Now for the icing on the cake – the development team has linked in the FFmpeg video libraries and given REAPER the ability to do simple video editing. I’m totally happy with my video editing system since I moved to Edius Neo 2.5, but when I played around with video in REAPER I realized that this is a tool many musicians want and need.

Many of us like to post simple performance videos on YouTube – not big production numbers but simple clips showing off our latest tune or instrument or technique. And we want to do this on a budget. We use inexpensive pocket video cameras, and they have at best mediocre sound quality. Many of us also have a fairly high quality recording system of some kind. Now with REAPER we can create our videos just like they do it in the movies – recording the sound on a high quality audio system positioned for the best audio quality while capturing the video at the distance needed for framing and perspective.

Using video in REAPER is a snap. First, go to the CockosWiki Video Support page for instructions on adding the FFmpeg libraries to the REAPER program directory.

Once the FFmpeg libraries are in place, just open the video file like any audio file, or drag and drop from your file browser into the REAPER track window. I’ve tried clips from three camcorders so far, the Kodak Zi8, the Flip Ultra HD, and the Sanyo Xacti HD2000. REAPER handled all of them with ease. Only the .mts files from my Panasonic Lumix TS2 failed to open, and I was able to convert them to an AVI that REAPER liked.

If I’m shooting video around my studio, I’m all ready to record audio into REAPER, so there’s another step out of the way. If I’m shooting on location it’s a snap to bring the recordings back to the PC and drop them into REAPER. The whole process is so easy that instead of writing detailed instructions I decided to simply shoot a video of shooting a video and demonstrate the syncing process.

So that’s how easy it is. Drag and drop, drag and drop, trim, drag and drop, trim, and render. When I think of the hours I’ve spent calculating frames in Avidemux, or waiting for Premiere Elements to redraw, or being told by Windows Movie Maker that it can’t deal with my file …

Here’s the video that I created in REAPER in the process of the tutorial. The Flip would have been happier with more light, for sure, but the quality you see in this video is right there with the original from the Flip. And the audio is in a whole different, and better, league. Naturally, since I was working within REAPER I could have easily added effects, applied EQ, worked over the audio to improve the result.

One consistent recommendation was the Schoeps line of microphones. I was lucky enough to find a deal on a pair of used Schoeps CMC64s (CMC6 modular bodies and MK4 cardioid capsules) a few years ago, and even though they were fairly expensive I bought them because I knew that once I had a pair of Schoeps, I could no longer blame the microphones for my less than satisfactory results.

Now, a few years older and hopefully wiser, I have come to realize that the difference between most mics is pretty subtle, the difference between preamps and a/d converters is even more subtle, and the big differences come in the instrument, the performance, and the room. Of course, believing that equipment has a minor impact has not kept me from buying more gear. Mics and audio interfaces, monitors and headphones, sometimes I just can’t resist trying something new.

A New Toy (er, Tool)

Since I’ve discovered the fun of videography I’ve found even more gear to consider. The recent Homebrewed Music comparison of stereo mics for the Kodak Zi8 stimulated my interest in a microphone that is widely recommended as an excellent medium priced tool, the Rode NT4. This mic combines the two capsules and electronics of the Rode NT5 small diaphragm condenser in a single body visibly similar to the NT3 model. This mic includes the option of using a 9 volt battery for power if 48 (or 24) volt phantom power is not available. It also comes with adapter cables providing either a conventional pair of XLRs or a 1/8″ stereo miniplug for cameras and field recorders. The NT4 doesn’t come up on the used market very often, but with a little patience I found one at an attractive price and added it to my collection.

One thing about high end (that is, high priced) gear like the Schoeps mics, in my little home studio they tend to stay in the drawer. Since Schoeps prices have gone up steadily for the last few years, my mic collection has become an investment as well as tool set, and I’ve become a bit protective of the “good stuff.” If I need a mic for a quick recording, I’m much more likely to pull out a less expensive unit, and the NT4 has been getting plenty of use lately. It’s simple to set up, useful with various recording systems, and sounds pretty darned good to me.

Shootout Time

In fact, it sounded so good, I started wondering how it might compare to the hallowed Schoeps CMC64. Once I listened to them side by side, would I still think the NT4 sounded darned good? I’ve gone into some detail on the procedure needed for a meaningful mic test, and I’ve done some other comparisons. But a recent flurry of “what is the best mic” postings on various guitar forums triggered a desire to evaluate the Rode and Schoeps side by side.

Naturally, I set the mics up as close as possible to the same position, using the same stereo arrangement. The Rode is constructed as a fixed X-Y array, so I used a stereo bar to mount the CMC64 pair in the same configuration.

