The View Up Here

Random scribblings about kites, photography, machining, and anything else

Archive for September, 2015

New Old Car

Posted by Tom Benedict on 29/09/2015

This has nothing to do with kites, photography, sound, engineering, or anything else I’ve written about over the past several years. It’s a post about a car. Two cars, really.

I’ve driven my Jeep for over ten years. It’s taken me all over the Big Island, and has brought me to all sorts of places where I’ve done photography, kite aerial photography, RC airplanes, and pretty much everything else I’ve put my mind to during that time. I bought it used, drove it, loved it, swore at it, fixed it, and finally sold it to someone who appreciates it for what it is: a good, dependable four wheel drive adult-sized Tonka truck. It’s a fun car, and those were some fun years.

I replaced it with a newer, but no less used Honda Civic. I had a couple of reasons for swapping it out, none the least of which is that my daughter is learning to drive. Jeeps are fun, but stick-shift Jeeps are finicky. I didn’t want her to get discouraged before she ever discovered all the places it could take her. Also, her drive will be considerably longer than mine. Gas mileage finally started to matter.

Any time I buy a used car I try to remind myself that they’re never perfect. They can’t be. Stuff’s going to need fixing before they’re really driveable. I try to budget at least half the purchase cost of the car toward immediate repairs. I looked at a couple of cars and found a nice little diamond (well… a zircon) in the rough: a 2002 Honda Civic LX… with almost 300,000 miles on it. Perfect? No. Not even close. But worth working on? I hope.

On the plus side it’s a stick-shift, just like my Jeep. Unlike my Jeep it has better gas mileage, a better power-to-weight ratio, a working radio, cruise control, and air conditioning. On the negative side after driving it for a couple of days and doing a basic tune-up, I found it needs a new exhaust manifold and catalytic converter (cracked), new wheel bearings on all four wheels (worn out), a new oil pan gasket (leaking), a new timing belt (last one was a hundred thousand miles ago), a new power window motor in the rear right door (broken), a new inside door handle (dying), a new outside door handle (cracked), steering wheel cover, brake pads, wiper blades, etc. But the engine is in remarkably good shape, for all that! While changing the spark plugs I was delighted to see that all four cylinders are fine.

I’d actually budgeted in the cost of a new engine, so as bad as all that sounds it hasn’t added up to anything really unpalatable. My daughter helped me with the tune-up and had her first introduction to working on cars. As the parts start coming in she’ll learn how to service her breaks, replace wheel bearings, work on car doors, replace an exhaust manifold and catalytic converter, and all the other stuff that needs doing. The end result will be another fun car with at least another hundred thousand miles left to go on it and a daughter who may never enjoy working on cars, but who certainly won’t be afraid of them.

– Tom

Advertisements

Posted in Uncategorized | Leave a Comment »

Recording Kite Line Scream

Posted by Tom Benedict on 28/09/2015

Anyone who’s flown a kite and held the line to their ear knows the sound of wind screaming over a kite line. The big plastic hoop winders many kiters use for larger kites are perfect for this. Just barely touch the line to the side of the winder, and the whole thing acts like a loudspeaker. But how to go about recording it?

A couple of weeks ago I built a contact microphone using tips from Zach Poff’s page. The mic consists of a piezo disk, a 6′ length of Mogami microphone cable, an Alex Rice piezo preamp, and an XLR connector. I salvaged the connector from a cable in the to-go pile at work. (Neutrik connectors are still on order.) The cable is the same stuff I’ve been using for my EM172 mics. I ordered the preamp boards from OSH Park, and the components (the list of which can be found on Zach Poff’s page) from Mouser. I got some piezo disks from Mouser as well, but I wound up using one I’d salvaged from a piezo buzzer ages ago.

The only trick when building one of these is that shielding is important. No, let me put that another way: Shielding is IMPORTANT! The first time I tested it, I picked up horrendous 60Hz buzz. I fixed it by insulating the preamp and the piezo disk, then covering each one with copper tape, which I connected to the shield in the cable. Once it was shielded from the XLR to the piezo disk the buzzing went away.

I’d describe all the rigorous tests I performed on it, but mostly I just played. I recorded sound from the supply and return lines on a CTI cryocooler, the sound of a PCC cooler (which is totally different), and the sound of pasta sauce simmering by attaching the contact mic to the end of a spatula and sinking the other end in the sauce. It worked great!

So today I took it out with me while I was doing KAP (and KAV and KAS).

