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Marten Django XL loudspeaker
However, most of the speakers in Marten's Heritage and Coltrane lines are quite pricey, and the other models trade off bass extension for lower prices. Though I believe I have the ears to appreciate speakers that cost $50,000/pair, I'm not sure I have the means to properly contextualize such costly gear for a review. Maybe, someday, I'll feel more comfortable recommending such high-ticket gear; for now, I'm not sure I can comment on the value of anything costing much more than $20,000.
But when I heard that Marten was about to release the Django XL, a full-range floorstander that uses the same midrange driver as their more expensive models but costs $15,000/pair, I knew I wanted to review them. I contacted Dan Meinwald of E.A.R. USA, Marten's North American distributor, and was able to get the very pair that had impressed John Atkinson and others at CES 2012.
Djescription
On the face of it, the Django XL is a straightforward three-way loudspeaker. On top is a ceramic tweeter, designed to Marten's specifications by German driver maker Accuton (known as Thiel and Partners outside the US), that's similar to the diamond tweeter used in Marten's top line of Coltrane models. The ceramic midrange driver, also made by Accuton, is found in Marten's Heritage line. New with the Django are its three aluminum-cone woofers, made for Marten by SEAS. These are reflex loaded, with two ports that fire down through the speaker's base. The cabinet, made of 25mm-thick MDF, is an oblique rectangular prism; the driver-bearing front baffle gently slopes up and away from the listener. All edges are nicely rounded, to reduce diffraction and to soften the Django's appearance. Although a large loudspeaker, the Django's elegant proportions make it seem far smaller.
The Django is available in Piano Black gloss (as were my review samples), or Silver Grey. As I've said before, I'm no big fan of piano-black speakers. But while I prefer the Marten Coltrane's woody surfboard looks to the Django's Darth Vader vibe, the latter's fit'n'finish was superb—if you like your speakers in black-gloss lacquer, you'll love the Django's looks. Even if you don't, they could get you to lay your prejudice aside, as I did mine.
Each driver is protected by a robust black metal cage. Accuton's ceramic drivers are notoriously fragile; the cages should keep any wayward fingers or paws off the delicate cones without adding any deleterious comb filtering to the sound. However, the cages look a bit brutal, reminding me of the chicken wire that separates the Blues Brothers from their angry audience as they sing the Rawhide theme. I got used to the cages, but perhaps Marten can come up with a more elegant solution for the Django's next edition.
The Django XL meets the floor via metal outriggers that widen its stance to increase its stability. The outriggers' four adjustable cone feet allow for easy leveling of the speaker. I'm a big fan of using spikes with speakers that sit on carpets; the Django's thick, blunt cones would likely leave it slightly floating above the floor. This wasn't a problem in my studio, where the Djangos sat directly on the concrete floor in front of my area rug, but if you have thick, shaggy carpet and like to spike your speakers, you might want to try another type of foot on the Django's outrigger.
On the rear panel is a single pair of WBT binding posts, and a knob for the Django's three-position bass-level control, which offers uncalibrated settings from "–" to "+." The Django's claimed sensitivity is 89dB and its nominal impedance is 6 ohms; the internal wiring is by Jorma Design.
Djialing in the Djangos
Setting up and positioning the Django XLs was easier than with any other speaker I've had. I first attached the outrigger and cone feet to each speaker using a supplied Allen wrench surprisingly similar to the one included with every piece of IKEA furniture I've assembled—Sweden's streets must be choked with these things. I placed the Djangos in the spots normally occupied by my Revel Performa F30s, toed in so that their drivers were aimed directly at my ears. Then I hooked them up to my Rogue M-180 monoblocks (with KT120 tubes) with Kimber Kable BiFocal X speaker cables doubled up at the speaker terminals, and had a listen. From what I heard from the Djangos straight out of the box, it was clear we were in for some good times together.
However, in ensuing weeks I experimented with placement and toe-in. Typically, I prefer speakers not to be toed in directly to the listening position but arranged so that their tweeter axes converge at a point some distance behind my head. That way, I hear greater stereo separation and better front-to-back layering.
