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POSITIVE FEEDBACK ONLINE - ISSUE 18
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The Dali Megaline
by Albert Porter

 

After living with the Sound Lab Ultimate One for more than twelve years, I expected more than a few problems selecting a new reference speaker. The Sound Lab Ultimate is a single driver, electrostatic design, providing the most articulate midrange and perfectly coherent sound from top to bottom I have ever experienced. Assuming the single driver design was at least partially responsible for this long-term love affair, I searched for a replacement speaker with as few crossover points as possible, and the Dali Megaline looked like the perfect choice.

The Megaline is a giant two way, made up of three separate speaker cabinets that lock together to form a single line source. Only two types of drivers are used, ribbons for the high frequencies and multiple woofers for the low frequencies. From the front, the ribbons appear to be mounted inside the cabinet along with the woofers. Looking from the side, you can see that each module consists of an externally mounted dipole ribbon and inside are four 6.5-inch low frequency drivers. The Dali electronic crossover provides the single dividing point at preamp level, eliminating inductors, capacitors, potentiometers and resistors in the signal path between the amplifiers and drivers.

The system is about 89dB efficient with a combined electrical impedance of 4.5 ohms (6 ohms nominal), making it an easy load for both tube and transistor amplifiers. My only complaint with the Dali and all its technological innovation is no choice of color or finish. The Megaline is available only in Alpi wood, which is a red toned, finely finished product that I believe to be an engineered material rather than veneer from a specific tree.

I ordered my pair in 2004 and was patiently waiting for the next container from Europe so mine could be pulled and forwarded to me. As luck would have it, I was notified they would arrive just four days before my flight to Sweden (the first of three European locations) to cover the high-end audio shows. It struck me odd that I should be traveling to a place in the world so near the Dali factory, just as my speakers were arriving stateside.

In spite of a nasty case of food poisoning the day of my departure, I was grateful for those few days of good health before the trip. That time was used to break down the shipping pallet and put away the boxes so my wife could get her car back in the garage. This speaker system arrives as a large, full pallet that is best handled with a forklift. In addition to the six boxes containing the modules that make up the stereo pair, there is an electronic crossover, two power supplies, eight WBT banana connectors, and various accessories, including an alignment tool to aid in sighting the speakers into position.

Fortunately, my son had not yet moved into his college dorm and with his help, we got each of the 30-inch tall modules stacked and locked together and roughed into position in our living room. Once I was on the road, providing coverage of the European audio shows, it gave me a lot of time to think about my decision. With both old and new speakers in mind, I paid close attention to each manufacturers display and what kind of sound they were achieving.

Overall, the European shows are more sedate and better thought out than their American cousins. The sound, in particular, is generally better than what I've experienced at CES. At the London Audio Show, I stopped by the Dali room, hoping to hear the Megaline. Unfortunately the room was small, so the demo was set up around the more appropriately-sized Euphonia. The systems source was an open reel tape supplied by Opus 3 Records, and between the Dali's, stood a beautiful young female cradling her saxophone. 

As the demo proceeded, we listened with just the Euphonia making music. Then this lovely woman began to play, accompanying the music on the Dali's. At this point it became obvious that she was the recording artist on the master tape and I must admit, the sound was quite compelling. I struck up a conversation with one of the people hosting the room and found I was in the company of Dali's chief designer, Lars Worre. I had my Trio phone with me and loaded into it were photographs taken just before my departure. In addition to the expected family photos, were images of my listening room and the Dali's.

Lars was heavily involved in the design of this speaker and after showing him the photos; I ask his advice on room placement and amplification. Lars' very strong recommendation was to use only two identical stereo, or four identical mono amplifiers. His advice is something I would take to heart—and then later deviate from.

Unfortunately after being away from home for nearly a month, I had not had the opportunity to borrow or beg matched reference quality amps, so I resorted to the only available matched power in my inventory, a pair of Sound Valves/Dynaco Stereo 70's. I was not expecting much in the way of performance, just looking for enough juice to get the Dali's going and see how they sound. The Sound Valves amps at 70 watts per chassis, while not all that powerful, did move the air around and provided me with a safe starting point.

Thinking about where I began with this speaker, I cannot state strongly enough that break in (particularly the Dali woofers) is the biggest challenge of owning this speaker. If you believe nothing else in this article, take my break in comment to heart. Even after six months of pushing these past the 500-hour mark, I believe the Megaline will require 800-hours or more before reaching their maximum performance.

I've developed a habit of writing down my listening impressions in a log when breaking in an unfamiliar product, and this time was no different. I kept thorough notes on dates, how long I listened, the maximum volume, and my reactions as the sound improved over this six-month period.

During the first month or so, the Megaline showed absolutely NO sign of bass, at least not anything that represented musical content below 50Hz. To make matters worse, the high frequencies were a combination of sterile, cold tonal balance combined with "projected" image brightness that made it uncomfortable to listen to for extended periods of time. I found myself blaming the speakers, fearing they were a mistake, and the next moment blaming the Dynaco's for their lack of power, particularly after having lived with VTL 750 monoblocks on the Sound Labs, an amplifier known for both dynamics and powerful bass.

Around the sixty hour mark there was a noticeable improvement in the soundstage and depth. I also heard significant improvement in the integration of the woofer/ribbon, near the crossover point, which is about 1200 Hz. Unfortunately, there was still no sign of deep bass, and the upper midrange was still imaging forward of the low frequencies, making the presentation "in your face," rather than aligned and focused. The sound reminded me of my rather poor listening experiences with the Megaline at the Denver Audio Festival (2004) and CES 2005. Fortunately, fate stepped in and gave me hope in the form of another audiophile's misery (and recovery). One of the guys in my group had purchased the new Kharma Exquisite 1D Enigma, and I watched his frustration as he passed the 200-hour, 400-hour and 600-hour break in points—and still no bass.

