I am building a new home with an audio closet for my stereo equipment (950/770 combo). I am concerned about how to vent out the heat generated from the 770. Does anyone have a simular set-up and how did you take care of the heat ventilation?

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dfs

I am still in the process of sorting through this myself, but I am always a bit surprised when I open my cabinet that houses only the 950 and 770. Each on a sep. shelf in a space 36 wide by 40 high and 34 deep. Theres a lot of boxed in heat. I am going to try and open up a vent in the shelf above that is open to roon air and see hoe convection works. A number of people have recommended some sort of fan also to keep circulation. If you are housing all your eqip in one closet you might at least consider putting the 770 at the top.

I haven't tried to do this (my stuff's in an old entertainment center), but the 770 will definitely need some air movement -- without some sort of vent, you effectively have a space heater in an enclosed space, and the temperature will rise steadily until it is a danger to the equipment. The 950 puts of comparably little heat, but still needs a little ventilation. In a totally enclosed closet with a lot of gear in it, I'd look at perhaps an undercut or louvered door and maybe a ventilation fan (something that could discharge hot air into an attic, for example).

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

ive known people to put a computer power supply in their racks and connect some (computer) fans to it. i dont know if you are into computers, but i know i have some extra power supplies and fans. plus you can get the stuff cheap and its an easy and quick fix even if you dont have any spare stuff.

For that matter, little bathroom vent fans can be had at Home Depot for under $30 -- and they'll move more air through a closet than a PC case fan, without the heat gain from a PC's power supply (which has a 120V to 5V transformer in there, all nice and toasty, while that little vent fan has a fractional horsepower motor that produces much less heat).

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

OK, I got to thinking about this some more this morning and dug out some notes from a recent project. Real-world heat gain data from electronics like amps is extremely difficult to pin down -- in addition to being somewhat dependent on the actual load being driven (at least for solid state amps; tubes should be a lot easier to figure out since they are more like incandescent lights), there is no guideline or standard for measuring heat gain of electronic equipment. It's all a little fuzzy, but I recently took a stab at guessing some realistic heat gain values while doing loads on a facility that included viewing rooms equipped with 5.1 surround systems. Keep in mind that all of this mumbo-jumbo is assuming that the equipment is located in a small closet with no ventilation (closed door, no air vent, ...) -- sort of a worst case scenario.

Assuming a fairly typical system -- five channel amp, 150W or so per channel, pre/pro, DVD, satellite or cable box, maybe a VCR -- the peak electrical consumption will be over 2000W. Not all of that is heat gain, and that consumption is the peak anyway. I ended up estimating (guessing -- gotta go with the SWAG sometimes) that a system like this might generate 1000W of heat. It could be even higher, but for the sake of argument even this ends up being a significant load. So we've got 1000W, which equates to 3412 BTU/hr (or about 0.3 tons of cooling load). If we plan to cool this by ventilating it -- drawing room air through and dumping the hot air somewhere else -- we want to establish some limits on the temperatures we'll allow. The entering air will be 75F (could be lower depending on where you have your thermostat set, but 75F is a safe value in a house), and I'd like to keep the discharge air below 90F if possible. With 3400BTUH and a 15F temperature change, the air flow required is approximately 210 CFM (cubic feet per minute; CFM = BTUH/(1.08*delta-T)) -- in a small, totally closed closet, that's a lot of air, over 1.5 air changes per minute in a 4x4x9 closet. A 1" undercut on the door will allow about 100CFM into the room, so a louvered door or door grille would be needed to get that much air in. The air could be discharged into an attic or to the out of doors, but you want to keep the discharge ductwork short to minimize the work required by the fan.

Bathroom exhaust fans range from 50CFM to 110CFM ( this fan , for example, will move 110 CFM and sells for around $50), and can be easily configured to discharge straight into the attic or to a louver or roof cap. Other exhaust fans (such as this one ) can be had that will go up to 210CFM pretty easily. PC case fans can move 35CFM (for an 80mm fan) to 75CFM (for a 120mm fan), but with no more than 0.10" of static pressure. An exhaust grille alone could generate 0.05" to 0.10" of static pressure drop, making it very difficult to get all this hot air moved anyplace very remote. "Wall wart" AC adapters could be rigged to power these fans; many people use such adapters connected to the accessory outlets of receivers to power small fans. A PC power supply could also do it, but the larger AC/DC transformers will add a lot of heat -- typical PC's produce around 100W of heat, due primarily to the CPU and power supply (with some also due to the hard drive and such). Adding 50W of heat from the power supply equates to over 150BTUH, or a 15%+ increase in load.

