I didn't say nothing else matters. I said those things were minor in comparison.
Could you explain exactly what is wrong with my statement? I don't see any use for any of the computer overclocker things in audio power amps.
The article you linked to is not about axial air flow, therefore it has little relevance to blowing/sucking fans.
It merely illustrates that if air flow direction is converged by 90 degrees or more, that becomes the dominant factor (and consequently leads to wrong conclusions)
Airflow does not increase, it decreases from the inlet side to the outlet side. The difference is the efficiency figure of the fan (I do know I said equal, it is not equal but never said that it increases).
Static pressure increases at the outlet side. because of smaller radiated 'pattern' of airflow. I should have said this is specific to most PC fans, specially for cases and heatsinks. This is because they are almost always pushing against an obstacle and hence the blade designs usually (not always) are optimised for higher static pressure up to a point. This is usually done by aiming for a small and controlled exhaust pattern.
The design of the fan will always trade off static pressure for airflow and vice versa, depending on application. And yes, airflow will always decrease from inlet to outlet. Pressure however, that can be controlled.
Watercooling e.g. enables one to construct a power output stage that is physically impossible with passive cooling.
There's also the matter of temperature differences,the larger the heatsink, the greater the difference.
In a practical sense, power devices will not be spread out over a vast distance.
There's also a limit to the number of output devices, engineering is always about trade-offs.
I agree with that, but I don't see any audio performance advantages in any of these physically impossible forms. For example, you can buy an air cooled UHF TV transmitter with 4750W power output: R&STMU9 UHF Transmitter Family for TV - Models - Rohde & Schwarz United Kingdom
You might argue that as an audio power output stage gets physically bigger, the stray inductances and capacitances get bigger too, and it will eventually get too slow for low distortion at high frequencies. To which I say that you just do what Rohde & Schwarz did in their TV transmitter, make several smaller amplifier modules and combine their outputs.
(On the other hand, you might notice that R&S offer a 30kW water cooled transmitter in the same footprint as the 5kW air cooled one.)
Very true, but not very 'audiophile', guv.
£ to lb, active fan and/or water cooling is unbeatable nowadays (imo).
Current day fans are much more silent compared to pre-2k stuff, and at a fraction of the cost.
Pus all the hardware is easily available, heat plates, ducted heatsink assemblies, the works.
The most disillusioned, my fellow naval architect neighbor drinks more Scotch whisky than his mind can forget.
(sniffing crude oil in Aberdeen for years on end may have contributed)
If you look at pictures of Amplifiers, you will find the heat sinks are mounted in various ways. Inside-outside, Vertical-horizontal, Simple plates to Assembled pipes and chimneys, and what not. Each case is different for cooling purposes. Each suggestion in this thread is correct for one of the cases. You choose your method. There is no single solution for all.
They are not the same in so far as you often want to get the hot air coming off the heatsink out of the case immediately, without giving it the chance to heat up everything else inside the case.
Internal fanned heatsinks should make use of the fan source.
That means tunneling and no leaks.
Ventilation of warmed or hot air to reduce the risks of overheating the other components is a completely separate issue. This separate issue can be solved by passive, or fanned ventilation.
Clever use of one fan with a divergent outlet, part to the heatsink tunnel and part to "other ventilation" would certainly save money in production costs.
There was a very clever use of a passive ventilation system many years ago on this Forum.
Cold air was drawn in through the side/s over a warm area and then the chimneys above the main heatsink drew both that warmed air and other "leaks" into the chassis and then up the chimneys to cool the main sinks.
This could be copied with a "sucking" fan !
That means tunneling and no leaks.
Ventilation of warmed or hot air to reduce the risks of overheating the other components is a completely separate issue. This separate issue can be solved by passive, or fanned ventilation.
Clever use of one fan with a divergent outlet, part to the heatsink tunnel and part to "other ventilation" would certainly save money in production costs.
There was a very clever use of a passive ventilation system many years ago on this Forum.
Cold air was drawn in through the side/s over a warm area and then the chimneys above the main heatsink drew both that warmed air and other "leaks" into the chassis and then up the chimneys to cool the main sinks.
This could be copied with a "sucking" fan !
The efficiency of a heatsink is determined by the temperature difference between the heatsink and ambient.
Mounted inside a case, temperature of the ambient air will be higher, but the one of the heatsink will be too by the same difference.
Manufacturers test their heatsinks, by measuring the number of watts to obtain a given temperature difference.
Advantage of that approach is that it does not require a temperature controlled environment for the test.
(makes the rating of a heatsink actually dW/dT, at a set ΔT between heatsink and ambient.)
That was supposed to be my first question: which application you need the active cooling for?
Passive cooling, where calculated and designed well, should serve the purpose well. Active cooling can be applied as a measure against overheating, not as temperature regulation, as a fan and simple trigger circuit set to a limit temperature.
this arose from rebuilding an old EV amp that i have had in the "pile" for a long time but it was more of a general question as over the years i'd heard a good many viewpoints on the subject and wanted to verify if some of the rhetoric had a basis in fact or that any specific or general approach was better.
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