

I ran these from two channels of a 4 channel amp with an 80hz highpass filter @12db/oct, the other two were bridged to drive the 12\" sub on an 80hz lowpass filter @12db/oct.

The crossovers were not hard to make, just time consuming. Part all up were about $120 from memory.

For your low frequencies or sub frequencies you really need the driver mounted to something solid. For good sound I wouldn't bother with the doors. I've got dayton 8\" splits in the door, they sound fantastic at lower volumes, however the doors rattle like crazy when you turn it up and don't sound to nice. The drivers are far better suited to parcel shelves. Plus the crossovers came with the speakers so they're properly matched, you also have a jumper on the crossover to attenuate the HF driver too which is handy. If you go DIY make sure you look into the crossovers and match them to speakers correctly, make sure the impedance, power rating and roll off frequencies match your drivers and your listening preferences. Good luck.

I'm happy with the Pioneer 8\" 3 ways (with a cross over to use a tweeter in the stock location).

I use to have 4 of these in the car but even 2 is quite adequate.

:: PIONEER TS-E2090
20 cm 3-way speakers 250 W (MAX) ::
SPECIFICATIONS
*Max. power output 250 W
*Nominal input power 90 W
*Woofer size (ø) 20 cm
*Woofer diaphragm material Metal coated IMPP cone
*Midrange size (ø) 57 mm
*Midrange diaphragm material PPTA cone
*Tweeter size (ø) 12 mm
*Damper Large diameter Conex damper
*Top / Bottom mount
*Efficiency (1W/1m) 91 dB
*Frequency response 25-32,000 Hz

I had these installed in my '85 Alfa Sprint. The holes in the door metal were covered with 6mm sheets of masonite and sealed with no-more-gaps, and then the whole door was covered with sound deadener. The driver was then mounted to a 12mm MFD frame and secured to the door. Made for a very sturdy and non-resonating enclosure.

m0b1liz3 wrote:I was thinking that the mx5 doors can handle an 8" speaker (mine is an NB8).

So instead of getting the 6.5 jaycar split, why not get 2 8" subs, a crossover and a decent tweeter and build your own setup from scratch?

Because it will sound horrible.

Is there any reason why you can't do this?

Yes.

1) Larger drivers dont handle midrange frequencies as well as small drivers as a general rule

2) Subwoofers don't handle midrangepretty much at all, because they aren't designed for it.

3) The added force of a gutsy 8" sub will cause tons of vibrations in your doors

4) GOOD subs are designed tob e run in a sealed enclosure, so they won't work how they are supposed to when mounted in a car door.

Are the crossovers set to a certain frequency?

Could you use a crossover meant for 6" subs with 8" subs?

No, and no. Crossovers that are shipped with certain drivers are designed specifcally for those drivers. Different drivers have different response, distortion and impedance characteristics so this makes it unsuitable to use one general crossover on another complete different speaker. Changes in impedance can actually alter the crossover points and knock them out of wack quite significantly. I such a system, active would be the only serious option.

From what I remember about speakers this should be possible. I want to avoid buying an amp and taking up trunk space with a sub...

/quote]

Buy a small, decent small enclosure sub and mount it a custom enclosure in the rear shelf or passenger footwell.

Failing that, ditch the sub and get yourself a set of Rainboe CS Power midbass drivers. At 7" diameter and 96mm depth, they are a big-ass driver that plahs hella low and still has a better midrange character then most 8" alternatives.

m0b1liz3 wrote:Hmm, are there 8" speakers that are not 2 or 3 ways and not subs? (ie. designed to be mids + lows like a 6.5" split would be used???)

Yes, Peerless HDS series - if you don't mind doing much off the work yourself.