Not much to the setup: Tascam DR-70D, headphones, contact mic, and blue sticky stuff. And a kite and line, of course. (And my hat to cushion everything, ’cause those rocks are like razors!)

Contact Mic Recording

I tried attaching the mic to the line two ways. The first was to stick it on the line itself using Blu Tak (the sticky stuff you get for sticking posters to walls.) This worked great, but braided Dacron likes to stick to the sticky stuff a little too well. When I removed the mic, I was left with gooey bits I had to pick off the line.

Contact Mic on Line

So for my second attempt I stuck it to the carabiner on my ground anchor strap. This worked as well. The mass of the carabiner helped damp some of the higher frequency sounds, leaving more of the bass notes. Unfortunately it also picked up the twisting/creaking/grinding sound of the ground strap.

Contact Mic on Carabiner

I think suspending a carabiner midway along the line would provide the best of both worlds: more bass notes, but better isolation from the ground strap. Unfortunately I didn’t try this. I also didn’t try just sticking the contact mic directly to the winder! Things to do next time.

Still not happy with how Soundcloud embeds in WordPress documents, but in case you’ve never heard kite line scream, here ya go!

Attached to the kite line:

Attached to the carabiner:

Both are mono recordings. (Hey, now I need to do this on a two-line sport kite so I can record in stereo!

On a whim I took a look at the spectrogram of the recording with the mic stuck directly to the kite line.

Line Scream Spectrum

Talk about harmonics! The primary is somewhere between 500Hz and 1kHz depending on the line tension, and the 2x, 3x, and 4x harmonics show up quite strongly.

Fun stuff…

(Told you I wasn’t testing this with any kind of rigor!)

– Tom

Posted in Audio, Kite | Leave a Comment »

Olson Wing and Damped Pendulum Suspension

Posted by Tom Benedict on 24/09/2015

One of the earliest experiments I did with aerial sound was to pop a windjammer on my Tascam DR-05, bolt it into my KAP rig, and send it aloft. I learned a couple of things from that flight: KAP electronics cause gobs of EM/RF intererence, servo jitter is incredibly loud, and the PeKaBe blocks in the Picavet suspension never ever stop making noise. I decided to solve all three problems by skipping the Picavet, using a pendulum, and losing the servos and electronics altogether.

I’ve wanted to built a damped pendulum KAP suspension for a while. My earlier designs involved a parallelogram section with four pivots and a straight section with a single pivot to minimize swing from changes in wind speed. I still think that design has a lot of promise and I’d eventually like to get back to it. For this, though, I only built a single straight section with a single pivot. It’s the easiest way to start playing with pendulum suspensions, and will let me figure out what the real design issues are. The pendulum I built has a pivot faced with a pair of 1-1/4″ disks of metal. I lapped the two plates together and filled the gap with Nye damping grease. The resulting joint is very quiet, smooth, and damps motion. There’s not as much damping force as I’d like, but that’s why it’s a prototype. I’m experimenting! As with any KAP project, as I was putting the finishing touches on the pendulum and loading the pivot with damping grease, the clouds opened up started to rain. So testing will have to wait.

Damped Pendulum Suspension

The other project I finished over the weekend was an Olson Wing microphone array, based entirely off of work by Curt Olson. Since the intent is to fly this from a kite I designed in wind protection from the get-go. The Olson Wing has an upward component to its sensitivity, so I built a 30 degree triangle into the back to angle the mics and baffles toward the source. Both legs of the triangle have 1/4″-20 threaded sockets in them. One allows me to use it on the ground, and aims the array for horizontal use. The other allows me to use it from the air, and orients it for downward vertical use. In both cases the range of motion from the tripod heads let me aim it in any number of directions. Unfortunately the photos I made of the Olson Wing looked horrible, so I’ll have to try again at a later date.

I had a little more opportunity to test the Olson Wing than I did the pendulum suspension. Some tests in 8-12kt wind showed that the furry windjammer does indeed work. On the advice of David Brinicombe from the Yahoo! Nature Recordists’ Group I added a 40Hz low cut filter, and almost all the wind noise is taken care of. Ready to fly!

While testing the Olson Wing I discovered something cool with my light stands. Two of them have 3/8″-16 threaded tips, and the other two have 1/4″-20 threaded tips. The 1/4″-20 stands can take the same mini ballhead I use on my photography pole. Depending on the mood, I can’ use them to stick a fixed angle camera 12′ up in the air, or I can bolt my KAP rig upside-down on top using my pole adapter, or I can stick either my SASS or Olson Wing on top and have a very portable self-contained field kit for doing stereo ambient recordings. Or I could use it to hold a light and modifier, the way it was designed. I love finding new uses for existing equipment!

