Yes I hear that JJ, not sure when I can get in, but I will see how much my guitar projects just acoustically, and then of course with the horns, and then the horns and a mic (or two) through a PA. I have been wanting to try this for some time!
Has anybody hear about this? I think it is a pretty cool idea. Since there is zero data, based on my soundboard work, my guess is it adds 5 dB at best. Not bad, but nothing to write home about.
I have a couple guitars that could use it. I'm happy to see it's just $67, not $450 like Bagg's pickup. I could actually invest in one to help sell a guitar, an otherwise nice Martin built Goya with a little high action from some bridge lift. They say that relaxes back into as built position, after you install one of these. Hmmmm...
JJ - if you get one and measure the difference, I would be interested in seeing that data, I might get one myself. Probably not a stunning power gain, but even a possible 5 dB increase at that price is not bad!
Art - I have a question about your Keystones, and horn speakers in general. Since your Keystones have a huge amount of power, I was wondering if you ever measured or observed how much power is coming from the horn mouth vs. the sides and back of the cabinet.
My guitar is not an apples to apples comparison of horn speakers of course, but they do have similarities. When I play, I stretch my neck and put my ear on the soundboard, strong, but not as strong as the dB directly at the horn mouth, and of course this includes the hollow body guitar upper chamber. My ear on the side of the guitar can hear a pretty good amount of power also, but not as much as the soundboard. I measured this before, and no surprise, the horn mouths were the strongest, then the soundboard, then the back and sides.
But what I can clearly hear when I play, is the soundboard and power from the sound hole. My horns are of course covered, and in this case by a 1/2" thick piece of Baltic Birch (chamber divider) that is screwed on top of the horns very tightly. The sides of the chamber divider are not a 100% perfect fit, so this may contribute also. With speakers this would be bad, but with a folded horn guitar, it actually seems to a pretty damn good situation.
This leads me to believe the chamber divider is a second soundboard. Not a typical sound board with strings and a bridge, but this thing is definitely vibrating strongly from the horns. It sounds great, and goes right up to the guitar players ear. I did not really expect this, but I love it!
It seems this guitar just keeps getting better, the mag pickup closer to the strings is a great improvement. The guitar must be in perfect tune, just one string off by the slightest amount is so much more noticeable than a standard acoustic guitar. When it is perfect (if there is such a thing) and my fingers are warmed up after at least 30 minutes of playing, great sound!
My favorite test: turn the horns off and listen to the lack of power, wow, what a great comparison. I find myself playing with such a lighter touch, due to the great power. Then play with this lighter touch without the horns, weak! Then of course one starts playing harder to get more volume, only bad things happen then.
I would be very interested in your thoughts!
My guitar is not an apples to apples comparison of horn speakers of course, but they do have similarities. When I play, I stretch my neck and put my ear on the soundboard, strong, but not as strong as the dB directly at the horn mouth, and of course this includes the hollow body guitar upper chamber. My ear on the side of the guitar can hear a pretty good amount of power also, but not as much as the soundboard. I measured this before, and no surprise, the horn mouths were the strongest, then the soundboard, then the back and sides.
But what I can clearly hear when I play, is the soundboard and power from the sound hole. My horns are of course covered, and in this case by a 1/2" thick piece of Baltic Birch (chamber divider) that is screwed on top of the horns very tightly. The sides of the chamber divider are not a 100% perfect fit, so this may contribute also. With speakers this would be bad, but with a folded horn guitar, it actually seems to a pretty damn good situation.
This leads me to believe the chamber divider is a second soundboard. Not a typical sound board with strings and a bridge, but this thing is definitely vibrating strongly from the horns. It sounds great, and goes right up to the guitar players ear. I did not really expect this, but I love it!
It seems this guitar just keeps getting better, the mag pickup closer to the strings is a great improvement. The guitar must be in perfect tune, just one string off by the slightest amount is so much more noticeable than a standard acoustic guitar. When it is perfect (if there is such a thing) and my fingers are warmed up after at least 30 minutes of playing, great sound!
My favorite test: turn the horns off and listen to the lack of power, wow, what a great comparison. I find myself playing with such a lighter touch, due to the great power. Then play with this lighter touch without the horns, weak! Then of course one starts playing harder to get more volume, only bad things happen then.
I would be very interested in your thoughts!
You could experiment with the thinness and material of that "separator board" - along with the 10,000 other things to do with this invention, to improve it.
At 1/2", I'd certainly entertain figuring a way to make the guitar 3/8" thinner overall, or increase the volume of your upper chamber, keeping the same body thickness. I bet there's some material at 1/8" that would still be really stiff when glued onto that horn routing structure.
