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sympathetic strings

#21
In general, you want a preamp in between an instrument and a power amp. This will match the impedance and give the power amp enough signal to properly do its job. Without the pre, you'd get much less power and possibly other issues (but because of the unusual application, it's tough to say what exactly would happen).

The rating "2x15W 10%RMS at 4-Ohm." is incorrect. It puts out 15 watts peak, per channel, but only 3 watts average with 1% distortion. 3 watts might be enough to do what you're doing, but I'd aim for more like 10 to 20 watts (look for RMS ratings, not peak ratings).
 
#22
hmm so i guess that amp doesn't have enough juice? from what i've seen online, people are using it with considerably higher wattage, i just don't need something really loud.

so i did some heavy thinking about what my goal is with this, and my plans have changed a bit. i have a useless classical guitar that i think i could use as an acoustic amplifier. i saw guys on youtube sticking these 'sound exciters' to walls and boxes and such, and they are quite loud, so i think they would do well on an acoustic guitar. i could put one of them on either side of the bridge, maybe replace the guitar bridge with a sitar one (and figure out a way to anchor the strings), then have tuning machines running down the neck like on a sitar and go from there. so i don't know if this changes anything, other than that i'm cutting out a big part. now i suppose i want to produce some sound, so a bigger amp is what i need (?)

but yes, there's still the amp to deal with. i don't have any instrument amps lying around that i want to take apart, and i certainly don't want to buy a new bass/guitar head for this. so i guess i need something equivalent to that...
 
#23
Perhaps it would be helpful to really solidify what it is you want to end up with here. Are you looking to be able to play bass and excite sympathetic strings, or be able to play instrument or even sing into the strings?

I'm just trying to understand why you don't want to build the sympathetics directly into the bass. This would have the most natural coupling, and you would do away with the difficulties of amplification and transduction.

I'm a little confused because of all the changes in concept, etc. but the thing with the amp (if you haven't abandoned it) is that you are thinking of volume as if this is a speaker you're vibrating. It isn't. You will lose a lot of energy in trying to vibrate physical media, and especially strings. A speaker has great surface area and therefore is much more efficient than strings in vibrating air.

If you try vibrating the body of an instrument to get the strings going, you will lose much energy in the wood of the body, plus the body of instrument will vibrate at a resonant frequency. Ever play an amplified acoustic? It vibrates with feedback, even when the strings are muted, because the body itself has several resonant frequencies (which are what give acoustic instruments much of their sound).

You would do best to vibrate either the strings themselves or the bridge, I think.
 
#24
it may be misleading when i say 'amplifier.' picture taking an instrument like the sitar, and then splitting it into two parts: the playing strings, and the resonator and sympathetic strings. by vibrating the 'resonator and sympathetic string' half with the force that would generally be produced from the 'playing strings' on the bridge and top, the 'resonator and sympathetic' half should react similar to how it normally does. in other words, i'm only looking to vibrate the top of the acoustic guitar with as much force as it would normally experience when it's strings are plucked; furthermore, i'm only looking for the amount of volume that an acoustic guitar would produce from a string pluck. and if the resonator vibrates correctly, the sympathetic strings should react as if the instrument was whole.

as far as feedback, i don't see it being a problem...the resonator isn't amplified, so it can't loop on it's own signal any more than an un-amplified acoustic could...if that makes sense. what i'm worried about at the moment is how to drive the transducers, and of course cost
 
#25
When I mentioned feedback, I only meant to say that you will be vibrating the guitar top in the same way that feedback does. Although feedback with an acoustic vibrates the strings as well, the top itself will vibrate at one or more resonant pitches whenever you send a signal into it. Might be cool, like a low drone. I don't know, though; there's a lot of speculation to be done here.

Here's what I would do: try those "sound exciters". They're pretty cheap. If you have a low-power amp (they can only handle 6 watts), plug it directly into them. You don't need to hack up the amp. Any practice amp will do.

I have lots of ideas like this, and I find that trying to figure out what will be perfect beforehand

1) keeps me from ever actually doing it, and
2) it still doesn't end up perfect the first time.

So just hack it together at first, then see what's not working and fix it. I don't think anybody here besides me has done anything quite like this, and even I haven't done what you're doing with the same materials and skill set.
 
#26
Someone said you need a dulcimer. If you want to buy one maybe cheap ($150) Go to the Binghamton NY craigslist. Some guy selling one with hammers. Surely after your test you could flip it for the same price easily.

Scott
 
#27
johnson - what do u mean by a 'low-power amp?' i mean, i have a two small combo's, a 16W and something less. do u mean disconnect the lead wires to the speaker and attach them to the transducers? otherwise, if i search 'low power audio amp' online i get some results, although i'm really in the dark here as to what exactly i need.

scott - a dulcimer would be cool at some point, since i could tune it to one note scheme rather than have to re-tune for every mode i want. but i really need to work with what i have at the moment.
 
