to those with PE amps on DIY subs... (1 Viewer)

[Niraj Patel]

I'm not sure if this is the best place to ask, but its considerably more visited then teh DIY forum so I thought I'd give it a whirl here...

So I've put together my DIY 85L Dayton DVC based sub tuned to 22 Hz (or 20 Hz, I forget...). I am using a 250 watt PE amp to run it and it gets VERY hot after about 3-4 hrs of use (movies and music). Its not tucked behind and against a wall or anything, in fact, the amp is facing out and gets a draft of air (not a fan or anything, but A/C kinda draft). Its almost too hot to even touch. Its definently too hot to touch for an extended amount of time. Do these amps get this hot usually? My Dayton is wired in parallel to 4 ohms. The gain (I guess its called the gain) is turned up to about 5/8 to 3/4 max, the xover is around 60-80 hz, and the phase is dead center at 135 degrees. Any help is appreciated. Thanks!

Niraj Patel

 

[Rory Buszka]

The heat is nothing to worry about unless it regularly trips the thermal protection. Your phase should be set to either 0 or 180 unless you set the control to 0 (in phase) or 180 (out of phase) and find that you liked better what you got with the phase set to 135 in the first place. You might not have to turn the amp up quite so much, and the heatsink won't get quite as hot.

Oh, and yes, you SHOULD have posted this in the DIY forums, because more people will know just what you're talking about in there.

 

[Ryan Schnacke]

These amps do tend to generate some heat when used heavily. Heatsinks are supposed to get hot - that's how they do their job. When it gets that hot then you're probably nearing the limits of the amp. Don't push it far beyond that point. If it trips the thermal protection then consider putting a fan on it to flow more air.

The position of the subwoofer's gain knob is a very poor indicator of how much power you're pushing since there are at least 2 other gain controls in the system - your receiver has a subwoofer level control plus the main volume knob. My receiver has an additional volume control via its intellivolume feature. Still, most guys find that they never have to turn the gain knob above halfway to get good calibration.

"Your phase should be set to either 0 or 180 unless you set the control to 0 (in phase) or 180 (out of phase) and find that you liked better what you got with the phase set to 135 in the first place. "

That sounds a bit confusing to me. If your subwoofer is RIGHT next to your main speakers then, yes, you'll probably want the phase knob at 0 degrees. If you find that you're out of phase then I would switch the speaker leads rather than turning the phase control to 180 since the phase control adds delay. We're usually trying to minimize delay in our design (group delay) so why add it back in with the amp if you can avoid it?

If your sub is away from your mains then there's a good chance that something other than 0 degrees will be best.

 

[Niraj Patel]

Awesome, thanks for the help!

 

[Brian Bunge]

In my experience, there's absolutely no way to get even close to proper calibration with the gain control set that high. With my receiver, if I turn the sub out to minimum and the gain on the amp up to half I can't calibrate properly. So I always set the gain from 1/4-1/3 of the way up and then adjust the sub out on my receiver accordingly.

 

[Niraj Patel]

Well, my reciever is an old Onkyo model, back when Pro-Logic one was new. The only bass control is a knob on the reciever (theres also a treble knob... exciting). The only way I can get a decent output from the sub is to turn the gains up that much with the bass all the way up on the receiver. My next upgrade, naturally, is a reciever though.