MiniDSP vs DCX2496 - Page 3 - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #61 of 75 Old 02-25-2013, 08:09 PM
Advanced Member
 
cookieattk's Avatar
 
Join Date: Jun 2011
Posts: 552
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Liked: 59
Quote:
Originally Posted by andyc56 View Post

The recommendations from that paper have become part of the AES48 standard "Grounding and EMC Standards". There's a site called pin1problem dot com that has links to articles about grounding of balanced systems, including two from the Jensen company (1995 and 1997), both of which reference the Muncy article, though I don't know which specific author wrote them. Muncy showed lots of measurements that if his recommendations are followed, one can inject a large hum current into the shield of a cable in a balanced system and the system will have very high rejection of the hum. One of the articles from Jensen at the above mentioned site is about how to construct the so-called "hummer" that injects that hum current. Systems that direct that ground current through the circuit board, instead of through the chassis, show much worse hum rejection.
Yes, the custom biquad feature is a biggie for me.

dcx is also grounded i believe through the pcb and has much worse noise levels.

u could just buy a 16 block barrier strip slap that sucker right above the inputs / outputs and connect shield to it and ground the strip to the top of chassis now your grounded your pin 1 the way u like it without any real work.
cookieattk is online now  
Sponsored Links
Advertisement
 
post #62 of 75 Old 02-25-2013, 08:20 PM
Advanced Member
 
andyc56's Avatar
 
Join Date: Feb 2013
Posts: 575
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 182
Quote:
Originally Posted by cookieattk View Post


dcx is also grounded i believe through the pcb and has much worse noise levels.

u could just buy a 16 block barrier strip slap that sucker right above the inputs / outputs and connect shield to it and ground the strip to the top of chassis now your grounded your pin 1 the way u like it without any real work.

Aaaaargh! This whole situation is driving me bonkers! biggrin.gif

In the end, I'd like to have an all-analog solution, but do the prototype with a digital setup, so maybe this isn't as bad as I think it is.

Edit: After reading cookieattk's post, I opened up an unused DEQ2496 equalizer (not the DCX2496 crossover) that I had sitting in a closet. I found an interesting thing. The XLR connectors are all mounted on a fairly long, narrow PCB that runs most of the width of the unit and contains only PCB-mount XLR connectors and no other circuitry. Then there's a ribbon cable connecting this narrow board to a completely separate board containing the rest of the circuitry. So it's possible to implement Muncy's grounding approach with this idea. If only the signals from pins 2 and 3 of each XLR connector were sent to the main board via the ribbon connector, and no connection from pin 1 of any of the XLR connectors were made to the main board, then any hum currents circulating in the shields of the XLR cables will be confined to the separate board that holds the XLR connectors and will not circulate in the ground system of the signal processing PCB. If that's the case, it's a very slick arrangement that also eliminates discrete wiring from the connectors via the PC mount approach. I didn't see the connection from this long narrow board to chassis ground, but I assume it's on the back side of the board, and that the main circuit board has a similar arrangement.

I like it. smile.gif
andyc56 is offline  
post #63 of 75 Old 02-25-2013, 10:47 PM
AVS Special Member
 
A9X-308's Avatar
 
Join Date: Mar 2008
Location: Australia; now run by adults.
Posts: 5,246
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 74 Post(s)
Liked: 56
Quote:
Originally Posted by cookieattk View Post

dcx [snip] has much worse noise levels.
Rubbish. Most people set up the gain structure incorrectly and have problems because of this when using it full range. It measures very well.



Analogue out with digital in. yellow stock green with modified PSU. Analog in to analog out is only a couple of dB worse.
A9X-308 is offline  
post #64 of 75 Old 02-25-2013, 10:49 PM
AVS Special Member
 
A9X-308's Avatar
 
Join Date: Mar 2008
Location: Australia; now run by adults.
Posts: 5,246
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 74 Post(s)
Liked: 56
Quote:
Originally Posted by andyc56 View Post

After reading cookieattk's post, I opened up an unused DEQ2496 equalizer (not the DCX2496 crossover) that I had sitting in a closet. I found an interesting thing. The XLR connectors are all mounted on a fairly long, narrow PCB that runs most of the width of the unit and contains only PCB-mount XLR connectors and no other circuitry. Then there's a ribbon cable connecting this narrow board to a completely separate board containing the rest of the circuitry.
The DCX is built similarly.
A9X-308 is offline  
post #65 of 75 Old 02-26-2013, 03:57 PM
Newbie
 
drawbars's Avatar
 
Join Date: Feb 2013
Location: Ashby, MA USA
Posts: 9
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by desertdome View Post

Quote:
Originally Posted by A9X-308 View Post

It has an AES digital in.
It will also accept S/PDIF via RCA on the digital in. I used one for a couple years this way and it worked great.

