Cearvol Diamond X1 vs MDHearing VoltMax
Side-by-side HearAdvisor lab results with SoundGrades, expert pick badges, and the same visualizations we use in product reviews.

Cearvol Diamond X1
The Cearvol Diamond X1 is a budget-priced OTC hearing aid that earned a B grade with a SoundScore of 3.7/5 in our lab testing, placing it in the top 45% of OTC devices. At $199, it represents an accessible entry point for those exploring hearing amplification. The Diamond X1's standout performance is in music streaming, scoring 4.1/5—a strong result that sits 2.18 points above the OTC category average. This makes it notably capable for users who prioritize audio entertainment through their hearing devices. Feedback handling is also excellent at 4.5/5, meaning users should experience minimal whistling during normal use. However, speech performance presents limitations. Speech in quiet scores a mixed 2.8/5, and speech in noise registers at 1.7/5. While both metrics technically sit above category averages (+0.03 and +0.22 points respectively), they remain low in absolute terms—important context for anyone prioritizing conversation clarity. Own-voice comfort is another weakness, scoring 1.7/5, which is 0.81 points below the category average and may affect how natural users sound to themselves. The Diamond X1 is best suited for budget-conscious consumers who value music streaming quality and aren't heavily reliant on challenging listening environments. Those who prioritize speech understanding in noise or natural own-voice perception may want to consider alternatives in this price range, such as the higher-scoring Elehear Beyond or Apple AirPods Pro 2.

MDHearing VoltMax
The MDHearing VoltMax is a behind-the-ear OTC hearing aid priced at $699, earning a B grade with a SoundScore of 3.0/5 in our lab testing. This places it in the lower tier of the OTC hearing aid category, ranking 62nd out of 65 devices tested. In our testing, the VoltMax delivered mixed results across key performance areas. Its standout strength is excellent feedback handling, scoring a perfect 5.0/5—above the category average by 0.46 points. This means users can expect stable performance without whistling or squealing during typical daily activities. However, speech clarity proved challenging, with speech-in-quiet scoring 1.9/5 (0.93 points below category average) and speech-in-noise at 1.0/5 (0.48 points below average). Own-voice comfort measured 2.4/5, slightly below the category norm. A significant limitation is music streaming, which scored 0.0/5—nearly 2 points below the category average. Users who prioritize phone streaming for calls or media should consider alternatives. The device features rechargeable batteries, offering convenience over disposable options. At this price point, several competitors deliver substantially stronger overall performance. The VoltMax may appeal to budget-conscious consumers who primarily need basic amplification with reliable feedback control and don't require streaming capabilities. Those seeking better speech clarity or music streaming should explore higher-scoring options in this price range.
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Performance metrics
Scale 1-5 (Tuned)
Lab metric by fit
Scale 1-5 (Tuned)
Speech level
Adjust input dB (Tuned)
Amplification (REIG)
Insertion gain at 65 dB (Tuned)
Audio scenes
Recorded samples (Tuned)
Fitting configuration for tuned fit