Schoeps CMC64 and Rode NT4

I connected both mic systems to the Echo Audiofire Pre8, and set the gain by eye. Next I setup Reaper to record two stereo tracks, and applied the Sonalksis FreeG meters to each track. This excellent plugin let me know that my preamp gain settings were within a couple of db of each other, as close as I am likely to get with the small gain controls of the Pre8. After recording, I pulled the files into Adobe Audition where I use the Group Waveform Normalize function to set the perceived average levels to – 12 dBFS.

It’s All in the Listening

Just listening to the tracks they sounded pretty similar, so I pulled the tracks into foobar2000 to use the ABX utility. Under this audio microscope I quickly discovered that I could recognize the files as different. The Rode recording was very (and I mean very) slightly “lighter,” less full than the Schoeps track. When I checked the frequency response curves I saw that the Rode had a reduced bass response and more pronounced emphasis on the highs compared to the MK4 capsule of the Schoeps.

NT4 frequency response showing low cut and high boost

CMC64 frequency response. more linear than the Rode

I immediately wondered if I could reduce the difference with some EQ. Back into Adobe Audition, where I used the Parametric Filter, adjusted to the opposite of the Rode frequency response graph, to process the Rode track and save it to a new file.

After this processing, I could no longer tell the files apart when I ran ABX in foobar2000. In the first test I made six consecutive correct choices with no incorrect ones, a better than 85% certainty that I could tell them apart. When I compared the Rode file with EQ to the Schoeps file, my results fell apart, with three incorrect choices out of four tries.

Based on this test, it seems that a little digital EQ can make a Rode NT4 sound like a Schoeps CMC64 when recording me playing solo acoustic guitar (in this room on this day). This is not to say that an NT4 is “as good as” a pair of Schoeps mics, of course. The Schoeps modular system supports many different capsules for different pickup patterns and uses. And a pair of mics give much more flexibility in placement than a fixed X-Y stereo mic. But in this one very limited use, simple stereo recording of a solo acoustic guitar, the NT4 reduces the complexity and cost while delivering sonic results that I find completely satisfactory.

Try for yourself. Here are the files (these are CD spec 44.1 khz 16 bit PCM wave files, so they’re large – about 14 Mb each):

Download O.wav
Download P.wav
Download Q.wav

One of these is the Schoeps, one is the Rode without EQ, the other is the Rode with EQ. Ideally you’ll use an ABX tool to listen carefully and determine if you can tell the files apart. However you choose to listen, post a comment here with your impressions and I’ll email you the identity of the three files.

***** June 17, 2010 Update *****
When I posted links to these files on the Acoustic Guitar Forum the folks there quickly zeroed in on the Schoeps CMC64, so I went back to foobar2000 ABX and, sure enough, once I found the right place to listen, I could hear the difference between the Rode, even with EQ, and the Schoeps. Which goes to demonstrate an important aspect of ABX testing – it’s quite possible to miss differences, due to tiredness or predisposition or some other cause.

By separating the mic from the camera, I should be able to position the mic for optimum sound while placing the camera for the visual effect I want. Of course, I can do this wihout an audio input on the camera by a technique called parallel recording, that is, recording on a separate audio system of some kind. The familiar clack of the slate at the start of a movie sequence is used to make it easy to synchronize the picture and sound, and this technique works very well for my homebrewed videos as well. Still it’s very tempting to think that recording directly to the camera is an easier way out, with camera audio every take and every edit lining up without any extra effort.

I’ve been interested in the range of options for attaching a mic to the Zi8, and back in December I went on a little mic shopping binge. Between my storage drawer, Ebay, and Sound Professionals I gathered a collection of mics in a range of prices. But I was struck with a glitch in my Zi8 audio, which required several round trips to attempt repair at the East Coast contract repair depot. Eventually Kodak agreed to replace my camera, but by then I was on a lovely trip to Hawai`i.

Test Design

Now that I’m back I’m ready to offer up some test clips. At first I planned to video a number of brief samples of guitar and vocal, which was very troubling to me. I strongly believe that audio sampling should be done with a single performance and carefully volume matched, in order to reduce the number of variables in the sample. As much as we think otherwise, humans just cannot judge subtle (or even not-so-subtle) differences without careful controls. My aha moment came when I realized that I was only testing audio, not video, so I could use a recorded source to get a repeatable performance. Focusing on audio only also allowed me to upload the much smaller audio clips, so the comparison will be quicker and easier.

For level matching I decided to take the easy way out and simply normalize the files. Normalizing raises the peak of a file to a given level, in this case I chose -3 dBFS. I adjusted levels like this so our ears won’t be fooled by level differences, but these samples hide the differences in the real recording you’ll get if you use one of these mics. So I’m including the original sample as well. Remember that I adjusted the sensitivity of the Zi8 for each mic, so the volume levels are affected by that even in the original, un-normalized samples.

