Josh,
How many hours on the Gjallerhorns so far?
Looks like the voice coil former to aluminum bond would be an area of stress concentration.
Is the former glued directly to the aluminum, or is there some build out material in that area ?
Maybe 100? They probably get at least 6 a week.
These have a large reinforcement collar that mounts to the former, that the cone sits into and there is a LOT of adhesive and surface area. The former is stainless steel. I thought I had a picture of the cone former joint but I do not.
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@ weltersys
Yes those Exremely high SPL figures seemed impossible to me. So in your opinion how far can we go actualy back from 1M & still get a trustworthy ID figure ?
I used to look after a sound system in a nightclub several years back, which had four x EV MT4 in the line up. I found them loud, but a bit rough sounding, no matter how they were EQ'd etc !
Ya think ?
Yes those Exremely high SPL figures seemed impossible to me. So in your opinion how far can we go actualy back from 1M & still get a trustworthy ID figure ?
I used to look after a sound system in a nightclub several years back, which had four x EV MT4 in the line up. I found them loud, but a bit rough sounding, no matter how they were EQ'd etc !
Ya think ?
How far back the inverse distance law would be applicable is dependent on the driver or exit size.
I’ll quote julienb34:
"it's easy to find the the near-field/far-field transition with the formula used for line array, you can find here: http://www.jblpro.com/catalog/suppor...1009&doctype=3
So imagine the mouth of the horn is 1,20m large.
For 100Hz: (1.2*1.2*100)/690= 0.20cm, so far field begins at 20 cm ."
The above formula seems reasonable for what happens outside a horn, I don’t know if the same formula would apply in the throat of a horn, but it seems to be close.
What kind of peak levels do they usually see in those 100 hours ?
The hour rating reminded me of my flight log, I had an aluminum reduction drive bracket fail from stress cracks after only 16 hours of use after an inaccessible screw (one of three) worked loose. Landing without a propeller in a rough feild is interesting
.What would you estimate the area of the reinforcement collar that mounts to the former to be?
A stainless steel former, never heard of that before !
"Perfect" stainless steel is supposed to be non magnetic, but all the stainless I own (boat hardware, screws, knives, etc.) is fairly magnetic.
Whatever the SS is doing to the magnetic circuit seems to be benign, the distortion specs of the Gjallerhorn you just posted are quite impressive for the output level.
It will be interesting to see how the Othorn compares for output and distortion.
Art
@ weltersys
Your JBL link doesn't work, it's not complete ? Can you repost it please
www.jblpro.com/catalog/support/getfile.aspx?docid=1009&doctype=3
All of TC's drivers use a stainless former now that is wrapped in a nomex winding with kapton. I had never heard of this either but it seems to work. BTW did you see the pictures of the B&C split wind coil?
Peak levels...I don't know they get kick drum and bass guitar so the kick drum is a pretty good peak but short duration. It is nothing like a DnB or dubstep show. I would say moderate?
Peak levels...I don't know they get kick drum and bass guitar so the kick drum is a pretty good peak but short duration. It is nothing like a DnB or dubstep show. I would say moderate?
I did see the pictures of the B&C split wind coil, tricky guys, those Italians
.How many watts or volts does "moderate" translate to ?
Interesting, stainless steel. I wonder why they chose it - it certainly doesn't have great specific modulus, or thermal conductivity.
Stainless steel has small spacing between the steel molecules compared to aluminium and copper and works therefore better for demodulating flux from the voice coil. Funny is that TC uses aluminium demodulating rings in the motor section while aluminium has the worst demodulating capabilities compared to stainless steel or copper (I guess it functions more as a heatsink).
Stainless steel is considered as a 'slow' absorber and 'slow' releaser of heat compared to aluminium or copper but that doesn’t mean stainless steel is a bad thermal conductor. Another advantage over aluminium is that heat expansion and/or deformation factors under high temperatures are much lower. The biggest disadvantage to use stainless steel is the more weight. Titanium would be better in all areas but it would rise the price considerably.
