• Actual Measurements Barbs included 4.02"(103mm) length x 4.02"(103mm) height x 2.08" (54mm) width.
• Weight: 1lbs - 3.6 ounces
• G1/4 Barbs with Danger Den Fatboy HighFlow barbs, my current favorite barb!
• 3pin header with RPM monitor

Hydraulics Pump Testing

The most scientific way to determine a pumps performance is to plot the entire pump pressure vs flow rate curve. This can be done by measuring pressure at the inlet and the outlet of the pump with a digital manometer and using a gate valve immediately after this pressure measurement point.  This method of capturing both the inlet and outlet pressure then gives you the "Totat Dynamic Head" in pressure in (PSI) .   This method is consistent with the recommendations by gouldspumps.com pump field testing technical article for field testing and I believe more accurately captures the entire power provided by a pump and will provide more accurate curves for estimating flow rates.  Then utilizing this gate valve, adjusting the amount of restriction will net different flow rates and coinciding pressures the pump is producing over its curve.  All of this is preferably done at a very precise 12.00V or the tested voltage as needed.  While testing for pressure and flow rates, data was also collected using multi-meters to capture voltage and current in amps for power consumption data.

You'll see the pressure axis is labeled as "Total Dynamic Head Pressure which is equal to the "Discharge Pressure" - "Suction Pressure".  You can think of this as the reverse of pressure drop, it is "Pressure Gain" from the pump.  I believe most manufacturer pump curves follow this same testing method for developing pressure.  It's actually more common to refer to "Head" rather than pressure, but in water cooling we're always dealing with water, so I've had the habit of just reading in PSI and leaving it at that, so it's consistent in units with pressure drop in PSI.

Equipment:

• Dwyer Digital Manometer 477 Mark V - Accuracy .5% of Full Scale.  Range 0-20.00 PSI range, Resolution .01 PSI
• King Instruments 7520 Series 0-5GPM, 250mm scale - Accuracy 2% of Full Scale.  Range 0-5GPM, Resolution .1 GPM (can be interpolated to .02GPM)
• Water Source - Household water pressure - 50PSI at >5GPM - Because flow rate readings are instantaneous, household tap water and water pressure are a good and powerful source for pressure drop testing.
• Samlex PSA-305 Variable DC Power Supply - Adjusted voltage to be at 12.00V +-.03V.
• Calterm 66430 Multi-meter - Measured Voltage (DC Volts to .01V resolution)
• Cen-Tech Digital Multi-meter - Measure Current (Amps to .01 Amps Resolution)
• Mastech MS8209 Auto Ranging Multi-meter - Used for sound level decibel measurements. (.1db resolution)

And my results are as follows:

The pump performs very well, and to put it into better perspective here is a comparison of the pump curve in relation to the stock DDC 3.2.

Sound Level

Sound level is a fairly tricky thing to quantify.  For one, ambient noise level affects decibel level, and second decibel level alone doesn't give you a sense of the type of sound (Some noises at the same volume are more annoying than others).  I've chosen to record the sound level with my Mastech multimeter/sound level meter and record the sound using my stereo capable JVC GZ-MC500U digital video camera.  This way you can get a sense of the type of sound as well as the level.  I typically wait until late at night when the house is completely silent and run my sound level testing which I did in this case as well.

With about a 47db ambient noise level and placing my decibel meter about 6" away, the DD CPX-Pro increased the sound level as follows:

• 12V - 51 db = 4db Gain

And for some general comparisons, I found this chart that relates decibel gain to perceived sound gain:

Perceptions of Increases in Decibel Level
Imperceptible Change	1dB
Barely Perceptible Change	3dB
Clearly Noticeable Change	5dB
About Twice as Loud	10dB
About Four Times as Loud	20dB

And this environment general level condition:

Environmental Noise
Weakest sound heard	0dB
Whisper Quiet Library	30dB
Normal conversation (3-5')	60-70dB
Telephone dial tone	80dB
City Traffic (inside car)	85dB
Train whistle at 500', Truck Traffic	90dB
Subway train at 200'	95dB
Level at which sustained exposure may result in hearing loss	90 - 95dB
Power mower at 3'	107dB
Snowmobile, Motorcycle	100dB
Power saw at 3'	110dB
Sandblasting, Loud Rock Concert	115dB

So the pump added noise level fits in to the "Barely Perceptible Change" noise level, the lowest I've recorded yet, very nice!

Pros

• Excellent All Around Performance
• Spiral Shaped Volute for High Efficiency and Low Heat Dump
• 3 pin with RPM monitor (can be used to shut down computer in the event of failure)
• G 1/4 threading allows user flexibility in barb selection
• Silent, only 4db gain over ambient
• Ceramic Shaft Bearing for smooth operation and long life durability
• More compact than a Laing D5 (MPC 655)

Cons

• Larger size than the MCP 355

Bottom Line

I'm really impressed with this pump for several reasons.  The smaller sibling (CPX-1) has a strong reputation for being one of the quietest pumps around, and it's nice to see this larger and more powerfull big brother pump follow suit.  It's very similar in pumping power to that of the Laing DDC 3.2, but it does so with less power consumption/heat dump and it also already comes with G1/4 barbs.  The DDCs and D5 are also excellent pumps, and now we have another one to choose from with similar excellent performance.  This is an excellent all around pump for most water cooling systems.  Danger Den tells me this pump will retail for around $54.95, so it's at an extremely competetive price point and would cost less than both the Laing D5 and the Laing DDC 3.2.  Good news for us!!