Refer to the Quadro User & Installation Manual Section 9 (page 14). You need to assign 1 of the Quadro's 8 soft sensors to the High Flow Next or D5 Next temp sensor.

In the Quadro Sensors tab there are 4 local temp sensors and a flow sensor that correspond to the 4 temp headers and 1 flow header on the Quadro. Then there are 8 soft sensors. In the Quadro Sensor tab, click on 1 of the 8 soft sensors (your choice), then in the next section down assign a data source to that soft sensor. You can select the High Flow Next's temp sensor or the D5 Next's temp sensor, which are both measuring coolant temp. Then go to the Fans tab, select Curve Controller, then click on Controller Source and select the soft sensor that you just connected to the High Flow Next or D5 Next temp sensor, If you just want to use the coolant temp as the fan speed control source, you are done.

Delta-T
Many people prefer to use the difference between the coolant temp and ambient temp as the fan speed control source. This difference in temperature, commonly referred to as Delta-T, is what most directly affects the heat transfer between the coolant and the air. Using Delta-T as the control source prevents the fan speed from being affected by variations in ambient temperature. The Quadro comes with a temp sensor that you can connect to 1 of the 4 temp sensor headers, then mount it somewhere in the back of your case, or even outside the case. This temp sensor will provide the ambient temperature. The High Flow Next or D5 Next temp sensors provide the coolant temp. Now go to the Playground Virtual Software Sensors tab and make a new virtual software sensor. Add 2 data sources to this virtual sensor and assign them to the ambient temp sensor and the High Flow Next or D5 Next temp sensor. Once the data inputs are set up, click on Functions and add a X=A-B subtract block. Connect the 2 data sources to the inputs of the subtract block. The subtract block will subtract the ambient temp from the coolant temp giving you Delta-T Once you have the Delta-T virtual sensor set up, go back to the Quadro sensor tab and connect the Delta-T virtual sensor to 1 of the Quadro soft sensors, then go to the Fan tab and use that soft sensor as the data source for the fan controller.

The Playground Virtual Software Sensors are a powerful feature of Aquasuite. You could, for example, use Delta-T to control the fan speeds but also have them speed up if your CPU and/or GPU temps exceed a threshold value for more than 30 seconds. This is a very basic example of the kinds of things you can do in the Aquasuite Playground.

You're welcome. Were you able to get the fans controlled by coolant temp? I would get that working before attempting to set up Delta-T.

Making a virtual software sensor that is coolant temp minus ambient temp (Delta-T), then assigning that virtual sensor to one of the Quadro’s soft sensors, and then using that soft sensor to control fan speeds is a good way to start learning about the Aquasuite Playground and the concept of a virtual software sensor. These features provide a completely customizable level of control that can be used to do all sorts of interesting things. For example, if you put temp sensors at the inlet and outlet of a rad, you can use the difference in temp and the flow rate to calculate how many watts of heat the rad is dissipating. Since the whole point of increasing fan speed is to remove more heat from the coolant, this virtual software sensor allows you to see what the higher fan speed is actually doing. You can use this info to build a fan speed curve that optimizes heat transfer.

Here is a screenshot of a virtual software sensor that does this calculation. Disclosure - I grabbed this particular virtual software sensor from a REDDIT POST but it's a fairly common setup. Virtual software sensors can be exported and imported as XML files so they are easy to backup and share.

Glad to hear you got it working.

My understanding is that the display on the D5 Next (D5N) is intended to display information about the D5 Next, not other devices. There is a way to get the High Flow Next (HFN) flow rate data on the D5N display, but it requires a special cable and has to be set up in a specific way.

You can get cable #53294 and connect the High Flow Next (HFN) Signal header to the D5N Fan/Flow header. The D5N has a "virtual flow sensor" that reports a flow rate that is a calculated value based on several parameters. There is a calibration procedure for the virtual flow sensor, but even after calibration, it’s not very accurate. The User and installation manual even says it's really more of a flow/no flow indicator. The manual also says the virtual flow sensor will not work below 80l/hr, but in my case, it did not work below 180 l/hr. I could not use the D5 Next alarm because it would activate when my flow rate was fine because the virtual flow sensor was so inaccurate. When you connect the HFN Signal header to the D5N Fan/Flow header with cable #53294, the D5N can use the HFN flow rate data instead of the virtual flow rate. Several of the D5 Next display screens include flow rate so you can get the HFN flow rate to display on the D5 Next display by using cable #53294.

The setup is a little tricky. In the HFN Alarm tab under Signal Output, click the button that says, “Generate high flow sensor [53068] signal (DP Ultra, Inner Diameter <7mm)”. This will cause the HFN to generate a timing signal that emulates the #53068 flow sensor. #53068 is a discontinued flow sensor model, but it does not matter here. Then in the D5N Sensors tab, select the 2nd sensor and in the section below, under Sensor Type select Aquacomputer high flow [53068]. For Medium/Coolant select DP Ultra, and for Fittings Type select >7mm. Now the HFN is set up to emulate the flow rate signal for the #53068 flow sensor and the D5N is set up to receive that signal. After doing this, the HFN flow rate is available to the D5N and can be displayed in the D5N display templates that include flow rate. As an added bonus, the D5N Alarm will now use the HFN flow rate instead of the very inaccurate virtual flow rate.

I asked Aquacomputer why I couldn’t just send the HFN flow rate to the D5N in the Aquasuite software. I can assign the HFN flow rate to a D5N soft sensor, but that does not control the Alarm, or what is displayed on the D5N display. They said the reason is the microcontroller in the D5N does not have the capability to do this. It’s been a while and I don’t recall the details, but the only way to get the D5N Alarm and Display screens to use the HFN flow rate is to get cable #53294 and do the above procedure. I don’t think there is any way to get a fan speed from the Quadro to display on the D5N display. You could set up an Overview page in which you have the freedom to include any sensor data you want. Aquasuite can also import sensor data from HWINFO and AIDA64.

Glad to hear it worked out. Regarding updating the D5 Next, an Aquacomputer rep (Shoggy) told me that the D5 Next has very limited memory and they are already struggling to fit the firmware into it. Maybe at some point they will decide to update the controller board in the D5 Next and include a higher capacity flash chip. Unless and until they do that. I don't think there is any way around this limitation.