How do mics work and which is best ? (1 Viewer)

Hi All
I've posted on here before and was very grateful of the advice received and wondered somebody could help again. I'm at present using an Oylmpus ls5 recorder for bird sound recording which had worked perfectly well for ad-hoc recordings for several years, easy to use with a reasonably good quality sound and reach. I am now thinking about upgrading to either a shot gun type mic or a mic use in conjuction with a Parabolic reflector.

I really want to try and understand what they both do and their limitations ( I realise the size and portability differences) before making a purchase
.
Night recording ( mainly overflying birds) is something I have been attempting and have a particular interest in and would be one use for what ever system I bought. I have been advised to take the parabolic reflector route by several people although seemingly with no other reasoning than its the best route ! As I understand it a reflector dish will magnify the sound (by approx. x10 ?) presumably a shotgun mic has a similar ability ? Does the dish design mean it operates over a wider area, picking up sound then concentrates/bounces it off the dish and onto the mic or just able pick up sounds further away? Therefore does a shotgun mic have a more concentrated recording zone in front of it ( like a beam ), that reaches further rather than a spread recording zone ? A shotgun mic also needs a separate power source or can be powered by some recorders ?

Hope that all makes sense, been trying to glean what info I can online but finding it all a bit confusing, I'm just trying to grasp initially in lay mans terms an understanding on how the two systems work and wether one is actually better than the other.

Many thanks

Have you read this?

http://www.wildlife-sound.org/equipment/newcomersguide/index.html

As you will see the shotgun mic works by excluding extraneous sound so that the intended sound is clearer, it does not itself amplify sounds, but by adopting a low noise construction and sensitive components some are capable of considerable preamplification into the recorder. Sensitivity varies and this is best discovered from the manufacturers downlodable spec sheets, these give the frequency ranges and coverage as well. For an LS-5 you cannot provide 24v phantom power and will need a powering module as described in the link. Plenty of coverage of the ME66 K6 combination in this forum.

The parabolic mic will, if it is of reputable origin amplify the sound and provide directionality (it was used pre-radar in the 2nd world war) performance does depend on size and construction and good professional ones are expensive. As they work like a torch reflector it is possible to focus on a wider or narrower area. So either may provide a more concentrated beam depending on their specification.

So - both shotgun and parabolic reflectors can cover different fixed areas depending on their manufacturers specification. A shotgun is usually fixed in this respect - so you need to study the documentation, some less expensive shotguns designed for use with domestic video recorders can be switched to cover a wider or narrower field.

Worthwhile parabolics cost a lot more, unless you build your own (examples can be found on the internet by searching), should provide a good degree of non- electronic amplification and give a 'directional beam' which is often variable.

Many good mics need phantom power (24-48v) more upmarket recorders can provide this, however, there are many cases where the mic requires more power (amps) than the recorder can provide (giving distortion or wierd noises) so it is important to read internet bloggs to make sure that the combination you are thinking of buying will actually work. You can sometimes get round this by using a self powering module made avasilable by the microphone manufacturer. You will also need to ensure that you are using a cable or adaptor that will work with your recorder. The LS-5 (from memory) can provide a 1.5 v power required by several mics designed for this kind of recorder this should normally be switched off (from a menu) when dealing with these more professional mics.

Strictly speaking you don't need to replace your LS-5 - if you read the threads in this forum you will find much useful information on interfacing a recorder fitted with a 3.5mm jack to shotgun mics (mainly the ME66 K6 combination as it works).

As you are probably aware by now most mics available for this use are mono.

As sound recording is not standardised for easy domestic use like say digital photography, you are best served copying the successful route forged by others, otherwise you will find that it is a steep learning curve with much frustration along the way.

I hope this helps.

J

A parabolic dish is directional like a shotgun microphone, probably more so.

Do you intend waiting for these overflying birds in order to aim the microphone at them? If not, then directional microphones like shotguns or parabolics might not be what you want. Have you tried recording them with what you have? If so, what was wrong with the recordings that you want to improve?

