Woofer cone exceeding Xmax (over excrusion)

[maverick101]

I am trying to a 3 way box, monitor style box, vented enclosure.

SB Acoustics SB17NRX2C35-8 6'' ( Fs 36.5 Hz, Qes=0.47, Qms=4.55, Qts=0.42)​

its rated for 50W RMS, and in Winisd, i got a 25 L @ FB 40 Hz, but after puting anything above 2W in signal, the cone excrusion is exceeding, the Xmax ie 5.5mm and from what i have read Linear excrusion is Xmax*2 and in specs sheet, its given Linear coil travel (p-p)= 11mm.
Please, can any one help how to deal with it, do i need to keep the cone excrusion under Xmax till the last end or what?

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[diyaudio]

To me the excursion looks fine. If you are designing for Fb=40Hz it means the usable range is above this frequency, so, see excursion above this frequency only. Also use a high pass filter to limit frequencies below Fb.

 

[Passive_audio_enthusiast]

Use a high pass at 40 like the other member said, or recalculate to FB-31hz. You will end up with a larger box.

 

[maverick101]

To me the excursion looks fine. If you are designing for Fb=40Hz it means the usable range is above this frequency, so, see excursion above this frequency only. Also use a high pass filter to limit frequencies below Fb.

so does that mean even withouth putting a highpass filter....driver wont be able to play signals below FB 40hz and will eventually be safe from over excursion ??

 

[diyaudio]

so does that mean even withouth putting a highpass filter....driver wont be able to play signals below FB 40hz and will eventually be safe from over excursion ??

No, its not safe to send signals below your designated low cut off frequency, which in your case is 40Hz. You need a high pass filter.

 

[keith_correa]

Sim using 10W and ~0.75 Ohms as series resistance to account for resistance of the cables, crossover and VC. Post what you get.

 

[Passive_audio_enthusiast]

so does that mean even withouth putting a highpass filter....driver wont be able to play signals below FB 40hz and will eventually be safe from over excursion ??

Driver will be able to play the signal, but it will distort easily as there isn’t enough space in the box to support the level of excursion needed to play something lower than 40hz. At low volumes this should be fine, but still you won’t hear the lows below 40 hz in a meaningful way with that box. So, best case is build a high pass filter or use a digital high pass before the subwoofer amp.

 

[maverick101]

If this is the solution to put a highpass, it would be nearly impossible to find a poly capacitor of value around 600uF, and how come bookshelf speakers from brands claim to go till 50 or even 60hzs with drivers as small as 6" 5" and obviously they don't have xmax anymore than 5mm?!?