I have 2 alpine type R 15's. They are both dual voice coil 4 ohm. I wired them both in parrell to get a 1ohm load to the amplifier. My question is I have a 1500 watt class ab 2ohm stable amp until i can get anotha amp. Can i still hook up my 15's even though it will be 1ohm load.

No.

what will happen to THE amp

At best, it will go into protection. At worst, damage.

what will happen to THE amp

You will mess it up by playing it under its recommended ohm load rating. It may work for a minute, day, month or cut off right away and wouldnt be a smart idea.

Depends on the amp. What amp is it?

Depends on the amp. What amp is it?

...I have a 1500 watt class ab 2ohm stable amp...

as in some amps are stable below what they are rated.

as in some amps are stable below what they are rated.

Typically not class A/B amps, thats why I requoted it.

Old school Class A/Bs are.

Old school Class A/Bs are.

I wouldn't go that far. The one's that were were labeled for high current and generally had a switch. Most were rated for 4 ohms mono and anything under that nominal figure was pushing it. Of course old school to me is late 80s/early-to-mid 90s.