How do I select proper crossover points and slopes

Racertrash

I have some monitors that are very nice, they are Biamped, They all have Two twelve inch speakers and one horn, the dirvers are all P audio, the horns are DDS and If I remeber right they work well down to 1.2 K, they are 2 inch horns, The drives on the horns are rated to work down to 800 hz,

I was using driveracks as xovers, but to get 8 mixes, it was better for me to buy Crown XTI's and use the DSP ( I hope so)

I have 4 k Xti on the lows and 1 Ks on the highs

I have used Gadgets 121db monitor before and got them to 119 db before I gave up Very loud and clean.

I am looking to smooth them out a bit with the Dsp on the crowns, and they sound better (at a low volume) with a butterworth at 6 or 12 db of slope, but I get better cutoff when I use LR at 24 db of slope. I am worried about things getting by and taking out the drivers with the slope at 6 db .

suggestions

Suggestions?

Dennis

LR24 would be the typical filter you would use. BW 6 or 12 would more easily yield a smooth phase response at the xo point but with the downside of huge overlap. LR24 will yield more separation but you will have more work to do taming the phase response.

http://en.wikipedia.org/wiki/Linkwitz%E ... ley_filter

Dennis

Gadget

The nice thing about the LR24 filter is that it exhibits a 360 phase shift..instead of some lesser portion of that...which makes transitions smoother by nature, when you look at BW18, you'll find the xover region is usually smoother (you might even try a bit of overlap), and those 12" and horns will transition nicely the closer to 1200 hz you can get. With all the processing you have available in the XTi's you should easily be able to tame the crossover region, and get those monitors tamed down so that you can get exceptional clarity and punch.

You'll also find that using the HPF and setting it up between 130 and 150hz will cut a lot of the stage rumble and din.

G

Racertrash

Thanks for the replies, gadget as far as stage rumble goes, I have been taking care of that with the LS9 either at the vocal mic or at the EQ, i have found that filters set as high as 250 hz on a vocal mic can reap some great benifits,

The monitors I have are some Clair/Mcbride and where used by the likes of Garth Brooks and Martina Mc, to name a few.

I was beginning to over lap the xover points when i was using the LR 24 filter as I was getting such a suck out near the xover Freq, at that point it was, 1.33 Khz, it seemed to be very smooth there with the DBX units but so much with the XTI,

I am just beginning to try some things but with all the expertise on here, I see no reason to reinvent the wheel and felt you would give me some good direction and I thank you all for that,. Here is a peicture of these monsters,






I will be working on them today and see what I can do with them, I will let you know

Dennis

The "suck" you are experiencing at the xo point is alignment (or lack there of). You may end up doing a little overlap there but that won't be the first step. Alignment at the xo point is achieved with the addition of delay to one of the components so that the arrival time of the two components is the same at the listening position. For accuracy, I achieve this with a dual FFT program. I think Gadget has a few tips for getting it in the ballpark without the program.

When beginning the alignment, you will see quite a valley at the xo point. The closer you get to time alignment, the closer you get to eliminating the valley but you may have difficulty achieving "smooth and flat". Perhaps at this point, a tiny amount of overlap would be your friend but I am talking only 2 to 4Hz. You can also deploy some PEQ filters to smooth things out but concentrate more on cuts than boosts.

Dennis

Gadget

Nice monitors...

The method he speaks of is a null method...you would need a frequency generator that can play the exact frequency of the crossover point. Then it's a matter of reversing the polarity of the horn (either would do but there is only one set of leads to reverse) now you play the frequency, and sweep the delay and listen for the greatest null. This then would be the closest you'll be able to get without measurement tools.

What we have done here is play the tone at the crossover frequency and reverse the polarity of one of the waves... where they are MOST out of phase is where the two cancel each other out. Don't expect total cancellation because overtones and harmonics are involved... just look for the greatest dip in the primary frequency.

Put things back to normal and there you have it...

You might want to try several different slopes while your at it and mark down the delay for each. When overlapping, the BW filters are the most musical, and 24 and 48 slopes are best. BW 18 is a good choice for HPF's.

If your looking to tailor/LPF the high end, LR6 or the like offer minimal phase shift and artifacts. Those filter types just don't make very good xover filters because there iks just too much interaction in the crossover region.

Gadget

Racertrash

Ok, I dont have one of those, but I may be able to get access to SMARTT, would that make the process more accurate and lend itself to better results?

Dennis

Racertrash wrote:

Ok, I dont have one of those, but I may be able to get access to SMARTT, would that make the process more accurate and lend itself to better results?

Do you have access to someone who knows SMAART and can interpret the data?

Gadget

Or... you could download this freeware test generator:
http://www.ringbell.co.uk/software/audio.htm
to inject the signal...

G

Dennis

Gadget wrote:

Or... you could download this freeware test generator:
http://www.ringbell.co.uk/software/audio.htm
to inject the signal...

Interesting....I bet I could find an iPhone app. Or maybe I already have one.

Racertrash

Dennis, yes I do and Gadet, thank you as always.

Racertrash

Gadget, just for reference, I have thought about what you said and signal generator, and reversing the polarity on the horn, I dont know about your system but I think because they are biamped, I think I might reverse the polarity at the amp instead of taking the cabinet apart to get to the horn, it should net the same results, I dont use bananna plugs but I might install one as a temp so I could reverse it real quick to compare,

Thoughts?

Dennis

Racertrash wrote:

Gadget, just for reference, I have thought about what you said and signal generator, and reversing the polarity on the horn, I dont know about your system but I think because they are biamped, I think I might reverse the polarity at the amp instead of taking the cabinet apart to get to the horn, it should net the same results, I dont use bananna plugs but I might install one as a temp so I could reverse it real quick to compare,

Thoughts?

The polarity reversal was just for a test....and you should be able to reverse polarity in the DSP. You don't have to build custom cables.

Gadget

Yes, the 260 has polarity reverse, AND phase in variable form...so ya.. all I do is fire up the GUI and do the deed and voila~
g

Racertrash

I found that on the DSP on the amp today :oops:

Dennis

Gadget wrote:

AND phase in variable form...

Appears to be an allpass filter with limited features...it automatically sets itself to the upper frequency of a pass band offering no user control of that function.

Gadget

:? :? um...Dennis I am not following you here... absolute phase reverse (positive or negative) and 0 to -180 phase in 5 degree increments... there may be finer adjustment available on the unit that the GUI does not show...

In the GUI double click on the 1,2,3... etc. and an output polarity/phase drop down appears...

:?:
G

Dennis

Gadget wrote:

:? :? um...Dennis I am not following you here... absolute phase reverse (positive or negative) and 0 to -180 phase in 5 degree increments... there may be finer adjustment available on the unit that the GUI does not show...

In the GUI double click on the 1,2,3... etc. and an output polarity/phase drop down appears...

:?:
G

I was referring to the center frequency of the allpass filter not being adjustable.

Dennis