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What does drum depth ACTUALLY do!?

xsabers

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On was watching an old Dream Theater concert when they played the entire Dark Side of the Moon album. Portnoy was on the smaller of his stage kits and his floor tom was very shallow, maybe 10", and it sounded great with just enough resonance.
 

xsabers

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I was watching an old Dream Theater concert when they played the entire Dark Side of the Moon album. Portnoy was on the smaller of his stage kits and his floor tom was very shallow, maybe 10", and it sounded great with just enough resonance.
 

Ron_M

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Sustain is the length of the complex waveform generated when a drum is struck, until the amplitude decays to negligible level. Resonance is typically a single frequency that dominates a system due to an oscillation or additive reflection within that system. The depth of a Tom and the fundamental note that it is tuned to have to have a specific relationship in order for resonance to occur. I get a bit lost, though, when it comes to sustain. My guess is that if a drum is improperly tuned, either from a head note to depth perspective, or t-rod to t-rod disparity, the fundamental is weak, and the perception is that the drum sounds choked, even though the overtones may sustain/ring.
 

Elvis

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Ron,

It almost sounds to me like you've defined Perceived Resonance.
Otherwise, how do you tell which single frequency, out of all the frequency's that occur when a drum is struck, is the dominate one?
Regardless, Resonance is a condition based on how something is constructed, not a note value.



Elvis
 

Seb77

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With cylindrical drums (not timpani), the fundamental is what you hear when you mute the perimeter of the batter head and hit close to center - the lowest frequency in the mix.

As for sustain of overtones vs. that of the fundamental, there's a similar phenomenon with bass guitars, so-called dead spots. The overtones ring out , but the fundamental only sounds for a very short time. Some people don't hear dead-spots for that reason, but when you play to the fundamental/mute the overtones, it becomes clear - the "bottom drops out" on these frets.

Fundamental has to do with head tension, but also with the resonance of the shell cavity; in fact, on two drums tuned the same, the frequency of the fundamental is slightly lower with a deeper shell, even though this is negligible because you normally compensate by tuning the reso head higher.

I think we can by now agree that the deeper drum is capable of producing more volume in the fundamental, but you need to hit harder as well. I'm not so sure anymore about the sustain duration of the fundamental being shorter or longer with different shell depths, too many varibales like floor tom legs, proximity to the floor head choice etc. At low volume a shallower drum does have a longer sustain, but it might be that at low volume the deeper drum doesn't "speak" , that there's a certain threshold, hence sounds shorter than a short version of the same shell. When struck hard, the deeper drum might as well have a longer sustain.
 

Ron_M

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Elvis said:
Ron,

It almost sounds to me like you've defined Perceived Resonance.
Otherwise, how do you tell which single frequency, out of all the frequency's that occur when a drum is struck, is the dominate one?
Regardless, Resonance is a condition based on how something is constructed, not a note value.



Elvis
It's both, Elvis. The fundamental note vs the length of the shell will determine whether a resonance will occur. The note determines the wavelength and if the length of the shell terminates at the wavelengths nodes, then resonance will occur. This condition reinforces the fundamental. As far as determining the fundamental, that's easy; if you run a spectral scan on the drum strike, the fundamental will be frequency highest in amplitude. Harmonics are always of a lesser amplitude, although, I suppose a condition could exist where a harmonic could be reinforced by a resonance. Anyone on this last bit?
 

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Ron_M said:
the fundamental will be frequency highest in amplitude. Harmonics are always of a lesser amplitude, although, I suppose a condition could exist where a harmonic could be reinforced by a resonance. Anyone on this last bit?


The fundamental is only highest in amplitude if you strike the drum a certain way . With an off-center rimshot the overtones will be stronger.

With timpani, the lowest vibrational mode of the mebrane/drumhead is suppressed by the bowl shape and due to the off-center striking point higher modes ("overtones") are the predominat frequencies, acting as fundamental tone. There has been a lot of research if and how resonance of these modes is amplifide by the shell cavity. It's not easy.

With cylindrical drums, the Helmholtz resonance of the cavity is higher frequency than regular tuning (with bass drums, it's a "hollow sound" picked up by internal mics) and thuns does not contribute to the fundamental (exception: tubular drums such as octobans).The frequency of the fundamental is rather a result of the air column vibrating more slowly than that resonance frequency, due to the mass and tension of the drumhead(s).
 

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I'm not going to argue physics, but my ears could tell that the deeper of the two toms in my comparison sustained longer than the shallow tom. I didn't "perceive" anything. When I think of resonance, I think of the reverberation of a room where certain frequencies build up & become overbearing. This was not the case with the toms in my experiment.

Mike
 

Elvis

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mg,

You standardized everything else, how could it not be increased perception of resonance?
I used to make the same mistake, but now I realize what I am hearing is not just sustain.

-------------------------------------------------

Ron,

Resonance is a condition that occurs naturally within any chamber.
Just because you modify that chamber to the point to where you no longer hear it, doesn't mean it doesn't exist.
To say a chamber does not have resonance is to go against nature.
It just doesn't happen (at least on planet earth).
It doesn't require a fundamental note, overtones, undertones, spectral scans, cheese on the moon or anything else.
That doesn't mean other auditory elements can't enhance or otherwise modulate resonance, but those other conditions do not need to exist in order for resonance to occur.



Elvis
 

mgdrummer

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Elvis said:
mg,

You standardized everything else, how could it not be increased perception of resonance?
I used to make the same mistake, but now I realize what I am hearing is not just sustain.

