Further Information
These are a true collectible and in fantastic condition (I chose "Excellent" as I would rather downplay).
I bought these from the original owner 1 year ago (he is in his 70's) and he has cared for these since buying new, like they were his child.
The HD 424s were the superior successor to the 414s and 410s with better separation and staging.
The HD 424 was one of the most successful hi‑fi headphones in the world during its era. It offered:
• A groundbreaking open‑back experience
• A soundstage few headphones could match in the 70s
• A lightweight, futuristic design compared to the bulky Koss models of the time
It helped define what “modern” headphone listening could be
I have replaced the pads with brand new Yaxi pads, and these sound amazing for 1970's headphones.
Comes in original box too- which I will layer with foam for safe transport.
They were $80 USD in the 1970s, which would equate to about $660 USD now with inflation (Using current inflation data, $80 in 1970 has the same purchasing power as roughly $668 today.
That figure comes from U.S. Consumer Price Index calculations showing a cumulative price increase of about 735% from 1970 to 2026. -Source - Co-Pilot).
The clarity and detail from the treble is excellent and the mids are buttery smooth.
The bass is there, but it's not the focus and may need some EQ to boost the lower end for some people, but the quality of sound is excellent!
I put them on my Feliks Echo Vibe OTL tube amp and they really came alive.
Can ship anywhere in Aus for just $15 or pickup and demo on the Surfcoast.
Any Senny fan or collector will just cherish these, especially in the condition they are in and the quality of sound they produce.
Ask me anything!
English (US)