Please explain, or show images/diagrams?
Goodmans products are not often found in the USA. I have never seen this driver and have no idea how a cone type woofer/coaxial driver is similar to a compression driver.
I did search, but I was not able to find an image that clearly shows the suspension elements.
Goodmans products are not often found in the USA. I have never seen this driver and have no idea how a cone type woofer/coaxial driver is similar to a compression driver.
I did search, but I was not able to find an image that clearly shows the suspension elements.
Change that... this link shows a drawing from an advertisement that shows the suspension. http://www.soundup.ru/images/stories/archive/Classic/speakers/goodman-axiom-80-pair/goodmans_axiom2.jpg That and another color jpeg shows that the suspension elements are straight phenolic fingers.
1) they are phenolic, not metal, not beryllium copper or phosphor bronze alloy.
2) they are straight fingers, not "S" or "Z" shaped.
This is a considerable distance from the suspension of the Yamaha 6681 series.
Closer are multiple pre-WWII speakers. Many used "S" or "Z" shaped alloy spider assemblies. One that I can cite is the Jensen A-12, although it post dates WWII (fairly certain of that) and it is a field coil speaker, never-the-less it has that "S" shaped metal spider. Beyond that there is little similarity.
1) they are phenolic, not metal, not beryllium copper or phosphor bronze alloy.
2) they are straight fingers, not "S" or "Z" shaped.
This is a considerable distance from the suspension of the Yamaha 6681 series.
Closer are multiple pre-WWII speakers. Many used "S" or "Z" shaped alloy spider assemblies. One that I can cite is the Jensen A-12, although it post dates WWII (fairly certain of that) and it is a field coil speaker, never-the-less it has that "S" shaped metal spider. Beyond that there is little similarity.
Straight fingers will have a non-linear displacement curve.
The point of the "Z" shaped fingers of the Yamaha driver is to have (within limits) an essentially linear displacement curve. The reason(s) for that are disclosed in the patent(s).
The point of the "Z" shaped fingers of the Yamaha driver is to have (within limits) an essentially linear displacement curve. The reason(s) for that are disclosed in the patent(s).
This is closer by far:
http://www.radiomuseum.org/forumdata/users/14186/Crossley_speaker_restoration/CrosleySpeaker03.jpg
Usually, I don't like to link, because later on the link has gone away and a reader can not see the image. I'm lazy today. But this looks like a 45rpm record adapater - one of those flat plastic ones, with the "S" shaped fingers. Good enough.
They made versions that went inside the VC, like this one, and outside, used rather than the most commonly found (today) phenolic pleated spider.
http://www.radiomuseum.org/forumdata/users/14186/Crossley_speaker_restoration/CrosleySpeaker03.jpg
Usually, I don't like to link, because later on the link has gone away and a reader can not see the image. I'm lazy today. But this looks like a 45rpm record adapater - one of those flat plastic ones, with the "S" shaped fingers. Good enough.
They made versions that went inside the VC, like this one, and outside, used rather than the most commonly found (today) phenolic pleated spider.
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bear,
I'm not going to model that last image you have linked to and do a motion study but just my gut level instinct would tell me that those curvilinear leaves would do two things. One it would decrease the stiffness greatly over a solid center planar spring but what concerns me it it does seem that it would cause a rotational movement while being stretched in the Z axis. As the fingers are stretched in that direction the fact they are all turned in the same direction the length of those would force the outer rim to turn? Very strange to say the least. I don't feel like modeling that and doing any motion study but I think I am right.
I'm not going to model that last image you have linked to and do a motion study but just my gut level instinct would tell me that those curvilinear leaves would do two things. One it would decrease the stiffness greatly over a solid center planar spring but what concerns me it it does seem that it would cause a rotational movement while being stretched in the Z axis. As the fingers are stretched in that direction the fact they are all turned in the same direction the length of those would force the outer rim to turn? Very strange to say the least. I don't feel like modeling that and doing any motion study but I think I am right.
Not sure I want to experiment with no protection cap I honestly don't hear it that much. The going rate for two of these JA-6681B is 900$ on ebay.
Yes, it does impart a slight rotation.
So does the angled (pressed) surround on a 555 driver or one like it.
The question is how much.
This was an early method.
Even so, it was as I recall used on the huge Hartley subwoofer as well!
There have been lots of suspension schemes. This is just an example that I thought was more like the edge of the 6681 than the Goodmans.
ooog. maybe it is time to sell the ones I have and buy a set of the asian 555 clones? (btw, have not heard much of them in a year or so...) 😀
Protection Cap
If you run the driver with the passive network built into the amplifer driving it, you do not need a protection cap as an extra protection, it is quite useless.
