Power Handling - SB17 v/s ER18 CA18

[percy]

While modeling the following drivers in WinISD Pro Alpha the SB17 comes out quiet weak in the power handling area. The chart shows a wide deep crater unlike other drivers that have just a narrow shallow dip. All these were modeled as ported enclosures.

Seas CA18RNX/LY
Seas ER18RNX
SB Acoustics SB17

Can anyone confirm this ? Or did I do something wrong ? I am unable to post any images right now but wanted to get this started.

Would be nice to cross check this with some other software as well. What other software is able to show a power handling curve ? I tried Unibox but it seemed like it doesn't have a direct equivalent for the power curve ?

Thanks!

 

[percy]

ok lets see if a couple of pictures help explain. Here are the Max Power and Cone Excursion charts -
Green = SB17
Yellow = ER18
Reddish Marron - CA18RNX

See how the SB17 bottoms out ?

Cone excursion is for 25W.

 

[gfiandy]

Hi,

At least part of the reason for this is the port tunning and box size. As you go lower in frequency with the port tunning the driveritself has to provide more of the low frequency range. This will significantly increase the excursion.

As you increase box size it will provide less of an air spring and hence the excusrion will rise, you will also get more bass extension but this is only possible through greater excursion so you limit the power response.

Regards,
Andrew

 

[pop4richard]

Hi, Try 11 litres and 52 Hz tuning which gives an f3 of 58Hz. Heavy box damping will reduce the excursion a little, or a slightly larger box with less power for a flatter response curve with lower maximum spl.

The SB17 has a max power rating of 60w also.

 

[percy]

yes I realize the implications of box size and port tuning on power handling, but what I really wanted to do was affirm that the SB17 is weak in the power handling area. Anyone disagree ?

Even if you dont play very loud the cone excursion is uncomfortably close to the max limit, dont you think ?

 

[gfiandy]

Since you have not compared like with like that is not an inference that can be made from your data.

More excursion is required in the box and tuning you have set up, so the drive unit show excursion limited power response.

Unless you compare the drivers in a situation where thay are trying to achive the same bandwidth in approximately the same way you can't make a valid determination of the relative power handling. It might be less power full at low frequency and it might not.

Regards,
Andrew

 

[gfiandy]

As an example I have reworked the driver in a box that won't limit its bass response. This box is not a good alignment just a demonstration that your graphs don't support your statement.

I have also done a simulation of the driver in box of approx equivalent size to the other drivers. Here you can see that whilst is still not as high a power handling as the others it is much better. This response now has abit of a peak in it which if it was used to reduce the baffle step requirement would further improve the relative bass performances of the drivers. (So you need to incorporate the frequency response information to make a valid comparison)

Sorry this is so pedantic, but I have an aversion to decisions made on poor data.

However having taken a deeper look at the drivers I think your gut feeling is right. I think a valid statement would be this driver has a smaller cone area and a lower xmax so it will not have as great low frequency power handling as the other drivers which are larger and have greater xmax.

Regards,
Andrew