old national cones

[marc cottonfield]

Hello guys,
this forum is a living, collective, constantly updated encyclopedia about resonator instruments and playing technics... so thank you Michael for having started it!
I was wondering about old National cones, if there are different sounding qualities among them depending on the period they were made: early without spirals, 1930/'35 with spirals, late cones with radial embossing added. This argument has been in my opinion not discussed enough yet, and many members here are very qualified to add anothere little piece to this mosaic.
Michael, do you really think that old cones sound better without any cleaning ? ( yes... this has been recently discussed here! ). I tend to agree, though not on a "scientific" basis, but more for a somewhat romantic idea.

thank you
mc

[tark]

Hi Marc,

I'm not sure anyone today could ever really say for sure what National guitars and cones sounded like when they were new. Also the recordings made at the time aren't acoustically accurate by todays standards. Even an un-played mint National guitar has possibly been subject to ageing processes that might change the sound and in any case you might argue that a genuine un-played NOS instrument should be played in to develop its true sound.
I think Michaels comments about not cleaning the dirt off old cones had more to do with his feeling that vintage instruments should be in their current condition and not cleaned up and fixed by a dealer, although personally if I was buying a guitar to play I'd like it restored to the best possible condition by an expert.
A good fifty years coating of grime I would think would have quite an effect on tone by damping down the treble. It's hard to say how many old Nationals have their original cones since they were certainly designed to have new cones fitted quite easily and National did sell replacement cones. I'd guess they probably expected the odd cone crush due to over enthusiastic playing.
Unfortunately my experience has been limited only to new cones and I have never seen or played an old National. I believe the spirals were added quite early on. As I understand it from Bob Brozmans book the Dopyeras were spinning at thicknesses not normally attempted at the time and some in the metal spinning trade didn't even think it possible. The spirals stiffen and strengthen the cone, making it possible to have a thinner, lighter cone, but still with sufficient strength to withstand the string pressure. The radial impressions seem to be a later experiment that stiffens the flexible surround of the cone, making it quieter. These may have been added to try and minimise cone collapse, but they seem to have been a failed modification that didn't last for too long. Today, National Resophonic cones are generally half the weight of cones made by others.
Brand new cones do play in and develop their tone over several days and sometimes the tone seems to improve over even longer periods. It's hard to say what changes may occur in an Aluminium cone over many years, although I have read that some old cones become brittle and crack or split.

[Michael Messer]

Hi Marc,

Thanks for the kind words about our forum. I like your description of it being like an encyclopaedia!

Your question is an interesting one and one that requires a detailed answer. I will return to this thread later in the week when I have a spare half hour to answer properly.

There are differences in the cones from different periods, but it is quite difficult to actually define what those diffeences are. I have heard all types of cones sounding wonderful and totally the opposite! Spinning cones is a real black art and to my knowledge there are only two or three people in the world now can do it as well as those guys at National in the 1920s.

Tark is correct about my comments on cleaning old cones. They definitely sound better when they are clean. But my point was about dealers opening up vintage Nationals and working on them before selling them. I agree with you that it would be better to buy a playable 1929 guitar than an unplayable one, but who is to say the dealer knows what they're doing. That was my point.

Tark, it is usually possible to see whether the cone is original or factory replaced, but only if replacement cones were used.

Shine On,
Michael.

[1928triolian]

Hi everybody,

very interesting thread, and both tark's and MM's replies are very useful ( also, MM told he will post again about this, I look forward to read it...).

I can say that tark is totally right about the swirless early cones: they are thicker and heavier ( anyway they aren't smooth, having slightly embossed concentric circles ), and this should have in my opinion some influence on the sounding side, making them maybe a little less resonant and sustaining than spiral ones.

I have both cones, but the swirless one is out of the guitar for repairs ( of the guitar) now, I played a little this guitar and gave it to the repair person, but the sound was wonderful anyway; I will be more precise when I have the guitar back.

[tark]

Hi 1928,

Err.. I think there's a slight misunderstanding here. I was talking about the cones that have the additional short radial impressions around the outer rim as well as having the spiral impressions. Both of these will stiffen the cone - the spirals will stiffen the main cone and the radial embossing will stiffen the suspension rim. My guess was that the radials siffening the suspension rim would make the cone slightly less responsive and therefore quieter. According to Mr Brozman this is not the case and he says there is no audible difference between cones with or without radials.

I wasn't refering to any very early cones that had neither spirals or radial embossing.
Anyway I'm going to post yet another thread in reply to some earlier discussion about if there had been any recent changes in the way NRP make their cones. I'm mentioning it here because it has some relevance.

