overlapping LPF and HPF?

[LongThrow]

I have a lpf and hpf setting on my head unit, and obviously on my amp. Would it do any damage, or degrade sound quality by overlapping say 80hz lpf on amp and 100 on the head unit?

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[Louisiana_CRX 5,000+ posts]

It can cause phase issues due too slope variation

 

[LongThrow]

I figure I could just set my amp to full range and just control my lpf with my headunit. My HU doesn't have a THRU or pass setting.