At 7:02 AM +1100 3/3/08, Paul Jacobson wrote:
>Hi Rob and Phil,
>
>The recording was made in a rural setting, but there was significant
>breeze in the tree canopy, so that will clearly have some effect.
Ah,.. The nose-dive in frequency response your sample shows starting
at 4KHz (see green line on the right most chart)
https://pantherfile.uwm.edu/type/public/media/RichAT3202_PaulAT3202.jpg
suggests to me that either the setting you recorded does have high
sound levels from 125 to 4K Hz or the mics are deficient in the
high-end. The former is more likely with matched results.
>But that does not explain what sounds like a LF plusing in the recording.
>I made a short recording last night in almost dead clam conditions
>hand holding the rig, and there are massive levels of LF energy present.
There usually are massive amounts of low hz energy because these
sounds have the power required to travel great distances. Without
knowing exactly what I'm listening to, its hard to be certain, but I
don't hear anything strikingly abnormal about the lowest octaves in
your sample (2nd half of:
https://pantherfile.uwm.edu/type/public/media/RichAT3202_PaulAT3203.wav)
The low end tonal structure (left side of
https://pantherfile.uwm.edu/type/public/media/JacobsenAt3032_Sono_Flat_RolledOff.jpg)
looks pretty normal to me. Faint standing tones and bounciness below
125Hz from background presence is quite common.
>I want to investigate what is going on a bit more fully but it does
>sound to me like some kind of LF oscillation similar to what Phil has
>found.
If the HDP2 has phantom powering issues with the AT-3032, that might
show up in a web search. Do you have any way to try the mics on
another recorder or power them with a portable phantom supply like a
Rolls PB224 or Art Phantom III?
>I'll hook up the mic and recorder to a 'scope at some stage
>today and see if I can pinpoint what is happening.
>
>I'm using HD280's for field monitoring, and I've been checking
>recordings with them at home as it's the only way I can get an idea
>of what is happening in the bottom end. They are quite nice phones ;)
If the mics have poor high-end response, I bet you would have noticed
it when you put on the headphones in the field. Rob D.
>cheers
>Paul
>
>On 03/03/2008, at 3:52 AM, Rob Danielson wrote:
>
>> Hi Phil-
>> Sorry. I think I may have confused your application with the 3032's
>> and the Mix Pre and Paul's.
>>
>> Phantom powering could be a factor, but Paul seems to be connecting
>> his mics directly to the HDP2. If so, we're getting down to unusual
>> suspects. It seems unlikely that both 3032's would arrive at his
>> doorstep with _matching_ poor frequency response. That leaves cables,
>> recorder/recorder settings and the mic rig as suspects. The high
>> frequencies could be attenuated by essentially "blanketing" the mics
>> with excessive wind protection, but this would be inconsistent with
>> the lack of mic self-noise (hiss) in Paul's sample. I assume Paul's
>> HDP2 was at or near full mic preamp gain in that location.
>>
>> Thanks for the nod about preserving low Hz content. In the sample we
>> are studying, the sonogram from Rich's "quiet" rural setting, shows
>> how much of the sound energy resides below 125Hz:
>>
>><https://pantherfile.uwm.edu/type/public/media/>https://pantherfile.uwm.edu/type/public/media/
>> RichAT3202_PaulAT3202.jpg
>>
>> I suspect some recordists use the low cut filter to make it easier to
>> hear the high frequency content/calls in the field, but its possible
>> to bring home a fuller spectrum and still experience good monitoring
>> by using fully-enclosed headphones. Sennheiser HD280 phones, for
>> example, cost $90USD and provide about 30dB attenuation. Of course,
>> the low frequencies can always be shaped in post. Rob D.
>>
>> = = = =
>>
>> At 9:49 AM +0000 3/2/08, Phil Tyler wrote:
>>> Hi Paul
>>>
>>> Just a thought I have a pair of AT3032's which I use with a Sound
>>> Devices MixPre.
