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Discussion Starter #1
I was tinkering with a high pass on my subs and it pulls the subs rearward.

I'm assuming adding that filter causes a phase shift . I dont remember much about high passing subs. What's the deal?
 

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It's just a subsonic filter. Interested to see what the experts say about a possible phase shift.
 

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The only thing that I can think of is that there is already some rattle/noise/distortion pulling the stage back but having the low frequencies playing is masking it. When you cut the lows with the HPF, that sound becomes more apparent. How high are you setting the HPF? Was this more of an experiment, or are you trying to limit excursion, increase power handling, is it a ported box?
 

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Obvious question but have you tried flipping phase since adding hp?
 

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Id think not, but it is possible.
Is it though? I'm not so sure it's even possible...

That's not intended as sass, but an honest question.

From the LPF down on the sub channel nothing has changed. The HPF should just attenuate the low frequencies at whatever rate is chosen by the slope. There is no other speaker taking over below that, so there won't be anything for it to get out of phase with. Remember, phase is relative. A single speaker cannot be out of phase, phase issues require multiple sources.
 

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Discussion Starter #9
The only thing that I can think of is that there is already some rattle/noise/distortion pulling the stage back but having the low frequencies playing is masking it. When you cut the lows with the HPF, that sound becomes more apparent. How high are you setting the HPF? Was this more of an experiment, or are you trying to limit excursion, increase power handling, is it a ported box?
Obvious question but have you tried flipping phase since adding hp?
There are no rattles. Spent a lot if time and money making sure of that.


I didn't try flipping the phase as it doesnt sound like a 180. More like about 30 degrees of shift.

I run ported and I was experimenting with a filter at 25 to 30 hz

What I find odd is it affected the subs at the crossover frequncy which is 73 hz. It separated the bass. Kind off stretched it out when I was expecting it to make it tighter.

It wasnt a complete separation like a phase flip.
My kick drums went from the windshield to the front of the dash in distance.

Anyway. I turned it back off. I dont run enough sub to need it.
 

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try it..see what happens. If nothing, then rule it out real quick. I tend to prefer even slope LR filters. All crossovers can alter phase as can TA. If your box is vented around 30hz, I never really used a subsonic. 35 or so...yeah.

One of the reasons I liked old audiocontrol crossovers. Fixed crossover point and completely variable phase. Mess around with crossover slopes and types.
 

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What happens if you set SSF lower - at 20Hz....does the problem still exist?
What happens if you retune your box lower and switch off SSF?
can you move your SW enclosure around the boot.
 

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Remember, phase is relative. A single speaker cannot be out of phase, phase issues require multiple sources.
While I agree with everything you said here, I'd like to add that "multiple sources" can still mean a single driver. i.e. a single driver can have phase issues or interference between its primary sound (direct) and secondary sound (reflections). Cars is hard.:(
 

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There's no reason that a HPF at the bottom end would cause a phase issue.
It absolutely will..

Before subsonic is applied..








vs after a 25hz 18db butterworth (like op mentioned) high pass is applied.








The phase shifted just about 45 degrees at the low pass crossover point, aka, added 50 inches worth of group delay considering the 65hz low pass. 45 degrees is more than enough to cause an audible and measurable difference.
 

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It absolutely will..

Before subsonic is applied..








vs after a 25hz 18db butterworth (like op mentioned) high pass is applied.








The phase shifted just about 45 degrees at the low pass crossover point, aka, added 50 inches worth of group delay considering the 65hz low pass. 45 degrees is more than enough to cause an audible and measurable difference.
45 degrees? Holy crap, what would a more typical 24dB slope do?
 

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While I agree with everything you said here, I'd like to add that "multiple sources" can still mean a single driver. i.e. a single driver can have phase issues or interference between its primary sound (direct) and secondary sound (reflections). Cars is hard.:(
That is true, but the crossover won't change the relationship between the direct sound and the reflected sound, the reflected sound (at a given frequency) will follow the direct sound by the same amount regardless, unless you move the speaker and change it's distance from the reflective surface.
 

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45 degrees? Holy crap, what would a more typical 24dB slope do?
yeah, its pretty significant. if you want to test this, just download the helix software and activate the phase response and play with it. that said, 24db with everything else the same is something like a 65 degree phase shift
 

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Discussion Starter #19
There's no reason that a HPF at the bottom end would cause a phase issue.
It absolutely will..

Before subsonic is applied..








vs after a 25hz 18db butterworth (like op mentioned) high pass is applied.








The phase shifted just about 45 degrees at the low pass crossover point, aka, added 50 inches worth of group delay considering the 65hz low pass. 45 degrees is more than enough to cause an audible and measurable difference.

Sweet! I'm not crazy!
 
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