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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Mario Roman on January 18, 2011, 08:27:35 pm

Title: Aux Subs crossover freq??
Post by: Mario Roman on January 18, 2011, 08:27:35 pm
Good Day All,

I curious as to what frequency most of you cross your mains to subs at. My setup is 01v96 into a DCX2496 active crossover. Mains are on outputs A & B and aux subs are on output C. Speakers are U15pb and subs are LS800pb. Music is classic to current rock. I currently have the mains passed at 100hz L/R 24db/oct and the subs passed at 100hz BW 48db/oct. Any suggestions to inproving this setup? I've just recently upgraded to Smaart 7 and have a couple of days before this weekends gigs to play around and learn the new format. So I thought if I could make any improvements now would be a good time. Thanks.

Title: Re: Aux Subs crossover freq??
Post by: Brent Venter on January 19, 2011, 01:17:48 am
Hi Mario

You mention that you have Smaart 7. Are you able to do some measurements and do a transfer function?

The acoustical crossover will depend on the physical displacement between subwoofer and mid/high and on top of this magnitude (level) will also contribute to the equation.

Title: Re: Aux Subs crossover freq??
Post by: Tom Reid on January 19, 2011, 10:56:24 am
I've seen folks "underlap" their crossover regions where subs stopped at 90HZ, tops started at 100Hz, and I've seen folks "overlap" this same region subs at 120HZ, tops down to 100HZ.  It all depends on the summed output at the crossover region.

One thing that most people miss which helps with a two way setup is the timing between the top and bottom boxes.
Crossover slopes, box design, and cabinet alignment all play a part in lining up the full range of sound hitting you in the back of the room.

The first thing to try is run a tone at the crossover freq through the top box, then the bottom box at the same SPL.
Then play the tone through both at the same power level.  You should have (theoretically) a +6db gain in output.
Title: Re: Aux Subs crossover freq??
Post by: Mario Roman on January 19, 2011, 12:13:33 pm
Here is what I ended up doing. To phase align the tops and subs through the crossover point, I changed the sub crossover to 90hz BW 48db/oct and tops 80hz L-R 24 db/oct. I aligned with a higher level going to the subs "haystacked" which seems to work live with the type of music we play. I didn't want to align the system with an equal power setting and then have the crossover point change if I turned up the aux send to the subs. I managed to get the sub and main phase at the crossover point to lay exactly on top of each other. The system sounds noticibly better. I'll know more when I actually try to align the system in this weekends venue. More to follow.....