Two other things happened later in the week that are also moving the kite aerial sound project forward. The first was the arrival of my second sound recorder, a Tascam DR-70D. It’s a hefty little brick of a thing, so I don’t think I’ll fly it on a kite any time soon. But it’ll be perfect for recording sound on the ground, including line scream. Which brings me to the other thing I did this week.

Tascam DR-70D

I built a contact microphone. Zach Poff has a nice article on building a contact mic with an impedance matching buffer circuit designed by Alex Rice. You can wire a piezo disk directly into a 1/8″ (3.5mm) microphone plug and plug it into a laptop or a recorder like the DR-05 or DR-70D. But the combination of the low capacitance of the disk and the low impedance of the recorder input effectively results in a high pass filter that cuts sound below a few kilohertz. This is why contact mics have an unfair reputation of sounding tinny. The impedance matching buffer solves this by presenting the piezo element with several megaohms of impedance, and providing an impedance-matched input to the recorder. The mic I built has remarkably good bass response. So far I’ve only played with it by recording things like kettles boiling and sinks running, but it should be a simple matter to attach it to a hoop winder to pick up the sound off of a kite line.

All in all it was a good weekend and a good week. If the weather holds I should be able to test out almost every combination of ground and air recording, as well as recording line scream. By the end of it I hope to have answered most if not all of my outstanding questions about the how-tos of kite aerial sound, and an idea of what I need to pursue it further.

– Tom

Posted in Audio, Kite Aerial Photography | Leave a Comment »

Jammers, Wings, and Email Lists

Posted by Tom Benedict on 17/09/2015

The fake fur I ordered a while back came in last week, but I’ve had a rotten time making a usable windjammer for my SASS array. I think I know why:

Sound is a pressure wave moving through a medium. When a sound wave strikes an acoustically opaque object the velocity goes to zero, but the pressure doesn’t. It increases. It’s that increase in pressure that provides the 6db of gain that boundary mics get over conventional mics.

Wind is motion of air molecules at an average velocity. Again, when wind impacts a surface like a wall or a kite, that velocity drops. But the pressure doesn’t. It increases. A lot. This is what makes kites fly at high angles of attack. But it also means that no matter how much fuzzy fur I stick in front of the mics on my SASS, the kind of wind I need to do KAP will almost certainly overwhelm the pressure limits of the mics. RATS!

I’m still pursuing a good windjammer for my SASS because I know it’s been done and I like using it on the ground, too. But for kite aerial sound work I’m moving my focus toward another design: Curt Olson’s Wing. A couple of things about his wing design make it attractive for KAP. First, it’s a lot easier to build a windjammer for an Olson Wing than it is for an SASS. The SASS was designed for use indoors. Curt’s a field recordist, so outdoor use was part of his design work. (You can see the cages for a windjammer on his page.) Second, the design includes a big flat plate that can be faced into the wind to help protect the mics from the direct wind blast. This means only recording subjects directly below or downrange of the kite, but it’s a start.

While trying to figure out the problems I was having with the windjammer, I ran across Trevor Owen deClercq’s master’s thesis titled “A More Realistic View of Mid/Side Stereophony”. The thesis itself focuses on a stereo recording technique pioneered at E.M.I. called Mid/Side Recording, as the title suggests, but the introductory material also discusses psychoacoustics: how humans process sound. At low frequencies we use phase differences to locate sound. At higher frequencies our heads act as a partial baffle, which attenuates sound coming from the far side of the head from the ear in question. This lets us use differences in sound level to locate sound. At mid frequencies we use a combination. (deClerq states that we don’t do it particularly well, but that we do do it.)

Later on I ran across this study of boundary microphones which echoed deClercq’s introductory statements in a section on the Crown SASS and its derivatives. The mic spacing of the SASS let it pick up phase differences at low frequencies, and the foam block acts as a partial baffle at higher frequencies, which results in different sound levels reaching each of the mics, depending on the direction of the sound source. This explains why the stereo image created by the SASS works so well: it’s how we were designed to hear.

That study also touches on some of Curt Olson’s earlier spaced boundary mic designs, though I think it pre-dates his wing design. Now I’m curious if it’s possible to add a foam block to his wing design to help it behave more like an SASS without incurring the penalty of having to make a windjammer that’ll survive kite-flying wind speeds. As soon as I finish my wing and fit it out with a proper windjammer, I’ll give this a try.

