The driver size differs between the two (NA vs 40 mm), which can influence sound depth, bass response, and overall audio clarity. Impedance levels vary (32 Ohms vs 36 Ohms), which can affect compatibility and audio output when used with different devices. Sennheiser HD-451 and Denon AH-D340 offer different noise cancellation capabilities (Yes vs NA), which can impact how effectively they block external noise. Both headphones offer solid battery performance, making them suitable for long listening sessions and travel. The frequency response differs (20 Hz-20,000 Hz vs 7Hz - 37,000Hz), which can influence how well the headphones reproduce lows, mids, and highs. Sennheiser HD-451 and Denon AH-D340 are well-known options in the wireless headphone segment, offering a balance of audio quality, battery performance, and smart features. Overall, both headphones are feature-rich and cater to users looking for a combination of sound quality, comfort, and wireless convenience. Both models support modern Bluetooth connectivity, ensuring stable wireless performance with compatible devices. There is a noticeable difference in weight (380 g vs 250 g), which may affect comfort during extended use.

Verdict: Choosing between Sennheiser HD-451 and Denon AH-D340 depends on whether you value better sound, longer battery life, or enhanced features.