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Post by svart on Nov 29, 2016 7:15:57 GMT -6
I still disagree with this theory. The inverse square law dictates that there is no way that an enclosure panel sympathetically moving <1mm can effectively change the tone of a speaker being driven to move 5mm-10mm. Besides, I posted my findings in the post before last where I swapped speakers in boxes and found that there was almost no difference in tone in the different boxes, at different powers. The only difference was change in low end response from the volume/closed/open nature of the box, and that was minimal. I don't think that the inverse square law is applicable when there's a direct mechanical coupling involved. Also it's not necessarily the amount of physical movement of the panel affection the speaker as much as the moving mass of that panel relative to the much lighter mass of the speaker cone(s). Also, saying you found "almost" no difference in tone doesn't really mean much of anything as your results really only apply to the specific cabinet constructions you used and cabinet involvement does not occur at the same volume level on all cabinets in which it is a significant factor, which makes it rather difficult to set up a direct comparison. It's also one of those things where even cabinets of the same make and model might not behave in exactly the same way - we're dealing with wood here, which is not a homogenous material. Again, think in terms of the acoustical properties on an (acoustic) guitar body - two guitars of the same model can sound quite different; one might be a dog and another might be magic. Haven't you ever encountered a situation where one speaker cabinet has something "special" about it that a similar cabinet lacks? Everything matters. The propoprtions in which things matter relastive to each other depend on the build and the situation. Well you're right about one thing.. Mass does factor into this.. But inversely to how you think. Mass resists movement, so the higher the mass, the lower the upper cutoff point is. This is why they make soundproof walls from heavy materials.. Also, the size of the panel dictates the lower cutoff point of vibrational frequency, so now you have a mechanical bandpass filter if you don't even factor in the structural rigidity of the materials that it's made from. If you tap the panels of the box, you'll hear the frequency makeup of what the box vibrations might contribute to the system. Not very broadband, nor loud is it? Just kind of a high-Q, high-mid frequency "thump" for most boxes. And yes, I've found a cabinet that was "magic", but I had always assumed it was the combination of air volume, matched compliance and speaker selection. Now I'm certain it's mostly speaker selection for tone and box volume for low extension.
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Post by johneppstein on Nov 29, 2016 13:30:10 GMT -6
Well you're right about one thing.. Mass does factor into this.. But inversely to how you think. Mass resists movement, so the higher the mass, the lower the upper cutoff point is. This is why they make soundproof walls from heavy materials.. Also, the size of the panel dictates the lower cutoff point of vibrational frequency, so now you have a mechanical bandpass filter if you don't even factor in the structural rigidity of the materials that it's made from. Au contraire, mon ami! It's not inversely to how I think at all, you're quite correct - at lower volumes. However when you reach a point where enough energy is being pumped into the speaker to overcome the inertia of the cabinet panels then resonance of the panels becomes sufficient to reflect (not sure if that's really the right word) back into the cone and affect the timbre of its output. It could also be enough to affect the sustain at certain frequencies. You could say the same thing about tapping the body of a guitar or the soundboard of a piano. There's a big difference between applying a single low frequency transient pulse and exciting a panel with a broadband sustained signal. I cdould be wrong about this, but I'm getting the feeling that you don't do much recording of REALLY LOUD guitars and so probably don't really get into the territory that Slipperman is talking about when he discusses cabinet involvement. Also, it depends a lot on the design of the cabinet and the materials involved.
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Post by svart on Nov 29, 2016 14:05:44 GMT -6
Well you're right about one thing.. Mass does factor into this.. But inversely to how you think. Mass resists movement, so the higher the mass, the lower the upper cutoff point is. This is why they make soundproof walls from heavy materials.. Also, the size of the panel dictates the lower cutoff point of vibrational frequency, so now you have a mechanical bandpass filter if you don't even factor in the structural rigidity of the materials that it's made from. Au contraire, mon ami! It's not inversely to how I think at all, you're quite correct - at lower volumes. However when you reach a point where enough energy is being pumped into the speaker to overcome the inertia of the cabinet panels then resonance of the panels becomes sufficient to reflect (not sure if that's really the right word) back into the cone and affect the timbre of its output. It could also be enough to affect the sustain at certain frequencies. You could say the same thing about tapping the body of a guitar or the soundboard of a piano. There's a big difference between applying a single low frequency transient pulse and exciting a panel with a broadband sustained signal. I cdould be wrong about this, but I'm getting the feeling that you don't do much recording of REALLY LOUD guitars and so probably don't really get into the territory that Slipperman is talking about when he discusses cabinet involvement. Also, it depends a lot on the design of the cabinet and the materials involved.Resonation and reflections are two very different phenomenon though. Reflections work better when the cabinet panels are more rigid, as the more vibration prone they are, the more power they remove from the pressure wave. Pianos work primarily by the strings vibrating the air mass within the cavity. You certainly don't want the body of a piano vibrating and emanating odd harmonics into the world. This is why a lot of pianos have suspended string trusses inside the main body, to limit vibrational transmission to the body shell. Tapping is a perfectly reasonable way to determine box density and therefor vibrational quality.. When you can link the timbre of the tap to the acoustical properties of the box. The wood is extremely lightweight, but the main acoustical gain comes from the sound hole and excitement of the air volume inside, not from the wood vibration. Nah, I only do metal and indie rock recording.. Nothing loud at all!
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Post by johneppstein on Nov 29, 2016 15:42:22 GMT -6
Well that's why I said "if that's the right word" concerning "reflection" - I wasn't refrerring to reflection through air but rather the mechanical energy of the cabinet panels being transmitted back into the diaphragm of the transducer via (more or less) direct mechanical conduction. I think you could refer to that as a form of "reflection" although it's not the usual sense of the word. (Ain't semantics a bitch sometimes?) Well, no, they don't. Pianos (real acoustic pianos) work by the strings vibrating the soundboard, which resonates in sympathy with the strings. The soundboard moves the air. In instruments like the guitar and other stringed instruments the back and sides also resonate in sympathy with the soundboard (top) of the instrument - to a lesser degree in most fretted strings like guitars, but members of the violon family have a soundpost to directly couple the back to the vibration of the top, so the entire box is vibrating. And what moves the air? Not the strings - the transfer of energy from string to air is very poor. It's the body of the instrument (primarily the soundboard in a guitar or piano, but, as mentioned above, not in all stringed instruments.. In the Japanese koto almost the entire instrument is soundboard.) A skilled builder can determine quite a bit about the properties of wood by tapping, but the tap does not give a full picture of the acoustic properties. It's kinda like doing a rough evaluation of room acoustics by clapping. Heh-heh.... OK.... But just because something is "indie" or "metal" doesn't mean it's really loud - not anymore. I've noticed a marked tend over the last decade away from the really loud guitar rigs of yesteryear in favor of smaller, more portable rigs that don't really achieve the kinds of levels Slippy's talking about in his article. "Really loud" isn't as loud these days (and to me a lot of the excitement has slipped away with it.) Hell, some thrash metal/shredder bands aren't even using real amplifiers anymore! What people regard as "really loud" is relative. I know some people who do a lot of that sort of music who say you really can't get proper cabinet involvement with less than a 100 watt tube amp - while a 50 watt head will generally sound about as loud it's not quite enough to get the cab moving well. I have not investigated this myself, as I said before I'm mostly doing country and a little blues these days, my punk and metal days are pretty much done. As an aside to all this, I've also heard of some people putting a secondary mic on the back of a fully enclosed 4x12 to get "cab tone". Read more: realgearonline.com/post/new/6222#ixzz4RR3UL2d6
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