That's how I'm running, too. I was going to buy an 'S/PDIF to AES/EBU converter cable,' but I determined that most of the ones that are available are just a piece or 75-ohm cable with an RCA on one end and an XLR on the other, tied in an unbalanced configuration. I decided to use a 75-ohm video cable that I had laying around with an RCA-to-XLR adapter. It probably wouldn't work if the cable was 20' long, but at 3' it works perfectly.

Regards,

-BW

Bruce Wahler
bw@ashbysolutions.com
http://music.ashbysolutions.com
drawbars is offline  
post #66 of 75 Old 02-26-2013, 05:59 PM
AVS Special Member
 
zheka's Avatar
 
Join Date: Jan 2007
Location: Chicago burbs
Posts: 1,046
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 16
is there free or inexpensive loudspeaker modeling software that can do shelf filters like the ones used in DCX? or is it possible to fake in WinISD somehow?
zheka is offline  
post #67 of 75 Old 02-26-2013, 06:16 PM
AVS Special Member
 
A9X-308's Avatar
 
Join Date: Mar 2008
Location: Australia; now run by adults.
Posts: 5,246
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 74 Post(s)
Liked: 56
Quote:
Originally Posted by zheka View Post

is there free or inexpensive loudspeaker modeling software that can do shelf filters like the ones used in DCX? or is it possible to fake in WinISD somehow?
Use Unibox to do the modelling. Then there are programs available to make PEQ, LT etc which you save as an FRD file and can be added to the model. I can't remember the URL for the programs but will later when I get home. This is how I do it.

Edit. Found it, but it appears to have been hacked and I get redirected to a Russian medical supply site.
A9X-308 is offline  
post #68 of 75 Old 02-26-2013, 06:25 PM
Advanced Member
 
andyc56's Avatar
 
Join Date: Feb 2013
Posts: 575
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 182
You should be able to do it with the Linkwitz transform in WinISD. I can't find specific documentation on the transfer function of the DCX shelving filters regarding Q0 and Qp, but I suspect they are both 0.707. So in the Linkwitz transform you would enter Q0 = Qp = 0.707. For f0 (the upper corner frequency of the shelving filter), enter the existing -3 dB frequency of the system you're trying to equalize, then adjust fp to a frequency less than f0 to give the desired low-frequency boost. Boost in dB = 20 * log10( f0^2 / fp^2). Then fp should be the new -3dB frequency (now < f0), assuming the Q of the system you're equalizing was 0.707 to begin with.
andyc56 is offline  
post #69 of 75 Old 02-26-2013, 06:53 PM
Advanced Member
 
andyc56's Avatar
 
Join Date: Feb 2013
Posts: 575
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 182
Here's an example of the LT in WinISD. It uses the Dayton 18" Ref HO driver in a closed box having fsc = 35.76 Hz and Qtc = 0.707. I've set up the LT for Q0 = Qp = 0.707, f0 = 35.76 Hz and fp = 20 Hz. This extends the -3 dB frequency from 35.76 Hz to 20 Hz.

Ref_18_HO.zip 1k .zip file
Attached Files
File Type: zip Ref_18_HO.zip (1.1 KB, 4 views)
andyc56 is offline  
post #70 of 75 Old 02-26-2013, 06:58 PM
AVS Special Member
 
zheka's Avatar
 
Join Date: Jan 2007
Location: Chicago burbs
Posts: 1,046
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 16
Quote:
Originally Posted by A9X-308 View Post

Use Unibox to do the modelling. Then there are programs available to make PEQ, LT etc which you save as an FRD file and can be added to the model. I can't remember the URL for the programs but will later when I get home. This is how I do it.

Edit. Found it, but it appears to have been hacked and I get redirected to a Russian medical supply site.

Thank you. I got to the page without problems. Do you happen to know which program of the many listed can model shelf filters specifically? would it be the LT design one http://www.pvconsultants.com/audio/eq/linktran.htm ?
zheka is offline  
post #71 of 75 Old 02-26-2013, 07:17 PM
AVS Special Member
 
zheka's Avatar
 
Join Date: Jan 2007
Location: Chicago burbs
Posts: 1,046
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 16
Quote:
Originally Posted by andyc56 View Post

You should be able to do it with the Linkwitz transform in WinISD. I can't find specific documentation on the transfer function of the DCX shelving filters regarding Q0 and Qp, but I suspect they are both 0.707. So in the Linkwitz transform you would enter Q0 = Qp = 0.707. For f0 (the upper corner frequency of the shelving filter), enter the existing -3 dB frequency of the system you're trying to equalize, then adjust fp to a frequency less than f0 to give the desired low-frequency boost. Boost in dB = 20 * log10( f0^2 / fp^2). Then fp should be the new -3dB frequency (now < f0), assuming the Q of the system you're equalizing was 0.707 to begin with.

Quote:
Originally Posted by andyc56 View Post

Here's an example of the LT in WinISD. It uses the Dayton 18" Ref HO driver in a closed box having fsc = 35.76 Hz and Qtc = 0.707. I've set up the LT for Q0 = Qp = 0.707, f0 = 35.76 Hz and fp = 20 Hz. This extends the -3 dB frequency from 35.76 Hz to 20 Hz.

