Hydrophone Shoot-out

Last month I attended the Australian Wildlife Sound Recording Group’s Workshop which was held near Smiths Lake in NSW, Australia. It was a great week of sharing knowledge and experiences.

A couple of the sessions that we did focused on hydrophones, and I was fortunate enough to be allowed to borrow a few different hydrophones to go and make some recordings so that I could compare the recordings from them. I only had a limited time with them and there weren’t many places close by and easily accessible for doing some recording with them, but I did get a chance to hang them off a jetty in the Southern end of Wallis Lake.

The set-up comprised four hydrophones running into a Sound Devices 788T with the channels linked so that gains were precisely matched.

The Sound Devices 788T with hydrophones hanging off the jetty

A sample of the recording can be played or downloaded below and comprises:
00:00-00:20 – JrF D Series with Triton Audio BigAmp Piezo Preamp
00:20-00:40 – Ambient ASF-1
00:40-01:00 – Dolphin Ears XLR version with 20dB gain added in post
01:00-01:20 – Aquarian Scientific AS-1

There is no post processing on this other than the 20dB gain added to the Dolphin Ears section. Overall average levels are fairly low but I didn’t want to cut off or limit the higher transients so left things unprocessed.

Below is a screenshot of the spectrum view from iZotope RX to give you an idea of the frequency response and noise. You will see that the Ambient ASF-1 and Aquarian Scientific AS-1 have wider frequency response generally, but also more noise along with that as a trade-off. The JrF with the BigAmp Piezo preamp has a good low frequency response, thanks to the preamp impedance, but the Dolphin Ears has less of the low frequency response as it is just plugged directly into the 788T preamp.

So which is best? I think this is a subjective thing and will depend on what you are recording. I think if you are recording louder sounds or sounds where the wider frequency response is important then the Ambient ASF-1 or the Aquarian Audio AS-1 would be a good choice, although these are also more expensive options, with the Ambient ASF-1 being significantly more expensive than the others. The self noise of these units is fairly high though, so for some people recording quiet sounds and less concerned about the wider, flatter frequency response might prefer either the JrF or the Dolphin Ears, even though they have more of a mid-range focused response. I suspect using a high impedance piezo preamp/buffer with the Dolphin Ears might get better results in terms of frequency response.

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