Importance of port placement?

[Grimfate126]

Yes, but not any better than with the method I have suggested, simply more time consuming.

ok

ill start a build thread in a couple months -_-

 

[Grimfate126]

more problems.

just to see what the final frequency response would be, i added a highpass filter (butterworth, 4th order, 20 Hz cutoff), which is how i intend to set it on the amp, and a lowpass filter (butterworth, 4th order, 100 Hz cutoff). Doing this however, rocketed my group delay. At 20 Hz, the group delay is now 65 ms, from 30 ms without a filter.

im utterly confused at this point. what are the best ways to handle this?

 

[TLS Guy]

more problems.

just to see what the final frequency response would be, i added a highpass filter (butterworth, 4th order, 20 Hz cutoff), which is how i intend to set it on the amp, and a lowpass filter (butterworth, 4th order, 100 Hz cutoff). Doing this however, rocketed my group delay. At 20 Hz, the group delay is now 65 ms, from 30 ms without a filter.

im utterly confused at this point. what are the best ways to handle this?

The time shift of a fourth order filter is a whole cycle, so it will change the group delay significantly. For a complete filter high and low pass it is a full cycle. At 20 Hz it is about 5msec. However you are only using half a crossover at 20 Hz since it is only a filter, so the time delay is a half cycle, 2.5 msec At those frequencies I would not worry about it. What is the reason you intend to use the low pass crossover on the subamp? It is usual to use the crossover in the receiver processor. You certainly do not want to cascade both filters. If you have both low and high pass filters at 100 Hz, then you will have a whole cycle of time shift, which is 1 msec.

I think that receivers usually have second order crossovers between subs and mains so the time delay is one half msec at 100 Hz, the sub being delayed a quarter msec and the mains ahead a quarter msec.

I hope this helps clear your confusion.

 

[annunaki]

Grim,

You can simply do a 2nd order (12db/oct.) infrasonic filter at 20 hz (3rd order 18db/oct. if you must is also acceptable). This combined with the natural roll-off below the tuning frequency creates an effective 36db/oct. filter or greater (if a higher slope is utilized) below 20hz. The infrasonic filter limits the signal to the amplifier to prevent overdriving or the woofer, and the roll-off below tuning helps take care of the rest.

 

[Grimfate126]

Grim,

You can simply do a 2nd order (12db/oct.) infrasonic filter at 20 hz (3rd order 18db/oct. if you must is also acceptable). This combined with the natural roll-off below the tuning frequency creates an effective 36db/oct. filter or greater (if a higher slope is utilized) below 20hz. The infrasonic filter limits the signal to the amplifier to prevent overdriving or the woofer, and the roll-off below tuning helps take care of the rest.

The thing that confused me about the oaudio amp was that its docs never specify what order subsonic filter it uses. The lowpass filter on the amp is a 4th order, so i assumed that the highpass was the same.

How can i accomplish a 2nd order subsonic filter with the amp?

Also, can someone link me to a good site on all these "orders"? I dont fully understand them.

 

[Grimfate126]

The time shift of a fourth order filter is a whole cycle, so it will change the group delay significantly. For a complete filter high and low pass it is a full cycle. At 20 Hz it is about 5msec. However you are only using half a crossover at 20 Hz since it is only a filter, so the time delay is a half cycle, 2.5 msec At those frequencies I would not worry about it. What is the reason you intend to use the low pass crossover on the subamp? It is usual to use the crossover in the receiver processor. You certainly do not want to cascade both filters. If you have both low and high pass filters at 100 Hz, then you will have a whole cycle of time shift, which is 1 msec.

I think that receivers usually have second order crossovers between subs and mains so the time delay is one half msec at 100 Hz, the sub being delayed a quarter msec and the mains ahead a quarter msec.

I hope this helps clear your confusion.

that was really confusing, simply because i dont know a thing about time shifts and orders.

So basically, i will be fine with this setup? (using the HPF on the oaudio at 20 Hz, and a LPF on my receiver at 100 Hz.)

 

[annunaki]

So basically, i will be fine with this setup? (using the HPF on the oaudio at 20 Hz, and a LPF on my receiver at 100 Hz.)

Yes, you will be fine.

 

[annunaki]

The thing that confused me about the oaudio amp was that its docs never specify what order subsonic filter it uses. The lowpass filter on the amp is a 4th order, so i assumed that the highpass was the same.

How can i accomplish a 2nd order subsonic filter with the amp?

Also, can someone link me to a good site on all these "orders"? I dont fully understand them.

See my thread here for a simplified explanation on crossovers.