Emerald Physics CS2 with modified DCX crossover

mgalusha · « **on:** 10 Dec 2007, 02:18 am »

This is not a full review, just some thoughts on the CS2's when fed by a modified Behringer DCX2496 vs the stock unit.

I spent a few pleasant hours at Mike Garner's (tweekgeek) house this afternoon listening to his system. As an Emerald Physics dealer he had expressed interest in hearing if there were any improvements to be had by using a modified DCX. I wsas pretty certain there would be as I had a stock one on hand to compare my modified unit to when I was working on it.

I don't own the CS2 but since the XO is the same all we had to do was load the profiles into my unit so it was pretty much plug and play. The only other thing that was required was to set the relative levels of the HP and LP sections to accommodate the amps being used, in this case a nuforce on the bass and his mystery amp on the top.

My unit has been modified with the Linear Audio Active analog I/O kit, an improved digital signal path and an upgrade of the caps on the DSP/DAC board. IMO the Linear Audio kit is the best of the currently available options as all volume control can take place in the analog domain, eliminating the need for a preamp and the extra A/D and D/A conversions. I've read some folks don't want to use the DCX as a DAC but in fact if the DCX is used at all one is using it's DAC's as any analog signal is first converted to digital and then back to analog after being crossed over and equalized. Since it will always impose it's signature I can't see any good reason to use an external DAC. Of course this is just my way of thinking and I only mention it so that my reasons for choosing this mod over something like a passive analog stage and preamp are clear.

Anyway, we first listened to the system with the stock DCX and set up as specified in the Emerald Physics directions. It sounded much as I remembered, very dynamic with the lovely OB bass. Oh yes, the source was Mike's Transporter feeding the DCX via the AES/EBU inputs since the Transporter has an AES/EBU digital output. In my opinion the gain of the amps wasn't matched quite right and we ended up lowering the gain of the LF amps a couple of dB and this improved the balance considerably.

After a few songs we swapped in the modified unit, selected the same XO profile and adjusted the gain levels to the amps. Since the modified unit has an analog volume control, we were able to run the digital out of the Transporter at 100%, ensuring we were not dropping any bits using digital level control.

The differences were significant and all positive. All aspects of the presentation were improved. Bass was both deeper and tighter, the midrange had considerably greater clarity and harmonic richness/warmth. Most improved however, at least to my ears, was the top end. The titanium diaphragms in the tweeter seem to be fairly adept at revealing anything in the signal path and can sometimes be a little metallic sounding with the stock DCX. This is not a problem with the speakers, indeed it demonstrates their resolving power. I believe Mike was fairly shocked at the changes. I wasn't since I'd been listening to it for the past few weeks and compared it to the stock one for reference on several occasions.

Just out of curiosity I had brought along my modified and re-cased Squeezebox 2. Recently this received the Aspen Audio/AKSA feed forward power supply module and I was interested in how it would stand up to the Transporter as a digital source. My Squeezebox has been modified extensively, including the digital output per Pat's (Analog Research Technolgy) thoughts on how to extract a better signal from the Squeezebox. In short the modified Squeezebox was preferred by both of us to the Transporter. I was somewhat surprised by this as I expected the Transporter to have an excellent digital section. However it seems the addition of the Aspen power supply has pushed it past what the Transporter can do.

The best sound we had ended up being the modified Squeezebox feeding the modified DCX via a Stereovox cable that Mike provided. I brought along the digital cable I've been using, a fairly standard cable using Belden 1505A coax with BNC connectors. We swapped it and the Stereovox in and out a few times and the Stereovox provided more realism and a cleaner top end. I hate it when that happens as I ended up taking one of these home and have to send Mike a check now.

Once we had all the right pieces in place we had a tough time carrying on a conversation as the music just sounded so damn good we had to stop talking and crank it up. The dynamics, which are awfully good with the CS2's and the stock DCX, were quite stunning with the modified unit when fed by the Squeezebox. I put on a 24/96 recording of John Lee Hooker and the attack of his voice actually made Mike jump and gave me goosebumps. Very cool.