I first created a test recording in Reaper, some slack key guitar naturally. I recorded in mono with an Audio Technica AT4050 in cardioid pattern. Then I added a bit of narration. All camera mics I know about, and many accessory mics as well, are omnidirectional. There are plenty of reasons why an omni is a good choice, but real trickery is required to get a good stereo image with omnis. So I threw in a bit of movement in the stereo field to evaluate channel separation. I arranged the narration and the stereo test ahead of the music and adjusted levels.

I placed all the mics very close to my normal listening position and played back the test recording through my normal monitoring chaing – Echo Audiofire 8, Hafler P3000, Dynaudio BM6p. A Radio Shack SPL meter showed 74 db C weighted at the mic position.

As I mentioned, I adjusted the sensitivity of the Zi8 for each mic. In each case I adjusted the sensitivity to the highest level that did not show any red. I label the default sensitivity as 0, lower sensitivity goes from -1 to -5 and higher goes from +1 to +5. I wound up using the whole range in this comparison.

Test Clips

Here’s the reference recording. It won’t get any cleaner than this.

or download ref.mp3

I used the Zoom H2 as the mic in my first experiments with the Zi8, so I included it in this comparison. It’s also handy because we can record with the H2 and the Zi8 at the same time. Even though the signal in the Zoom was very low and pumped up with a lot of digital gain in the normalization process, it is quite a bit cleaner than the Zi8. I set the Zoom to M Mic Gain because tests have shown that the H setting adds noise. This still resulted in a rather low level, so raising it also raised the noise as well.

or download h2p.mp3
Original versions, no normalization:

or download oh2p.mp3

I used the rear mics on the H2 so I could operate the controls on the front of the unit. As a result the stereo left and right are backwards in both the parallel clip and the Zi8 clip. Here’s the output of the H2 headphone jack recorded on the Zi8 with sensitivity set to -3.

or download h2v.mp3
Original versions, no normalization:

or download oh2v.mp3

If you’re like me you’ve been fooling with recorders for a while, maybe going back to cassette tapes. Perhaps, like me, you have some kind of little mic in a drawer somewhere. My drawer mic is labeled www.reactivesounds.com but the web site is a dead end now. I bought this to use with my minidisc recorder a few years ago. The mic is omni, no cable (requires an female to male extension), and has been repaired with superglue. I used -2 sensitivity for this mic.

or download drawer.mp3
Original versions, no normalization:

or download odrawer.mp3

I’ve used Sound Professionals http://www.soundprofessionals.com/ for these kinds of recording gear for years. I used one of their T-mics for years with my minidisc, but somehow lost it. They still sell a mic with the same model number, SPSM-1, but it doesn’t look much like the mic I remember. I set the Zi8 to -3 sensitivity for this mic.

or download spsm-1.mp3
Original versions, no normalization:

or download ospsm-1.mp3

The SPSM-15 is the least expensive single point stereo mic sold by Sound Professionals. It appears to have a higher low frequency cutoff than the SPSM-1, and/or lower sensitivity. As a result I set the Zi8 sensitivity to -2.

or download spsm-15.mp3
Original versions, no normalization:

or download ospsm-15.mp3

The AudioTechnica AT825 has been a popular single point stereo mic for many years, but was recently discontinued. The replacements are much higher in price, so it might be worth watching for used examples of the AT825 on Ebay or Craigslist. It seemed perfectly matched to the Zi8 and worked well at the default sensitivity setting.

or download at825.mp3
Original versions, no normalization:

or download oat825.mp3

I was impressed with the performance of the AT825. I was very disappointed in the AudioTechnica Pro 24. Although it looks much more impressive than the T-mics from Sound Professionals, it was very low in output, requiring that I set the Zi8 to the maximum +5 sensitivity.

or download atpro24.mp3
Original versions, no normalization:

or download oatpro24.mp3

Let’s Look at the Video

Let’s finish off with some actual video. Be careful with comparisons, but perhaps there will be some blatant differences we can take away. When I framed the shot to include the whole guitar the camera wound up about 5 feet from the instrument. I adjusted the Zi8 sensitivity for each mic using my normal procedure – the highest setting that did not show any red squares.

I had a little fun with my new Edius Neo 2.5 software putting together a compilation of the mic demonstrations.

All these mics sound better here than in the audio test with the recording, but they still show their basic characteristics. The camera mic picks up a lot more room, as it must at that distance. And since the room is a boxy little thing, the recording sounds small and boxy.

