Posts Tagged ‘MCP-35X’

Welcome to my very first standardized round of pump noise tests in my continued pursuit of silence (The primary reason I water-cool).  This round will be much more controlled with an emphasis on consistency between pump tests.  Anything with the pump noise Round 1 will have the same test conditions.  Pump noise is normally not a concern for folks with higher speed fans or for installs where the pump is allowed to float freely avoiding vibration transfer.  However,  solid mounts and/or when users begin dipping below the 1000 RPM level are conditions where pump noise can become the primary noise annoyance.  This testing effort is looking at a variety of DDC/D5 series pumps in various flavors and tops measure dbA relatively to flow rate on a low restriction loop.

I want to give a huge thanks to my many sponsors.  Tim at, Gabe at, bmaverick, and have all sponsored in some way.  Without their generosity this test would not have been possible.   Tim from sponsored most of the items in this test including the pump controllers used on voltage regulated pumps.  Thanks!!!

Test Conditions

Test Setup, sorry for the poor phone picture, camera in use.:)

This round will use a low restriction CPU block only type loop that includes the Danger Den MC-TDX, XSPC RS120 radiator, King Instruments Flow meter, 1/2″ tubing, and a custom 3″ ABS reservoir with 5/8″ fittings.  The loop also contains some very low restriction brass globe valves for easier swapping between pumps.  I chose a low restriction loop for this round so I could get a greater number of data points. I may later attempt the same for a more restrictive loop although you could cross correlate with RPM values to PQ pump curves if desired as well.  Some noise is actually generated at the restriction points (blocks) as well, but this will be a good relative test between pumps.

I am also testing in two decoupling scenarios.  The first is a near ideal soft foam free floating type test, the second is direct metal contact.  This gives you sort of a worst/best range of noise.  In my earlier testing I found that thinner foam neoprene would fall somewhere in the middle.  Other options such as rubber washers/grommets would also fall in between and likely a bit more toward the worst case condition.  This best/worst case should give you a sense of possible noise range which is fairly dramatic in most instances.  This will also likely emphasize the importance behind decoupling pumps.

For relative scale, I’m including approximate noise level tests from my Gentle Typhoon fan on the left from my fan/radiator round 6 based testing here.  It was tested at roughly the same distance so I thought it would give some sense of scale to the charts.

Laing DDC-1 + XSPC top

This is the old model DDC-1 pump rated at 10 w and manufactured in 2003.

I think noise level is subjectively higher than average due to a buzz type noise present, but the pump is fairly consistent with very little issue with harmonic spikes even without decoupling.  Fully decoupled at 12V it measures roughly the same noise level as a GT-15 at around 1400RPM.  Noise scales well with voltage and at lower volts is approaching the 940RPM fan mark.  A good performer for it’s age, but not quite as silent as the newer models.

Koolance PMP-400 (DDC3.25) + Koolance COV-RP400 Top

This is the latest PMP-400 pump (18 watt) flavor with a nice thick/heavy acetal constructed top from Koolance.  Being acetal and extra thick, this top will likely provide some improvement to the thin and hard factory top material.

The pump/top combo does very well when completely decoupled.  Even at the extremely strong 12+V mark it’s just a hair more noise than a GT15 at around 1,000 RPM, that’s excellent!  You should however noticed there are two harmonic bumps that may or may not be associated with the simulated test rig.  The metal contact test however was all over the place with harmonics causing increased noise over the decoupled test from 3 dbA to  15 dbA.  This pump & top combo really likes to be decoupled completely if possible, the trick is likely some sort of lift or UN bracket system that will allow cooling and vibration decoupling.

Swiftech MCP-35X

This is the new PWM “Smart Pump” by Swiftech.  One obvious difference is the much larger operating range over voltage control of similar non PWM pumps.