As I adjust the speakers' angles, I listen for a few specific things. First, I want to make sure that a gentler toe-in actually does improve the stereo image: Does the image widen, deepen, and give more separation between images, or does it diffuse and confuse the soundstage? Second, does it deleteriously affect the speakers' voicing and balance? The dispersion pattern of each speaker is different at every frequency, and adjustments of toe-in angle can dramatically change the voicing of the speaker, especially at and around the crossover frequency(ies). Third, I weigh the benefits and costs: balancing the possible greater immersion in the soundstage that less toe-in can provide, while maintaining precise imaging and ensuring that there's no hole in the middle of the stereo image.
As I played with their toe-in, the Django XLs proved to be textbook examples of why I do all this. As I reduced their toe-in angle, the Djangos' stereo image did indeed seem to widen, with more separation, to provide a more immersive soundstage than when the drivers were pointed straight at my ears. However, there were tiny losses of inner detail, immediacy, and transient snap, which I had to balance with the improvements in stereo imaging. I ended up with the Djangos toed out about 10° past pointing straight at my head—I could just see the inner sidewall of each cabinet. The results were a very wide, deep, precisely defined soundstage, stable center imaging (as confirmed by playing the "Dual-Mono Pink Noise" track on JA's Editor's Choice CD, Stereophile STPH016-2), and excellent tonal balance from the midrange up. Throughout this process the tonal balance remained very constant, indicating that Django had nice, wide, even dispersion.
Finding the best spots in my room for the Django XLs was also relatively easy. As I settled on spots only an inch or so from where my Revel F30s give me the best bass, the Audio Research Reference 150 stereo amplifier arrived. This amp took the performance of the Martens to levels I hadn't thought possible.
Rereading my rave review of the Ref150 in the July 2012 issue, I'm now not sure I gushed quite hard enough for how good this game-changing amplifier is. Y'all need to own one, or at least hear one! With the ARC and the Rogues, the Djangos exhibited a wonderfully full, textured midbass and great low-bass extension, but also sounded slightly loose in the 50–60Hz range. Part of this sound can be attributed to my room, part to the Ref150, and part to the Djangos—I don't think any single element of the combination was at fault for this minor problem, but together they added up to a sound just shy of neutral that no amount of repositioning could make entirely neutral.
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Source : stereophile[dot]com
Audio Alchemy DTI•Pro 32 Jitter Filter
The DTI•Pro, released 18 months later, bore little similarity to the rather simple DTI. The Pro added a more sophisticated dual Phase-Locked Loop (PLL) input receiver for much lower jitter, and also performed a new type of Digital Signal Processing (DSP) that Audio Alchemy called "Resolution Enhancement." This processing reportedly increased the resolution of the compact disc's 16-bit digital words, approximating 18- or even 20-bit resolution. It did this by looking at the 16-bit words over a time window, and calculating the additional bits that would have been present had the signal been originally encoded with higher resolution than 16 bits.
In my November 1994 review of the DTI•Pro (footnote 1), I called it a "breakthrough in digital audio reproduction" and "a musical revelation." When inserted in the playback chain between a transport and digital processor, the DTI•Pro significantly improved the sound of my system. Moreover, experimenting with the output word length suggested that the Pro's benefits were indeed rendered by Resolution Enhancement, not just jitter reduction.
Shortly after the DTI•Pro was launched, Star Semiconductor, the manufacturer of the Pro's DSP engine, temporarily went out of business. Although Audio Alchemy scoured the globe and hoarded all remaining Star DSP chips, it was clear that the DTI•Pro's days were numbered.
Audio Alchemy took the opportunity to redesign the Pro with a 32-bit DSP chip from Texas Instruments, hence the product's new name, the DTI•Pro 32. The new chip reportedly has 50% more computing horsepower to run the Resolution Enhancement algorithm. The Pro 32 also includes some operating improvements over the Pro. Fortunately, I still have an original DTI•Pro on hand for comparison with its successor.
Description
The DTI•Pro 32 is housed in Alchemy's standard 8.5" wide and 2" high chassis. From the front panel, the DTI•Pro 32 looks identical to the DTI•Pro. The front panel's 10 LEDs indicate the input selected, power to the 32's three main sections, when the unit is locked to a source, and whether the phase or polarity has been inverted.
The lock indicator actually requires two LEDs, marked "Primary" and "Secondary." The Primary lock shows that the Pro 32's first PLL stage has locked to the source, and the Secondary LED indicates the low-jitter "double-lock" condition. The Pro 32 should double-lock to most CD transports. More on this dual PLL later.
