The chamber and throat of a Dobro resonator guitar are quite large. Look at the radial holes in the big back chamber of the Dobro. It has a large diaphragm too. The diaphragms of the Stroh instruments look similar to resonator of a Dobro.
I also design and build musical instruments including guitars with optical pickups, flutes including Irish and shakuhachi. All with complete computer models to aid in hole placement.
In any event I think this is a fun thing to look at.
I also design and build musical instruments including guitars with optical pickups, flutes including Irish and shakuhachi. All with complete computer models to aid in hole placement.
In any event I think this is a fun thing to look at.
x,
first, a big thanks to you for all the nice work re foamcore/tpa3116/good-sounding, low-cost FR drivers. I'm a big fan.
WRT the front-loaded horn with a "glove port" for the strumming hand, I was just throwing one idea on top of another for fun
in general, banjos and dobros go right to the OP topic of
'trying increase the efficiency of the diaphragm",
drum skins and resonators have a lot less damping than any wood you can think of,
the thinner you shave a wood top, the more you have to brace it.
it's why banjos and dobros were popular in early New Orleans style jazz.
In the midst of mass polyphony from trumpet, trombone, clarinet, tuba, drums, etc
--before performances moved inside, off the street,
the roles of individual instruments became more formalized,
and audiences got quieter instead of louder when the band started up --
guitars just got lost in the mix.
low mass/more freely resonating materials will always have higher "efficiency" than wood,
but once you even start to think about tone color, priorities change, and all bets are off
as to how you can achieve your goals. Lots of different ways to approach individual bridge tunings for individual strings out there on various guitar forums.
but I haven't seen any git-fiddles/banjos/dobros with a 3-foot front horn and a sealed "glove port" so yer strummin' hand can get in there and get to work without leaking all that moving air out the hand-hole. just sayin'. ;-) god bless, and good luck!
first, a big thanks to you for all the nice work re foamcore/tpa3116/good-sounding, low-cost FR drivers. I'm a big fan.
WRT the front-loaded horn with a "glove port" for the strumming hand, I was just throwing one idea on top of another for fun
in general, banjos and dobros go right to the OP topic of
'trying increase the efficiency of the diaphragm",
drum skins and resonators have a lot less damping than any wood you can think of,
the thinner you shave a wood top, the more you have to brace it.
it's why banjos and dobros were popular in early New Orleans style jazz.
In the midst of mass polyphony from trumpet, trombone, clarinet, tuba, drums, etc
--before performances moved inside, off the street,
the roles of individual instruments became more formalized,
and audiences got quieter instead of louder when the band started up --
guitars just got lost in the mix.
low mass/more freely resonating materials will always have higher "efficiency" than wood,
but once you even start to think about tone color, priorities change, and all bets are off
as to how you can achieve your goals. Lots of different ways to approach individual bridge tunings for individual strings out there on various guitar forums.
but I haven't seen any git-fiddles/banjos/dobros with a 3-foot front horn and a sealed "glove port" so yer strummin' hand can get in there and get to work without leaking all that moving air out the hand-hole. just sayin'. ;-) god bless, and good luck!
Yeah, definitely fun to look at. Fooling with both instruments and hifi gives a lot of insight IME. I did not know you were into building also. I will be bugging you for those computer models someday!😀 Mostly I make stringed stuff, but my first was a flemish/'Bruegel' style bagpipe, and it needs a new chanter.
RE Dobro: those are basically a reflex speaker with a large aluminum full range driver (under the fancy chromed cover). It's very different conceptually, being a direct radiator. Most definitely the design was influenced by the then new idea of electric radio speakers.
in the linked blog, its suggested that Dobro derived from the Stroh and other phonoviolin - assume the violins enjoyed popularity in the acoustic recording era Stroh Violin, Stroh Viol | Resonator World
thanks
thanks everyone for your input! everyone seems to be putting downs some great ideas here and i really appreciate it. 🙂
so, why is it that the multiple parallel horns of the Cornu are better then a single horn such as below? its just that a folded horn was my first instinct to go to. is it dispersion? a narrow, powerful dispersion could be a benefit. flat response? this is not necessarily an issue. i hope by the end, this will sound like a "horn loaded guitar", what ever that sounds like 😛
as i read the comments of others, this apears more and more redundant, however, here it is. below is a picture of my final, VERY rough diaphragm guitar. you can see i was trying to use mechanical advantage to perhaps create a little more xmax, but that didnt really work. i was also a little exited with how much acoustic energy may be avaliable to me, and WELL over estimated the possible xmax, as evident by the huge surround. the xmax was only around 0.3mm at best, so a stiff surround may be quite a bit benificial, as it allow energy to be stored a little longer in the diaphragm as resonances, adding harmincs and sustain and all that loverly stuff. it has since destroyed itself with time; the diaphragm has shifted up warping the surround and tightening the strings only makes this worse. its cactus atm
again as greg pointed out, the actual acoustic energy of a guitar is quite low really, its the rest of the guitar that makes it so loud. as such it is clear to me a VERY high compression ratio may be required to effectively couple the diaphragm to the air, similar to how a gramaphone has such tiny acoustic energy, that can be "amplified" using a high compression ratio and a large horn.
