pinkmouse said:
Hmm . . . I did that.
OMG
it worked. Maybe I did not do that 
Got about 90 Hz for the fs though.
It does seems to be 4 ohm according to the graph(s), but measures a DCR of about 5.5 with my voltimeter. Is that possible?
I keep getting a message that says "Invalid Frequency Range - Does not include full impedance peak" when I try to "estimate parameters."
pinkmouse said:
After seeing/reading the manual, I might assume that the above is some of that dry british humor I've heard about.
I read about measuring impedance in free air and with added mass, then measured those two. The specs I got did not seem to be very accurate, here's a pic .
Maybe it did not account for the wire inductance or capacitance correctly. Qes seems to be off by the most 1.05 instead of .43 from the specs on the page given before, http://www.mindspring.com/~audiolab/peerlspc.htm
I did not calibrate my sound card also.
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A couple things, you said you read 5.5 ohms using your voltmeter. Is this a digital voltmeter, and what do you read in terms of resistance when you just short circuit the leads of the voltmeter? Usually you will read something like 1 ohms by just shorting the measurement cable leads. So you need to substract that amount from what you read when you measure the driver's DCR. I think there is something wrong there. From your picture of SW results it says you entered the Re value. Try also extracting the T/S parameters letting SW decide the Re value, and compare this value to what you measured with substracting the lead resistances. I would guess they would be close, and it would be somewhere or less than 4 ohms. I think you also said the model number on the drivers say it is 4 ohm model.
Another thing, I think you have the paper cone version, not poly. I think they coat the paper cones with a special coating that make it look like poly from outside, but as you said the back of the cone looks paper.
It is a good thing that you are measuring the T/S params, it is not unusual that production specs are off from published specs. But such Qe value makes me think that there is something wrong with the Re value entered.
Another thing, I think you have the paper cone version, not poly. I think they coat the paper cones with a special coating that make it look like poly from outside, but as you said the back of the cone looks paper.
It is a good thing that you are measuring the T/S params, it is not unusual that production specs are off from published specs. But such Qe value makes me think that there is something wrong with the Re value entered.
As a quick and dirty check on the Qts, (which is generally pretty close to the Qes, as well), you might try using either Speaker Workshop or Audiotester to do a quick frequency response test, especially below 300 Hz.
The SPL response at Fs, in relation to the midpoint, for Qts is:
Qts = 20 Log Qts
So at Qts = 0.7, the response is:
20 Log 0.7 = -3.1 dB down from the midpoint.
I did some quick math-you can extrapolate whatever your SPL is at Fs.
Qts = 0.5 Response at Fs = -6 dB
Qts = 0.4 Response at Fs = -8 db
Qts = 0.35 Response at Fs = -9.1 dB
Qts = 0.3 Response at Fs = -10.5 dB
Qts = 0.25 Response at Fs = -12 dB
It's a quick way to either check your Qts measurements, or even to use to find them.
Note-some woofers do have a little bit of an output resonance at Fs. So if there seems to be bump in the SPL response around Fs, just visualize where the rolloff curve is leading, and estimate from there. It usually is pretty effective.
The SPL response at Fs, in relation to the midpoint, for Qts is:
Qts = 20 Log Qts
So at Qts = 0.7, the response is:
20 Log 0.7 = -3.1 dB down from the midpoint.
I did some quick math-you can extrapolate whatever your SPL is at Fs.
Qts = 0.5 Response at Fs = -6 dB
Qts = 0.4 Response at Fs = -8 db
Qts = 0.35 Response at Fs = -9.1 dB
Qts = 0.3 Response at Fs = -10.5 dB
Qts = 0.25 Response at Fs = -12 dB
It's a quick way to either check your Qts measurements, or even to use to find them.
Note-some woofers do have a little bit of an output resonance at Fs. So if there seems to be bump in the SPL response around Fs, just visualize where the rolloff curve is leading, and estimate from there. It usually is pretty effective.
You guys are going to like this, I can feel it
The specs for the woofers don't match each other they also don't match the specs on this page http://www.mindspring.com/~audiolab/peerlspc.htm
They should match these specs somewhat fot the SKO130, I think, and each other.
I did the measurements a lot of time with two different sound blaster cards and the woofers still come out like this. So I guess my question is - what does this mean?
The specs for the woofers don't match each other they also don't match the specs on this page http://www.mindspring.com/~audiolab/peerlspc.htm
They should match these specs somewhat fot the SKO130, I think, and each other.
I did the measurements a lot of time with two different sound blaster cards and the woofers still come out like this. So I guess my question is - what does this mean?
Attachments
It looks like you have SKO130's. IMO the T/S params on the left of your picture matches very well with http://www.mindspring.com/~audiolab/peerlspc.htm.
The difference between your two units may not be that important when you model the box. The unit on the right has higher Fs, but at the same time a lower Vas, and higher Qts. These differences may cancel each other in a box. For example, if I remember correctly, for a sealed box if the ratio of Fs/Qts remains same, box volume stays same to give same box alignment. So I would suggest you to model the box with the T/S parameters that are on the left of your picture. Then change the driver parameters to the right ones, and look what happens to SPL using the same box. It may turn out the end result will be very similar between the two units.
I haven't used those drivers, but I had read that they have very nice midrange.
The difference between your two units may not be that important when you model the box. The unit on the right has higher Fs, but at the same time a lower Vas, and higher Qts. These differences may cancel each other in a box. For example, if I remember correctly, for a sealed box if the ratio of Fs/Qts remains same, box volume stays same to give same box alignment. So I would suggest you to model the box with the T/S parameters that are on the left of your picture. Then change the driver parameters to the right ones, and look what happens to SPL using the same box. It may turn out the end result will be very similar between the two units.
I haven't used those drivers, but I had read that they have very nice midrange.
I would almost rather use the published specs cause I don't think speaker workshop has calculated the right Qes for these woofers.
My resistor is suppose to be 10 ohm 1 or 2 % tolerance, but I could not measure it accurately. Also I used the added mass method and I estimated that a pennies plus the tape weigh 5.1 grams, but I'm not too sure. Also I could not calibrate my sound card.
My resistor is suppose to be 10 ohm 1 or 2 % tolerance, but I could not measure it accurately. Also I used the added mass method and I estimated that a pennies plus the tape weigh 5.1 grams, but I'm not too sure. Also I could not calibrate my sound card.
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