Behringer DCX 2496 to prototype active crossover

I'm building a 3 way system (lambda TD12s, PHL 1120, morel supreme 110) and i'm hoping to prototype its response first with a DCX 2496. Once I have a response that I'm happy with, I will build an analog active crossover to replicate it.

Should I be expecting very much change in going from a DSP based system to an analog filter?
 
For what its worth,

I had the same plan but after hearing the DCX I ened up keeping it in my system.. The main thing to remember is that you'll need to atenuate the outputs of the DCX to get the full digital precision. I great way to do this is to use pro amps with gain controls instead of comercial amplifiers.

--Chris
 
Yeah, what he said.

I bought the Behringer with the same notion but as I get into the passive design phase, I see that things are not going to translate perfectly. Maybe the only thing that translates is the crossover point and slope but you still need to measure your drivers, determine the correct passive component values, try to find the ideal passive component values, build, test, repeat.

First the Pros:
- added cost not that great compared to your driver costs
- immediate gratification (you can enjoy your system immediately)
- ability to immediately hear the difference between differend crossover points and slopes
- can be used with future projects.

Now the Cons:
- difficult to integrate in an unbalanced signal path.
- ideal sound quality config may not fit your needs
- does not measure your drivers or determine equivalent passive component values

Ideal config would be digital into the DCX with the DCX feeding its outputs into a 6 channel volume control before each amp. Pretty much eliminates the ability to use with home theater setups.

Less ideal config would be use a high-gain preamp feeding the DCX and then feed the DCX signal through an attenuation network before the amps. The idea is to increase the ratio between the input signal and the unit's inherrent hiss.

Read this thread to start and search on DCX2496 and read those as well: http://www.diyaudio.com/forums/showthread.php?s=&threadid=55871&highlight=

That said, if you can deal with the hiss (eliminate or ignore) then I'd say go for it. It's fun to play with and educational to boot. But you'll need some sort of measurement software to get it to sound its best. I've used TrueRTA and that's been enough to get something enjoyable to listen to. But it's not the best type of tool to use for reasons I can't explain here...
 
LOL,

UltraChrome and I seem to post on all the same threads ;) That was a pretty good pros/cons argument above.

The only thing I would add is that if you use pro audio amplifiers you don't have to worry about the attenuation network after the DCX or the balanced to unbalanced coversion.

The best possible solution is to drive digital to the DCX and then analog to amplifiers which have adjustable gain. My personal setup looks like this :

CD-player -> SRC2496 (digital 16bit/44.1Khz)
** upsampled digitally with dithering in SRC **
SRC2496 -> DEQ2496 (digital 24bit/96khz)
** Digital Room Correction Applied in DEQ **
DEQ2496 -> DCX2496 (digital 24bit/96khz)
** DSP Crossover and D/A conversion **
DCX -> 3x A500 reference amplifier

This sort of configuration allows you to use the maximum digital dynamic range of the DEQ/DCX maintaining the highest signal to noise ratio

--Chris
 
I already bought an active filter board and have a power supply ready. The reason i don't want to use the DCX permanently is because I hear a lot of mixed reviews about it. I'm paying a fortune on my drivers so im not going to sacrifice anything on my xover. I also don't have a balanced source or balanced amplifier inputs. Will that be detrimental to the S/N?
 
Balanced interconnects are not essential, but they do help with noise rejection. The largest improvement you can make when using the DCX is keeping the signal levels on the inputs/outputs as close to clipping as possible.

As far as analog active/digital active crossover you'll see opinions on both sides saying which is superior. IMHO the DCX is so ridiculously better than any passive crossover I can't believe I've lived without one for so long ;)

Don't take my word for it though, listen to both see what you like better. In the end what really matters is what YOU like better not what anyone else does.

--Chris
 
So your target is an active three-way? What active boards are you using?

Since you have them already, you might want to give it a go. It shouldn't be too hard picking crossover points from the datasheets of those woofers. The biggest difference in sound quality that I've uncovered with the DCX was with crossover slope. I tried LR48 last night after trying 12 and 24 and the difference was pretty obvious.

If I was building a fully active system from scratch, I'd likely build it around a DCX and then later upgrade to a higher resolution digital system that supported better filters and room correction features.
 
lambda TD12s, PHL 1120, morel supreme 110

This design will be very easy to tune as there is less problems
with integration than other common designs. It will be
an excellent system if you pay attention to fabrication details.

The reason i don't want to use the DCX permanently is because I hear a lot of mixed reviews about it.

