How’s this domestic woofer for a small hatch’s boot?

[otto88]

Its a good price, and good quality, for a

• Nominal impedance: 8 ohms
• Power nominal: 225 WRMS
• Sensitivity: 91 dB
• Qts: 0.32
• Vas: 22 litres
• Fs: 60 Hz

http://www.jaycar.com.au/productView...r&form=KEYWORD

in Unibox it models into 300 litres (my estimate of the boot's size), vented at 80 Hz, with a nice +4 dB bump up at about 80 Hz, for some thump factor

How would an 8 ohms driver work with a normal car 4 ohms amp?

[nightanole]

half the power. aka if the amp put out 200 watts at normal 4ohms, it would only put out 100 watts at 8ohms.

[otto88]

Yes, so as long as I have enough power (halved) to get to my target SPL (which is only peaks of about 106 dB) . . .

And if I ran 2 * car co-axial 6.5", 4 ohms car speakers off two amp channels; and two 8 ohms woofer off the other 2 channels . . ?

[sofaspud]

And if I ran 2 * car co-axial 6.5", 4 ohms car speakers off two amp channels; and two 8 ohms woofer off the other 2 channels . . ?

The 4 ohms and 8 ohms are nominal values; in use the impedances are going to vary with frequency. In general, using a higher nominal value as an amp load is alright. In your case, you'll likely want a means of "balancing the front & rear outputs", ie a fader. I'm not sure if you plan to do that at the head unit, amp, or the speakers.

[otto88]

Thanks SS, I follow you

I'll make sure there's a fader in the head unit

Cheers

[ppia600]

You can bridge the amp's rear two channels into one and parallel the two 8 ohms woofers across the one bridged channel to maximize the amp's output. Then run the front speakers on the amp's front channels. The amp should easily be able to handle a 4 ohm load bridged if its anything decent made within ten years or so.

[sofaspud]

The amp should easily be able to handle a 4 ohm load bridged

...which means a 2 ohm load for the amp. My own approach is to not stress the amp unless the mfr spec'd it for low-ohm loads. YMMV.

[otto88]

Thanks guys, will give it a try