dcx2496 shakedown

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Just a self-congratulatory post to report that I just got my DCX2496 up and running. The only tricky part was realizing the outputs were muted by default.

I don't have a serial port on my laptop so until I can get a usb-serial adapter, I've been dinking around with the front panel controls. I'm suprised to say that without cracking the manual, it's fairly decent as far as setting crossover points/slopes and levels, although I'm using the defaults.

I hooked it up to my Feandil-linearray-killer which comprises of a TB-871, Audax PR170M0, and an 8" MCM woofer. The amps are a BrianGT rev A gainclone, AKSA 55, and Adcom 545ii, respectively.

I can honestly say my CDs have never sounded this way before.:dodgy:

The PR170M0s have been waiting for Fountek NeoPro5i's that arrived this past Thursday and for a quartet of Lambda Dipole12s that will arrive this coming Wednesday.

Before the DCX arrived, I hadn't actually tried to get all those woofers working together.
 

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cmckasty

Member
2004-08-27 2:51 pm
S.C
details on hook up?

Hello,

Do you mind if I ask how you have it all hooked up. Do you use a standard home pre amp. Are you using rca to balanced simple wire conversions or are you boosting the pre amp signal? Do you experience any low level hiss. I am asking to find out because I have that problem at low volumes. I have heard of passive volume controles but am unsure how to implement them.
Any help you can offer will be appreciated.



Thanks, Chris
 
source > preamp > DCX > amp

I made a simple rca to XLR cable by bridging pins 1 and 3 per the Behringer manual (p20).

Yes, I have the hiss using it with standard home preamp/amps.

I'm not too worried about it at the moment as I plan to use it to prototype the final crossover which will be active between the woofer and mid/tweeter and passive between the mid and tweeter. So the intent is not to leave it in the chain for long.

If I wanted to keep it in the loop, I'd probably sell the DCX and step up to the Rane RPM26z which can handle volume control.

I know there are some folks working on 6-channel volume controls but based on my own remote control 2-ch kit purchases, the cost can get pretty high so you could end up getting close to the Rane pricepoint. With the Rane, I'd likely dispense with the preamp altogether.
 
Fellas,

Try breaking the pin 1 to 3 connection on any adaptors or cables you have on the DCX outputs. This will decrease the gain in the analog output section of the DCX and force the signal 6db higher relative to the noise. You can take this even farther by adding fixed attenuator pads on the DCX outputs.

A six-channel volume control is the way to go ultimately (they don't have to be expensive,) but in the mean time that should help you.

Cheers,

Davey.
 
Just spent a few minutes with a mic and the free version of TrueRTA. Obtained a better match with my super efficient Audax mid. EQ'd a peak at 15k and below 200Hz to deal with my woofer rolloff. Then plugged the mic into the DCX and did the time-align thing. All together it made a world of difference. I could very easily listen to this all evening.

Someone posted a Rane article that showed connecting pin 3 to black and pin 1 to the shield when going from RCA to XLR which would be my input side.

On output from XLR to RCA, they show pins 1 and 3 bridged and connected to both shield and black.

Is that what you are talking about?
 
Yes, that's exactly what I'm talking about. Don't make the connection between pin 1 and pin 3 on the DCX outputs. On the inputs it doesn't matter.

There are dozens of threads on this forum related to the DCX and its various idiosyncrasies for hifi use. I would suggest reviewing them all to pickup a bunch of good information.

Here's just one:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=55871&highlight=

Cheers,

Davey.
 
Davey, I'm confused. What you just wrote is exactly opposite of what the Rane document seems to be saying.

17) RCA output (source) to a XLR male input (DCX) has 1 to shield and 2 to red, 3 to black.

6) XLR female output (DCX) to RCA input (amp) has 1 to shield, 2 to red, 3 to black with 1 and 3 bridged.


Thanks for the thread pointer. I'll check it out. I did go through several DCX posts before I bought it but some details didn't stick. The hiss isn't horrible but if I can fix it relatively easily, I will.
 
Davey said:
Yes, I understand this is different than what is recommeded by Rane and Behringer.
I don't know how much clearer I can say it....don't connect pin 1 to 3 on the outputs. Pin 1 goes to your RCA shield and pin 2 goes to the RCA center. Pin 3 is unused and unterminated.

Davey.

Davey,

Did you see a noticable improvement by doing this? I had it wired the way it was described in the manual and I was pretty happy with the sound. After reading everyones comments I decided to wire it the way you describe. Now I feel like the noise floor is louder than it was the other way. I can hear the "crackling" at my seated listening position during quiet passages, I don't think I was able to before..
However, I might just be listening for it more now than before.