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Do you have anything that corroborates what you are saying? I've always read that electrical conductivity is what is necessary for flux demodulation.
Yes, stainless steel is a bad conductor for both heat and electricity. A material datasheet would be rather enlightening, I think.
Titanium is an even worse heat conductor.
I suppose you want me to be more precise. Why you think they make trafo's from iron or steel and not from aluminium? It's the mass/density that counts for flux (with the exception of the right titanium alloys). That's why some companies state that stainless steel can be used also.
Titanium is a better heat conductor then stainless steel but aluminium and copper are by far better. Although iron and steel are mostly used for trafo's titanium has better electrical capabilities. But the trick is the right alloy mixture. If you mix silver with titanium the heat and electrical conductive capabilities rise very rapidly. There are also procedures that allow to higher the density of the titanium alloy, this will increase the heat and electrical capabilities even further. Titanium has the lowest thermal expansion and almost doesn't change it's electrical capabilities below 300 degrees Celsius. So called aluminium demodulating rings are more thermal rings then flux rings simply because the lack of mass and density of the material. The only demodulating rings that actually are effective for sub range (below 150Hz) are made out of copper (preferably pure copper) or titanium alloys (but that is to expensive anyway). Some companies say, it's not just TC, stainless steel is another option but I haven't seen any data from that.
Titanium is a better heat conductor then stainless steel but aluminium and copper are by far better. Although iron and steel are mostly used for trafo's titanium has better electrical capabilities. But the trick is the right alloy mixture. If you mix silver with titanium the heat and electrical conductive capabilities rise very rapidly. There are also procedures that allow to higher the density of the titanium alloy, this will increase the heat and electrical capabilities even further. Titanium has the lowest thermal expansion and almost doesn't change it's electrical capabilities below 300 degrees Celsius. So called aluminium demodulating rings are more thermal rings then flux rings simply because the lack of mass and density of the material. The only demodulating rings that actually are effective for sub range (below 150Hz) are made out of copper (preferably pure copper) or titanium alloys (but that is to expensive anyway). Some companies say, it's not just TC, stainless steel is another option but I haven't seen any data from that.
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Originally Posted by Josh Ricci
All of TC's drivers use a stainless former now that is wrapped in a nomex winding with kapton. I had never heard of this either but it seems to work.
Aluminum still seems to be on the top for strength to weight vs. cost.
All of TC's drivers use a stainless former now that is wrapped in a nomex winding with kapton. I had never heard of this either but it seems to work.
It would seem the stainless steel has been added to the former for properties other than thermal or strength, it is not much better strength to weight than Kapton.
Aluminum still seems to be on the top for strength to weight vs. cost.
Attachments
Transformer steel requires high permeability, among other factors. It has nothing to do with density in and of itself (copper is even more dense than steel, too).
I have never heard of a transformer that used a stainless steel core.
Titanium alloys typically have a thermal conductivity of ~7 W/m-K while a stainless steel alloy such as 304 has a thermal conductivity of ~20 W/m-K. Aluminum and copper have TCs of 250 and 400, respectively, same units. Titanium, and to a lesser extent, stainless steel, are notorious for their poor thermal conductivity.
Sorry, what you are telling me goes against the grain of current knowledge. Without further proof I'm not really interested in hearing more about this.
I wrote “It's the mass/density that counts for flux”, that means the relation between mass/density and flux not just density.
That value number is related to industry standard titanium – nickel alloys and doesn’t count for titanium-silver alloys. If you look for charts look for high silver values above 6%.
I haven’t stated or suggested that copper or aluminium have less thermal capabilities. I stated if you want to enhance the thermal and electrical capabilities of titanium, an alloy with silver is the best option and it will be much better thermal and electrical conductive than any stainless steel variant.
Aluminium has the highest heat expansion factor of all and also the adhesive materials that are attached to the aluminium can get in trouble at high temperatures. Even though it has better strength/weight ratio's it isn't the right material so far for using as the piston. Temperatures in VC's of PA drivers can raise above 250 degrees Celsius.