Results are also similarly good when fully decoupled as the Koolance PMP-400 with some slightly higher numbers in some areas by 1-2 dbA.  It does have an extended range and the PWM feature could potentially be scaled dynamically, so those are all details to consider as well.  Overall a good showing that also like to be decoupled for best noise results.  Solid mounting can result in anywhere from 1 to 10 dbA more noise than a really well decoupled installation.  Of course being a DDC series high performance pump, you also may want to consider lifting the pump off the base to provide cooling and decoupling

Koolance PMP-450 (D5 Vario) + COV-RP450 Top

Well how does our larger vario pump model with factory speed controller work, these have generally been popular by the noiseless priority folks as they are factory built with a manual speed controller.  This first test is with the Koolance COV-RP450 top which is somewhat unique in that it includes an aluminum casing for the pump motor.  This serves to mount the pumps, but also to clean up the visual.  In addition, I suspect this help mask motor noises as well…  Let’s take a look:

Decoupled the Koolance PMP-450 with Koolance COV-RP450 top is the top performer, only hitting around 33 dbA at full speed, very good! However, similar to the other pumps when not decoupled, the noise levels climb significantly as RPMs increase creating up to 13dbA more noise than the fully decoupled test.

Koolance PMP-450 (D5 Vario) Sample #2 Stock Top

This is a second sample pump I had hand and initially decided to test it simply because I still had the factory top on it.  My intent was to compare stock top vs aftermarket top, but it turns out I also found some significant sample variance over the first sample.  This pumps had some rather pronounced spikes in noise level in a few places.

Overall this pump sample did good at middle speeds, but had higher than average noise levels at slow and high which I suspect is an impeller that’s slightly out of balance.  Sample variance is obviously a big factor in results so far and is going to make solid conclusions difficult with the low sample quantity being tested.

Koolance PMP-450S (D5 Strong)

The new king of power on the test bench…running with the factory top which it seems to like the best.

The Koolance PMP-450S strong did well, particularly under 14 V with the exception of a blip at 3800 RPM. Very good pump for noise and power.

Laing DDC 3.2

I’ve had this pump for a while, these are the last generation Laing DDC 3.2 series which is being replaced by the DDC 3.25 model.  This one also has the base “Feet” and a solid blue impeller.

This pump did very well and similar to the Koolance DDC 3.25 and only measuring about 1 dbA (less than perceivable noise difference) at full speed.  The thicker Koolance acetal top again seems to help reduce noise levels of the DDC series pumps.  It keeps noise at similar levels to an extremely silent GT fan at 1000RPM which is very good when decoupled.  Loosing the foam decoupler however reveals a similar erratic and harmonic variable results up to 9 dbA higher than the decoupled test.   I’m starting to sound like a broken record here, but decoupling is everything when it comes to pump noise reduction.

Summary Comparison Charts

Noise vs. Low Restriction Loop Flow Rate

First, lets look at the “Best Case” scenario where the pump is completely floating freely on a thick piece of foam.  Note, DDC series pumps should have a stand to allow base heat dissipation.

At the 2.3 GPM mark there are many pumps within about a 2dbA (not perceptible) grouping.  The Koolance PMP-450 with COV-RP450 top having a very slight (and perhaps testing error) edge in the charts.  The Koolance PMP-400 + COV-RP400, Swiftech MCP-35X, and Koolance PMP-450S are all similarly good here as well.  The PMP-450 sample 2 for some reason (suspect sample variance/impeller balance), was slightly higher.  The DDC-1 was also a bit more noisy.

All of the pumps were of good noise level though, and generally when decoupled were producing under the GT-15 noise level at around 1500 RPM.  If you had 10 each 40 dbA fans running in the background that total is 50 dbA, so it doesn’t take a whole bunch of fan noise to quickly mask pump noise “WHEN” the pump is properly decoupled.

So…what happens when you have a worst case mount, direct metal to pump contact….

