I am going to build a wall unit on either side of a fireplace. The one side will have a cupboard w/ 2 glass doors. What I was wonedering is...is it better to force in outside air OR push out inside air. I was thinking of installing a grill on the bottom w/ flexible duct running up the back. I would leave a couple of inches behind the shelves to allow for cabling and ventilation. If anybody has any ideas any input would be appreciated.

Kenny, I assume you're asking if it's better to blow air into the cabinet at the bottom, or to draw air out at the top. Naturally (pardon the pun), anything else would be to fight convection.

First of all, since I mentioned it, convection alone will probably suffice, as long as there is sufficient ventilation space at both top and bottom. Unless you're going to be running a lot of power, you shouldn't need a fan.

The power amp, or amp section of a receiver, will normally be the greatest source of heat. Many suggest, for that reason, placing either at the top of the stack, but it really doesn't make that much difference, unless again, you run at high output for a long time.

However, if you decide you want a fan, it's probably better to draw air in at the bottom, so the cabinet is slightly pressurized, otherwise you will find that dust enters through spaces between and around the doors. Even then, I suggest that you fit some sort of dust filtering ahead of the intake fan.

Home stores (Home Depot, Lowe's, etc) sell filtering material made to be used inside air registers, or grills, that can be cut to fit your intake grills. In fact, grills can be painted to match your wood, and installed in the toe-kick area below the doors. Grills above, the spaces around the doors,or openings into the space above the ceiling will probably be enough to allow heated air to escape.

Hope this gives you a place to start.

Larry

I think the answer to your question is draw air out instead of pushing air in.

Thanks Guys! I think I will go with a fan at the bottom behind the toe kick pushing air into the cabinet. Then have a "passive" grill at the top to let the air out. The dust part tipped the scales to the "air in" side!

One idea that has worked great for me is get a 4.5" 120VAC 62CFM fan form radio shack plug it into the back of your receivers switched outlet and set it right on top of your receiver or amp and have it push in cold air right onto the heat sinks. I use to have an old Denon AVR1700 back in the poor ole days when I was in school. I used to run the 1700 at 2/3 output or around 105db all week end long with the fan on it behind closed doors and no vent holes and it did a great job of keeping things cool. Having a fan at the bottom and top of a cabinet is good also but I feel things still get a little to hot for my likes. the fan cost $25.00

Good luck
Larry

Gotta watch the noise factor. Nothing worse for me than spending 20 grand on a system and hear the freakin' fan whir at every quiet passage in a movie.

larry, this is Larry

Many moons ago, I had the original dolby surround receiver, the Pioneer VSX-5000. I had a fan standing on edge behind the receiver, much like you described. It stayed cool all right, but it collected a mountain of dust, mostly inside the chassis, which I feel eventually blocked more cooling air than it benefitted. (Did that come out right?) Dust is a fairly good insulator. Just a small warning for the unwary.

Larry

I have just had an A.V. cabinet built and had a similar problem with heat disipation. The problem with most commercially available fans is the noise they generate when on. Try www.papst.com who specialise in
low noise fans and have a huge range available. Before buying any old fan, there is a formula on their site which you will need to run through to calculate how many litres of air you need to shift per hour to keep the equipment at the right temperature, this is based on the wattage(heat generated)of your equiptment. Once you've worked this out then you can choose your fans. Remember that more fans running at a lower speed will produce less noise than 1 fan running at high speed.
You can't order direct from Papst but I tracked them down through www.farnell.com in the U.K. I ordered 3 x 80mm 240v fans (they also do 115v versions for the U.S.)and then knocked up a thermistor kit from [Link: quasarelectronics.com]. to turn the fans on and off dependant on the cabinet temperature. Remember to be careful mounting the fans as even though they are very quiet, if tightened to the cabinet, mechanical noise will be transmitted. I got around this by mounting them in foam rubber.

Result No heat-No sound-Happy Bunny.

Hope this was of some help