Folded Horn Acoustic Guitar Patent # 10,777,172

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Hello Art - yeah, I am on OK player, that is it. Glen Campbell is a great guitar player, underrated, plus Cat Stevens played an Ovation at times.

I am thinking when my guitar uses an external mic to a P.A. I can mount it on one of the horns. Also my wood body is 1/4" thick, so much less resistant to cracking, humidity...but heavy.

When finished I will post for sure, I feel like I owe you something for all your input. You really challenged me and helped me improve, thank you! Joe
 

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Folded Horn Acoustic Guitar

I finally cut off the excess wood and have two speakers mounted, just with tape for now. I mentioned how great the bass is, and I now believe it is due to capturing 1/4 wavelength. 90 Hz wavelength is approx. 10 feet. The folded horn portion is approx. 2-1/2 feet by design, before the sound wave hits the sound ports and then the horn on the end, which is five feet total. The sound ports go from small to large, following the horn shape, and keeping relatively consistent dB throughout the guitar. I hooked my iPhone up to a small amp, that feeds two speakers, incredible sound for a guitar body, truly like a speaker cabinet. The question now is can I repeat the great frequency range from the guitar itself, using a mic/pickup/transducer/equalizer/amp/speakers in such a small space? Stay tuned!
 

Attachments

  • Folded Horn Acoustic Guitar Updated Nov 2021 Body With Speakers.pdf
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Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Pics attached of guitar body and how enclosed folded horns affects tone. Incredible lows with these horns,
but need more highs. Not a problem, have ideas, but would love to hear ideas from others. I am cutting
the soundboard now, hope to be done next week, one piece of Baltic Birch. Going better than expected, again.
I am waiting for a big problem to hit me, but it is not happening yet, very surprised! Videos to follow, not sure
how well I can capture the sound on an iPhone. Thanks! Joe
 

Attachments

  • Folded Horn Acoustic Guitar Updated Dec 2021 Tone.pdf
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Joe,

You might recall my observation from post #40- the horn entrance front chamber is large, which creates an acoustic low-pass filter ("high cut equalizer").
Reduced bandpass chamber.png

Mounting the driver in an "offset horn" fashion as in the upper portion of the modified depiction above would improve the high frequency output.
That said, an offset horn still won't do very well for the upper harmonic range compared to a straight horn with a proper throat to mouth expansion ratio.

Woodwork looks nice!

Art
 

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Thank you Art! I will try that for sure. I have seen this in horn speakers, and was wondering how I could improve the entrance front chamber.
It is easy enough to test now, and I can also include in production. My horn expansion ratio can be improved, thinking about how it
affects manufacturing, can be done, but not to the level I would really like to see. Frankly, I wish I had another two inches of height to work with,
but the guitar would be too large to hold and play!

I opened the area behind the speakers (cut hole through chamber divider), so the sound can come out the back of the speakers also (can port through chamber divider and soundboard - this may be the soundboard hole). Prior to doing this, the lows through the horn were wonderful, but I did not have enough highs and mid, does this make sense? This way I can lose all the multiple ports on the sides (OK maybe one more per side). After looking at designs for this, I decided it did not look great.

The sound with tonewood sounds wonderful. The same speakers through a plastic pipe (wave guide) sound terrible. What do you think of how this wood affects sound, and the resonance of 1/4" thick hard maple? I am getting into tone here, and trust my ears, but really don't know how to measure this with data.

I have made mistakes, and also learned some great methods on the manufacturing side. I now know how to make the body. I will keep these as
trade secrets, as they are not part of the patent, and not on the audio side of the discussion. Thanks in advance for more comments from you, and others as well. I appreciate it very much!! Joe
 

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Hello Art - let me know what you think of this design change. I definitely could use more high end, so I hope to test this tomorrow.
My biggest challenge: do the changes based on proven acoustic theory work, of course they do. Given the limited space I have
to work with, inside an acoustic guitar, will it be enough of a difference to hear? Testing always tells, stay tuned and thanks! Joe
 

Attachments

  • Folded Horn Acoustic Guitar With High Frequency Improvement.pdf
    131.3 KB · Views: 20
Hello Art - let me know what you think of this design change.
Given the limited space I have to work with, inside an acoustic guitar, will it be enough of a difference to hear?
The chunks of 3/4" lumber should help a little, but are only half of the changes suggested in post #126. The improvement should be audible, but not great, by any stretch of the imagination.