All bets are off….There is really no consistency other than the general lack of consistency and general rise in noise level.  There are some things to learn here though, the bumps and dips are scattered throughout which means the vibration frequency and speed can be potentially “Tuned” to hit a low point.  If you have a solid mounted or less than desirable pump mount that is causing noise problems, you should seriously consider turning it down/up to see if you can find a low point in the noise curve.  Each case and each installation will likely have a unique harmonic noise/rpm profile/pattern, you just need to find the right pump speed to fall on the dips or low points.


  • Pump decoupling has HUGE benefits, up to 15 dbA lower noise levels than pumps without decoupling.
  • Pumps without decoupling are erratic in noise with massive peaks and valleys in noise level throughout the RPM range.
  • Thick Acetal pump tops may provide some benefit to reduction in noise levels over thin factory pump tops.
  • Pump sample variance does also affect noise levels, this may be due to how balanced the impeller is. Luck of the draw.
  • PWM pumps such as the Swiftech MCP-35X provide much more control and RPM range than voltage control.  They also provide the ability to dynamically increase decrease pump speed on thermal needs.
  • In general, all of these pumps are extremely silent pumps when decoupled.  Most general users with fans over 1000 RPM would typically have a hard time hearing these pumps at all in a normal fan noise masking environment.  Critical noise folks using ultra slow speed fans should put extra emphasis into pump decoupling methods and undervolting or reducing pump speeds.

Bottom line, if you want an extremely quiet pump, work on completely decoupling it from your case and consider tuning speed to seek the low points along the noise profile.  I would also highly recommend using pumps with PWM or fan controllers with thermal throttling capabilities to dial these pumps up and down with load.  Dynamic pump speed reduction setups allow for both ultra silence AND peak power when needed.



Swiftech MCP-35X & Reservoir

Posted: February 25, 2011 in Pumps
Tags: , , , , ,


Welcome to my Swiftech MCP-35X review, the latest in the extremely popular Laing DDC pumps. This latest incarnation just got smarter with PWM technology and has several factory high performance features included within. I want to give a special thanks to Gabe from Swiftech for sponsoring this pump.

If you have been watercooling for long, you’ll likely recognize this family of pumps that have many names and variations over the course of years in refinement. The Laing DDC series has been through various revisions from the DDC 1, DDC 2, and over the last view years the DDC 3.1 and DDC 3.2 being offered in two power flavors. The current common models would be the DDC 3.15(MCP 350) and DDC 3.25(MCP 355 or PMP400). They are exceptional and popular pumps because they are tuned for high pressure applications and carry a wallop of power in such as small package.

A common “Missing Refinement” of the “non 35X” pumps is that they typically come with a factory top that uses plastic 3/8″ barbs. The factory top typically comes with a sharp elbow at the pump inlet (which is poor in efficiency). Sooo..most water cooling enthusiasts have had a desire to use their own fittings which requires replacing the factory top with something after market. This provides users with standard G1/4 threading, improved looks, and higher performance. Unfortunately, removal of the factory top typically means you also forfeit the warranty.


It is very clear that switching out the stock pump top to an aftermarket top increases pumping power, but what many fail to recognize is it also increases current draw and pump heat. This in itself puts more stress on the pump motor and causes more heat buildup. Sort of like putting a turbo on your factory high performance car or truck, you exceed specifications and increase wear and tear. I also believe a large portion of pump failures are due to leaks by incorrect top installation. I myself have managed to flood out two different DDC pumps by incorrectly tightening the tops on (it happens). The way the pump motor sits on top of and inside the exterior shell, if the o-ring leaks, water will work it’s way down into the PCB area first. Leaking water will eventually fill up the bottom case and start spilling out of the holes in the bottom, but many times not until the PCB is completely under water. Anyhow, we’re only human and we will and do mess up. The manufacturers know this and you forgo your warranty privileges once the factory top is removed. I believe some of the newer packages will even start coming with a warranty void if removed type sticker, but my particular sample did not.


