BillFitzmaurice.info

Ok, trying to setup my DCX.

I know it's been asked 1000+ times, but honestly, I have scrolled through months of posts looking for DCX info and can't find much that helps me.

Cannot make heads or tails of the manual! Well, not quite true, but it is not "friendly".

Are people using a factory preset, modifying and saving as another preset?

I have got this far:
input A+B and summed.
sub out summed and LR48 at 45Hz. (IITP to HP at 45Hz for < 4 T39's, the HP only gives me 12db slope, do I add that too?)

Do I need to LP the sub?
Or just crossover the tops at desired frequency and the resultant slope be ok? What slope and pattern do most ppl use?

EQing: Do most ppl use the DCX as master EQ for system tuning and then DEQ to RTA/Room tune?

Setup: Mixer L R out to DEQ. DEQ to DCX. DCX to amp?

Please help.
Feel free to be really expansive with answers...

Thanks in advance
Grant

I use XTi amps so not familiar with the DCX but being stuck with 12dB /Oct doesn't seem right.

Are you using LR ( Linkowitz (sp) Reilly) HP filter? Should be at least 24 dB/oct preferably 48 dB/oct

Grant Bunter wrote: I have got this far:
input A+B and summed.
sub out summed and LR48 at 45Hz. (IITP to HP at 45Hz for < 4 T39's, the HP only gives me 12db slope, do I add that too?)

I just tried on the DCX Remote and I was able to get LR48 on both ends of the sub. I had selcted output 3 to be the sub, renamed it to "subwoofer".

Grant Bunter wrote:Do I need to LP the sub?

Yes. Typically it's between 100 and 120hz, depending on how your tops like to go low.

Grant Bunter wrote:Or just crossover the tops at desired frequency and the resultant slope be ok? What slope and pattern do most ppl use?

See above. Slope is generally LR48 (db/octave).

Grant Bunter wrote:EQing: Do most ppl use the DCX as master EQ for system tuning and then DEQ to RTA/Room tune?

Setup: Mixer L R out to DEQ. DEQ to DCX. DCX to amp?

Grant

I have put a DCX in one setup. The output EQs were to make the tops flat and the sub flat. Then used the input EQ for overall contour.

There ya go,

For EQ I use system EQ and 31 band to tune the room. It's probably a lot easier with RTA!

Cheers Gregory and Tom.

Any other responses welcomed gratefully.

Just to check:
Say I have T39's and DR 250's.
For the sub out(s) LR48 at 45hz and LP (so again LR48) at (say) 110hz
Tops out: based on a tops cab tuning of 80Hz: LR48 at 80Hz
Which should strengthen bass response between 80Hz and 110Hz from both subs and tops.

Is it easier to do it all via PC (laptop died a while back, PITA)

I have quite a few posts about setting gain to limit to 35V written down, but need to get this bit sorted first...

You could try that but I think you will find it gets muddy in the bass. The idea of the crossover is to get it over and done with.

You can even set the crossover with a small gap, low passing T39 100hz, high passing tops 110hz, since the response of the sub rises so much through there it negates the crossover slope.

Grant Bunter wrote: For the sub out(s) LR48 at 45hz and LP (so again LR48) at (say) 110hz
Tops out: based on a tops cab tuning of 80Hz: LR48 at 80Hz
Which should strengthen bass response between 80Hz and 110Hz from both subs and tops.

This might be true only if the tops and subs are completely in phase, which they aren't likely to be. The reality is that anything from a big null to the sum effect you expect could happen, because phase is continuously variable.

Thanks Brent.

Any other takers?

You'll need to eq the subs to get them right - more or less reverse the response curve.

Yes it's easier to use a laptop.

You need to limit the output voltage of the amplifier according to the plan.

Thanks Greg
Perhaps you might suggest where I draw my "0" line for bass response...
So I can ballpark some adjustments

Greg Plouvier wrote:You'll need to eq the subs to get them right - more or less reverse the response curve.

Yes it's easier to use a laptop.

You need to limit the output voltage of the amplifier according to the plan.

If I use the S2010 response chart for the T39 in the SPL section will that be reasonably close to a BP102 response curve? I can draw a "zero" line at 100db. Based on that add +2.5 from 45 to 80Hz in EQ to get me in the ballpark do you think?

I looked and, going by the fact that you have 20" cabs, you don't need do any compensating (20"/S3012).

Tom Smit wrote:I looked and, going by the fact that you have 20" cabs, you don't need do any compensating (20"/S3012).

Thanks Tom.
I was looking at EQ'ing, ie mirroring the response curve with EQ to get flat, but based on the S2010 (and/or 3012) SPL chart. I hope that makes sense.

http://billfitzmaurice.info/forum/viewt ... f=12&t=487

Top picture/graph has 20"/S2010 cab and it is at 100db from 50 up to 75hz, and then it rises. Going by that graph, I would pull out a few db at 90hz and adjust the "Q" shoulders pull it flat from 85 to 100hz.

Brilliant Tom!
Thanks, exactly the kind of input I was looking for.


Fired it up today.
Needs a lot of work in the EQ generally, but not worth going there yet as I am using some old 15"/piezo direct radiators for tops.
Once I ironed out some of the mud, my wife said it was awesome. Belting her chest in "like when we saw AC/DC (mind you we were at the other end of the arena then and beside it today lol).
Good grief, so much yet to learn...