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  #1  
Old 11-25-2020, 01:51 AM
ballynally ballynally is offline
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Default Archtop K&K pure twin spot vs definity?

Hi,
I have a Pure twin spot on the inside of my F style mandolin and i am contemplating getting one for my acoustic archtop guitar.
I have some Pure ones on other flattops and i really like them but you have to work a little harder compared to piezo and magnetic pickups.
K&K is now recommending the Definity pickup, between the leg of the bridge and the top of the guitar. It seems a more direct approach than the Pure under the top.
A good medium between piezo and the Pure, perhaps?

Q: it's only one single pickup and most seem to place it under the bass side of the floating bridge. It seems a tad bassy in most soundclips but the only other option is the treble side.
With the Pure you can find the sweet spot in various places.
Has anyone compared the two systems?
Im also concerned about putting anything between a leg of a floating bridge and the top in terms of affecting the acoustic tone as the only contacts are the two legs..

Please don't recommend a mic or a magnetic option. I already know what they do..:-)

Last edited by ballynally; 11-25-2020 at 01:56 AM.
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Old 11-25-2020, 02:12 AM
Mandobart Mandobart is offline
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I've used twin piezo SBT pickups on multiple floating bridge, archtop instruments including my Eastman archtop.

I mount the heads under the sounboard, one right below each bridge foot (or beneath each end of the bridge for continuous contact bridges.

Works well.
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Old 11-25-2020, 03:02 AM
shufflebeat shufflebeat is offline
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After as much internet searching as I could manage I fitted a Twin Spot to my Framus archtop a couple of years ago. Previously I had used a piezo UST (possibly Martin Thinline) and a Headway endpin preamp but never really worked out where to put the 9v battery.

I tried a few temp fittings (under the bridge, inside and out, within the bridge, various parts of the soundboard) which were very disappointing. The sound was woolly and indistinct with lots of discordant low mid resonances. If I left them in they sounded horrible and fed back, if I notched them out there was nothing left of the sound.

Eventually I found an article suggesting the elements should go outside the feet of the bridge and inside the guitar. This was a winner both for sound and ease of fitting, however, the nastiness of the low mid was not completely cured.

Having finally decided this was the best the K&K could do I compared it to the UST, no competition. I could EQ the nasty out of the UST and be left with a useable sound or so could EQ the nasty out of the K&K and be left with very little.

Then I discovered Impulse Response technology. My Tonedexter was the first real step up to something useful but the real game changer has been my experiments with the IR production algorithm developed by JonFields and Cuki of this parish. The Framus/UST has been the project which has shown the most benefit from this approach and when circumstances permit I will be using a selection of the IRs created by myself in a my Mooer Radar pedal in the FX loop of the TD which will be dealing with my other instruments.

I still love the K&K sound in smaller bodied instruments (mandola/bouzouki) but in my Dreadnought it's not useable on loud stages and in the archtop it's not useable at all.
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Old 11-26-2020, 01:47 PM
ballynally ballynally is offline
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Quote:
Originally Posted by shufflebeat View Post
After as much internet searching as I could manage I fitted a Twin Spot to my Framus archtop a couple of years ago. Previously I had used a piezo UST (possibly Martin Thinline) and a Headway endpin preamp but never really worked out where to put the 9v battery.

I tried a few temp fittings (under the bridge, inside and out, within the bridge, various parts of the soundboard) which were very disappointing. The sound was woolly and indistinct with lots of discordant low mid resonances. If I left them in they sounded horrible and fed back, if I notched them out there was nothing left of the sound.

Eventually I found an article suggesting the elements should go outside the feet of the bridge and inside the guitar. This was a winner both for sound and ease of fitting, however, the nastiness of the low mid was not completely cured.

Having finally decided this was the best the K&K could do I compared it to the UST, no competition. I could EQ the nasty out of the UST and be left with a useable sound or so could EQ the nasty out of the K&K and be left with very little.

Then I discovered Impulse Response technology. My Tonedexter was the first real step up to something useful but the real game changer has been my experiments with the IR production algorithm developed by JonFields and Cuki of this parish. The Framus/UST has been the project which has shown the most benefit from this approach and when circumstances permit I will be using a selection of the IRs created by myself in a my Mooer Radar pedal in the FX loop of the TD which will be dealing with my other instruments.