That’s where things start looking really good for this new 35X pump. It comes factory with a quality pump top that is already installed and ready to go. No need to remove the stock top and void any warranty, just plug it in, screw on your desired barbs and go. You get factory and warranty protected high performance right out of the box.

The top contains several new and/or improved features that are worthy of design/efficiency note. Of most importance is the spiral shaped volute. Not the best picture here, but the radius and space between the impeller and wall is continuously increasing. In addition the wall was cut with a radius bit which should help further reduce friction at this critical location. The top is also similar to the stock top in that there are centering feet to ensure proper inlet centering on the impeller. In addition the outlet port was specifically oriented in line or in plane with the impeller for a perfectly tangential alignment with the impeller (most of the current tops have a slight bend). This help keep the impeller running flat. And the best I’ve seen in matching the spiral volute to the exit port, the drilled hole lines up perfectly with the radius milled volute.

But the features and details of the volute are very clear that high performance was at the top of the priority list. I’ll include more on performance later..


This is the first I have seen of PWM pump control in the history of watercooling which offers you the ability to control pump speed either manually or automatically via MB core temperature. Prior to this pump, variable speed control was reserved to either voltage regulation, or buying the D5 vario (MCP655). Now you have that option here too. Furthermore, PWM offers a broader range of speed control AND more importantly and safe minimum and maximum speed. With voltage control, you have a fairly narrow and unforgiving window. Under about 7V OR over 13V and the pump will NOT start. If you hook any ordinary pump to a fan controller only to have accidentally bumped a control knob, that could leave you with a pumps sitting there and zero flow. It wont take long for the water in the CPU block to start boiling which eventually will lead to deforming and bursting of tubing nearby (I’ve almost done this myself).

Well, no worries using PWM control, if connected to a molex and you set the PWM via MB controls, the pump will always start no matter what the PWM setting. Even disconnecting the PWM signal wire, the pump will simply default to 100% pumping power. PWM control means several things:

  • Wide RPM speed control (DDC Vario)
  • Safe Speed Control (Pump will always start)
  • More Low RPM range than Voltage Control
  • Ability to scale pump speed with CPU temperature (On Demand)
  • No extra controller necessary, typically possible via MB and MB related software (Free smart controls)

For PWM control, you will ideally have controls on your motherboard, but the level of control will depend on software and the motherboard used. For example, my older DFI board from a few years back can only set one temperature point on the CPU fan, and the motherboard ramp up down is fixed. However on my son’s newer Gigabyte MB and using EasyTune 6, I had full control over PWM from 10% up to 90% in 1% increments. This is what I used to run my tests as it turns out measuring duty cycle at higher frequencies is reserved for those who own a scope. My multimeter in Duty mode is simply incapable of measuring. With that said, I must put a large grain of salt on my PWM factor and suspect it may be off by as much as 10%. The performance PQ results are good, but the PWM Duty may be off a bit due to only having the MB software to go by.

Here are my PWM vs RPM scaling results. I increased PWM value from 10% to 60% in 10% increments and pulled RPM maximum values from those test to plot out the following chart.

And here you can see the PWM wires and PCB. At the surface level the PCB looks identical to that of the DDC3.25, but what hides within is a very different motor. Don’t assume you can simply solder in a green wire on a DDC3.25 and create a 35X motor, it doesn’t work.


It comes as no surprise to me when I opened the boxes that it was yet again a very complete accessory package, Swiftech is always very generous in the accessories. The package comes with:

  • 35X Pump Motor/35X Performance Top Assembled
  • Swiftech 1/2″ Highflow Barbs
  • Swiftech Clamps
  • Vibration (Noise Reduction)Neoprene Double Sided Sticky Pad
  • Corse threaded screws for solid mounting
  • 3 Page User Manual

The user manual is very well written and complete, it should be easy to follow for most users.

Overall an excellent and complete pump package with accessories above and beyond the factory package. It really is everything you need plus some..


