HPF on Head unit vs. HPF on amp?

[Guitarmageddon]

Okay, so this is where someone needs to correct me if I am wrong- a High pass filter is used to block frequencies LOWER than the setting from getting through a set of speakers, correct? So if I were to set my HPF to 50hz, no bass frequencies LOWER than 50hz should come out of the speakers, correct?

Im using a kenwood excellon x600 amp (100rmsx4) and a pioneer avh-4200dvd through two polk db 6501's in the front, rear speakers remain stock and amped by HU. I have the HPF on the amp itself turned off, but I set the one on the head unit to 63hz. While playing with the HU's eq, I noticed that I can up the frequencies on the bands lower than the HPF is set at and it still makes a tonal difference.

Are the HPF's on the head unit not as efficient as one that is actually on the amp itself? Or would this happen any time you bump frequencies even with a high pass set?

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[T3mpest 10+ year member]

A HPF or LPF , either or, does not act as a brick wall. They are listed with "slopes". Usually 6,12,24,36,or sometimes 48 dbs/octave. What this means is that at the frequency you pick, say 60hz in your case, the speaker will be getting only 1/2 power and be 3dbs down. Below that point it'll continue to drop off at a rate of xx/db's octave depending on the slope of the crossover. You'd have to check your manual to see how sharp your slope it. In simpler terms you will get some output on the other side of your filter, you just get less and less as you get further past the crossover point.

 

[miker 5,000+ posts]

A HPF or LPF , either or, does not act as a brick wall. They are listed with "slopes". Usually 6,12,24,36,or sometimes 48 dbs/octave. What this means is that at the frequency you pick, say 60hz in your case, the speaker will be getting only 1/2 power and be 3dbs down. Below that point it'll continue to drop off at a rate of xx/db's octave depending on the slope of the crossover. You'd have to check your manual to see how sharp your slope it. In simpler terms you will get some output on the other side of your filter, you just get less and less as you get further past the crossover point.

Sooo what are you supposed to do about blocking unwanted frequencies?

 

[Guitarmageddon]

I suppose the simple answer to that would be to find that frequency you want to block, take your happy little fingers over to the eq, and bring the freqs down. Actually, I do think that the little bit of bass that creeps through the crossover while the HPF is engaged sounds better than turning the HPF off and tuning down the lower freqs. If that makes any sense.

 

[Louisiana_CRX 5,000+ posts]

using multiple crossover from radio to the amp will cause multiple problems...besides changing the slopes you'll sometime experience cancellation and loss of frequencies due to the over/under lapping of multiple frequencies....you can also experience phase issues as well....Just use one crossover ...either the deck or the one built into the amp....

 

[keep_hope_alive Premium Member]

the only way to increase the slope of a crossover is to add more in series. whether that is done inside the amp or in two different pieces doesn't matter - slope will be affected the same.

that siad, you won't get a head unit crossover in the exact same place as an amp crossover. as a result, decide which crossover point is easier to adjust and use that one to fine-tune the point while listening to the effect. choose whatever you like the sound of best.

crossovers will affect phase around the crossover point. keep that in mind.

 

[anwaypasible 10+ year member]

i'd use the headunit crossover and try to conserve some of the power for the frequencies that arent being blocked.

you might find that your headunit will play louder with less distortion if you cancel the bass out on the headunits amp.

 

[BrownVanMan 10+ year member]

hu cross usually only does the speakers connected to the hu unless is say output 1 etc.

 

[Rich B 5,000+ posts]

Just raise the HPF until the sounds diminish to the point its acceptable.

Few mids like being crossed over that low anyway.