The surround is the rubber half-roll connecting the cone and the basket. Which resonance frequencies do you get free air and in the test box?
alright, for the 10"
Fs (free air)=29.4Hz
Fs (test box)=24.9Hz
New t/s with accurate diameter:
Fs = 24.89 Hz
Re = 6.05 ohms[dc]
Le = 1521.84 uH
L2 = 9458.86 uH
R2 = 25.60 ohms
Qt = 0.18
Qes = 0.21
Qms = 1.41
Mms = 535.80 grams
Rms = 59.340157 kg/s
Cms = 0.000076 m/N
Vas = 13.74 liters
Sd= 358.00 cm^2
Bl = 49.089962 Tm
ETA = 0.10 %
Lp(2.83V/1m) = 83.18 dB
Closed Box Method:
Box volume = 25.81 liters
Diameter= 21.35 cm
Note: the cone does seem like it could weigh more then typical as it is pretty thick.
12cm Mid
Fs(free air) = 81 Hz
Fs(test box) = 92.7 Hz
t/s with accurate diameter:
Fs = 80.92 Hz
Re = 5.40 ohms[dc]
Le = 219.34 uH
L2 = 779.95 uH
R2 = 3.43 ohms
Qt = 1.16
Qes = 1.74
Qms = 3.46
Mms = 4.83 grams
Rms = 0.709828 kg/s
Cms = 0.000801 m/N
Vas = 5.90 liters
Sd= 72.38 cm^2
Bl = 2.757947 Tm
ETA = 0.17 %
Lp(2.83V/1m) = 86.18 dB
Closed Box Method:
Box volume = 13.37 liters
Diameter= 9.60 cm
Thank you for your help so far. It is greatly appreciated.
Fs (free air)=29.4Hz
Fs (test box)=24.9Hz
New t/s with accurate diameter:
Fs = 24.89 Hz
Re = 6.05 ohms[dc]
Le = 1521.84 uH
L2 = 9458.86 uH
R2 = 25.60 ohms
Qt = 0.18
Qes = 0.21
Qms = 1.41
Mms = 535.80 grams
Rms = 59.340157 kg/s
Cms = 0.000076 m/N
Vas = 13.74 liters
Sd= 358.00 cm^2
Bl = 49.089962 Tm
ETA = 0.10 %
Lp(2.83V/1m) = 83.18 dB
Closed Box Method:
Box volume = 25.81 liters
Diameter= 21.35 cm
Note: the cone does seem like it could weigh more then typical as it is pretty thick.
12cm Mid
Fs(free air) = 81 Hz
Fs(test box) = 92.7 Hz
t/s with accurate diameter:
Fs = 80.92 Hz
Re = 5.40 ohms[dc]
Le = 219.34 uH
L2 = 779.95 uH
R2 = 3.43 ohms
Qt = 1.16
Qes = 1.74
Qms = 3.46
Mms = 4.83 grams
Rms = 0.709828 kg/s
Cms = 0.000801 m/N
Vas = 5.90 liters
Sd= 72.38 cm^2
Bl = 2.757947 Tm
ETA = 0.17 %
Lp(2.83V/1m) = 86.18 dB
Closed Box Method:
Box volume = 13.37 liters
Diameter= 9.60 cm
Thank you for your help so far. It is greatly appreciated.
the resonance in the test box can not be lower than in free-air, it is impossible. Resonant frequency only rises when placed in test boxes of any size. That error is likely throwing everything off, such as the the Mms, BL, etc for the woofer.
I don't know what to say, I just did the test several times and always get the same fs and the one in the test box is always lower.
then there is something wrong with the test/test gear/test setup in one way or another.
Can you do an impedance sweep in free-air and in the test box?
Seems to be backwards, as Fs always rises in a box. I can't say for sure exactly what is wrong since I don't have that software/hardware you are using, but there is something definitely wrong somewhere. Perhaps try reinstalling the software?