To compliment the pump, there is an accessory option you can buy in the form of a combo reservoir unit that mounts directly to the pump top. In general I have found that combining a pump + reservoir is a good thing for pump performance as you generally eliminate extra connections plus tubing that creates additional restriction. The reservoir installation was a little different in that you have to install a little orientation pin that fixes the barb orientation relative to the base. Then you have to carefully place a sealing o-ring in place on the top. Next you set the reservoir on the o-ring and on the pin, and finally you get to use a long large flathead screwdriver to tighten the retention base fitting. I did this several times and each time went without a hitch although it was a little bit interesting.

After that is done you install a wire mesh and sponge over the inlet port on bottom. I presume the wire mesh is there to prevent any sponge or other material from accidentally getting into the impeller blades. The combo unit looks like this which is a nice compact unit only measuring roughly 5.5″ tall.

All fitted and ready for action!

Although I should note that I was not able to fit a 3/4″OD compression barb in the upper side inlet hole. The flat spot molded into the side was about 1mm too low and impacted the barb edge. I believe this was just a fluke in my particular sample, the holes were just drilled/tapped slightly too high. This could be fixed easy enough with a little dremel work, but I don’t have plans to use compression fittings so I didn’t bother.

The sponge systems allows you to utilize the side ports for one or two inlets. Depending on how you setup the system. I tested the sponge system with the lower inlet port.

But as a side experiment, I also tried creating my own top inlet/downtube setup which actually worked better both for bleeding and for performance. I simply screwed in another barb in the bottom of the top cover and cut off about a 3″ piece of tubing and tried to center the bottom part of the tube to line up with the pump inlet. Ideally you could also use some clear 1/2″ acrylic tube or something a bit more rigid/straight.

The system is very modular for inlet options.


In case you wanted the fine print details, here are the charts for pump only (no reservoir) for 10% through 60% in 10% increments as well as 100%. I’ll thumb these out below. This actually took a fair amount of time, but considering I’ve never tested anything with PWM control, I wanted to get some experience with it and did full 10% incremental tests.

And the summary Chart of those results:

Generally I think 30% is about the minimum you would want to go with even a low restriction loop (1GPM or better), and the majority of the speed change occurs between 10% and 50-60%. My 60% and 100% run came out about the same which is probably due to my PWM software and/or motherboard not being very precise. The PWM frequency is too high to allow multimeter measurement of duty cycle, so I could only go by what Easy Tune told me which appears to be approximate at best.

One thing to note about the summary chart, I also included approximate voltages that equaled the same RPM, but since the pump startup minimum is around 7V, I was not able to duplicate the lower PWM speeds.

PWM provides more low speed options than analog voltage control.


If you sit down and think about the likely purchase scenario’s for a DDC pump/top combo, it might look something like this:

Option A would be the Swiftech MCP35X with factory performance top.

Option B would be some version of the DDC3.25 such as the MCP355 or PMP-400 and you would add a performance aftermarket top of your choosing.

To compare these two options I selected the XSPC top as it was my top performing standalone top from my pump top shootout some time ago. I compared it directly on the same motor as the MCP35X and it performed equally as well. So the following comparison is more about pump motors than it is tops:

The 35X option has a decent performance advantage, moreso than most top differences. A low restriction loop may see about .2GPM or 10% improvement to flow rate over the DDC3.25+top alternative, and ultra high restriction loop will be approximately the same. An average system would see about 5% more flow rate.

So if the tops perform about the same, why does the 35X perform better you might ask?

The answer is RPM limiter programming, which is fairly obvious in the following chart:

The RPM limiter programming in the DDC3.25 is much more aggressive leaving the DDC35X to have a simple RPM advantage particularly with lower restriction scenarios. Note that this does come at some expense in power consumption though and possibly some increase in pump heat.

Regardless, the performance is simply hard to touch with that RPM advantage and as far as I know, the only way to get the 35X pump motor is to buy a 35X pump. And considering you get everything in one package with a backing 24 month warranty, that’s a good thing!


