Induction recordings - what microphone should I get?

Hi there! I'd like to try induction recording.  If you've done some induction recordings, can you post about the mic you used to help me decide which to get?

eyore said:
There really is a choice of one (without getting into serious money or making your own - which some here have done).
There are expensive induction mics?  I know I can spend a few thousand dollars on a very nice conventional directional mic, a.k.a. "shotgun" mic.

There are cheaper induction mics if you can find an electronics store, either brick-and-mortar or online.  The mics are usually labelled as a "telephone pickup".  One example:

I suspect that induction mics exist for professional applications ( do the CIA honestly slip down to Radioshack)?
It's only a presumption though.
I was going to suggest getting two or three (in case one is a lemon) and at that price it's worth a few spares!
Shame it's a minimum shipping charge of $8.99 though  :-\
Actually, they might (well they may order direct or not need them anymore).  ;D Kind of like how coroners can use hedge clippers and other power tools (not making it up) on corpses. They're dead and it does a better job at breaking open that rib cage.
As other's have said, there's really only one choice.  I picked up like 5 or 6 a few years back on eBay for less than $20 total.
I add longer cords with shielded wire and have also made a few stereo pickups for an attraction of two, but I'm not sure if anything really helps.

You'll get the most benefit out of:

a.  Not moving the pickup during recording
b.  Knowing your way around Audition or some other audio editing app.

Get a few recordings, you'll need them.
Thanks everyone!  Tips for recording are also very helpful.  I read somewhere that you can get a lot of noise in induction recordings.  Just curious what causes this and what techniques you use for limiting/eliminating it
An induction mic picks up the magnetic impulses from the speaker magnet (rather than the vibrations of the speaker itself) therefore any electric/ magnetic source can interfere with the signal (think people talking when recording with an ordinary mic). Electrical equipment etc can cause "sound" to be picked up but, to be honest, what recordings I have made have never picked up anything bar the sound I was aiming for but I've probably picked easy targets. You certainly do get funny sounds if you don't place the mic just right but that's more a muffled sound (so you turn up the volume to hear it and so pick up the player's background hum). I'm far lacking in the experience of some here though but most of my recordings have only suffered from setting the wrong volume.
Do remember, pick a bad speaker and you'll get what you are hearing. Rubbish in, rubbish out.
Techniques for reducing any noises? Pick another speaker :D
When you get your induction recording kit together, try walking around the house with the recorder on and wearing headphones to monitor the input.  You should be able to hear the hum from the power lines running through house.  Theme parks have all sorts of electrical equipment scattered around their property so there's a good chance an induction recording will have hum or some other kind of noise in it if the speaker is close to enough to the equipment.  Some of the speakers I've recorded have a noticeable hum at night.  I try again during the day and the hum is gone.  What's the difference?  The lights are off during the day.  Occam's Razor. ;)

BTW, I've gone through 3 induction pickups because one or both of the wires in the cable keeps breaking, probably right where it enters the pickup housing since there is no strain relief "boot".  If you hear a lot of crackling when you move the pickup, that's probably a sign some of the wire strands have broken and are making intermittent contact.
What eyore said.  Induction recording is pretty particular.  You really need to be just about right on top of the signal.   Typically this means the speaker coild, but you can also get a decent signal from the wiring leading to the speakers.  It's tough because often you can't see the wires so it's a lot of trial and error.  

The orientation of the induction pickup in relation to the speaker coil makes a huge difference.  

After all of this, you will probably still have a decent amount of hiss on your recording.  This is probably a combination of the quality of recording device, induction "technology" and the source.  Post processing may be able to help, but if you don't know what you're doing you'll destroy the fidelity of the recording.  

It's a trial and error thing.  I have be doing it for a while and still have a bunch of problems.  Lately, while on vacation I just don't have the time to experiment anymore.  I did the Everest BGM loop that's been posted, it's about an hour and 15 minutes, but I recorded much more than that to make sure I got a loop point (I think I did but can't remember right now).  I got lucky on that one, I'm sure it's possible to get a better one right now, knowing what I know, but I just don't have the time to try.  Others have done 5-6 hours for a hour long track and still have what they consider a mediocre recording.  

Each speaker is different in terms of quality and levels.  You might not realize you set your levels wrong until far into the recording.   So, you reset your levels and try again.

Many of the new loops are hours long!  I tried the Animal Kingdom Lodge Villas pool loop and I think I heard it's like 6-8 hours long.  I didn't get it all, but I did get a bunch of it.  I believe that there's a shorter loop of about 30 minutes played over that, making multiple attempts useless for stitching the entire loop together.
As said, a lot depends on the actual connections to the speakers, their condition and much else. However, last year I did a full induction of the Discoveryland loop with the pickup resting on the top of an Omnispeaker (no tape or glue dots), set the recording level and took my son on the rides while it recorded (my wife stayed with it as she fancied a rest and a read of her book - it was a nice location and a very accessible speaker in a fairly quiet place). I don't have any expensive Hi-Fi stuff to play things on so maybe I'm not as critical as some need to be. I was pleased with the recording (a one-off as well). I recorded it as a WAV file and converted it to flacc to retain as much as I could of the quality.
Take this recording as an example of what someone who isn't experienced can do.
It's had nothing done to it -just recorded on the ZoomH2 with the pickup noted and copied directly to the PC from the SD card (copy and paste). I did snip the start and end points to get rid of the overlap - I daresay I could have made a better job of that  :-[
Not trying to blow my own trumpet (sorry if anyone thinks that)  but I was pleased with it and am just saying that, with beginner's luck, you can get some decent results from the start. You'll get better with experience, of course.
Bringing this way back from the dead, what do most people record onto? Cell phone? Separate recorder? Thinking about capturing Fantasy and Frontier Towers as one giant loop (I know a few remote locations) but don't want to waste the time invested.
Usually to a PCM recorder - Or before that I used to go to a MiniDisc recorder....  The PCM is a direct to MP3 format, much easier than the old MD way...
Zoom H2
Unfortunately my iPod is a later one (the earlier ones didn't have built in mics so needed an external one) and inserting a mic doesn't shut off the internal ones :( My cell phone only really makes phone calls.
Yeah, I used a minidisc recorder before too. The Zoom H2 records to an SD card so really easy to copy to the PC. Pop it in the card reader and copy and paste. Selection of formats too so no pesky conversions.
Little to choose between the Tascam and the Zoom, Tascam would have bee my second choice. Both great bits of kit and similar prices. It was the size and shape of the Zoom H2 that settled it for me as it didn't "look" like a recorder  ;).
So it seems that Radio Shack isn't selling our good old telephone pickup mic, and instead is selling this:
Looking up reviews of that mic, it picks up not only from the source, but surrounding noise too, completely defeating the purpose for us.

