Is the Xmax a measure of the linear displacement from the neutral position of the woofer to the maximum excursion (the woofer completely up) or a measure of the linear displacement from below the neutral position (the cone completely bottomed out) to maximum excursion (the woofer completely up).
The term x-max is the linear displacement from neutral position. It is defined only as a linear workspace, but the linearity has to be defined. Normally that is height of VC minus heighy of gap /2, and in some cases + 15%. Since most drivers mostly multiplies the Le by 2 from X-max pos to X-max neg the definition of linearity is somehow less interesting. The suspension does also play an important role here. The X-max must therefore be understood as "effective workspace".
Some manufacturers (Seas is an example) gives x-max as Linear Coil Travel (p-p) wich means peak to peak. That is x-max * 2.
Aurum Cantus adds more than 15%. That may lead people to believe that they have longer excursion than they really have.
Manufacturers like TC sounds has a controlled roll off in the magnet gap that makes the x-max harder to define. They often give the x-max as the same as the x-mech-parameter.
For an underhung coil the x-max will be more difineable as you will get a collapse in BxL when exceeding the gap. The 15% add will not work well in that case.
Some manufacturers (Seas is an example) gives x-max as Linear Coil Travel (p-p) wich means peak to peak. That is x-max * 2.
Aurum Cantus adds more than 15%. That may lead people to believe that they have longer excursion than they really have.
Manufacturers like TC sounds has a controlled roll off in the magnet gap that makes the x-max harder to define. They often give the x-max as the same as the x-mech-parameter.
For an underhung coil the x-max will be more difineable as you will get a collapse in BxL when exceeding the gap. The 15% add will not work well in that case.
Jason:
It should be neutral position to the max, either way. There is a happily growing trend for manufacturers to do it that way, and now most do.
For a long time, and even still now, cheaper manufacturers try to cheat and list the travel all the way from the back to the front maximum. That way is called peak-to-peak excursion. Most good manufacturers, however, list it the right way.
Seas seems to be something of an exception, but at least they tell you it is peak-to-peak, so you can cut the figure in half for comparison purposes.
Just to restate the formula above
Xmax = (length of voice coil-length of voice coil gap)/2.
So a speaker with a 25mm voice coil and a 7 mm gap will have:
Xmax = (25-7)/2 = (18)/2 = 9mm.
As Snickers stated previously, some testing methods add another 15% on to this, but that is not a big difference- it adds less perhaps 1 dB to your total SPL.
It should be neutral position to the max, either way. There is a happily growing trend for manufacturers to do it that way, and now most do.
For a long time, and even still now, cheaper manufacturers try to cheat and list the travel all the way from the back to the front maximum. That way is called peak-to-peak excursion. Most good manufacturers, however, list it the right way.
Seas seems to be something of an exception, but at least they tell you it is peak-to-peak, so you can cut the figure in half for comparison purposes.
Just to restate the formula above
Xmax = (length of voice coil-length of voice coil gap)/2.
So a speaker with a 25mm voice coil and a 7 mm gap will have:
Xmax = (25-7)/2 = (18)/2 = 9mm.
As Snickers stated previously, some testing methods add another 15% on to this, but that is not a big difference- it adds less perhaps 1 dB to your total SPL.
Incidentally, the two charts listed here give you the bass SPL, at all bass frequencies, for a given volume of air moved.
The volume of air moved is your maximum excursion times your cone area. The Xmax used in this chart is the correct one-fromneutral position to the max travel in front. In other words, not peak-to-peak.
The chart is given in both normal and metric measurements.
This chart is taken from an article by Richard Small, of Thiele-Small fame, from the Journal Of The Audio Engineering Society.
http://www.diyaudio.com/forums/showthread.php?threadid=5668&highlight=
By the way, all the Thiele-Small papers, from which this chart is taken, are available for download here:
http://www.richie00boy.pwp.blueyonder.co.uk/papers/index.htm
Richie00boy generously donated the webspace to make them available to the diyAudio community.
The volume of air moved is your maximum excursion times your cone area. The Xmax used in this chart is the correct one-fromneutral position to the max travel in front. In other words, not peak-to-peak.
The chart is given in both normal and metric measurements.
This chart is taken from an article by Richard Small, of Thiele-Small fame, from the Journal Of The Audio Engineering Society.
http://www.diyaudio.com/forums/showthread.php?threadid=5668&highlight=
By the way, all the Thiele-Small papers, from which this chart is taken, are available for download here:
http://www.richie00boy.pwp.blueyonder.co.uk/papers/index.htm
Richie00boy generously donated the webspace to make them available to the diyAudio community.
You caught that, did you? I figured I could sneak that one by.
Well, it's normal measurements for the guy who posted it, who is me. If someone from Norway posted it, it becomes normal measurements and inches.
