I have a small "Applecreek" travel guitar that I've made playable through a lot of work. I've put a magnetic pickup in it and have actually used it in shows. But some of my intended use is outdoors at things like Renaissance fairs, where all I need is a little battery powered amp so it could be heard at or slightly above the level of ordinary sized acoustic guitars. I've done that and its worked out well. See where I'm going? I'd like to try to build a whole little amp, maybe an efficient class 'D' circuit, right inside the guitar. So.. knowing that I can't expect GREAT sound doing something like that, I'd still like a fighting chance and making it as good as it can be. Can anyone recommend a small (like 3" or less" full range speaker that might work decently?
links come and go on line, but here's a link showing the guitar I started with...
Applecreek Acoustic Travel Guitar | Best Travel Guitars
links come and go on line, but here's a link showing the guitar I started with...
Applecreek Acoustic Travel Guitar | Best Travel Guitars
A full sized acoustic guitar can hit some rather surprising levels, over 100 dB at one meter is easy without really playing hard.
Smaller speakers are less efficient than larger speakers, requiring lots more power (and more battery) to achieve that level.
A speaker rated 80 dB 1watt 1 meter requires 100 watts to make 100 dB.
I'd suggest a Galaxy Audio Hot spot speaker, they are 5" nominally. The Neo magnet version (about $50) is lightweight, gets loud, sounds pretty good, and at 95 dB 1w 1m is far more efficient than any 3" driver I know of.
Art
Smaller speakers are less efficient than larger speakers, requiring lots more power (and more battery) to achieve that level.
A speaker rated 80 dB 1watt 1 meter requires 100 watts to make 100 dB.
I'd suggest a Galaxy Audio Hot spot speaker, they are 5" nominally. The Neo magnet version (about $50) is lightweight, gets loud, sounds pretty good, and at 95 dB 1w 1m is far more efficient than any 3" driver I know of.
Art
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I'm thinking of the lower part of the face, midway between the the sound hole and bridge, as close to the lower edge as possible.
Well its hard to tell this from the picture I linked, but go back and look at it, and then consider that looking at its face, the widest part of the body , measured from about an inch off the bridge (toward the sound hole) is barely 8 inches! There's no possible way to get anything bigger than 3" inside this thing without encroaching on the sound hole, and 2-1/2 would be even better.
I realize this is a long shot, and its only some of the modern speaker technology I see making small radios sound pretty good, that I even think its worth trying.
I'm not a muso' but knowing a little about the physics of string instruments suggests the speaker driver should be mounted deep inside the resonant cavity and be used to augment the resonating air column, rather than replace it like an electric guitar. With a carefully chosen amplifier frequency response I suspect you could give the acoustic appearance of a normally sized cavity, or even a chelo.
However, because it is the strings resonating with the air column there is a high risk of positive feedback through the pickup with even moderate gain. I am trying to visualise the electrical equivalent of the mechanical system and its inter-action with the electrical add-on, but alas I lack the wit.
Alternatively, do away with the resonance entirely and mount your speaker over the hole and design your electrics and acoustic output around a sealed enclosure.
However, because it is the strings resonating with the air column there is a high risk of positive feedback through the pickup with even moderate gain. I am trying to visualise the electrical equivalent of the mechanical system and its inter-action with the electrical add-on, but alas I lack the wit.
Alternatively, do away with the resonance entirely and mount your speaker over the hole and design your electrics and acoustic output around a sealed enclosure.
I think that a small full ranger suspended inside the body and venting the backside of the driver through a port to the rear might be the ticket to augment the guitar while sending rear pressure out the back so as not to cancel the forward facing sound pressure....hi-Vi makes some small impressive drivers.
regards E
regards E
Yes... I've thought of these things. As another responder (Pano) mentioned, the feedback problem is obviously one I'd have to contend with, and I suspect that putting a speaker where the existing sound hole is could be the worst thing for feedback. then again maybe not at reasonable low levels. And I guess a paper cone speaker over the sound hole would act as a passive radiator when the amplifier was off (provided its coil were not damped by a low impedance amplifier, doubtful is the power is off).
But whatever I do, the fact remains that my best chance of success will require the best possible small speaker, so I'd still appreciate links to possible sources. Maybe if I pose my question to the right speaker company they will have some recommendations. I'm sure though if I just go to Radio Shack, i won't get any intelligent recommendations. 🙂
Thanks Eyoung! I'll check into Vi today. Never heard of them though... do you have a link?
