Feeling the Whomp - III

My short life as a practical scientist seems to have come to an end. In the Pursuit of the Wily Whomp I posited that by finding the correct location for the stereo microphones the whomp would be phased out, or at least noticeably dropped in volume. But I could not find any location on the face or sides or neck of the LKSM-12 where opposite phase vibrations were picked up by the music microphones. However I did learn something new that might help microphone placement for individual guitars.

The closest I came to finding out of phase information was finding areas where the frequency was strongly doubled. Doctor Russell used an "accelerometer" to measure surface vibrations, perhaps some type of surface contact device like a piezo pickup. I'm using a microphone, and I think the volume of sound coming out of the sound hole swamps any sound from surface vibrations at the sound hole's resonant frequency (91 hertz).

In Pursuit of the Wily Whomp - part deux

The whomp is still here! I could have sworn that I found the cure over the weekend, but listening to the same recordings later in the evening reveals the whomp in all its booming glory. Are my audial perceptions changing over the course of the day? I recorded some more last night using one microphone scanning over 8 or 9 different positions, repeating the passage in BWV999 that passes from D root through A on its journey to the E pedal. The boom is particularly noticeable as the root approaches A. The boom seems prominent on any part of the top, and much less noticeable on the sides. I start to think along the lines of phase cancellation; if the boom is in a positive phase in one part of the guitar, perhaps placing the second mic in a positions where the boom is in a negative phase would effectively cancel it.

I found a paper online by Dr. Daniel Russell at Kettering University on Acoustic Guitar (in this case, a Gibson) vibration modes, available online here; I think the information on the 2nd and 3rd modes might be relevant. If true, a mic over the saddle and one somewhere in the upper bout should have whomp cancellation. I'm not sure from the animations if the upper bout mic should be over the fret board or alongside it, but a recording test with both options should verify this. If true, I expect the spectrum graphs to show the whomp on both mics, but when combined it should not be as evident.

More to come.

Losing the Whomp

I'm not liking the Jecklin array much lately. The LKSM-12 is tuned to down a minor third and this puts the 5th course at about 91 hertz; this happens to be the same as the sound hole is tuned and for close mic'ing, which I do with omni mics in the Jecklin array, the 'whomp' of the A course bothers me. The spectrum shot above shows 2 of the whomps (circled). Look how much louder they are!

The B45-12 - The First Meeting

I bought my first 12-string, a Gibson B45-12, in a pawnshop on 3rd Street in New York City. Why did I buy a 12-string? I don't recall even hearing a 12-string except for maybe a Hudie Ledbetter song. I don’t think I knew anything about 12-strings, but that it was a big, shiny object, and made my teenage eyes grow huge with desire. The amount of hardware and shiny strings fascinated me.

I had seen some odd, fascinating musical instruments in the Village - things that looked like guitars but with weirdly extra strings. Here I was not far from the Village, over on Third Street, looking to buy a guitar and I found myself compelled to buy this 12-string in this pawnshop. It stayed with me for the next 40 years, and is with me today, through many interesting times, pictured on the right.

Within about 10 years the top became wavy, and the bridge started lifting. Part of this was the light construction of this guitar, but most of it was my fault: Living from apartment to apartment, sometimes rooming with others, hitchhiking from Boston to Cape Cod to New York City in super hot days and icy-cold ones, the guitar stayed with me, strings rarely changed, often not in tune. There were also the peaks and valleys of drug use, drugs to make you play like mad, drugs to make you want to 'adjust' everything,

I never use open tunings. Here is why.

Leo Kottke, the father of the modern 12-string sound, often used open tunings early in his career, particularly on slide guitar. I expect that slide (aka bottleneck) guitar almost requires an open tuning. Tappers also probably benefit from open tuning.

6-string steel guitarists use open tunings all the time. I think one of the most popular open tunings is DADGAD; I see references about it a lot in the music newsgroups and forums.

Guitar pieces using open tunings are pretty easy to identify - they seem to have a new-age sameness to them, never change keys, and don't stray too far from the root. This is not universally true, of course. For example, Pierre Bensusan is an astounding guitarist who just happens to compose and play in DADGAD.