I still love the K&K sound in smaller bodied instruments (mandola/bouzouki) but in my Dreadnought it's not useable on loud stages and in the archtop it's not useable at all.
Thanks for your considered response. Apart from my mandolin i also have a K%K pure mini in my 1930s Kalamazoo flattop and my 00028vs.
Both small bodies and the system works well but both are set up with a parametric EQ to filter out some low mids. I prefer that sound to most USTs except for my LR Baggs in my jumbo.
I think the K&K pure might need a solid top, perhaps not laminated.
Archtops might be more hit and miss than flattops using that system.
My guess is that a combi of UST and K&k style would work best.
None of the mic options work imo, for obvious reasons.
I have tried a Fishman UST piezo in my F style mandolin but that was pretty bad. My other flattop mandolin has a K&k pure. Again, pretty good, so i am leaning towards an under soundboard system, though i am still curious about the Definity compared to that.
Imo, every system other than straight ust needs a parametric EQ.
Just because of the many overtones the direct contact with the vibrating top produces.
With a mic, especially inside a guitar you are swimming in a whole ocean of unwanted frequencies that you cannot dial out and no guitar sounds good inside. A mic outside gives serious feedback issues and can only be used with the help of a PA guy and a controlled space w strategic monitors at least a metre away from the player..
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Old 11-26-2020, 02:22 PM
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James May James May is offline
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Quote:
Originally Posted by ballynally View Post
...
I think the K&K pure might need a solid top, perhaps not laminated.
Archtops might be more hit and miss than flattops using that system.
My guess...
From what I know first hand, if you're willing to go in and glue or tape the sensors to the inside close to or under the bridge feet, soundboard transducers like the K&K or my Ultra Tonic will work with archtops just fine. They don't need a solid top. However, the more response (ie.e flexible) the top is, the more you'll get out of them. And of course, all but the Ultra Tonic will present feedback and low end mud issues.

In general, based on my experiments, archtops with SBTs will give a brighter sound than flat top steel string installations will.

There is this more on my experiments here:
https://www.acousticguitarforum.com/...d.php?t=593356
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Old 11-26-2020, 03:12 PM
ballynally ballynally is offline
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Originally Posted by James May View Post
From what I know first hand, if you're willing to go in and glue or tape the sensors to the inside close to or under the bridge feet, soundboard transducers like the K&K or my Ultra Tonic will work with archtops just fine. They don't need a solid top. However, the more response (ie.e flexible) the top is, the more you'll get out of them. And of course, all but the Ultra Tonic will present feedback and low end mud issues.

In general, based on my experiments, archtops with SBTs will give a brighter sound than flat top steel string installations will.

There is this more on my experiments here:
https://www.acousticguitarforum.com/...d.php?t=593356

Thank you, James. I am not so much concerned with feedback but i AM interested in exactly how you achieve less of the low end issues compared to the K&K SBT. Afaik the pickup is passive.
I imagine some EQ-ing through resistors/capacitors but think it needs at least a small power source to achieve that, like a preamp..

And what you said about SBTs having a brighter sound in archtops makes sense. My mandolin w a Pure has got quite a toppy end, and yes, the high E seems weaker as well.

Last edited by ballynally; 11-26-2020 at 03:22 PM.
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Old 11-26-2020, 05:22 PM
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Originally Posted by ballynally View Post
Thank you, James. I am not so much concerned with feedback but i AM interested in exactly how you achieve less of the low end issues compared to the K&K SBT. Afaik the pickup is passive.
I imagine some EQ-ing through resistors/capacitors but think it needs at least a small power source to achieve that, like a preamp..

And what you said about SBTs having a brighter sound in archtops makes sense. My mandolin w a Pure has got quite a toppy end, and yes, the high E seems weaker as well.
I'll try to explain. It's not an EQ, and it is not dependent on having the resonances at any particular frequencies. And yes, it is passive.

Think of the low end resonances of your instrument as big peaks in the natural acoustic response. The lowest one is caused by the chamber forming an helmholtz resonator at somewhere around low G to A. The second one is the first mode of the top plate, and usually occurs roughly around 180Hz or so. Both of these will cause feedback problems because the response of a SBT at these frequencies will mirror the acoustic response and be something like 8-14db louder than everything else.

Besides causing feedback concerns, they are the reason most SBTs sound muddy on the bottom. The Q of these resonances is not particularly narrow. What this means in layman's terms is that any note you sound will cause them to respond to some degree. This also goes for the pick attack, and any other percussive components to the string excitation.

So back to your question. The Ultra Tonic gets rid of most of this unwanted response in the electrical output by playing a bit of a science trick:
  • The main sensor(s) located under the saddle up the desirable string induced response as well as the undesirable resonance response.
  • A feedback suppression sensor is located much further from the saddle location, and picks up mostly the undesirable resonance response. It has opposite polarity to the main sensor.
  • A passive mixing circuit functions as a 12 position stepped attenuator that let's you mix in just the right amount of the feedback cancellation sensor so that the bad stuff cancels out, thus eliminating the hyped resonance response (mud), and greatly improveing feedback immunity. Somewhat analogous to a humbucker or a noise cancelling headset.