Oops!! sorry 1928, I skim read your "I 'can' say.." as a can't. Then got further confused because you mentioned the earlier cones which I hadn't known about. Yes you're absolutely right, the principle is - lighter cones (and bridges) are more responsive. I have done some experiments with very heavy metal bridges where the bridge had so much inertia that the notes could sustain forever with just a little 'bowing' action from a slide. The down side was that you could hardly hear the notes!!

[1928triolian]

Hi tark,

no misunderstanding, in my opinion.
You wrote: "the spirals stiffen and strenghten the cone, making it possible to have a thinner, lighter cone", and I was noticeing that my early cone without spirals is actually less thin and less light than the cones with the spirals and spirals/radial embossing.

My thought was that the lighter the cone, more resonant the overall sound.

[marc cottonfield]

Hello guys,

thank you for the informative responses, and very interesting the parallel thread about new NRP hot rod cones ! Could they be an attempt of NRP to get closer to that old sound ?
As for the old sound ... Michael, we were looking forward your detailed reply ! ;D

[tark]

To expand on my previous comments on lighter cones etc.

I came across this explanation which made a lot sense to me based around the idea of impedance. Electrical impedance is a very familiar concept to anyone who has an electronics background, but it can also be applied to acoustic or mechanical systems as acoustic impedance or mechanical impedance.

It probably helps to think of acoustic and mechanical impedance as 'resistance to motion'. Although its more accurate to say 'the resistance to motion at a particular vibrating frequency'.

Anyway the idea is that guitar strings have a certain resistance to motion (a string impedance) and the bridge and soundboard/cones of a guitar also have their own impedance. Its useful to think of the relationship between the string impedance and the impedance of bridge/soundboard.

Assume that the string impedance is a given (it varies depending on string gauge, tension, length and vibrating frequency).
If you have a guitar design where the bridge/soundboard has a relatively high impedance (heavy bridge with a stiff heavy soundboard) compared to the strings then you will have a guitar that sustains well but isn't very loud. Due to the way that the bridge/soundboard behaves the impedance is also likely to be higher at lower frequencies so the guitar will have a poor bass repsonse.

As you lower the bridge/soundboard impedance (lighter and thinner) then the sustain falls but the volume and bass response improves.

This is clear from instruments like the banjo or the violin which have light floppy bridges and thin light soundboards. They are very loud but have little sustain. They also don't have a lot of bass but that is for other reasons to do with their resonant cavities.

In the case of the resonator guitar the weight of the bridge and the stiffness and weight of the cones are balanced against the lever action of the bridge, which helps to amplify the sound. In any case tricone resonators like the cheap Chinese versions have very heavy bridges and stiff heavy cones. These guitars have little volume or bass, but sustain well particularly on the high notes.

National Reso-Phonics with their properly hollowed out bridges (on the tricones) and lightweight flexible cones are loud with a good bass response. I have seen a post on another forum which said that the author chose a Continental guitar (i.e. relatively heavier, stiffer cones) over an NRP because it had a sweeter longer sustain on the high notes.

I would think that old cones are likely to get brittle and stiffer with age, so older National guitars with very old cones are likely to have a little more sustain and maybe less volume and bass.

This all makes a lot of sense to me, the rest of you probably think I've lost the plot!!

[rickS]

Tark, you need to get out more..

[fitchmeister]

Hey Tark - nice post

Isn't it the idea that your bridge has higher impedance so it transfers more of the energy to where you want it i.e. the cones/soundboard. The reason i ask is i have a replaced an cheap bridge with an NRP one - it's actually heavier than the cheap one but, i suspect alot stiffer, resulting in better tone.

Resound sell a replacement 'high density' T piece too.

Cheers

Roj

[tark]

Hi RickS,

You're right I definitely need to get out more.

Hi Roj,

In general it is true that the bridge/soundboard have a considerably higher impedance than the strings. After all you can deflect the strings easily with your fingers but getting any detectable movement out of the bridge/soundboard or bridge/cones using finger pressure is very hard.

However, according to impedance theory maximum energy is transfered from the strings to the bridge/cones when their impedances are equal.

Normally fitting a heavier, stiffer bridge to a tricone will raise the impedance seen by the strings, so in theory the sustain should increase slightly, the treble may be boosted a little and volume should drop slightly.

My experiments show that if you vary the weight of the bridge a lot then its effects become very obvious. But the weight of the T bridges on the market varies at most between 48 and 72 grams. The weight change between your old bridge and the NRP (NRP tricone bridges weigh 59gms) is likely to have been less. I doubt that there would be any significant change in stiffness. As far as I can tell the stiffness and weight of the cones has a bigger effect than changes in the bridge. In general NRP cones are half the weight of most Korean, Chinese and Quarterman cones (for tricones).