Sub Questions

[blu1183]

i just hooked up my surround sound last nite, i watched a movie and the sub was working but i have some questions. theres 2 input spots L and R. does it matter which i pick? also whats lowpass and phase?? what do i put them on?

[StimpsonJCat]

You can put it in either. Most put it in L. You can actually get a splitter and connect both (but it won't really make any difference).

Set the low pass to as high as it will go (you want the AVR to do the bass management) or turn it off if possible. Phase depends on where you have the sub placed. If you only have two choices set phase to each and go with the one that sounds louder. If your AVR has some kind of EQ software set the phase to 0 and run the software (Audessey for example).

[blu1183]

i have the phase to 0% its either 0 or 180

also i have the db at 5. i think the highest is 10. i

[ghebert]

Some subwoofers have a main input for when you are connecting from the LFE output of a receiver and the other output for when you are using an external cross over system.

[StimpsonJCat]

Originally Posted by blu1183

also i have the db at 5. i think the highest is 10. i

That sounds like the gain. About halfway is good for the gain. Then you can change the level if needed from there in your AVR.

[statikcat]

Originally Posted by blu1183

i have the phase to 0% its either 0 or 180

Look at this phase diagram :

http://www.eng.cam.ac.uk/DesignOffic...b/AC/02032.png

Let's pretend the last picture in the diagram is occurring. When two of the same waveforms are opposite of each other they cancel each other out (no sound!). This is 100% phase. Some waveforms can partially cancel each other as well. So if this is happening in your setup you would want to turn the phase (upwards of 180) to create what you see in the first picture.. or at least get closer to that image.

Phase can be caused by the same signal coming from multiple directions. This includes things like wall reflections and multiple speaker palcement. If the signal bounces off the wall behind the speaker and comes back towards you it might hit the outgoing waveforms in a way that causes phase. That is a reason why distance from the wall is important. It also can vary depending on what material your walls are made from because different materials absorb and reflect different bands of frequencies at different amounts. As you can imagine phase can be introduced in a variety of ways depending on speaker placement and the frequencies each speaker play in relation to one another. When you hear someone refer to "fine tuning" a room they are often referring to phase and reflection issues and eliminating them to get the best sound.

With your system I would suggest crossing over the sub at 120. This means the sub will only play frequencies at 120 and below. In your receiver set your other speakers to cutoff at 120.. meaning they will only play signal above 120hz. This way you have the sub playing separate freq than the rest of your speakers. It might not matter with the 6750 anyway because the main speakers can not produce much bass to begin with. All rambling aside.. you should probably just leave your phase at 0 but it does not hurt to experiment.

I mainly deal with phase in the recording studio .. but a lot of the concepts should still apply to home theater.

[jomari]

if you'd like to tho, i can certainly suggest to use the knowledge statik has implied on, as an experiment. using two subwoofers, you can actually 'see' the difference when implementing 'out of phase' frequencies,

and notice (depending on the two subwoofers placement - i personally tried this with them stacked on top first, then in proper placement),
when you have them stacked,
in phase works well together - no problems there.
out of phase or 180 - you can hear how 'empty' it would sound, cancelling each other at times, and well, not getting pure silence, but you can sort of 'see' something happening.

then place them in their corresponding places, and see again the effects. got it right, out of phase would determine if its er... the ideal setup so to speak. it sort of guides me at times to show if i am on mark. its unconventional, but can definitely educate us thru experience.

the only problems with systems setup at anything higher than 80hz, is that the subwoofer sometimes can become directional, with a general amount of people able to localize the subwoofer.

again, it depends on each persons setup, including the speakers if they can handle 80 or not. some speakers cant, so in essence, work with what you have and see how well it blends in with your fronts.