Thank you both for replying, and for the link J ( which is well worth reading ) and also the advice.
In reply to your question pshute I do use the recorder for fly over birds I can see ( and hear ) for which it seems to do a remarkably good job. I am intending to initially start using the LS5 for nocturnal migration recording, the main issue I feel is how good the mic needs to be to effectively record unseen over flying birds not knowing how high they are likely to be. The majority of my recording will be on the coast so I suppose now thinking about it, birds arriving could already be losing height as they sense land below and departing birds could therefore presumably already be reasonably low on leaving, so maybe your right I may not need an added microphone. Understanding how the different systems work though will I'm sure be invaluable in the future though. Do either of you ( or anyone else) have any thoughts as to whether its feasible to maybe use the LS5 injunction with a parabolic reflector if I find I do need a better/stronger mic ?
Thanks

The simple answer is a qualified yes, depending on the parabolic mic. You will need to get/make one that either is compatible to start with or obtain an interface that will allow you to get the full benefit of the mic. This latter requirement varies from relatively simple to expensive depending on the mic you have in mind, remember, there is limited standardisation, you need to read the manufacturers data and discuss your needs with the person selling it to you.

Quite frankly I would tempted to build one, just to get a feel for them, the biggest problem I encountered was the difficulty of getting a big enough reflector. This will probably be spherical rather than parabolic, but it is still focussable and the choice of mic can be a simple lavalier (little plastic one) with a 3.5 mm connector. There were plenty of build your own entries on the net when I had a bash at it, the ones that want you to mould your own glassfibre parabolic reflector are overkill for this experiment. I found a rigid reflector was far more effective than adapting an umbrella, but more difficult to find something big enough and inexpensive.

You also need to make sure that coastal cross winds do not use the parabola as a resonating chamber, which is why you see professional ones with cotton scrim or similar across the aperture. The shotgun will need the usual hairy dead cat approach.

Generally speaking anyone selling expensive professional kit is only too pleased to make sure that what they are selling is what you need. It may be possible to rent kit which will potentially give you a lower cost introduction to the joys of such a beast, they are cumbersome to lug around.

Many parabolics do have the ability to focus on a tight area or cover a wider field depending on the distance from the focal point of the reflector, as in a torch, so they might be better than a shotgun for your needs.

A further option is to use a shotgun mic intended for a domestic video camera, these will usually work with the LS-5 with no hassle at all. Their slightly wider view of the world may be adequate. Some have variable gain (internal amplification) that allows a degree of fine tuning. Rode do several that come with vibration proof mounts. Remember that a mono mic and cable will often just record onto the left hand channel of a stereo recorder unless you use a simple adaptor or the recorder allows you to change an appropriate setting in its menu. This is potentially the lowest cost approach.

Thats brilliant, thanks J, just one more quick question, is it possible ( or beneficial ) to use the microphone/s on the LS5 in conjunction with a parabolic dish, i.e. fit the recorder into the dish using this to focus the sound into it.

It is possible, I have seen a picture of a similar setup. It was a home build. I seem to remember that the rig used a wired remote in order to avoid moving the recorder once it had been set-up. Clearly with all parabolic setups you need to monitor the sound in real time when setting up through headphones ideally. Mounting the recorder in the microphone position makes set-up a bit trickier, its relatively easy to calculate roughly where the point of sound focus is but in practice fine adjustment can make a difference. Also the mount for a recorder needs to be fairly strong to avoid any movement. I have no idea how effective it was.

The reflectors people use these days tend to be thin moulded acrylic, which can be rolled up to make transporting easier. I've seen blank dishes on eBay, but postage from the USA to Australia was a bit expensive, so I've never tried one. There might be a local manufacturer, so it's worth a look.

60cm diameter seems to be a common size people use, designed to be deep enough that the focal point is in line with the lip of the dish. Bigger is too unwieldy, smaller loses the low frequencies.

I've also heard of people using a steel wok as a reflector. It's not efficient because it's not actually a parabolic shape, but apparently it works. You'd have to experiment to find where the focal point is.

That all said, I'd try it with just the bare recorder first. If you can hear the birds then you should be able to record them, it's just a question of whether you'll be able to id them over the background noise.