One thing I have noticed is every time I get a slightly different graph, It is the exact same shape just translated up or down. Another strange thing is I Limp does not care which one is the free-air and which one is the test box, I can switch them and get the same t/s parameters.
Strange is also the calibration. The driver is 6 ohm, but the curve is at 16 ohm. Verify the setup using a 10 ohm resistor instead of a loudspeaker as load. The impedance should be a flat line at 10 ohm.
There seems to be a standing wave in the test box causing an additional resonance peak at 100 Hz. Is the cabinet long and small? This could distort the measurement completely.
There seems to be a standing wave in the test box causing an additional resonance peak at 100 Hz. Is the cabinet long and small? This could distort the measurement completely.
The 10" driver is nominal 8 ohm, 6.05 Ohms DC. On some tests it is around 16 and others it is around the proper 8 Ohms. I just did another test trying to position the driver in the exact same location in the room, and got around 8 ohms, but the t/s parameters were crazy.
One thing is I am just using my headphone jack out so it is not near 1VRMS, would this be a problem. The line out on my computer is even smaller.
I tried what you suggested except with a 100 Ohm resistor because that is what I had and it was as flat as can be expected from a 5% tolerance resistor.
I'm probably just making some silly small dumb mistake, I'll try again with a fresh brain tomorrow.
One thing is I am just using my headphone jack out so it is not near 1VRMS, would this be a problem. The line out on my computer is even smaller.
I tried what you suggested except with a 100 Ohm resistor because that is what I had and it was as flat as can be expected from a 5% tolerance resistor.
I'm probably just making some silly small dumb mistake, I'll try again with a fresh brain tomorrow.
Alright this is what I did:
For the 10":
First I redid my free air impedance measurement, by hanging the driver from the ceiling instead of putting it on the table.
I made sure my enclosure was completely sealed by lining all the edges, and corners with playdough, (primitive, but effective). I then notice there were to "humps" one fs that I always got at 24 Hz and another one at 72 Hz. Just to see what I got I used the 72 as my Fs for my calculations, and got reasonable t/s parameters. I then performed two tests (one with 23 grams, and another with 49 grams) using the added mass method and got very similar results to the closed box using fs of 72 Hz. I then averaged all three (closed box, added mass (23 g) and added mass (49 g)) of the t/s parameters.
The ending results for the 10" Sub:
Fs = 29.78 Hz
Re = 6.05 ohms [dc]
Le = 2390.01 uH
L2 = 5515.85 uH
R2 = 9.45 ohms
Qt = 0.36
Qes = 0.39
Qms = 4.39
Mms = 81.65333333 grams
Rms = 3.480623333 kg/s
Cms = 0.00035 m/N
Vas = 54.56333333 liters
Sd = 333.29 cm^2
Bl = 15.441371 Tm
ETA = 0.356666667%
Lp = 88.85 dB
12cm Mid:
I did the same thing except with 12 grams and 23 grams because it is a smaller driver.
Ending result after averages.
Fs = 80.01 Hz
Re = 5.40 ohms[dc]
Le = 329.13 uH
L2 = 2381.11 uH
R2 = 1.68
Qt = 1.28
Qes = 1.85
Qms = 4.16
Mms = 6.573333 grams
Rms = 0.794003 kg/s
Cms = 0.000621 m/N
Vas = 3.3 liters
Sd = 61.51 cm^2
Bl = 3.09592
ETA = 0.086667
Lp = 83.18333
My tweeter has a completely closed back, does this mean I can put it in a sealed enclosure of any size?
For the 10":
First I redid my free air impedance measurement, by hanging the driver from the ceiling instead of putting it on the table.
I made sure my enclosure was completely sealed by lining all the edges, and corners with playdough, (primitive, but effective). I then notice there were to "humps" one fs that I always got at 24 Hz and another one at 72 Hz. Just to see what I got I used the 72 as my Fs for my calculations, and got reasonable t/s parameters. I then performed two tests (one with 23 grams, and another with 49 grams) using the added mass method and got very similar results to the closed box using fs of 72 Hz. I then averaged all three (closed box, added mass (23 g) and added mass (49 g)) of the t/s parameters.