Searching for the perfect 12-string microphone

I've had a few false starts and spent more money that I should have, but as of now I've settled on a matched pair of OKTAVA MC-012 with omni capsules and use them in a modified Jecklin array. I mic as close as I can get the guitar to the array baffle, so close that I sometimes hit it with the guitar!I needed microphones that will capture the sound of a 12-string. One way to audition a lot of microphones is by going to the Listening Sessions web site. They don't have any guitar with a variety of small diaphragm capsule (SDC) microphones, but there is an interesting collection of large diaphragm (LDC) microphones with guitar samples in session 5. At the bottom of the page are links to listening sessions on other sites. I like to listen to these using a double-blind method. I download all the samples, then play them in some repeatable but unknown order (I'm a programmer, so a quick perl script is all it takes),

Home Recording - the room

The room where you record has a tremendous potential on your sound. It's easy to prove this. Download the NTI Minirator program and play some tones in your recording room. Try frequencies from 60 or 70 hertz up to about 200 hertz. As you play one, walk around and listen to the volume change drastically, often within a foot or so. These are caused by standing waves and reflections. You have to minimize these reflections; you have to minimize standing waves, or find a location between them. It's possible to find a place to put the microphones that will not be affected by the standing waves, but there are probably other reflections too numerous to avoid. You can calculate roughly which frequencies will cause standing wave problems based on your recording studion dimensions. Here's one way.

Home Recording a 12-string

Recording a guitar is said to very difficult, yet you can often hear great sounding recordings of steel 6-strings and classical guitars recorded in modest studios using home equipment. There are fewer 12-string guitarists, but one can sometimes hear a good acoustic sound from a home-recordist. For 3 or 4 years I've felt very frustrated trying to get a good sound from the 12-string in my home studio, but for a little over a year now I feel that my recordings are starting to capture the sound correctly. I don't know enough to generalize to anyone else's situation, but perhaps this run-down of my setup and the reasons behind it might help another 12-stringer to come up with a great sound.

More on Low Tuning

I had written about putting heavy Elixir strings on the Gibson B45-12 and tuning it down a fourth. But after listening to some recordings on different speakers, I felt the high courses sounded too slack, so I retuned down only a third. This fixed the high strings a bit, but the low strings lost a lot of thunder. Next I tried tuning down a fourth, but using a higher reference to A (easy to do with the Korg chromatic tuner). In this case also I didn't find much to gain, so I'm back to a fourth down; the courses are now B, E, A, D, F#, B.

I'm also somewhat obsessively lowering the action at the nut end, a couple of times by too much, repaired by filling in the slot with powdered bone and crazy glue, then re-filing with the nut files. The neck relief is almost non-existent now on the Gibson, and the strings are about as low as I can get them. The guitar plays better than it ever has, but it is still not as easy as either of my Taylor 12-strings. I'm thinking of posting samples of the same piece played with each guitar. The difference in sound between 12-strings with different tunings is amazing.

Muscle memory

One of the good folks that populate rec.music.classical.guitar (RMCG) suggested that I depend on muscle memory to increase the speed of the Bach piece that I've been working on recently. I pointed out that I've been playing it for 20 years, so my muscles have, I hope, memorized it. But it raises an interesting subject.

It seems that the most awkward hand movements when playing can become quite easy and natural with practice. I think this is what is commonly referred to as "muscle memory". For me, the process seems to take a few hours of playing, but not all at once. Breaks from playing the same thing over and over seem to accelerate the learning process. Something happens during a break of, for instance, 10 minutes, so that coming back to a piece is like returning with new hands and brain.

The new left hand positions for BWV999 that I described in a previous post were imprinted fairly quickly, over-writing what I had been doing for 20 years. It helped when I could see the logic of the positions, how anchor fingers glided down the frets. This seemed to convince some part of me that, yes, this was worth doing. Now, after a few days, my right hand doesn't seem to believe that my left hand is already in position and messes up. Bad hand! More practice for you.

