Question about excursion limits

[rpb]

How much beyond x-max can a woofer like the Dayton 15" DVC and RSS390 subs go before they risk bottoming out?

[norman]

> How much beyond x-max can a woofer like the
> Dayton 15" DVC and RSS390 subs go
> before they risk bottoming out?

not much thats why they call it "MAX"

[dB]

> How much beyond x-max can a woofer like the
> Dayton 15" DVC and RSS390 subs go
> before they risk bottoming out?

Technically, the Xmax is defined as the coil height minus the top plate thickness divided by two. Bottoming out is where the coil former hits the back plate. Topping out is where the spider hits the top of the top plate. In a good design, top out would occur first to preclude flaring the coil former and destroying the speaker.

In most cases though the surround limits the speaker from reaching top or bottom out. It's all a matter of geometry of the basket, plates and the other components. No way to relate Xmax to bottoming out really. If you can push the cone in and feel it hitting, then the driver may easily be over driven, especially with a highly compliant spider and surround.

The DVC 15 has 15mm of Xmax with what looks like a relatively small surround (compared to some others nowadays). So, it is possible that Xmax could be close to the suspension limit. Hopefully, the suspension limit won't create distortion.

But, that's why I prefer 15" and larger woofers. Compared to smaller drivers, they need to move much less to move the same amount of air.

dave

[Dirk]

> Technically, the Xmax is defined as the coil
> height minus the top plate thickness divided
> by two. Bottoming out is where the coil
> former hits the back plate. Topping out is
> where the spider hits the top of the top
> plate. In a good design, top out would occur
> first to preclude flaring the coil former
> and destroying the speaker.

> In most cases though the surround limits the
> speaker from reaching top or bottom out.
> It's all a matter of geometry of the basket,
> plates and the other components. No way to
> relate Xmax to bottoming out really. If you
> can push the cone in and feel it hitting,
> then the driver may easily be over driven,
> especially with a highly compliant spider
> and surround.

> The DVC 15 has 15mm of Xmax with what looks
> like a relatively small surround (compared
> to some others nowadays). So, it is possible
> that Xmax could be close to the suspension
> limit. Hopefully, the suspension limit won't
> create distortion.

> But, that's why I prefer 15" and larger
> woofers. Compared to smaller drivers, they
> need to move much less to move the same
> amount of air.

> dave

And I've noticed a trend in Dayton subs to have much more Xsus than Xmag. In short, if you size your amplifier correctly, the sub will start to sound like *** well before mechanical damage can occur. If the driver SOUNDS distorted, you're operating out of its linear range and all bets are off as to what happens after that. If you want a number for simulations with Unibox or something, I'd say Xmax + 15% is safe.

With the tools we have available to us these days, there should be little reason to ever run into this problem at all. Size it right from the get-go. :-D

[rpb]

> And I've noticed a trend in Dayton subs to
> have much more Xsus than Xmag. In short, if
> you size your amplifier correctly, the sub
> will start to sound like *** well before
> mechanical damage can occur. If the driver
> SOUNDS distorted, you're operating out of
> its linear range and all bets are off as to
> what happens after that. If you want a
> number for simulations with Unibox or
> something, I'd say Xmax + 15% is safe.

> With the tools we have available to us these
> days, there should be little reason to ever
> run into this problem at all. Size it right
> from the get-go. :-D

I'm running an RSS390HO sealed in a 4 cu-ft low Q design. The amp I'm currently using should put out 150w into 4 ohms. I've seen excursion that would appear be reaching 1" peak to peak while playing a loud action movie. Everything sounds very clean. I want to know how close to the limits I might be. I have a limiter on my DCX that I can set to protect the sub if needed. I also may use a plate amp rated at 275 watts into 4 ohms.

[rpb]

> I'm running an RSS390HO sealed in a 4 cu-ft
> low Q design. The amp I'm currently using
> should put out 150w into 4 ohms. I've seen
> excursion that would appear be reaching
> 1" peak to peak while playing a loud
> action movie. Everything sounds very clean.
> I want to know how close to the limits I
> might be. I have a limiter on my DCX that I
> can set to protect the sub if needed. I also
> may use a plate amp rated at 275 watts into
> 4 ohms.

The box also has a port. I'm trying it out with the port plugged.