I attached the upper end of the diaphragm/rod in my Planot to a bearing, and also screwed the whole unit down to a heavy block of wood, to reduce vibrations.
Positioning the upper bearing was a little ticklish, but I found I could get it quite accurate by using a pin stuck in the end of the rod as a guide.
Here's a photo of the modified unit:
It looks more rickety than it actually is!
Now it sounds somewhat louder, and there is less vibration. I took a spectrum of Pink Noise with my IE35. Here's the corrected response:
Lots of resonances, and essentially no output below about 200Hz. I found I could reduce the amplitude of the resonance peak at 560Hz by gently touching the diaphragm/rod. No doubt it's due to some mode of vibration of the rod.
My impression, as Ziggy has noted, is that the construction tolerances and materials are crucial to how well this will perform. I'd welcome suggestions on how I could tweak my prototype to improve its performance 🙂
Positioning the upper bearing was a little ticklish, but I found I could get it quite accurate by using a pin stuck in the end of the rod as a guide.
Here's a photo of the modified unit:
An externally hosted image should be here but it was not working when we last tested it.
It looks more rickety than it actually is!
Now it sounds somewhat louder, and there is less vibration. I took a spectrum of Pink Noise with my IE35. Here's the corrected response:
An externally hosted image should be here but it was not working when we last tested it.
Lots of resonances, and essentially no output below about 200Hz. I found I could reduce the amplitude of the resonance peak at 560Hz by gently touching the diaphragm/rod. No doubt it's due to some mode of vibration of the rod.
My impression, as Ziggy has noted, is that the construction tolerances and materials are crucial to how well this will perform. I'd welcome suggestions on how I could tweak my prototype to improve its performance 🙂
When you actuate a long rod at one end only, it behaves more like a bending wave transducer and not like one big diaphragm moving in unison.
You have to unleash the unwanted energy at the other end of the rod, you can make a bearing of absorbing material like foam or rubber weatherstriping and make it adjustable by compression.
I think the concept is interesting but it is a fundamental flaw to move such a long diaphragm at one end only.
Place a motor at the top as well or better yet, actuate the rod in its entire length, like a ribbon.
JB
You have to unleash the unwanted energy at the other end of the rod, you can make a bearing of absorbing material like foam or rubber weatherstriping and make it adjustable by compression.
I think the concept is interesting but it is a fundamental flaw to move such a long diaphragm at one end only.
Place a motor at the top as well or better yet, actuate the rod in its entire length, like a ribbon.
JB
Maybe the only way it will work is like a bending wave transducer.Its the only way I can see it work.
Andrè, if you want it to act like a bending wave transducer, you either have to absorb the wave just like the surround in a normal speaker, or match the acoustic impedance of the diaphragm to the air very carefully.
JB
JB
thinkpad I ergre .But you need too have under and over pressure too make sound.And I cant see this transducer doing this in a normal way. So I am thinking if you try too make ridigt and so one like a normal transducer, it will not produce any sound ?.
ABJensen said:
Thinking only pressure = sound is the same thinking that "proves" that dipole loudspeakers can't work - even though they DO work.
The soundboard of an open piano does not flex and produce sound as a simple piston diphraghm at all. The complex vibrations actually all "should" zero-out. And they do - just not in the same place and time.
'Disturbing' air - like a ribbon driver or the Planot - produces local pressure variations. While the net result is not a sum pressure change in the room, it still produces minute local variations in pressure - vibration - to the air at our ears. At higher frequencies this is pretty much what a traditional boxed piston is doing anyway, as the net pressure change in the room is negligible.
It's only at lower frequencies where the tradeoffs become brutally apparent. Producing bass is more easily accomplished with enclosed piston (or much larger planar) drivers that produce the familiar pressure.
That's why many (though not all**) dipole systems are hybrids, using traditional boxed bass.
-- TubaMark
**There are sonic reasons that some folks still go to all the trouble of creating large, comparitively "inefficient" dipole or planar systems for bass. It's not simply a matter of one being much bigger than the other, but rather the way the room interacts with the system
jjbunn said:
An easy measure would be encasing the balsa with Rohacell stripes. And the direct comparison of sensitivites would test André's bending wave hypothesis. Usual contact glue doesn´t work well for balsa and probably PVA not for Rohacell, but I can imagine PU works.
I will build build a "big one" with my 30x30x1000mm rod to see what is the LF limit of the concept and care about resonances later.
Oliver
I'd be interested to see the results of the following experiment:
There's a big assumption that the flat faces of the transducer rod are responsible for sound emission - hence the triangular facets of the Planot design. However, if there is plenty of bending wave and transverse modes in the rod, a cylinder might also give a significant output.
