# How would Tempest compare to an SVS Ultra

Discussion in 'Archived Threads 2001-2004' started by David Giesbrecht, Jul 29, 2001.

1. ### David Giesbrecht Second Unit

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In a 250L enclosier tuned to 16hz how would this sub compare.

2. ### Greg P Stunt Coordinator

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David,
I am a newbie at DIY but from what Ive been learning a lot of the output can be calculated by the amount of air the driver can move. Also I asume you want to put the tempest in a ported enclosure which would be comparable to each other. I believe you take the diameter sq. x the excursion. heres how I believe they would stack up.
SVS Ultra = 12 x 12(diameter) x 21mm(excursion)= 3,024
Tempest = 15 x 15(diameter) x 16.8mm(excursion)= 3,780
The SVS can outgun most 15's, but not the Tempest ( It has one of the longest throws out there of any 15). Another thing to take into consideration is usable excursion, if you could some how calculate that you would be more accurate. If I have made any errors I hope the more experienecd guys here correct me. I believe though David if you wanted to tune the tempest to 16hz you would need a little bit bigger cabinate. You can find out more at www.diysubwoofers.org. they have formulas for calculating the Vb (box volume).

3. ### Julian Data Second Unit

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If the TV 12 is like the MASS, then the Tempest would surely beat it out of output due to it's displacment. Terry C did a test on this awhile back.
As for 15" excursion, they are several with over 20mm one-way.
Displacement
(Sd) X (Xmax one way)
[Edited last by Julian Data on July 29, 2001 at 04:27 PM]

4. ### Jack Gilvey Producer

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You're on the right track, Greg, displacement is the area of the cone multiplied by the linear stroke. The area of a circle, though, is Pi(r^2). The effective cone area is not always such a simple number, as different manufacturers figure it differently based on the type and size of surround. The number you're looking for in the specs is Sd. For the Tempest, it's 779cm^2. Xmax both ways is 3.28cm. Seems to come out to about 2.6 liters.
I don't know the specifics of the SVS driver, but being that a 12" would need a lot more stroke than a Tempest to equal its linear displacement, I'd say a Tempest in 250L tuned to 18Hz or so should compare rather favorably. An excellent quality larger driver in a larger cabinet has many advantages.
You'd really have to test both to really know, though.
[Edited last by Jack Gilvey on July 29, 2001 at 04:44 PM]

5. ### Julian Data Second Unit

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Jack,
You meant 32.8mm.. correct for the Xmax p-p?
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6. ### Jack Gilvey Producer

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7. ### DanWiggins Second Unit

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What? No fathoms (0.0179765648 fathoms of linear excursion)?
Anyway, a Tempest displaces 2.55L linearly (779 cm^2, 32.8mm pp Xmax). Assuming the TV12 has the same performance capabilities as the MASS2012, then it would displace 1.84L linearly (460 cm^2, 38mm pp Xmax).
Dan Wiggins
Adire Audio

8. ### Jack Gilvey Producer

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9. ### Julian Data Second Unit

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I thought you used Xmax "one way" for displacment?
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10. ### Jack Gilvey Producer

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11. ### David Giesbrecht Second Unit

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So in other words my Tempest sonosub is going to rule!

12. ### Julian Data Second Unit

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"no substitute for displacement".
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13. ### Patrick Sun Moderator Moderator

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14. ### Julian Data Second Unit

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Actually, IMHO, a turbocharger.
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15. ### Tom Vodhanel Cinematographer

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the whole displacement analogy depends on the two motors being fine tuned and performance oriented equally. and then the motors are just a single component of the car.
So if you exactly the same cars...and you have a 396 and a 502 exactly built/tuned the same...yes,the 502 should *win*. Then again, the 396 might just make enough torque to keep the bite...while the 502 blows em off
Who wants to race a well tuned 472 caddy against a well tuned 454 vette? The caddy's got the displacement...so I guess it always wins.....on paper anyway.
TV

16. ### Jack Gilvey Producer

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I wish I understood all these car analogies.
I'm guessing the gist is that there's more to it than the driver, and that the system has to be well-tuned and constructed for superior linear displacement to be shown to advantage? I'd certainly agree.