Where else can we find a good mic? I see this one online for cheap:
but has anyone tried it? I'm worried about the quality, but if the quality is the same (or better, which I'm not expecting) than this would be a good deal.
also possible that similar stores in the UK and Europe may be able to supply abroad. Unfortunately my source for them (Maplins) don't deliver outside the UK and Ireland. There are several available on May be worth asking the sellers if they can deliver to your area. Prices start around £2.00 UK. I've found no difference in quality in them at all - they either work or they don't (always a possibility with electrical stuff that you get a dud).
You could try using a parcel-forwarding service to order from Maplin with a UK shipping address and then have the service send it to you in the USA.  I just checked for reviews of Borderlinx and they are mostly negative :eek:.  I would definitely research any of the services listed in the article and its comments before using them. ;)
10 Parcel Forwarding Services for International Shoppers (so they can shop from Amazon/eBay/Walmart etc)
but have a browse on Amazon - if it can't be posted to your area (I'm presuming US) it should say so when you reach the page (and you can always try to buy and cancel if the warning doesn't come up - sometimes the warning comes up then). I know other fans in Europe have been able to buy them (I've had others asking where to get them but not from the US so no feedback there).
I don't know why Maplin stopped shipping abroad - they used to - stopped a couple of years ago.
Watch out for the telephone pickups that use the same part number as the good quality Electrovision pickup but are *not* made by Electrovision.  For example, this one for sale on the US ebay site:
This one looks like one of the lower quality pickups but it uses the Electrovision part number.  Coincindence or deceit? ::)
For comparison, the actual Electrovision telephone pickup:
yes one must beware of a few things. With the reduction in the number of old fashioned phones, the modern pickups have a microphone facility to record both sides of the conversation now (as the mic and earpiece are so close together on new phones). The last one I bought I had to read the descriptions very carefully to avoid those. One wonders whether production of "our" mics will continue for much longer - stock up now!
I do have both of those mics and I haven't really noticed a difference between them quality wise. The one on eBay was the same as was sent to me in error (it's squatter than the other one) so they sent me the electrovision Eagle one free of charge. I may just have been fortunate of course.
eyore said:
One wonders whether production of "our" mics will continue for much longer - stock up now!
Or you learn to wind your own induction coils. ;)  I haven't tried replacing the mild steel core in a retail telephone pickup with a ferrite core to see if that improves the pickup's sensitivity.  The diameters of the available ferrite cores were all larger than the existing steel core.  I think most ferrite components are sintered so they can't be machined.  I.e., I couldn't simply put the ferrite rod in a lathe and turn it down to the proper diameter.
I've opened both the Radio Shack and generic induction pickups to repair broken wires.  The pickup's connecting wire is stranded but it still breaks if it's flexed enough.  That usually happens right at the hole where the cable exits the pickup body.  There is a strain relief (i.e., a simple overhand knot in the cable) inside the pickup body to keep the cable from being outright pulled off the coil connections but there is no strain relief for the cable outside the pickup.  I used some RTV gasket maker compound to make an unattractive but effective strain relief at that spot and I haven't had a broken wire so far. 8)

Using dial calipers, I get a diameter of 0.191 in (4.85 mm) and a length of 0.54-0.55 in (~14 mm) for both the Radio Shack and generic induction pickup cores.  I see that site you linked to has medium permeability ferrite rods that are a little smaller in diameter, 0.175 in., and 60% longer, 0.875 in., than the steel cores.  A bit of paper or tape wrapped around those ferrite rods should make for a better fit.

I *assumed* the steel cores were made of mild steel based on their color and the price of the pickups.  It would be nice if the Radio Shack core turned out to be silicon steel because that material has a much higher magnetic permeability than mild steel and that's why the Radio Shack pickup has a stronger signal.
I found a picture I took of one of the Radio Shack telephone pickups I opened to repair it after it eventually developed a broken wire.  Just to the left of the knot in the wire, you can see where the wire was pinched by the pickup housing (the triangular notch in the insulation), causing the wire to break sooner than it would have normally.


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It's not that hard if you have a woodworker's coping saw or a model builder's razor saw.  Carefully saw along the seam between the pickup body and the end cap.  Be careful with the depth of the cut and you'll avoid damaging the pickup coil and wiring.
I'll wait until one stops working.  8) If I damage one, I'll suddenly find I can go to the park again!

Yes, I do have both coping and razor saws. Essential modellers kit.