thanks everyone for your input! everyone seems to be putting downs some great ideas here and i really appreciate it. 🙂
so, why is it that the multiple parallel horns of the Cornu are better then a single horn such as below? its just that a folded horn was my first instinct to go to. is it dispersion? a narrow, powerful dispersion could be a benefit. flat response? this is not necessarily an issue. i hope by the end, this will sound like a "horn loaded guitar", what ever that sounds like 😛
as i read the comments of others, this apears more and more redundant, however, here it is. below is a picture of my final, VERY rough diaphragm guitar. you can see i was trying to use mechanical advantage to perhaps create a little more xmax, but that didnt really work. i was also a little exited with how much acoustic energy may be avaliable to me, and WELL over estimated the possible xmax, as evident by the huge surround. the xmax was only around 0.3mm at best, so a stiff surround may be quite a bit benificial, as it allow energy to be stored a little longer in the diaphragm as resonances, adding harmincs and sustain and all that loverly stuff. it has since destroyed itself with time; the diaphragm has shifted up warping the surround and tightening the strings only makes this worse. its cactus atm
again as greg pointed out, the actual acoustic energy of a guitar is quite low really, its the rest of the guitar that makes it so loud. as such it is clear to me a VERY high compression ratio may be required to effectively couple the diaphragm to the air, similar to how a gramaphone has such tiny acoustic energy, that can be "amplified" using a high compression ratio and a large horn.
i understand that a horn has a low frequency cut off, like an acoustic cross over i suppose, what is the slope that it cuts off at? or does it vary with different horn designs?
with any luck, it doesnt turn out like this:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Yeah, I think you're thinking along the right lines now. It will take some experimation, but that's the fun of it. 😀
One thing is worth pointing out: for maximum bandwidth, IMO you should avoid 'folded' horns. Try to keep a smooth curved pathway -- like a tuba or something. Perhaps use matboard or something for the internals. The corners are beneficial (arguably) when used in backhorns and basshorns, because they tend to block highs, but you don't want this effect.
The interesting thing about the Cornu is that it has a relatively large mouth area for a compact 'folded' horn.
awesome. i shouldnt have posted that pic i guess, what my plan was to calve a mould out of wax, with a half circle profile, and make it snake behind the "soundboard". the only corner should be the corners of the half circle.
the Cornu may be an option, i think it would need to be a diamond shape instead of square though (just rotate 45*) so all the mouths clear the neck.
do you know how many Db/octave a horns low frequency cut off is?
the Cornu may be an option, i think it would need to be a diamond shape instead of square though (just rotate 45*) so all the mouths clear the neck.
do you know how many Db/octave a horns low frequency cut off is?
fwiw - here's some response curves of vintage acoustic phonograph horns - but they were driven with a custom homemade electrical driver
The Victor-Victrola Page
am not sure about slope below cutoff - IIRC Bruce Edgar said it could be faster than 4th order in some cases of horn/driver combination.
The Victor-Victrola Page
am not sure about slope below cutoff - IIRC Bruce Edgar said it could be faster than 4th order in some cases of horn/driver combination.
Two posts deleted. sreten, you have made your point and must accept that those involved in the thread may see things differently or just want to try out their own ideas. Unless you are prepared to actively help rather than just posting negative comments then I suggest that you refrain from posting at all.
For a musical instrument, I think it's important to radiate as many harmonics as possible.
So if it's enhanced by a horn (or horn-like stuff), then the bandwidth would better be very wide.
On this viewpoint, (straight) gramphone type is indeed better than folded horns with parallel walls 😉
I would have to disagree with you on that one. I have played some awesome small bodied guitars that sound quite thin and quiet and with poor sustain due to their small sound board but also quite percussive and sounded awesome. I've also played some really large guitars that sounds warm and full that you can nearly fell the sound. but the attack of the notes was almost absent. not a good guitar for finger picking delegate melodies. but I love then both. I find most guitars are a compromise of the two.
