**Fractal Design Celsius S24 Cooler Review : Read more**

- Status
- Not open for further replies.

My only question is the fans. I've loved FD cases, and owned a number, but the "stock" fans that come with those cases have been basically mediocre. While these FD fans appear to be quiet I wonder if we wouldn't see better performance and noise out of something else.

ingtar33 :

My only question is the fans. I've loved FD cases, and owned a number, but the "stock" fans that come with those cases have been basically mediocre. While these FD fans appear to be quiet I wonder if we wouldn't see better performance and noise out of something else.

I suppose if FD must cut costs somewhere, fans are a pretty good place to do it, since they are easily replaceable.

Plausible explanation for the superior cooling achieved with a lower flow rate?

jcwbnimble :

Plausible explanation for the superior cooling achieved with a lower flow rate?

that's plausible, though it would mean the radiators of the other coolers are poor for dispelling heat.

Walt Prill

If this is open loop, does that mean it needs to be maintained like a custom liquid cooling solution (Drained, filled, etc)? Or is it closer to a CLC in the sense it's more "mount and forget"? What's the advantage it has over either solution?

TbsToy :

Walt Prill

There's no marketing gimmick in seeing better numbers and reporting that the numbers are the best. Something tells me you were probably once a good observer of these details but that your observations have more recently turned into a nonsense counter-marketing thing.

Eric did a special cooling project using multiple radiators on a different system. It's a full open loop. Putting all of that hardware into this system would alter the test parameters used to compare the other coolers, invalidating the comparison. But you may be interested in the components he used.

RomeoReject :

If this is open loop, does that mean it needs to be maintained like a custom liquid cooling solution (Drained, filled, etc)? Or is it closer to a CLC in the sense it's more "mount and forget"? What's the advantage it has over either solution?

That seems fundamentally wrong, considering the H240-X2 gives a delta T of 51C while producing 29.8 dBA, and the H220-X produces 34.8 dBA to achieve the same delta T.

Clearly, the H240-X2 is substantially more acoustically efficient.

This also seems to underrate the efficiency of the Fractal. It manages to achieve a lower delta T than any other cooler at max, and that means overcoming the TIM in that CPU. Each additional reduction in temperature requires exponentially more power and airflow to achieve. The more realistic comparison would be to compare cooling power at equal noise levels or comparing noise levels at equal cooling. Anything else will severely distort the data unless the non-linear relationships between fan speed/noise, fan speed/air flow, and air flow/thermal conductivity are accounted for.

the nerd 389 :

That seems fundamentally wrong, considering the H240-X2 gives a delta T of 51C while producing 29.8 dBA, and the H220-X produces 34.8 dBA to achieve the same delta T.

Clearly, the H240-X2 is substantially more acoustically efficient.

This also seems to underrate the efficiency of the Fractal. It manages to achieve a lower delta T than any other cooler at max, and that means overcoming the TIM in that CPU. Each additional reduction in temperature requires exponentially more power and airflow to achieve. The more realistic comparison would be to compare cooling power at equal noise levels or comparing noise levels at equal cooling. Anything else will severely distort the data unless the non-linear relationships between fan speed/noise, fan speed/air flow, and air flow/thermal conductivity are accounted for.

mpampis84 :

Does it perform better than the Kelvin S24 though? Kelvin prices have dropped recently, so is there any point in waiting for Celsius, apart from the integrated fan hub?

Crashman :

the nerd 389 :

That seems fundamentally wrong, considering the H240-X2 gives a delta T of 51C while producing 29.8 dBA, and the H220-X produces 34.8 dBA to achieve the same delta T.

Clearly, the H240-X2 is substantially more acoustically efficient.

This also seems to underrate the efficiency of the Fractal. It manages to achieve a lower delta T than any other cooler at max, and that means overcoming the TIM in that CPU. Each additional reduction in temperature requires exponentially more power and airflow to achieve. The more realistic comparison would be to compare cooling power at equal noise levels or comparing noise levels at equal cooling. Anything else will severely distort the data unless the non-linear relationships between fan speed/noise, fan speed/air flow, and air flow/thermal conductivity are accounted for.

I know how you get the numbers. That's not the issue at all, and it never has been.

The issue is that the numbers are presented as acoustic efficiency, and simply do not reflect the relationship between cooling power and noise output in practice. The end result is that these numbers are often cited to say product A is more acoustically efficient than product B. The problem as I see it is that in many cases, product B will provide equal cooling at a lower noise level.