--Chris
 
I hooked it up to my Feandil-linearray-killer which comprises of a TB-871, Audax PR170M0, and an 8" MCM woofer.

What does the Feandil speaker sound like compared to this one? ;)

The PR170M0s have been waiting for Fountek NeoPro5i's that arrived this past Thursday and for a quartet of Lambda Dipole12s that will arrive this coming Wednesday.

Cool, I see that you are indeed using the design I recommended
to you, the use of that pro ribbon and the Lambda woofers.

Why do you trust my recommendations for your design and at the
same time make a joke about the Feandil design ? Do you know
who recommended the use of the horn and midrange in the Feandil array? ;)

Here is a the Feandil array conceptual CAD drawings, how did
I get them ;) /hehehe

http://home.pacbell.net/lordpk/misc/Feandil-2.GIF
 
I will post one off topic subject to 'clear the air' about the Feandil vs. McIntosh array comments.

Remember, the McIntosh array is about $20,000 US.

Here is what Jim Griffin said about the design.

Actually the Mac design isn't too shabby. If you look at the owners manual it gives you details like driver spacings, line lengths, crossover frequency, etc. so you can defer a lot about this array's theoretical performance.

The woofer and tweeter line lengths are long enough to enable most any normal listening room to be in the near field. That is a good thing.

With the side by side mids the concern is to have them spaced close enough and use a low crossover frequency so that any M to M (side to side now) would be minimal. This would minimize any off-axis nulls in the horizontal dispersion in the frequency range covered by the mids. This spacing is 6.75" (one wavelength for the M to M centers is 2008 Hz and cncellation would occur at twice that frequency) and the crossover is at 1700 Hz.

The side by side mid-woofers yield symmetrical horizontal dispersion radiation and minimizes any lobing assocatied with the low order (2nd and 3rd) specificed crossover slopes. The tradeoff that the designer has to consider is the small diameter of the mids (closer M to M spacing) and low crossover frequency that would be dictated by this side by side configuation. The smaller mids would also limit the array's lower frequency extension as it does in this design.

The vertical M to M spacing is on 4.5" centers (one WL is 3013 Hz). With the crossover at 1700 Hz you should be free from comb lines even with the second and third order crossover slopes. The T-M spacing is 3.375" (one WL at 3616 Hz) so again with the low crossover you will maintain good dispersion as sound transitions from mid woofer to tweeter lines.

I'm troubled by the tweeter to tweeter spacings as anyone who has read my white paper would understand. The center to center spacings for the tweeters is 2.75" (one WL 4931 Hz and two WL 9863 Hz). Hence, you'll have the first cancellation at 9863 Hz and vertical axis comb line effects in the upper octave (10-20,000 Hz). Likely the tweeter line sensitivity in the upper octave will also show a downward slope so that the crossover would have to attenuate the lower part of the tweeter band to flatten out the overall band. Bottom line is that the tweeters are too far apart to cover the upper ocatve without comb lining and associated sensititivy reduction.

You know I really like a line of planar or ribbon drivers instead of dome tweeters which would alleviate these tweeter line issues. You can improve this design by spacing the tweeters closer but it would require more drivers and even then you really need to get the center to center spacing within 1.35"--preferably less than one inch.

If I were doing a design with dual rows of mid-woofers, I would use ribbon tweeters and crossover low enough to minimize the side by side mids effects as done by Mac. The keys are the low crossover frequency and the close spacing between the mids. The ribbons would be able to alleviate the dome tweeter issues assocaited with this design.

Jim


http://audioroundtable.com/ArraySpeakers/messages/495.html


You folks assume because it has a McIntosh name the design is without flaw. Anyone can see the flaws of the design and DIY'er
today that want to build a serious line array wouldn't use that
McIntosh recipe.

For $20,000 US, I think the design should be better than
isn't too shabby.
 
Re: Re: dcx2496 shakedown

thylantyr said:
Why do you trust my recommendations for your design and at the
same time make a joke about the Feandil design ? Do you know
who recommended the use of the horn and midrange in the Feandil array? ;)

My joke wasn't about the design. It was about the individual. I was impressed with the magnitude of the project. Less impressed by the attitude.
 
Re: Re: Re: dcx2496 shakedown

ultrachrome said:


My joke wasn't about the design. It was about the individual. I was impressed with the magnitude of the project. Less impressed by the attitude.

LOL, I was about to respond to this post as well ...

Thylantyr, I was not trying to disrespect you or your work.. In fact, I thank you for the suggestions on my own project. I believe that Feandil suffers from one of the oldest problems in the business world :

Great product, terrible marketing... ;)

--Chris
 
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