View Full Version : Amp for Roswell 4 speaker combo

07-13-2012, 06:26 PM
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.


07-13-2012, 07:51 PM
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.

07-13-2012, 08:30 PM
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.

Earmark Marine

07-13-2012, 10:05 PM
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

07-13-2012, 10:20 PM
also would a kicker 700.5 be better. I would probably add sub next spring.

07-13-2012, 10:33 PM

07-14-2012, 09:09 AM
also would a kicker 700.5 be better. I would probably add sub next spring.

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.

07-14-2012, 11:26 AM
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.

Earmark Marine