I also like banjos, which are generally very tinny.
I expect the horn loaded guitar to sound unique enough to be worth the effort. not saying that a full sound wouldn't be awesome, but if I don't get a full sound due to compromises in the design, that could sound awesome to.
generally, I am expecting a tight percussive sound that may fall on the thinner percussive side due to possibility of needing to design a small diaphragm to make the compression chamber easier to design unless I can find a better diaphragm material.
that's my idea anyway. the sound doesn't really bother me.
Technically, from a hifi perspective, you can't make a horn that covers your desired bandwidth without it being the size of a refrigerator. If you really want to learn how horns work, read the papers by Harry Olson, Keele, Leach, et al.
However, this isn't hifi. Things like baritone saxophones cover essentially the BW of a guitar, yet aren't ridiculously massive. You will essentially be making a flared pipe.
I suggest starting by developing a compression chamber and diaphragm that works first. That's the key. You should get some results even with no horn, or perhaps a simple pipe/hose and funnel or something.
However, this isn't hifi. Things like baritone saxophones cover essentially the BW of a guitar, yet aren't ridiculously massive. You will essentially be making a flared pipe.
I suggest starting by developing a compression chamber and diaphragm that works first. That's the key. You should get some results even with no horn, or perhaps a simple pipe/hose and funnel or something.
yeah, I'm getting the feeling more and more that for someone with my experience with horns, which is low, I may just need to experiment with different horn sizes till I find what works.
before I just build something, has anyone got any ideas for diaphragms? ideally it would be flexible enough to push a reasonable amount of air within its pass band, but rigid enough to retain some resonance to help with sustain. I'm sort of bouncing between an ultra thin plywood, out maybe even 0.2mm steel sheet. (because that's what I have laying about)
I was thinking about something exotic like Fibreglass or thin carbon fiber, but when you tap those materials, they tend to have a dull sound that suggests it is good at absorbing energy which is not ideal. but I don't know what is ideal! any ideas would be really appreciated 🙂
if I get plenty of answers I'll start building this weekend
before I just build something, has anyone got any ideas for diaphragms? ideally it would be flexible enough to push a reasonable amount of air within its pass band, but rigid enough to retain some resonance to help with sustain. I'm sort of bouncing between an ultra thin plywood, out maybe even 0.2mm steel sheet. (because that's what I have laying about)
I was thinking about something exotic like Fibreglass or thin carbon fiber, but when you tap those materials, they tend to have a dull sound that suggests it is good at absorbing energy which is not ideal. but I don't know what is ideal! any ideas would be really appreciated 🙂
if I get plenty of answers I'll start building this weekend
Hi ubza1234,
I don't understand what you disagree with me. Instead, as I read your previous post (#34), your descriptions pretty much reflect what I've said.
In general, horn (or the likes) enhance the lower part of the spectrum. So if you do horn-loaded an acoustic instrument, you'd better build it light and thin sounded for a start.
Otherwise it'll sound overly warm or dark, no spark.
And that's why I said the horn should be straight, not folded. More bends, more attenuation to the HF. 😉
I don't understand what you disagree with me. Instead, as I read your previous post (#34), your descriptions pretty much reflect what I've said.
In general, horn (or the likes) enhance the lower part of the spectrum. So if you do horn-loaded an acoustic instrument, you'd better build it light and thin sounded for a start.
Otherwise it'll sound overly warm or dark, no spark.
And that's why I said the horn should be straight, not folded. More bends, more attenuation to the HF. 😉
I see.. my bad 🙂
this is one of the reasons why I suggested maybe multiple horns and diaphragms for each string may be best. there is no way I can make a horn for the lower strings that are not folded in some way, I should be able to keep it free of sharp corners pretty easily by molding the fiber glass that way, but straight horns that can do bass and treble may be quite impossible I think I'd I want it to be remotely practical.
this is one of the reasons why I suggested maybe multiple horns and diaphragms for each string may be best. there is no way I can make a horn for the lower strings that are not folded in some way, I should be able to keep it free of sharp corners pretty easily by molding the fiber glass that way, but straight horns that can do bass and treble may be quite impossible I think I'd I want it to be remotely practical.
here's a replacement mica diaphragm for an acoustic Victrola - perhaps you could write the seller telling of your proposed project and get some idea using that angle (~Stroh) can a "practical" diaphragm which carries the tension of the strings across the bridge be made to work?
Victor Phonograph Exhibition Reproducer Diaphragm | eBay
Victor Phonograph Exhibition Reproducer Diaphragm | eBay