Outer Limits 4x4 Board

What would happen if I put 4 ohm independence speakers in instead of original 8ohm ones.

Well, most car speakers are normally 4 ohm.

It depends on what head unit you've got. Amplifiers are usually rated at certain power outputs, they usually deliver more power into low ohm loads, roughly double for a drop from 8 to 4 ohm given the voltage swing is the same.

However when the impedance is lower stability is a problem. More power is from an increase in current, so the amplifiers outputs need to be able to handle this higher current and the power supply needs to deliver it.

If it's an aftermarket head unit it should be fine, they're made for 4 ohm speakers. It's a manufacturer's one... it might not be 4 ohm stable.

Can you contact the manufacturer or get a manual for it ?

That would be the easiest way. You could try it as well, most likely should be completely fine.

If the amplifier in your head unit is struggling it will get hot and if it get's really bad thermal protection should kick in or a fuse blows. Also just listen for distortion and clipping.

Thanks for that, the old 8 ohm speakers are out of an Excavator, checked the voltage of the unit (radio only type ) and is 12v not 24v.
Old speakers are 20w max audio and 8w normal audible, the outer cushion has gone hard in one area and the speakers crackles that bad you just can't listen to it.

there shoudnt be anything wrong with putting 8ohm speakers on a 4 ohm head unit. Other way around however and the amplifier wont like it. Generally speaking, if you have car stereo parts, they will be 4 ohm, home stereo parts are likely 8ohm (but vary).

Seriously, for a system pushing 16w nominal, you arent going to lose much by giving it a crack.

Sounds like the surround is stuffed. They tend to do that with age. Not worth repairing for anything but the high end stuff.

4 ohm should be fine, just give it a go is my opinion. If theres any dramas swap them out for some 8 ohm. Can get some sizes in 8 ohm that are full range or coax.

You shouldn't have any problems with the 4 Ohm speakers. If anything they might be a bit louder

Installed and all is ok, the difference is I think it may alter the frequency range or tone or something like that as now the bass, (if a 4" speaker can call it that) is not as deep and the trebble is a bit higher. Not all that bad as before the tone of it was a bit to low, know it is able to be heard above the rockbreaker.