I don't think I've pushed myself nearly to the limit of "muscle memory".

BWV999 - Getting up to speed

The new fingering (pima mpmi ....) is helping to increase the speed, but when running at greater than quarter=90 I'm running into left hand problems. Fingerings that worked ok at a slower speed now get tangled up in the transitions, and it's important to the music flow to get it smooth - the bass in the last quarter note of each measure leads to the tonic of the next measure.

In particular, measures 22 through 27 were difficult, so I came up with new fingering that always has at least one anchor finger as it descends down from the tenth fret to the fourth fret. Click on the image to see it full size:

BWV999 - Bach Lute Prelude

BWV999 is the catalog index for a short and simple Lute prelude composed by Johann Sebastian Bach. The original was in Cm and the only way we know about it is from a contemporaneous copy done by Kellner which you can see here.

It makes a nice piece for the 12-string, if you enjoy fingerpicking. You can use the usual guitar transcription, which changes the key to Dm. Here's a version.

Gibson B45-12 down low

I'm trying heavy Elixir strings on the Gibson B45-12. Because the guitar is fragile and old, I'm tuning down a fourth, so the 1st and 6th courses are B instead of E. First results are better than I expected. The guitar is not a bright guitar, particularly when compared to a Taylor. The floating bridge is ebony and has notches, and I think this muffles the sound. The side and back are mahogany, considered a dark sounding wood. There is not much jangle; the top 2 courses sound positively muted. I've been using Martin Marquis, a medium weight string and tune it down a minor third. But since I have an LKSM-12 tuned the same my thoughts for the Gibson were to put bright light strings tuned up to concert to counter the mellow darkness of the guitar itself. However I changed my mind for some reason and put the heavies on it. The big dreadnaught shape seems to handle the lows very smoothly, and now all the strings seem to be tuned under that muffled sounding ceiling (which is the best way I can think to describe the effect), giving it a rather grand, maybe somewhat ponderous, sound.
Here's a sample, 1.3 megs

Buying Strings

I just sent in an order for 9 sets of strings, 3 heavy, 3 medium, and 3 extra light. They are Elixirs, and even after looking all over the 'Net, the best price, including shipping, runs well over a hundred bucks. This hurts.

How long do strings last? They need to last a good long time when you have several twelve-strings. Changing them takes about an hour if all goes well. Sometimes when you think they need changing - the guitar sounds dull - a day later everything seems fine. What is that? Humidity, bad mood?

It used to be that new strings always made the guitar sound new. Lately this hasn't been the case, and I sometimes wonder if I should have even bothered changing them. I don't know if this is characteristic of Elixirs, which I only started using in the last couple of years, or if it is my aging ears that no longer hear the new highs. New strings used to be cause for endless hours of musical haze, playing brightness, new sounds, new sensations. Now I seldom hear much of a difference. When I was younger I may have gone many months between changing strings. Maybe that's it. I should leave these suckers on longer. Yet I have a new bunch of strings inward bound, and the thoughts of the sounds of new strings calls to me like a drug.

Time to change strings!

why a 12-string

A Acoustic Guitar Forum friend asked, "why a 12-string and not a 6-string?". I think the following is correct, although to tell the truth, I don't know if I can put into words why I play a 12-string.
"As for 12 vs. 6 sound differences, a 12 has two distinct sounds when finger picking.
The octave courses (strings 3, 4, 5, 6) are struck with the thumb and strings 1, 2, and 3 are usually picked
with i, m, or a. The 3rd string can be hit with thumb or fingers, and will sound very different depending which is used. When the 3rd string is struck with the thumb it tends to have both the high and low course resonate, and when fingers are used only the lower string sounds strongly. Pieces like Bach's Cm prelude for Lute tend to sound good because the 2 voices sound like different instruments.

Good 12 String Albums on iTunes

Here are some good examples of 12-string music.


Leo Kottke - One Guitar, No VocalsAll instrumentals.


Leo Kottke - 6- and 12-String GuitarAll instrumentals.