A slug of air , dont pour salt on it
Dave ,
You pretty much got the right idea 🙂
It is sometimes called "mass loading" a pipe (like adding weight) and allows us to shorten the path length while maintaining a low tuning ... Used in moderation it can allow for more manageable box size/dimensions without too much impact upon performance ......
Taken to the extreme you just end up with bass reflex box of course, but we are using it moderately here so we still retain the behavior of a quarter wave resonator ...
A lot of the hi-fi and fullrange DIY enthusiasts use the ML technique in their ML-TL , and ML-TQWP and other related configs using path lengths of as little as 36 inches long (and up from there) ..... The actual path length of the Karlflex configured as series-tuned is around 6 feet+-ish for our 35 to 40hz fb...
If designing with this method for use at higher power levels attention should be paid to air velocity rates to be sure they won't be excessive around the pinch @ full power which can be a some extra hassle for a designer, but that extra hassle is balanced
by the benefits IMHO
.....
In some cases the ML feature can push pipe harmonics (and associated response ripple) higher up in frequency, which is an additional benefit .... Our offset driver placement also helps to alleviate some of that ripple and extends bandwidth ..
Dave ,
You pretty much got the right idea 🙂
It is sometimes called "mass loading" a pipe (like adding weight) and allows us to shorten the path length while maintaining a low tuning ... Used in moderation it can allow for more manageable box size/dimensions without too much impact upon performance ......
Taken to the extreme you just end up with bass reflex box of course, but we are using it moderately here so we still retain the behavior of a quarter wave resonator ...
A lot of the hi-fi and fullrange DIY enthusiasts use the ML technique in their ML-TL , and ML-TQWP and other related configs using path lengths of as little as 36 inches long (and up from there) ..... The actual path length of the Karlflex configured as series-tuned is around 6 feet+-ish for our 35 to 40hz fb...
If designing with this method for use at higher power levels attention should be paid to air velocity rates to be sure they won't be excessive around the pinch @ full power which can be a some extra hassle for a designer, but that extra hassle is balanced
by the benefits IMHO..... In some cases the ML feature can push pipe harmonics (and associated response ripple) higher up in frequency, which is an additional benefit .... Our offset driver placement also helps to alleviate some of that ripple and extends bandwidth ..
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Off topic , FrankenPiezo array note
Made a final adjustment to the transformer driven Frankenpiezo arrays .....
Vertical dispersion was too tightly controlled (for our application) , so i tilted the top and bottom element slightly (using these grey plastic spacers) to widen the vertical "sweet spot" by a small amount... So even if our ears end up a little above the array (standing up in our case) or just below (sitting down) the output from the arrays now stay consistent enough to keep up with the rest of the mix ...... If i had a taller array (like 8 or 12 piezos per array) this physical tilt or curvature may not have been necessary since our ears would have been within the vertical height of the array whether we were sitting down or standing up, but i had to stick with four elements (perhaps 5 if i trimmed them) because that is all i could fit into the front of these cabinets😀 ...
Made a final adjustment to the transformer driven Frankenpiezo arrays .....
Vertical dispersion was too tightly controlled (for our application) , so i tilted the top and bottom element slightly (using these grey plastic spacers) to widen the vertical "sweet spot" by a small amount... So even if our ears end up a little above the array (standing up in our case) or just below (sitting down) the output from the arrays now stay consistent enough to keep up with the rest of the mix ...... If i had a taller array (like 8 or 12 piezos per array) this physical tilt or curvature may not have been necessary since our ears would have been within the vertical height of the array whether we were sitting down or standing up, but i had to stick with four elements (perhaps 5 if i trimmed them) because that is all i could fit into the front of these cabinets😀 ...
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cool - the Goldwood 1016 have been out of stock for some time at PE -I measured a couple of GRS 1005 type and they have a big peak around 11KHz - maybe there's a Franken1005 combo - ? (why can't they make them good in the first place -? lol) did you post the circuit and tap for this array? (seems like you did) - I want 1005 type smooth and on transformer to use with a K-lens
Deep dish Piezo with all of the toppings
Freddi,
It would be great to see someone perform an experiment and put a GRS 1005 element into a GW 1005 horn to see if the response is as wonderful as the 1016 FrankenPiezo .... 🙂
I suppose GRS could easily make them this good in the first place by making a simple alteration to their horn body mold (changing the dimensions of the phase plug and throat to more closely match the GW horn body) ...
