Do my speakers need an amp?

[mawby]

If my Kenwood Z838W (http://www.incardiscount.co.uk/acatalog/info_1535.html) head unit can output 50w*4 max (30w*4 DIN), and my Kenwood KFC-W1705 (http://www.justkenwood.co.uk/speakers01/kfcw1705.asp) rear speakers can take 260w peak, and I hope to upgrade my fronts to similar sized and rated speakers, is the head unit powerful enough for the speakers or should I be looking to put an amp in there? If so, what RMS output from the amp should I be looking for to power (but not destroy!) 260w speakers?

[Matt Harwood]

Any speaker will benefit from an amplifier, but to get the most from the speaker, forget power ratings, you need to look at the enclosure first.
I notice that the speakers you've quoted are subs, or more acuratly, mid-bass drivers. - How are they mounted? Are they in the GZ type enclosures or mounted to the body?
Ideally, the easiest to get a good result is to seal the speakers in as much as possible.
Yes, and amp is definatly worthwhile. The speakers will work best if you can band-pass them. In other words, have a crossover working to stop the mid/high frequencies getting through and anothe crossover to stop them producing too low frequencies for them to handle. - You should be able to chive this with a decent amp and the System E's on your head unit. I'd guess at a high pass on the amp set to around 150hz, (this may be too boomy and may need a lower figure), and low passed at 40hz via the system e's.

Have I just over-answered the question :innocent:

[mawby]

No Matt, that's great help. The speakers are mounted where the normal rear speakers are, without the rear enclosures. I have used some dynomat, but the speakers are not enclosed. Umm... maybe I'll have to come up with something to enclose them then.

On the amp side of things, if I had 260w speakers front and rear, what would be an idea output from the amp to power them? Are the any rules for matching the RMS on an amp to the peak on the speaker? Or is it simply add the speaker maximums together (say 4*260) and get a 4 channel amp that has a maximum output of less than 1040w?

[mawby]

So would you recon the GZ enclosures would be good enough or should I make my own? Any tips?

Also, above question about amps. I asked two independant car audio specialists which one of these (http://www.justkenwood.co.uk/amplifiers.asp) amps they would recommend to power the above speakers. One said the 250W (http://www.justkenwood.co.uk/stock01/kac5201.asp) because "The 260W is the peak of each spaeker so to give them best sound out put you need to go for an amp with simmilar peak out put something like the Kenwood KAC5201 whitch is a 250W x2 channel amp.", and the other one choose the 350W (http://www.justkenwood.co.uk/stock01/kac6201.asp) one. So now I'm confused. When an amp says 250W and it's a 2-channel amp does that mean both channels can do 250W or the amp in total can produce 250W? If it's the former then the 250W amp would be correct for the speakers, if it's the latter then I can see the 350W amp being better.