At 1/2", I'd certainly entertain figuring a way to make the guitar 3/8" thinner overall, or increase the volume of your upper chamber, keeping the same body thickness. I bet there's some material at 1/8" that would still be really stiff when glued onto that horn routing structure.
The Keystone is a low frequency "tapped horn", not really a horn in a traditional sense.
Regardless of construction, or whether a horn or direct radiator, omnidirectional low frequency waves will wrap around the cabinet.
At 30-60Hz there would be hardly any difference in level at a few meters from the mouth (or a direct radiator) whether in front, to the side or rear of the cabinet.
The actual transmission of low frequencies through 3/4" plywood might be as low as -20dB, though I'd as a guess say the output through well braced horn or cabinet walls would be more in the -40 dB range compared to the intended exit.
Looking at a high frequency horn's polar response we can see over 40dB off-axis reduction at the high frequencies:
The ME464 horn walls are under 1/2" thick other than around it's braces.
Wood vibrations may be in or out of phase with the sound board, horn, or sound hole output, overall the net output over the guitar frequency range from the chamber divider is pretty negligible.
The 1/2" thick upper horn wall is probably not contributing much direct output, but certainly is reflecting much of the soundboard's output.
Amplification does allow a wider dynamic range to be audible.
If correct, you may want to experiment with mounting your mag pickup to the chamber divider, instead of hanging it on the edges of the soundhole. Kinda like a solid body mounts its mag pickups. Now this may require some thought; hopefully one of those thicker wood parts in the horn routing ends up right below the soundhole, so that the pickup attach is through the divider, then into a thick, meaty part of the horn routing structure.
Every sound hole mounted pickup gets some of its input from the top vibrations. Up by the neck, maybe not so much as to be acceptable. But not as good as if the pickup were physically referenced to a large, independent mass having the least vibration of its own possible; that should give unfettered access to the string vibrations only. Without the sound being some combo of strings and top. Like every other acoustic guitar that sound hole mounts the pickup; "tap the top" and tell me it doesnt come right through the amp.
Doing that also opens up patent-land for a very unusual mag pickup design. Down there, you have all the room in the world for magnet and coil, because you're no longer restricted to something that must reasonably fit into the sound hole. What's the depth from string to divider board, 2.5"? Who says you cant have 1/4" pole pieces sticking up that far, to allow the strings to modulate the pickup's magnetic circuit? Or a metal blade? A 1/8" thick blade sticking up through the soundhole would disrupt the airflow a lot less than a whole pickup hanging within there.
Mounting it to the divider board over a thick part of the horn structure would also reduce feedback susceptibility from horns -> soundboard -> pickup, which I assume would vibrate in response to horn acoustic output far easier than the 1/2" divider, held fast by glue to all those edges of the horn structure routing.
I know you prefer off the shelf solutions. I see an opportunity to invent something, that your other invention can take advantage of. I dont know anything about magnetic circuit loss when perturbations are conducted along some length of magnetic material. Maybe nothing, maybe "-3db", maybe -infinity for all I know. Maybe requires some special shape in the conducting pole; so much to not know and investigate.
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Magnetic pickups for electric or acoustic guitars are specifically designed to only pick up signals made by the steel strings. You can slip a piece of wood between a magnetic pickup and the strings, or hold it by hand above the strings and it's output will sound the same.
If you removed the strings, a wooden hammer beating the guitar to kindling would produce almost no electrical signal.
Since the magnetic pickup doesn't pick up wood vibrations, there would be no sonic advantage to remote location, which would reduce signal to noise ratios.
As an alternative to piezo transducers, a magnetic moving coil contact microphone can pick up wood vibrations while excluding most air vibrations, but mounting any contact pickup in a place that vibrates less from the strings would reduce it's gain before feedback while reducing signal to noise ratio.
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JJ- 3/8" might work. I know that 1/4" does not work, feedback! Then 1/2" works great! Yes it will feedback on 9-1/2 volume, but I don't want to play up there anyway (usually)distortion! Or I should say playing at 8 volume clean is great, not clipping, but sometimes I do want to rock and screw the clean sound, and let it distort, just keep your hands on the strings to prevent howling feedback, but use it...really electric guitar territory at that point, but still fun!
Art - I think this may be happening in my guitar, the sound is everywhere. But of course the guitar is very close to me, nobody hold a horn speaker in their arms as it rocks. 😎
Yeah this is interesting, the chamber divider being a reflector as you note Art, but a vibrating reflector, I mean vibrating from the horns before it vibrates from the soundboard reflection, eh? Not sure I can understand that in full...how is phase playing a roll, very big I know, but hard to measure. My ears like it!