Toms of consistent depth

BassDriver

Silver Member
I had an interesting discussion with a drum teacher about the sonic properties associated with drum shell dimensions.

...and I was explained that you could keep all of the toms on your kit with the same depth and the only variable being diameter. This would mean that the drums could differ in fundamental pitch while retaining the same timbre - or sound "character" (determined by harmonic ratios).

...I was given the analogy of the construction of marimba bars, the width and depth of marimba bars (although the arch in the middle tends to differ quite a bit for it is sanded away for tuning) stays the same while the length differs proportionately with pitch, they keys keep consistent harmonic ratios and thus same timbre.

...has anyone heard what this sounds like, toms of consistent depth...any examples?
 

AJNystrom

Member
I know Keith Moon's "Pictures of Lily" kit featured 3 14x8 mounted toms.

Ronald Bruner, Jr. uses 8", 10", 12', 13" toms all at 7" depth. You can check out his videos and see what you think (plus he's a damn good drummer, as well). I think his drums sound stellar and it's due to the shell depths.

Personally, I prefer 1" increments with my depths for my rack toms- 6x6", 7x8", 8x10, 9x12, 10x14. I like a more significant drop- although uniform- in my sonic range. Then you couple the higher mounted toms with the deep floors (16x16, 16x18, 16x20) and there's a large change from the very high 6x6 to the extremely deep 16x20. I've had the opportunity to play this kind of set up... I just need about 3 other jobs to be able to afford it for myself.

~A.J.
 

Andy

Administrator
Staff member
Good subject, & one that's very relevant to me right now. I played a custom Slingerland 6 piece kit in the early 80's that worked on this principal. (dxh) 8x8, 10x8, 12x8 with a 16x16 floor tom. The drums matched so well, with a lovely consistent tone across the top 3. Probably the most impressive toms I've played, including my present Spaun maple toms. I'm in the process of partnering with a drum maker to produce a quite radical drum kit. Amongst many unusual features, we'll be following the same equal depth principal. Sizes will be 8x10, 10x10, 12x10, & 14x14. There's a reason for the extra depth that I'll go into once the kit is made (& when I've had a chance to test my theory, lol).
 

caddywumpus

Platinum Member
...I was given the analogy of the construction of marimba bars, the width and depth of marimba bars (although the arch in the middle tends to differ quite a bit for it is sanded away for tuning) stays the same while the length differs proportionately with pitch, they keys keep consistent harmonic ratios and thus same timbre.
Um...on GOOD mallet instruments, the bars are graduated (get wider) as they get lower in pitch. Companies like Marimba One or Yamaha or Adams have low C bars on their 5 octave models that are less than 3 inches wide(!!!). This might make them easier to play on, but the sound suffers tremendously. You end up hearing the E overtone 3.5 octaves up more than you hear the fundamental pitch. Look into Leigh Howard Steven's studies of marimba acoustics for more info, or better yet, play 2 low Cs next to each other, one of them 2.5"-3" wide, and the other one more than 4" wide...you'll hear a definite difference!

When I had my marimba made, I had it modeled after Malletech's design, and had the opportunity to compare it with a few other 5-octave models while I was in college. No comparison--my lower octave sounded SOOOO much better than the others. You could actually hear the proper notes when playing down there, and they were full and warm sounding, and blended into the middle range of the marimba. The other marimbas had a thinner sound down there and you couldn't clearly distinguish the fundamental over the sound of the first two overtones (they sounded good down to the low A, but then got "thinner" sounding below that).

I don't know what this has to do with shell depth, but the marimba bar analogy that you were told is severely lacking. Besides, do you actually want the same timbre from drum to drum? I want my floor toms to sound like floor toms and my rack toms to sound like rack toms. I want my crashes to sound different, too. I want my small crash to be brighter and "quicker" and my larger crash to be darker and sustain more. If I had 3 crashes, and they all sounded like they were from the same series, that would be too boring and I feel that it might be limiting to the range of my vocabulary and expressiveness.

...but, that's just my opinion.
 

Bo Eder

Platinum Member
Steve Smith is also playing same-depth toms on his signature Sonor kit: 8x8, 8x10,8x12. But to be honest, I can't tell if the timbre matches, I just hear different pitches.
 

BassDriver

Silver Member
What if you carried on the consistent shell depth to the low toms?

You could have 14 x 8 and 16 x 8, would there be a point where the timbre trails off?