If venting to the back might be a good idea, then its possible I suppose that I could just mount the speaker facing the back, with a hole and grill cut out on the rear. I'd then be using the revers side of the speaker as the main part of the driver, and let the back radiated sound come out the guitar's sound hole. Would that be a bad idea? On such a low scale, would the back of the speaker be all that different from the front? Of course I might have to play with the pickup and polarity to get the phasing right. Theoretically I'd have to have a whole CPU driven A/D->D/A with buffering to really get the phasing right. Hopefully one or the the other setting of s simple revers switch on the input or speaker connection will be close enough. The good news, I guess, is that this is a fairly inexpensive guitar and can be easilly replaced. So if I have to make a lot of holes before I figure out the best way to do this, I could start over with another one when I'm sure of what works best.
A driver like the VIFA TC9FD18-08 might be a good starting point. 65mm cut out, remarkably well behaved, lots of plastic, light weight, low profile etc. About US$10 ea.
thanks! Its a little big but might be workable. I'd rather have 4 ohms of course for lower voltage swing requirements, but if I go with a bridge amp, this won't be an issue. I'm a little concerned with one point about it... "High Qts indicates this driver will work in a small sealed enclosure". But what if its an unsealed enclosure. Do you think it might still behave well? Certainly cheap enough to try it!
Putting the amp and speaker inside the guitar has been done before. In fact I saw my first one about 45 years ago. They were ALL solid body guitars though. I built one about 30 years ago that barely worked and I gave up on it.
I started on another one about 3 years ago, and I think I will acheive success this time, but I don't have much time to work on it. I am looking for an electric sound with a tube amp and a fairly high volume level. Feedback WILL be the limiting factor. I have highlighted my findings here. Read through this thread. It is short.
http://www.diyaudio.com/forums/tubes-valves/200885-guitar-built-amp-speaker.html
I started on another one about 3 years ago, and I think I will acheive success this time, but I don't have much time to work on it. I am looking for an electric sound with a tube amp and a fairly high volume level. Feedback WILL be the limiting factor. I have highlighted my findings here. Read through this thread. It is short.
http://www.diyaudio.com/forums/tubes-valves/200885-guitar-built-amp-speaker.html
By the way, I found one of those at the "Madisound Speaker Store", on line at Madisound Speaker Store , and I also found several other very good candidates, including an impressive 2-1/2" 4ohm full range, that looks even more perfect for the job. Anyway, if you didn't know about Madisound, it looks like a great resource, and I can see ordering several items from them!
Originally Posted by weltersys
A full sized acoustic guitar can hit some rather surprising levels, over 100 dB at one meter is easy without really playing hard.
Smaller speakers are less efficient than larger speakers, requiring lots more power (and more battery) to achieve that level.
A speaker rated 80 dB 1watt 1 meter requires 100 watts to make 100 dB.
I'd suggest a Galaxy Audio Hot spot speaker, they are 5" nominally. The Neo magnet version (about $50) is lightweight, gets loud, sounds pretty good, and at 95 dB 1w 1m is far more efficient than any 3" driver I know of.
Art
If you don't cover the hole with a speaker, (or cover) the additional gain will cause feedback.
Placing the speaker behind the sound hole with a black cloth cover will be almost undetectable.
As a simple proof of whether the basic concept will work, I'd suggest going to a music store and trying a powered Hotspot monitor, they mount on mic stands so you can get the guitar right next to the speaker and hear what happens. Bring some gaffer's tape or a rubber jar lid to cover the sound hole, you will need it.
You will hear how loud the speaker gets without investing any money, know that a smaller speaker will likely be 10 dB less efficient, half as loud, even if you have the power to push it.
If you turn the Hot spot down to about half as loud as it can get (by ear, not volume control) you will have reduced it's 100 watts to 10 watts.
Bring a loud acoustic guitar player (or two) along to see if you can keep up.
I just checked my Ovation acoustic today, it was more like peaking at 100 dB, so the 95 dB one watt one meter Hot spot speaker could get by with a watt or two (or 5 lol) amp.
Art
A full sized acoustic guitar can hit some rather surprising levels, over 100 dB at one meter is easy without really playing hard.
Smaller speakers are less efficient than larger speakers, requiring lots more power (and more battery) to achieve that level.
A speaker rated 80 dB 1watt 1 meter requires 100 watts to make 100 dB.
I'd suggest a Galaxy Audio Hot spot speaker, they are 5" nominally. The Neo magnet version (about $50) is lightweight, gets loud, sounds pretty good, and at 95 dB 1w 1m is far more efficient than any 3" driver I know of.
Art
The sound hole/body is a Helmholtz resonator, it reinforces the low notes of the guitar.
If you don't cover the hole with a speaker, (or cover) the additional gain will cause feedback.
Placing the speaker behind the sound hole with a black cloth cover will be almost undetectable.