Space limitations are not killing the high frequency output, lack of a proper horn throat expansion and transitional bends are.
 

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Agree, could not hear a difference with the small wood change. My high frequency output is acceptable, because I am getting it through the back of the speakers, which do not go through the horn/waveguide. Plus I get it from the soundboard itself. I always thought the four lower acoustic guitar strings sound great, and B and high E strings sound tinny, never liked that, ever. I am going to try nylon strings on those two only. Since the only speakers I can fit are Tectonic 3" BMR 20 watt, I am far more concerned about getting mids and lows through the horn/waveguides. The speakers have a frequency range of 150Hz-20,000 Hz, so highs and mids are great from the speaker itself. The lowest frequency of an acoustic guitar is 83 Hz, so I need to accentuate lows. I know the length of the horn/waveguide is doing this, and really saving this guitar. I tested with only 1-2 feet of horn/waveguide length, even with a bigger bell, not even close. Like I said before, play this without the chamber divider (horn/waveguide tops are open, so do not exist at all) sounds OK. Add the chamber divider to close the horn/wave guide, and sound difference is stunning. Lows go though the roof. EQ is essential.

I can not make the horn/waveguide go from a smaller to larger taper due to CNC cutter diameter to length ratio, need a big sturdy cutter to cut this beast 5" deep. I can add wood and make the taper much more substantial, from the speakers to the bell, but that will take several pieces of wood at different thickness with taper, and join them all together, to give the horn true taper through its length as you note. I am going to try this next, it could provide a substantial difference in frequency response and dB level, stay tuned!
 
Hi Joe,

What a remarkable, beautiful bit of work you've put into this! And CNC skills to the moon! Wow. Can you see how green I am?

But please, close the loop soon -- it's time. The conducted and acoustic feedback is going to swamp maybe 90% of the subtleties that you've been so thoughtfully and carefully evaluating. It'll be even more true since you intend to use a mic for the source, since it's precisely the 'acoustic guitar sound' that you're after.

Much as I hate to kick sand on such a beautiful body (pun intended) and project, I think you'll be shocked at how much the multiple feedback paths corrupt any tone you set out to achieve. A 1/3 octave graphic has been along every gig I've done for 47 years, but Max Gain Before Feedback will come in well short of the stated objective. And the EQ required to get even that, will make a mess of the timbre.

Granted, it isn't complete enough for exclusively closed-loop (with the sole signal source being something on or in the instrument) testing. But maybe you could judiciously mix in some mic or pickup signal, to your recorded stimulus. It's gonna change EVERYthing . .

Still, that work is REALLY nice.
Cheers
 
Last edited:

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Thanks much Rick, I appreciate the great feedback! I have many places I can put the mic and keep it away from the speakers,

especially given this is ¼” thick maple, but I am prepared for mic feedback disappointment. Testing shows a pickup can produce

great sound, but only if an EQ is used, and also with help from the natural soundboard, so I am not hung up on using a mic like

I was before. I am also writing a second patent to cover changes I am making as I test my assumptions, which are of course

always wrong in some way, for all of us. The reason this is taking so long, is because I work long hours, and only have so much

time after work for this project, although it is something I love to do.



I am cutting a second body now, because I need it for marketing reasons, I need to show the guts and explain how this works,

while somebody is playing the guitar, which shows almost nothing of this invention, due to all being internal. The hard part is complete,

neck is next, then assembly. I know a pickup does not feedback anywhere near as much as a mic, so through some crude testing with

speakers dropped into a finished guitar, I am confident that will work, mic not so sure. I also blow music through this body from my iPhone cranked

up through the speakers, and am able to hold it like a guitar, you can feel the power. I keep telling myself, patience grasshopper!



When I dropped a speaker into a regular guitar with a mic, yes it did feedback. When turned down low it did not feedback, but the speakers

rang and echoed anyway, sounded terrible. The horns solve that problem. Doing this with a pickup did not prove to be a problem.



My soundboard is lighter and stronger, so that alone will be louder than a regular guitar, and that is always part of the output. This does not

need to be turned up to 10 to work, having it on 5 along with the natural sound it far louder than a regular guitar. Also adding sound ports

on the side will help music escape from the body. The fact is nobody knows if this will work 100%, that is what makes it exciting. I have not spent

lots of money, just much of my time, which is a joy, so if it does not work, that’s life. That is not going to stop me from inventing and trying.