The tiny rear panel is consumed by input and output jacks. Input is via coaxial (BNC) jack, TosLink optical, or Alchemy's I2S bus. The addition of the I2S bus input is new on the Pro 32, and is included to accept I2S output from Alchemy's forthcoming CD transport. For an additional $179 you can swap the TosLink input for an ST-Type optical jack. The Pro 32's output appears on a BNC jack, AES/EBU connector, ST-Type glass optical jack, and I2S bus. A DC input connector, which accepts a plug from the Pro 32's small external power supply, finishes the rear panel.
An I2S connector looks like an S-Video jack, but has five pins rather than S-Video's four. The five pins carry left and right audio data on one line, bit clock, word clock, master clock, and the emphasis flag. By separating the clock and transmitting it independently of the audio data, the unit receiving an I2S-formatted signal need not "lock" to the incoming datastream and "recover" a clock. The result is nearly total immunity to interface-induced jitter. Indeed, the whole idea of extracting a clock signal from the audio data is a fundamentally flawed approach to transmitting digital audio. Note that when one of Alchemy's processors with I2S input is connected to the DTI•Pro 32's I2S output, the familiar and comforting "lock" LED doesn't illuminate on the processor's front panel. Don't worry; the processor will still decode the I2S data.
Seven user-selectable operating modes optimize the Pro 32's output for your digital/analog converter. These modes set the output word length (16, 18, 20, 22, or 24 bits) and other output conditions. One mode turns off the dither, but performs Resolution Enhancement. The output word length in this no-dither mode changes with the program source, with the algorithm deciding how many additional bits it can reliably interpolate. Turning off the DTI•Pro's dither can be a benefit with some digital processors that are already dithered internally.
The seventh mode turns off the Resolution Enhancement processing for HDCD$r playback. HDCD decoding requires that the control code buried in the least significant bit of the CD's 16-bit words arrive at the HDCD filter in your digital processor. Any change in the data—such as that introduced by Resolution Enhancement—corrupts this control code and prevents HDCD decoding. This is why the Pro 32 offers the HDCD bypass mode. Note that this HDCD bypass option wasn't offered on early versions of the Pro.
Choosing the correct output word length is crucial to getting the best performance from the DTI•Pro 32. Let's say you have a digital processor with 18-bit DACs, and you set the Pro 32's output word length to 20 or more bits. The DACs will simply truncate (cut off) any bits below 18, introducing noise and distortion. As JA described in his review of the Meridian 518 Mastering Processor in the January '96 Stereophile, truncation also hardens midrange textures and reduces the sense of space.
Conversely, setting the Pro 32's output word length to 18 bits if you have a true 20-bit processor prevents you from experiencing the full benefits of Resolution Enhancement.
Just because your digital processor has 20-bit DACs doesn't mean that it will pass 20-bit data from input to output. The NPC 5813 and 5813 digital filters, for example, truncate the incoming data to 18 bits. The older Yamaha YM3623 input receiver chip will pass only 16-bit data. For comparison, the Crystal Semiconductor CS8412 and UltraAnalog AES21 input receivers will pass up to 24-bit data, as will the Pacific Microsonics PMD100 HDCD decoder/filter.
There's yet another trap to be aware of. Digital processors with the Crystal or UltraAnalog input receivers, the PMD100 filter, and 20-bit DACs still may not pass 20-bit data. Some processors that have been retrofitted with the PMD100 weren't redesigned to pass the PMD100's full resolution to the DACs. Two such examples are the PS Audio UltraLink Two and Enlightened Audio Designs DSP7000 Series III. Each of these processors has only a 16-bit data path from the digital filter to the DACs. Consequently, they'll truncate 20-bit input data, even though they have a 24-bit input receiver, 24-bit digital filter, and 20-bit DACs. Any processor designed from the ground up around the PMD100 (as opposed to an existing design retrofitted with the PMD100) should pass at least 20-bit data. The only way of finding out which "20-bit" processors truly pass 20-bit data is by the measurements included in reviews. Reports from readers suggest that some processor manufacturers either aren't aware of their products' capabilities, or provide misleading information.
Footnote 1: See my review of the DTI in Vol.16 No.5, DTI measurements in Vol.16 No.11, and DTI•Pro review in Vol.17 No.11.
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Source : stereophile[dot]com