As a simple proof of whether the basic concept will work, I'd suggest going to a music store and trying a powered Hotspot monitor, they mount on mic stands so you can get the guitar right next to the speaker and hear what happens. Bring some gaffer's tape or a rubber jar lid to cover the sound hole, you will need it.
You will hear how loud the speaker gets without investing any money, know that a smaller speaker will likely be 10 dB less efficient, half as loud, even if you have the power to push it.
If you turn the Hot spot down to about half as loud as it can get (by ear, not volume control) you will have reduced it's 100 watts to 10 watts.
Bring a loud acoustic guitar player (or two) along to see if you can keep up.
I just checked my Ovation acoustic today, it was more like peaking at 100 dB, so the 95 dB one watt one meter Hot spot speaker could get by with a watt or two (or 5 lol) amp.
Art
Being a guitar maker, this one piqued my interest.
There isn't a whole lot of air inside that little guitar body to get excited about anything. Might I suggest that you put the driver right under the sound hole? Get one of those little perforated soundhole covers and it can look a little like a Baroque guitar.
Lute Hole Produsts - Product line - LuteHole soundhole covers, Jamulet wood pendants, and the Holey Strap leather guitar strap
Then you can treat the whole thing kind of like a solid body guitar, or speaker cabinet with strings.
There isn't a whole lot of air inside that little guitar body to get excited about anything. Might I suggest that you put the driver right under the sound hole? Get one of those little perforated soundhole covers and it can look a little like a Baroque guitar.
Lute Hole Produsts - Product line - LuteHole soundhole covers, Jamulet wood pendants, and the Holey Strap leather guitar strap
Then you can treat the whole thing kind of like a solid body guitar, or speaker cabinet with strings.
@Doug. I appreciate hearing from you! The trouble is that whatever little bit of "low end" I would get out of such an installation, it's going to be even less if any low note instantly generates acoustic feedback. Arguably I can't get away from that problem with ANY speaker actually inside the guitar. But wouldn't it be even worse with the speaker places so in the sound hole? Plus, the magnetic pickup I added already straddles the sound hole.
By the way, that company "madisound.com" I mentioned has a lot of small speaker choices, their one "technical help" person has not been very helpful. Instead of just answering my questions about some optimal choices, he basically just continued to tell me why I can't do what I want to do. I'm a DIY hobbiest and I like to TRY things, so maybe I'll get more help here! The question is this... There are three configurations I've seen used for a speaker.
1. a Sealed enclosure
2. an bass reflex enclosure with a ducted port,
3. A simple open back box, such as often used with guitar amplifiers.
I have an idea of what speaker specifications to look for in the first two cases. But my "speaker in a guitar" project is most likely going to mimic the third case. What kind of specifications (especially in the total Q factor) should I be looking for in that third case?
1. a Sealed enclosure
2. an bass reflex enclosure with a ducted port,
3. A simple open back box, such as often used with guitar amplifiers.
I have an idea of what speaker specifications to look for in the first two cases. But my "speaker in a guitar" project is most likely going to mimic the third case. What kind of specifications (especially in the total Q factor) should I be looking for in that third case?
You could try something a little different, then. A lot of contemporary guitars are being made with a tone port, basically a secondary soundhole, placed on the bass side upper bout side. This allows sound to be directed towards the payers ear and provides a much richer sound for the player, kind of like having a monitor.
You could easily place a small driver there. You could add one on the other side of the guitar, too, for added oomph. Sorry, can't help you with choosing a driver, I think that the physical size will be what determines the choice as much as anything else.
I would have thought that you might be using some other kind of pickup. The pickup will influence the sound more than anything else in your equation. Some, make that a lot, of what is out there is crap. Especially in the budget end of things.
I'd pose your question to the fine folks at some of the lutherie forums. Try
Official Luthiers Forum
http://luthiersforum.com/forum/viewforum.php?f=10101&sid=afefa5968e2ca1c35b848907106d559b
and
Musical Instrument Makers Forum
Musical Instrument Makers Forum - Welcome
You could easily place a small driver there. You could add one on the other side of the guitar, too, for added oomph. Sorry, can't help you with choosing a driver, I think that the physical size will be what determines the choice as much as anything else.
I would have thought that you might be using some other kind of pickup. The pickup will influence the sound more than anything else in your equation. Some, make that a lot, of what is out there is crap. Especially in the budget end of things.
I'd pose your question to the fine folks at some of the lutherie forums. Try
Official Luthiers Forum
http://luthiersforum.com/forum/viewforum.php?f=10101&sid=afefa5968e2ca1c35b848907106d559b
and
Musical Instrument Makers Forum
Musical Instrument Makers Forum - Welcome
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