I don't think you said whether you'd be running it unattended, or if you'd be there to aim it. If unattended, perhaps the parabola idea would randomly exclude as many bird calls as it would enhance.

Thanks to you for both your thoughts, all makes good sense and has helped no end and has given me plenty to think about / consider.

migration mic

Gary,
I've done some night migration monitoring, I have tested different types of mics and based my selection on that and on some math. It turns out that you don't gain anything using parabolic or shotgun mics. Yes you get some extra apparent gain, but you loose an equal amount because the directional beam is narrower. On top of that you get extra atmospheric attenuation. So an omnidirectional pattern is about as good as you get. If you are recording close to roads or close to the ocean, then a (rather mildly directional) cardoid mic is better, because you can point it up or tilt a bit, and you cen get rid of substantial amount of local noise. I have used ME62 mics for this - of course they have to be shielded for wind and moisture.

A parabolic mic is great for targeted recording. I use that often too.

Good recordings to you!
Harry

Thanks HarryJ, the results you got were acceptable with a shotgun type mic then ? Would be considerably cheaper than a good parabolic setup, its not so much the price its what you would gain for that extra money.

garyelton said:

Thanks HarryJ, the results you got were acceptable with a shotgun type mic then ? Would be considerably cheaper than a good parabolic setup, its not so much the price its what you would gain for that extra money.

Click to expand...

For untargeted (night) migration I would go for a mic that has either an omnidirectional or a cardoid, not a super or hypercardoid of the shotguns. Of course a shotgun works for migration but in my opinion it is not as good. A shotgun mic is a good compromise though if you want to make also e.g. pointed species recordings - they are good general light mics (SennheiserME66+ K6 takes you back ~400 moneys (USD/€/UKP) .

Parabolics setups are useful if you need better pointing and targeting than you get from a shotgun. The parabolic sound is different from a shotgun mic sound. Good quality parabolic boosts more the high frequencies - not the 6" that are sold for 10 moneys. The price of a parabolic setup depends on many things. If you are good with your hands you can build a good parabolic system with a parabolic mirror (~100 money or less ) and a cheap 20 moneys omnidirectional mic, but then you need to figure out the cables and the handle and mic support. If you buy a ready made parabolic system (eg telinga) it will put you back 1000 moneys.

I have both shotgun mics and a parabolic stereo. Both are good and it is often a matter of taste which one I end up using.

Harry J

I've been using the sound approach for migrating birds for some years now and this is what I got out of it: my first tries using a sony pcm-10 were not that bad but not sufficient for difficult species ID.

Beeing plagued by road noise and others unwanted sounds, I then used a parabolic mic (60cm dish) connected to the pcm-10 but proved way too cumbersome in the field and highly subject to wind problem, would it be hissing sound or having the dish flapping in a 4bft wind.

I then switched to a cardoic sennheiser me66 with a rycote blimp connected to my pcm-10 and headphone monitoring. Great results for birds flying in the path of the mic range with some true rare gems (olive-backed pipit, red-throated pipit, little bunting, dotterels, etc.) for my region and the mic sensitivity enabled perfect ID of difficult species, but still missed quiet a few birds flying left or right.

I then added a 2nd sennheiser me66 also shielded with a windjammer to my pcm-10. Terrific stereo image, fewer birds missed but connectivity problematic with the 3.5 jack only port of the pcm-10 (some hissing, no balance between left & right mic, etc.). I just purchased a Tascam DR-100 which has 2 XLR ports and I'm planning to do 4 channels recording using the integrated mics of the Tascam for overhead birds recording and left and right ones using the two me66.

All mics and recorder are placed on tripod, I follow the recording with headphone and start recording using the remote and a pre-rec time of 2 secs (5 secs for pcm-10). This eliminate lengthy .wav files and shorten time spent analysing spectrograms.

This set-up should be perfect for my needs and environment and I can't wait for the migration to begin within the next few weeks! Good luck to all of you for a cracking 2016 migration!

Good luck and please let us know how you get on.

Thanks for that schienpflug, likewise be great to hear how you get on.