Friday, December 30, 2011

System Two Update

Yet another system two update. This time its another speaker again. Well, I do not know what made me to built these speakers, perhaps I wanted to imitate the look of Legacy Whisper, just kidding. It only remotely resembles Whisper. Anyway, it started long time ago when I got 2" Dayton domes brand new never used very cheaply on ebay, so I started looking for an application. I have seen HiVi ribbons on sale, so it was only a matter of finishing the lower mids section. I selected Dayton 4" midwoofers RS125. Crossovers were optimized using Holm Impulse program based on real measurements. Panels are open baffle, what else, working from 150Hz up. Woofers is still the same, 15" Jamo in closed box.
The system is biamplified using active crossover, has 31 band digital eq and tube amp for mids/heights and solid state for woofers. Signal sources are the same as before, Cambridge Audio CP player (dual Wolfson), SAE FM tuner, Technics SP25 with ATOC9 cart, some Onkyo Integra deck and preamp (used only for signal switching and RIAA), and digital tape player. System could use better amp, I am working on it.

Thursday, December 29, 2011

CBT array update

I added tweeters to the CBT line arrays. Even those NS3 Aura's are "fullrange", their response drops after 10kHz. They need significant eq in order to sound good. Tweeters are needed. Eighteen tweeters were wired in three sections of six to give 16 ohms, to match the Aura's. Arrays sound much better now, almost no need for eq. Last picture might be confusing a little, just to clarify, there are two systems. Line arrays are powered by two older silver JVC SuperA AX1 and AX2 amps, it's bi amplified with active crossover at 170Hz and 2x15" black subwoofer in the back. Other system is something else, Betsy WOW MTM with Selenium horn tweeters, excellent sounding open baffle, with two 15" woofers handling the bass. Second system is powered by JVC receiver, SuperA as well. By the way, these JVC components are under appreciated gems, they sound gorgeous. JVC did great job with their SuperA circuit. Their CD players are excellent also, once their output stage (3 dual OPA's) is bypassed by simple tube buffer. I lampized some and they are excellent sounding CD players. But that is another story.

6N11 Linestage

I just finished new line stage, it's SRPP with 6N11. I bought this kit on ebay for $35 plus shipping. The line preamp has four inputs with nice japanese relays for switching and one output. Two transformers are used, one for preamp and one for signal switching. The line stage is absolutely quiet, no hiss, no hum. It sounds excellent.

Wednesday, December 28, 2011

CBT Line array

Don Keele's constant beamwidth transducer...or something like that.
I got plenty of small tweeters, Onkyo tweeters sale, box of 200 tweeters for $20. I got 100 small 3" fullrange drivers Aura NS3 for $1.50 what is one to do? Line array! Well, I built line arrays before and they can do amazing things, but this time I was about to built something totally different. Here are some pictures from the built, its still work in progress.
It was a bit of a challenge, since the only tools I have are drill and jigsaw. Plus I used smaller pieces of plywood, so I had to glue larger pieces together. Inspite of the challenge, I enjoyed the build. Currently the arrays have only 3" fullrange drivers. Tweeters come later. I could not wait. All the fullrange are wired equally, no shading. I have my reasons for it. 16 small 3" fullrange units, each 16 ohm is wired in 4 sections of four giving nice 16 ohm output impedance. Easy to drive with any amp.

Tuesday, July 26, 2011

Aikido 5687 linestage

Aikido pre-amp

Just finished and tested this preamp with 5687 tubes. One input only, two outputs for bi-amplification convenience. I used two transformers, whatever I had at hand. One for high voltage, 250 volts with RCRC filtration. One for DC regulated power supply for filaments. Sounds great, however, in direct comparison with octal Aikido with 6SN7 tubes, I prefer octal. This one goes to ebay. Here are some pics.