He was so frustrated he was discussing having GTT audio fly in to replace parts (we assumed defective), or trade them in for a replacement pair. Then suddenly, at around 850 hours the bass began to develop and the midrange integration fell into place. There is a sizable group of audiophiles who heard this remarkable improvement and everyone assumed (until now) that it was a unique situation.  When I listen to that same Kharma today, I can hardly believe it is the same speaker. It is a stunning performer, with very natural balance and resolution.

I tell this story to drive home a point. I believe many audiophiles purchase, listen to, and sell their speakers, NEVER having properly heard them. Most of us have jobs and many of us have wives and children, making it impossible to set aside a regular schedule to break in new speakers, much less keep track of the progress. (Oh, the joys of being self-employed.) Assuming a typical 40-hour work week with no obligations other than tend to the break in process, my friend's Kharma Exquisite 1D would have required 5 months to reach their full musical potential.

Realizing I was facing a similar issue, I purchased a pair of Air Tight ATM-3 mono blocks with the idea of acquiring a second pair as funds permitted. This is an amp with enough power to do the job and would fit nicely into the space I have. According to my logic, the VTL 750s were overkill; I would sell them and use the money to buy a second pair of Air Tight ATM-3's rather than another pair of 750-Watt amps just to drive the ribbons. 

When the Air Tight mono blocks arrived, I noticed the volume control on the front panel, something conspicuously absent on the Dali's electronic crossover. So I decided I would experiment, using VTL Ref 750's on the woofers and the Air Tight ATM 3's on the ribbons. The volume control (hopefully) would provide enough adjustment for differences in gain.

Nirvana! (Sort of)

The integration of the two amps was not perfect, but the volume control did allow me to trim the overall gain to a very comfortable setting. Now I was getting good sound. Not perfect, mind you, but very good, and with all that additional power the VTL 750's were providing the woofers, I could play the Purist Audio and Ayre break in CDs at extremely high volume, without fear of clipping the amps or damaging the drivers.

The break in process began to really accelerate and at about 220 hours. At this point, members of my audio group began to cast their blessings upon these new speakers. Like my friend's Kharma's, the deep bass was very late in arriving. At around 400 hours, frequencies below 40Hz finally began to creep into the room; at just over 430 hours, the coherency had integrated to the point that two of my regular visitors were proclaiming the Megalines as the best sound they had ever had. While I quietly disagreed with them, remembering perhaps more clearly the strengths of the Sound Lab, I admit the changes were startling. The Megalines had gone from being pale, anemic, and shrill, to having very good sound. They had finally begun to recreate the speed and dynamics of live music, while maintaining a graceful, musical personality.

At present, I have just over 509 hours of time on my Megalines, and of that, 86 hours at sound pressure levels near 100dB, with the Ayre (Irrational, But Efficacious!—System Enhancement Disc), and the Purist Audio (Revision B, 74-Minute System Enhancer Disc), rather than conventional music. Without these two discs, the sound of the Megalines would not be what it is today. In my opinion, these are "must-have" tools for owners of Dali, Kharma and other speakers that may be resistant to the break in process. Every time I "beat up" my system with these discs (6 hours or more at high sound pressure levels), the next listening session never failed to garner praise as to how much the speaker had improved.

As excited as I am with my progress, I still cannot overlook the very slightly unnatural electronic sound that persists in the high frequencies. This is more of an annoyance to me than anyone in my local audio group, and certainly not an issue that has been mentioned in any other reviews of the Dali Megaline.

To resolve this, I experimented with my room acoustics, including repositioning the tube traps and swapping tubes in both the input and output sections of all four of my amplifiers. When that failed to achieve the desired results, I turned to my Aesthetix Io and Callisto, rolling the input tubes, regulators and outputs with softer versions of my previously chosen NOS tubes. Puzzled that these changes did not match previous test results, I wondered if the Dali crossover might the source of this persistent sonic signature.

My next trip out of town, the crossover was shipped to a friend of mine with the right smarts and tools, and when the test came back, I discovered that the high frequencies have an additional (transistor) gain stage, increasing output voltage by 2.4dB. The high frequencies operate as a third order Butterworth design with a minus 3 dB down point of about 980Hz. The bass section is a second order Butterworth, crossing at approximately 1200Hz. The bass output voltage measures 15dB down from the high frequencies, so I assume this balances differences in efficiency between the ribbon and woofers. There is also an active EQ circuit providing boost (referenced to 400Hz), as follows:

Plus 3dB at 57Hz

Plus 6dB at 27Hz

Plus 8dB at 12Hz

There is no indication that there is a lower limit on this equalization, suggesting the bass boost may extend to sub sonic levels.

The Dali is rated in the factory literature at 35Hz to 22kHz (+ or – 3dB). However the reflex tuning is 38.5Hz, meaning this active EQ is working against the fundamental limits of the ported cabinet.

In light of this I am having a tube crossover built.

My plans are to construct it using all aluminum chassis with separate outboard tube rectified power supply. Primary tubes will be octal type 12SX7. This tube has similar performance characteristics as the popular 6SN7 (Military 5692) and VT 231, but is the 12-volt variety.

Completion date for the crossover is five to eight weeks. I will post a follow up review here at Positive Feedback Online, complete with description and images of both crossovers, including design changes and initial impressions. Stay tuned!

 

 

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