The H2 in this clip is very slightly overdriving the Zi8, to my ears. The slightly dark voice of the H2 comes through as well. The Sound Professionals SPSM-15 does a pretty decent job for very small bucks. I failed to mention in the video that the sensitivity on the Zi8 is down to -3. This means the SPSM-15 is quite sensitive, so it might be a problem if your source is loud. To my ear the AT825 is the winner. I like the clear presentation. I’m sorry I didn’t do a better job of balancing the channels.

I hope these comparisons are useful. I plan to try these mics with a different camera in a future post.

The Best Tuner Is Built-in

It’s hard to appreciate just how convenient this device is. First, it’s always handy, your picking buddy can’t borrow the tuner unless you lend him the whole guitar!! You’ll never put it down and forget it, never leave it behind at a gig, never have one of the kids play with it and run the battery down. Another hassle you avoid is the visibility problem. The lights are bright and the tuner is in a nice dark space inside the instrument, so visibility is better than any other tuner I’ve ever used.

The tuner is fully chromatic, that is, you can tune to any standard pitch, not just standard guitar tuning. This is very handy for my slack key because we tune to flats and sharps as well as natural notes up and down the scale. The Wittman has a clear marking for the sharp/flat interval between the natural scale notes.

It’s Not Perfect

There are some limitations to the Wittman MiniTuner. The reference pitch is not adjustable, so it doesn’t have the ability to match an out of tune piano or horn. The tuner senses body vibrations, so it can be difficult to use in very loud conditions where your instrument is affected by the sounds around you. If your bass player is tuning up or noodling at performance volume the Wittman is going to be very hard to use. The other big issue is that you wind up buying a separate tuner for each instrument. This makes the Wittman an unhappy choice for those on a strict budget.

I Got A Freebie – It’s Going in a Uke

Perhaps I should economize, but the darned thing is just addictive. In fact, many of my friends, even those who scoff at first, wind up installing one of these tuners. Apparently many people have mentioned my name when buying a Wittman MiniTuner, and Mr. Wittman showed his appreciation by sending me a pair of tuners. I decided to try installing one of them in my `ukulele.

This one is a lovely little Pono tenor cutaway, mahogany and spruce.

Pono Tenor `Ukulele, cutaway in mahogany and spruce

Pono is the off-shore brand of the Ko`olau Guitar & Ukulele Company, the Kitakis family of O`ahu. My Ko`olau tenor is a treasure and my favorite uke, but I’ve always had a guitar geek’s desire for a cutaway tenor with a pickup, and this Pono fits the bill perfectly.

Here’s a video of the installation process.

Now that I’m reviewing the process I can see that I did it quite the hard way. The sticky-back velcro attachment system makes it easy to fit just one half the velcro first. With the velcro in place it’s a snap to install the battery holder and tuner. Still, even if I didn’t demonstrate the best way, I hope you can see that it’s a pretty simple job to install one of these. And if you’re like me, once you try it, you’ll be hooked.

For a number of years builders have worked on more stable replacements for the wood in our guitars, and now we have plywood, aluminum, and a range of composites including fiberglass, kevlar, and carbon fiber. In fact one of the pioneers in carbon fiber guitars, Rainsong, started their business in Hawai`i and attracted a number of local players to their instruments.

Composite Acoustics is a relatively young company that started with a dreadnaught and bluegrass focus, but thanks to my encouragement (hey, I wrote them an email) they’ve developed some very fingerstyle friendly models, especially the new OX body style.

I’ve been very curious about the Composite Acoustics OX since I saw the first pictures, and when I found a used one offered in one of the guitar forums I visit, I snapped it up. Here’s my new baby in all its carbon fiber glory:

An old leather strap holds up the high tech carbon fiber OX.

The body on this beauty is pretty slick, so the soft old leather strap helps hold it in position. Note the perfectly smooth and comfortable (if graceless) merging of the neck, body, and cutaway:

The neck flows smoothly into the body

I like the simple detailing on this very reasonably priced guitar. The tuning pegs are some I’ve never seen before but they work nicely. I would prefer a bit lighter peghead, but that’s true of almost every guitar I try:

The tuners are attractive and work very well

The black woven look of carbon fiber is so hip now that you can buy fake carbon fiber decorative parts for your car or motorcycle. The drama is evident in this shot of the top of the OX. This is the simplest, least expensive finish offered by CA, they call it Raw. The bridge, saddle, and bridge pins are all fabricated from composites. The sound hole decoration is a thin sheet of brushed aluminum that floats above the weave. You can catch a glimpse of the Wittman Mini tuner peeking out of the soundhole. I’ve installed these in almost every guitar I own:

Dramatic weave of carbon fiber, a Wittman Mini tuner in the soundhole

I was hoping for a lot when I bought this guitar, and I’m not disappointed. I think Composite Acoustics has figured out a bunch of stuff very well to create the OX Raw. Here’s a bit of video, an old hula song called Papalina Lahilahi showing some of the fun of playing this lovely instrument:

The guitar is tuned to taropatch F, open G tuned down one whole step. From low to high: C F C F A C. The sound on this video was recorded on the Zoom H2, you can see the top of it just edging into the bottom of the shot. I pulled the audio file into Adobe Audition and tweaked the EQ just a bit, but there’s no reverb, compression or other effects, you’re hearing the sound of the guitar.

