I am a newbie at speaker construction, and I was thinking about starting with a sealed sub. I noticed that quite a few people go for Shiva designs, and I went to adire audio's web site and red the sealed design white paper.
I also ran some equations to see what I could come up with on my own. I noticed some striking differences in what the equations say and what Adire Audio says.
I was looking for a Qtc of around 0.6. Using a spreadsheet I found on diysubwoofers.org, I plugged in the T/S parameters for the Shiva, and calculated for a Qtc of 0.6. I compared the numbers to the Shiva white paper, and here is what I saw:
______________White Paper: _____ My calculations:
Box Volume:___88.5 liters ______ 110 liters
Anechonic F3:_30.7 Hz __________ 39.1 Hz
Anechonic F8:_20.5 Hz __________ 23 Hz
Fb:___________34.4 Hz __________ 32.3 Hz
I realize that the box volume difference is due to the use of stuffing in the white paper's designs. I thought that stuffing simply increased the apparant box size to the driver (hence the ~25% difference). Can stuffing alter the other results this much? Or is Adire fudging on their numbers?
I also ran some equations to see what I could come up with on my own. I noticed some striking differences in what the equations say and what Adire Audio says.
I was looking for a Qtc of around 0.6. Using a spreadsheet I found on diysubwoofers.org, I plugged in the T/S parameters for the Shiva, and calculated for a Qtc of 0.6. I compared the numbers to the Shiva white paper, and here is what I saw:
______________White Paper: _____ My calculations:
Box Volume:___88.5 liters ______ 110 liters
Anechonic F3:_30.7 Hz __________ 39.1 Hz
Anechonic F8:_20.5 Hz __________ 23 Hz
Fb:___________34.4 Hz __________ 32.3 Hz
I realize that the box volume difference is due to the use of stuffing in the white paper's designs. I thought that stuffing simply increased the apparant box size to the driver (hence the ~25% difference). Can stuffing alter the other results this much? Or is Adire fudging on their numbers?
Anyway, for a final Q of .6, I get the same numbers you do-not Shiva's numbers. Do you have a link to the white paper?
For what it is worth, if you make an 88 liter PORTED box and tune it to 13 Hz or so, you should get numbers somewhat near that.
Incidentally, the tuning ratio H for that ported box is .6. The tuning ration is defined as Fb/Fs. Has there been some confusion between H and Q? Just guessing.
[Edited by kelticwizard on 10-12-2001 at 11:24 PM]
For what it is worth, if you make an 88 liter PORTED box and tune it to 13 Hz or so, you should get numbers somewhat near that.
Incidentally, the tuning ratio H for that ported box is .6. The tuning ration is defined as Fb/Fs. Has there been some confusion between H and Q? Just guessing.
[Edited by kelticwizard on 10-12-2001 at 11:24 PM]
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