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What effect does a Qts that is slightly too high, or a Vas that is slightly too low, have on a design like the AutoTuba?
Based on a few minutes of research, Qts is basically describing the cone's "weight", for lack of a better term, and Vas is cone "stiffness".
So, if my thoughts are correct, a driver with too-high Qts will sound sloppy, and a driver with too-low Vas will sound weak.
How does BL play into any of this? Is BL unimportant in horns?
If I were to try out an 8" speaker in an AutoTuba that had the following specs:
Fs: 37Hz (within spec)
Qts: .511 (slightly high)
Vas: 4.474L (WAY low)
Is it safe to assume that this driver would not perform well at all? Despite the ~15mm xmax?

Qts has nothing to do with the cone weight. It's the product of Qes (motor strength) and Qms (suspension stiffness). High Qts drivers work best in sealed or infinite baffle cabs, not horns or ported cabs.

Bill Fitzmaurice wrote:Qts has nothing to do with the cone weight. It's the product of Qes (motor strength) and Qms (suspension stiffness). High Qts drivers work best in sealed or infinite baffle cabs, not horns or ported cabs.

Isn't BL "motor strength"? Or is it more complicated than that?
Not trying to correct, just learn.
Also, what behavior would you anticipate from the (slightly) hypothetical driver in the OP?

Ryan Sober wrote: Isn't BL "motor strength"? Or is it more complicated than that?
Not trying to correct, just learn.
Also, what behavior would you anticipate from the (slightly) hypothetical driver in the OP?

BL takes into consideration both Qes and impedance among other factors. Too high a Qes/Qts in a horn results in a loss of low frequency extension.

Bill Fitzmaurice wrote: BL takes into consideration both Qes and impedance among other factors. Too high a Qes/Qts in a horn results in a loss of low frequency extension.

Ahh, that makes sense.
So, what about low Vas? What effect does that have on a horn-loaded system?
Thanks for humoring me, Bill.

Ryan Sober wrote: So, what about low Vas? What effect does that have on a horn-loaded system?

It also results in less low frequency extension.