Folded Horn Acoustic Guitar Patent # 10,777,172

Member
Joined 2021
Paid Member
Art - I checked the amp for flat response per your suggestion. I could not get it to be 2 volts for some reason.

Master up full, gain down, all tone at zero.

Increased the gain, always hit 5 volts or above.

With REW tone generator I did the next 1/3 octave, kept it going from 50 Hz to 15,000 Hz. It was always between 5.3V and 5.8V.

Is this an acceptable flat response for this test? Sweeps next. Please advise and thanks! Joe
 

Attachments

  • Amp Flat.pdf
    95.8 KB · Views: 14
Art - I checked the amp for flat response per your suggestion. I could not get it to be 2 volts for some reason.
Master up full, gain down, all tone at zero.
Increased the gain, always hit 5 volts or above.
The amp gain input is very sensitive, as it needs to be able to bring levels of -60dBU from weak inputs to full output.
With a -10dBu input, it may be too "jumpy", going from "off" to near full output when the master gain is wide open.
You can turn the tone generator level or amp master volume down further to get any output level desired.
With the amp set as it was, the REW tone generator output needs to be reduced to about -19dBu for a "one watt" test.
With REW tone generator I did the next 1/3 octave, kept it going from 50 Hz to 15,000 Hz. It was always between 5.3V and 5.8V.
Is this an acceptable flat response for this test? Sweeps next.
The difference could be voltmeter imprecision at differing frequencies, but even if accurate, the amp's output level difference is less than +/-0.5 dB, nothing compared to the +/- 15dB (or more) your speaker response probably has between 50 Hz and 15,000 Hz.

5.3V into 4 ohms is about 7 watts, 5.8V is 8.4watts.
8 watts is +9dB over 1watt (2V into 4 ohms).

If your amp clips at 15 watts, at best it has 3dB more clean output.
Amp clipping generates mostly odd order harmonics, you do not want those in your frequency response test, the speaker will generate enough harmonic distortion of it's own ;)
 
Member
Joined 2021
Paid Member
I was going to say that :ROFLMAO:

Thank you Art! It was cool to watch it run through the 1/3 octaves, and not change much, had not used that before.

More guitar body work today, then on to Pink Noise redo with sealed horns (will post/compare with unsealed horns) and Sweeps!

A friend of mine recently (September) went to a Jim Irsay (Indianapolis Colts Owner) concert (his band). He had Mellencamp, Buddy Guy, John Hiatt...performing with him. He owns guitars previously owned by George Harrison, Jerry Garcia, and he bought David Gilmour's Martin D-35 that he used to record Wish You Were Here (I think he paid 1 million dollars for that, and 4 million dollars for his Strat). He lives about 30 minutes from me, so...this is the kind of guy I need to find that loves guitars, and might be interested in owning the intellectual property for a very unique acoustic guitar. Right...good luck with that. Can't hurt to try, and I will!

BTW Wish You Were Here is one of my favorite acoustic guitar songs, string noise and all. I don't usually like string noise, but for some reason on this song it just makes it sound more human, so much soul. Plus Wish You Were Here is a stunning album. That's all it got! Joe
 
Member
Joined 2021
Paid Member
I have posted this before, and I know some people are not impressed, but how does this Bose Waveguide work? I mean it seems to be the reverse geometry of a horn. It goes from large to small, not only in width, but depth.

OK I know it can't fill a big room. I Listen to this in my small shop in the basement, sounds pretty good for the size. Today I went upstairs while it was playing, and the bass was coming though the basement ceiling pretty strong. I had some Neil Young playing, not acoustic, his rocking band. How does this damn thing work? Comments?
 

Attachments

  • Bose Waveguide.pdf
    137.2 KB · Views: 10
Member
Joined 2021
Paid Member
OK Art - the sweep data is in, let me have it! I heard the signal run from low to high.

I assume the black line is the flat tone generated by REW. My red line looks "pretty flat" at the midrange. Highs don't drop off too much, strong harmonics?
Lows are blowing up, what gives? I mean 20 Hz, what? Overall I think this might be a decent FR?

Anyway please let me know what you think and thank you! 🙏 :unsure: Joe
 

Attachments

  • Folded Horn Acoustic Guitar Sweep 1-7-23.pdf
    295.1 KB · Views: 18
OK Art - the sweep data is in, let me have it!
Sorry Joe, no idea how you get such results, but they are obviously not representative of a speaker like yours measured with a calibrated test system.
The 420 dB vertical SPL range makes it even harder to tell what's going on, limit it to a useful range, like 60-120dB.
You'll need to follow the REW manual and instructional videos to learn step by step what to do.

