Here is an easy to understand poster about the major sources of distortion in a speaker.
Study it carefully and then we are talking...
http://www.klippel.de/fileadmin/kli...rature/Papers/Klippel_Nonlinearity_Poster.pdf
Study it carefully and then we are talking...
http://www.klippel.de/fileadmin/kli...rature/Papers/Klippel_Nonlinearity_Poster.pdf
"Easy" Always a warning! There is a lot to take in there. It does not show anything about how the motor structure does not produce a uniform field in the gap and the various non-linearity that causes, or how one can use one non-linearity to counter another. Motors are complicated. It makes you wonder how speakers are as good as they are and it does give you more respect for the designers of above par drivers. This will take more than casual reading.
Paul Klipsh was well known for saying distortion and efficiency were inversely proportional. This poster would tend to say otherwise for the motor. Obviously, the efficiency with which a driver is coupled to the air will help as it reduces the displacement for a given SPL, and this shows why that is a big advantage. Unfortunately, high efficiency horns have their own set of added distortions.
A comment was made about different magnet material and how that could effect distortion. I would have thought that a given flux was a given flux. What makes the difference? I have also seen several newer drivers using a set of slugs for magnets instead of a ring. Is this just for ease of manufacturing or is there some actual difference in how the motor works.
Another thread mentioned adding an electoral short between the front and rear pole pieces reduced distortion. I have never seen that done, so I would be skeptical.
I had not heard of Kipple. Thanks.
Paul Klipsh was well known for saying distortion and efficiency were inversely proportional. This poster would tend to say otherwise for the motor. Obviously, the efficiency with which a driver is coupled to the air will help as it reduces the displacement for a given SPL, and this shows why that is a big advantage. Unfortunately, high efficiency horns have their own set of added distortions.
A comment was made about different magnet material and how that could effect distortion. I would have thought that a given flux was a given flux. What makes the difference? I have also seen several newer drivers using a set of slugs for magnets instead of a ring. Is this just for ease of manufacturing or is there some actual difference in how the motor works.
Another thread mentioned adding an electoral short between the front and rear pole pieces reduced distortion. I have never seen that done, so I would be skeptical.
I had not heard of Kipple. Thanks.
Is not the case for a beryllium dome that the mass is so small, that in the upper reaches it is no higher than a soft dome that has decoupled regions? I also remember when I dealt with beryllium tape drive capstan wheels, it was very non-resonant compared to the magnesium wheels. When you set one down on a desk, it has less ring to it and it was higher in frequency. On the other hand, are the voice coil, former, and glue not so much heavier than the dome that the mass is not really important?
Yes, making drivers is still a "black art". The Satori driver started life many years agao where the main designer told me that he is working on a reference driver and he will be ready soon. Now it is here, 4 years later. I do not want to know how many prototypes have being made until this result came out.
Yes, some ring radiators have poor mechanics cheep plastic parts, resonant chambers, etc. I mentioned that.
The published results from the SEAS diamond and the Scan-Speak beryllium show my point. They are less extended in the treble because they do not decouple. In theory they have an advantage in distortion though. That is the old discussion if a hard, medium or soft membrane should be used. The soft dome guys claim sweeter and more extended sound and the hard dome guys think that piston movement is the ticket. i made good speakers with both technologies.
I have made measurements with the same drivers that used different magnet materials.
I found differences in the distortion of the current . I will look if i can find the measurements and then i post them.
Yes, some ring radiators have poor mechanics cheep plastic parts, resonant chambers, etc. I mentioned that.
The published results from the SEAS diamond and the Scan-Speak beryllium show my point. They are less extended in the treble because they do not decouple. In theory they have an advantage in distortion though. That is the old discussion if a hard, medium or soft membrane should be used. The soft dome guys claim sweeter and more extended sound and the hard dome guys think that piston movement is the ticket. i made good speakers with both technologies.
I have made measurements with the same drivers that used different magnet materials.
I found differences in the distortion of the current . I will look if i can find the measurements and then i post them.
Scanspeak do have the 6640 though, their other Beryllium dome and this doesn't have anywhere near as much droop, its breakup is also less severe too.
http://www.scan-speak.dk/datasheet/pdf/d3004-664000.pdf
This driver has exceptional distortion performance as measured by others and I can't really see any reason why you'd pick the new scan tweeter over this one.
http://www.scan-speak.dk/datasheet/pdf/d3004-664000.pdf
This driver has exceptional distortion performance as measured by others and I can't really see any reason why you'd pick the new scan tweeter over this one.
"After EQ" Well, maybe it is just me, but one of the things I expect when one jumps this high in the price line is drivers should get easier to use. The extra money should go to resolving the various issues. At the very least, they should provide sufficient application notes. Look at the information provided for a $.50 op-amp vs. a $500 tweeter. Something is not right here.
Sometimes you do expect things to get easier when you pay more for drivers, but this isn't necessarily the case. As Joachim pointed out, soft domes going through controlled breakup helps to maintain their frequency response high up in frequency, this also helps maintain the off axis response. Metal dome tweeters usually come with a phase shield that helps to correct for these problems. The Scan BE domes and the SEAS diamond don't have phase shields so the off axis falls faster then your standard soft dome.
The same can be true of woofers too, where the cheap driver has a high inductance. This higher inductance causes the top end to droop slightly and it can make the cheaper driver seem easier to work with as it helps to keep the response flat and to lessen the visual impact of any issues at breakup. This is why it isn't uncommon to see very expensive drivers, with their super low inductance motors, having rising responses as frequency increases. You could say that it's a lot easier to design a cheap driver then it is to design an expensive one, because the expectations are high and the driver will be pulled to bits by the DIY community, you really do have to make sure that everything is correctly designed. It isn't a surprise that the Satori took a long time to develop when you see how well behaved the cone is, how flat it's on axis, along with the very low inductance motor.
Now the new Scan BE dome is a bit of an enigma, if scan had chosen to really shape the larger front plate into a proper wave-guide, rather then the very shallow affair they chose, then this would have helped significantly in maintaining its off axis response (just like in the SEAS DXT), whilst making the integration and directivity match to woofers even easier.
The same can be true of woofers too, where the cheap driver has a high inductance. This higher inductance causes the top end to droop slightly and it can make the cheaper driver seem easier to work with as it helps to keep the response flat and to lessen the visual impact of any issues at breakup. This is why it isn't uncommon to see very expensive drivers, with their super low inductance motors, having rising responses as frequency increases. You could say that it's a lot easier to design a cheap driver then it is to design an expensive one, because the expectations are high and the driver will be pulled to bits by the DIY community, you really do have to make sure that everything is correctly designed. It isn't a surprise that the Satori took a long time to develop when you see how well behaved the cone is, how flat it's on axis, along with the very low inductance motor.
Now the new Scan BE dome is a bit of an enigma, if scan had chosen to really shape the larger front plate into a proper wave-guide, rather then the very shallow affair they chose, then this would have helped significantly in maintaining its off axis response (just like in the SEAS DXT), whilst making the integration and directivity match to woofers even easier.
No that isn't so bad, it was a good design choice to keep the magnet ferrite imo as neo would only raised the price unnecessarily.
Yes, i wanted to talk about the possibility of a phase plate too to extend the range of a hard dome. SB makes a hard dome too that has a phase plate and the dome is shaped in a way to stiffen it a bit. I think the idea came because one of the designers of the old Scan-Seak hard dome has a father that had a car repair shop. He uses a chisel to repair bumps in the metal of a crashed car. After many years of use the top of the chisel goes into a certain shape that looks a bit like the sharper side of an egg, at least that is the story told to me.