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Shells and Coverings

Going back thousands of years, the traditional drum shell material has been wood. It’s musical, depending on the type, it’s easy to work with and it’s relatively inexpensive. Metals have also been used and since the 1970’s, plastic. Let’s look at plastics first.

Acrylic

Though an experimental Plexiglass set was made by Bill Zickos in 1959, they were commercially introduced a decade later. In 1969, Zickos sold its first professional kit to Ron Bushy of Iron Butterfly of “In-A-Gadda-Da-Vida” fame. Fibes and Ludwig soon jumped in the game in the early 1970s. These acrylic shells weren’t marketed as a sonic improvement over wood, they just looked cooler. They do have a particular sound, which some have come to appreciate. Acrylic shells are made of hard, dense plastic, and when paired with plastic heads, well, you can imagine the sound. Remember, the more rigid and dense a shell is, the less it will vibrate; thus, it’s more likely that the sound from the drum head will be the predominate sound of the drum.

Fiberglass and Resins

Larrie London, top session drummer in the 1980s, preferred the sound of thin, fiberglass shells and when on stage he used a wrap-over-fiberglass kit. But for the studio, Pearl made unwrapped fiberglass kits for him. Without the wrap, the drums had a bit more tone and the sound appealed to his ears, especially when close mic’ed in the studio. Bright and loud, these were very thin shells (single head toms), considerably thinner than wood. Proximity effect from close mic’ing and the brighter shells gave Larrie the recorded tone he preferred.

Metals

Metals are used primarily on snare drums and offer unlimited tonal choices for what most people regard as the signature sound for any drummer. Choices are varied, such as copper, brass, aluminum, steel, hammered, etc.. Each metal has its own tonal characteristic. Entire metal kits are not that popular. Carl Palmer famously had a stainless steel kit made in the seventies. It was very heavy and I’m sure roadies hated it. But metals are great for signature snare sounds. I find for studio work it makes sense to have many snares on hand to find the right one for each tune or project.

Wood

Wood is the traditional choice for most drummers. Modern manufacturing allows perfectly formed shells out of a wide variety of woods, all chosen for their musical ‘notes’ (see the Janka Hardness Test in part 2 of this series). Modern production also allows for thinner and thinner shells; lighter and stronger, not needing the reinforcement rings of yesteryear. Modern shells are manufactured out of thin, wood veneers, as few as 3-plys, glued and pressed to form a molded plywood shell. Shells made of solid wood, thin and steam-bent, are popular with some. Slingerland ‘Radio Kings’ come to mind. The wood grain in steam bent drums runs horizontal. Some are making ‘stave’ drums; thick wood wedges glued in a circle and machined, kind of like how old barrels were made. Modern manufacturing allows thinner shells than stave drums used to have, the wood grain is vertical, which allows a stronger bearing edge and better transfer from the head to the shell. The resulting drum is heavier than a plywood drum.

Coverings

From the early days of modern drum manufacturing, shell coverings (wraps) such as sparkles, glitters or pearls, have allowed the drummer to show off his style and personality while protecting the drum during transport.

Does the wrap affect the sound?  Yes.

The wrap is layer of dissimilar material toning down the vibration of the shell. A modern approach, instead of a wrap, is a painted surface. But let’s face it, if you’re a hard-gigging drummer a beautiful wrap keeps your drums and you looking sharp. And, for the most part, the recorded drum sounds we know and love are sounds from wrapped drums. I would say if your primary use for a kit is the studio, then don’t compromise the sound in any way; chose an unwrapped kit. But if you are a gigging drummer with occasional studio work you need a kit that will hold up to traveling. Chose a wrapped kit.

Next, where the rubber hits the road: bearing edges.

Bearing Edges, Reinforcement Rings and Other Things

Transferring the energy of a strike on the drumhead to the shell is the job of the bearing edge. I found a Federally funded research paper on this comparing different bearing edges (really!). Scientists compared 45 degree on the edge, 45 degree centered and 45 degree on edge with slight round over. Though the study was implemented by scientists (flawless people), there were flaws in the report (in my opinion), but I found the essence of the study to be factual, and a good explanation of  the function of bearing edges. The report concluded the 45 degree in the center of the shell transferred the most energy, though they didn’t know why. I believe when the 45 is in the center of the shell, the energy transfers from the center towards the edges quickly and evenly.

Older drums had reinforcement rings to stabilize the shell. This was necessary to keep drums in round.  Bearing edges were cut into the rings and tended to be rounded with more surface area in contact with the head than most modern drums. The result is a warm, rounder tone as more energy is transferred to the shell.

Now this is the biggest pet-peeve I have with drum companies and bearing edges. Most heads seat on the bearing edge on the collar of the head. The collar is the rounded bend in the head. This bugs me like nothing else. It’s as if there’s a communication breakdown between drum makers and head manufacturers. Is there a solution?

