How to set LPF on amp to exactly 70Hz?

[ghart999 10+ year member]

My Sundown 1500D has a LPF like every other amp. Normally I just use the head unit to set this, but using Alpine's Imprint, so I can't set in the head unit anymore.

LPF knob goes from 35Hz - 300 Hz. How do I know where 70Hz is?

Would I maybe play a test tone as 63Hz and then another at 80Hz and when the 80Hz tone is significantly quiter I know I found the ballpark spot? Will I need a SPL meter to notice the diff or will it be obvious enough?

Same question for Subsonic filter. Just play tones around my tuning freq and turn knob until SPL drops significantly?

Thanks all.

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[PaulD 10+ year member]

a cheap oscilloscope would be good for that.

 

[dipitydoo 10+ year member]

I would just set it using your ears. How would you know that 70hz is the best sounding xover point in your setup? 70 - 80hz is a good standing point for many systems, but its best to finalize it some listening. Test tones might be good to get a starting point, then use music to finish tuning it.

 

[350zspl 10+ year member]

about in the middle should be close

i would put in a disc you are familiar with

start at 35 hertz and raise until you get were you like the sound

 

[ghart999 10+ year member]

Thanks all.

 

[Tehgregzor 10+ year member]

300 - 35 = 265 ... 265/2 = 132.5.. so half way up is 132.5 half of that is 66.25...so a quarter of the way up is 66.25. so turn it slightly past 1/4 way and it should be right at if not really close to 70.

a better way is 70/265 = 0.2641etc... so turn it up 26%. which is what i said earlier. Yay.

 

[PaulD 10+ year member]

Teh, those knobs are not always linear so the simple math trick doesn't always work. I agree that listening is better, mine ended up at 50 Hz - wanted it lower but the midbass won't blend much lower than that