The ending results for the 10" Sub:
Fs = 29.78 Hz
Re = 6.05 ohms [dc]
Le = 2390.01 uH
L2 = 5515.85 uH
R2 = 9.45 ohms
Qt = 0.36
Qes = 0.39
Qms = 4.39
Mms = 81.65333333 grams
Rms = 3.480623333 kg/s
Cms = 0.00035 m/N
Vas = 54.56333333 liters
Sd = 333.29 cm^2
Bl = 15.441371 Tm
ETA = 0.356666667%
Lp = 88.85 dB
12cm Mid:
I did the same thing except with 12 grams and 23 grams because it is a smaller driver.
Ending result after averages.
Fs = 80.01 Hz
Re = 5.40 ohms[dc]
Le = 329.13 uH
L2 = 2381.11 uH
R2 = 1.68
Qt = 1.28
Qes = 1.85
Qms = 4.16
Mms = 6.573333 grams
Rms = 0.794003 kg/s
Cms = 0.000621 m/N
Vas = 3.3 liters
Sd = 61.51 cm^2
Bl = 3.09592
ETA = 0.086667
Lp = 83.18333
My tweeter has a completely closed back, does this mean I can put it in a sealed enclosure of any size?
Why did you do this exactly? (Specifically, the averaging of different sets of parameters). Is this something that software tells you to do? I ask because just because the results look reasonable, doesn't make them accurate.
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To get the most accurate results, I realize I might run into a little bit of trouble because then they will not match up perfectly.
Really I'm asking because you say you used an impedance peak of 72Hz, rather than the true driver Fs, to get one set of "T/S" parameters, when this is not correct (unless I missunderstood you). IF you have wildly varying sets of T/S parameters, then your end results will be off. I would only average out parameters if they came out with a very low variance (or std deviation). In other words, if one Qts comes out to 0.25, and another test reveals 0.50, that does NOT make the actual Qts 0.38. But if you got 0.30, 0.32, 0.29, 0.30, then an average of these closely grouped values would be accurate, IMO.
My three sets of t/s parameters were very close. When I tested my 10" in a test box, there were two impedance peaks, one was below free air resonance, and gave very impractical t/s parameters, the other gave pratical t/s parameters, that very closely lined up with the t/s parameters from two tests, using the added mass method.
The only values that changed were: Mms, Cms, Rms, Vas, ETA, and LP.
On the 12 Cm I will probably rule out the closed box because that seems extranous.
The only values that changed were: Mms, Cms, Rms, Vas, ETA, and LP.
On the 12 Cm I will probably rule out the closed box because that seems extranous.
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Well it's your gear, just trying to make sense of it all. I just use my Dayton DATS and have all parameters in less than 2min, hehe.
Yup, something called the speaker. There will always be standing waves in rectangular prisms with parallel walls if no measures are taken to suppress them, BUT unless the distance between the walls is 1.74m or longer, you won't get standing waves less than 100Hz.
The modes of vibration of a standing wave are given by
f = k*c/(2*l), where c= speed of sound in m/s, l= distance between walls in m, k= integer values 1,2,3,....
If one dimension is say, 0.30m, the first mode is 1*348/(2*0.3)=580 Hz. The subsequently larger k values only lead to higher and higher standing wave frequencies.
I am a NOOB, I do not know why there is a impedence peak below the free air resonance, but by using the second peak I get very, very close parameters to accurate testing using the added mass method.
You're making a fundamental error in your ways of thinking. If you make an impedance sweep, the free air resonance is the one and only impedance peak, period. Anything else (in terms of impedance peaks) after you put it in a box, has to be some kind of artifact produced artificially. If you get two impedance peaks in free-air, then it has to be a test system/calibration error. Or the driver has some kind of weird physical defect I've never heard of before.
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