People in cyberspace have a way to scare people away when
the pros outweigh any negatives by a HUGE margin.

Don't worry about the DCX sound quality, it's excellent without
mod, and excellent if you choose the analog pathway. The
feature rich DCX can only make your system more interesting
because you will be able to tune it for whatever listening mood
you are in vs. using passive crossovers which will only give you
one sound <-- that's ok too. :cool:
 
I'm using active filter one boards.

My plan was to:

1. Prototype with DCX. Find optimal filter slopes/notches/delay.
2. Implement equivalent filter using the active filter one boards.
3. Either sell the DCX or keep it to prototype future speakers.

I understand that active is better then passive, but I'm not convinced whether DSP is better than analog. Up to this point, I was convinced that the DCX is more convenient do to software implemented transfer functions, but analog has it beat in signal integrity. I guess the only way I can find out is if I do them both.
 
That plan sounds pretty sound.

Behringer or not, you're going to need a measurement mic, mic pre, and measurement software.

Theoretically, feeding the Behringer an analog signal puts it at disadvantage. The Behringer's big advantage is its convenience.

I sound negative but I don't regret the purchase. Just annoyed by hassle of interfacing between pro with consumer gear. Essentially, getting it to work quietly with the amps I already had involved essentially another DIY project.
 

AnthonyPT

Member
2004-10-29 9:23 am
HI


The Behringer DCX2496 does seem to need a full
signal to get the most out of the unit.I came
across this 6 channel remote volume kit. It uses
LM1973n volume chips and then goes to TL072 output
buffers. The TL072 are easily updated with better
chips but if the LM1973Ns are ok it would make a
very neat solution to the DCX2496 volume issue.
Since it is a kit it pretty cheap at AUD$199.
It is a magazine design from Siicon Chip hear
in OZ. There may be some others that do
just the boards but here are URL about
the kit.
At the moment I am building a 24db/octave
3 way analogue crossover for my dipole panels.
Plan to migrate to the DSX and this 6 channel
volume control when funds become available.

regards

AnthonyPT

http://www.altronics.com.au/index.asp?area=item&id=K5600
http://www.siliconchip.com.au/cms/A_30608/article.html
http://www.decibelhifi.com.au/webcontent10.htm
 

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Just annoyed by hassle of interfacing between pro with consumer gear. Essentially, getting it to work quietly with the amps I already had involved essentially another DIY project.

I'm running the Roland M1000 as the home audio interface to
proaudio and it's working well sonically. This method was recommended
on forums as the Roland provides the digital volume control. I did have
to buy an inline transformer to convert SPDIF to AES/EBU, but it didn't
cost much.

DVD player digital output -> Roland digital input -> Roland digital output -> impedance transformer -> DCX digital input -> amps

I also tried analog pathways using analog crossovers but the
DCX has more features that allowed better tuning to give me better
sound. I also tried the analog paths on the Behringer and Roland
and there is no sonic difference to digital paths.

The Roland is neat. It has one set of analog inputs and four
digital inputs, it's a mixer. I can feed the DVD player analog outputs
into the Roland and ALSO feed the digital output of the DVD player
into the Roland digital input and have the ability to choose which
pathway to use. You can compare analog to digital paths in real time
and I've been switching between the two and can't hear a difference.

I want to do another test where I will add more conversions
to see if the golden ears can detect all these conversions.
I'm going to do this for fun.

DVD player analog out [D/A] -> Roland analog in [A/D] -> Roland
analog out [D/A] -> DCX analog in [A/D} -> DCX analog out [D/A] - amps.

Five conversions, I wonder if the they can pass the blind test. :)
 
That Roland does sound interesting especially considering that all my current analog sources have digital outputs.

I did some testing with my attenuators. Set them up to greater than >24dB. How much more than that I don't know. I didn't have a 750R resistor so I used 540R. See Kuei Yang Wang's post.
Still can hear hiss at 8+ feet.

Swapped my newly rebuilt tube pre for a solid state. Hiss still there.

Reconfigured the DCX as 2-way replaced the mid/tweet with a pair of Dennis Murphy baffle-step-compensated MB20s. Efficiency in the 80's? This fixed the hiss. Can only hear it within a foot of the speaker.
 

mac

Member
2003-05-26 1:49 am
Seattle
thylantyr said:
Just annoyed by hassle of interfacing between pro with consumer gear. Essentially, getting it to work quietly with the amps I already had involved essentially another DIY project.

