RCF NX M15-A and Subwoofer 4PRO8003-AS please help

giusfre

Hi!
I have a drive rack PA+ and a couple of new RCF NX M15-A (frequency response 50 Hz/20 KHz) with a couple of new subwoofer RCF 4PRO8003-AS (frequency response 40/120 Hz); what is the best settings for the crossower? Do the frequency of the subwoofer have to overlay a bit the frequency of the sat? Which filter do i have to use?
thanks

Gadget

Hi,
There are a lot of different thoughts and possibilities here. UNDERSTAND that if you DO end up overlapping the crossover points you will undoubtedly end up with some cancellations and frequency anomalies... in any case , the butterworth steeper filters like 24-48 dB/ octave work best for these. JBL is a practitioner of this technique, at least on some of their older speaker models, but it's gonna be a VERY difficult thing to perfect, I'd steer clear of overlapped crossover points without some pretty hefty skills and measurement equipment...(FFT based systems like SMAART and Praxis, or Spectrafoo)

That said it's pretty easy to test different crossover types and slopes with the driverack. Typically, the most symmetric, and friendliest crossover type is the Linkwitz Riley. Higher order filters offer less interference in the crossover region, but the tradeoff is the more complex the filter the more correction for phase difference is needed. Also more complex networks can affect the sonic integrity of the sound. As aforementioned, the LR delays the signal a nearly perfect 360 degrees, and so, doesn't require any phase adjustment (which the PX and DRPA do not posses).

Make sure you use similar crossover type and slope on adjacent filters...

Powered speakers typically can be allowed to do their own HPF work and limiting, On powered subs be sure to choose a crossover frequency that will be below the subs LPF, and if you have a frequency control on your subs... turn it up as high as it will go and let the driverack set the frequency of crossover. The reason being, the driverack is dedicated processor and it's an afterthought in powered speakers (the difference WILL be very audible!)

Generally, I like to consider the size and power available to the top speakers Low driver. !5" speakers cab typically go lower with less distortion than their 12", 10", and 8..." counterparts. The motor structure of the woofer should also be considered when choosing a crossover point. For instance, a 4" voice coil woofer will be able to go much lower than a 3" or 2" voice coil woofer without breaking up. However, the lower the speaker is allowed to go the less linear the critical midrange frequencies will be.

Tradeoffs, and "It depends".... these are the truths of crossover geometry. Experimentation, and testing will result in the best results. We do know that there are some pretty safe bets. Moderately powered tops with a 12" or 15" woofer can usually be crossed @ 100-120 hz LR24. LR12 will allow more frequencies to be caught in the crossover region. Butterworth will affect the region differently (sound different), some like it some don't like it as much... Bessel is just another choice (but not available on all platforms).

One thing I don't like to do is place the crossover point on top of the kick drum frequency. That is a one note wonder that is usually 75-80hz (kick thump). The fact is tho, that one of those tradeoffs is, the higher you cross the subs the more honky/nasally they become. In the subs we typically don't want anything "intelligible" to be audible, just low frequencies and rumble. Obviously, if you have smaller tops you will need to cross the subs higher, and this is one reason for the popularity of 15" 2 way tops. They do NOT however, sound as good in the critical vocal midrange as say a 12" or 10" speaker.

giusfre

Thank you very much for your answer...but it make me more confused.
let me give details of the speakers:
Nx m15-A: frequency response 50 Hz-20kHz/driver 1" neo,1.75" v.c./woofer 15" neo,3.5"v.c /750 watt(500w bass/250w hight) max spl 132 dB
4Pro8003-As (subwoofer): frequency response 40Hz -Xover point kHz/woofer 18" neo,4"v.c./1.000 watt/crossover frequencies 80Hz-120 Hz/max spl 134 dB
Can you please tell me detailed settings for the crossover of the DR pa+ that you would use with this speakers?
Many thanks

Gadget

Ok, that's a lot to digest, but if you look.. I gave you the answer as well...

Moderately powered tops with a 12" or 15" woofer can usually be crossed @ 100-120 hz LR24.

I also told you that it's quite easy for you to try different frequencies and slopes...and I recommend you do so, but you don't have to...

I think I would start at 100hz LR24...

If your adventurous, try 118hz LR24, then 90 hz LR24 see which you like best (you may not hit those exact frequencies, just get close)

Does that answer your question then?

giusfre

yas, many thanks!
This is exactly what I was looking for!
Thanks again