Ugh...Overheating Sansui amp

I have a Sansui 8700DB rated at 500 watts (160 wpc rms at 8ohms). Was blowing woofers in my Klipsch KG4's (rated at 100 watt max) and decided to get new speakers.

So i picked up a pair of the new Cerwin Vega XLS 215. Great speakers btw!!!

They are rated at 500 watt max with an impedence of 6 ohms. When I called Cerwin Vega they said it was a "typo" and they were really 4 ohms, but still compatible with 8ohm amps.

I dont know if they are trying to suck too much power out of my 8ohm amp or what, but after playing for a couple hours and modest to loud volumes, my amp protection cuts in and my amp cuts out. Havent found a definate pattern yet though. But its always after extended use.

I assume its the thermal protection turning on. Have been using a small fan to blow against the amp radiator fins to no avail.

I just wonder cause I know these speakers can be driven much louder than what I am driving them. My ears wouldnt allow it though. I thought a 500 watt amp could power them all day without hesitation.

What am I doing wrong?

Those are huge speakers with 2 active 15" woofers. I guess they need more juice and your amp gets hot because they get all the power. The Ohms may have something to do too

I'm not sure it's well vented if it's in a wooden case so a fan blowing on the heat sinks may not be enough. As a bandaid approach you may try running it naked and cooling the insides with your fan. I once had an amp that made 95 watts into 8 ohms and 180 watts into 4 ohms but with 84db sensitivity speakers (also 4 ohms ) it ran hot as a griddle. I sold those speakers and replaced them with more efficient 8 ohm speakers

A 4/6 ohm speaker will draw more current from your amp which will produce heat, the amp needs a lot of ventilation or air around it. The fan won't do much if there isn't some place for the heat to dissipate. If your shelf isn't open in the back I'd move the amp to an open area. If that is a vintage amp it was most likely designed for 8 ohms so if the xLS are drawing 4 ohms it may be too much, it depends on the quality of the amp and I'm not familiar with that one. I will say I drove my 4 ohm, 86dB, Dynaudio Audience 60's with a Sansui AU9500 integrated with no problem.

Hopefully you only have the one set of speakers hooked up? Also, my Sansui had a switch for speaker A, B, or A/B, make sure the switch is just in the "A" position if only one pair of speakers.

You might try looking for a used Adcom 555 or 5500 if you have the funds, they should be had for under $500.00. No matter the amp you'll need a lot of air around it.

I should also ask about the AWG you are using. As a general rule if you have a high guage wire that is running a long distance, you will have heat problems with your amp. You generally want a low AWG wire (say 12 or 14) that is in a short run from the amp to the speakers. It may be a simple question of impedence. ( if you have to move a wheel barrel 100 yards, and the wheel barrel is empty, the effort to move this wheel barrel will be easy. On the other hand, if you move the same wheel barrel the same distance, but now with 200 pounds of stones in it, you will need more power to move it). This may be the issue with your speakers and the reason why your AMP is overheating. It is having to work too hard based on the demands you are placing on it. So I recommend a thick wire that is run a short distance. If this is not the problem, it is most assuredly the problem listed above.
Good luck and let us know how it works out.
Dwayne

160WPC @8 Ohms does not make a 500 Watt amp. The 500 Watt rating is probably the current drain from the wall.

it's not a 500 watt amp, it's a 160watt/ch amp, but it still should handle the CW's with ease...

It's probably going into protection mode indeed.
I don't know how loud you like your music, but that's pretty hard to do :D

do you have a multimeter? it's an older amp, might need a recap, some drifted values too, you should measure DC offset (more info here: http://www.audiokarma.org/forums/showthread.php?t=5634 - it's not hard at all...)
if those values are too high, it might add to the heat, and also explain how it's possible that you've blown the woofers on your Klipsch speakers...

bias might also be off (this is harder...), a technician should do this...

it's a good amp, but it might just need some love too...

(unless you are listening to your music SO loud, that various things are falling off the wall)

Good luck,
Bert.

I bought the Sansui at a local shop. The only one in Austin texas that deals in vintage gear. Had a full refurb. Got a floor fan blowing on it now. Overheating not an issue as long as i dont play at concert level volume for more than 2 hours.

Its in a cramped shelf currently. Very tight fit with barely an inch above the vents in the top rear of the amp. Once i get a friend over, will move it to a lower shelf and remove the glass shelf above it to help with venting heat

Yeah, sounds like ventilation is the issue. Come on Big Perminator surely the amp isn't that heavy you can't toss it around :)