Running 8ohm sub with an amp optimized for 4 ohm

i have a crunch 1000W amp that runs off 4ohms when bridged and a crunch GTR 10" 700W sub with dual 4ohm voice coils, the dumbasses who sent me the wrong speaker said to wire the sub in series, with the dual 4ohm voice coils (they were supposted to be 2ohms each) that would make 8ohms.

Now with 8ohms instead of 4ohms, how will this affect the sound/power output of the sub and amp, will it be only half the power? My amp cannot run at 2ohms bridged.

Your amp would put out roughly half the power @ 8ohm as it would @ 4ohms. You could get another sub exactly like the one you have and run them both in series. That would be a 4ohm load, but you would only get around 500Watts to each sub. Assuming the 1000Watts is an rms rating and not a peak rating.

you could also buy some resisters to bring the ohms down.

you need to wire each voice coil in parallell with each other, not series, series would double your impedance

I don't think it would be half power. Maybe 20-25 percent loss power because of the more resistance. I played in rock bands for 25 years. I always ran my Marshall Amp at 8 ohms into a 16 ohm cabinet. It actually made it sound fatter. There was probably some power loss ,but not enough to notice.
If you choose to keep the dual 4ohm subs that they sent you, wire them in series not parallel. Series will give you 8ohms, parrallel will give you 2ohms.
You are safe having your amp pushing to a higher impedence, such as your application , amp output at 4ohms, subs resistance at 8ohms. The opposite, amp output at 4ohms, speaker resistance at 2ohms would put your power amp at risk of blowing. The best way is to have matching impedence. But if you can't, it's always better to have the speaker impedence higher not lower than the power amp.
If you don't bridge your amp, won't that give you a 8ohm output?

I have a 800.2 (rated for 800w at 1 Ohm stable) rockford and a 12" JL W6 which rated for like 400w I think. (Sub was originally had a RF HX2) The sub is dual 4 Ohm VC and I have it wired in series and put that bridged to my amp. And it has worked great. Keeps the amp cooler too now. I don't even have the amp turned up past 1/2 way and it does a great job.

~K