Seeking help troubleshooting measuring frequency response of plugins with REW

[Bedroom Researcher]

Hi, I'm new here and was hoping to find someone, who could help me figure out a solution to the following problem.
For a research study I'm measuring the freq-response of various hardware equalizers in the context of music production. Specifically focussing on the Pultec EQP-1A and software emulations (plugins) of this piece of gear.
I already have been able to capture data from the hardware but measuring plugins seems to be not quite as easy.

In REW I exported a measure sweep (256kMeasSweep 20 to 20k at -24db 48kHz 24bit) as .wav-file, then I've imported that .wav into Cubase Artist 12 with corresponding settings, put the Universal Audio Digital (UAD) Pultec EQP-1A plugin as the only effect in the signal chain and exported the sweep at 48kHz 24bit .wav without any extra settings like iXML or all the other stuff Cubase offers. I then tried to analyse the sweeps in REW via "import sweep recording" and chose the the same measure sweep as reference. The first exported file from Cubase worked but was distorted by about 260%, hovering around -40SPL from 20Hz to 3kHz, then jumping up to +100SPL at around 10kHz and above. After that I tried to load processed sweeps with different settings from Cubase but even though its a genuine .wav file, REW generated an error code ("not supported"). After exporting 20 different setting from Cubase (all .wav) I uploaded a working file and a non-working file to ChatGPT to analyse the files. Truns out the working file is 480k samples long, while the non-working file is 589k samples long. Also the RMS for the working file is 8848 RMS against the 10703 RMS of the other file.
I promise, I have not change any settings (at least not to my knowledge) but also I haven't found any settings that should corrupt the file.

Maybe someone here can point me into the right direction since at this point I don't know what to do and even different LLMs are giving up troubleshooting. If needed I can provide screenshots of everything. I'd be very greatful for any advice.

Cheers!

 

[Keith_W]

Do you want to take an acoustic measurement of your recording, or a hardware measurement?

For a hardware measurement, you will need an interface like a Focusrite 2i2 or better. I'll also assume you are using Windows. Set it up like this:

In REW:
- Set to Java mode
- Output: to Cubase Artist (assuming it has a WDM driver)
- Input: your interface

In Cubase Artist (I presume it's a DAW):
- Load your EQP-1 and put it in the signal chain
- Input: Default WDM
- Output: your interface

Your interface:
- use hardware or software loopback if it is available. For hardware loopback, you need a cable to connect the output of your DAC to the analog input.

Back in REW:
- Take a measurement as per usual.

If Cubase does not have a WDM driver, you will need to use a virtual cable, such as ASIO4ALL.

Note that a traditional Pultec EQP-1 generates distortion by design. That's how you get that "warm" and "tubey" sound. I don't know how well UAD replicated the EQP-1, but I would certainly expect some distortion. Not 260% though unless your settings are very wrong. I would suggest testing your setup first with a "clean" DAW with no plugins in the signal chain just to make sure you get a flat line as the output.