The bottom line for me is that it's possible there are a set of CS2's in my future and IMO if you own a pair of these you need to consider some rework for the DCX as you have not truly heard what these speakers are capable of. And the scary part for me is that I'm not done with my DCX yet, it has a noisy switching power supply that has to go, so it will likely get even better. Hopefully Mike will chime in with his thoughts.

Standard Disclaimer: I have no affiliation with Emerald Physics other than being friends with a couple of their dealers and no affiliation with Jan Didden and Linear Audio.

Mike

zybar · « **Reply #1 on:** 10 Dec 2007, 02:38 am »

Great post Mike.

Sounds like you guys had a lot of fun today.

I am not surprised that modifying the DCX could lead to some significant gains. I had the same types of improvements when I had my TacT 2.2x modified.

Thanks for taking the time to show that the stock CS2's can get even better!!

George

carusoracer · « **Reply #2 on:** 10 Dec 2007, 02:29 pm »

Nice read Mike, sounds likes like a lot fun to be able to play with your toys!

I need to hear these speakers sometime as the lemming effect from the show has worn off and people are really into the OB sound from the Emerald's

zybar · « **Reply #3 on:** 10 Dec 2007, 02:39 pm »

Quote from: carusoracer on 10 Dec 2007, 02:29 pm

Nice read Mike, sounds likes like a lot fun to be able to play with your toys!

I need to hear these speakers sometime as the lemming effect from the show has worn off and people are really into the OB sound from the Emerald's

Come on out to Boston and you can hear the CS2's and the PP150 at my place...kill two birds with one stone! aa

George

TomS · « **Reply #4 on:** 10 Dec 2007, 02:52 pm »

Very nice review Mike. Sounds like it's time to commit to the mods, though I sort of planned that from the start. Thanks again for being the pioneer and sharing your thoughts!

Tom

janneman · « **Reply #5 on:** 10 Dec 2007, 07:09 pm »

Mike,

Thanks for a thorough report. It's feedback like this that helps and motivates me to try to do the best I can.
I was particularly interested in what you wrote about the highs, and you confirm what I heard from several others. A standard reply is that there seems to be much more differences between CD's or downloaded tracks with the new active output board in the DCX, but the synergy with the digital mods is probably what makes it all come together.
I also agree that the next step up is probably coming from an upgraded power supply. I'm working on it!

Jan Didden.

Ric Schultz · « **Reply #6 on:** 10 Dec 2007, 08:44 pm »

Mike,
Very cool.....mods rule!

How were you controlling the volume in each case? Were you using the volume control in the modified DCX and ? with the Stock DCX.....did you eliminate a preamp when using the modified jobbie? Please, more info, thanks.

carusoracer · « **Reply #7 on:** 10 Dec 2007, 08:44 pm »

Quote from: zybar on 10 Dec 2007, 02:39 pm

Quote from: carusoracer on 10 Dec 2007, 02:29 pm
Nice read Mike, sounds likes like a lot fun to be able to play with your toys!

I need to hear these speakers sometime as the lemming effect from the show has worn off and people are really into the OB sound from the Emerald's

Come on out to Boston and you can hear the CS2's and the PP150 at my place...kill two birds with one stone! aa

George

Thanks Goerge,

Sounds like a fun time! I'll have to try and take you up on the offer

TomS · « **Reply #8 on:** 10 Dec 2007, 09:14 pm »

Quote from: Ric Schultz on 10 Dec 2007, 08:44 pm

Mike,
Very cool.....mods rule!

How were you controlling the volume in each case? Were you using the volume control in the modified DCX and ? with the Stock DCX.....did you eliminate a preamp when using the modified jobbie? Please, more info, thanks.

www.linearaudio.nl

Ric Schultz · « **Reply #9 on:** 10 Dec 2007, 09:29 pm »

Tom,
Thanks, I am familiar with the Didden thing and how it works (including schematics).....however, I was wondering how the volume was being controlled when they were using the stock DCX.
Ric

zybar · « **Reply #10 on:** 10 Dec 2007, 09:32 pm »

Quote from: Ric Schultz on 10 Dec 2007, 09:29 pm

Tom,
Thanks, I am familiar with the Didden thing and how it works (including schematics).....however, I was wondering how the volume was being controlled when they were using the stock DCX.
Ric

I am controlling the volume via the Squeeze Box when using the stock DCX.

