Thursday, May 30, 2013

Bozak Rebuild Project - Part 8

Sometimes, you just have to have faith.  I did believing that one day I would discover a high sensitivity leaf or ribbon tweeter that would match the acoustic efficiency of the Bozak drivers. This is a tall order but as Tony Robbins says, "You are what you believe." So I again put his legendary ideas together with my pursuit of the high end and viola - a 97dB/W/m ribbon tweeter enters my life.

I searched long and hard trying to find a dynamic driver that could keep pace with the Bozaks and found something sort of close - but not really. The Audax gold dome (TW025A28) came close measuring 94dB/W/m (not at the 1/2 meter point Audax publishes their data) and I was pacified with filling in the top octave where the Bozak B-200Y tweeters fell short. Below is an RTA measurement of the way this super tweeter in the system performed.

Audax TW025A28 Dome Super Tweeter

With persistence and perseverance, I changed my search focus from dynamic home audio drivers to professional compression drivers and found a few that were tempting. JBL, Fostex, and Fountek all had bullet-styled tweeters popular in car audio systems but my ears are more sensitive to the ringing and other inherent compromises in such driver designs and although VERY tempting, I decided to "keep the faith."

One day, I ran across what was called the Versarray made by the well established professional sound reinforcement company, Peavey. With its touted 97dB/W/m sensitivity, this seemed to be a perfect match for my dreams. Now, to find some.

Searching eBay, there were some Versarray  systems still sold despite the model now being discontinued. Apparently professionals either love them or hate them, mainly because of their limitations in stacking and angling vertical arrays, but those who played small club venues seemed to boast about them. With this in mind, I found one and gave eBay a bid that couldn't be refused. One Peavey RD 1.6 came to my door a few weeks ago and I was thrilled. It looked like it was going to work and with a quick attachment to the system (disconnecting the Audax and temporarily connecting the Peavey), I was not disappointed. But wait, I only have one! As Tony says, "keep your eyes on the prize."

So undeterred, I settled into that personal conviction where I just knew another driver would soon appear, and with the very next emailing of the Parts Express clearance catalog, my dreams and blind faith paid off.  Somehow, Parts Express bought Peavey's old stock and were now selling them for a pittance. If they still have them, here is the link.

Within a week, another of these little beauties arrived at my doorstep and I hurriedly unwrapped it and attached it temporarily to the system as the other.  Now with a pair of these drivers sitting on the tops of the woofer cabinets, I was able to judge the potential of their sound and it proved better than I could have anticipated. The sound stage opened up literally as if a doctor had removed ear wax from my ears and instrument inner detailing was remarkable. That was enough to convince me I needed to stuff them into the existing box - somehow.

Coincidentally (if you believe that there are such things as coincidences), this driver is exactly the same size as two Bozak B-200y drivers. So I pulled out the center two drivers from my satellite, stuffed in the RD 1.6, and flipped on the switch. I was shocked. After changing my underwear, I settled down and started to make some measurements trying to see if what my ears heard my RTA measurements could confirm  - and they did.

Peavey RD 1.6 Ribbon Super Tweeter

Now understand that there is a small error in the crossover network for the Peavey that I have yet to correct, but have already designed. Adding a few turns to the second-order Bessel inductor will bring things back into alignment and I will do this some time next week. But for now, I am thrilled with their performance and I cannot find the proper expletive to give this driver and this system.

Like any good leaf or ribbon driver, this one is no exception. Its massive magnet structure and low mass diaphragm sound so crisp and clean compared to the slower dynamic driver I had been listening to.  The Audax, while a very good dome tweeter, just does not have the transient abilities that a low-mass tweeter does. Now I can hear the taps of cymbals and tamps of tambourines clearly rather than in the distant background as before. Now I can hear sheet music turning in quiet classical passages and all of those other sparkling top-octave characteristics well-designed high-end speakers posses.

These speakers have come a long way from the first time I built the satellite and now can hold their ground with some of the best I have ever heard. Here is a picture of the system now to show you what the new satellites look like.

Satellites with RD 1.6 Drivers

I am shaking at the time of this writing since adrenaline is still coursing through my veins from the excitement. What I can say without reservation is that if you are considering performing any of the modifications to your Bozaks or adding a super tweeter to your system, you have to give this driver a chance. Parts Express has a really nice no questions asked return policy IF you do not solder the driver terminals (I used test leads with alligator clips for my initial evaluation) or blow out the driver (duh!). The price at $100 each is very fair and shipping for the pair is free.

So my friends, stay tuned for what appears to be the final round of tweaks to this amazing speaker system, the one where I finalize the crossover network design. Hopefully, the math and the reality match up and yes, I have faith that it will. See what happened next in Part 9.

See also Part 1Part 2, Part 3, Part 4, Part 5, Part 6, and Part 7

Yours for higher fidelity,

Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

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