There are three I can think of.  First—and this is the best one—drum companies should undersize their shells. None, that I know of, undersize. This would open the doors to the best tonal possibilities no matter the head choice. Second, if a drum company can’t (won’t) undersize the shell, then cut the bearing edge from the outside of the shell inward. Third, drumhead companies change the dimensions on their heads. I thought this would never happen but recently Evans stepped up to the plate and introduced Level 360 which begins to address the collar problem.

There has been a lot of improvement on how heads connect to the bearing edge. Lug casings are lighter, stronger, and less resonant. Rims, especially cast rims, are an attempt to keep the head, collar, and bearing edge in rigid agreement. In an attempt to keep the shell at maximum resonance, contact with tone-dampening lug casings has been minimized. Rim mounted toms are another attempt to keep the shell free floating. Rim mounts do allow the drum to move (up and down) when hit. A mic on a studio stand doesn’t move. Though the tom may move only a half inch or so, when closed mic’ed a couple of inches away from the drum, it’s a substantial  amount.  A mic fixed to the rim of the drum moves with the drum, but vibrations from the shell are unnecessarily transferred to the mic capsule. While this configuration is ok for a live situation, it’s not good for the studio. In a studio situation, the type of rim mount is an important detail.

Lug casings and the art of drums

How can you tell who’s a serious drummer? By their admiration of the drum-set as art. And nothing is more artistic and different about drum companies than the design of the lug casing. I love the classic art deco designs of Ludwig and Slingerland and think the Ludwig casing is probably the most artistic of the bunch. I’m not a real big fan of the Camco (DW) turret but it definitely beats the latest Premier, Pork Pie (oink!), Pearl, Tama, bla, bla…

But wait, we’re talking about sound, not looks!

In order to allow the shell to vibrate freely, the lug casings need to have as little contact with the shell as possible and they need to be the lightest mass possible. True, but those vibration dampening lug casings have been a part of the drum since right after rope tensioning and are an integral part of the drum sounds on countless classic recordings. In the big picture, you judge if it is important to you and your sound to have low-mass casings.

Some final thoughts. . .

I saw a major rock act on TV the other day and when they showed a close-up of the drummer, I could see the snare wires duct-taped to the bottom head. Also, there were several large tape patches on all the top tom heads. What did that set sound like? If you’ve read this series of blogs you can deduce what it sounded like. Was it wrong? Well, not if it serves the music in a musical way.  Everything has to serve the music. Would drummers consider this guy’s approach a great drum sound? No, of course not. Though in a famous band, this guy isn’t considered a great drummer. Is there a correlation?

Modern drum companies are making great strides to build better sounding drums. Drummers are demanding more attack, tone and sustain. Meanwhile, modern music arrangements are getting more dense and crowded. The average loudness in modern recordings is getting higher and higher with the heavy-handed use of compressors, lots of compressors. Drum transients are the major victim. This may be the real casualty of the loudness wars.

This article is titled “More On Drums” and if you say it out loud – – say it now – – it sounds like “Moron Drums”, which could be said for the drummer but definitely not the drum. Drums are very complex instruments and this was underscored for me recently when I revisited a book titled “The Acoustical Foundations of Music” by John Backus. Some of the information I’m about to write about deserves repeated credit to John and his book and it took several readings by this moron drummer to understand it.

Drumheads

Most of the sound we hear when a drum is hit comes from the drumhead. The shell and other factors play into its tonal qualities. Don’t believe it? A Roto Tom (a metal frame drum without a shell) makes a drum-like sound when hit, and in this case, it’s the entire sound. When a drumhead is coupled to the shell via the bearing edge, energy is transferred to the shell and the characteristics of the shell tonally combine with the drumhead(s). It’s at this point that the type of wood used, number of plies, how the bearing edges are cut and other factors combine to make the ‘sound’ of different drums and even the sound of an entire drum company. But it all starts with the drumhead.

In his book, John analyzed the physics of striking a circular membrane and what happens with the sound, especially the overtones. John analyzed tympani because drums with two heads are infinitely more complex to measure. We are assuming the head is evenly tensioned and tuned. Circular membranes vibrate with several modes when struck. A mode is a line where tonal amplitude is at its peak. There are many modes when a drumhead is hit but John writes that beyond six basic modes, others don’t supply enough musical content to be concerned with. An initial hit produces a fundamental tone from the entire head surface, which we’ll call the first mode.  In the second most-useful mode (designated by the black hash line in the photo) the head divides in half and the two sides vibrate opposite of one another, out of phase; that is, one half the head moves up while the other side moves down.  (No console phase button for that.)