I also try to hold the body with another guitar to get the pickup as close to the speakers as possible, that is very difficult of course, but it does

not feedback. Stay tuned and please keep the comments coming, I value constructive criticism, it helps me learn! Trying to close the loop! Joe
 

Joe K

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Paid Member
2021-08-14 12:12 am
Indianapolis, IN.
I got a little worried and just did another feedback test, as I have not tried with my new amp yet. When I have the amp up to 7, which is
as loud as I like to play, to not get distortion, and my Taylor volume up all the way, zero feedback. I put the bridge/piezo from the guitar
I was playing directly behind the speakers in the folded horn guitar, even closer than they would be in the finished product, zero feedback. Ok I am pretty sure you could not do this with a mic, so I concede that point. I then turned the amp up to 10, still no feedback. This is just a small Roland portable battery powered amp, 5 watts per channel, not a big powerful amp. I will rip the guts out of this and mount them inside my guitar, so good experiment. The only way I got feedback was when everything was turned up to 10, then I turned the bass up all the way on the Taylor and BAM, feedback. Turn the bass down half way
and feedback gone. Does this make sense Rick?
 

PRR

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2003-06-12 7:04 pm
Maine USA
this design change.
Still not there. Read this: https://www.centauriaudio.com.au/diy/plugs.html

First picture: the volume A times B, against the cone mass, defines a resonance. Frequencies higher than resonance will be filtered-out. To a rough approximation, compare this front volume and its F against the typical back (box) volume and F. If we have 50 cubic inches in back resonating at 100Hz, and 1 cubic inch (3" cone) in front, resonance is about 350Hz and treble will be awful. 1 cubic inch may be a 3" cone with 0.14 space between cone and phase plug..... your big space may be resonating far lower (though also low Q).

The rough approximation assumes very small horn throat (for best loading of heavy diaphragm); the approximation fails for large throats (which are typically much less efficient). There are other factors which make the filtering not as bad as I have sketched. But you should study REAL HORNS, not from a bugle-based length theory, but how a century of speaker science evolved.
 

Joe K

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2021-08-14 12:12 am
Indianapolis, IN.
Hello All - I just received another patent for a different guitar design: Floating Soundboard Acoustic Guitar Patent # 11,232,770.

This is all acoustic, no electronics. The goal is to see how a free floating soundboard will increase volume. Baltic Birch again for
light but strong properties, totally unknown how it will sound, lets go! See attachment for floating section view.

Back to the Folded Horn Acoustic Guitar. I have placed the piezo pickup as close to the speakers as possible, zero feedback
at guitar volume up to 10, and amp up to 7. If the amp goes up to 10, FEEDBACK! I don't want it that loud anyway, far too
distorted, so I will limit the potentiometer for gain. That said, when you do get close to 7, it sounds more like an electric
guitar, don't take your fingers off the strings, and pretty nice controlled feedback for solos, did not even think I could
do that with an acoustic guitar.

Tested a mic, no feedback before volume 5, after that TOAST, no dice, feedback horrible. I hope to still add this with pot
limits also, mix it in, but no way to do 100% percent mic.

I try to come up with solutions to the problems that hit me, your ideas would be greatly appreciated. Noise gate, maybe,
shielding, maybe, we shall see.

I also attached pictures back/front of the Folded Horn Acoustic Guitar soundboard, all CNC with the exception of the bridge
backup block, good to do some things manual, whatever works. Thanks so much for your feedback - pun intended! Joe
 

Attachments

  • Folded Horn Acoustic Guitar Soundboard and Chamber Divider.pdf
    101 KB · Views: 21
  • Floating Soundboard Acoustic Guitar Soundboard February 2022.pdf
    896.1 KB · Views: 19
  • Floating Soundboard Acoustic Guitar Soundboard Spring February 2022.pdf
    37.1 KB · Views: 20

Joe K

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Paid Member
2021-08-14 12:12 am
Indianapolis, IN.
...am curious. Your idea is to do something (like a folded horn) sometimes used in 'Hi-Fi' speakers to make an acoustic guitar sound better? Who cares who plays w/who.? I'd like to see the guitar. Do It. Play it. Why are 'patents'.... relevant?
Thank you sir for your response, the goal is to make an acoustic guitar sound louder, to be able to play unplugged any where, with great volume, with other musicians, and to play very easily and get a big sound. I think a guitar already sounds great, so I am not claiming to make it sound better, I don't think that is possible, but louder, much louder, yes!