On paper, there's not much if any factor of safety in these numbers (the numbers could even be considered low, if the nameplate data is to be believed). In reality, I would guess that a safety factor of 1.5 or more exists in these calculations. If you had 100CFM+ of air movement (an undercut or louvered door and a decent exhaust fan) in a small, otherwise sealed equipment closet, you would probably be OK, and a week or so with a cheap digital thermometer in the closet to track temperatures would let you know for sure. In a freestanding equipment rack, simple openings in the rack or a 120mm PC fan powered by an AC adapter ought to be able to keep things under control. In any scenario, I'm assuming that you have the recommended clearance around equipment (especially the amps) so that they can get air in and out readily.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

Thank you all for your suggestions, especially GONK. You've all given me a lot to think about. The closet is about 4x4x9 with a pocket door in the theater room and a rear solid door (for access to wiring) in a spare bedroom. I should be able to give an inch for hte rear door and add bathroom vent into the attic (above the equipment closet). Now I just need to locate one that is as quiet as possible...

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dfs

Look into these Panasonic models. They are VERY quiet.
www.panasonic.com/consumer_electronics/bp_ventilation_fans/default.asp

That sounds like a plan, then. Let us know how it turns out, dfsmks.

And those are some very quiet little fans -- the FV-11VQ2 is rated at 1.5 sones, which may be the lowest I've ever seen on a fan.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

gonk, you have a lot of freetime or a very boring job! j/k. interesting data you calculated above. i dont know too many people who have that kind of airflow in their racks... a lot of exhaust fans are pretty noisy, well too noisy to be acceptable in a ht. i would recommend a configuration of an array of fans that suck air from the bottom and pull it up through the system and eject it at the top. cooling is achieved by pulling air across a surface much more quickly than allowing the heat to naturally radiate and then eventually being pulled out. hence the design of computer heatsinks. id think his whole house would be hot with 75 as the room temp.

Wow. I spend an evening and morning getting the house ready for a potential buyer to look at today, and come back to a ton of new posts this morning! Heat rejection isn't exactly as fun a topic of discussion as tubes or subs or LCD/DLP/LCOS, but what the heck -- it might be a useful thread for some folks out there. And we've had some mighty fine expert input from electricians, EE's, and industry insiders over the last couple years, so I may as well toss in my two cents on cooling.

As I mentioned, this is my job -- I'm a professional mechanical engineer and I design HVAC systems (and some fire protection) for commercial buildings. In the design that I developed those numbers for, we were able to throw <55F air at the area year-round, but in a house your furnace won't provide cold air in the winter, and I doubt you want to try to install an airside economizer just for the equipment closet, which is why the typical choice is to use a fan to just ventilate a hot equipment rack in a home system. These are also just general numbers. For example, while many people keep their houses around 72 or so, most residential (and commercial) HVAC systems are sized to maintain 75 on a design day. And for all I know, dfskms likes his house warm or likes to keep his utility bill low and has the thermostat set to 76 in the summer. As for the fact that most people don't move that much air through their gear, you are exactly right. Many people don't ventilate at all, and convection alone does the best it can for them. However, my numbers were for a sealed equipment closet -- something that very few people actually have. In such a closet, fan noise would be less critical as the fan is pretty remote and isolated from the viewing/listening area and heat buildup would be much more likely to become an issue. Besides, the fan that Keta recommends is extremely quiet (somewhere around 45dBA, although the conversion from sone to dB is pretty clumsy). For the average equipment rack, most can be operated without any fan (and without any fan noise), but as you and I both mentioned, those that are a bit enclosed or crowded should be able to get by with a well-placed small DC fan such as a 120mm PC case fan. I do recommend not using a salvaged PC power supply to power the fan(s), however.



Since this is a subject I spend a lot of time with (albeit at a much larger scale than a CPU), I just wanted to clarify some heat transfer here. The heat sinks on a computer chip are not based on airflow -- in fact, fans weren't added at all until the 486 and weren't common until the Pentium. A heat sink (whether in a PC or in an amp like Outlaw's 755 and 770) is a highly conductive material with as much surface area as possible. By using a conductive material, heat can be carried rapidly away from the heat source through the sink to the air (hence the widespread use of aluminum and copper in heat sinks and the complete absence of asbestos heat sinks ), and by providing a great deal of surface area in a small space the sink can reject more heat. (The five heat sinks in Outlaw's original amp, the Model 750, combined for almost two thousand square inches of surface area, all in a 7" high chassis with a 240 sq. inch footprint.) Adding a fan does accelerate the heat rejection as you note, but the heat sink itself functions with or without a fan to draw air across it. That's why most good amps increase the size of the heat sink and eliminate the fan -- they are rejecting the same amount of heat to their surroundings either way, but by eliminating the fan they are cooling the amps quietly and without the danger of a failed fan allowing the gear to overheat and malfunction.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

i would agree that a good heatsink can not need a fan, but a heatsink benefits a great deal from having a fan pull the heat away from it more quickly. if you had fins on a heatsink that were really long then you wouldnt need a fan as much. it obivously depends on how hot something is going to get whether you need both or just a heat sink.
i was a little hasty to post my idea about cooling, rereading that he is building his house i would totally agree that exhaust fans would be best and not that difficult as its new.
the power supply with fans idea (from computer) works very nicely though, but it is more for standalone closed racks where you could mount the ps to the back (where its heat doesnt matter) and cut out holes so that the fans can suck out the heat.