In the next mode (blue hash lines) the head divides into ‘quarters’ and these sections also vibrate opposite one another. Next (red hash line) there’s a modal line in the shape of a circle about half the size of the head; next the head divides into six pieces (purple hash lines) and finally another circle mode with a mode that again divides the head in half (green hash lines).  As you would expect, these modes are not the fundamental tone but actually overtones (light bulb moment) that are not harmonic. I’ll say that again – they – are – not – harmonic. The lowest tone that lasts the longest is the second mode, (black hash line) the one where each half is vibrating out of phase. The following mode’s frequency is 1.42 of  the second mode pitch, the next is 1.53 of the second mode pitch and so on, thus explaining the basic difficulty in tuning drums to begin with and the futility of tuning a drum to a ‘note’. Remember, this is a tympani, a drum that that should be tuned to a note. John again states that two headed drums are way more complex because of the vibrating second head, space between heads, air volume inside the drum, tuning, etc.

The initial strike moves the most air on the fundamental (mode one) but dies out quickly. You can demonstrate this yourself by lightly hitting a drum dead center and you’ll notice a ‘drier’ quick fading tone but if you strike off center the drum will have more sustain. The fundamental mode provides the ‘thump’ but the other modes supply the sustain and quality of the tone. This has to be repeated; the other modes supply the sustain and quality of the tone. Dampen these modes too much and you’ll will get a boxy sound (hello Eagles). Tune the drum evenly, let the head freely ring and you will have more sustain and better tone.

Here’s a way to check out the second modal line (the one with the most tone, which is a straight line across the drumhead). Back in the day, I would find the place to put the tape using this method (I know, yes I too liked dead snares then).  I still use this technique today to find the spot to put a touch of moon gel to cut a little overtone. Take your snare (with the snares off) and tap the drum lightly in the center while moving your finger around the drumhead about an inch from the rim. If you very lightly touch the drumhead as you move it around, you will hear a point where the ringing is less. That is the second modal line that runs across the drumhead and where you place the dampening material.

Here’s a video link where you can see 4 of the 6 useful modes: http://www.youtube.com/watch?v=v4ELxKKT5Rw&feature=related

Modern drumheads are made of plastic and are manufactured to exacting standards, so your results from head to head can be quite consistent. If you prefer a particular head, every time you replace the head you can expect a similar result, something impossible in the days of calf skin heads. When I started playing, white single-ply coated heads were just about all we could buy. We wanted clear heads so we would scrape the white coating off with a razor blade. Ugly for sure but we could see our shoes through the drum as we marched! As rock music came in full force, drumhead companies started introducing all manner of heads with multiple plies, dots, rings and colors. Musically driven? I don’t know. But I guess they introduced reinforced dots because drummers were playing harder and couldn’t afford to replace heads often, dual plies to darken the tone and eliminate the ring, colors for visual flair and so on.  And today, wow, there are several companies with all kinds of formulations and combinations.  Here is why all this is so important. If you understand fundamentally what happens to a head when it’s hit, you should be able to match your style of playing with the type of music you are playing with your particular drum set and choose a head that will give you the sound result you are expecting. Once you get good at this, you can even look at a kit and heads and know the sound it will make even before someone plays it.

So what is the best drumhead?  That depends on the music, but the drumhead that will allow the drum to “speak the most” is a single-ply clear head. All other heads dampen modes one way or another. Understanding how they dampen will allow you to alter the tonal qualities of your drums if that is what you’re looking for. Some heads are made for durability in live situations or if you play hard and can’t afford to change heads often. Some heads reinforce the initial ‘thump’ while making the head more durable. Some are designed to dampen the ‘ring’ a little. Some are just marketing gimmicks to lure the uninformed, which may possibly be the largest group of head types.

What I’ve noticed in the studio is when drums are tuned for maximum tone and sustain, they sit better in the final mix and feel more musical to me. Keeping the drums in this heightened state while playing hard will mean head changes as the sessions progress. It’s amazing how quick a head will ‘go dead’ in the studio with a hard-hitting drummer. Plastics also break down and harden over time. Do old heads, whether top or bottom, dampen modes, thus affecting tone?  Yes. This also explains why new drum heads, top and bottom, give you more sustain and tone. Even though you don’t hit the bottom head, over time, after countless vibrations, the plastic hardens and self-dampens. Take your favorite credit card and bend it and see what happens.

Once you understand drum heads and basic modes, you begin to think through your drum sound and will possibly think outside the box a little. For example, does it make sense to have a bass drum beater strike dead center on the head where the fundamental dies quickly and overtones are minimal?  No, unless all you want is smack and in some music it’s all about the kick smack. If you want a little more tone from the kick adjust the beater so it doesn’t hit dead center.

This is a lot of info to think about without discussing shell woods, plies, bearing edges, coverings, hardware, rims and sticks. And, actually, I have covered very little about heads, but hopefully enough to understand why drums sound the way they do.

In Part 2, I’ll write about the drum itself.