Amplifying a nylon string guitar - best options

[Mark McLean]

I am building a neo-classical nylon string guitar. New territory for me, but it seems to be going well so far. I am generally following the Gore/Gillet method and using falcate bracing (my first try of this), and no bridge plate (is that a mistake?) .
I have already closed the box and I am now considering adding a pickup to this instrument (another first in my experience). People here seem pretty keen on the K&K pure mini, and from what I understand they are OK for nylon strings. So, a few questions for those with experience in this relm:
1. Is it OK to use the type of transducers that normally superglue to a bridge plate, and attach them directly to the underside of the soundboard?
2. If so, any special considerations for placement relative to the falcate braces under the bridge (which sit pretty much exactly where K&K say the transducers should be placed).
3. Alternatively, is an undersaddle piezo a better choice?
4. Any other words of advice?

Cheers
Mark

[kiwigeo]

Mark,

One of my current builds is a falcate braced classical (currently being french polished) without a bridge plate and it'll have a K and K western classical pickup system. There are 4 piezeo pads. Ive test fitted the pads and they just fit.....two between the two primary braces and the remaining two squeeze in between the primary and secondary braces. Ill be making up my own template to use for securing the pads rather than the method in the K and K instructions.

I don't know if anyone has fitted a 3 pad steel string system to a classical but I think the falcate bracing would create issues.....4 pads would be the way to go.

The easiest way to fit the pads is to do it while the box is open but you need to design your bridge gluing caul with recesses that clear the pads so you don't crush them during glue up. Ive opted to fit my pads after the bridge goes on....more of a juggle but shouldn't be too many issues.

Here's a pic of my bridge caul with the K and K classical pads laid out. The important thing is to ensure there's enough space between the two primary braces to fit two of the pads.

[blackalex1952]

My opinion for what it's worth. From a guitar player's perspective.Piezo pickups "quack". I have never heard one that doesn't to some degree or other. Position is so important, and it is worth while experimenting if one is going to use them. People seem to love the K&K- I have one in a Gypsy Jazz guitar and it sounds terrible.The acoustic guitar functions as a whole instrument, a contact pickup of any kind will emphasise the soundboard energy at its point of attachment. The combination of pickup, amplifier, EQ, pre amp etc needs to be considered as a whole system. IMHO the BEST way to amplify an acoustic guitar is with a tastefully positioned condensor microphone. The drawback is feedback at high levels. For stage use, a small diaphragm condensor is better, the large diaphragm ones are more prone to low frequency feedback. The advantage, apart from tone and texture, is the players ability to make use of both the proximity effect of cardioid microphones and the volume control that can be utilised by moving the instrument closer to and further away from the mic. Dynamic microphones have their place as well, but it is worth noting that dynamic mics, by their construction, have physically heavier diaphragms and are therefore slower to respond to transients. High end acoustic guitars are made with light, fast responding soundboards...match the mic to the guitar! The air resonance of a guitar is aroung 90Hz...so use the bass roll off on the amplifier, or on the mic itself if it has one. The microphone polar pattern and distance from the guitar influence how much of the guitar's sound output is being picked up, along with which part of the guitar the mic is pointing to.Avoid aiming the mic directly into the sound hole.
Steel string players usually play at higher volumes and the piezo and magnetic pickups have a strong role to play there. Amplified stage guitars are designed with stiff soundboards so as to minimise low frequency feedback.
Piezos have their place with nylon and acoustic steel string guitars, but I prefer to use a mic or a combination of the two. I have never had great results with an internal microphone/piezo combination that are as good as with an external mic, or ext mic/piezo combination.

[kiwigeo]

My experience has been that the K and K pad system is far less quacky than most under saddle piezeo systems.

[Trevor Gore]

1. Is it OK to use the type of transducers that normally superglue to a bridge plate, and attach them directly to the underside of the soundboard?
2. If so, any special considerations for placement relative to the falcate braces under the bridge (which sit pretty much exactly where K&K say the transducers should be placed).
3. Alternatively, is an undersaddle piezo a better choice?
4. Any other words of advice?

