The DIY Hydrophone That Showed Me Underwater Recordings Could Be Beautiful

In 2022 I was introduced to Jules Ryckebusch, a retired Navy submariner that decided to design a DIY hydrophone in his spare time.

What follows are stories, recordings, and AB tests that I’ve made with these amazing hydros over the past 2 years. As a general rule, I don’t do gear reviews but these hydros have opened up a whole new sonic world for me and I can’t help but share my love for these underwater microphones. For better context, please take a quick look at this Instructable before you continue reading.

DO AFFORDABLE HYDROPHONES ALWAYS SOUND BAD?

I think a lot of audiophiles think that hydrophone recordings sound “conceptually” interesting, but objectively sound lo-fi, hissy, and unappealing. I used to think this as well, but my mind has been blown. Low cost hydrophone recordings can actually WOW.

Overall, you can sum up these DIY hydros by thinking of them as having the similar hardware and sound quality to a $4,500 SoundTrap research hydrophone. However the average field recordist doesn’t need to leave the hydro mounted on the ocean floor for several months. So, by building the hydro yourself you can get an astonishingly good sound quality for around $200 per hydro!

BUILDING THE HYDROS

My soldering skills leave a lot to be desired, so I have a colleague that agreed to build a pair of these hydros for me in summer 2022 so I could test them in Greenland. They were barely finished in time and luckily I received an overnight DHL delivery the day before I left on the expedition!

I also took along my Aquarian Audio H2a hydros. And to be fair, the H2a/H2d is a solid commercial hydrophone that is sold for around $200. It is a great starting point for many recordists and I’ve used them myself in the past. But why wouldn’t you upgrade to $4,500 in sound quality for the same build cost of $200?

LET’S SEE THE DIFFERENCE

To start the comparison, let’s look at a spectrogram of all 4 hydros recording the melting of icebergs in parallel:

Channels 1/2 (L/R) are DIYs and Channels 3/4 (Ls/Rs) are H2as

• Can you see the difference?
• In the DIYs you’ll notice a full spectrum sound that even picks up the ultrasonic pings from the boat sonar!
• With the H2as, you’ll notice lack of high frequencies an unpleasant resonant band around 2 kHz

LET’S HEAR THE DIFFERENCE

A little context for what you're about to hear: imagine snow falling on a glacier, then more snow falls, and more and more and more. Eventually the weight of the layers compresses the airy snow into ice. The air in the snow is actually compressed up to 20 times normal atmospheric pressure in beautiful large bubbles! Then the ice gradually moves down the glacier over hundreds of years and finally calves off the glacier as an iceberg. As the floating iceberg melts in the fjord those powerful pockets of air explode like millions of tiny little gunshots! This makes for an incredible underwater soundscape.

I honestly did not know how great the DIY hydros would sound, so I wanted to do some AB tests. I set up two DIYs and two H2as running into a Zoom F6 while out in the middle of an iceberg filled fjord in Greenland.

I think the proof is in the pudding with this AB test. I alternate between DIY or H2a every 8 seconds:

DOWNLOAD & LISTEN

• If you’d like to listen to the uncompressed AB Test Quad files please use this WeTransfer download link.
• Channels 1/2 (L/R) are DIYs and Channels 3/4 (Ls/Rs) are H2as

FULL SPECTRUM DETAIL & ULTRASONICS

1. Here are some other spectrograms showing the incredible full spectrum frequency pickup (including ultrasonics).
2. I’ve recorded frequencies up to 96 kHz while recording at 192 kHz sampling rate. 
3. I’ve been told the DIYs could pick up frequencies up to 1 Megahertz, but unfortunately my recorders are not capable of capturing those sounds!

DIY Hydros – Icelandic lake ice lasers (with ultrasonics)

DIY Hydros – Snow falling on lake ice in Iceland (with ultrasonic clouds)

TIPS FOR RECORDING UNDERWATER

• Don't record in mono for underwater ambiences. I sounds terrible. 
• Sound travels 4-5 times faster underwater, so you need to space hydros further apart than acoustic mics to record in stereo. 
• These hydros act like an omni. But instead of a minimum of 40 cm of spacing for acoustic mics, you need at least 2 meters to get a nice stereo image underwater. 
• I've found that I gravitate to 3 meters of spacing as a starting point, but there is apparently no distance too wide. I spoke with a humpback whale researcher that recorders with a Quad setup where each hydrophone was spaced 1 kilometer apart!

RECORDINGS I’VE MADE WITH THE DIY HYDROS:

• So far, I've recorded lake ice lasers, underwater snow, calving glaciers, and underwater icebergs with these DIY hydros in Greenland and Iceland: 

• Here’s a long soundscape of underwater icebergs: 

HOW TO ACCIDENTALLY DESTROY YOUR HYDROS IN ICELAND:

• Here’s a YouTube Short I made about sacrificing a pair of DIYs to the recording gods in Iceland. 

ADDITIONAL RESOURCES:

• Hydrophone drop rigs are tricky for many reasons, but here is another Instructable Jules made about how to build them (using the same high fidelity hydros).
• DIY Hydrophone - Drop Rig Instructable

WANT A PAIR OF THESE DIY HYDROS?

• If you are good with a soldering iron, build the hydros yourself using these instructions. 
• Hire someone who already builds custom cables. They can often easily follow the instructable directions and build these hydros for you. That's is what I've done. 
• Gustav Landerholm has started to build and sell Jules' DIY hydro design. I haven't tested Gustav's build quality myself yet, but I've heard good things from colleagues who have. That said, I've ordered a pair of hydros from Gustav to use on my next expedition to Patagonia and will be testing them soon. 
• Gustav is building hydros in a non-commercial/hobby capacity, so please be aware that this can change at any point in time and that there are no guarantees that he can fulfill a potential order.
• If you've made recordings that show off the fidelity of these DIY hydros, please share them in the comments below. AB tests compared with other commercial hydros would be great too!