In an attempt to answer this and other questions I joined two Yahoo email lists over the last week. The micbuilders list focuses on microphone design and construction. The naturerecordists list focuses more on field recording equipment and techniques. There is, needless to say, a great deal of overlap between the two. And to my delight, between the two lists I’ve run across posts by Vicki Powys and Curt Olson, both of whom I’ve mentioned several times, along with David Brinicombe, inventor of the fuzzy windjammer, Zach Poff, whose web site started me off on the whole Primo BT-EM172 based microphones, Gene from Frogloggers, the place I ordered my mics from, and Klas Strandberg, owner of Telinga Microphones, whose EM-172 based parabolics I’ve been drooling over since I dove into this whole sound thing. I’m still soaking it all in. I haven’t posted a word to either group.

So despite my utter failure at making a KAP-ready windjammer for my SASS, it’s been a pretty good week. But man that learning curve still looks like a sheer wall.

– Tom

Posted in Audio | Leave a Comment »

Pseudo-SASS Testing at Kiholo Bay

Posted by Tom Benedict on 09/09/2015

Last weekend I took my pseudo-SASS back to the south end of Kiholo Bay to make another attempt at recording wave sounds. The north end of Kiholo Bay has been one of my favorite places to do kite aerial photography, and has a soundscape I haven’t even begun to explore. The south end, though less photogenic in some ways, has some real treats when it comes to sound.

One that I’d tried to record previously is a tiny beach composed entirely of rocks about the size of a fist. The beach is no more than six feet wide, and is framed by heavy basalt rock. Waves hitting the beach have the characteristic crash-boom-bam of waves on rocks, followed by the sound of a wet rockslide as the fist-sized rocks ride the wave back out. In my previous attempt the range of frequencies presented by the waves and the rocks, combined with the tunnel-effect of having recessed microphone capsules, created a sensation that made the hair on the back of my neck stand up. Not pleasant. If ever there was a test for the flush-mounted mic bodies, this was it.

Unfortunately the other problem I ran into on my previous attempt was still there: wind. I haven’t made a windjammer for this setup yet, and even a doubled-up fleece jacket wrapped around the SASS didn’t cut it entirely. Still, I got several bits of usable audio. The flush mounted mic bodies seems to have fixed the tunnel effect I was getting, at least. I think the mid range may still be a little harsh, but it’s getting closer to what I’m after.

The other problem I ran into was a helicopter pilot who kept flying over Kiholo Bay. I can’t blame them, whoever they are. It’s beautiful there. But half my takes end with my growling, “Helicopter…” Even without a kite line in the air, I always seem to have to worry about helicopters!

So far all my testing has been relatively close to the subject. In the case of the rock beach my microphones were about ten feet from the water. It’s still my intention to use this in the air, though, in which case the mic-to-subject distance will be closer to a hundred feet or more. Unfortunately I don’t have a good way to test this without actually flying the microphones. As soon as I have the wind protection issue sorted out, I intend to give it a try.

– Tom

P.S. I’m still not pleased with how Soundcloud’s embedded player shows up in WordPress. I’ve seen some really nice, small, not over-the-top versions of their player. I just can’t figure out how to make it do that. If anyone knows, clue me in!

Posted in Audio | Leave a Comment »

Flush Mount Mic Bodies

Posted by Tom Benedict on 06/09/2015

In my previous post I mentioned that the mic bodies I’d made were coloring the sound of the mics in the SASS. I figured in a couple of weeks I could make new mic bodies that would mount the BT-EM172 capsules flush with the end, and recover some of the bass I was missing with the existing bodies.

Myeah… I couldn’t wait that long. After work Friday I made new ones.

Flush Mount Mic Body

I wanted to make them with the same form factor as the original ones I’d made out of aluminum. That would let me mount them in the SASS without having to modify it. This started life as a 3/4″ black Delrin round, turned down to the right outside diameter and bored out. No screws in this design. I prototyped it on my mono mic, then made bodies for the SASS mics. Everything loads from the front, and then the mic is pressed into the body. It’s a pretty snug fit, so I hope I don’t have to take them out any time soon.

SASS - Flush Mount Mic

The new mic bodies went in just fine, and now I’m finally operating my SASS as a stereo boundary microphone array. YAY!

I’m holding off on replacing the bodies on the pair of lav mics I made. Without the screen mesh and the rubber shock mount, there’s not as much need for room inside the mic body. I could make this a lot less chunky and a lot more like a lavalier. I want to think on the design before cutting.

