Let’s say I have an 800w amp operating at full power. How much of that 800w is being turned into heat, and where? How much at the amp and how much at the speakers, sloshing air molecules around? How about the other equipment–if signal processor consumes 35w for the sake of my calculations I can assume it all goes to heat eventually, right? In fact, for the calculations of total heat load I might as well total up all the draws and figure they’re all going to heat, right?
Thanks, right?
It all ends up as heat, except for the small amount of energy that escapes the room in the form of sound.
The efficiency of the amplifier and speakers will determine how much power is converted to heat in each component.
Since it is my sworn duty to cause the Chihuly chandelier to explode into a trillion glass shards the moment this system is cranked I will assume more than “a small amount of energy” will become sound and the soundproofing will ensure that very little of it escapes. However, the nine :eek: 800w amps will be in a separate room so their only contribution to the theater’s heat load will be from that sound but is that really something I need to include in my calculations or do I just assume it’s all being released in the equipment room?
Don’t worry about the added heat from the sound in the theater if you mean a real theater and not just a home projection room. If your cooling system can handle the heat load from the people, the sound is a minor factor. Each person contributes about 120-150 Watts.
Good point, David, but other people are worrying about that. I’m just concerned with the equipment and I’m currently tracking down why the drivers on the unpowered subwoofers need heat sinks. Seems unnecessary unless they get pretty hot.
If you have a “800 Watt amplifier” it means it has the capability of supplying a maximum of 800 Watts (average and continuous) into a specified load.
If we assume the amplifier is really supplying 800 Watts (average and continuous) into your speakers (which is not unlikely), all of the 800 Watts eventually ends up as heat, one way or another.
Of course, if we wish to calculate the total heat load produced by the amp + speakers, you would need to add the heat produced internally by the amplifier + the 800 Watts dissipated by the speakers. There’s a simple way to do this… just measure the amplifier’s real & average power consumption at the 120 VAC outlet. All of the power it sucks from the outlet eventually ends up as heat.
Oh, you are worrying about the possible heat damage to the equipment? Get a fan and blow air over it and let those who are worrying about the building cooling handle it.
The only problem with that is with localized heat from equipment, the AC system would have the remainder of the building ready to hang meat by the time it had handled the equipment room.
We went through a similar situation in my fire company with the computer room, in that when the main thermostat showed 72F, it was over 85F in the room with all of the servers, etc. I totaled the equipment plate wattage and installed a 3/4T mini-split AC system for that room. Problem solved.
All of the power to the load, i.e. the 800 Watts is delivered to the speaker and it all is dissipated in the theater which you say someone else has to worry about cooling.
The heat load you have to worry about is the power taken by your units that isn’t sent out to the load. Chances are the units that are in the equipment room are not operating at unity power factor (don’t worry if you don’t know about power factor) but you’re on the safe side if you assume they are. On the equipment nameplate will be a voltage and current or a power input figure stated. Multiply the voltage times the current to get Watts (it isn’t quite Watts, but don’t worry about that) My WAG is that for an 800 W output unit the input power will be in the neighborhood of 3.5 kW. Of that 2.7 kW will be dissipated in the equipment room. That’s 2700 Joules/sec which works out to be about 9200 Btu/hour.
You need to worry about the equipment room, but the heat you are putting into the theater part, *i.e.[/;i] the 800 Watts output per amplifier, is only equal to about an additional 50 people.
If you have 9 of these beasts running you’re essentially running an 80000 Btu/hour furnace given that my WAG as to the 2700 Watts is close. That, I think, you need to take account of.
Well, I finally did the smart thing and looked up the specs on some high powered audio amplifiers. It seems they are more efficient than I thought and for an 800 W output you might have an input of only about 1500 W. That’s 700 W dissipated in your equipment room so your “furnace” is only a 22000 Btu/hour unit instead of the 80K of the previous post. Still considerable but not nearly so bad.
Oh? I’m supposed to have a $119,000 sound system laying around where I can look at the nameplates? (checking the shop to make sure I don’t) Well, I guess that shows what YOU know! 
“Only” 50 people? That is “only” four times the capacity of this theater!
Nowadays a lot of nameplates use “VA” as a unit for specifying power consumption. As you correctly stated, this is not real power consumption; it is “apparent power.” But because apparent power ≥ real power, using the apparent power value is a safe/conservative value to work with.