The only bad thing about finding a nifty new item like the OX is the sudden urge to explore other Composite Acoustics instruments, like that cute little Cargo travel guitar …

I’m pretty pleased with this new camcorder. Let’s look at the pros and cons:

It’s Pocketable

It’s compact. It’s right on the edge of being too big for a pocket camcorder, but I’d say it still works. Here’s a shot of the Zi8 next to a Motorola Razr:

Zi8 and Razr Side by Side

I’m embarrassed that I shipped my Flip Mino HD off to a friend before I did this comparison so I can’t show them side by side or show comparison videos.

Another factor that makes a good pocket cam is a low price, and the Zi8 does fine on that score. And while the user interface is a bit more complicated than the Flip or Vado cams, the Kodak has a bit more flexibility as well. The options are easily accessible with the control layout. It takes decent stills along with several video formats.

It’s Expandable

Compact Flash memory continues to ride the price curve down, down, down, so the ability of the Zi8 to use accessory cards lets the user take advantage of bargains when they appear. I often shoot a set of music that continues for an hour or longer. A 16 Gbyte SDHC card combined with the included AC adapter makes the Zi8 a great tool for my kind of shooting. For places where AC isn’t available, the battery in the Zi8 can be replaced with a fully charged spare.

The other big feature for my use is the stereo microphone input. When I shoot my solo guitar performance videos I usually record the sound separately, then synchronize the audio and video in post production. Recently I’ve been using a Sanyo Xacti HD2000 camcorder that has many great features including an audio input, so I’ve been able to record direct to the camera using high quality mics. The HD2000 is a just a little too bulky to be a true pocket cam, and it busts out of the “disposable” price range by quite a bit as well. Now with the Zi8 I have an affordable shooter that I can feed audio into.

The reason for needing an external mic is simple physics – the camera has to be some distance from the subject, but the microphone needs to be close to the subject, at least for the kind of stuff I do, recording solo acoustic guitar in less than optimal rooms.

Here’s a picture that gives an idea of the problem:

Zoom H2 audio into the Kodak Zi8 camcorder

The room in this picture is a screened lanai, or porch, in Kailua. Beautiful Kailua beach is about 50 yards away, so the surf is always audible in the background. The trade winds are usually blowing through the surrounding trees, and a fairly busy street goes by the back door. There’s no soundproofing or room treatment of any kind, so getting a decent sound is a challenge. Notice how far the camera is positioned from the guitar – 5 to 6 feet away. At this distance, the guitar is not very loud, while the surrounding waves, wind, and cars are quite obtrusive. But with the audio input in the Zi8, I can use the Zoom H2 as a stereo microphone, and place it about 1 foot from the guitar. Here the signal to noise ratio is much better.

But It’s Not Perfect

Naturally, the Zi8 has flaws, some minor, some a bit more troubling. I never thought about the flat bottom of the Flip Mino HD until I tried to position the Zi8 on a table without a stand. Oooopss. The Zi8 has a rounded bottom that requires some kind of support for any placement.

The feel of the Kodak is a bit flimsy compared to the Flip, but those flimsy bits give access to a replaceable battery and various connectors. The zoom capability seems like a bit of a joke to me, it works in digital mode so it impacts picture quality, and it operates in discrete steps that would be very distracting during a shot. The bundled Media Impressions software has a number of issues, judging by the discussions at the support forum but I was able to title and trim one clip with it.

**EDIT Nov 19, 2009**The italicized comment that follows talks about my problems with the AGC on the audio input, but I’ve since learned that there is no AGC. Ooops!! I must have been overloading the input pretty heavily. I plan to continue to explore the audio input in a future post.**End of EDIT**

The biggest negative issue for me is the AGC, automatic gain control, on the audio input. This function raises the gain when sounds are low, which raises the background noise. It also makes level setting more difficult. I don’t know if it’s possible, but I’m hoping for a firmware upgrade someday to turn off the AGC. In the meantime, I’ve come up with a setting that seems to get the job done, by setting the Zoom H2 to low sensitivity and turning down the audio sensitivity on the Zi8.

So How’s the Video?