>>>
>>> I found that the MixPre became unstable when using AT3032's due to
> >> the way in which
>>> they work with phantom power. Most phantom power mic's vary the
>>> voltage they draw
>>> depending on the signal. AT3032's vary the current and this is what
>>> causes the Sound
>>> Devices MixPre the problem, due to the way it is itself powered.
>>> This low frequency
>>> instability was reduced using the LF cut on the MixPre.
>>> But I found another, much better, way around the problem, as the
>>> AT3032's are current
>>> and not voltage dependent they have quite a wide voltage range they
>>> can run on. So
>>> switching my MixPre to 15 volt phantom, rather than the normal 48
>>> volt and my problem
>>> goes away. As the MixPre's power supply can cope using the lower
>>> phantom voltage, and I
>>> can record without any LF cut, as Rob tells me I should :-))
>>>
>>> It may be your system is exhibiting a similar problem but not
>>> actually becoming fully
>>> unstable?
>>>
>>> Hope you find a solution soon.
>>>
>>> Phil
>>>
>>> --- In
>>> <naturerecordists%
>>>
>>>40yahoogroups.com><naturerecordists%40yahoogroups.com>
>>> Paul Jacobson <> wrote:
>>>>
>>>> Ok I guess I should post an illustration of what I'm getting.
>>>>
>>>> The whroo frogs recording which I posted to the list, and to which
>>>> John referred to, was made with LF cut on the HDP2 switched on. I
>>>> initially started recording with LF Cut off and had the recorder
>>>> running when I flipped the switch. There isn't much happening in
>>>> the
>>>> recording apart from a bit of rustling, but it clearly illustrates
>>>> the kind of LF energy or "growl" that I'm trying eliminate.
>>>>
>>>>
>>>>
>>>><<http://www.urbanbirder.com.au/audio/play/13>http://www.urbanbirder.com.au/audio/play/13>http://
>>>> www.urbanbirder.com.au/audio/play/13
>>>>
>>>> I'm trying to identify what is contributing to that LF energy. My
>>>> suspicion is that resonances from the tripod are being transmitted
>>>> into the rig, but looking at sonograms of Walt's comparative
>>>> recordings seemed to suggest that the might mic be a contributing
>>>> factor as well, but that could very well be a misinterpretation of
>>>> the recordings. I certainly wasn't condemning the AT3032's to the
>>>> junk heap - in fact I'm about to order another to use in a Telinga
>>>> Universal rig.
>>>>
>>>> I'm sure it's been stated many times, that these rigs are
>>>> experimental
>>>>
>>>> The main reason I am looking at this is that I want to tweak/
>>>> rebuild
>>>> the rig before I head up to the Alice Springs area in May for a
>>>> couple of weeks. The top priority is incorporating a shock
>>>> mounting,
>>>> which I hope will eliminated much of the LF rumble/growl.
>>>>
>>>> cheers
>>>> Paul
>>>>
>>>>
>>>> On 02/03/2008, at 4:38 PM, Rob Danielson wrote:
>>>>
>>>>> Paul,
>>>>> Sorry to hear your AT3032's are not performing up to your
>>>>> expectations. I second John's suggestion. If you are certain the
>>>>> abnormal response or artifact lies in the lower registers, it would
>>>>> help to select a sound from (or record a test in) a quiet location
>>>>> away from low frequency sound sources. It common for locations to
>>>>> have lots of energy in this part of the spectrum. A wooden barrier
>>>>> can lift the upper mid-range and brighten-up the sound a bit,
>>>>> but it
>>>>> typically does not emphasize the lows. Of course, if you have other
>>>>> mics you can make recordings with in the same location/conditions,
>>>>> they'll will provide additional reference. Rob D.
>>>>
>>>
>>>
>>
>>
>> --
>>
>>
>>
>>
>>
>> "While a picture is worth a thousand words, a
>> sound is worth a thousand pictures." R. Murray Schafer via Bernie
>> Krause
>>
>> Yahoo! Groups Links
>>
>>
>>
>
>
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