This is entirely counter intuitive to many readers, and it takes some effort on our part to determine which product will actually give lower noise in any given application. I would greatly appreciate it if I could read a review and know what to expect out of a product. As it is, I have to hunt through the charts to find what the delta T and SPL values are, and then figure out the relationship between them on my own.

the nerd 389 :

I know how you get the numbers. That's not the issue at all, and it never has been.

The issue is that the numbers are presented as acoustic efficiency, and simply do not reflect the relationship between cooling power and noise output in practice. The end result is that these numbers are often cited to say product A is more acoustically efficient than product B. The problem as I see it is that in many cases, product B will provide equal cooling at a lower noise level.

This is entirely counter intuitive to many readers, and it takes some effort on our part to determine which product will actually give lower noise in any given application. I would greatly appreciate it if I could read a review and know what to expect out of a product. As it is, I have to hunt through the charts to find what the delta T and SPL values are, and then figure out the relationship between them on my own.

The issue is that the numbers are presented as acoustic efficiency, and simply do not reflect the relationship between cooling power and noise output in practice. The end result is that these numbers are often cited to say product A is more acoustically efficient than product B. The problem as I see it is that in many cases, product B will provide equal cooling at a lower noise level.

This is entirely counter intuitive to many readers, and it takes some effort on our part to determine which product will actually give lower noise in any given application. I would greatly appreciate it if I could read a review and know what to expect out of a product. As it is, I have to hunt through the charts to find what the delta T and SPL values are, and then figure out the relationship between them on my own.

We get the same feedback occasionally when a system that uses 100W to produce 100 work units is rated less efficient than one that uses 150W to produce 200 work units. "The 100W unit [must] be more efficient because it uses less power". Nah, it's just more miserly.

Crashman :

the nerd 389 :

The issue is that the numbers are presented as acoustic efficiency, and simply do not reflect the relationship between cooling power and noise output in practice. The end result is that these numbers are often cited to say product A is more acoustically efficient than product B. The problem as I see it is that in many cases, product B will provide equal cooling at a lower noise level.

This is entirely counter intuitive to many readers, and it takes some effort on our part to determine which product will actually give lower noise in any given application. I would greatly appreciate it if I could read a review and know what to expect out of a product. As it is, I have to hunt through the charts to find what the delta T and SPL values are, and then figure out the relationship between them on my own.

We get the same feedback occasionally when a system that uses 100W to produce 100 work units is rated less efficient than one that uses 150W to produce 200 work units. "The 100W unit [must] be more efficient because it uses less power". Nah, it's just more miserly.

I understand the logic behind that. Unfortunately, acoustics rarely works like that. The units for, say, a motor's efficiency are based on two similar units, namely mechanical vs electrical watts. Since any decibel value is a unitless ratio, you can't simply use it like you would other units.

Acoustic efficiency of a fan (and yes, there is an official definition) is very different. Because the noise level produced by a specific fan scales with 10*log( RPM^5), airflow scales with RPM, and heat transfer scales with e^(-k*cfm) you cannot simply look at the difference in cooling vs the difference in noise. I can't even begin to cover all of the places where the math simply does not work.

The official definition of acoustic efficiency is actually a simple dB offset that's added into the fan noise prediction equations, and is defined in terms of RPM, not delta T. No where will you find a dB/watt unit, a dB/C unit, or a dB/RPM unit in the field of acoustics. The closest you actually see is dB (SPL) - dB (watts). That's a minus, not a division. For fans, this comes into play as a specific 50*log(RPM1/RPM2) term in the noise equations.

Mind you, there's still the exponential decay involved with the amount of cooling a fin array can give you with increasing airflow. That's probably the most annoying factor to account for due to modern heatsinks inducing turbulence as a means of increasing heat transfer. I'm unfortunately not in a position that I could test that, but TH reviewers might be. I understand the time limitations you guys face, though. I don't know of an efficient way to measure that off the top of my head, so it probably isn't practical to implement a measurement method without further research.

I'd be happy to link in some reference material for you to go over if you're interested. I have some documents that may be worth going through, as they outline the key parameters used to describe fans in terms of acoustics. They're far more concise and understandable than I can hope to be.