As I mentioned at the beginning of this post I mentioned that I’ve done two video clips with the Zi8. Here’s the first one, shot in indoors daylight, an original composition I call Kui Lima:

and here’s one demonstrating the low light performance of the Zi8, an old song called Kalena Kai:

So that’s the story as I see it. For my particular application, shooting solo performer music videos, this little cam seems like a pretty good tool for the job. And like always in the fast moving world of consumer technology, we can look forward to the response this cam generates among competitors.

I’ve tweaked and fiddled with this guitar for a while, especially since I brought it to O`ahu. The humidity is pretty tough on instruments. The tuning machines have always been stiff and they’ve gotten worse lately, so I decided to swap them out for the new Grover Vintage Sta-Tite 18:1 machines. I’ve heard great things about these machines on various guitar forums, and the measurements looked right to be a drop-in replacement for the stock tuning machines. I ordered up a set of #4592 Grover 18:1 Sta-Tites from Stewart-McDonald.

Well, for once luck was with me, and in fact they work and look like they were made for this guitar. Screw holed lined up, the shaft diameters are different but the bushings that came with the new Sta-Tites fit right into the old holes. Here’s a pic of the back of the peghead with half the machines replaced:

Epi Peghead with old and new tuners

These new machines are basically totally different from the originals. The base plate is thicker, the gears are obviously different to provide the higher gear ratio, and the attachment of the gears is totally different as well.

Here’s the original tuning machine:

Original Epi Grover Tuning Machine

Part of the difficulty in turning it is due to the warped base, the rest because the curved arm that holds the shaft has bent, releasing the mesh of the right angle gears.

Here’s the new one:

New Grover Sta-Tite 18:1

Notice how solid and thick the base plate is, and more importantly notice that the shaft is held in a cast mount, a much more solid bit of engineering.

These tuning machines have another fine virtue, they’re not terribly expensive. I bought this set from Stewart-McDonald for $37.37 – I’ve already gotten my money’s worth the first time I changed strings.

As I expected, some folks reject the validity of these controlled tests, stating that different mics respond to different positioning in different ways, and their performance in their optimal position is the important issue. I can only suggest that they try some controlled testing in those different positions. After all, if the difference really exists, it should be apparent when levels and positions are matched, right?

And as I expected, some people pointed out that mics with different patterns and mics with very different transducer technology, like ribbon mics, sound different from the cardioid condensers I used. I absolutely agree.

Also as I expected, some people suggested that my use of a single source, the acoustic guitar, is preventing me from hearing the differences, which show themselves on cymbals and vocals. As Dirty Harry was wont to say, “A man’s gotta know his limitations.” I don’t record those sources so I don’t use them for testing .

One comment that has come up a couple of times is that the mics I chose were too similar, all large diaphragm mics from the low end of the spectrum. So I pulled out my highest priced mic, a Schoeps CMC64 small diaphragm condenser, and stuck it in the array.

Variety is the Spice of Mics?

For a little more variety, I replaced the Rode and AT mics with the Shure KSM141 and KSM44. So this set of clips includes two large diaphragm mics and two SD mics, and the price spread ranges from under $200 to over $1500.

I followed the same procedure I illustrated in yesterday’s post, aligning mic diaphragms by eye, playing a test tone through a small speaker about 1 foot from the mics, then adjusting gain on the M-Audio Profire 2626 to match their levels as well as possible in Reaper. Then I recorded the test tone followed by the acoustic guitar clip.

Mics and Clips

So here are the mics:

CAD M179
Schoeps CMC64
Shure KSM44
Shure KSM141

and here are the clips:

download 20090626-F.wav
download 20090626-G.wav
download 20090626-H.wav
download 20090626-I.wav

As before, I’ll post the key to the clip identities in a future blog entry. Or if you post your opinion and preference in a comment here or on one of the forums I visit I’ll email or PM the information to you.

Philosophical Musing

Please let me take a moment to wax philosophical here. No one has reported doing double blind ABX comparisons on the clips so far. Several posters have offered opinions on the sonic qualities of the clips, but no one has confirmed that they can actually hear a difference! This seems to be human nature, but I think that skipping the double blind check is missing a really valuable learning experience.

Sometimes when I’ve listened to mic samples I thought I heard these dramatic differences, but after a bit I realized that I was listening to different performances, not different mics. Sure the mics had been changed, but the player was hitting the strings differently and playing different riffs at a different volume – so how could I tell what part of the difference was the mic, and what part the player?

Since then I’ve tried to do some mic tests of my own, and I’ve tried to educate myself on audio testing. At this point I’m beginning to think that the differences in microphones are a lot more subtle than I had been led to believe, which makes a careful test even more important. As I’ve mentioned before, very small differences in volume are registered by our ear/brain combination as differences in quality rather than loudness. I’d like to demonstrate the steps I now take to try to make my mic comparisons, and preamp and a/d comparisons, meaningful.

