How to set up a DCX 2496.

[BassheadUK]

This is a really good read. I have both the DEQ and DCX. Up till now I have had a play with the auto EQ with the RTA using the ECM8000 mic, this (in my garage had EQ'd the passive cheap NJS 15" 400w max speakers - The difference was night and day, they sounded terrible with no EQ, with the EQ on, it sounded half decent, not bad from a cheap pair of speakers that could only push about 70db. These were being driven by my JBL MPX1200 - Same settings on the Mackie sound bloody terrible !

Up till now, the DCX hasn't been plugged in, well I lie a little, I plugged it in, pressed several buttons and thought that was for another day, where its remained off for about 8 months.

As my first T39 will be finished some time soon, I have purchased a pair of active Mackie SRM450v2 to act as tops, until I can engineer a pair of either OT12's or if i feel brave, maybe DR250's.....

My DJ partner tells me he's got a family wedding to do in May, I should have (health permitting) my one T39 Lab12 done by then, hence the Mackie (he's got some Gemini manufactured EON copies and they aren't great at all)

My thoughts at the moment are, If I use two outputs from the mixer (Behringer VMX1000USB) for the tops, it has a sub output. I wonder, can the stereo feeds, go into the EQ, and from the EQ into DCX on inputs A & B - And pop the SUB output into input C on the DCX ? - Then set the DCX to limit levels into the Mackie full range, and limit power to the MPX1200 for the subs ?

Im going to re-read the thread, and press some buttons and see what happens.....!

Is there any advantage of using a DCX in conjunction with active tops? - First time of owning active speakers.

[David Raehn]

I don't have a DEQ, but I use my DCX with a pair of SRM450V2s and a quad of T48s. Not being stereo, I use 1 input and 2 outputs on the DCX. I would think (feel free to correct me on this, folks) this would be the same as your setup , while you would have the advantage of RTA and more concise EQ control. The DCX is a 'manager' of the signal after it is 'polished' by the DEQ. If you are going to run ANY of Bill's designs, especially subs, you will need the limiting control of the DCX and will benefit from the crossover controls.

[CoronaOperator]

Is there any advantage of using a DCX in conjunction with active tops? - First time of owning active speakers.

Active tops generally have some kind of tone shaping controls on the back of them. Problem with that is you have to run out front, listen, then go "behind" the speaker to adjust the sound, then run back out front to listen to your results, and repeat that process 32 more times until it sounds just right. Its much better to be able to do your adjusting while you can actually hear what your adjustments are doing. That's where the DCX comes in. That and you have x-over, better eq's, level controls, delay, etc all in one place at your fingertips.

[Grant Bunter]

BassheadUK,

I would use the stereo with 1 sub factory setting on the DCX.
Plug left and right out of the mixer into the DEQ and use that for EQing.
Then the DEQ outputs into the DCX.

Set the sub output channel up as already described in this thread.
For one T39, that will be, 45Hz high pass LR24 or BW24, and try 100Hz for the low pass. And don't forget the limiter

Then on your tops/mains outputs, set a high pass of 100Hz, LR24 or BW24. Try that and see how it goes.

Setting a 100Hz HP will free up the active tops somewhat, as they aren't trying to reproduce lower frequencies.
I would try to make sure any EQ settings on the active speakers, even high and low dials, be set to zero...

[escapemcp]

My thoughts at the moment are, If I use two outputs from the mixer (Behringer VMX1000USB) for the tops, it has a sub output. I wonder, can the stereo feeds, go into the EQ, and from the EQ into DCX on inputs A & B - And pop the SUB output into input C on the DCX ? - Then set the DCX to limit levels into the Mackie full range, and limit power to the MPX1200 for the subs ?

I used a similar setup for a short while before I had my DCX (when I used the DSP on the amps). I used the sub output of my Berry DJM4000 mixer and set the crossover at 200Hz (the highest it would go). I then set the main outs to be 'full range' rather than 'crossed over' (or they would start losing stuff as it gets down toward and below 200Hz). This way I could then use the DSP to actually shape the sub signal with a 100Hz LPF. This was all done as the iNukes don't have a through line and it was the only way of getting a signal to the sub amp. The 200Hz figure was simply to allow enough of the sub frequencies through so that the frequency range I was interested in was barely affected by the Berry mixer - at 200Hz I'd be 30dB down using a 24dB LR slope @ 100Hz (using the iNuke's DSP), so what ever the mixer reduced the level by at 200Hz (3db, or 6dB if it uses an LR filter), it wasn't really going to matter - sorry that all got a bit complicated there! I didn't know what the steepness of the slope was on the mixer either, which would have further complicated the issue if I was using the mixer to filter the subs to 100Hz.

Now that I have the DCX, I don't need this setup. The DCX will do the job (i.e. creating a sub output from L&R) just fine. What I AM using the 'C' input for is to provide control of my monitor speaker. That way the volume can still be adjusted from the Berry mixer (as different DJs prefer different volumes) and I can then cut off everything below 100Hz from the monitor, thus allowing it to run louder and cleaner. That 'C' input can be very handy in certain situations like this.

[BassheadUK]

Well it's 00:36 here in the uk. Just finished the bulk of cab two T39 lab12 just got the mouth braces to do on both. Yay.

I've been playing. Think I've managed to setup the DCX to have ch1&2 as left and right and 3&4 as sub outputs. The only thing that concerns me is I can't seem to lower the output to less than 47v from my MPX1200 JBL. I've turned the DCX all the way back to -24 db to achieve 47v. I understand the max on a lab 12 is 55v from the plans??

