Here are reviews of the K-Stereo and User reports.


Review of K-Stereo Processor in: Tape Op Magazine #68, December 2008

Reprinted by permission.

By: Garrett Haines of Treelady Studios

Algorithmix. Chromium Series K-Stereo plug-in. Algorithmix, in conjunction with Bob Katz, has released a software incarnation of Digital Domain K-Stereo, a patented process that can extract ambience and depth from existing recordings, allowing for post-mixdown adjustments. The hardware version was reviewed in Tape Op #45.  Check out your back issues or the manufacturer's website for more details on the process.

To my ears, the software sounds nearly identical to its hardware parent, but has the added benefit of multiple instances and a graphical user interface. According to the design team, the plug-in uses double-precision 32 bit (64 bit total) floating-point arithmetic, and the box uses 32 bit float. Both run the same exact algorithm. And while the original unit was ergonomically straightforward, having all of the controls available at once---plus the visual of the width and depth fields---makes the plug-in a wonderful incarnation of the original.

I tested the plug-in extensively in an attended mastering session. We all know that things tend to break when a client is present. I was able to shift settings during playback; bypass and enable the plug in; and bring up numerous instances without any problems. Like the original I was able to use K-Stereo to give a track that special sparkle that was missing or to bring out perceived space on a track that sounded narrower than the rest of the CD. One word of caution---depending on the setting, the K-Stereo process can make your average level sound louder to your audience. It may be necessary to adjust your gain staging in other areas of the chain; otherwise, the K-Stereo-processed track might jump out.

If you have ever had the pleasure of visiting a well-appointed woodshop, you'll encounter specialized tools that allow a master craftsman to handle special requests. Mastering engineers are in a similar situation. Sometimes there are requirements that can't be fudged or simulated. The proper tool is necesary. The K-Stereo plug-in is such a tool. This is not an effect that you should use on every song, but when you need it, there is nothing that comes close to sounding like it.

From: Ron Kurz (November 2004)
Switzerland, HARDstudio

Hi Bob,

The K-Stereo box is back in the mastering studio now, and I've already used it on two masterings - what can I say - it's wonderful! Here in the studio, I can hear the different K-settings much better, so the imaging really moves a big step forward or whichever direction one chooses, but I also love the EQ on it as well: very very nice indeed! I've also just acquired a Crane Song HEDD 192 and those two boxes together are like wowza! But, like I've said, I've only gotten started, so there is a lot of experimenting and trying out ahead of me - any tips on where in the mastering chain these two units work the best?

Once again - great tool! (I haven't heard from the recording-mobile unit guys yet, but you'll definetly hear from me if I do...)

From: Ron Kurz (November 2004)
Switzerland, HARDstudio

Hi Bob,

Sorry for not getting back to you sooner. When the box arrived I made sure it was rigged for 220V (which it was, btw). But since I didn't have anymore time to try it out in the studio, I took it with me to a 15 day music festival, where I do all the mixes for broadcast (tv, radio & internet) from a mobile studio. I patched it into the main bus, where I use a TC6000 as master limiter/compressor: in a nutshell: the result was AMAZING! We had artists like Al Jarreau, Ronan Keating and Lionel Richie, which made for a great input, but to be honest, I did not expect the effect! I would only turn it on AFTER all the sound checks, as not fool myself. I mix everything, on the fly, direct to stereo, and since the mixes are meant for broadcast - due to the nature of broadcasting - I have to limit the dynamics quite a lot, and it's was amazing to still hear everything in 3D' when listening back the next day in the video truck, and even more astonishing was checking the streaming audio over the internet - It really maintained the sense of depth! Fantasic! I ended up using the K between +1 and +2 wid/deep and used the EQs for slight tweaking...

This K-Stereo is meant for my mastering studio (that is mainly what I do when not live recording) - but with the above experience, I'm now trying to convince the mobile units here to look into getting one for their truck as well (specially since the dollar is at an all time low for us)...

So as of next week, I'm back at mastering and i'll gladly give you some feed-back from there, even though I'm sure it will be more than positive!

From: Trey (April 2004)

Thank you for sending that mastering box out so quickly. It is truly an amazing piece of gear. As a matter of fact, I would go out on a limb and say I don't think I have ever heard anything like it. Believe the hype! This thing rocks! I do a lot of hip hop these days and to my surprise, it even brought out subtle ambience in that genre of music. It's like Viagra for mixes! Thanks again, and please be sure to thank Bob for me. Also, please keep me on a mailing list, should you folks have other great pieces of gear or even books that I might be interested in.

From: Benjamin Maas (April 2001)
Fifth Circle Audio
Los Angeles, CA

My colleague (Jonathan Marcus of Orpharion recordings here in LA) just purchased one of these miracle boxes and I borrowed it this weekend for a couple of my projects...