Actually, the chart from Small's article is in metric only . The only people in America who have any familiarity with the metric system are engineers, scientists or people who work in technical fields. I, like most people, do not fit any of those descriptions.
When I first came on to this website, I found I had great, great difficulty dealing with metric, which I never had to do in my entire life. I assumed others did as well, so I just computed the English equivalents and put them onto the chart using MSPaint.
There are still manufacturers who give their cone area, etc. in inches, so it works out well to have the chart in both systems.
The decision as to which is "normal" was pure editorializing on my part.
Well, it's normal measurements for the guy who posted it, who is me. If someone from Norway posted it, it becomes normal measurements and inches.
Actually, the chart from Small's article is in metric only . The only people in America who have any familiarity with the metric system are engineers, scientists or people who work in technical fields. I, like most people, do not fit any of those descriptions.
When I first came on to this website, I found I had great, great difficulty dealing with metric, which I never had to do in my entire life. I assumed others did as well, so I just computed the English equivalents and put them onto the chart using MSPaint.
There are still manufacturers who give their cone area, etc. in inches, so it works out well to have the chart in both systems.
The decision as to which is "normal" was pure editorializing on my part.
I just had to
I generally have problems dealing with square and cubic inches/feet. Not that there is any problem to recalculate them, but for me it is clearly easier to deal with the metric system when I am dealing with known sizes.
But what suprises me is that you still use both decimal and "7 3/16 inches".
Does USA try to adopt to the metric system at all?
I generally have problems dealing with square and cubic inches/feet. Not that there is any problem to recalculate them, but for me it is clearly easier to deal with the metric system when I am dealing with known sizes.
But what suprises me is that you still use both decimal and "7 3/16 inches".
Does USA try to adopt to the metric system at all?
Actually, I see Peerless and other manufacturers like Focal calling their speakers 10 inchers, or rating 7" speakers as 7Nxxxx, etc. So I presumed there was some familiarity with inches, etc. On the other hand, I gave box volume advice to a member from Scandinavia, and he went way off using feet and inches. So I guess that familiarity is limited.
Back in the seventies, there was much brouhaha made about how we are all going to go maetric. News magazine articles were dealing with the economic impact of redoing all the machine tools in metric, Celsius temps were put on those big time & temperature signs outside banks, etc. It really was a big story.
Thirty years later? A complete fizzle. People know what a liter is because that is how soft drinks are bottled these days. Outside of that, unless they are in a technical field, the average American has no idea of kilometers, centimeters, degrees Celsius, or anything like it.
Snickers-is said:
Back in the seventies, there was much brouhaha made about how we are all going to go maetric. News magazine articles were dealing with the economic impact of redoing all the machine tools in metric, Celsius temps were put on those big time & temperature signs outside banks, etc. It really was a big story.
Thirty years later? A complete fizzle. People know what a liter is because that is how soft drinks are bottled these days. Outside of that, unless they are in a technical field, the average American has no idea of kilometers, centimeters, degrees Celsius, or anything like it.
Hi,
OOPS
someone just confused System International (SI) method of measurement with metric.
Scientists, even in USA, use SI units as far as I know.
Continental Europe mostly uses metric and the UK supposedly went over to metric in 1975.
All UK schools teach SI in the sciences. However many teachers only meet alledged metric via their contact with the scientists and mistakenly believe they are teaching metric by using cm.
Metric uses metre for linear measurement and all smaller/larger denominations must rise or fall in multiples of 1000. eg T, G, M, k, m, u, p, n, f. plus a few others I've missed. Note the use of lower case k is the exception for greater than 1 multiplier. The electronics specialists among will instantly recognise these multipliers.
Hobby horse collapsed with exhaustion
Sorry all Andrew T.
OOPS
someone just confused System International (SI) method of measurement with metric.
Scientists, even in USA, use SI units as far as I know.
Continental Europe mostly uses metric and the UK supposedly went over to metric in 1975.
All UK schools teach SI in the sciences. However many teachers only meet alledged metric via their contact with the scientists and mistakenly believe they are teaching metric by using cm.
Metric uses metre for linear measurement and all smaller/larger denominations must rise or fall in multiples of 1000. eg T, G, M, k, m, u, p, n, f. plus a few others I've missed. Note the use of lower case k is the exception for greater than 1 multiplier. The electronics specialists among will instantly recognise these multipliers.
Hobby horse collapsed with exhaustion
Sorry all Andrew T.
And what can happen when it all goes wrong...
http://edition.cnn.com/TECH/space/9909/30/mars.metric.02/
http://edition.cnn.com/TECH/space/9909/30/mars.metric.02/
Snickers-is said:In Norway one liter is defined as 100centi liters, but one half liter (of beer) is defined as somewhere between 25 and 40 centiliters.
Not only that , but when they made the beer mugs smaller,
( to make us drink less beer, of course
)they compensated by INCREASING the price!
cheers
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.