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Quincke tube adjustment
Posted: Wed Jan 25, 2023 1:59 am
by streetmechanic14
The Quincke tube seems simple enough in principle but I'm curious about its specific function on my Expert Senior. Is it intended to tune out an unwanted peak in the gramophone itself or some characteristic common to the records it was expected to play? Did Ginn offer instructions for its adjustment or were owners just told "don't touch it"?
-Dave
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 2:22 am
by Steve
I honestly believe It was an early example of "snake oil" in an industry that would later be full of it. Adjust it for yourself and see if it makes a difference to the sound
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 3:05 am
by emgcr
Agreed ! It is possible a passing bat may be able to discern differences with various settings but my ears have never been able to hear them !
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 4:40 am
by epigramophone
I have tried the full extent of adjustment and can detect no difference. I now leave it fully screwed in.
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 7:23 am
by Orchorsol
emgcr wrote: ↑Wed Jan 25, 2023 3:05 am
Agreed ! It is possible a passing bat may be able to discern differences with various settings but my ears have never been able to hear them !
AHA - you may have hit upon something there Graham. Maybe that's why those bats found their way inside the Fitzpatrick gramophone!
I've never found any difference either, although I must admit I've never really played with my Quinckes much.
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 7:50 am
by physicist
Assuming the principle of its function is phase cancellation, a sound wave passing down the tube, bouncing off the plug and returning to the main channel would result in some noise cancellation at a frequency where the total path length (2*tube length) matches half a wavelength.
The maximum length is around 15mm which gives a frequency of about 5.7KHz. This is in the audible range but I don't have any 78s that generate much signal at this frequency. Screwing the plug further in would, as Graham has pointed out, take the effect up into bat signal range. A significantly longer tube would be needed for any audible effect. I did try removing the plug and attaching a length of copper tube (closed at the end) to reduce the frequency. An inconvenient length of tube is needed to have a noticeable effect.
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 4:25 pm
by chunnybh
I believe the initial design of the Quincke tube was for phase cancellation in early acoustic records. To basically get rid of the shrill factor with small diaphragm mica soundboxes.
I'm sure I read somewhere that the Quincke tube adjustment was to balance the size of the airgap behind the soundbox. Makes sense if different soundboxes have different airgaps. Balanced it would allow easier move of the diaphragm. Perhaps we should be experimenting with earlier mica soundboxes.
From The Gramophone:
Since a diaphragm emphasises one pitch more than others the distortion caused by this can be avoided by the use of a goose-neck designed to absorb tones of that pitch. When the diaphragm is mounted in a sound-box its resonance peak is flattened out by damping arrangements so that instead of over-emphasising only one pitch, the sound-box responds most effectively to a short range of pitch. So long as the pitch of the goose-neck lies somewhere near the middle of that range the reproduction will be more even. But if it lies outside that range it will make the resonance peak more marked than ever. It is for this reason that large sound-boxes are usually exceedingly “ tubby ” when used with a gooseneck tone-arm though they may be quite otherwise on a straight arm. Similarly a small sound-box may be so shrill as to be unbearable on a straight arm, but exceedingly effective on a goose-neck with a “ dead-end.” Theoretically it is desirable for a goose-neck arm to have a “ dead-end ” whose distance from the centre line of the tone-arm is adjustable since by that means the pitch of the goose-neck could be adjusted to suit the sound-box.
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 5:05 pm
by physicist
Are there earlier designs using longer quincke tubes? The EMG/Expert quincke tubes seem to be too short to make a significant difference in the frequency range that can be heard with their machines.
I have re-visited my investigation of a longer quincke tube. The attached image shows the frequency response difference with a much longer tube.
The red curve is the frequency response I get when recording Fats Waller's "Copper Colored Gal". The green curve is the response with an extended quincke tube. The difference is shown in the brown curve. The dip at ~1250Hz is consistent with a quincke tube length of ~70mm.
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 6:42 pm
by Inigo
This is very interesting. In any gooseneck tonearm of the wide screw cup lid at the dead end opposite the gooseneck, a Quincke tube with the same thread could be made and replace the original screw cup lid, and then we would have an adjustable notch filter to get rid of the infamous Exhibition ringing tone... 70mm for 1250Hz notch, 86mm for 1000Hz... I have to try that.
Probably the damping effect of the fulcrum springs would make something similar when properly adjusted. But who can adjust an Exhibition soundbox? Not me...
I've tried many times and just when I believe I got it, some other record rings awfully and gets me down... Spanish Odeon recordings of early twenties are top most ringing, rendering the audition completely unpleasant. I have to use one of these for adjustment of the Exhibition. But if you adjust to that, other records sound muffled. I've arrived to the conclusion that one has to keep at hand two soundboxes at least, adjusted differently: one for the "strong" records and another for the"weak" records...
Re: Quincke tube adjustment
Posted: Wed Jan 25, 2023 8:19 pm
by JerryVan
I prefer to use a retractable Flemming rod myself.
Okay, seriously, I've only been in this hobby for 40 years, so I'm just new at this, but WHAT IS A QUINCKE TUBE???