The thing seriously saved my tush. I had a jazz recording that I made that did not come out as well as planned... (Big show, No sound check, artist didn't want to pay for multi-tracking, etc... Long story...) I had some issues with some of the imaging and levels, particularly with the vocal being a bit low.

In the mastering of this show, I broke just about every possible rule I've ever personally set for taste to rescue the recording... Through a combination of the DD-2, some frequency-dependent compression, EQ, and some limiting, I made the recording listenable (still isn't great, but I can't fix the mix). The DD-2 enabled me to bring out the center a bit in the recording, but still maintain a relatively full ambient sound around the rest of the recording.

Many of my personal tools are still pretty low-tech and certainly not "mastering quality" in the level that most of you out there work, but using the DD-2 was a pleasure.

When Jonathan and I tested the box, we put all sorts of music through it and were very impressed... It ranged from orchestral recordings to early music to jazz to... In every case, we were able to open up the sound without any artifacts. There is enough of setting that you can make it work for just about any recording.

I highly recommend any of you out there give this box a try...

To: Benjamin Maas (April 2001)

Hi, Benjamin. I really want to thank you for your incredible story about the DD-2! I'm filing it in my "good words" email folder and hope that you may permit me to use it some time.

As you may know, word of mouth is about the only way we're presently getting word about this box, because we're a small company and can't yet afford a real marketing campaign.

You've made my day--and my week!

Take care and thanks again,

Bob Katz

From: Michael MacDonald (November 2001)

I've just had the opportunity to audition a beta version of the new Digital Domain DD-2 K-Stereo Processor. This is the ambience recovery box Bob Katz has been hinting about for the few months.

Several years ago I hired Bob to master a blues project that I had produced, recorded and mixed. Although I have been mastering my own work for many years I decided that the project would be best served by someone who not only had great "ears" but could also be more objective than me, since I was so close to the project. Bob was someone I knew very well, highly respected and completely trusted.

I flew to Orlando and went to work with him in his studio, Digital Domain. Towards the end of a very successful collaboration of my desires and his skills he turned to me and said "I want you to listen to something I've been experimenting with." He then proceeded to play back one of my mixes through a crazy patch that I had never seen before.

The mix that I had known so well now seemed a bit more alive and focused but not in any way I could exactly put my finger on. It was not brighter or louder but it seemed bigger and clearer. It did not sound like he was adding EQ or compression.

What IS that? I wanted to know. Bob was calling his process "stereoization" and explained that it was an idea he had been thinking about for many years and now was beginning to use it on projects he was mastering.

Over the next few years I'd constantly try to get him to reveal his secret because I had never heard anyone else do anything like it and I wanted to start experimenting with it as well. Wisely, he kept mum, dropping a few subtle hints as to where to begin my inquiry as he continued to refine his technique and make his clients very happy.

Several month ago we spoke and he told me that he had made a major break through in his idea and was thinking about marketing a product using his new found knowledge.

"Great!" I said, "Please let me play with a beta version when you have it ready."

It arrived two days ago, which was perfect timing as I was just finishing mastering a rock project that was pretty well recorded with real drums and guitars but had been recorded with Pro Tools and had had a lot of processing done to it before I received the mixes. Fortunately they were 24 bit files.

Up until Bob's box arrived I had felt that I had done a good job and the master sounded much better than the raw sound files. Although I was able to help it with some tube EQ, reverb room sound and some analog peak limiting, the mixes still bothered me a bit because they still sounded a bit crowded and tight. Increasing the S portion of the M/S signal didn't really help either.

I plugged in Bob's box and started to play around. Almost immediately I was able to obtain the kind of result Bob had demonstrated years ago. Hey, this is great! Turning the control knob even further I was able to open up the mixes even more.

Everything seemed to now be in a more definite place, background vocals seemed clearer and I was able to hear more of the layering as clear, definite parts, not a obscure wash. Drums had more depth as I could hear the room that they were recorded in.

Everything seemed to be clearer and warmer at the same time. But not brighter or darker. The tracks sounded louder but the meters told me that the box was not adding any gain. Odd, but very cool.

I then bypassed the effect. The mix dropped back between the speakers and lost the feeling of life and air.

Yea, I know, this is beginning to sound like ad copy. It isn't supposed to. Almost all "effect" boxes I shun as I do not like gimmicks. This box isno gimmick. It simply allows you some control over the ambience from the programand allows you to manipulate the ambience without changing the tonal spectrum or balance of the mix.

There is a lot more that I have not even begun to touch upon, like the great EQ section designed by Glen Zelniker or the POW-R dither algorithms that are included. I guess this rant has gone on long enough.

Bob, great box! Brilliant! Good luck getting it back from me!