Along with any reservoir, you’ll want to know at least something about it’s ability to bleed air out of a system and how the performance of that reservoir compares to the stock top.

I tested the factory screen/sponge system with side inlet, pump alone, pump plus separated reservoir, and top downtube alternative.

Regarding bleeding performance, the sponge system worked ok for flow rates below 1.5GPM, but above 1.5GPM the inlet flow disturbance was enough that the surface water was fairly disturbed and I was getting air sucking back down the pump at the 2+GPM mark. This could be mitigated by simply turning the pump down a bit, but it should be noted.

With the sponge not working as well as I hoped, I set out to look at the alternatives. I found that the reservoir works perfectly using a top down inlet plus down tube configuration. This is extremely easy to build, all you need is an extra barb and about 3″ of tubing. Even better would be some sort of clear rigid tube, you just need something to protrude down through the surface of the water in the reservoir and point at the pump inlet. I tested with a piece of 1/2″ x 3/4″ tubing as I assumed that would be readily available by most users.

Here are the performance test results comparing the various reservoir alternatives tried:

While we are splitting hairs a bit here, I did measure a slight performance advantage to using the combined reservoir vs separated reservoir. This makes sense because you have one less fitting plus less tubing loss, etc. I also found the top down inlet tube idea to be superior to the sponge system in performance. But the key benefit to the top down tube is very still surface water clear out to 3GPM and more. It’s also more resistant to varied fill height levels.

I would recommend the TOP INLET INTERNAL TUBE ALTERNATIVE, it works the best in my tinkering experience both for bleeding and for performance


For those that haven’t used a DDC series pump motor, you should be aware they get hot on their base and the 35X is no different in that regard. I measured up to 55C in a 21C ambient which feels toasty to the touch. Many users of these pump go to an extra level of effort to provide some air flow over the base of the unit to mitigate that heat and while I’m not sure it’s necessary, I can’t imagine it hurts. I’ve run serveral DDC pumps, some with air flow, some without and never had any failure type problem. In this case, the pump motor and pump top were designed together and warrantied together, so I wouldn’t let heat bother you. Just don’t be surprised that they get hot to the touch.

Many people know this, but efficiency is also very important in water cooling. You want the least amount of heat transfered to the water as possible for maximum cooling. Many might think that the pump heat would not matter because it is too small. While it is true that the pump heat numbers are small, it’s also true that the gains by flow rate are small. Because both values are small, it doesn’t take long for heat dump to counteract the net flow rate gain by more pumping power. While we are splitting hairs, efficiency should not be ignored. For the same flow rates with two different pumps, the pump with the better efficiency will generally dump less heat into the loop and net fractions of a degree better temperatures.

With that said, you should know that the Swiftech MCP-35X pump is very efficient electrically compared to the D5 series pumps. I like both pumps very much, but it should be noted that you’ll have a little less heat dumped into the loop using a pump like the MCP-35X.


I will include this pump in my pump noise thread for further noise analysis, but considering it’s a DDC pump with variable speed, it sounds a lot like a DDC pump except it runs a bit higher in speed at max setting and has variable adjustment to get really low speeds as well. This is obviously advantageous to have via PWM control because you could scale RPM and Noise via thermal demand if tuned properly. I will do more of this later in my noise thread.

In the mean time, I’ve included this video that explores noise somewhat informally using a custom PWM controller. This gives you a sense of the noise scaling that is possible via PWM.


I really like the pump/reservoir combo for all out DDC performance in a smart variable and warranty covered package. My only complaint would be the sponge system in the reservoir being difficult to bleed at really high flow rates, but that can be mitigated by either dialing down the PWM setting or using the top inlet with an internal tube.

I look forward to experimenting with this and more “Smart” water cooling products that can scale noise on demand. Swiftech has taken one of the most popular water cooling pumps, added smart PWM speed control features, reprogrammed the RPM scaling for even higher performance, and included a very well designed pump top. All of this comes in a factory warranty package, very nice!