Thoughts please?
Ed
There's a big assumption that the flat faces of the transducer rod are responsible for sound emission - hence the triangular facets of the Planot design. However, if there is plenty of bending wave and transverse modes in the rod, a cylinder might also give a significant output.
Thoughts please?
Ed
Ed Holland said:
I wondered this, too. My rod is square in cross section: would a circular cross section also work? I bet it would, but it would not be from pressure waves produced by rotational motion - it would be from flexing etc. as others have noted.
For moving the most air, some sort of propellor blade shape would appear to be best, with several vanes of maximum length. Looking down the rod's axis, a good shape would be a spikey star.
The constraint is that you want to reduce or eliminate "flapping" of the vanes at the ends, and you also want to make the moment of inertia around the axis minimal. So you want something very stiff, with lots of surface area, lots of faces, and with all its weight at the axis.
I think everyone is missing the physics behind this design, it it not a bending wave speaker or transmission line ect..... it a mechanical air resonance design it does not transmit vibrational energy it makes it via direct excitation of air via movement similar to fan engines.
for example, take a piece of ridged material make sure it has a proper attack angle and move it at 60 cycles per second, you will get a proportional 60 cycle air wave of the leading edge, sound via mechanical articulation similar to aircraft propellers cutting through air, but instead of trying to move air your making it resonate.
for example, take a piece of ridged material make sure it has a proper attack angle and move it at 60 cycles per second, you will get a proportional 60 cycle air wave of the leading edge, sound via mechanical articulation similar to aircraft propellers cutting through air, but instead of trying to move air your making it resonate.
tiltedhalo said:
That's fine, if you can establish that this is the only means of sound wave excitation. To do so requires experimentation using scientific principles, to determine which among a number of potential mechanisms are responsible for turning the excitation from the motor into sound waves. Only then do you have a sound basis for transducer design and development. That is what members like jjbunn and ziggy are trying to achieve in their tests.
tiltedhalo said:
I think I agree with you about the physics, but I'm not sure I understand your disinction regarding moving the air and making it resonate. Since the vanes/sides of the rod are moving, the air is being pushed backwards and forwards and creates a pressure wave.
The physics appears to be very simple.
What is not so simple is the other unwanted vibrations which cause sound to be emitted.
An interesting experiment would be to use one of these devices as a microphone: simple enough, just connect the voice coil to a phono input (would that be the appropriate impedance?) on your amp, and bellow at it 🙂
You could set one up in the middle of a concert hall, record a concert, then play it back later to exactly reproduce the event.
I like the microphone idea, but that leads us back to the inherent problems in the design, like a microphone the transducer must be very lite and fast to capture a wide dynamic range, something I dont think the Planot driver is.
I tried a simple, very simple experiment the other night. I took a moving magnet AC fan motor added a resistor to get the impedance up around 6ohms and gave it some audio, presto sound not good not allot, but sound with hardly any resonance from the windings.
I think the design has great merit but has some serious engineering issues to make it work well.
I wonder what an actual Planot driver sounds like, he should post some high quality microphone recordings of it. Might change some views on the design.
I tried a simple, very simple experiment the other night. I took a moving magnet AC fan motor added a resistor to get the impedance up around 6ohms and gave it some audio, presto sound not good not allot, but sound with hardly any resonance from the windings.
I think the design has great merit but has some serious engineering issues to make it work well.
I wonder what an actual Planot driver sounds like, he should post some high quality microphone recordings of it. Might change some views on the design.
I`m toying with the idea of making a scaled-up version of this simple experiment
http://www.metacafe.com/watch/971400/unexplained_phenomenon_simplest_electric_motor/
JB
http://www.metacafe.com/watch/971400/unexplained_phenomenon_simplest_electric_motor/
JB
Hey guys !........been a bit busy work wise(real work) and re-built my GAINCLONE ..........and blew it up!!!!.........that's the price for rushing your work and not checking it
It's great to see so much input on this subject, especially jjbunn, great stuff pal!.....love the response curve even though it displays what we feared the most - lousy performance and heaps of vibration problems as expected.
Reading through the latest posts I tend to agree that the PLANOT design was always meant to be an ''air chopper''😀 . It was never designed to be a vibration producing stick exited by the voice coils attached to it - as jjbunn and I have found.
It's a pity that John(PLANOT designer) decided that we all hated his guts or something because we are all now guessing and theorising on what it is and what it's really supposed to do in the way of reproducing sound.
Yes, there are many good ideas and alternatives being passed around on this thread.That's great to see and is what we're here for.