The relevance of patents is a great question, there are many views on this. My second patent was issued about 16 months after my first patent, and in that time frame there were almost 500,000 U.S. patents granted, so somebody likes them, and they issue more every year. I think the stat is about half of all U.S. patents are issued to people that are not U.S. citizens, so the world values these patents by far more than any other country, encouraging. A real Non-Provisional Patent like mine is good for 20 years. A Provisional Patent that you see on TV is good for about a year, I find those to be a joke. Plus I learned how to write my own patents, so I don't have to pay a patent attorney every time I get one, another reason this is taking so long. The first one was a real bitch, after that, not so bad. Not only does the patent legally prevent people from stealing your idea, but it gives you ownership over the same idea that some else invented, but did not bother to get a patent. I have no interest in suing people, would just try to work out a licensing deal in that situation. Now patent trolls love to sue people, and they make a living getting patents, so they can do just that. In fact they look for great products that do not have patent protection, get the patent, then sue the original inventor. I consider them to be on the same level as dung on the bottom of my shoe that I unfortunately stepped in (another reason, to get a patent, to be protected in many ways). If anybody is interested in writing their own patent, by far the best book out there in my opinion is "Patent It Yourself", by David Pressman and David E. Blau. Both are patent attorneys, both have very impressive experience, and David P was even a patent examiner, so he knows the straight dope of the USPTO. Highly recommended, especially after trying about 5 or 6 other patent books. It's like Elon Musk said when a reporter asked him how he gained so much knowledge. He said "I read books".

Does anybody out there know of a good Luthier in the Indianapolis or Chicago area that might be interested in helping me with the build/assembly/setup? I will pay them very well of course. Guitar body number two is still sitting on the CNC machine at work, but the guys got really busy and it just needs to wait its turn, slow moving as usual, but their work is outstanding, so I am very grateful. Sorry to go on so long, I get carried away, but I am very passionate about this project, and also music of course. Thanks! Joe
 

Joe K

Member
Paid Member
2021-08-14 12:12 am
Indianapolis, IN.
Hi Joe,

What a remarkable, beautiful bit of work you've put into this! And CNC skills to the moon! Wow. Can you see how green I am?

But please, close the loop soon -- it's time. The conducted and acoustic feedback is going to swamp maybe 90% of the subtleties that you've been so thoughtfully and carefully evaluating. It'll be even more true since you intend to use a mic for the source, since it's precisely the 'acoustic guitar sound' that you're after.

Much as I hate to kick sand on such a beautiful body (pun intended) and project, I think you'll be shocked at how much the multiple feedback paths corrupt any tone you set out to achieve. A 1/3 octave graphic has been along every gig I've done for 47 years, but Max Gain Before Feedback will come in well short of the stated objective. And the EQ required to get even that, will make a mess of the timbre.

Granted, it isn't complete enough for exclusively closed-loop (with the sole signal source being something on or in the instrument) testing. But maybe you could judiciously mix in some mic or pickup signal, to your recorded stimulus. It's gonna change EVERYthing . .

Still, that work is REALLY nice.
Cheers
Hello Rick - another thought regarding feedback. I can use contact piezo pickups, similar to what is used on my Taylor. My 1/4" thick maple body will resonate until the cows come home, and in turn will transfer vibration back to the soundboard, where the pickups are located. The contact piezo pickups will grab all this vibration and feedback. What to do? My second patent that has a floating soundboard gives me some ideas. Since my walls are 1/4" thick, I can easily CNC a small and shallow path into the top of the side walls. I can then use rope rubber gasket material in this, and have the soundboard just slightly above the body, to avoid vibration transfer from the body back into the soundboard, and hence into the pickups. Not thermoplastic rubber garbage that degrades over time, but actual thermoset rubber (tire rubber) that is chemically crosslinked, and does not degrade. I can glue or use screws, since I have the thickness to accept said screws. Standard guitars don't have anywhere near the thickness to pull this off. This way the soundboard can vibrate freely, actually move like a damn speaker, and have this sound captured by the pickup, send to the amp, send to the speakers, and push through the horns or waveguides that sound great. Then the body will not be able to transfer vibration back to the soundboard, and into the pickups, break the loop so to speak, and feedback reduced. What do you think? Let me have it! Joe