Minor Update:

I feel like it's worth mentioning that I wouldn't bother the reviewers at TH with this if I hadn't gone through and triple checked both the methods that I'm suggesting and the methods currently used in the reviews. I don't care to waste anyone's time on trivialities or even minor errors. I only bring this up because it presents significant issues when selecting products, and can easily lead consumers to purchase products that are not what they want/need.

the nerd 389 :

Crashman :

It's the actual measurement of how much cooling you get per unit of noise. Or how much noise you get per unit of cooling. Actually it's both of those. It's like measuring how many work units you get per unit of electricity...so yes...a system that produces twice the data while using the same energy is twice as efficient, same deal using acoustical energy instead of electrical energy...

We get the same feedback occasionally when a system that uses 100W to produce 100 work units is rated less efficient than one that uses 150W to produce 200 work units. "The 100W unit [must] be more efficient because it uses less power". Nah, it's just more miserly.

We get the same feedback occasionally when a system that uses 100W to produce 100 work units is rated less efficient than one that uses 150W to produce 200 work units. "The 100W unit [must] be more efficient because it uses less power". Nah, it's just more miserly.

I understand the logic behind that. Unfortunately, acoustics rarely works like that. The units for, say, a motor's efficiency are based on two similar units, namely mechanical vs electrical watts. Since any decibel value is a unitless ratio, you can't simply use it like you would other units.

Acoustic efficiency of a fan (and yes, there is an official definition) is very different. Because the noise level produced by a specific fan scales with 10*log( RPM^5), airflow scales with RPM, and heat transfer scales with e^(-k*cfm) you cannot simply look at the difference in cooling vs the difference in noise. I can't even begin to cover all of the places where the math simply does not work.

The simplest way to convert dB to a linear scale is 10^(dB/10) if you're interested in energy content, and 10^(dB/20) if you're interested in some physical quantity like pressure. This still won't correct for the fifth order relationship with RPM or the exponential relationship between that and delta T. There's also the constant k that needs to be taken into account, and that varies based on the construction of a cooler. I'll have to sit down with the math to be sure, but there should be a way to derive it from either two or, preferably, three measurements of delta T and the corresponding SPL.

I'll see if I can put a formula together. I usually use either C# or VBA to make that sort of operation legible and easy to work with when dealing with this sort of thing at work. Otherwise, the formulas get rather cumbersome very quickly. If that isn't acceptable, I can write the entire thing out in a single formula.

If you'd like, I can also throw in a term to correct for the thermal interface material used in Intel CPUs. Currently, I can only make a reasonable estimate of the i7-7700k, and that's +/-20%. You guys probably have enough data to derive it with much greater accuracy than I do. You also probably have enough data to get the numbers for other processors and product lines.

I just have one question, though. Do you want the formula/code to be backwards compatible with the data you've gathered in previous reviews? If so, it may take some time to put together, even for me.

the nerd 389 :

The simplest way to convert dB to a linear scale is 10^(dB/10) if you're interested in energy content, and 10^(dB/20) if you're interested in some physical quantity like pressure. This still won't correct for the fifth order relationship with RPM or the exponential relationship between that and delta T. There's also the constant k that needs to be taken into account, and that varies based on the construction of a cooler. I'll have to sit down with the math to be sure, but there should be a way to derive it from either two or, preferably, three measurements of delta T and the corresponding SPL.

I'll see if I can put a formula together. I usually use either C# or VBA to make that sort of operation legible and easy to work with when dealing with this sort of thing at work. Otherwise, the formulas get rather cumbersome very quickly. If that isn't acceptable, I can write the entire thing out in a single formula.

If you'd like, I can also throw in a term to correct for the thermal interface material used in Intel CPUs. Currently, I can only make a reasonable estimate of the i7-7700k, and that's +/-20%. You guys probably have enough data to derive it with much greater accuracy than I do. You also probably have enough data to get the numbers for other processors and product lines.

I just have one question, though. Do you want the formula/code to be backwards compatible with the data you've gathered in previous reviews? If so, it may take some time to put together, even for me.

The original sheet takes two averages for the two measurements (high and low) of all coolers, then divides that result by the single result to generate a percent scale inverse to the temperature (ie, 12% less heat than the group average of 100% gives it a rating of 112%). The division works the other way in the noise measurement, because that number is going on the bottom of the cooling-to-noise equation (ie, 12% more noise than average is 112%). And then the temperature % is divided by the noise % to get a cooling-to-noise ratio without the logorithmic scaling on the noise ratio. And then the average is zero'd out by subtracting 1 from the result and putting the -1 data on the chart. So, I think we'd need to go up to the middle, where the individual noise measurement is divided by the average for the group, in order to add the logorithmic to linear scale correction.

