Visaton B200 OB almost done!

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harryz

Visaton B200 OB almost done!
« on: 1 May 2012, 03:30 am »
Greetings OB lovers-
I've been building up a 3-way OB over the past few weeks and one is done, with the 2nd in progress.  In the past I've tried Jensen 12" field coils, Altec biflex on JE labs style etc..  This is much more to my liking, as follows:

B200 run wide open so far (160 hours of burn in before mounting them)
Aurum Cantus G2Si with .22uF cap
Eminence Alpha 15A on the bottom

All drivers flush mounted in 21" x 43" one inch Russian birch baffles, with tops curved a la Lowther tiny OB.  Side pieces and bottoms in process; sides are only half height. 15A outer edge about 1.5" from the bottom and tweeter 1/4" above the B200, which is centered 32" above the ground.  All tilted back 7 degrees per Martin King suggestion.  I'm running one with tripod stand now and I'd rather have one of these than most everything I've had, including several pairs of Quad ESLs, Altec horns, Acoustat 2+2s, IMF TLS 80 Mk2s, Spica TC 50s and more.  The OB is more dynamic, magic factor at least equivalent to ESL "57s" yet with more resolution.  Segovia is in the room with me as I write this.  And what a great soul he is.

Anyway, the 2nd speaker will join the fray later this week...

Now for the questions, namely:  any ideas of how these might work with Hypex nCore 400s on the mids and tweets and UCD 180 on the woofers?  Also, has anyone had luck multi-amping their OBs with active crossovers?  Anyone using DEQX or modded Behringers on their OBs?  I have parts to cross passively but want to maintain high-ish efficiency.  Am using custom, heavy duty KT 66 monoblocks and a tube preamp on the single unit now, but would prefer to have a simple system with cap on the tweeter (maybe cap and coil), a coil across the B200 to serve as high pass filter and a plate amp below to run the 15As.  Am looking for ideas and suggestions, so bring it on.  Am also very interested in comparisons of high quality Class A/D and good SET and PP amps on the B200 OBs.

With thanks in advance (not to mention thanks well after the fact for the marvelous Gravity Well thread, which got me started on this path.  Better late than never!)

Harry

harryz

Re: Visaton B200 OB almost done!
« Reply #1 on: 1 May 2012, 03:31 am »
Whoops!  I forgot to mention that 15A is driven by small plate amp.  Currently set on 100hz crossover at decent volume and 180 degree phase.

Harry

-Richard-

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Re: Visaton B200 OB almost done!
« Reply #2 on: 4 May 2012, 06:51 pm »
Hi Harry ~

Unfortunately I cannot help you with your specific questions regarding the drivers you are interested in. But I did want to thank you for favorably comparing your present B200 OB's with speakers that are usually on the top of everyone's list of the "best" among those commercially available, like the Quads and Altec horns.

Yes... Dan Mason gave us the gift of his experience and creative energy when he started the Dark Star thread... I will be forever grateful to him for opening the door and exhorting us to enter into the experience of building our own DIY Open Baffle speakers. For me it was the ending of the illusion that audio magic could only be found in commercial speakers... and that magic must be purchased with large amounts of money. With the simple OB application of using a driver like the B200, or the Dayton PS220, we can have incredible sound for a fraction of what commercial speakers cost.

What is necessary is for someone to take a little leap of faith and dive into the project for the fun of it. You will never go back to commercial speakers again.

With Open Baffle the music lives!!!!!!!!

Warmest Regards ~ Richard

harryz

Re: Visaton B200 OB almost done!
« Reply #3 on: 5 May 2012, 01:32 am »
Hi Richard-
Thanks for your kind reply.  I've enjoyed reading your posts on the Gravity Well thread and elsewhere, and especially appreciate your sensibilities.

Construction and assembly of both speakers is finished.  I'm going to use natural Minwax oil in a couple of weeks.  For now, they're passively crossed with 2uF paper in oil cap on top, .225mH inductor on the woofer, 68uF cap across the woofer and 9mH choke on the woofer.  I believe that this means 1st order on the tweet and B200 and 2nd order on the woofer, but I'm not sure.  The B200 runs open all the way down but rolls off at 4500hz.  Sound is wonderful so far, but lots of experimentation to do.  I may just use one amp, as I'm getting nice bass and would prefer a simple system (currently using custom KT 66 tube monoblocks).  Here are pics.

Harry





Gothover

Re: Visaton B200 OB almost done!
« Reply #4 on: 5 May 2012, 03:54 am »
Very cool project, keep up the good work.

Dave

-Richard-

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Re: Visaton B200 OB almost done!
« Reply #5 on: 5 May 2012, 06:22 am »
Hi Harry ~

Thank you for your kind words. Your speakers look superb... well thought out and executed. I like the fact that you have shared with us the important information about cross-overs... that will help anyone, including me, who is interested in trying something similar to have "values" to work off. In the DIY world every piece of information is important.

Thanks for sharing your wonderful design with us.

Please keep us informed as you learn anything that you feel contributes to your understanding, or if some modification helps to raise the performance to a new level.

