How much efficiency loss at .5 ohm?

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Just getting back into car audio after a while and wondering if I already messed up. I helped a buddy on a project a couple weeks ago and as a payment he gave me a Lanzar Opti2000D amp since he knew I was looking again. He ran it at .5 ohm as it was designed to do and said he never had any problems with electrical so without doing my homework I ordered a dual 1 ohm subwoofer. I started looking into it and keep reading how inefficient amps are when running .5 ohm. I then thought that he had a 200 amp alternator and the two batteries in his diesel truck.

The subwoofer I ordered is 1500rms with ability to take more and have seen where the Opti2000D has benched at 1800 @ .5 and 1600 @ 1 so I just figured to go the .5 route without thinking of efficiency. Will it be a big difference running the amp at .5 compared to 1 ohm? I'm not sure if I should spend the money to send the subwoofer back and go with dual 2 ohm, sell the amp and get something different, or run it and enjoy?

It will be in a daily driver setup being used 30 minutes to an hour every day. Will probably not have it turned up extremely high most of the time but like to have the option. I have a 130 amp alternator right now. I just finished running my power wire tonight and will be doing the big 3 tomorrow. Any help is greatly appreciated. Thanks!!

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[hispls 5,000+ posts]

No telling what efficiency you'll see real-world. It's probably going to be rather poor though.

I wouldn't consider running an amp that size at even 1 ohm without an additional battery.

 

[garychurch84 10+ year member]

definitely need good electrical

 

[Hosted]

I forgot to put in my original message that I do plan on a second battery.

 

[n2audio 5,000+ posts]

FWIW - I have an independent test report on the Opti2kd from back when it was a forum boner amp.

According to the test -- at 1/3 output and 1/2 ohm it is 79%.

At full unclipped output, 1/2 ohm, it is 85%.

Full output at 1% THD measured 1962w. 1 ohm 1687.