Bass management

dkubis

I read an old Polk article about bass management and it said set the mains as large even with a powered subwoofer. When I bought the 550pro it says to set the mains as small with a filtered frequency over to the sub. My mains are rt2000p and rt1000i both with built in powered subs.

I've tried both ways and it always sounds better with the mains set as large. My receiver allows me to run to my sub even though I have my mains set to large. Unfortunately the sub will be out of phase even with a phase adjustment. When I run my speakers as small it sounds cleaner but lacking in lower mid range. When I set them as small they'll cross at 40 or 60hz.

What is Polk's official stance when pairing large towers with powered subs with another subwoofer? If we filter them we're almost defeating the purpose of having powered subs in the tower. I also have the cs1000p center that has a powered sub.

Conradicles

dkubis wrote: »

Unfortunately the sub will be out of phase even with a phase adjustment.

Welcome to Club Polk! What makes you determine this statement?

dkubis

A filter with non linear phase varies with frequency. When you adjust the phase with small speakers you are shooting for the frequency closest to the crossover. When you set the mains to large you're offering up the full frequency range to the mains. Depending on where you set the lpf/hpf you could be sharing a range of frequencies between 25-60hz.

Syndil

dkubis wrote: »

What is Polk's official stance when pairing large towers with powered subs with another subwoofer? If we filter them we're almost defeating the purpose of having powered subs in the tower. I also have the cs1000p center that has a powered sub.

The RT2000p has a lower -3db limit of 25Hz, and the RT1000i has a lower -3db limit of 36Hz. Given these numbers, if you want equal bass from your mains, you need to set your crossover above 36Hz, or the bass will roll off as the frequency dips below that number, given that the RT2000p will still be outputting measurable bass while the RT1000i's bass volume will be decreasing.

That said, the -3db limits attributed to these speakers are not fixed measurements--they are greatly affected by the room in which the speakers are placed. So it's not an exact science--you can't simply go by what someone else tells you, manufacturer or otherwise. You have to let your ears be the ultimate judge. If it sounds better with the mains set to large, then there is your answer.

Regarding your statement about phase... I'm not quite sure you are using the correct definition of phase.

http://www.crutchfield.com/S-dy39AkoZp4W/learn/learningcenter/home/speakers_faq.html#phase

tonyb

What he said ^^^.

Your in-room response will always vary because we all don't have the same room let alone a specific audio chamber that manufacturers use for these specs. Having owned both those speakers in the past, I can pretty much tell you that 25 hertz isn't even close to the reality. I would cross them over in the neighborhood of 60-80 depending on the subwoofer used and the room. Setting them to large is still ok if you dig the sound but most don't as the low end can get too meshed up with the sub's lower end. 2 different types of bass with the sub most likely being quicker and deeper. None of this stuff is written in stone so play around with the settings until your ears tell you it's kosher.

Ern Dog

Here's a good resource I've used. His name is Barry and he works at JL Audio as their tech support person. He created a website called the Sound doctor and he goes over all the ins and outs about sub setup HERE.