From: Andy Gauthier (March 2001)

Dear Bob:

Congratulations! I've just used some files passed through your K Stereo Processor. They were DAT copies of a cleaned up LP done by Brian Peters via Sonic 1.5 HD. The clean up was fine (Brian is excellent at such things) considering the dreadful condition of the 1974 Melodyia (yes Melodyia, so you can imagine) LP.

However, I had NO idea that it could be made to sound so good via your KSP. I am extremely impressed with the overall sound, especially the upper octaves where I heard the greatest difference from the source, (i.e. CLARITY) the stereo depth, and the brilliance of John's dither. Of course, I am one of John's greatest fans I own as much Millennnia gear as I can afford. YOU did an amazing job of exactly what you claim in the first page of the manual. It IS bigger, wider, clearer. The voice (it is opera) is virtually etched out of what was crap. I don't tend to go overboard about audio gear, I have to hear something that raises the ante right away to be impressed. Needless to say the KSP did just that.

Unusually (ha ha), I don't have the money now, but may have in the next few months. (The winter sucked and it all went happily to the 6000 which is doing wonders as well.)

So, the vital questions. Do you sell the box directly, or is it done via a dealer? If you sell directly how much will it set me back and are you backed up in production? If via dealership, who do I call in the New York area?

Bob, I heard the difference in .5 second. I want one the moment I can afford it.

With all sincerity, you've done a great service to the audio industry by working so hard and with such dedication to come up with as nearly a perfect product as I think is possible. Again, congratulations.

From: Rob Gwynn (May 2001)

Hi Bob,

It's hard to know where to start in any discussion about the merits of the K-Stereo processor...partly because, on one hand, it achieves what other processors cannot and, on the other hand, it is seemingly subtle (on first listen). It is definitely a "polishing" tool that will be of use to those who aspire to great recordings and that will probably be viewed as too subtle to bother with for those who are satisfied with less. Thank you for sharing this amazing achievement.

I started by trying recordings at both extremes first, one that was TOTALLY dry (bordering on anechoic), recorded on a college theatre stage and one that was too generous in (complex) reverberation. The dry recordings remained dry,with perhaps just a little increase in breadth and depth. The reverberant recording already had quite a bit of space around the instruments and, while I could hear the effect of the processor, it didn't really contribute anything new to the resulting sound. The recordings that seemed to benefit the most were those that had adequate reverb but that could have used more breadth and depth of the sound stage. In these cases, the resulting sound had increased clarity (apparent) and sweetness. I used various commercial recordings as well as a few of my own. It became a game to see how little K-Level I could use and still hear a difference...this for the purpose of learning how much is "enough" and how much is "too much." In most cases, K-Levels of -3 to -4 were still audible. What is nice is that recordings that have sufficient reverb benefit from the K-Stereo processor without having to add reverb, such aswith the Sony, where with one risks creating a "box within a box" sound. I have always resisted the notion that it's better to have too little reverb because one can always add some later; the acoustics in the original mix often don't sound as convincing after melding them with an electronic reverb.The K-Stereo processor relieves
this dilemma.

I have a couple of suggestions regarding the manual, though I realise it is still evolving:

1. Some kind of technical specifications page might be where the voltage selector is mentioned, for example (that is just an example...I'm not giving you a bad time about the 230V setting!).

2. It would be helpful if you went into more depth on the differences between the four basic settings (wide, wide/deep, small, small/deep). By this I'm not suggesting you "give away the store" as to what is going on with the algorithms, but enough that the user has an idea of what to expect and a suggestion as to the application of each algorithm. One question that came to my mind was how the breadth and depth were changing with the K-Level, i.e., aspect ratio (if it makes sense to talk in those terms).

I will no doubt think of other things and will email you as they come to mind.

For the moment, I will continue to experiment. I already know that I am going to use the processor on my next two re-releases. They were both decent recordings to start with, but will at least benefit from some EQ and the K-Stereoprocessor.

That's about it for now. The processor is already mounted in the rack and, since I used one-way screws, I guess you'll just have to send me an invoice!

From: Jürgen (April 2001)

Hello Bob,

After a few days of using I can say, a very naturally sounding process and again very good shelving eq's. A have a question about the K level. Can you explain me how the + and - settings are working, I here the difference, but what is really going on? Today I had a mastering with piano and a solo singer and the settings worked very well.

From: Tony Faulkner (January 2001)
Green Room Productions
London, England
Engineering Classics
High Resolution Digital Audio and Digital Video

Hi Bob,

Thanks for shipping the processor. It arrived ok.

I am off to Kuala Lumpur tomorrow for sessions over the weekend. The unit has gone off to Ray Staff and Bob at Whitfield Street while I am away. Simon at Chop/Sanctuary will have a try a bit later too.

Interesting box. Is it upgradable with software as you do development? I'll have a few suggestions. Nice to have something with a range of useful subtleties rather than the usual overabundance of sledge-hammers to crack walnuts.