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[Dmason]

For an interesting treatise on the subject of DarkStars, read "A Brief History of Time" by Dr Stephen Hawking....

In the interest of sharing an astounding synergy in sound, I have encouraged -Richard- mxgsr and Gmood1 to get going on their own open baffle experiments combining their ClariT amps with the power source of Hawking's DarkStar, the Visaton B200 widerange driver. All have their pairs on the way!! It will be interesting to see what happens, and what observations, and suggestions they can lend.

With the ClariT sound, the B200 is pretty much my all-time favorite, most musical, dynamic, open, organic sounding, easy-on-the-ears speaker driver I have come across. There are many who advise against it, based solely on technical impressions, yet the people who have actually made the effort to obtain them and use them have quite a different opinion. An opposite one, in fact.. This is an extraordinary pairing of amplifier and driver. Soon we will have open discussion, so I thought I would open this thread now, and let the games begin.

[JeffB]

Where can the Visaton's be purchased?  What is the price per driver?

[mcgsxr]

I sent a payment for a pair of Visatons this afternoon, and hope to have them in an open baffle inside 2 weeks.  Hopefully in time for powerbench's visit, as he intends to trundle down to my end of the province, later on, and is bringing me that fine treat - the Clari-T!

If you live in Canada, the Visatons are easily available from Solen in Quebec for CAN$ 167 each.

Solen will ship to y'all down there, and in greenbacks, the converted driver cost is $135 or so.  Give them a shout to discuss shipping - their English is great, even if they do live in the predominantly French part of Canada.

These are the speakers that I intend to use in my basement 2 channel retreat, in the new house.  I was expecting to wait until closer to moving to buy them, but a lightly used set became available, so I jumped!

Looking forward to expressing my thoughts, with the modded Teac, and hopefully also the Clari-T at some point.

I figure, this is my kind of DIY project - cut hole, drill in driver, lean against speaker stand - now listen!

[mcgsxr]

oh, sorry...

http://www.solen.ca/

[tobyw]

Hi, DMason and mcgsxr!
What size open baffle are you using with the B200?
What material are you using?
I have the PHY-HP KM30 SAG dual concentric drivers in a 3/4 inch lexan open baffle that sounds (and looks) amazing, especially with the Clari-T.  Vinnie is making a custom DACT battery powered active preamp with phono stage to mate with the batttery powered Teres 255 turntable, so the sound should be dialed in, and we can have tunes here in south Florida even when the next Hurricane blows through and we lose our electricity!
Regards,
tobyw

[ooheadsoo]

The driver's manufacturer provided frequency response looks like it needs to have the top end brought down - even before baffle step compensation.  Are you guys finding it excessively bright?  It seems that even if you use a big baffle, the response is still going to rise towards the top naturally.

[JLM]

Yes, the B200 appears bright, that's part of what DMason is elluding to.  But remember that with an 8 inch driver and no whizzer, they will beam.  So its a simple matter of pointing the drivers off center (many suggest aiming them at the listener's knees is a good starting point for experimentation) if they seem "top heavy".  This works for my whizzerless 8 inch full range drivers to improve imaging.

Recall too that in open baffles half the response is directed behind the driver.  Again with higher frequencies being so directional much of the rear firing output will get lost/absorbed (room treatments could play a major role here).

With Fs of 40 Hz there will be a bit of weakness on the low end, but these drivers have remarkably good bass response at their efficiency.  Practical baffle sizing will limit bass output.  Let us know how the bass measures in your rooms.

Now, what would I do with a 4th set of speakers?

[nickspicks]

You wanna good Darkstar experience,
check out the album "Live Dead" by the Grateful Dead.
Dark Star > Saint Stephen > the eleven > lovelight
can't beat it.




no , wait...
(~);}  thats more like it.

[mcgsxr]

As usual, JLM is on the right track - the dispersion characteristics of the driver, when leveraged in concert with their tendancy towards a rising response, is one trick to even out the response at the chair.

Here is a link to Visaton's website (the English version), where you can review the 5-6 "enclosures" that they recommend - some of them include simple Xovers for those interested - http://www.visaton.de/english/artikel/art_771_1_3.html

I will start off in a 4ft x 4ft baffle, and trim down from there.  I will post my thoughts, but my measurement equipment is only my ears...

I should have some drivers, and some russian birch ply, mated in around 2 weeks - can I hold my breath that long?

[JLM]

Mark,

I'd suggest starting out with the cheapest possible plywood and modify one baffle at a time so you can A/B as you go.  


IMPORTANT (not meaning to shout, just to highlight):  One of the problems with O.B. is reflection of sound from the other channel off the baffle.  A/Bing in mono eliminates this effect.  Padding the final baffle design should save money on a fancy baffle material while addressing this issue to improve imaging.


Typical OB designs provide an offset so edge roll off occurs at different frequencies.  Of course make sure you break in the drivers first (how long Dan?).

When you've settled on a baffle size/offset design go ahead and use the material of choice.  Remember that as the baffle has little pressure on it (compared to box designs) you can use nearly whatever material.  With the reflection issue mentioned above I could trying high density fiberglass with an air space behind mounted on the baffle (the driver would have to be offset forward, perhaps on a 12 inch square of wood thats thickness matches the fiberglass/air gap thickness).

[mcgsxr]

Interesting suggestion JLM, thanks for sharing.