#28
uethanian said:
johnson - what do u mean by a 'low-power amp?' i mean, i have a two small combo's, a 16W and something less. do u mean disconnect the lead wires to the speaker and attach them to the transducers?.
Click to expand...

Yep, that should work fine. The specs say the sound exciter things can only handle 6 watts, so start with the volume low. The sound exciters are just speakers with the cone removed, so they can be treated just like any other speaker. By "low power" I meant you don't want to run 500 watts into these, because you'll blow them.

Do exactly as you say - disconnect the wires going to the combo speaker and attach them to your sound exciters, then attach those to your acoustic apparatus (however that shapes up). You should get something happening with that setup. Plus you'll have some tone controls (I assume your combo has at least a 3-band tone stack) which might come in handy.
 
#29
well lucky me, on my 16W combo i just found a super secret 1/4" output in the back, that bypasses the speaker when it's used. so i just gotta order the transducers and i should be able to try it (soon, waiting for $$$)
 
#31
taviswardlaw said:
place the strings in front of the cab. the sound waves will be enough to vibrate the sympathetic strings. A simple test is singing into the face of an acoustic guitar. If you have relatively good pitch and a loud enough voice you can get the strings ringing quite easily.
Click to expand...

Well, by singing into the strings, you'd just be testing the concept of sympathetic strings, which is already well-known to be real. We don't need to prove the concept of sympathetic vibration. Playing a speaker into the strings wouldn't be a very usable sound, since the sympathetics would be drowned out by the clean bass volume.
 
#32
yea my original idea was to actually attach a rack of strings to a cabinet in front of the grill...it turns out the cabinet doesn't vibrate enough to induce sympathetic vibration, and even with a resonating body the sympathetics need to be amplified

i'm a bit conflicted...i just found this online
http://goddenmusic.com/
i would love to have an acoustic guitar fitted with this. i haven't gotten a price quote yet, but i assume it's a lot more money than i have. at the same time, i would love even more to have an electric guitar with sympathetics, but it's harder to transfer sympathetic vibration with a solid body (and hard to modify an existing guitar, since you'd need to install a new pickup circuit and create some kind of one-piece bridge)...the acoustic guitar i'm looking at as an 'amp' is almost useless (a botched attempt to remove the fingerboard a while back), so making it playable again would take work. gahh there's a lot of different things i want to do...
 
#33
#34
well! i finally got my dayton sound exciters and i gotta say, these things are pretty cool. i was playing my guitar thru them and getting a lot of sound out of cardboard boxes and such. anyways i just attached both of them to the body of the acoustic guitar. aaaand it works. right now the traducers are wired in parallel to the 16W amp (which i have no clue if that's right or not in terms of power/resistance). the guitar sounds like a weird hybrid between electric and acoustic, which is what i expected...like the tone of an electric, but the resonance of the acoustic, i think thats the best way to explain it. the top is vibrating more than enough to resonate sympathetics, although things will change once there's a bridge and string pressure on it. so now i'm looking at different ways to get the tuners/strings on...i'm thinking 13 sympathetics. maybe a pic later (although not much to see, trashy guitar).
 
#35
ok well i drew up some plans today and decided on only 7 sympathetics, so each string will be used for any scale. i used 7-tone equal temperament to calculate string lengths, because (i believe) it will give me the greatest flexibility in terms of tuning up/down.

i'm going to attach a 9/16" plank of maple or some other hard wood to the neck of the guitar (which doesn't have a fingerboard at the moment). the plank will be wider than the neck, so on one side it will hang off the edge. off this edge, there will be the 7 tuning machines in a line. down the middle of the neck, each string will pass through the eye of a zither pin. it's a bit hard to explain, but it's very similar to the mohan veena:

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so i have the machines/pins coming in the mail, i got to work on leveling out the neck of the guitar (because it's all ripped up and uneven). pictures eventually.
 
#37
finally, it's coming together.


for today:
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something that represents the bridge of a sitar. not too shabby for a first try. well, except that the legs are made of popsicle sticks...

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in the end, i just took the entire neck off the guitar because it would be more work to incorporate it. so this piece of maple is going where the neck used to be. i have the tuning machines to install BUT i couldn't find my drill set :crying: but strings are in the mail, and i should be done in a few days.
 
#39
conical johnson said:
I have an early Fodera with a popsicle stick bridge, so no biggie. Nice mid hump.

How many playable strings are you going to have?
Click to expand...

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well none of these strings are playable, i'm using the guitar as a resonator. so there are 7 sympathetics with a very wide tuning range. i'd be using this with my fretless guitar, so...technically i have 6 playable strings :D
 

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