If I do that, I should be able to make the entire thing independent of the other coolers in the review. That's one less issue for the reviewers to worry about, no?

the nerd 389 :

If I do that, I should be able to make the entire thing independent of the other coolers in the review. That's one less issue for the reviewers to worry about, no?

jcwbnimble :

Could this cooler's lower l/h design be giving it the advantage compared to these other expandable coolers? By that I mean, with a lower flow, the coolant has more time to release it's heat in the radiator before returning to the CPU block.

You're correct that the coolant has more time to dump heat to the air, but:

a) it will do so in a less efficient manner, since the average temperature gradient between coolant and air will be lower, and

b) the coolant will also heat up more while staying longer at the cooling block.

In reality there's a threshold flow level above which the cooling doesn't become significantly mor efficient, but below that level any change is clearly noticed.

the nerd 389 :

The simplest way to convert dB to a linear scale ... still won't correct for the fifth order relationship with RPM or the exponential relationship between that and delta T. There's also the constant k that needs to be taken into account, and that varies based on the construction of a cooler.

The design is obviously fixed and measurements are done with the fans at full and half speed.

My only gripe is that the presented noise level doesn't have the background noise removed. (Delta noise instead of absolute noise.)

The way to calculate actual noise from the fan (N [dB(A)]) given background noise (B) and measured noise with fan (M) is N = 10*log(10^(M/10) - 10^(B/10))

Note: N ≈ M if M > B+5

Olle P :

the nerd 389 :

The design is obviously fixed and measurements are done with the fans at full and half speed.

My only gripe is that the presented noise level doesn't have the background noise removed. (Delta noise instead of absolute noise.)

The way to calculate actual noise from the fan (N [dB(A)]) given background noise (B) and measured noise with fan (M) is N = 10*log(10^(M/10) - 10^(B/10))

Note: N ≈ M if M > B+5

Check out the H240 X2 review, and look at the values for the X61 vs the H240 X2. The X61 clearly outperforms the H240 X2 in terms of noise levels at a given temperature, but due to the way the numbers are crunched, they conclude that the H240 X2 has better acoustic efficiency.

Also, they perform measurements, to my knowledge, with ambient levels around 20 dBA on the meter. With their meter, that's not real noise. It's the noise floor of the meter. It would be corrected for using that equation, though.

Crashman :

the nerd 389 :

If I do that, I should be able to make the entire thing independent of the other coolers in the review. That's one less issue for the reviewers to worry about, no?

The issue with acoustic efficiency is that you can actually have a cooler that produces no additional noise (other than the brownian noise associated with heated particles, roughly -24 dB at ambient temperatures), but can still cool something to below ambient. That will break anything that treats it as an efficiency value.

It's called an absorption refrigerator, and to my knowledge, there is one company that does use them in computers. In that case, they only used the heat generated by the computer to power the refrigerator, so it didn't drop below ambient.

Here's a video where they go over that machine:

https://www.youtube.com/watch?v=9PJOrfpiVwE

Crashman :

RomeoReject :

If this is open loop, does that mean it needs to be maintained like a custom liquid cooling solution (Drained, filled, etc)? Or is it closer to a CLC in the sense it's more "mount and forget"? What's the advantage it has over either solution?

Ah, okie dokie. Appreciate it.

So, if someone opens it up to expand something, from that point forward it will forever require maintenance, but until that line is crossed, it's hands-off? Would that apply to the QDC stuff from EK as well (Given that it doesn't expose the fluids at all)?

RomeoReject :

Crashman :

RomeoReject :

If this is open loop, does that mean it needs to be maintained like a custom liquid cooling solution (Drained, filled, etc)? Or is it closer to a CLC in the sense it's more "mount and forget"? What's the advantage it has over either solution?

Ah, okie dokie. Appreciate it.

So, if someone opens it up to expand something, from that point forward it will forever require maintenance, but until that line is crossed, it's hands-off? Would that apply to the QDC stuff from EK as well (Given that it doesn't expose the fluids at all)?

- Status
- Not open for further replies.