Meanwhile everything’s back together. Time to get out and record more waves!

– Tom

Posted in Audio | 3 Comments »

Pseudo-SASS Array

Posted by Tom Benedict on 03/09/2015

Following the successful testing of the new mics, I turned my attention toward building a pseudo SASS array. My prototype design was a copy of a copy of a copy of… well… a copy. This becomes important later, because it’s lessons learned from one of those copies that drove part of my final design. First, a bit of history, mostly gleaned from Vicki Powys’s web site:

The SASS, or Stereo Ambient Sampling System, was designed by Michael Billingsley in 1987 for Crown International. It was (and still is) aimed at recording music performances, audiences, and other subjects that lend themselves to stereo recording. It offers relatively strong stereo separation in a small package. Crown sold the SASS with microphones built into the system, which worked well for its intended purpose. But the original microphones exhibited a high noise floor, and weren’t well suited for quiet subjects. Lang Elliott and Michael Billingsley modified a Crown SASS to work with higher-end microphones, and Walter Knapp took that concept and offered re-tooled Crown SASS units that would take, among other mics, the Sennheiser MKH20. This made it a viable choice for recording quiet ambient sounds and field recording.

More variations tailored to field recording continue to be made. Rob Danielson’s PBB2N, built out of wood and PVC pipe along similar lines to the Crown SASS, takes the same range of microphones as the units made by Walter Knapp, and offers better bass response. Vicki Powys, concerned about the weight of a wood array, took that concept and made her own version out of dense closed-cell foam (pool floaties) using Primo BT-EM172 capusles. After building her foam SASS, she did side-by-side tests with it against a Crown SASS with MKH20 microphones. The performance of the two were remarkably close.

The idea behind the Crown SASS, Rob Danielson’s PBB2N, and Vicki Powys’s SASS-LN2, is to baffle the microphones so that the array acts as a pseudo-binaural stereo pair similar to the human head. The wings act as boundary surfaces, and the foam baffle in the center partially absorbs sound from unwanted angles. The end result is a higher gain than a bare microphone, and considerably better separation than two microphones arranged as an X-Y pair. This photo of a Crown Audio SASS-P MkII was a later model that used PZM mics, but the overall shape didn’t really change much from the original SASS:

I built my prototype based off of measurements I took from a photo of an original Crown SASS, scaled to the overall size of Vicki Powys’s SASS-LN2. I wanted to test the idea before leaping in and building an airborne unit, so I built the prototype out of 1/2″ foam core board. The unit provided quite good stereo separation, and had considerably higher gain than the built-in mics on the Tascam DR-05, but it lacked bass punch. I wanted to figure out why before going from prototype to final design.

One clue came from another of Rob Danielson’s designs: PBMB2. His design calls for significantly larger wings than the original Crown SASS. The larger wings provide a larger boundary surface for the microphones to work with, and therefore provide gain at lower frequencies than the original from Crown. Since I’m planning to use this in the air, cross-section is an important design consideration I need to take into account: larger objects are more easily affected by the wind than smaller ones. Rather than using the larger wings from Rob Danielson’s PBB2N array, I stuck with the dimensions of the Crown SASS.

Another clue came from a set of posts on the micbuilders Yahoo group: Electrets mics need to be mounted flush with the end of their enclosures. Mine aren’t. They’re recessed several millimeters into their tubes and hide behind a layer of stainless mesh. Recessing the mics this way colors the sound they pick up.

Mono Mic Assembled

Unfortunately I learned this late in the game, after I’d already built all five of my mic enclosures as well as my airborne pseudo-SASS. Before going out and designing all new enclosures I decided to test this for myself. I disassembled one of my mics and tried sliding the mic deeper into the tube. I found that the more recessed it was, the more mid-range gain I got, and the less bass. Finally I pulled it out entirely, bare to the world, and tried it that way. I could easily tell the difference. There was a lot more bass, and the mic sounded a lot less tinny. (Hey, if I can tell the difference, it’s HUGE!) Time to design all new mic enclosures!

The last clue came from the folks at DIY Boundary Mics. They ran some tests on the array built by Vicki Powys and the modified Crown SASS with Sennheiser MKH20 microphones. Rob D. (Rob Danielson?) from DIY Boundary Mics noted that Vicki’s foam array lacked some of the lower frequency response the Crown SASS / MKH20 combination had. He attributed it to the soft nature of the boundary surface (foam). Paul Jacobson at DIY Boundary Mics ran a comparison between Vicki Powys’s array and a similar one made of untreated wood, similar to Rob Danielson’s array. The untreated wood array recovered some of the bass lost in the foam array. This agrees with Rob D’s conclusions about the hardness of the boundary surface.