Mic Setup

The mics need to be close together, but not interfere with each other. I try to determine the location of the diaphragm, the part of the microphone that gets hit by the sound waves, on each mic, and align them along that position. This is pretty easy with large diaphragm mics, often a bit tricky with small diaphragm units. All the mics should be on axis to the source or all should be equally off axis. Check pattern switches, rolloff settings, pads, any feature of the mic than changes its response. I’ve missed this step a few times.

I also arrange the mics so they don’t interfere with each other. For instance, it’s not a good idea to tie a bunch of small diaphragm mics into a bundle, because the ports behind the capsule contribute toi the frequency response and pattern of the mic. If those ports are blocked the mic is not performing normally.

There are three mics being compared in this example. The CAD M179 is a low cost continuously variable mic in an unusual looking housing. One salesperson began a drumbeat for these mics and they are now widely recommended in internet recording forums. The Rode NT2a is one I’ve used before. I think it does a fine job of capturing audio with low noise and no noticeable distortion, but many forum posts are negative toward Rode in general and the NT2a in particular. The Audio-Technica AT3035 has recently been discontinued, replaced by the AT2035. In the past I’ve read a wide range of comments about this mic, with some calling it a secret gem and others decrying its overwhelmingly bright character.

Here’s a picture of a mic array arranged for testing. A cheater clamp that fastens to the mic stand main tube can help fit an extra mic into the array. Adapters to attach mics at an angle can be very handy as well.

Three large diaphragm mics in an array for comparison

I often hear this arrangement, with all the mics equidistant from the source, criticized because different mics work best in different positions. I strongly suggest that if you wish to evaluate different positions you try all the mics in all the positions. It’s a little more trouble, but it’s a great learning opportunity, and omitting this step means no valid comparison can be made. We’re right back to asking what part of the difference is the mic, what part is the location with no way to answer the question.

Of course, my aim here is different from trying mics and positions to get a good recorded sound. I’m after data, not art. When the aim is art, the ears rule!

Equipment wise, you can do a useful comparison with as few as two recording inputs. In fact, comparisons that are done two by two are probably the most revealing and useful. Still its fun to line up three or four mics for a single session – in which case it’s helpful to have four identical channels, especially if the comparison will be made public. In my experience, more posters will criticize a change in preamp than will mention a change in performance, amazingly enough.

Here’s a video that illustrates the setup process and takes you through gain calibration, discussed below:

Microphone Comparison - A Tutorial - part 1 of 2 from Fran Guidry on Vimeo.

Gain Calibration

Once we’ve arranged the mics to capture a single performance we need to minimize the volume difference in the our samples. I like to start with a test tone played into all the mics from a speaker only a foot or so away. A 1000 Hz tone is not very challenging, so even a low cost computer speaker can be used as the source. A test tone is easy to come by and it doesn’t need to be calibrated for volume since we’re interested in relative rather than absolute levels.

I’m using Reaper to conduct this test, and a little inquiry on the Reaper user forum and learned about MDA Test Tone, a plugin that provides the beep.

In Reaper I created a project with MDA Test Tone on one track, and three tracks for recording the three mics. I also adjusted the range of the Reaper console meters. With these connections in place I hit record and adjusted the preamp gain for each mic so they all were very close to -18 DbFS.

Next I discarded these recordings and captured three more tracks to store a consistent level for each mic. These 1000 Hz tones are used to fine tune the track levels later.

Recording

In the next video we actually do a little recording. After all the setup and calibration work, the recording process is anticlimactic. Move the calibration speaker, tune up the guitar, hit Record in Reaper, play a few bars, and we have our clips in the can. Be sure to record the clips on the same tracks as the reference tones we created in the last step. That way when we adjust the reference tones we adjust the clips at the same time.

For straight mic comparisons, I like to position the guitar about 32″ from the mics. This avoids proximity effect and hopefully presents a fully developed guitar sound to the mics, instead of one mic picking up the neck of the guitar while another picks up the bridge.

Here’s the video demonstration of recording simultaneous tracks and fine tuning the gain:

Microphone Comparison - A Tutorial - part 2 of 2 from Fran Guidry on Vimeo.

Volume Fine Tuning and Rendering

As the video illustrates, working with that 1000 Hz test tone can be pretty annoying, but we need to delve into it one more time. Actually, this time we can turn the volume down, because we’re adjusting levels “in the box” – that is, internally in the computer.

The helpful folks at the Reaper Forum pointed me to the Sonalksis FreeG plugin. This tool adds high resolution metering and gain adjustment we can use to tweak the levels of our clips that last little bit.