George

nature boy · « **Reply #11 on:** 10 Dec 2007, 09:52 pm »

Mike,

Thanks for sharing your great review.

NB

Ric Schultz · « **Reply #12 on:** 10 Dec 2007, 09:55 pm »

George,
OK, the Squeezebox has a digital out with volume. Does turning the volume down loose bits?

zybar · « **Reply #13 on:** 10 Dec 2007, 09:59 pm »

Quote from: Ric Schultz on 10 Dec 2007, 09:55 pm

George,
OK, the Squeezebox has a digital out with volume. Does turning the volume down loose bits?

If you turn down the volume too much you will lose bits.

I am not attenuating things enough that I am losing any resolution.

When using a modified DCX, I am running a digital input into the DCX at full output.

BTW, the SB can control volume for the digital and analog outputs.

George

Ric Schultz · « **Reply #14 on:** 10 Dec 2007, 10:11 pm »

George,
So you are only using a few db of digital attenuation (via Squeezebox) when using the stock Behringer? Every 6db of attenuaton looses one bit of info.

JeffB · « **Reply #15 on:** 10 Dec 2007, 10:56 pm »

I though it was possible to run digital into and out of the DCX without any conversion to Analog.
Oh, correction. Now that I think about it, I don't believe there is a digital out.

Russell Dawkins · « **Reply #16 on:** 10 Dec 2007, 11:12 pm »

Quote from: JeffB on 10 Dec 2007, 10:56 pm

I though it was possible to run digital into and out of the DCX without any conversion to Analog.
Oh, correction. Now that I think about it, I don't believe there is a digital out.

Yeah, you'd need three and three DACs.

zybar · « **Reply #17 on:** 10 Dec 2007, 11:44 pm »

Quote from: Ric Schultz on 10 Dec 2007, 10:11 pm

George,
So you are only using a few db of digital attenuation (via Squeezebox) when using the stock Behringer? Every 6db of attenuaton looses one bit of info.

I believe that since the output is higher than 16/44, you can attenuate and not lose any data.

Maybe somebody like Mike Galusha can do a better job of technically explaining things?

I just know that things sound good.

George

Ric Schultz · « **Reply #18 on:** 10 Dec 2007, 11:59 pm »

I believe the Squeezebox is running at 16/44 when outputting a CD to the DCX......if this is so and the Squeezebox is using a normal digital volume control then you would indeed be loosing bits turning down the volume more than 6 db. So, if you are comparing two xovers and one is being fed less than 16 bits (the stock one).....then the comparison is definitely flawed. If, you are only going to be using the Sqeezebox....it really does not matter that the comparison is flawed because the results are better no matter what the reason. But if you really want to see what the new output stage is doing then feeding both Behringers the same bits is necessary......then, of course you would have to figure out some way of attenuating the volume in the stock unit......obviously, something your are not going to do....no biggie, really. The only thing that matters is the results....and I am sure the modded unit sounds way better the way you are using it.

zybar · « **Reply #19 on:** 11 Dec 2007, 12:34 am »

Quote from: Ric Schultz on 10 Dec 2007, 11:59 pm

I believe the Squeezebox is running at 16/44 when outputting a CD to the DCX......if this is so and the Squeezebox is using a normal digital volume control then you would indeed be loosing bits turning down the volume more than 6 db. So, if you are comparing two xovers and one is being fed less than 16 bits (the stock one).....then the comparison is definitely flawed. If, you are only going to be using the Sqeezebox....it really does not matter that the comparison is flawed because the results are better no matter what the reason. But if you really want to see what the new output stage is doing then feeding both Behringers the same bits is necessary......then, of course you would have to figure out some way of attenuating the volume in the stock unit......obviously, something your are not going to do....no biggie, really. The only thing that matters is the results....and I am sure the modded unit sounds way better the way you are using it. However, using an op amp based output stage is not going to give the best results possible.

Thanks for the clarification Ric.

George