Which leads me back to the prototype I built out of foam core. The outer surface of the foam core is relatively hard, but the foam itself is acoustically thin, and the foam core board has a high natural frequency. I’m guessing that some of the lack of bass punch in my prototype can be traced to the material I used to build the array and the lack of damping material in the array’s inner cavity. I needed something better.

Years ago I made a kite aerial 4×5 film camera out of birch plywood. I never was completely happy with the photos it produced, but it turned out super pretty. Since Rob Danielson was making boundary array mics out of wood, and since the wood SASS had better bass performance than Vicki’s foam one, I figured I could build mine out of wood as well.

I already had some 0.200″ baltic birch plywood left over from the 4×5 camera, so that’s what I used for the array body. The woodwork came together relatively quickly, but I couldn’t finish sealing up the box until I had the damping material glued in place. Here’s one problem with living on an island: no one sells acoustic materials. Rob Danielson used carpet padding in his PBB2N, so I went that route. Here’s another problem with living on an island: stores that sell carpet padding don’t like breaking up rolls! I finally wound up at Home Depot. I waited patiently in the flooring department until someone could help me. I’d already been to several stores, and had received more than my fair share of blank stares when I asked for one foot of carpet padding. I wasn’t expecting much.

The folks at Home Depot surprised me! When I asked for such a small amount, the guy in flooring said, “You building a speaker box or something?” “A microphone array, actually, but it’s the same idea.” “Cool!” He was super helpful, and sent me home with my one foot roll.

Eventually my DIY-SASS came together. It’s shown here with my original mic enclosures, but in the next few weeks I’m planning to swap them out with flush mounts:

DIY-SASS

It uses the same Primo BT-EM172 capsules as Vicki Powys’s array, though she used four and I only used two. The covering for the baffle gave me fits until I finally bent to common wisdom and used sheet metal. (I’d wanted to make it out of the same plywood I’d used for the rest of the SASS for cosmetic reasons, but I ran into structural issues.) The hardware store sold 6″x12″ aluminum for almost the same cost as 6″x12″ polished stainless, so I went with the stainless. But I had to bead blast the outside of it to keep myself from going blind when I took it out in the sun.

DIY-SASS Front

There are a lot of screw holes on this, both to hold the baffle cover in place and to attach the array to a tripod (or a KAS rig!) I’ve seen too many wood screws strip out over time, so I epoxied T-nuts into each screw hole to provide machine threads. Since  I do a lot of my KAP along the coast and plan to record sound in that environment as well, I went with as much stainless hardware as I could. Even so, I’m going to have to open the unit periodically to check the wiring for salt contamination. (One more reason to be glad I used T-nuts!)

DIY-SASS Bottom

Since I’m planning to use this on the ground as well as in the air I didn’t want to wire in a dedicated cable. I’ll only need 2-3′ for aerial work, but on the ground there’s good reason to put some distance between a microphone and the recordist. Having a way to swap cables seemed like a good idea, so I wired it with a 1/8″ TRS jack so I can use the cable of choice, depending on what I’m doing.

I’ve now used my pseudo-SASS in the field several times. I was pleased to find that the heavier construction worked, and that I got back a lot of the bass punch I’d lost with the foam core prototype array. I’m looking forward to trying it with the flush mounted microphone enclosures to see how much more bass I can recover.

Meanwhile I’m facing yet another design problem. Like any microphone, my pseudo-SASS array suffers from wind noise. I learned this the hard way while trying to record the sound of waves crashing on rocks.

In Dire Need of a Windjammer

The wind buffeting was more than the mics could handle, so I wrapped the whole thing with my folded up t-shirt. Even that wasn’t enough to cut the wind, so none of the files were usable. Bummer!

Unfortunately the wind there was nothing compared to the wind I’ll get when I hang this thing from a kite line. And since Rycote and Rode don’t make windjammers for DIY mic projects I’ll have to build my own. My last act of the weekend was to order a yard of 2″ pile 100% polyester artificial fur with the loosest backing I could find. As I finished checking out I couldn’t help thinking yet again, “You’re getting in deep, man.” I fear I’ll learn how to sew fake fur before I learn how to make my own kites.

– Tom

Posted in Audio, Engineering | Tagged: , , , , , , | 3 Comments »