It would be better to start withsomething like your JBL bookshelf speakers that have a published frequency response you can compare to, so you get an idea of what to expect from a valid measurement. Those tests will also be a benchmark to compare your speaker with.

Art
 
Member
Joined 2021
Paid Member
OK same data attached but with better resolution, sorry about that. Note this is similar to what I saw with Pink Noise back in October. I will recheck and see what happened, and needs to be improved. I will also do a sweep with the cover off the horns, just to compare. As I said earlier when the horns are covered, the bass goes through the roof, compared to uncovered. The data shows strong bass, but not sure why it is so peaky. The mids not quite as peaky and the highs much flatter, and do not drop off badly, and actually go back up after 10K ??? Will be fun to play with... Joe
 

Attachments

  • Folded Horn Acoustic Guitar Sweep 1-7-23.pdf
    603.2 KB · Views: 15
Suggestion; trim your data to fit the graph in both X and Y scales. It should look more like the "thumbnail" in the upper left corner!

There's no need to start the sweep at 1Hz... Start at a more reasonable value like 40 - the low E of a Bass guitar for a little margin there. I also doubt there's any real reason to go above 10K as well. C'mon - it's a guitar amp. 20K is for HiFi - and half the people listening can only hear half that bandwidth if they're lucky.

On the vertical side, the bottom should be zero DB. That should roughly correspond to the background noise level of wherever it is you're making the measurements; hopefully at a time where traffic has died down, no one is watching TV or running the wash elsewhere in the house. The DB measurement of the best level of Silence you can get. It's fine if it's a number of DB above zero and would be good to include along with the speakers on plot.

That way, a remote observer of your data can see how loud you're playing the speakers above a, presumably, ordinary "silent" home background level, which is common and relatable to.

On the vertical side, the top graph value should be about the DB level of the highest peak. Maybe leave 3-5 DB to "frame" the measurement a little nicer, with a small margin of white space between the highest peak and the top of the graph.

These are easily adjustable in REW and I see you already know how to do it.
 
Note this is similar to what I saw with Pink Noise back in October.
Not very similar, other than the out of bandwidth room noise in all your tests.
The data shows strong bass, but not sure why it is so peaky.
The current "data" looks more like random room noise than a speaker output.

As a basic reality check, compare the output of the driver you use driven with 2volts input (1W/1m):
TTEBM46C20N-4B.png

You could expect the horn to provide peaks as much as +6dB over the front loaded driver, and a reduction of -6dB or more in the upper range if you do a similar test.

Best of luck figuring out what is wrong with your test procedures.

Art
 
Member
Joined 2021
Paid Member
What do you know, I just looked up the Tectonic driver at lunch today, recognized that FR right away.

Thank you Art and JJ, I will consider and revisit for sure! My bass gets stronger by ear for sure, but not that much stronger, not above the mid.

I am used to recording fairly loud guitars, or iPhone music, but sweeps are very sensitive, I need to be more careful. Today I wondered if my laptop fan kicked on, or the furnace, or a car on the street, as we live on a main street, traffic comes and goes.

I know it probably sounds a little pedestrian, but I am happy that I can set up sweeps right away now, then concentrate on the measurements.

I was hoping to get 20,000 hits by the end of January, but have that today!

Anyway thank you much gents, I will review your suggestions and keep going! Joe
 
I am happy that I can set up sweeps right away now, then concentrate on the measurements.
By the end of the year, it'll be like tying your shoe. Get yourself a Dayton DAEX25FHE and you'll be sweeping everything.

Seriously, you'll certainly want to know how the top of your new guitar behaves acoustically with whatever bracing scheme you choose; 3 fan, 5, fan, 7 fan, ladder / lattice?

From my experience, that little Dayton DAEX25FHE could help out in figuring out what's going on with the guitar's top. Measure, shave / shape the braces, measure again. Hope all those screws come off and back on 100 times before the threads fail!

I have this little Yamaha APXT2; a sort of travel guitar sized instrument. Acoustically, sounds like a little cigar box with strings. However, when you plug it into an amp, Yamaha apparently figured out how to make it sound like a much bigger acoustic-electric guitar. So there's that "fix it in the electronics" possibility too.
 
