Phase Locking of Drone Reeds in Hollow Mainstocks

[geoff wooff]

Do free reeds do phase lock?

Perhaps Cheap reeds will lock( (shut) but Free reeds should be forgiven their foibles....

I think someone has done a study on free reed Phase locking and it is one of the reasons why Vibrato (Musette) tuning on accordions is usually set at a minimum 1 hertz spacing of two reed pitches.

More to this subject; what about the effect on sound of a double chanter ( two bores ,two reeds but one reed chamber? I think the tone produced from a double chanter is the way it is because the reeds will not phase lock. Perhaps each note would need to be played for longer periods to allow two double reeds to syncronize.

[rorybbellows]

More like,; " who was the first person to make a solid stock and why did they do that ?"

Thanks Geoff I never knew hollow stocks were first. As to why they were made could it be that they are just easier to make ,as stated earlier or do you think the solid stock offers a different sound that some pipers may prefer. Solid stocks are better at transmitting vibrations to the bag which of course is a very effective resonator. The Ennis coyne is a good example of the solid stock sound. So is it a case of horses for courses.


RORY

[Hans-Joerg]

I find it much easier to make a hollow stock: I buy veneer-wood - 3 layers a stock - glue between - and "roll my own" on a slightly conical metal "dowell" (to losen it after drying you put it in the fridge) (thick walled aluminum pipe-piece - 5.5 cm o. d. - in my case).

[geoff wooff]

More like,; " who was the first person to make a solid stock and why did they do that ?"

Thanks Geoff I never knew hollow stocks were first. As to why they were made could it be that they are just easier to make ,as stated earlier or do you think the solid stock offers a different sound that some pipers may prefer. Solid stocks are better at transmitting vibrations to the bag which of course is a very effective resonator. The Ennis coyne is a good example of the solid stock sound. So is it a case of horses for courses.


RORY

Rory, I am not sure I would go as far as to say the solid stock is easier to make but perhaps it depends what tools the maker has at his/her disposal . Also the materials used can have a marked effect on sound and choice of type. Where do you get your suggestion that Solid stocks transmit vibrations to the bag ? I cannot see why that would happen any more in a Solid stock than a Hollow type, but again much to do with all the materials used would need to be taken into consideration.

The Ennis Coyne set; is said to have a Solid stock although it has the sound atributes associated with the Hollow type, but I have not personally examined that instrument and again the caveat " it depends a lot on the materials involved" as to the sound outcome.

It is probably 37 years since I made a Solid mainstock.....

[Mr.Gumby]

I am not sure I would go as far as to say the solid stock is easier to make but perhaps it depends what tools the maker has at his/her disposal

[rorybbellows]

I am not sure I would go as far as to say the solid stock is easier to make but perhaps it depends what tools the maker has at his/her disposal . Also the materials used can have a marked effect on sound and choice of type. Where do you get your suggestion that Solid stocks transmit vibrations to the bag ? I cannot see why that would happen any more in a Solid stock than a Hollow type, but again much to do with all the materials used would need to be taken into consideration.

The Ennis Coyne set; is said to have a Solid stock although it has the sound atributes associated with the Hollow type, but I have not personally examined that instrument and again the caveat " it depends a lot on the materials involved" as to the sound outcome.

To be honest ,Geoff most of my information comes via this forum, in past threads it came up indirectly from Andrae Rogge that the Ennis coyne has a solid stock .
The idea of a solid stock transmitting vibrations better is due to the fact that a solid stock is heavier (materials being the same)than a hollow one. It seems at the end of the day ,there is so much conjecture ,guesswork and personal preference involved that unless objective scientific tests were done under laboratory conditions , certain questions will never be answered conclusively

RORY

[geoff wooff]

I am not sure I would go as far as to say the solid stock is easier to make but perhaps it depends what tools the maker has at his/her disposal

Ah... turning the counterbore step for the back plug of an Ebony hollow stock... no face mask!... amazing I'm not also smoking as I work!!