I don't know what this has to do with shell depth, but the marimba bar analogy that you were told is severely lacking. Besides, do you actually want the same timbre from drum to drum? I want my floor toms to sound like floor toms and my rack toms to sound like rack toms. I want my crashes to sound different, too. I want my small crash to be brighter and "quicker" and my larger crash to be darker and sustain more. If I had 3 crashes, and they all sounded like they were from the same series, that would be too boring and I feel that it might be limiting to the range of my vocabulary and expressiveness.
What about roto-toms? They have the same amount of shell depth (none), and have consistent timbres while having different pitches determined by diameter.
 

Andy

Administrator
Staff member
Does anyone here actually know the science to a drum's sound based on dimensions?
Apart from the basics, not really. The obvious stuff:
Assuming the same tension & head material, larger diameter = lower pitch due to slower oscillation. (+ reverse applies)
More head mass = greater sustain due to inertia. (+ reverse applies)
More head mass = lower pitch due to slower oscillation. (+ reverse applies)
More head mass = slower amplitude curve. (+ reverse applies)
Thin shell = greater resonance. (+ reverse applies)
Re rings = raised pitch.
Greater shell depth = dominant overtones.
Less shell depth = dominant fundamental tone.

Of course, there's a ton of other variables such as tuning, bearing edge accuracy & design, wood density, &, according to my recent experiences, age of timber.

I can only assume that deeper shells somehow allow more overtones to develop due to the increased internal volume & distance. I'm guessing the sound waves essentially bounce around more, thus weakening the fundamental tone in the mix. Take concert toms as an example. Very clear & uncluttered voice. There's only one main oscillating surface. The sound escapes quickly and in an unmolested way. I also suspect the level of shell involvement is reduced for the same reasons, & that deep drums bring about the reverse affect.
 

bobdadruma

Platinum Member
I have two kits that have 10 and 12 inch mounted toms that are the same depth. 7 inches on one kit and 8 inches on the other.
I have experimented with them a lot.
The toms have no problem sounding different from each other even when tuned to the same tension.
I can't really tell much difference in the separation of sound between the same depth tom kits and my kit that has toms that have a one inch difference.
Slight difference, but I have to really listen to notice it.
Of course if there was a big difference in depth like 4 inches for example the difference would be great.
1 inch doesn't seem to matter that much.

I find that tuning my same depth toms is easier than tuning my different depth toms.

My Pearl Rhythm Traveler kit has 10, 12, and 14 inch diameter toms that are all 5 inches deep.
They have no reso heads. They have a big separation in sound also.
 
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GruntersDad

Administrator - Mayor
Staff member
2. Shell depth equates to articulation, resonance and the volume (power) of the resonant note given off by the drum shell. The shell depth coupled with wood and construction gives the drum its character.

By way of example, a 12” x 10” (as in Dia. x Depth) gives you a shell surface area of 370 sq. in. as opposed to 333 sq. in. for a 12” x 9”. So the 10” depth is a 11% increase in the shell surface area and generally translates into an increase in resonance and or power. If the shell is reasonably thin, the tone of the 10” depth will be ever so slightly deeper and the note duration a few milliseconds longer. Engineers refer to it as “fatter”. The added depth also adds volume to the drum note. And if the shell is thick, adding depth translates into focusing more volume to those at 90° to the drumhead surface (audience). Regardless of diameter, a one-inch change in shell length, for a drum of identical diameter, generally translates into the same increase of 11% or decrease of 10%. So a 12” x 8” will be 20% less in surface area than a 12” x 10”. Simply put, the depth of the “punch” will be more evident on the 12” x 10” than that of a 12” x 8” drum.
As an added note, often drummers always talk of wanting more resonance, but then turn around and put aftermarket devices on the head surface to mute out unwanted overtones. Overtones are of course a form of resonance. If you want your toms more articulated, I would suggest you are far better off to buy shallow depth drums than you are to buy so-called “power toms”. You may think you are getting a drum that can tune deeper, but the trade off is less control over resonance than you will get on a shallow depth drum. Think of how tight and articulate a 3” deep snare is as opposed to one which is 6-7” deep. It works much the same way with toms, and bass drums.
So with these concepts in mind, I find a 12” drum is better paired with a 10” or 14” drum than it is a 11” or 13”. That is unless you have a 10” or 14” and really desire something in-between for pitch. Then the in between sizes make sense.

The common belief is that even sized drums produce better tuning qualities. I don’t know why this belief is out there, I find they can all be tuned if tuned as the shell/diameter allows. If you try to make a 13” sound like a 14” while pairing it with a 12”, you’re setting yourself up for trouble unless you want a small incremental note difference.

From the Drum tuning Bible
 
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