Seems like someone should start selling these ...
I think i posted it a while back when we first started talking about Piezos .... The circuit i used is very similar to a transformer circuit you had posted .... My network was just a series cap followed by the 70v transformer's low impedance tap... Then i used the 15w (330 ohm) tap on the step-up side followed by a 400ohm parallel swamping resistor (helps to normalize the impedance response and load that the transformer sees and the voltage it produces) followed by a series resistor (20 to 50 ohm works well) which then connects to the piezo element or elements ... 🙂
I can send you the diagram if you like.
Freddi,
It would be great to see someone perform an experiment and put a GRS 1005 element into a GW 1005 horn to see if the response is as wonderful as the 1016 FrankenPiezo .... 🙂
I suppose GRS could easily make them this good in the first place by making a simple alteration to their horn body mold (changing the dimensions of the phase plug and throat to more closely match the GW horn body) ...
Seems like someone should start selling these ...
I think i posted it a while back when we first started talking about Piezos .... The circuit i used is very similar to a transformer circuit you had posted .... My network was just a series cap followed by the 70v transformer's low impedance tap... Then i used the 15w (330 ohm) tap on the step-up side followed by a 400ohm parallel swamping resistor (helps to normalize the impedance response and load that the transformer sees and the voltage it produces) followed by a series resistor (20 to 50 ohm works well) which then connects to the piezo element or elements ... 🙂
I can send you the diagram if you like.
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I don't know if it will work out the same. It was just plain blind idleness and luck that caused me to stumble upon the Frankenpiezo 1016. I happen to have a spare GRS 1016 and a spare GW 1016 on hand, noticed that the backs were the same size and the screws were in the same locations and then wondered "hmm, what if...".
Usually that kind of approach to experimentation usually results in a copious release of the "magic smoke" 🙂.
When I did the first FR measurement of the combo, I didn't believe what I saw. I actually repeated it a few times and checked for problems with the measuring equipment just to make sure, LOL.
I'd be very surprised if a similar experiment with the 1005 models produces the same results. That would be like winning two lotteries in one year, LOL.
If Freddi still has those GRS 1005s laying around maybe he could try it , if he isn't afraid of any potential Magic Smoke!
Be brave Freddi !😀
I might be making another order from PE soon, so if nobody tried it at that point i might order a few sacrificial 1005s to goof around with...
I never go anywhere - a couple of summers ago in daylight during the buildup of a powerful electrical storm, I had two lightning balls pass over my dead parked car - the first was viewed at around 70 feet away - about a minute later I walked with a friend past the car and the second lightning ball came probably within 10 feet behind us and dissipated into the weeds with a "zzzzzzzzztttt" sound. Two strikes of exceedingly rare ball lightning. (the other viewers had no idea of the event - all had cell phones other than myself)
anyhow, I swept a GRS1005 then Goldwood1005 then GRS element on Goldwood horn = no significant change - some but pretty much the same pattern - I know the Goldwood's phase rod looks crooked on most. I took a horrendous MCM piezo which lacked the phase rod and mated it with the GRS - another horrendous piezo.
MCM part 53-820
-TB46 - I remember Traynor using a similar array
seeing ball lightning essentially in my own yard and twice over the same approximate path seemed a better bet than getting a great Franken1005piezo from GRS w. Goldwood. 😱
anyhow, I swept a GRS1005 then Goldwood1005 then GRS element on Goldwood horn = no significant change - some but pretty much the same pattern - I know the Goldwood's phase rod looks crooked on most. I took a horrendous MCM piezo which lacked the phase rod and mated it with the GRS - another horrendous piezo.
