# Hifiman Sundara Open-Back Planar Magnetic Headphones - Official Thread **URL:** \ **Category:** Official Headphone Model Discussion\ **Tags:** hifiman, planar\ **Created:** [June 10, 2019, 10:25pm UTC](https://forum.headphones.com/t/hifiman-sundara-open-back-planar-magnetic-headphones-official-thread/3248 "2019-06-10T22:25:10Z")\ **Posts on this page:** 1\ **Showing post:** 375
**Author:** ![Resolve](https://sea2.discourse-cdn.com/flex016/user_avatar/forum.headphones.com/resolve/32/51647_2.png) [@Resolve](https://forum.headphones.com/u/Resolve)\ **Post date:** [May 26, 2023, 5:50pm UTC](https://forum.headphones.com/t/hifiman-sundara-open-back-planar-magnetic-headphones-official-thread/3248/375 "2023-05-26T17:50:00Z")
Just posting some new measurements from the B&K 5128 Raw ![HiFiMAN Sundara 2020 5128 raw](https://us1.discourse-cdn.com/flex016/uploads/headphones/original/3X/d/0/d0f52cfc6cf8766718f9b5c1fce38469ff778b14.jpeg) Compensated ![HiFiMAN Sundara Comp 5128 2023](https://us1.discourse-cdn.com/flex016/uploads/headphones/original/3X/3/a/3a54e5a5a9ab75e0595cce900e791ef038740b9b.jpeg) For those unaware, there’s an air gap between the driver and the housing on the Sundara, which gives it a subtle bass boost compared to other open-back planars. The tradeoff is that you lose sub-bass at 20hz due to the dropoff below the resonance frequency (Fs). When sealing up the driver gap but putty (Funtak here in Canada), it drops the bass boost and provides extension all the way down. I don’t recommend doing this, since perceptually it’ll sound like there’s more bass if you just leave it open. But it is the explanation and conclusion to the curious case of the Sundara’s missing sub-bass below 30hz. ![HiFiMAN Sundara funtak2](https://us1.discourse-cdn.com/flex016/uploads/headphones/original/3X/3/8/38efb3f066247a43ce4b03aef86f7effb81b9b13.jpeg) --- _[View the full topic](https://forum.headphones.com/t/hifiman-sundara-open-back-planar-magnetic-headphones-official-thread/3248)._