You have protection caps in the driving amplifier itself!
You have limited the fx by adjusting the kathode caps.
This is more protection than any cap as in a standard passive speaker network!
Any engineer who understands this kind of design will/must recognise this.
Plus you have an output-transformer!
Now, why does an output-transformer protect as well?
But running a compression driver directly without network in the amplifier
and without any protection is imo stupidity
If you run the driver with the passive network built into the amplifer driving it, you do not need a protection cap as an extra protection, it is quite useless.
You have protection caps in the driving amplifier itself!
You have limited the fx by adjusting the kathode caps.
This is more protection than any cap as in a standard passive speaker network!
Any engineer who understands this kind of design will/must recognise this.
Plus you have an output-transformer!
Now, why does an output-transformer protect as well?
But running a compression driver directly without network in the amplifier
and without any protection is imo stupidity
Bear,
If you are twisting the center of the cone if even slightly but the outer edge of the cone is held from turning by the surround then something is having to distort to relieve that stress, I would think it would be the surface of the paper cone. I've been working on some ideas for a spider that could potentially have a more linear travel than a typical spider.
If you are twisting the center of the cone if even slightly but the outer edge of the cone is held from turning by the surround then something is having to distort to relieve that stress, I would think it would be the surface of the paper cone. I've been working on some ideas for a spider that could potentially have a more linear travel than a typical spider.
I have some examples of production speakers that used a more advanced design for metal alloy spiders. I'm not sure if they have problems with self damping or lack thereof.
Linear travel is good, until you have to stop the cone from excessive excursion!! 😀
I agree with what you said regarding that sort of old tyme spider, I think these were rather stiff and very low Xmax devices. The Hartley, however was not...
Jensen A12
and a conventional front suspension.
There are hundrets of drivers which have a phenolic back suspension, that's NOT the point!
It is the front-suspension plus back suspension which makes the Goodmans so special:
http://www.pocketwatchpics.com/ebay/41014066.jpg
http://www.pocketwatchpics.com/ebay/41014067.jpg
But this was a hint about the special suspension of the Yamaha.
and a conventional front suspension.
There are hundrets of drivers which have a phenolic back suspension, that's NOT the point!
It is the front-suspension plus back suspension which makes the Goodmans so special:
http://www.pocketwatchpics.com/ebay/41014066.jpg
http://www.pocketwatchpics.com/ebay/41014067.jpg
But this was a hint about the special suspension of the Yamaha.
The danger of not using a single passive capacitor in series with these drivers is that which comes from either an electronic fault, like motorboating, or from user error - like plugging in a cable with the volume up...
Otoh, if you are using a 2watt amp, perhaps it has insufficient power to damage the diaphragm assembly. I've not tested this theory.
While, at the same time, I personally am willing to take risks with my gear in order to maximize the sound! So, for me, personally, I do not mind connecting my amps directly to the drivers at all. I'll take the risk. I have back-up diaphragms and drivers.
FYI, Odeon, I did say that at various times a group of us played live electric music, guitars, bass, keyboards, including V-drums *direct* into a mixer, and monitored through my system. So, guess I am willing to take some risks. Still using the same drivers and diaphragms. 😀
You going to post any images of your set up?
Ur little SE amps?
The horn(s)?
Otoh, if you are using a 2watt amp, perhaps it has insufficient power to damage the diaphragm assembly. I've not tested this theory.
While, at the same time, I personally am willing to take risks with my gear in order to maximize the sound! So, for me, personally, I do not mind connecting my amps directly to the drivers at all. I'll take the risk. I have back-up diaphragms and drivers.
FYI, Odeon, I did say that at various times a group of us played live electric music, guitars, bass, keyboards, including V-drums *direct* into a mixer, and monitored through my system. So, guess I am willing to take some risks. Still using the same drivers and diaphragms. 😀
You going to post any images of your set up?
Ur little SE amps?
The horn(s)?
Posts that were becoming rather to personal have been deleted. Stick to the technical stuff and argue it out on technical merit. Consider this as a friendly reminder.
Ok, perhaps there is something to learn?
How is the Goodmans suspension similar to the JA 6681, and/or what does it show us?
How is the Goodmans suspension similar to the JA 6681, and/or what does it show us?
Modifying throat
Hi!
I am thinking of using a 1" horn for the JA-6681B. What do you think about this: plugging the throat in the driver with modelling clay and rebore it to 1"?
/Bruno
Hi!
I am thinking of using a 1" horn for the JA-6681B. What do you think about this: plugging the throat in the driver with modelling clay and rebore it to 1"?
/Bruno
I realize that the exit part of the CD can not be separated? If so, it is hard to reshape the exit.
/Bruno
/Bruno