Today I wondered if my laptop fan kicked on, or the furnace, or a car on the street, as we live on a main street, traffic comes and goes.
That type of background noise could be what you posted.

We stayed at a guest house a few years ago with a heat pump which resonated around with noise at similar levels to yours, the 30 Hz range made me do a screen save, don't normally hear that in systems without long ductwork.
New Orleans Heat Pump, Joe's Room Noise.png


With a sine wave signal of 2 volts into your speakers, even at one meter their level should be 40dB or more over the noise for most of the range.

Art
 
Member
Joined 2021
Paid Member
Wow, very similar Art :unsure: amazing what can be picked up and recorded.

JJ- exciter for top, oy...:ROFLMAO: 100 times for threads, I hope not, OK maybe 30...Rock Maple is hard, softwood, not a chance.

The only place slower than me is the USPTO. I filed my second patent (on this instrument) eight months ago. They were supposed to respond in six months. I do have FITF (first inventor to file) status, so safe!
 

Attachments

  • Patent Info.pdf
    477.1 KB · Views: 11
Well, your top and its braces cant hit the dividing board covering the horns. The guitar also cant be monsterously thick, which doesnt leave a lot of cabinet space between the two. So I doubt you'll get the first resonance at 100 Hz, which is the sound hole / body cavity volume resonance. That leaves the next one at 200, then again at 400 Hz or so, which is typical from what I've seen among guitars I own.

As I mentioned in my other thread, when these resonances are pushed sharp, relative to A 440 and its subharmonics, the guitar sounds boxy to me. I got rid of one because its first top - not sound hole - resonance was something like 260 Hz and it sounded like a toy, though it looked like a full size guitar. I for one seem to like this particular resonance at or a smidge above 200 Hz.

Since you wont be getting the 100 Hz sound hole resonance, due to lack of cabinet volume that a normal acoustic has, I'd say you might as well just leave it out - have what would appear to be a solid top guitar with no sound hole. I know you'll do what you want, but there is some logic to the above thinking. How would one brace the bottom side of a non-laminate acoustic top to hit 200 Hz? I have no idea - only the test method which can show whatever it ends up at.
 
Member
Joined 2021
Paid Member
Well JJ, I like the idea of leaving out the sound hole. In fact my best top does not have a sound hole, and I will use this top to string up the guitar - wood safe! It provides more strength to the soundboard, and as you mention has other benefits. The volume is actually not much less than a standard dreadnought, since it is much larger in area, but yes not as much depth. My laminated Martin is smaller than a dreadnought, and less depth, sounds pretty good. Also the Fender Acoustasonic has a sound hole and a sound chamber that is pretty lame in volume. Not sure how it sounds, but I have my doubts about it sounding good acoustically. Plugged in, I am sure it is great. Oh yeah, and the Ovations have small sound holes as everybody knows.

I attached a previous post, and also the same data using better REW resolution, pretty dramatic from a visual viewpoint. Hey this is only marketing comparisons. Not everybody that might want to buy this guitar will be an Audio expert...etc...they might be more like me, a music lover, guitar player, and a NON-Audio expert :ROFLMAO: Comments welcome as always and thanks! Joe
 

Attachments

  • 12-9-22 Sealed Horns and Acoustic Guitar Only Better Resolution.pdf
    386.6 KB · Views: 10
  • 12-9-22 Sealed Horns and Acoustic Guitar Only With Notes.pdf
    326.9 KB · Views: 9
Member
Joined 2021
Paid Member
About the sound hole, I need it for the magnetic pickup, which I must have, conundrum.

I drilled many small holes in the body itself for the soundboard. Must center drill and keep on exact center, went well. Did not get them all done before dinner, some progress!

Hope to work on REW tonight, also making progress on a recording, look for a .pdf file as JJ mentioned, that you can actually hear :unsure:
 
About the sound hole, I need it for the magnetic pickup, which I must have, conundrum.
It's not that tough. I've seen them mounted to the end of the fretboard. You could also put it on a "post" mounted to the dividing board, hopefully above that thick part between the horn routing, making a cutout for it so the top can vibrate freely around the big heavy mag pickup. If you load the top with the pickup weight, it wont sound as good.

Even Gibson made the mistake of putting metal screws in the saddle one time and that added weight was enough to dull the guitar's sound.