Xmax is the 0 to peak excursion that the drivers voice coil and cone can move and still be in the linear part of the magnetic field. If the driver starts to move past Xmax, distortion starts to go up very quickly. For this driver, that number is 1.8mm, not 2.5mm. Xmax for an overhung driver is defined as =(voice coil winding height(10.7mm)-top plate thickness(7.1))/2. I don't know if this is a rounding error or JBL is coming up with 2.5mm because that corresponds to 10% THD under acoustic measurements (this is roughly the THD level that is supposed to predict).
Maximum excursion before damage is the maximum voice coil and cone motion before something hits something else. Usually this is the voice coil former hitting the back plate or the spider hitting the top plate. If either of these happens, the driver can possibly be broken from just one impact (unlikely). 3/4 peak to peak means that the driver can move back and forth a total of 3/4". This is 19mm. 0 to peak (the same scale as Xmax) the driver can move 9.5mm before damage. If you use an 18dB/octave filter at 90Hz, you will never bottom out (mechanically damage) this driver. Steepening the crossover beyond 12dB/octave will do nothing to decrease the driver excursion. You definitely don't want to add any passive crossover parts if you don't have to.
From those parameters, BL is really 12.28.
A 3" port will be plenty large for this driver.
What is the application for this driver?
Maximum excursion before damage is the maximum voice coil and cone motion before something hits something else. Usually this is the voice coil former hitting the back plate or the spider hitting the top plate. If either of these happens, the driver can possibly be broken from just one impact (unlikely). 3/4 peak to peak means that the driver can move back and forth a total of 3/4". This is 19mm. 0 to peak (the same scale as Xmax) the driver can move 9.5mm before damage. If you use an 18dB/octave filter at 90Hz, you will never bottom out (mechanically damage) this driver. Steepening the crossover beyond 12dB/octave will do nothing to decrease the driver excursion. You definitely don't want to add any passive crossover parts if you don't have to.
From those parameters, BL is really 12.28.
A 3" port will be plenty large for this driver.
What is the application for this driver?
These are going to be used in a car. Others have used with great success in cars before and in particular success with horns. In my experience I have not heard of them being used ported but either sealed or AP. I thought with porting I could get greater efficiency while also protecting the speaker a little more.
Jack Hidley said:
Jack isn't the above formula is just a rough start, knowing nothing else about the magnetic circuit. Isn't it really defined from Bl curves, meas. from rest position to the 70% levels from max, by looking at the actual measured Bl curves. Mostly can be non-symetrical due to the suspension and other things.
I'm really not sure about the audibility of lower mid bass sound from the ports will be Hi-Quality. He could exit the port in front or in the rear, which may throw that part of the response away.
Robh3606 said:Why are you trying to run them that low??
Rob
As the OP said this is used a midrange and has been advised to use them in closed box or possibly OB. He is trying to use them with an existing fixed 90 Hz Xover.
'This isn't for SPL. I am just trying to get dynamic sound, not SPL. I am 51 years old and I am not trying to impress the kids down the street.'
That's good. It looks OK in Bass Box for .5cubic Ft. If you limit your power input to about 100watts you will be fine as far as any x-max issues. That's plenty loud at over 110db for a single driver.
Rob
That's good. It looks OK in Bass Box for .5cubic Ft. If you limit your power input to about 100watts you will be fine as far as any x-max issues. That's plenty loud at over 110db for a single driver.
Rob
Attachments
Thanks again.
RobH3606 - From looking at your chart it looks like you tuned the box to 83.13 Hz with a .5 cu ft box, 3" port 2.5" long. When I run the same numbers in WinSLD I get a 3" port that is 3.2" long. Why the difference. Did you tune the box that low for added protection from over travel?
Infinia - Why did you write this, 'I'm really not sure about the audibility of lower mid bass sound from the ports will be Hi-Quality. He could exit the port in front or in the rear, which may throw that part of the response away.'
What is the meaning of 'Maximum excursion before damage' mean?
And why doesn't it correlate to xmax?
RobH3606 - From looking at your chart it looks like you tuned the box to 83.13 Hz with a .5 cu ft box, 3" port 2.5" long. When I run the same numbers in WinSLD I get a 3" port that is 3.2" long. Why the difference. Did you tune the box that low for added protection from over travel?
Infinia - Why did you write this, 'I'm really not sure about the audibility of lower mid bass sound from the ports will be Hi-Quality. He could exit the port in front or in the rear, which may throw that part of the response away.'
What is the meaning of 'Maximum excursion before damage' mean?
And why doesn't it correlate to xmax?
"What is the meaning of 'Maximum excursion before damage' mean? And why doesn't it correlate to xmax?"
X max is determined by the gap and coil dimensions. Maximum Excursion is always greater as that is determined by the suspension.
I can have Bass Box come out with the same solution as WinIsd by turning off options in the program. Bass Box is more accurate as you can adjust for fill as an example. Both can give you very good results.
Rob
X max is determined by the gap and coil dimensions. Maximum Excursion is always greater as that is determined by the suspension.
I can have Bass Box come out with the same solution as WinIsd by turning off options in the program. Bass Box is more accurate as you can adjust for fill as an example. Both can give you very good results.
Rob
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