confused w/calibrating my new sub on AVIA (1 Viewer)

[JakeMcM]

I just recently had someone build me a DIY midq Tempest (about 2x2) with a 380w Rythmik amp but I'm having trouble figuring out the frequency sweep tone with avia. I have a Sony Da4es and for the time being all the crossovers are at 80 but when the frequency starts at 200hz or whatever the volume goes up if I turn up the gain on the sub itself. Why is there sound coming out of the sub if it shouldn't kick in till 80 hz? The crossover on the sub is set to its highest setting but I thought the receiver would take care of that, should I also set the crossover on the sub to 80, I didn't think that was necessary but maybe i'm mistaken.

There is also a gap in the sound from about 50-30 or so, is this a placement issue? I am using a radio shack meter and the needle goes all over the place but I have heard that they don't measure low frequencies very well...is that the case?

Can subs be placed anywhere or do they do best when they are up front with the front speakers? What placement generally gives the flattest response? When you guys put your sub in a corner do you wedge it evenly in there or is just in the general area of the corner i.e a foot or two along either wall?

Room size 11x15, is this square enough to be worried about standing waves and is there anyway to combat them.

Thanks for the help

 

[JakeMcM]

What can I attempt to fix electronically to solve these problems before I lug around the sub trying different positions.

 

[Geoff L]

I am terriable at explaning things but will give it a shot.

The "receiver crossover" to the sub and (mains when set small) (80hz) are not brick walls. You are going to have spl out put from the sub above 80hz but it should progressivly get less and less the further you go up in hz. The same with the mains they don't stop playing at 80hz, they continue to play on down in hz but at lower and lower spl levels given the type crossovers slope. The idea is the 2 (sub and mains) are sloping to meet each other to try and give a seemless blend from the mains to the sub.

Max room gain is usually found placing the sub in a corner but your room like any other, will have peeks and valleys in the sub response. Keeping the sub up front (corner loaded or not) with the mains helps to reduce phase problems. The closer the sub comes to the listening position or behind it them phase issues can occure. This is when you would use the phase knob on the Rythmik amp.

You can only experiment with placement and measurments to see where the subs location gives you the best sound/flattest/deepest/ response. Don't expect to find one in your room thats perfect, meaning a placement that provides all the above.

Usually to get a truely flat sub response will require a parametric eq, like the BFD you hear about here all the time.

I hope that helps, and maybe someone can explain it clearer than I.....

Regards
Geoff