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Low-cost seismic instruments, such as Raspberry Shake sensors, are increasingly deployed to complement traditional seismic networks and enable applications ranging from network densification and education to low-cost forensic seismology monitoring and local early warning; however, systematic performance comparisons with broadband stations remain essential.The Cadí station, part of the CA Catalan network and operated by LEGEF-IEC, is located in the eastern Pyrenees, a region of moderate seismicity that is of particular relevance for seismic hazard assessment and emergency planning in Catalonia. CADI is installed inside an abandoned tunnel that provides stable thermal conditions and protection from atmospheric effects; despite this isolation, the site exhibits medium-to-low ambient noise levels due to the presence of nearby transportation infrastructure. In general this emplacement provides favorable conditions for instrument comparison.In this study, we assess the data quality and detection capabilities of a Raspberry Shake RS3D short-period sensor through a direct comparison with broadband instrumentation (Guralp CMG3T and Centaur digitizer) at the CADI site. Before the comparison period, only the low-cost sensor was active due to broadband maintenance; afterward, both instruments ran together, allowing direct comparison and validation of the prior CADI recordingsContinuous seismic data recorded between September 2024 and April 2025 were analyzed and compared using cumulative Power Spectral Density (PSD) spectra and Root Mean Square (RMS) amplitude estimates, using part of the SeismoRMS free software (Lecocq et al., 2020). Broadband data were compared with Raspberry Shake recordings during their overlapping operational period to assess noise levels, frequency response, and sensitivity across relevant seismic bands. PSDs were evaluated relative to the New Low and High Noise Models to characterize baseline performance.Results show that both instruments exhibit comparable spectral behavior above 0.1 Hz, capturing similar noise patterns and anthropogenic signals in the high-frequency band (10–40 Hz). However, the broadband sensor demonstrates superior performance at lower frequencies, reliably recording signals below the narrowband instrument’s response range.This difference becomes critical for the detection of teleseismic events, which are only clearly recorded by the broadband station, while both sensors adequately capture local and regional earthquakes. These findings highlight the strengths and limitations of low-cost seismic instrumentation and confirm that Raspberry Shake sensors can effectively complement broadband networks for local and regional monitoring, while broadband stations remain essential for comprehensive seismic observations. ReferenceLecocq, T., Massin, F., Satriano, C., Vanstone, M., & Megies, T. (2020). SeismoRMS - A simple python/jupyter notebook package for studying seismic noise changes (1.0). Zenodo. https://doi.org/10.5281/zenodo.3820046