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Re: Re: homemade hydrophone

Subject: Re: Re: homemade hydrophone
From: Lang Elliott <>
Date: Thu, 28 Feb 2002 13:23:45 -0500
Actually, once while recording in a prairie marsh in North Dakota, I managed
to trip over my cable and overturn my SASS unit which was on a tripod. The
entire affair was completely dunked and it took me a minute or so to get to
it.

I took the two MKH 20s out and dried them using heat from the defroster in
my Van. After drying, they appeard to work fine. I later sent them to
Sennheiser and they told me they spec'd out just fine. The tech guy there
said if they are dried soon after dunking, there should be no problems. But
this only refers to freshwater.

I'm still using those same two mikes!

Lang

> Lang, don't you think soaking an mkh-20 is a little risky? Does an mkh dry
> out pretty well after it is wet? I tried adapting a pair of contact mics
> which was recommended for dolphin recording by the manufacturer after they
> said the biggest problem was making sure the dolphins didn't eat it. We'll
> to make a long (but entertaining) story short I think I got roughly 2
> seconds of sound before the rest of the day was spent salvaging what I
> could. In the end  I bought another pair of contact mics ...
> 
> 
> 
> -----Original Message-----
> From: Lang Elliott 
> Sent: Thursday, February 28, 2002 8:16 AM
> To: 
> Subject: Re: [Nature Recordists] Re: homemade hydrophone
> 
> 
> Mark:
> 
> Do you think the AFAB will produce better sound than a Sennheiser MKH
> 20/condom combo? I imagine that using a condom will drastically change the
> frequency response, causing significant rolloff at higher frequencies. Is
> this true?
> 
> Lang
> 
>> 
>>> From: Lang Elliott <>
>> 
>>> At some point we discussed how to make a simple hydrophone using a
> condom
>>> pulled over a microphone.
>>> 
>> 
>> Lang,
>> 
>> For starters, use an unlubricated condom!
>> 
>> Seal the open end around the mic cable (making sure to cover the XLR
>> connector) by making rings around the cable with electrical or duct
> tape.
>> WD-40 will remove any sticky tape residue afterwards. You could also
>> construct a cable with a couple of rubber "O" rings on it.
>> 
>> Tie the condom tightly to the mic cable in several spots, stretching the
>> condom over the rings.
>> 
>> I've only tried this method to a depth of 10 feet, and for about 15
> minutes,
>> on a dynamic mic and it worked just fine (as waterproofing, the sound
> was
>> muffled). I didn't use an electret or condenser because I didn't want to
>> risk an expensive mic in salt water.
>> 
>> The main disadvantage of the waterproofing is the inefficient acoustic
>> coupling of the mic element to the water.
>> 
>> If you want a low-cost, good performance hydrophone, I like the AFAB.
> Less
>> than $150!
>> 
>> http://www.afabsound.com/
>> 
>> hope that helps,
>> 
>> Mark
>> 
>> 
>> 
>> 
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