PL 400 for 4 ohm subs.

[Oldskoolfan]

I am building a passive subwoofer with separate left and right drivers. They will be driven by a PL-400 that is fed by a Rolls active sub crossover. The drivers are 4 ohm impedance. I know that can be problematic for the 400 at hi output levels. I'm using this in a home system and unlikely to be pushed beyond 50 watts, and then not for more than a song or two. Should I be concerned about the impedance?

 

[laatsch55]

No...monitor heat sink temp until you know you dont need a fan . If it warms up , put a fan on it. My K's woofs are 4 ohm and a WOPL 700 needs a fan when I romp on it..

 

[George S.]

A 400 WOPL will power two 4 ohm subs perfectly fine. Actually, better than just "fine", the 400 WOPL kicks ass as a stereo 4 ohm sub amp.
Mine powered two Dayton Audio 12" Ultimax (two 2 ohm voice coils in each driver wired in series for 4 ohms) in the standard sealed enclosure kits. Ran them with a MiniDsp 2x4 active crossover giving them a frequency slice of 20-80 Hz.
Tested them in stereo mode to YouTube subwoofer test tones that made the house windows shimmer with vibrations and the neighbor's could feel. I really annoyed a lot of people on that day of testing.
The WOPL never broke a sweat and wasn't close to running out of headroom.
Hottest part of the amp was the transformer, not the heatsinks.
A 400 WOPL is a excellent stereo sub amp, even at 4 ohms. No fans needed.
Elevate the amp on rubber feet, provide open air around it, feed it a smaller spectrum slice with a active crossover. It'll crank louder than you can stand and just get warm.
My current crossover running four amps, subs now get a 10-50 Hz slice. The crossover is very important regarding how the amp operates.

 

[Gibsonian]

Will work fine at 4 ohms, have run these here alot with 400 and 700. My main system is running a 700 right now at 4 ohms. It all depends as Lee said how hard you use them. Hard for more than 15 min straight, you will likely need a fan. Say you have some rock loving buddies over, a few drinks or something, a shared love of high SPL, and you'll likely need a fan. Most folks won't because they don't listen that loud for that long. I don't listen as loud as I used to (aging thing I think) and I haven't used a fan at all in quite sometime whereas I used to use a fan much of the time.