Ref_18_HO.zip 1k .zip file

Great, thank you. What if the box alignment is not 0.707? would it still be a valid shelf filter simulation and only the -3db point be at a different position than with 0.707 ? Also, DCX provides first and second order slope options for the shelf filters. Is it correct to assume that the LT workaround can only do second order slope?
zheka is offline  
post #72 of 75 Old 02-26-2013, 07:26 PM
Advanced Member
 
andyc56's Avatar
 
Join Date: Feb 2013
Posts: 575
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 17 Post(s)
Liked: 182
Quote:
Originally Posted by zheka View Post

Great, thank you. What if the box alignment is not 0.707? would it still be a valid shelf filter simulation and only the -3db point be at a different position than with 0.707 ? Also, DCX provides first and second order slope options for the shelf filters. Is it correct to assume that the LT workaround can only do second order slope?

Then you would look at the "box" dialog and find Qtc and fsc. Set f0 = fsc and Q0 = Qtc, and set fp to the desired new -3 dB frequency, and Qp to 0.707. Make sure you're neglecting the voice coil inductance when simulating.

I'm not sure what the exact Q values for the DCX filters are, but the measured acoustic data should be far enough from the ideal predicted by WinISD that those errors will dominate over not being able to match the Q values exactly.

Yes, the LT is second-order only. Using the first-order shelf in the DCX could conceivably work better than second-order for some real-world acoustic data depending on circumstances.
andyc56 is offline  
post #73 of 75 Old 02-26-2013, 08:05 PM
AVS Special Member
 
zheka's Avatar
 
Join Date: Jan 2007
Location: Chicago burbs
Posts: 1,046
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 16
Quote:
Originally Posted by andyc56 View Post

Then you would look at the "box" dialog and find Qtc and fsc. Set f0 = fsc and Q0 = Qtc, and set fp to the desired new -3 dB frequency, and Qp to 0.707. Make sure you're neglecting the voice coil inductance when simulating.

I'm not sure what the exact Q values for the DCX filters are, but the measured acoustic data should be far enough from the ideal predicted by WinISD that those errors will dominate over not being able to match the Q values exactly.

Yes, the LT is second-order only. Using the first-order shelf in the DCX could conceivably work better than second-order for some real-world acoustic data depending on circumstances.

thank you very much
zheka is offline  
post #74 of 75 Old 07-04-2013, 10:04 PM
Member
 
SNOT's Avatar
 
Join Date: Nov 2010
Posts: 54
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Hi Guys,

Thanks for all the notes and inputs. I know this discussion has been going on for ages and there is a lot of back and forth...but the big question remains

Which one wins in a head to head SQ setup?

I kind of like the ready XLR on the DCX don't get the idea why they would put phoenix connectors on a ready boxed unit on the minidsp?

Anyway the plan for me is Denon AVR -> DSP of some sort -> amps -> 3way active

Needless to say I am confused as hell. Even started looking at crossovers that does not make sense at this price bracket(for the gear I use). Lets just say I dont want to buy myself a bunch of problems. i need something that sound good and work good even if I need to look at other products and pay more within reason. That being said the battle seems to be between behringer and the mini dsp.

Thanks in advance

uʍop ǝpısdn sı ɹǝʇndɯoɔ ɹnoʎ sıɥʇ pɐǝɹ uɐɔ noʎ ɟı
SNOT is offline  
post #75 of 75 Old 07-05-2013, 12:41 AM
AVS Special Member
 
A9X-308's Avatar
 
Join Date: Mar 2008
Location: Australia; now run by adults.
Posts: 5,246
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 74 Post(s)
Liked: 56
Quote:
Originally Posted by SNOT View Post

Which one wins in a head to head SQ setup?
A properly set up DCX will better the MD in technical measurement, but it's doubtful it's audible. MD has some more flexibiltity using custom biquads. Otherwise it's a wash.
Quote:
Originally Posted by SNOT View Post

I kind of like the ready XLR on the DCX don't get the idea why they would put phoenix connectors on a ready boxed unit on the minidsp?
Because they are small and inexpensive. I still fail to see what the problem is with Phoenix connectors. They aren't difficult to use.
Quote:
Originally Posted by SNOT View Post

Anyway the plan for me is Denon AVR -> DSP of some sort -> amps -> 3way active

Needless to say I am confused as hell. Even started looking at crossovers that does not make sense at this price bracket(for the gear I use). Lets just say I dont want to buy myself a bunch of problems. i need something that sound good and work good even if I need to look at other products and pay more within reason. That being said the battle seems to be between behringer and the mini dsp.

Thanks in advance
I use modified DCXs in the mains and surrounds (all 3 way active) and will use the MD for some of the subs. Either would be fine for what you want.
Another candidate I'm looking at for the mains is the Najda as I'm interested in using the FIR filters and recent bills have forced a DEQX out of my pricerange.
A9X-308 is offline  
Reply DIY Speakers and Subs

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off