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DJ Mizourah
05-08-2012, 08:38 PM
Hi guys. I have two RCF ART 312As and a 705A sub. I was wondering if its possible to get these to work with my friends passive sub using a crossover?

My idea was too have my mixer go to the crossover, then have XLRs to my RCFs and RCA go to his amp. I'm just worried this would blow his sub so I wanted to ask first.

sss18734
05-08-2012, 08:40 PM
Mixer > Crossover > High Pass to Active Mains
.........................> Low Pass to Amp > Passive Subwoofer

Hope that diagram makes sense :P

DJ Mizourah
05-08-2012, 09:13 PM
Yep thanks! Sorry for the double post.

windspeed36
05-08-2012, 09:15 PM
Mixing subwoofers generally isn't done due to the different SPL levels at certain frequencies and different power handling (So an uneven climb in volume as a fader is raised)

Coronaoperator
05-08-2012, 10:57 PM
Different phase responses between the 2 subs can/will cause an uneven frequency response due to cancellations. Trying to correct for the cancellations using EQ or power will put undue stress on both subwoofers. Adding power (using gains or eq) to a cancellation doesn't solve the problem, it only makes for a bigger inaudible argument. You could give it a try but if you find yourself cranking the gains or using eq to boost the low end beware that the extra power going to both subs might toast both of them.

jayhwk
05-08-2012, 11:02 PM
Using two subs of the same design (say, front loaded 18's) isn't the end of the world since they're generally similar in phase and frequency response. We just went over how splitting your subs up is bad, but if you put one design on one side of the stage and the other on the other side, I doubt you'll see any problems

Coronaoperator
05-09-2012, 12:52 AM
Using two subs of the same design (say, front loaded 18's) isn't the end of the world since they're generally similar in phase and frequency response.

Agreed, I do it quite often. I just wanted him to know to be watchfull of the eq and power because if there is a cancellation, too much of either can be inaudible leading to overuse and then the magic smoke can make a break for it and escape.

Mrspyaman
05-09-2012, 05:11 PM
Why would there be cancellation in that setup unless the crossover wasn't doing its job?

windspeed36
05-09-2012, 05:16 PM
Why would there be cancellation in that setup unless the crossover wasn't doing its job?

http://www.moultonlabs.com/more/about_comb_filtering_phase_shift_and_polarity_reve rsal/

Mrspyaman
05-09-2012, 05:31 PM
http://www.moultonlabs.com/more/about_comb_filtering_phase_shift_and_polarity_reve rsal/
Why would the tops put out the same signal as the bottoms?
To clarify the high output and low output from the crossover.

windspeed36
05-09-2012, 05:39 PM
We're not worried about the tops, more the two subs cancelling each other out due to their different design and components

Mrspyaman
05-09-2012, 06:13 PM
We're not worried about the tops, more the two subs cancelling each other out due to their different design and components
Ok, I was going off of this:
Mixer > Crossover > High Pass to Active Mains
.........................> Low Pass to Amp > Passive Subwoofer

Which does not include the second subs.

sss18734
05-09-2012, 08:09 PM
Ok, I was going off of this:
Mixer > Crossover > High Pass to Active Mains
.........................> Low Pass to Amp > Passive Subwoofer

Which does not include the second subs.

Yeah I didn't take into account the fact that he was mixing the subs. I suppose you could split the low pass output into the external amp and into the built-in subwoofer amp and then set the gains from that point on. Mixing/matching isn't usually the best thing to do but the only way to know exactly how it will sound is to try it out *shrug*

Coronaoperator
05-09-2012, 09:41 PM
Why would there be cancellation in that setup unless the crossover wasn't doing its job?


There may or may not be depending on the phase response of the 2 different designs and any cancellations will only be at certain frequencies and not others.

http://img401.imageshack.us/img401/5561/oldresponse.jpg (http://imageshack.us/photo/my-images/401/oldresponse.jpg/)

The bottom graph shows a typical phase response of a loudspeaker: frequency on the bottom, phase on the right. Ideally it would be a straight line at 0 degrees across all frequencies. Loudspeakers do not behave ideally. Allthough all frequencies would arrive at your ear at the same time, they do not all line up perfectly with respect to the first sound being 0 degrees or top dead center on a sine wave. This speaker by itself even with the varying phase response will sound normal. If we now add another subwoofer of a different design, the phase response plot may be much different than the one shown. The frequencies where the phase of the 2 drivers is the same or within about 90' of each other will sum and get louder as you would expect by adding another woofer. The freqencies where the 2 speakers are 180' out of phase will cancel the same as if you reversed polarity on one of your 2 subs. Unlike reversing polarity on one of 2 identical subs, the cancellations (if present from different phase responses) will only be at the frequencies that line up 180' out of phase on the graphs.

Trying to compensate for a cancellation caused by opposite phase response between 2 drivers at a particular frequency with eq can eat up power and toast voice coils because you cannot hear (cancellation remember) any difference no matter how much power you throw at it.

Coronaoperator
05-09-2012, 09:55 PM
Moral of the story is go ahead and use the 2 subs . If they are both the same size woofer and are of similar designs (ie ported boxes) then the phase responses should be similar enough to give you more volume and relatively smooth response. Just don't hook up an RTA and try and boost any dips with an eq.

DJ Higgumz
05-09-2012, 10:49 PM
it's touch and go, you can't really tell until you hear it. i wouldn't advise buying two different types, but in your case its fine, but try it first.