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  1. #1
    Join Date
    Jul 2012
    Location
    Vonore TN
    Posts
    9

    Default Amp for Roswell 4 speaker combo

    is a Rockford Fosgate P400-4 to much power for a roswell 4 combo speaker bar? Speaker specs say

    RMA 6.5" coaxial
    Power rating: 75W RMS / 150W peak
    Frequency response: 70Hz - 20kHz
    Impedance: 2 ohms per channel (wired as 2 channels)

    and say use the Roswell 500.4 which has these specs and is to be used at 2 ohms
    Power Output @ 14.4V
    75W RMS x 4 (@ 4 ohms)
    125W RMS x 4 (@ 2 ohms)

    The Fosgate specs are
    50W x 4 @ 4-Ohms RMS
    100W x 4 @ 2-Ohms RMS
    but has dynamic power of upto 148 watts

    I just want to put right power to the speakers and I found the Fosgate amp at about half price of the Rosell amp, and I know Fosgates amps are usually more power than rated.

    thanks
    Shawn

  2. #2
    Join Date
    Jun 2007
    Location
    Vancouver, WA
    Posts
    3,522

    Default

    2 speakers x 75 watts = you want 150watts RMS going to each "channel" or pair of speakers. (or more)

    Looks like the Fosgate is close to that, the Roswell even closer if they are higher output than advertised.

    Unfortunately it looks like you can't bridge the Fosgate amp and be stable at 2ohms.

    Another option - you could run a 2-channel amp, wiring your pairs of speakers to 2ohm as you are saying, maybe save a little coin and get higher power.
    2001 MobiusV

  3. #3
    Join Date
    May 2009
    Location
    Dallas, TX
    Posts
    880

    Default

    Shawn,
    As mentioned above you should ideally have a two channel amplifier to drive four 4-ohm tower speakers.
    Tower speakers usually get pushed inordinately hard and will generally handle more power than their rating because you are operating in the highpass mode. I would want 75 watts minimum to each of four speakers.
    If you must use a four channel amplifier you would series the tower speakers and bridge the amplifier in order to limit the tower harness to 4-conductors. Bridged into two channels into an 8-ohm load will produce the identical power as running discrete four channels into a 4-ohm load. And, that (50 watts per speaker) is the best you're going to be able to do with the referenced Fosgate amplifier.

    David
    Earmark Marine

  4. #4
    Join Date
    Jul 2012
    Location
    Vonore TN
    Posts
    9

    Default

    thanks for replays guys. so a 2 channel is al i need instead of 4? i forgot to add this part from the Roswell site

    *NOTE - Each side of the Quad Spin Combo is wired in parallel, creating a 2 Ohm load per channel. Please ensure that the amplifier you choose to power it is 2 Ohm stable for your wiring application.

    does this change anything do i need 2 ohm only its been awhile since i have dealt with any amps or speakers

    Thanks again
    Shawn

  5. #5
    Join Date
    Jul 2012
    Location
    Vonore TN
    Posts
    9

    Default

    also would a kicker 700.5 be better. I would probably add sub next spring.
    Thanks
    Shawn

  6. #6
    Join Date
    Jan 2008
    Location
    Keuka Lake, NY
    Posts
    5,489

    Default

    Yep.......
    A Day at the Lake...Priceless
    A Day in Powder...Endless


    Joe V
    2012 Möbius XLV~ Loaded & Exiled
    2007 Outback V ~ sold

  7. #7
    Join Date
    Oct 2010
    Location
    Lake Wylie NC Area
    Posts
    631

    Default

    Quote Originally Posted by ShawnTN View Post
    also would a kicker 700.5 be better. I would probably add sub next spring.
    Thanks
    Shawn
    The Kicker zxm700.5 will deliver 70 x 4 @ 4 ohm, 85 x 4 @ 2 ohm and 165 x 2 @ 4 ohm. You will still have the same configuration hurdle as you have with the other 4 chnl amps you are asking about. IMO, this amp is better suited to run the entire in-boat setup, rather then running towers and in-boats. This is mainly due to RCA routing and configuring.

    The best solution will be a 2 chnl amp as noted above. Other wise, you will need to rewire the pods and series the two pairs so you net a bridgeable 8 ohm load. Then you can use a 4 chnl.

  8. #8
    Join Date
    May 2009
    Location
    Dallas, TX
    Posts
    880

    Default

    Just like Mike (MLA) wrote, the highpass channels of the 5-channel amplifier are still effectively a four channel amplifier which really doesn't fit the application.
    Go with a stable 2-channel amplifier with 150 to 200 watts per channel into a 2-ohm load for these particular speakers. Going larger gives you more future upgrade options if over time you become disappointed with four conventional speakers trying to project over distance.

    David
    Earmark Marine

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