[geoff wooff]

I am not sure I would go as far as to say the solid stock is easier to make but perhaps it depends what tools the maker has at his/her disposal . Also the materials used can have a marked effect on sound and choice of type. Where do you get your suggestion that Solid stocks transmit vibrations to the bag ? I cannot see why that would happen any more in a Solid stock than a Hollow type, but again much to do with all the materials used would need to be taken into consideration.

The Ennis Coyne set; is said to have a Solid stock although it has the sound atributes associated with the Hollow type, but I have not personally examined that instrument and again the caveat " it depends a lot on the materials involved" as to the sound outcome.

To be honest ,Geoff most of my information comes via this forum, in past threads it came up indirectly from Andrae Rogge that the Ennis coyne has a solid stock .
The idea of a solid stock transmitting vibrations better is due to the fact that a solid stock is heavier (materials being the same)than a hollow one. It seems at the end of the day ,there is so much conjecture ,guesswork and personal preference involved that unless objective scientific tests were done under laboratory conditions , certain questions will never be answered conclusively

RORY

Thankyou for your usual very honest answer Rory. Perhaps we should agree that there is a little too much 'received wisdom'... also a certain degree of 'miss information' on forums and the Internet in general ? That we should only trust what we know, or believe to be true might be the fairest way to conduct ourselves?

[Mr.Gumby]

amazing I'm not also smoking as I work!!

You wouldn't, would you? Well, on the other hand, maybe..

[chaos97]

I'd like to ask, because I'm still not sure I understand- Regarding the original thread that sparked this one; How does the insertion of the ring on the end of the stock help phase locking in solid stocks? Is the idea that the vibrations echo off it back into the cylinders containing the reeds, helping to create a shared vibrating space? I've never heard of this. Does anybody else have experience with this technique?

And on a side note; I've also read that Ennis had a solid stock. The original was either missing or severely damaged and a new one was made - possibly by J Brogan(?).

[rorybbellows]

How does the insertion of the ring on the end of the stock help phase locking in solid stocks?

I think there is a tendency to confuse aerodynamics with sound wave dynamics, Having everything rounded off and smooth is not necessarily the answer.

RORY

[daveboling]

How does the insertion of the ring on the end of the stock help phase locking in solid stocks?

I think there is a tendency to confuse aerodynamics with sound wave dynamics, Having everything rounded off and smooth is not necessarily the answer.

RORY

But there is a relationship in that pressure waves (sound) do not propagate smoothly around sharp edges in a similar way that a sharp edge moving through a fluid (air in this case) will produce eddies. These eddies contribute to white/pink noise (Geoff mentions in the NPU "Heart of the Instrument" DVD that he prefers to eliminate sharp edges/burrs from staples to avoid added noise). A good bit of reading can be found on this subject under the heading of fluid dynamics (a term that can drain the blood from the countenance of most engineering students ). Reynolds numbers, laminar, and turbulent flow are terms that will stalk your nightmares after a couple of terms of studying these concepts. This is the hell Archimedes and Bernoulli explored.

As far as what the subject of the instigating thread implied, consider the following, crude, cross section of a solid mainstock and cup with the addition of the ring:

The blue represents the wood body of the mainstock, and the mainstock cup. The yellow/gold is the metal bits, and the green outline indicates the additional ring (I'm using powerpoint to draw this as I couldn't get to a real CAD program at the time). The cup in the end of the disc of the ring would create a chamber common to the volume of the drone sockets. How much coupling would occur, again, is open to speculation. There would be a shorter, more (for loss of a better word) voluminous passage between the resonating chambers than in a solid mainstock. But again, I'd like to see visual proof whether phase locking occurs in a hollow chamber, or in this case what I would call a low coupling impedance cavity.

