Crossover Frequency

[Impelled]

Speakers are usually rated in open air.
If you place it near a wall it will gain up to 3dB.

[DD66000]

Speakers are usually rated in open air.
If you place it near a wall it will gain up to 3dB.

Which is what I said in post #8. In the case of my PT800s they go from -6db to -3db when wall mounted.

[Impelled]

It is yes

[Josuah]

Its not the way I see it. Its +3db above zero and -3db below. so its still -3db at 50 htz.

Okay, there's nothing wrong with saying it that way. But does that mean you would set your subwoofer level (measured flat for the purpose of argument) at the zero point? If so, your subwoofer will be on average -3dB lower than your mains. Or would you set your subwoofer so it is +3dB? And so when measuring, it is flat at +3dB? Except I'd want to set my crossover at a frequency so that when integrated everything was flat at +3dB, which will be some point higher than 50Hz then?

[Impelled]

Depends where you place your subwoofer.
If its near a single wall, you will gain up to 3dB, near a corner will gain up to 6dB.

[guggas]

I got my speakers in today, and set them up. I did the auto calibrate function and then went in to manually set crossover. It turns out my only chooces are 50, 80, 100, 150, and 200.
It sounds the best at 80.

[DD66000]

Okay, there's nothing wrong with saying it that way. But does that mean you would set your subwoofer level (measured flat for the purpose of argument) at the zero point? If so, your subwoofer will be on average -3dB lower than your mains. Or would you set your subwoofer so it is +3dB? And so when measuring, it is flat at +3dB? Except I'd want to set my crossover at a frequency so that when integrated everything was flat at +3dB, which will be some point higher than 50Hz then?

At ANY XO point when both drivers are -3db they sum together to produce a flat response @ zero.
When I play my older L212s which have a acoustical roll off @ 70 htz I set my P7 pre-amp @ 80 htz for the sub XO, being my choices are 50, 80, off.

For my PT800s, I set the sub's XO to 100~110, which is about the max for the SUB1500, as it is VLF sub. So that gets me close to the PT800's -3db point. If I were to set the sub XO to 80 then I would end up with a 3db dip, as the PT800 is -6db @ 80.
So that gets me close to what the PT800 was designed for, when stacked to a PS1400 sub to make a full range system with the XO @ 130.

[Irvrobinson]

Man, I have played around with crossover points until I'm blue in the face and I always end up back at 80hz. May mains dig pretty deep but 80 just seems to be the best blend of everything. (My surround are crossed over at 120hz).

I played around similarly and came to the same conclusion, a high-pass filter at 80Hz for the mains. Since we have a different speakers, subs, and rooms, I wonder why 80Hz is turning out to be some sort of magic crossover frequency?

[DD66000]

I played around similarly and came to the same conclusion, a high-pass filter at 80Hz for the mains. Since we have a different speakers, subs, and rooms, I wonder why 80Hz is turning out to be some sort of magic crossover frequency?

80 htz is the point where the bass becomes omni directional. Meaning anything below that point the direction of the sound can not be located. And even with 'full range' speakers, unless driven by a very large amp, will not be as forceful as a good sub.
If you have the good fortune to have something like the Revel Salon2 and have very good amps, like a pair of Parasound JC1 mono blocks, then those full range speakers will kick ***.

The one exception in most cases for the XO point is if the mains and sub(s) are co-located. Such as with a JBL Performance Series system. When docked together and the internal 130 htz XO is used, they become a full range system with a built-in powered sub. So the 130 htz XO does not become a problem as both share the same location.