I'm running the Roland M1000 as the home audio interface to
proaudio and it's working well sonically...

Another alternative is to use the Bill Dipoala DCX2496 boards. His output board allows you to use any opamp of your choice (AD823) with either pro or consumer level (RCA or XLR) outputs. In addition, it has a lot of other optional features including IR volume control, digital volume LCD display and Toslink input.

As a bonus, his boards fit neatly inside of the DCX.

I've been using one in my system for several months and am very happy with the sound and overall operation. Btw, it replaced a DEQX PDC. :up:
 
ultrachrome said:
I did some testing with my attenuators. Set them up to greater than >24dB. How much more than that I don't know. I didn't have a 750R resistor so I used 540R. See Kuei Yang Wang's post.
Still can hear hiss at 8+ feet.

24db of attenuation is only 8 bits of dynamic range increase inside the DCX.. The real test is how many LED's where lit on the output channels during playback? Unless you can get all of them lit, just below clipping you're loosing lots and lots of precision.

--Chris
 
DIY_newbie said:


24db of attenuation is only 8 bits of dynamic range increase inside the DCX.. The real test is how many LED's where lit on the output channels during playback? Unless you can get all of them lit, just below clipping you're loosing lots and lots of precision.

--Chris

There is alot of comedy in audio.

Branwell posted this message;
http://groups.yahoo.com/group/DCX2496/message/415

From: Branwell <[email protected]>
Date: Thu Jun 16, 2005 1:08 pm

Subject: Digital Volume Control for DCX based systems

Hello,

I have an active setup with the Behringer DCX 2496 crossover, and like most
home users, have had to address the volume control issue and level matching
for non pro amps.

The setups I have tried are:

1) CD ( digital out ) – DCX ( analog out ) – DACT 6 channel pot - Amps
2) CD ( digital out ) – DCX ( analog out ) – VCA based 6 channel pre –
Amps

Both of these setups dealt with the level matching and allowed good volume
control.
Of the two, I preferred the sound of the active volume control as opposed
to the passive pot. A little more dynamic and sets up a more 3 dimensional
sound stage.

To try something different, recently I got a Roland M1000 digital mixer and
am using it to act as a volume control.
http://www.rolandus.com/products/details.asp?catid=12&subcatid=49&prodid=M-1000

CD ( digital out ) – M1000 ( digital out ) – DCX – Amps

While this setup does not deal with the level matching issues ( Can add L
pad resistor setups in the interconnects between the Amp and the DCX ), it
does deal with the volume control.

Compared to the two analog volume control setups, the Digital volume setup
sounds more dynamic, more detailed and interestingly, more musical.


While this was fairly close to being apples to apples, the variables include:

Passive Volume Control:
Behringer to Pot – Single ended.
Pot to Amps – Single ended.

Active Volume Control:
Behringer to VCA - Balanced
VCA to Amps - Single ended.

Digital Volume Control:
Behringer to Amps – Balanced.

The amps I have will take single ended inputs or balanced, so there was not
an amp change.

Could the balanced factor account for the perceived sound quality increase?.
Perhaps, but either way, for those that like the idea of a Digital volume
control, the M1000 is a viable solution.



////


I find it assuming that the Roland setup sounded better in spite
that it has three gremlins that people fear;

A. Upsampling
B. Roland digital attenuation, loss of bits.
C. Not driving the DCX to full lit LED's at low - medium volume levels.
 
Thyl,

LOL, see my post above, what really matters is what YOU like other people's opinions are just enjoyable reading ;)

I need to look at the roland's specs, but I'm assuming the digital volume control is more advanced then a simple bit shift operation. If the volume control adds some compression as it attenuates this would preserve some of the low level information, even enhance it at lower volume levels compared to either of the other post dcx volume controls. This would cause the sound to be more "dynamic" as it preserved some of the low level information...

Guess I should go find a spec for that Roland and check it out, untill then its just a guess ;)

--Chris
 
DIY_newbie said:
Thyl,

LOL, see my post above, what really matters is what YOU like other people's opinions are just enjoyable reading ;)

I need to look at the roland's specs, but I'm assuming the digital volume control is more advanced then a simple bit shift operation. If the volume control adds some compression as it attenuates this would preserve some of the low level information, even enhance it at lower volume levels compared to either of the other post dcx volume controls. This would cause the sound to be more "dynamic" as it preserved some of the low level information...

Guess I should go find a spec for that Roland and check it out, untill then its just a guess ;)

--Chris

http://www.htguide.com/forum/showthread.php4?t=14926