1) Yes
2) You only need 3 transducers. The K&K Pure Classic has 4, because most classical guitars (fan braced) have a brace on the centreline, so 4 are required for symmetry. You should be able to position 3 directly under the saddle. Check this out.
3) No
4) Piezo pick-ups generally need to run into a high impedance amp/pre-amp, at least 1Mohm. K&Ks have a very high output and if run into a typical 10Mohm pre will have way too much bass if you have a responsive guitar. K&Ks will drive into 15kOhm quite happily, and, depending on the responsiveness of your guitar, you'll get much more realistic sound running into a lower input impedance. If you have the electronics chops, it's best to experiment a bit.

[kiwigeo]

A tip via Robbie Obrien (I think)....ditch the gel CA glue that comes with the K and K kit and buy some fresh stuff to stick the pads on with.

[Trevor Gore]

Whilst I've never had any problems with the gel that K&K supply, the last few K&K sets that I've had didn't have any gel included. So it's a case of supply your own, anyway, these days.

[Allen]

K&K stopped supplying super glue as they were having batches getting old sitting on the shelf waiting for the units to sell.

Where you position them makes a huge difference in their response. On my ukes and guitars its certainly not directly on the bridge patch.

And running them through a good preamp is a must if you want the most natural sound.

[Mark McLean]

OK, thank you gentlemen. That is exactly the sort of information that I was after. I feel confident that I can manage the job of installing a K&K.
I will measure out the space between my braces to check the room for the transducers. Does anyone happen to have one handy to measure the width of the transducer heads?

On looking at the K&K website again I see that the Pure Mini has 3 transducers, but they say that it is for steel strings. The Pure Classic is suggested for nylon strings and it has 4 heads. Does anyone know if the transducers are different? Or does the Classic just have 4 because, like Trevor said, many classicals have a brace on the centre line so they need an even number?

If they are otherwise exactly the same I would be better using the Mini. If the Classic is somehow configured to be better for nylon strings I should go with that , but maybe only place 3 heads. Trevor, what do you do with the fourth one - how do you remove it from the device?
cheers
Mark

[Bob Connor]

Hi Mark

As Trevor mentioned the pre-amp is critical so I'd be ordering a Pure-Mini pre-amp from K&K which does have the appropriate input impedance.

You wouldn't bother using the K&K's without one.

Regards

[kiwigeo]

OK, thank you gentlemen. That is exactly the sort of information that I was after. I feel confident that I can manage the job of installing a K&K.
I will measure out the space between my braces to check the room for the transducers. Does anyone happen to have one handy to measure the width of the transducer heads?

On looking at the K&K website again I see that the Pure Mini has 3 transducers, but they say that it is for steel strings. The Pure Classic is suggested for nylon strings and it has 4 heads. Does anyone know if the transducers are different? Or does the Classic just have 4 because, like Trevor said, many classicals have a brace on the centre line so they need an even number?

If they are otherwise exactly the same I would be better using the Mini. If the Classic is somehow configured to be better for nylon strings I should go with that , but maybe only place 3 heads. Trevor, what do you do with the fourth one - how do you remove it from the device?
cheers
Mark

Mark

1. Hard to tell from the outside but transducers look the same physically for both classical and steel string kits.
2. Diameter of transducers on both kits is around 12.5mm
3. My understanding is there are 4 pads on the classical kit to get sufficient saddle coverage due to central fan brace. ie the extra pad is purely to allow for the central fan brace.
4. You shouldn't need to cut off a pad from the classical kit.....4 pads will fit a falcate braced classical as per my photo above. The pads are wired direct to the output jack on both kits.....parallel wired. I assume there'd be a slight difference in total impedance. Professor Trevor can enlighten us on this one.

[Mark McLean]

Thanks Martin & Bob
I will follow Martin's plan of having 2 transducers in the centre, and will also get the pre-amp.
Cheers
mm