MCM part 53-820
-TB46 - I remember Traynor using a similar array
seeing ball lightning essentially in my own yard and twice over the same approximate path seemed a better bet than getting a great Franken1005piezo from GRS w. Goldwood. 😱
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Freddi,
I wish you could have videotaped those lightning balls. It is very rare to have it come that close to you and live to tell about it. A quick look on YouTube reveals videos that are maybe hundred feet to miles away from high altitude lightning balls. There is not accepted theory for the balls but here is my guess: an initial strike vaporizes Si atoms in soil, the plume of energetic Si (and O atoms) are concentrated and focused into a sphere up by the magnetic field created by the lightning pulse. The highly energetic Si atoms are vibrationally excited, this has a very slow rate of collisional decay via gas kinetic action, and thus the glow is persistent and does not die right away. Takes several seconds for all the excited atoms to decay to their ground state and combine with O atoms to precipitate out as sand dust.
I wish you could have videotaped those lightning balls. It is very rare to have it come that close to you and live to tell about it. A quick look on YouTube reveals videos that are maybe hundred feet to miles away from high altitude lightning balls. There is not accepted theory for the balls but here is my guess: an initial strike vaporizes Si atoms in soil, the plume of energetic Si (and O atoms) are concentrated and focused into a sphere up by the magnetic field created by the lightning pulse. The highly energetic Si atoms are vibrationally excited, this has a very slow rate of collisional decay via gas kinetic action, and thus the glow is persistent and does not die right away. Takes several seconds for all the excited atoms to decay to their ground state and combine with O atoms to precipitate out as sand dust.
baasl
it would have been good - don't own a cell phone and the four or more other viewers did not realize how rare such an event. The energy in the sky must hve been awesome - rain had not come yet and not really dark other than clouds moving in The first ball was ~basketball size - I'm not sure about the one which passed close behind me. There was no overt smell of ozone or burning of foliage - just a "zzzzzzzzzttttttt" sound as the 2nd ball dissipated. I think it formed near an insulator junction. It would have been a great way to exit.
it would have been good - don't own a cell phone and the four or more other viewers did not realize how rare such an event. The energy in the sky must hve been awesome - rain had not come yet and not really dark other than clouds moving in The first ball was ~basketball size - I'm not sure about the one which passed close behind me. There was no overt smell of ozone or burning of foliage - just a "zzzzzzzzzttttttt" sound as the 2nd ball dissipated. I think it formed near an insulator junction. It would have been a great way to exit.
it would have looked something like this crude paint depiction - could the insulation have fed the process? - it started at the wires over to the left and floated to the right over my tarped car
That is a cool "re-enactment" - great visual there with the zig zag dancing path and appropriately sized grapefruit (in your case, basketball) sized ball. They all say it glows like a 100 watt light bulb but Freddi's looks a bit more golden and red.
balls of mystery from above!
You are so lucky to have seen that Freddi ,
I just read up on the subject, wild stuff!
Ball lightning is one of those mysterious things that some scientific minds previously denied even exists because it is so rare and unexplainable ... It is difficult to study because previously it wasn't something you could just easily produce in a lab, but these guys in Brazil managed it based on what XRK was talking about, a highly charged silicon vapor , but can possibly be done with other elements too:
Ball Lightning Mystery Solved? Electrical Phenomenon Created in Lab
You can read lots of anecdotal reports about ball lightning, there are websites with long lists of reports, kinda fun to read🙂 ...
Seems to have happened on planes commonly when static charges build up to to extremes .... Ball lightning is also reported to appear from areas or objects that lightning just struck ...
Seeing ball lightning on, near, or emerging from electrical lines also seems to be a common theme .... There are a few disturbing videos out there with ball lightning actually riding down the electrical lines at a fairly slow pace like some sort of creeping electrical monster from a science fiction horror movie! (not sure if this is the exact same phenomenon)
Nevertheless this ball lightning can contain enough energy to do damage where it discharges like splitting trees and blowing holes in the ground, awe inspiring stuff!
Soooo , extremely rare ball lightning spotted, but the Franken1005 still eludes us!
You are so lucky to have seen that Freddi ,
I just read up on the subject, wild stuff!