You asked about SET's... I am looking deeply into that as well. I am trying to take a fresh look at everything... to get closer to a solution that will bring the quality of sound I think I am after.

Right now I am looking into 300B SET's and getting an overview of what is out there. The 2A3 SET which probably sounds a little less euphonic and perhaps a little more linear and detailed, is not realistic with its 3 to 3.5 watts, for the kind of listening I seem to be doing lately. A SET designer I respect a great deal said this to me a few days ago in response to my asking him about the idea of doubling the output tubes for each channel to generate higher watts: "If you double the 45 tube you get a 2A3 tube... if you double the 2A3 tube you get a 300B." Interesting isn't it? Another designer I trust a great deal suggested that: "it doesn't matter which Triode tube you use, 45, 2A3, or 300B... they all sound the same if the circuit is optimized for them... the problem is that few designers know how to really use these tubes effectively... so they sound different because the circuits are not optimized to allow them to sound at their best". So that suggests that there is a great deal of myth, misinformation and hype drifting through the world of SET's. I am attempting to clear the air to bring some clarity so I can find the amplifier that will suit my purpose.

For example... Audionote England has a kit that is bloody expensive and that uses extra transformers as a coupling device... h-e-a-v-y... but people rave about it in their feedback section... Bottlehead has a kit that is much more reasonable although their output transformers are surprising small. A great deal of the SET literature claims that the "sound" that SET's are famous for is in the transformers... that is unless one is interested in a transformer-less circuit design like David Berning's... not cheap... and unless he makes a production-run... which is not now on the agenda... his hand-made examples are rather rudimentary... I have heard good things about Don Garber's latest mono-block versions with Japanese transformers... over $6k.

I am looking for a "transparent" and rich sound... liquid but and not overly "tubby". If anyone has any suggestions for a 300B amplifier that fits that description I am extremely interested in your experience and thoughts.

If it is expensive, perhaps I can purchase it used.
 
If I discover something interesting I will write about it.

Erling/Scorpio has kindly helped me to "tame" the Dayton PS220 Neo driver I am now using by applying a simple passive Baffle Step Correction "filter"... I will be writing about this simple solution very soon. I am traveling for 3 weeks in England beginning this Sunday. When I return I want to share my insights about what I think I am hearing... and other thoughts about audio as well. Erling is a GEM... incredibly helpful, astute, thorough and generous in his observations and insights. The Open Baffle forum is fantastic... may it live forever!!!!!!!

With Warmest Regards ~ Richard

harryz

Re: Visaton B200 OB almost done!
« Reply #6 on: 5 May 2012, 07:15 am »
Thanks for the compliments.  For a first go around with the B200, I'm quite happy with the sound but I'm going to be making some changes.  First, the Eminence 15A is problematic in an OB, despite it's popularity and common use.  It isn't a bad driver but it has serious limitation.  It's stated efficiency is 96d or so with a high Qts, but the efficiency is an average.  At 50hz it's actually 85db, and it really takes a nose dive below 100hz so it needs either 1) equalization or 2) a second driver, preferably on the side, which I can't do unless I rebuild the baffles.  Not a big deal if I go that route.  In addition, it only has a 1.5 inch voice coil and has a low xMax, which means that output is limited.  By contrast, the Hawthorne Augie addresses all of these issues but is $100 more per driver. 

I also didn't put a low pass filter on the B200, which would have cleaned up the midrange, and I should have used a higher order crossover on the tweeter.  The baffle has a 7 degree slope, which is a common practice but a serious NO NO.  The slope is intended to time align drivers, but this shoots the sound at angles that aren't natural (ie... at 9 ft away much of the midrange is over a seated listener's head).  Thus, lobing effects are prevalent.  Moreover, I should have rear loaded the midrange and chamfered the hole.  Rear loading the mid would have solved the time alignment issue better than what I did.  Live and learn...

I've had many SET and PP tube amps-- modern, vintage and custom. What I've learned so far is that execution is everything, power supplies are critical, and-- for me-- simple two stage amps tend to sound best all things being equal.  I don't like regulated power supplies, and I love triodes.  That being said, it's tough to beat a nice 6BQ5 amp with great vintage iron.  And while I love 2A3, 45 and 300B (and have owned nice samples of 2a3 and 300B) I am certain that they don't have enough juice for full range use for orchestral music unless speakers are more like 100db.  With dynamic swings of as much as 60db, classical music really requires much more power than triodes can supply unless speakers are bi-amped.  This being said, I'd love a nice triode amp on the mids and highs of my OB!

Stay tuned and all the best-

Harry

Poultrygeist

Re: Visaton B200 OB almost done!
« Reply #7 on: 8 May 2012, 12:55 pm »
The Alphas need power. I use 150 watt solid state mono blocks on the Alphas while I drive the main full rangers ( Tang Band W8-1808 ) with a 2a3.

THWO

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Re: Visaton B200 OB almost done!
« Reply #8 on: 8 May 2012, 12:58 pm »
I discovered a serious increase in precision and control after glueing thick bitumen stripes onto the inner sides of the thin metalsheet frames of the Alphas (I used two per side in a baffle of comparable design).

Rgerads
Till