Ok if it's a max of 55 and I'm capped at 47 that should be fine, doubt I'd get near that anyhow.

Is it normal for the limit lamp to then be on pretty much the whole time when any signals passed through it? Even without any if the green LEDs lighting up, the limit lamp flashes with some music.

[Grant Bunter]

Well it's 00:36 here in the uk. Just finished the bulk of cab two T39 lab12 just got the mouth braces to do on both. Yay.

Make sure the mouth braces are in and well cured before using the cabs.

I've been playing. Think I've managed to setup the DCX to have ch1&2 as left and right and 3&4 as sub outputs. The only thing that concerns me is I can't seem to lower the output to less than 47v from my MPX1200 JBL. I've turned the DCX all the way back to -24 db to achieve 47v. I understand the max on a lab 12 is 55v from the plans??
Ok if it's a max of 55 and I'm capped at 47 that should be fine, doubt I'd get near that anyhow.

It's no surprise you're struggling to reduce voltage from your amp.
Honestly, it's to much amp for your subs!
The MPX1200 puts out 800W (continuous, as suggested by the manual) at 8 ohms, or 80V/channel.
So a -24dB reduction on the limiter would be about right for 47V.
Change the reduction to about -22dB for what should measure not much over 50V, but less than 55V.

Is it normal for the limit lamp to then be on pretty much the whole time when any signals passed through it? Even without any if the green LEDs lighting up, the limit lamp flashes with some music.

I'm assuming you mean the limit lights on the DCX.
With gain structure set correctly in the entire chain, you would see perhaps an odd flicker of the limit light.
When a less powerful amp is used.

Part of the reason the limit light is pretty much on the whole time is that it is constantly having to limit output of the MPX1200 for the voltage output you are aiming for.

The following advice is for BassheadUK's particular situation only, based on the output of his amp:
There's a number of ways you could approach fixing this.
One would be to decrease the output at your mixer. I would be leery of this method, as anyone else who might use the system could just push your faders higher, making the limit lights being constantly on, and probably leading to blown drivers due to voice coil overheating.

What I suggest is to go back to the sub channels (ie outputs 3 and 4 as you have set your DCX up) and reduce output gain. I'm not sure exactly how much room for adjustment there is in this scenario and don't have time to check it right now, but see if you can make the setting -6dB initially. That may be enough to stop the limit lights being on pretty much the whole time.
If it still doesn't "fix" the problem, try a further reduction if that is possible.

If that doesn't fix the problem, take the input gains on channel A and B into the minuses as well. Doing this may mean you need to increase output gains on Outputs 1 and 2 (for your tops) to get some subs/tops balance.

If, after all that, you still can't get the limiter lights to stop showing except for perhaps the odd flicker, you need to get a lower powered amp...

[BassheadUK]

Hi Grant,

Thanks for this, my pal has a 400x400 RMS amp, managed to blag that and capped it down to 40.2v, however playing with my iPhone with tone generator I manage to hear 30hz unto 140hz - I have the DCX set to BUT24 45Hz on the left hand side of the page, with But24 100Hz on the right. Should this only pass those frequencies between down that channel?

[Grant Bunter]

Hi Grant,

Thanks for this, my pal has a 400x400 RMS amp, managed to blag that and capped it down to 40.2v, however playing with my iPhone with tone generator I manage to hear 30hz unto 140hz - I have the DCX set to BUT24 45Hz on the left hand side of the page, with But24 100Hz on the right. Should this only pass those frequencies between down that channel?

The lesser the slope, the more content you will hear above your high pass and your low pass points.
Also, BW is not as steep a slope as LR. So that will let more "through" depending on where in the slope you are measuring.
And because it's a slope (not a vertical line) you will get content, but it should be well down volume wise, compared to the content you hear, in your case, from 45 to 100Hz.

All the slopes are XdB per octave.
One octave down is half the frequency, so:
One octave down from 45Hz is 22.5Hz. 30Hz is less than half way between the two, so if you were to measure it, it should be at least 12dB quieter compared to 45Hz.

One octave up is double the frequency, so:
One octave up from 100Hz is 200Hz.
Again, 140Hz should be at about 12dB quieter compared to 100Hz.

So, it's working as it should...

[BassheadUK]

I have had to revert back to the JBL amp, I was thinking that to get the 50v max setting, a 60hz sine into the mixer, all faders and gains maxed out so every things in the red, and that should limit the output, on the front of the amp, I managed to get the control to 14, however when bouncing some music through it, the tops were outshining the (single for now) sub, and it wasn't pushing very much at all, I managed to turn the amp up to 50% of its output to equalise top/sub

christ, these things kick

[Grant Bunter]

Redlining everything simply sounds awful.
Distorted.
Sucks!

[BassheadUK]

Oh yes, I agree, the only thing that sounds awesome at the redline is my V8 Rangerover !

But, pissed up nob heads having a blast....? Sometimes the gains get pushed too high.

[Jools4001]

Oh yes, I agree, the only thing that sounds awesome at the redline is my V8 Rangerover !

Spoken like a man who's never ridden a Ducati.

[markandersonsa]

Great work Grant
This has been a great help

[Grant Bunter]

Great work Grant
This has been a great help

Thanks!
The thread is designed to take the mystery out of the device...