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Hey, jazz guitar community
I have a curiosity question: physically, why is it that hollow body guitars tend to have less sustain than semi-hollows or solids? The basic answer is that they provide more damping for the vibration, of course, but why? Where does that damping come from?
It seems like the acoustic resonance of a hollow might actually increase sustain; why does that tend not to be the case?
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05-20-2025 12:52 PM
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A simple explanation is that hollowbody guitars acoustically push more air (ie louder). That energy comes from the strings, therefore the vibration cycles don't last as long on hollowbody guitars. Of course energy can also dissipate in other ways. A less acoustically efficient system can dampen the vibration by dissipating that energy as heat. For example if you make a bridge out of foam, the string vibrations will be instantly turned into heat.
Last edited by Tal_175; 05-20-2025 at 04:13 PM.
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The fact that an acoustic instrument is louder (acoustically) than a solid body is part of the answer. In a hollow body, the vibrational energy from the string goes into vibrating the top, which shakes the air, making the sound waves that we hear. The energy from the string is converted into acoustic energy. This process dissipates the energy of the string, causing it to die out quickly.
A solid body guitar is very quiet by itself. The vibrational energy of the strings isn't going anywhere. Since the energy doesn't have anywhere to go, it lasts longer, hence more sustain.
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Ah, yes… thanks to both of you. That totally makes sense.
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Yep.
Originally Posted by supersoul
But you can level the playing field.
Take the strings off both instruments. Now they both make perfectly inaudible sounds that just goes on forever and ever
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Probably a nuanced topic. All plausible explanations, IMHO. However, there are exceptions. I have a hollow archtop that rings forever. And I have solid body guitars that don't.
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I believe though (?) some arch tops can have terrific sustain. My L5 CES does, but L5's are a different breed, and then there are acoustic L5's, L5's with 1 p/up, and then 2 p/ups............................
Maybe because there is a lot of wood and binding ??? The string energy just gets everything vibrating beautifully and synchronistically ?
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Plucking a guitar string imparts a certain amount of energy to it. In a broad sense, the faster the energy is dissipated, the louder the sound produced. The same amount of energy has to be dissipated regardless of the body type, but the speed of dissipation is influenced by multiple factors. Generally, lightly built archtops will dissipate the string energy faster than heavier built bodies, and especially solid bodies, thus will have more volume. The same amount of sound will be produced, but over a longer period, so you may hear the sound of the string a little at a time, or more quickly. It can be in one quick bang, spread out over several seconds, or anything in between. One complication is that the body isn't the only thing dissipating the energy. The tailpiece, the neck, headstock, everything, is involved, and will influence both the volume and the sustain.
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I am not a expert on L5s but I think at least some of them had parallel bracing. That might make a difference as far as sustain goes.. Originally Posted by Jimmy Mack
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What about bloom?
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the stiffer the object strings are attached to, the longer it will sustain. Originally Posted by Jimmy Mack
Any flex between the nut and bridge will absorb energy that reduces sustain. Strong magnets will also have an influence on sustain as they are effectively pulling magnetically the strings towards the pickup all of the time. Break angles will also affect energy loss axially down the string.
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I’ve most often heard bloom to be a function of Valve amps. Specifically those with valve rectifiers or output transformers unable to keep up with current supply demand of heavy use. Bloom is a slight spongy delay between delivered sound and the power supply catching up to deliver full power. Originally Posted by Woody Sound
I have not heard of a guitar doing the same because it is a percussive instrument. Once you hit (pick/strum/flick/whatever) the string, everything from that point on is energy loss coming off the string and out the sound hole or output jack. Volume only reduces as far as I know?
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Well it can be a weird phenomenon, but I have played guitars that because of their string vibrations being extended (sustained) I've experienced a kind of "bloom" to the notes. Often this happens when fingerpicking, and/or bending the strings, sometimes after picking the note. I know there are reasons for this, but I do like the effect for certain styles.
I recently ran across this happening when I pulled an old Stratocaster out of storage, with old strings on it and pretty much tuned to pitch ( I didn't plan on leaving it there that long - 5 years or more). The old strings sustain beautifully. I seem to think that because they are old, the initial attack is muted but the fundamental notes still ring and ring.
Whatever the reason it's a fun axe to play - a different flavor and feel. I hesitate to put fresh strings on it.
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Claim/premise/assumption/hypothesis: Semis and solid bodies sustain better than hollow bodies.
Question: -Is sustain a function of acoustic resonance?
Answer:
Sustain is a function of intonation and playability. (When intonation is poor, acoustic interference dampens sustain.) The ability to play chords and intervals in tune is the goal and purpose of the intonation process that involves more parameters than just sliding bridge saddles back and forth.
A guitar that doesn't intonate cannot be tuned, cannot hold tune and cannot be played in tune. If strings pitch sharp when fretted, the guitar cannot be played in tune and would therefore be unplayable. If the guitar is hard to play it's not possible to play in tune and sustain will suffer. Acoustic interference that dampens sustain may also originate from loose and rattling parts (like a pickup), not limited to hollow body designs. Bad string slots is the mother of poor tone (regardless of guitar model).
Conclusion:
Things that facilitate playability also facilitate intonation and the ability to tune and play in tune. If your archtop is hard to play (like if strings are too heavy and action is too high) sustain will suffer. If your archtop got a wooden bridge, it's not possible to slide bridge saddles back and forth and intonation must be addressed by other means.
Solid body guitars typically got adjustable bridges, fret access beyond 12th fret and light gauge strings; things that facilitate intonation and playability.
If someone chooses to have high action on his acoustic archtop, it's a tradeoff between playability and acoustic volume, loudness.
Note:
All iconic guitar models (solid body or not) and the various bridge systems (adjustable or not) were designed in an era when everyone was using a wound 3rd. These days a vast majority is using a plain 3rd on a solid body. The use of a plain 3rd may have a negative impact on intonation and sustain. (a wound 3rd is more pliable and you may find that it's easier to intonate and play a wound 3rd in tune, i.e that it sustains better.)
Also note that a one piece bridge saddle, like a wooden bridge, is made to intonate either with wound 3rd or with a plain 3rd, not interchangeable.
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BLoom:
The string is able to vibrate both parallel to the guitar top and perpendicular to it. These two modes of vibration have very slightly different frequencies (too close to hear) and different degrees of damping. The parallel mode is generally the least damped and produces very little sound because the bridge is very stiff for side to side movement. The two modes are coupled together and exchange energy. While the total energy in the string is always reducing with time after the pluck, the coupling of the modes can allow the extra energy stored in the more slowly decaying parallel mode to be transferred to the perpendicular mode. This energy is then able to produce sound so the volume can bloom even as the total energy decays.
Pickups are also much more sensitive to the perpendicular string movement than to the parallel movement. This is particularly so with rail pickups like the CC. This allows the effect to occur in the electric sound as well.
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