How much ventilation space is REALLY needed?

[Boomzilla]

The majority of Emotiva's amplifiers run pretty cool. The only exception I've found is the XPR-2. The conventional wisdom is that amps need a bare minimum of 0.5 to 1 inch of overhead clearance in a shelving unit to adequately ventilate. Such recommendation, though, seems to have been derived by assuming continuous, high-power output (worst-case scenario).

So my question is, assuming that the amp will be driven neither at high power nor continuously (think surround-sound rear channels, etc.) then the lower heat generation should, theoretically, require less overhead clearance for ventilation.

My shelving units have 8" clearances. I can shoehorn my XPA-5 into that shelf, but with less than a half inch clearance above. I plan to mount the amp in that gap, watch a movie, and stick a thermometer into the gap. What's the highest temperature that I should consider "safe" for the long-term viability of the amp's electronics?

Assuming that the temperature is "excessive," (whatever that might be - KeithL ?) is it feasible to use a forced-air fan to compensate for the lack of natural-draft?

Boomzilla

[pop]

I prefer to go no underwear with a little powder for full natural-draft. Hope this helps.

[DYohn]

Most consumer electronics are rated for at least 70C continual operating temperature and some for much higher. 105C is also a very common rating. In general, placing an amplifier with less than 1" of air gap on top is less than desirable, but many amps can operate with less than that.

[novisnick]

Jul 10, 2014 10:47:48 GMT -5 Boomzilla said:

The majority of Emotiva's amplifiers run pretty cool. The only exception I've found is the XPR-2. The conventional wisdom is that amps need a bare minimum of 0.5 to 1 inch of overhead clearance in a shelving unit to adequately ventilate. Such recommendation, though, seems to have been derived by assuming continuous, high-power output (worst-case scenario).

So my question is, assuming that the amp will be driven neither at high power nor continuously (think surround-sound rear channels, etc.) then the lower heat generation should, theoretically, require less overhead clearance for ventilation.

My shelving units have 8" clearances. I can shoehorn my XPA-5 into that shelf, but with less than a half inch clearance above. I plan to mount the amp in that gap, watch a movie, and stick a thermometer into the gap. What's the highest temperature that I should consider "safe" for the long-term viability of the amp's electronics?

Assuming that the temperature is "excessive," (whatever that might be - KeithL ?) is it feasible to use a forced-air fan to compensate for the lack of natural-draft?

Boomzilla

I'll have to check the sticker I made for my Yamaha AVR but after I called them they stated that  the normal operating temp is between 85*f to 95*f if my memory serves me correctly.

[monkumonku]

Jul 10, 2014 10:54:36 GMT -5 pop said:

I prefer to go no underwear with a little powder for full natural-draft. Hope this helps.

Hmm... I suggest adding "TMI" to the list of things you can click on for a particular Lounge post in the upper right hand corner.

[KeithL]

In general, in still air, if you can touch the top plate of the amp without feeling pain, then you're fine (threshold of pain for most people is about 135 degrees F).

Basically, the reason why our amps need good clearance in still air is that we use "convective cooling" - which means that it is the hot air rising from the heat sinks, and going out the top of the amp, that pulls in more cool air. This method is very reliable (and also "automatically" moves more air when the amp is hotter), but it doesn't "push" the air very hard, and so anything that blocks the vents - even a little - can reduce the air flow. Anything that physically pulls air through the amp will work very well to alleviate this problem.

However, here are a few things to keep track of:

1) Air needs to move through the amp. A fan blowing across the top plate will cool the top plate, but do little to cool the heat sinks. Likewise, a fan pulling air away from the top of the amp at the back won't do much if the only place for air to enter is on the top at the front of the amp (the air will simply go over the amp from front to back.) This is why most cabinet fans are arranged so they either pull air out or push it in in such a way that it flows through the equipment. It doesn't take an awful lot of air to keep the amp cool as long as it reaches the heat sinks. (But this is why you need at least some access to multiple vent surfaces - if you try to pull air out the top, yet the bottom and sides are completely blocked, you won't actually get any useful air flow.)

2) Even when playing quietly, our amps generate a small but steady amount of heat. Because of this, even when playing quietly, they will gradually heat up. (So, if you were to totally block the vents, they might remain relatively cool for several minutes, or even hours, but might still eventually overheat. They can also heat up very rapidly if you turn up the volume in that situation.) So, if you're not providing sufficient clearance or forced air cooling, then you should watch the temperature for several hours, and under various conditions, to make sure the temperature remains OK in the longer term.

3) In general, as long as you have "free air flow" of some sort, then the actual clearance is less critical. (In your case, as long as you have some gap - even 1/2 inch - which allows the air from the amp to escape at the top, and a similar gap that allows air to enter the amp at the bottom, and you couple that with a small fan that removes the hot air from that 1/2" gap at the top and keeps it from "piling up", and so ensures that air can continue to flow through the amp, then you should be OK.) Again, note that the air has to move past the heat sinks. (For example, if you were to block the bottom vents, but leave open vents on one side, you could still end up with air entering a side vent and flowing out the top without going past the heat sinks - which would not be good.)

A typical "enclosed installation" might have a narrow (but open) gap at the top, with a thermostatically controlled fan (set for 110 degrees F or so) that exhausts air from that gap out the back of the cabinet, and at least a little clearance around the other surfaces. Note that there has to be a way for fresh, cool air to get in to those other surfaces. Many cabinet installations use one powerful fan to remove air from the cabinet at the rear, plus a series of slot vents to allow fresh incoming air to reach the various pieces of equipment at the front. As long as the fresh cool air has to go through the amp on its way to the exhaust fan, it should be fine. (Even a good, quiet, 4" fan should produce plenty of airflow. A pair of them gives you a backup in case one fails.)

Jul 10, 2014 10:47:48 GMT -5 Boomzilla said:

The majority of Emotiva's amplifiers run pretty cool. The only exception I've found is the XPR-2. The conventional wisdom is that amps need a bare minimum of 0.5 to 1 inch of overhead clearance in a shelving unit to adequately ventilate. Such recommendation, though, seems to have been derived by assuming continuous, high-power output (worst-case scenario).

So my question is, assuming that the amp will be driven neither at high power nor continuously (think surround-sound rear channels, etc.) then the lower heat generation should, theoretically, require less overhead clearance for ventilation.

My shelving units have 8" clearances. I can shoehorn my XPA-5 into that shelf, but with less than a half inch clearance above. I plan to mount the amp in that gap, watch a movie, and stick a thermometer into the gap. What's the highest temperature that I should consider "safe" for the long-term viability of the amp's electronics?

Assuming that the temperature is "excessive," (whatever that might be - KeithL ?) is it feasible to use a forced-air fan to compensate for the lack of natural-draft?

Boomzilla

[Boomzilla]

Thanks, Keith - I appreciate it. I'll do the "finger tip test" and if there's any question, I'll stick a thermometer on it.

The clearance is about 0.3 to 0.4 inches and I've no doubt that if all channels were driven, or if played at louder volumes (or into lower impedances) that the ventilation WOULD be insufficient. In my case, only three of the five channels will be active (center & two rear surrounds), and all of the associated speakers are high impedance and/or high sensitivity.

I'll post my results.