Setting Large or small

dholmes

Thanks again!

kuntasensei

solarrdadd wrote: »

Howdy, I'm wondering if given my set-up anyone can recommend settings, i.e., small or large, crossover frequency and lpf of lfe. All of my speakers are Polk except for the sub. With the exception of the surround backs (tsi100) all of the rest are large speakers, I even consider the tsi200 i have to have descent size to it, i use them as surrounds and I have RTi10 for the front and CSi5 for my center. The funny part is the two settings I mentioned both sounded pretty good to me but everything I read says I'm killing my a/v receiver with full band for all or not using my sub enough. I'm just not sure, at one point I had all my speakers set to full band, then i changed it to rti10-40, csi5-60, rti200-60 and rti100-70. slso, for whatever settings you might recommend, what should the sub crossover be set too, it goes from 50 - 150hz and then also has a volume knob. I'd love to hear your feedback. Please & Thank You!

For various reasons on which we could have a lengthy discussion (and we have if you poke around the forums!), you should just set all channels to an 80Hz crossover, with the filter on the subwoofer itself turned all the way up to 150Hz so you don't cascade that filter with the crossovers enacted on the receiver.

Alternately, you can set each channel based on its lowest extension, but in my experience you need to set the crossover at least a half octave above that lowest extension so you get a smooth transition to the sub before the speaker's natural rolloff. To find that point, take the -3dB point and multiply times 1.5. For instance, your RTi10s have a -3dB point of 35Hz x 1.5 = 52.5Hz, so set it to 50Hz. CSi5 goes -3dB at 55Hz, making 80Hz a good point. And so on.

But here's the caveat: The lower you set these numbers, the more power you need from your receiver to drive them cleanly. And let's face it, most AVRs aren't designed to provide much for low frequencies, as evidenced by their power ratings and the damping factor of their amp sections (i.e. how quickly it can bring a woofer to a stop once activated). If you're using external amplification, you can adequately drive speakers at a lower crossover because the amps are usually much better at bringing the woofers to a halt (>200 damping factor, compared to the typical AVR damping factor of about 60). The result is much "tighter" sounding bass that is distinct and not "muddy" sounding.

That's a big reason you should consider just using 80Hz for all channels, even your towers, if you're driving them with a receiver. The amp in your subwoofer will typically have a much better damping factor, and everything above 80Hz that's going to your speakers won't be affected by the amp's damping factor as audibly as deep bass is. You still get the advantage of having tower speakers, since crossovers are a gradual transition and you will still get bass to the speaker well below that point as the subwoofer slowly takes over.

As for LPF of LFE, this is a THX-legacy filter put in THX receivers solely to maintain compatibility with THX-spec'd subwoofers. It likely defaulted to 80Hz and is usually not adjusted by any auto-setup routine (because it has ZERO effect on redirected bass from the other channels - just the LFE channel). To ensure that you're passing the full bandwidth of the LFE channel, you should set it to 120Hz, which is where the LFE channel is brickwall filtered by its nature. It will not increase the possibility of localization of the subwoofer because very little above 80Hz is placed in the LFE channel by audio mixers... but it will allow the harmonics above sub-80Hz sounds to be properly reproduced by the subwoofer.