4 speakers on a 2 channel amp?

(ispair) · (ispair) **Join Date: May 2006** 07-31-2008, 10:20 PM

I have a question for you audio guru's. I have 4 6.5 Polk speakers that are installed in the boat. Right now they are just being powered by a Pyle head unit (I think its 50X4). A buddy has a Rockford Fosgate P5002 2 channel amp that he's got "laying around" that he'll sell me for cheap. Can I run this amp for all four of the Polk speakers? If so, what is the best way to set it up. Here are the ratings for the speakers and amp.

Polk 6.5's:

RMS power handling (watts): 60
Frequency response (kHz): 35Hz - 22kHz
Peak power handling (watts): 180
Peak power range (watts) 150-249

Rockford Fosgate P5002:

Amplifier Type Dual Channel
Amplifier Output 2-channel
Power RMS Power 125 Watts x 2
Output Details 125 Watt - 4 Ohm - 2 channel(s) ¦ 250 Watt - 2 Ohm - 2 channel(s) ¦ 500 Watt - 4 Ohm - 1 channel(s)
Output Power 500 Watt

Features High Pass Frequencies 40 - 400 Hz
Low Pass Frequencies 40 - 400 Hz
Response Bandwidth 20 - 20000 Hz
Bass Boost Frequency 45 Hz
Bass Boost Gain 0 to +18dB
Crossover Slope 12 dB/octave

(rson) · (rson) **Join Date: Jun 2002** 07-31-2008, 10:35 PM

since it is a 2 channel amp, run them at 2 ohms stereo by just running pos to pos and neg to neg.

Each speaker will be getting 125 watts each which is over the rated load but your should be fine, turn down the gain on the amp and all should be good. You will notice a great difference from the pyle amp.

(rson) · (rson) **Join Date: Jun 2002** 07-31-2008, 10:37 PM

oh yeah, set the cross over high so the speakers don't play hitting bass. This will save your speakers.

(chpthril) · (chpthril) **Join Date: Oct 2007** 08-01-2008, 4:28 AM

Since you do not have a sub, I would set the x-overs to "off" or "full", which ever is says.

I would recommend setting the gains in a normal manor, the Polks will handle 125W just fine.

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 08-01-2008, 6:03 AM

I've had bad luck showing 2ohm loads to class a/b amps in boat. I do live in houston where summer temps easily reach 100+, but w/o fail any time I would run an amp seeing that load they overheat after 3-4 hours of play time. You can alwasy add a fan to help cool.

(hatepain) · (hatepain) **Join Date: Aug 2006** 08-01-2008, 10:18 AM

I'm with TM go "full" but keep the gains down so you don't over power them and blow em.

(ispair) · (ispair) **Join Date: May 2006** 08-01-2008, 1:18 PM

The amp crossover switch says LP-AP-HP. Which one should I choose? Also, the frequency dial is rated in Hz not kHz like the speakers. The dial is numbers 40, 55, 80, 160, 220, 320, and 400. Which number should I set it on?

While i'm asking questions, there are three slots on the right side of the amp labelled REM, GND, and B+. Is the REM slot for the continuous power, GND for ground (obviously), and B+ for the positive lead to the battery? Thanks for your help guys

(chpthril) · (chpthril) **Join Date: Oct 2007** 08-01-2008, 1:50 PM

AP = all-pass, thats what you want.

REM = "remote turn on" from head unit
GND = ground to the battery
B+ = positive to the battery

(timmy) · (timmy) **Join Date: Jul 2001** 08-01-2008, 2:10 PM

I would set it HP at 40Hz. You are not going to get anything useful below that out of 6.5" speakers especially if they are not in an enclosure.

(ispair) · (ispair) **Join Date: May 2006** 08-01-2008, 3:45 PM

Is it possible to run a small sub with this 4 speaker set up also, or am i getting carried away? I was thinking maybe a 10" sub?

(hematoma) · (hematoma) **Join Date: Jul 2008** 08-01-2008, 6:27 PM

LOl, yup carried away. I would watch the temp on that amp for real. Its not designed to run 4 speakers at 2 ohms. Just a heads up.

(joe_crawley) · (joe_crawley) **Join Date: Jan 2007** 08-01-2008, 7:19 PM

You'll be fine at 2 Ohms. Set the high pass to 80Hz and you'll won't have any problems with the low impedance load, and those 6.5s can't make any useful bass below 80 anyways.

(audiopro74) · (audiopro74) **Join Date: Jun 2005** 08-01-2008, 11:59 PM

Tim had the best advice, followed closely by gangstar. 40 might be a little low, but depending on operator 80 might be cutting off a good part of your tunes. That amp will play 2 ohm stereo, running some 6 1/2's, all day long. As long as you don't let the battery get too low. And Mike Has it for the pwr, gnd, rem. The rem, should hook to the blue with white stripe wire on the back of the headunit.