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    CTamp78's Avatar
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    Very confused about amp specs

    Hi Everyone...My profile contains info on my current boat setup. I've just added a wake tower and purchased 2 Rockford Fosgate 8" speakers (M282-WAKE) to mount to it. Speaker specs- 100 watts RMS (200 watts peak power), 4ohm. I'm content with powering my 4 existing 6" speakers with my head unit but I would like to connect an amp to the 8" guys up top.

    I took a walk through Best Buy today and looked at the Polk PA-330. The display said it was a 300W Class AB 2-channel amp. I figured it would be perfect for my application and assumed that a 300W 2-channel amp would push 150W to each speaker. I did some research on the amp and the specs from Polk indicate that the amp will provide 75 continuous watts per channel at 4 ohms. My experience is limited but wouldn't the specs seem to suggest that this is a 150 watt amp (75 x 2)?

    The specs also say the following:
    Continuous Watts per Channel (2 Ohms) RMS 100 x 2
    Continuous Watts Bridged 200 at 4 ohms
    Peak Power Watts per Channel (4 Ohms) 300 x 1
    Peak Power Watts per Channel (2 Ohms) 200 x 2
    Max Power Watts per Channel (4 Ohms Bridged) 300

    I'm looking for the best amp or at least a good amp that would maximize the potential of the two tower speakers without damaging them. I initially thought that the Polk amp was the way to go, assuming that I'd be pushing 150W to each speaker. Now I'm very confused about exactly how many watts this amp will provide to each speaker based on the specs. Again, my amp experience is limited so if anyone can clarify this for me or recommend a different amp based on my setup, it would be greatly appreciated. Thanks a lot!


    Gary







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    Lexicon740iL's Avatar
    Lexicon740iL is offline AGM FTW!



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    Re: Very confused about amp specs

    I wouldn't take any peak ratings into consideration. Amp or Speaker wise.

    Those speakers listed say they are 4 ohm & 100W RMS "Continuous"

    If the Polk does 75W RMS per channel @ 4ohms it should be a nice match for those speakers. If you have your eye on another amp and your using 4ohm speakers that just get as close to the RMS or Continuous watts per channel rating on your amp as the RMS rating of the speakers.

    A 2 Channel that does 100W per channel at 4ohms is a perfect match to your speakers.

    Some people choose to use a pair of speakers with the voice coils wired together to create different ohm ratings.

    For instance if you take two 4ohm single voice coil speakers and you can wire them up to show an amp 2ohm load. Then you would base your amplifier selection of what the amp is rated for at 2 ohms.

    When an amps is run at a lower ohm load it puts out more RMS power per channel that why the specs of an amp are different at 4ohm and 2 ohm loads.

    My amp does 500w RMS at 4ohms, 900w at 2ohms or 1200WRMS at 1ohm
    So I choose to use a sub that has dual 2ohm voice coils so I can wire it to show the amp 1ohm and get the most watts out of it.

    That's a pretty generalized breakdown on amp ratings and matching speaker ratings correctly.




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    Re: Very confused about amp specs

    Quote Originally Posted by Lexicon740iL View Post
    I wouldn't take any peak ratings into consideration. Amp or Speaker wise.

    Those speakers listed say they are 4 ohm & 100W RMS "Continuous"

    If the Polk does 75W RMS per channel @ 4ohms it should be a nice match for those speakers. If you have your eye on another amp and your using 4ohm speakers that just get as close to the RMS or Continuous watts per channel rating on your amp as the RMS rating of the speakers.

    A 2 Channel that does 100W per channel at 4ohms is a perfect match to your speakers.

    Some people choose to use a pair of speakers with the voice coils wired together to create different ohm ratings.

    For instance if you take two 4ohm single voice coil speakers and you can wire them up to show an amp 2ohm load. Then you would base your amplifier selection of what the amp is rated for at 2 ohms.

    When an amps is run at a lower ohm load it puts out more RMS power per channel that why the specs of that polk are different at 4ohm and 2 ohm loads.

    That's a pretty generalized breakdown on amp ratings and matching speaker ratings correctly.

    Thank you. That makes more sense to me. This may be a dumb question but how do I ensure that the amp is running at 4ohms versus 2ohms?




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    Lexicon740iL's Avatar
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    Re: Very confused about amp specs

    The amp will run 2 or 4 ohm automatically on it's own dependent on what the speaker you connect to each channel is rated at. There is not a switch or anything.

    It gets more complicated when your speaker has two voice coils or your bridging the channels of your amp.

    There are some good links in the FAQ sections on sub wiring for different ohm loads.

    The amp connections on the other hand will be specific to the amp and covered in the literature with the amp. Weather it be a two, four channel or monoblock the speaker connection wiring may vary.

    I just looked at the speaker on Rockfords site. It is a single 4ohm speaker pod. and in product description it actually says 75W RMS in the description but 100W RMS in the specs page. So I think that polk u looked at would be a good match for the specified wattage.




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    Re: Very confused about amp specs

    U need a amp that gives powers you want @2 ohm since you have a pair s4 subs..if your intent on best buy amps then look for a monoblock for power @2 ex..alpine, fosgate, etc




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