A few questions on my setup concerning high pass filter and gain

[RoachForLife 10+ year member]

Hey gang. So I finally tuned my sub amp yesterday after repairing my JL subs that the foam was messed up. Everything is generally in order but it prompted me to examine some of my setup. I had a few questions. (Setup below)

Questions

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1. Right now I have both my sub amp and front amps set to crossover at the same freq (80Hz), this is the way it is generally done so there is nothing missing correct?

2. I had read that 80Hz was a good crossover point, true?

3. Whats odd is that my HP filter is on and set to 80Hz, however when I grabbed a 50Hz test tone and played it at 3/4 volume, there was sound coming out of my front speakers. Does this mean that the amp is not working properly for the HP Filter?

4. I have an option to do a HP filter on my HU (off, 80hz, 120hz, and 160hz). If I set my HU to 80hz I noticed the sound in the fronts went away (when doing the 50hz test tone at 3/4 volume). What does this mean? Should I use the HU instead of the amp?

5. If I did decide to use the HU for the HP and not the amp, I would think I would turn it to off on the amp, however that seemed to make sound from the speakers also. Its almost like I needed to use both the amp at 80hz (with HP on) and the HU at 80hz to make it work. Seems odd to me

6. New topic, is there a reason I should use the subsonic filter on the sub amp?

7. On my sub amp Im using 0.1V - 1.0V even though I have 2.0V preouts. Its been awhile since I played wit this but I recall the 1-8V not giving much power. Is this correct?

THANKS guys!

Setup

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Headunit - Alpine ida-x100

Alpine PDX 4.100 (bridged to 2x200)

Channel 1/2

Gain - approx 3/4

Filter - HP

Crossover - approx 80hz

Channel 3/4

Gain - approx 3/4

Filter - HP

Crossover - approx 80hz

Alpine PDX 1.1000 amp

Subs - 2x 12" JL W6v2s in sealed box

Gain - approx 3/4

Volt - 0.1V - 1.0V

LP Filter - approx 80Hz

Subsonic Filter - Off

Click to read more...

 

[maylar 10+ year member]

1. Right now I have both my sub amp and front amps set to crossover at the same freq (80Hz), this is the way it is generally done so there is nothing missing correct?2. I had read that 80Hz was a good crossover point, true?

80 Hz is a good starting point.

3. Whats odd is that my HP filter is on and set to 80Hz, however when I grabbed a 50Hz test tone and played it at 3/4 volume, there was sound coming out of my front speakers. Does this mean that the amp is not working properly for the HP Filter?

Filters have a "slope" that determines how quickly they roll off. A typical amp with a 12 dB/octave HPF will have some output at 50Hz (it can be calculated) when set for 80 Hz. Also realize that the calibration marks may not be exact.

4. I have an option to do a HP filter on my HU (off, 80hz, 120hz, and 160hz). If I set my HU to 80hz I noticed the sound in the fronts went away (when doing the 50hz test tone at 3/4 volume). What does this mean? Should I use the HU instead of the amp?

The HU may have a steeper HPF slope than the amp.

5. If I did decide to use the HU for the HP and not the amp, I would think I would turn it to off on the amp, however that seemed to make sound from the speakers also. Its almost like I needed to use both the amp at 80hz (with HP on) and the HU at 80hz to make it work. Seems odd to me

Adding another HPF in the line will increase the slope of the filter. Depending on how much power you're giving the speakers, if you can get away with just one of the filters and allow a bit of sub bass in the front that can be a nice thing. If you're pushing your speakers to the limits and need to keep them from whacking the stops, then use both filters.

6) I dunno ... never used one.

7) Yep.

 

[All_Logix 10+ year member]

The only use for a subsonice filter is to make sure that frequencies that are unheard by the human ear dont enter the subwoofer... just because you can't hear it doesnt mean that the speakers are not working, and this low low frequencies can be damaging to some subs...all in all it wont hurt anything to do it, and it MIGHT prolong the life of the speakers.

 

[RoachForLife 10+ year member]

Thanks guys. The thing on the roll off makes sense. Perhaps I will accept this as roll off and just continue on //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Referring to question 1, its best practice to have both amps (sub and fronts) set to the same crossover. Considering some rolloff will occur, this way im not missing out on any of the band? The other option is to have some overlap but I guess the rolloff does that for me (like the LP at 90 but the HP at 80)

 

[Why So Cereal? 5,000+ posts]

Some people overlap, some ppl leave gaps, some make them the same....just do what sounds best.