Monday, May 2, 2011

System two - update

Betsy WOW on open baffle

It's been a while I posted any changes to my system. It's because I am working on two other speaker projects, Keele's CBT line array, which is a lot of work, and on Legacy's Whisper look alike. However, one significant change happened in my second system. I replaced vintage Magnavox elliptical midranges/paper cone tweeters with brand new open baffle mids/tweets. I placed two Betsy WOW (Betsy Without Whizzer) and a Selenium horn tweeter in d'Appolito arrangement. The result is seriously good sound, to the point of approaching my main system. I wonder if the same electronics as in main system would be day I will swap the speakers to see. It's not that easy because both systems are biamped. Anyway, here are some pics of the second system after update.

Detail of the left speaker. And from the back.

I highly recommend Betsy WOW speakers for open baffle. They go deep, almost 50Hz, they are reasonably flat in midrange area, they do not have nasty breakup modes typical of real world fullrange drivers, and they are quite efficient. Not in the Lowthers area, but pretty high. Having two per side definitely helps even more. Power handling is good as well, better than Lowthers. Having dedicated tweeter makes top end way better sounding than from fullrange drivers. No matter how puristic the fullrange approach is, the result of well executed dedicated midrange/dedicated tweeter is just better sounding system. Originally I had two Betsy's per side connected equally, as you would normally in d'Appolito 2-way system. However, I prefer the upper midrange to come from one point source, rather than two, so I changed the crossover to 2.5 way, with one Betsy rolling off sooner that other. To me this sounds better. So the top now is 2.5 way, plus the woofer makes this system effectively 3.5 way. I am enjoying these speakers a lot. Highly recommended, but I already said that, didn't I.
Here is how Betsy WOW measures (no tweeter) using Holm Impulse:

It's unbelievably flat from 50Hz to 500Hz, then it has small dip, nothing too bad, then slowly rising fr response with breakup modes not too bad either. With single coil for crossover at about 3KHz, those brakup modes are removed and fr response can smoothly transition to tweeter.

However, to be honest, I have recently had some troubles with Besty I want others using these speakers to know about, here is the whole story from the letter to Paul, the owner of Wild Buro Labs:

Hi Paul,
this is not easy wright, but I have to do it. I was very fond of Betsy WOW for quite a while, but I encountered a problem with my drivers. I bought 4 Betsy WOW from you while back and mounted them on open baffles in MTM configuration with subwoofer. I really liked the sound, efficiency, clarity. However, I encountered the problem, which I am curious to know if you potentially know about it. The problem is that I never blamed the Betsy drivers for it, only this weekend I discovered what the problem was.
Anyway, long story short, here is the problem: with certain recordings, particularly simple ones, with only one intrument in midrange playing, and especially on female vocals, particularly opera high pithced voices I heard buzzing sound. For last half a year I was trying to find a source of this buzz. I never blamed drivers, since inspection always showed free movement, no rubbing of voice coil, the drivers looked good. I removed dust caps and found nothing wrong with voice coils, nothing stuck or loose there. I blamed Behringer ultracurve, thinking its overloading some band, or some pre-amp stage overdriving or similar things. I kept changing preamps and amps, but the problem never went away. I must say with most recordings, especially complex ones, all sounded good. However, the problem got a little worse over last few months, so I investigated deeper. This weekend I used testing cd and with certain mid frequencies on sine wave I heard that buzzing sound. I inspected all stages of electronics with osciloscope, at every stage the sine wave looked great, no sign of overload anywhere. Behringer ultracurve was clearly not to blame. Signal leading to the drivers was clean as a whistle. So electronically all looked great, but with 1 kHz tone I heard buzzing, slightly different level from each speaker, weird. This lead me to discover that at the point on the cone, back side of the cone where lead of multristrand wire is entering small metalic ring, which on the other front side of the cone connects to the voice coil wire, is the source of the buzz! Yes, buzzing sound is comming from that metalic ring or rings on back side of the cone, where those two wires meet. If I touch it gently while the sine wave is playing, it prevents the buzzing! There is something loose inside those rings. It only buzz at certain frequencies. So now I need to find a way to fix the problem.

Thats pretty much the story. I believe there is some lousy connection made which over time loosens and makes buzzing irritating sound.

Paul, have you encounter anything like this with Betsy drivers?

Since then I fixed the whole problem by aplication of few wood glue drops on each brass ring.