I hope that makes it clearer.
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Old 11-27-2020, 02:38 AM
ballynally ballynally is offline
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Quote:
Originally Posted by James May View Post
I'll try to explain. It's not an EQ, and it is not dependent on having the resonances at any particular frequencies. And yes, it is passive.

Think of the low end resonances of your instrument as big peaks in the natural acoustic response. The lowest one is caused by the chamber forming an helmholtz resonator at somewhere around low G to A. The second one is the first mode of the top plate, and usually occurs roughly around 180Hz or so. Both of these will cause feedback problems because the response of a SBT at these frequencies will mirror the acoustic response and be something like 8-14db louder than everything else.

Besides causing feedback concerns, they are the reason most SBTs sound muddy on the bottom. The Q of these resonances is not particularly narrow. What this means in layman's terms is that any note you sound will cause them to respond to some degree. This also goes for the pick attack, and any other percussive components to the string excitation.

So back to your question. The Ultra Tonic gets rid of most of this unwanted response in the electrical output by playing a bit of a science trick:
  • The main sensor(s) located under the saddle up the desirable string induced response as well as the undesirable resonance response.
  • A feedback suppression sensor is located much further from the saddle location, and picks up mostly the undesirable resonance response. It has opposite polarity to the main sensor.
  • A passive mixing circuit functions as a 12 position stepped attenuator that let's you mix in just the right amount of the feedback cancellation sensor so that the bad stuff cancels out, thus eliminating the hyped resonance response (mud), and greatly improveing feedback immunity. Somewhat analogous to a humbucker or a noise cancelling headset.

I hope that makes it clearer.
it does make it clearer, James. Thanks for that.
I thought one needed magnets for reversed polarity but i guess a phase flip does it equally good.
Yours seems quite a brilliant idea.
And yes, most of the trouble frequencies lie around 160 Hz. In fact, that also goes goes for electric guitars through amps and speakers, where the speaker acts as a 'box' with often an 80Hz frequency peak (2x80Hz is 160Hz). As the acoustic guitar signal is also amplified and put out through a speaker the same issue arises.There is some feedback occuring around 100Hz as you mentioned on your site.
Both those frequencies i currently pull down through my para EQ w the K&K Pure.
The archtop im looking to buy soon has a floating humbucker.
Your combi system looks promising for that.
You are based in the US.
Any dealers in the EU?
I suppose it's small enough to post fr US to EU without having to pay import duty?

Last edited by ballynally; 11-27-2020 at 02:46 AM.
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  #9  
Old 11-27-2020, 04:18 AM
shufflebeat shufflebeat is offline
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Originally Posted by ballynally View Post
I suppose it's small enough to post fr US to EU without having to pay import duty?
Sadly not in my experience.

Remember this.

An acoustic instrument without a soundboard/resonating chamber is just the sound of the saddle vibrating. All other character of the sound is the addition of the response of the chamber to the vibration of the saddle. If you were to mic up the sound of the saddle on it's own it would sound awful.

Now take that same "saddle only" sound which is what you're getting from the UST. Run that through an impulse response (IR) and each sample "triggers" the IR in such a way as to have the effect of a resonating chanber (not quite how it works but not too far off).

In this way you're not subtracting frequencies with an EQ or desparately trying to boost something that's not there, you're adding a layer (the sound of a resonating chamber, preferably your own guitar) to the total, then sculpting the outcome.

Strongly recommend you explore. If you already have a computer recording setup it's easy and free, happy to provide guidance.

I would, however, not try to talk anyone out of investing money on any of James May's contributions to the craft, for which I'm hugely grateful.
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Old 11-27-2020, 09:18 AM
ballynally ballynally is offline
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Originally Posted by shufflebeat View Post
Sadly not in my experience.

Remember this.

An acoustic instrument without a soundboard/resonating chamber is just the sound of the saddle vibrating. All other character of the sound is the addition of the response of the chamber to the vibration of the saddle. If you were to mic up the sound of the saddle on it's own it would sound awful.

Now take that same "saddle only" sound which is what you're getting from the UST. Run that through an impulse response (IR) and each sample "triggers" the IR in such a way as to have the effect of a resonating chanber (not quite how it works but not too far off).

In this way you're not subtracting frequencies with an EQ or desparately trying to boost something that's not there, you're adding a layer (the sound of a resonating chamber, preferably your own guitar) to the total, then sculpting the outcome.

Strongly recommend you explore. If you already have a computer recording setup it's easy and free, happy to provide guidance.

I would, however, not try to talk anyone out of investing money on any of James May's contributions to the craft, for which I'm hugely grateful.

thank you. I will look into it..
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