Simply place the Reaper track cursor so the recorded test tone will be played, reset the FreeG meter, and play a bit of the clip (the space bar starts and starts playback). Note the RMS level, and repeat for each track. Then, to be fair, apply a gain adjustment to each track so they all show the same RMS level. In the video I’m fiddling with the Gain knob using the mouse, but after I recorded the session I realized that you can simply type the desired gain change into the value box, making it very easy to get the level just right.

Finally, click and drag the cursor to make a time selection of the recorded clips, then render each track separately as illustrated in the video. It’s a good idea to render to 44.1/16 format if you plan to make the clips public, because everyone can play this CD standard format.

Blind Comparison

I have had the experience many times of listening to mic comparison clips and clearly hearing the difference between them when I knew their identities, then finding that I could not hear a difference at all when I hid the identification in some way. Even getting momentarily confused about the source of the clips has been enough to change what I “hear”. Our brains are at least as important as our ears in defining what we hear, and our brains like new stuff, shiny stuff, expensive stuff. So when we know a clip was made with our shiny new expensive mic, we’re going to “hear” how wonderful it sounds.

For a test to be meaningful, we need to hide the identity of the clips somehow. This is pretty hard to do when working by ourselves. The foobar2000 audio player offers one solution, with the ABX testing utility built-in, as described in this blog post. This is a powerful tool, because it not only offers a way to test clips double blind, it helps us determine if we can hear any difference at all before we try to determine a preference.

Mic comparisons are useful for our own recording knowledge, but it’s even better to share. There are lots of folks hanging out at recording forums on the internet who are looking for information about mics and other recording gear. I like to contribute when I can by posting comparison clips, but I think it’s important to make the original post without identifying the devices used. It’s more informative, and more fun too.

So here are the three clips I recorded in the video, with no EQ, no compression, no reverb, no processing of any kind except to match volume levels and trim ends. To recap, the three mics being compared are the CAD M179, Rode NT2a, and Audio-Technica AT3035. Naturally the clips are not in the order listed.

download 20090625-J.wav
download 20090625-K.wav
download 20090625-L.wav

I’ll post the key to the clip identities in a future blog entry. Or if you post your opinion and preference in a comment here or on one of the forums I visit I’ll email or PM the information to you.

Naturally a cheapskate like me is only interested in free solutions, so the software tools for this project are Avidemux for video and Wavosaur for audio. With these two tools we can tweak our camera audio by raising volume, adding reverb, adjusting tone, and so on.

Trim Video and Extract Audio

We start by opening the video in Avidemux. Next we trim the video to eliminate alternate takes and start and stop activity that we don’t need to display. The A and B markers in Avidemux make this an easy task, just be sure to only set these markers on I frames, not P frames. Then set the container format to match the original video, and save the file, preferably to a new name, retaining the original. Avidemux will only save the portion of the video within the A and B markers. As always with Avidemux we must enter the file extension, and it should match the container format.

Next, open the newly saved trimmed file. We want to save the audio as an uncompressed WAV file in most cases, so set the Audio codec to PCM. Then save the audio from this video using the Audio : Save menu option, being sure to add the .WAV extension. Close Avidemux.

Enhance Audio with Wavosaur

Now start Wavosaur and open the newly extracted audio file. In our example we’ll only adjust the volume, and we’ll do that in the simplest way, by normalizing the file to -3dB. (Maximum volume in a digital audio file is called 0dB, so all volume levels are expressed as negative numbers.) Use the Process : Normalize menu option, then select Custom and set the value to -3. The audio file is now noticeably louder. Save the file and close Wavosaur.

Merge Enhanced Audio with Avidemux

Restart Avidemux and open the trimmed clip. Set the container Format to match the file type. Now merge the enhanced audio file using the Audio : Main Track menu option. Set the source to External WAV and Open the file we just ehanced in Wavosaour. We’re almost done, but we need to recompress the audio – it’s currently an uncompressed WAV file and we need to return it to the AAC format (or other as appropriate) that we started with. So set the Audio field to the AAC codec and save the file. Now you’re ready to upload your video with its enhanced audio.

Of course it’s a lot easier to follow these steps in a video demonstration, so please check this one out.

Audio Enhancement Using Avidemux and Wavosaur from Fran Guidry on Vimeo.

VST Plugins

Wavosaur is a handy audio tool with a simple interface and good performance, but it needs a little help from some other free software tools called VST plugins. These are software tools for audio that can be added to any program that knows how to be a VST host, and Wavosaour is just such a program.

Some of my favorite VST plugins are created by Kjaerhus Audio. The Classic series of effects are all free downloads, and no one should be without Classic EQ and Classic Reverb.

While I was perusing the Wavosaur tutorials I discovered another EQ tool, called PushTec 5.1 and I was startled by the excellent selection of presets. Be sure to spend a few moments going through the tutorials to better understand the power of Wavosaur and of this terrific free utility.