-------------------------------------------------

Ron,

Resonance is a condition that occurs naturally within any chamber.
Just because you modify that chamber to the point to where you no longer hear it, doesn't mean it doesn't exist.
To say a chamber does not have resonance is to go against nature.
It just doesn't happen (at least on planet earth).
It doesn't require a fundamental note, overtones, undertones, spectral scans, cheese on the moon or anything else.
That doesn't mean other auditory elements can't enhance or otherwise modulate resonance, but those other conditions do not need to exist in order for resonance to occur.



Elvis
My ears aren't making a mistake, thank you very much. It's really easy to determine if one note sustains longer than another. And, if I still had the power tom, I could record each drum and I guarantee you the mics would pick up the same information.

Mike
 

cruddyeye

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I've seen more than a few comments about having hit the power toms harder to get a good sound. I'd just like to attest to that. I had a 5 ply Slingy power tom kit, all square sizes and they never sounded good in lower volume situations, but they would really shine when played hard. I always said it was like driving a truck, took more effort. I actually found some Slingy shells in standard sizes that matched the diameters of my 5 plys and did a shell transplant. I'm never looking back. I love the sound of the standard size 3 ply shells vs the power tom 5 plys. I'm sure much has to do with the shell construction, but it is what it is. They sound pretty sweet in any situation, except they're too big for jazz. I'm loving my new/old Slingys now.
 

Ron_M

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Seb77 said:
the fundamental will be frequency highest in amplitude. Harmonics are always of a lesser amplitude, although, I suppose a condition could exist where a harmonic could be reinforced by a resonance. Anyone on this last bit?


The fundamental is only highest in amplitude if you strike the drum a certain way . With an off-center rimshot the overtones will be stronger.

With timpani, the lowest vibrational mode of the mebrane/drumhead is suppressed by the bowl shape and due to the off-center striking point higher modes ("overtones") are the predominat frequencies, acting as fundamental tone. There has been a lot of research if and how resonance of these modes is amplifide by the shell cavity. It's not easy.

With cylindrical drums, the Helmholtz resonance of the cavity is higher frequency than regular tuning (with bass drums, it's a "hollow sound" picked up by internal mics) and thuns does not contribute to the fundamental (exception: tubular drums such as octobans).The frequency of the fundamental is rather a result of the air column vibrating more slowly than that resonance frequency, due to the mass and tension of the drumhead(s).
Thanks, Seb - I appreciate the comments. My thoughts were that the resonance created in a cylindrical drum is analogous to a transducer and its associated room modes of various orders. Does this hold true?
 

agogobil

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you can easily compute the relation between sustain, volume, and drum shell depth by using this formula:

dδ1(t) = σδ1 dWδ1 (t) z(t) = µz + a0t + a1 ln S1(t) dz(t) = −b(m − z(t))dt + a1δ1(t)dt + a1σS1 dWS1 (t) b = b1a1 m = −a0 − a1r + 1 2 a1σ 2 S1 b, where x is the depth (in cm)

... there's probably an app for that, but I could be wrong.
 

Ron_M

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agogobil said:
you can easily compute the relation between sustain, volume, and drum shell depth by using this formula:

dδ1(t) = σδ1 dWδ1 (t) z(t) = µz + a0t + a1 ln S1(t) dz(t) = −b(m − z(t))dt + a1δ1(t)dt + a1σS1 dWS1 (t) b = b1a1 m = −a0 − a1r + 1 2 a1σ 2 S1 b, where x is the depth (in cm)

... there's probably an app for that, but I could be wrong.
So you're saying that a drum is a very dynamic and complex system? My head hurts - lets just make assumptions.
 

cruddyeye

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agogobil said:
you can easily compute the relation between sustain, volume, and drum shell depth by using this formula:

dδ1(t) = σδ1 dWδ1 (t) z(t) = µz + a0t + a1 ln S1(t) dz(t) = −b(m − z(t))dt + a1δ1(t)dt + a1σS1 dWS1 (t) b = b1a1 m = −a0 − a1r + 1 2 a1σ 2 S1 b, where x is the depth (in cm)

... there's probably an app for that, but I could be wrong.
I got the number 42
 

Ron_M

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Joe, you hit on an answer to the question that hasn't been expressed yet; a change in feel of stick response.
 

Seb77

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Ron_M said:
Thanks, Seb - I appreciate the comments. My thoughts were that the resonance created in a cylindrical drum is analogous to a transducer and its associated room modes of various orders. Does this hold true?
Are you talking about loudspeakers in rooms? If so, yes, you could think of the drum cavity as a very small room, which leads to the explanation why the resonance is higher than the frequency range of usual drum fundamental tone:
As a rule of thumb, sound travels at one foot per millisecond (344m/s), so the wavelength of notes at 1 kHz is about a foot (344mm)
http://en.wikipedia.org/wiki/Room_modes

A drum cavity is just too small to resonate the drum fundamental, which is around 200Hz at the max (high toms, snare drums). The wavelength doesn't fit inside the drum, so to speak. The tone/vibration originates from the tensioned membrane(s) (a bit of shell influence etc.), which is the reason we can tune a typical snare/tom, or bass to a wide range of pitches.
 

Koyzumie

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Thank you so much for this detailed and informative response! I've been looking for this exact information and this really helped me to understand what was really going on in my drums.
 

LRod1707

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Wow this thread is 9 years old. Congratulations Koyzumie on actually using the search function. I must learn from your actions!:)
 


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