Setting LPF for subwoofer

[derrickdj1]

I use a Berhinger I Nuke 3000 DSP which gives several XO options for the subwoofer. They are Linkowitz-Riley, Bessel, and Butterworth varying from 6 to 48 db slopes. Which is best for the sealed SS 18.1. If I defeat/turn off the XO the mid bass is not as detailed. I have it set as a 48 Linkowitz slope. My avr xo is also set to 80 Hz as the sub. This help filter out the midrange for a better mid bass.

[sbdman]

The typical AVR XO uses a HPF of 12dB/octave slope for the mains and a LPFof 24dB/octave for the sub. You should either use the one in your avr or your iNuke, but not both.

Since you're not driving your mains with the iNuke, I would not use it's XO feature, only the AVR's. You may be better off changing the XO point higher or lower. What did the AVR set it to on setup/auto eq testing with the mic?

Are the mains set to large? Do you have double bass selected in the AVR? Either of these settings could cause the mid range bass to be bloated.

[tesseract]

Steve is correct, use only one crossover or the other, but the AVR is probably the best choice, especially if you are running it's room correction.

If using the iNUKE, definitely use the Linkwitz-Riley slope, that will give you flat frequency response AND phase where the low and high pass meet. This is also part of the THX standard.

If the sub's output seems to be a little "ahead", or "lags" a little behind the mains, I would experiment switching between 48 & 36 dB (or 24 & 12 dB)/octave crossovers. This is like switching the polarity at the subwoofer speaker terminals, and will help you blend with the main speakers.

[derrickdj1]

I have always been in the camp set all speakers to small and use a xo of 60-100 Hz for my RF 7 system. Both subs are corner loaded and the Linkowitz slope 24 db is the typical one used for most subwoofers. I normally agree to defeat the sub xo.

Even though the Pioneer sets the xo at 80 and I have the speakers at small, the bass seems a lot cleaner cascading the slopes. I thin it is cutting out more 2nd harmonics which can be as high as 160 Hz since the slope is not a brick wall.

I will have to listen for a few days or a week cascading the slopes of the I Nuke and then trying it with only the avr xo. I was just curious to what others were doing since this is my first time with passive subs.

[sbdman]

It could be very possible that corner loading of both subs may be the problem. This position gives the highest gain, but could be causing the uneven response at the xo you speak of. Sub position has a huge influence on room modes.

If your double equalization sounds best, I'd go with it. The only way to be sure is measurement. The onmi mic is a bit expensive, but the easiest method, followed up by a REW system. This would be the only real way to actually know what's going on in your listening room.

[derrickdj1]

Steve is correct, use only one crossover or the other, but the AVR is probably the best choice, especially if you are running it's room correction.

If using the iNUKE, definitely use the Linkwitz-Riley slope, that will give you flat frequency response AND phase where the low and high pass meet. This is also part of the THX standard.

If the sub's output seems to be a little "ahead", or "lags" a little behind the mains, I would experiment switching between 48 & 36 dB (or 24 & 12 dB)/octave crossovers. This is like switching the polarity at the subwoofer speaker terminals, and will help you blend with the main speakers.

I agree that most avr's will apply a 24 db slope to the sub. Is this a compromise since ported or slot subs have different roll off characteristics than a sealed sub. The THX standards are for a sealed system. I have large ported mains which roll off different than sealed speakers. I know I am making this more complicated but, I just like learning more audio theory, lol.

[tesseract]

I agree that most avr's will apply a 24 db slope to the sub. Is this a compromise since ported or slot subs have different roll off characteristics than a sealed sub. The THX standards are for a sealed system. I have large ported mains which roll off different than sealed speakers. I know I am making this more complicated but, I just like learning more audio theory, lol.

I see your way of thinking, and you are correct about the roll off differences between sealed and ported. There is no compromise there to worry about as far as port/crossover summing, and here is why.

Most main speakers with ports are tuned in the neighborhood of 35-60 Hz. If you are high passing the mains at 80 Hz, the port is not contributing much to the output at it's tuning frequency.

On the other hand, it has been my experience that ported mains still have higher frequency sound exiting the port, muddling the midbass a bit. I prefer sealed mains or plugging ported speakers. It lets everything the subwoofer is doing shine through unhindered, articulation goes UP.

[derrickdj1]

I am done with experimenting on the xo's and the Linkowitz-Riley 48 db slope sounds the best. It sounds great with movies and music. If you have not rented the movie Oblivion, get it. The movie has a variety of LFE and the deep bass is in a majority of the film. Bass heads should enjoy this one.

[tesseract]

If the subs are properly setup, a 24 or 48/dB LR would sound best. Looks like you have everything dialed in right.

[tesseract]

Doh! My reply about slopes was referring to main speakers! The same applies for subs, though. No summing of acoustic or electrical slopes worth worrying about with a XO that high (80 Hz). If a person is crossing over close to a vented sub's port tune, I would question why.