Being an Aussie, I am always keen on new technology. I had a great interest in the NXT distributrd mode system until I heard a couple of panels in action. They were not for me and certainly more hype than actual useable performance in an audiophile application.
I fear that the PLANOT is a clone of such a being - lots of unsubstantiated praise on how good it is yet a flat refusal to release simple specifications and test responses when asked for. That reeks of possible and misleading information on a product that doesn't really work that impressive at all. Maybe in some areas, but disasterous in others, which is most likely the case.
MOBILEUSA.........if you know john personally, inform him that he needs to supply the information required to substantiate his claims. He needs to post some DECENT photographs of his invention - from all angles including close-ups,(not just voice coils and chunks of aluminium and distant shadowy objects like the latest one).
We would all love to see a video of the PLANOT in action so that the principle of operation can be seen.
We are not here to rip off his invention, we only want verification that it does what it does. Hell, I'll be the first to buy one or a kit should that be available.
So, for the time being, there is no point in producing an updated version of my previous experiment as it obviously doesn't work and most likely never will meet high quality audio levels
It's great to see so much input on this subject, especially jjbunn, great stuff pal!.....love the response curve even though it displays what we feared the most - lousy performance and heaps of vibration problems as expected.
Reading through the latest posts I tend to agree that the PLANOT design was always meant to be an ''air chopper''😀 . It was never designed to be a vibration producing stick exited by the voice coils attached to it - as jjbunn and I have found.
It's a pity that John(PLANOT designer) decided that we all hated his guts or something because we are all now guessing and theorising on what it is and what it's really supposed to do in the way of reproducing sound.
Yes, there are many good ideas and alternatives being passed around on this thread.That's great to see and is what we're here for.
Being an Aussie, I am always keen on new technology. I had a great interest in the NXT distributrd mode system until I heard a couple of panels in action. They were not for me and certainly more hype than actual useable performance in an audiophile application.
I fear that the PLANOT is a clone of such a being - lots of unsubstantiated praise on how good it is yet a flat refusal to release simple specifications and test responses when asked for. That reeks of possible and misleading information on a product that doesn't really work that impressive at all. Maybe in some areas, but disasterous in others, which is most likely the case.
MOBILEUSA.........if you know john personally, inform him that he needs to supply the information required to substantiate his claims. He needs to post some DECENT photographs of his invention - from all angles including close-ups,(not just voice coils and chunks of aluminium and distant shadowy objects like the latest one).
We would all love to see a video of the PLANOT in action so that the principle of operation can be seen.
We are not here to rip off his invention, we only want verification that it does what it does. Hell, I'll be the first to buy one or a kit should that be available.
So, for the time being, there is no point in producing an updated version of my previous experiment as it obviously doesn't work and most likely never will meet high quality audio levels
Refinements to my Planot prototype
I replaced the rather thick wires that I had connecting the voice coil by some very thin and flexible transformer wire. Hopefully this allowed the voice coil to rotate a little more freely.
I then glued a small, light magnet to one side of the balsa wood rod's base, and positioned a powerful magnet nearby.
This positioning magnet is probably quite important to the sound quality: my guess is it limits excursions by the rod, and serves to prevent distortion. In fact you can hear the improvement by moving the powerful magnet backwards and forwards from the light magnet.
Here is the 1/3 octave Pink Noise response: red curve with magnet, blue without.
The HF peaks are significantly reduced by using the magnet, but the LF resonances appear to be enhanced 🙂
Here's a photo showing the new arrangement.
The sound quality with music is pretty atrocious, but I'm sure this is a fault of my shoddy prototype. I'd love to hear a professionally made device: I bet it sounds superb.
I replaced the rather thick wires that I had connecting the voice coil by some very thin and flexible transformer wire. Hopefully this allowed the voice coil to rotate a little more freely.
I then glued a small, light magnet to one side of the balsa wood rod's base, and positioned a powerful magnet nearby.
This positioning magnet is probably quite important to the sound quality: my guess is it limits excursions by the rod, and serves to prevent distortion. In fact you can hear the improvement by moving the powerful magnet backwards and forwards from the light magnet.
Here is the 1/3 octave Pink Noise response: red curve with magnet, blue without.
An externally hosted image should be here but it was not working when we last tested it.
The HF peaks are significantly reduced by using the magnet, but the LF resonances appear to be enhanced 🙂
Here's a photo showing the new arrangement.
An externally hosted image should be here but it was not working when we last tested it.
The sound quality with music is pretty atrocious, but I'm sure this is a fault of my shoddy prototype. I'd love to hear a professionally made device: I bet it sounds superb.
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