Don't set a timetable on me (since I'm still working multiple jobs to catch up with the bills incurred during long unemployment), but I'm inclined to set up an experiment with three audio transducers, a bit of electronics, a multi-channel oscilloscope, and a hollow mainstock (of which I still owe a few euro to BillH (I'm working on it ). With a bit of measurement, and correction for difference in drone length, I'll put something together (don't expect the quality of a submission to the Royal Society) with pictures and big words I tell myself I understand.


dave boling

[uillmann]

I suppose this is intended to be a theoretical drone stock, as fail to see how this design would supply air to the regulators. In any event, any coupling achieved by the drone tongues will be pretty hard to discern with an oscilloscope. If it were found, it would show perfect sine waves doubled and quadrupled off the bass drone. That ain't gonna happen, folks. In the first place, the harmonic distortion alone from just a single drone would nullify the whole concept. Even if it did happen, in real life it wouldn't sound nice, as we tend to hear low pitches lower than they really are, and high ones higher, (one of the reasons why pianos are not tuned to simple mathematical ratio.) Not only that, but no drone is going to remain completely reactionless to the needs of a chanter. I'm afraid the best we can hope for is a reasonably steady pitch and pleasant tone.

[Torrin Riáin]

I've modified the drawing slightly to make it more accurate. The curved brown lines represent the bag.

image post

[daveboling]

I suppose this is intended to be a theoretical drone stock, as fail to see how this design would supply air to the regulators.

Torrin is correct. My model was rushed, and reflected more how I would envision such a ring incorporated to "join" the resonating chambers of the drone reeds, rather than the configuration of the original drone stock of note. Also, as regulators, whether in a hollow or solid mainstock, do not exist in the same chamber as the drones, addition of regulator sockets would only complicate an already rushed illustration. The exception would be in the rare (in the last century) mainstock which does not incorporate a drone cutoff switch.

In any event, any coupling achieved by the drone tongues will be pretty hard to discern with an oscilloscope.

Actually, close miking of each drone, with a bit of acoustical dampening between should yield serviceable waveforms. I experimented with this last evening, and with a shotgun mic, and a bit of cotton batting misappropriated from the wife's Christmas tree skirt, I was able to isolate each tone tolerably. This was with a solid mainstock as I've no hollow mainstocks in hand.

Even if it did happen, in real life it wouldn't sound nice, as we tend to hear low pitches lower than they really are, and high ones higher, (one of the reasons why pianos are not tuned to simple mathematical ratio.)

The altering of pitch, from true, to get a pianoforte sounding psychologically "in tune" across seven (7) octaves is done progressively to the extremes of the range. The range between the tenor and bass drones is two (2) octaves. When I tune my drones, I normally tune the baritone first to the chanter, and then the bass to the baritone, the tenor to the baritone, and finally the tenor against the bass, with a goal of zero detection of beat frequency. Is this incorrect?

Not only that, but no drone is going to remain completely reactionless to the needs of a chanter. I'm afraid the best we can hope for is a reasonably steady pitch and pleasant tone.

Please don' take this question the wrong way: How much effect would a chanter reed, separated from the drone reeds by a small diameter tube, a lossy-walled bag, and constricted (between the drone cutoff switch and the drone socket) passage effect the drone reeds compared to drone reeds interaction in the close proximity of a common chamber?

What I'm going to try to detect, is whether the resulting pressure waves are in phase when inside the mainstock. They likely will not be when exiting the individual drones due to differences in bore profiles between the drones, resulting in drone lengths which are not doublings when moving from tenor to baritone to bass. However, the speed of sound, irrespective of drone bore profile is consistent (I'm going to assume an adiabatic process since the amount of airflow, from what I can detect, does not approach that of a significant pressure increase due to drone backpressure), so adjustments can be calculated. All of this may not sway anyone from their current viewpoint, but I am a point where I need to do something to satisfy my own curiosity, to the level that I can reasonably achieve. If you disagree with whatever I present, put together an empirical exercise of your own, and present your refutation.

As I should have stated long before this point, I greatly appreciate everyone's input on this subject. I don't know if this will result in anything satisfying to you or me, but I'm tired of mentally kicking this can down the road.

dave boling