Ball lightning is one of those mysterious things that some scientific minds previously denied even exists because it is so rare and unexplainable ... It is difficult to study because previously it wasn't something you could just easily produce in a lab, but these guys in Brazil managed it based on what XRK was talking about, a highly charged silicon vapor , but can possibly be done with other elements too:Ball Lightning Mystery Solved? Electrical Phenomenon Created in Lab
You can read lots of anecdotal reports about ball lightning, there are websites with long lists of reports, kinda fun to read🙂 ...
Seems to have happened on planes commonly when static charges build up to to extremes .... Ball lightning is also reported to appear from areas or objects that lightning just struck ...
Seeing ball lightning on, near, or emerging from electrical lines also seems to be a common theme .... There are a few disturbing videos out there with ball lightning actually riding down the electrical lines at a fairly slow pace like some sort of creeping electrical monster from a science fiction horror movie! (not sure if this is the exact same phenomenon)
Nevertheless this ball lightning can contain enough energy to do damage where it discharges like splitting trees and blowing holes in the ground, awe inspiring stuff!
Soooo , extremely rare ball lightning spotted, but the Franken1005 still eludes us!
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Ball lightening is real
As it seems that this thread has taken a detour, I will add to it.
In the mid '80's my mother was on an Amtrak going from DC to Philadelphia when a ball lightening came through the front of the train car.
It traveled down the center of the aisle and went to the back window where it exploded, stopping the train dead in (on) it's tracks.
All the passengers had to disembark and walk a mile through the woods to catch a bus to Philadelphia.
I would have not believed her story until her friend/ co-traveler told the same story at a separate time and place, not in her presence.
They both described it as basketball sized, glowing orange, crackling and giving off a strong Ozone smell.
Believe it or not, I finally did (believe it) after they both told the same story.
Eventually my mother said she did not want to talk about it.
She was always very agitated when she had talked about the subject.
I have never found any mention of this in news stories, anywhere.
It happened in the mid '80's.
Dave
As it seems that this thread has taken a detour, I will add to it.
In the mid '80's my mother was on an Amtrak going from DC to Philadelphia when a ball lightening came through the front of the train car.
It traveled down the center of the aisle and went to the back window where it exploded, stopping the train dead in (on) it's tracks.
All the passengers had to disembark and walk a mile through the woods to catch a bus to Philadelphia.
I would have not believed her story until her friend/ co-traveler told the same story at a separate time and place, not in her presence.
They both described it as basketball sized, glowing orange, crackling and giving off a strong Ozone smell.
Believe it or not, I finally did (believe it) after they both told the same story.
Eventually my mother said she did not want to talk about it.
She was always very agitated when she had talked about the subject.
I have never found any mention of this in news stories, anywhere.
It happened in the mid '80's.
Dave
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here's a GRS1005 vs a Le Son TLC3 to illustrate the current hopelessness in round piezo - Goldwood 1005 are rough too - would have to buy lots and match into pairs for home stereo
1/24 octave resolution
here's another sweep at 10dB lower drive to make sure the soundcard
wasn't overloaded - might not be exact same position for piezos but
close enough for comparison
the original CTS and Motorola 1005 had a noticeable bump around 4-5K
1/12 octave smoothing
1/24 octave resolution
here's another sweep at 10dB lower drive to make sure the soundcard
wasn't overloaded - might not be exact same position for piezos but
close enough for comparison
the original CTS and Motorola 1005 had a noticeable bump around 4-5K
1/12 octave smoothing
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Wow, those are pretty bad....
I know the 3x7's response is pretty bad too, but clears up quite nicely with some damping on the bender and in the chamber. I wonder if the same would work for the 1005?
I used a small piece of leftover Dynamat from my car audio install. Just stuck it on the back of the bender. I'm guessing that it basically damped the 5kHz resonance significantly. A piece of asphalt or butyl rubber flashing should work as well. Experiment with the size for the best results.
thanks - I'll order some car mat. On the 2nd ball lightening which was behind me - I got the following description "It's been a while, but l think it was between 3 and 5 feet diameter, spheroid but flatter on the top and bottom it was bright and localized around a tree overhanging your driveway. It seemed a great flash" - that must have put it less than 10 feet where I and friend were standing !
A roll of adhesive flashing tape from the nearest hardware store should work just as well.