I had not thought about how sound might reflect off a 4 foot square panel in the room... duh!    In my case, I will be putting the equipment rack in a corner, and then the panels out near the side walls, as they spread away from the rack (corner) so I thought I had some of the wall reflections issues licked.

I think you mean that the face of the OB can be lined with damping material, to prevent/minimize reflections, and the driver itself is pushed forward the thickness of the damping material, such that the whole thing is a uniform "depth" of surface - equal with the driver?

I may start with cardboard for the baffle, or MDF, but the final version for me will be baltic birch ply - if I were trying (and dear God what a WAF battle that would be...) to get these into the living space of our home, rather than the unfinished basement cave, I would likely go to the trouble and expense of locating some plexiglass or glass etc, to reduce the optical impact of such large panels...  but as I am free to do as I will down there in the new house, it will be plain and simple plywood for me!

Thanks for the tips, I expect to use an offset of some kind, and am more than willing to share all that I discover, once I have them together, and am able to listen to them!

[Dmason]

Wow. Off and running. Good discussion. Nice to come home to...

- Rule of thumb, 10 per cent offset of baffle. Ill give all of you a head start. Whatever size chunk you start with, cut TWO baffles for each driver, and the "control" baffle, mount 29/29cm from upper inside corner, matched pairs. This is filter-down DarkStar technology to get you going, and is the product of testing between myself and another gravity well voyager in Germany.

JLM talks about reflections. Dead right. What I did was get some of that thin CORK lining stuff, and veneer the backside of each panel. Immediate and obvious effect equal to big dollar acoustic treatment. Maybe I should do the same to the fronts.

Do not underestimate the fact that the backwave of the driver is put into play here. This is what the naysayers are not taking into consideration, and in truth, they should all just be quiet. It is like suggesting that Germans dont know what they are doing when it comes to design engineering and applied science.        What you do not get is port loaded chuffing, backwave cone resonances, box resonances, and a whole lot of stuff whose detrimental effects become apparent, once you remove them.

Someone mentioned "...before baffle step correction.."  ....this is not about applying circuit suicide to the works.

Less = More.

 Please do not confuse the issue here. The WHOLE IDEA here is direct coupled, active powered, Tripath/ClariT + Visaton B200. There is absolutely ZERO point to this exercise if you get into all that stuff, the sad result of which being the light of the music will be completely obscured by an impassable ceramic cloud, -an electrolytic storm with Copper funnel clouds, that will suck the life of the music right out of the mix, leaving you in some confused sonic "Oz" with no ability to hear the blue skies above, and worse yet, no way home. Zobels are allowed.   ...If you need crossovers and musically opaque boredom, go to the Dynaudio website for products with metallo-ceramic prostheses done right, and then budget for a very powerful, AC powered amplifier.......NOTE any contouring should nowadays be done completely in the digital domain, where the signal can remain uncontaminated. Behringer now makes this very accessible, with the DEQ2496. Check them out, a sonic Swiss Army Knife, and indispensible tool, once you figure it out.

[JeffB]

I was looking at the NoBox BB design for the Visaton described here:
http://www.visaton.de/english/artikel/art_829_6_20.html

It states 90db sensitivity.
But this design has the Visaton B200 and a 15" woofer.  It doesn't state anything about a cross-over.

Is the sensitivity low due to the open baffle, or is it perhaps due to a cross-over?

If I were to use the Visaton B200 in an open-baffle, my room layout would require a tall-thin baffle.  I could go maybe 5ft tall by 12" wide.  Any thoughts on whether this would work?  How should I offset the driver from the upper inside corner?

[Dmason]

NoBox has a very large and complex crossover. It could be pared down, and some of the XO configurations reflect the German tendency toward complexity, in their designs. Many, have gotten better results with less parts. Bear in mind also that Visaton sells the whole thing as a kit, complete with XO components, a high margin item.

 Again, DarkStar's essence is about -active direct-coupling of the Visaton B200-- to the ClariT. Mechanical crossovers are "illegal". Zobels are "legal." Active, digital crossovers are encouraged, as is RTA and channel EQ, all digital.

[mcgsxr]

Well, I am not the right guy to do the math for you... but let me arm you with the capacity to do some of the modeling yourself!

I would use this doc as a guide for getting you in the right neighborhood, and then experiment with ears and saw to get it right for you, in your room.

Here is a broadly known xls file, that helps model the frequency response of a given driver, in an OB of a given size.

I reiterate, that this will just give you SOME idea of what this might sound like, since your room is going to interact differently with the combo, than does the predicted response - know what I mean?

Good luck, and please share your results!

http://www.t-linespeakers.org/downloads.html

[Dmason]

Mark

That is exactly right. The worksheet's author, Thorsten Loesch, is quick to point out that the idea is more of a sketchpad to "get and idea" of what to expect. When you manipulate the FR thru digital EQ, you can accomplish alot. you can easily flatten the rising FR and you can push the LF reach beyond the natural baffle roll off for example, and the B200 has TONS of Xmax. It can jam.

For a table plotting FR rolloff  FR/baffle width go to www.melhuish.org

I find the best test equipment available is the Mach II Tympano-cochleometer.

I should add that, once Thorsten dialed in his open baffles, -no turning back for him.

[thayerg]

Intersting discussion. Some have suggested using corrugated cardboard to test different baffle designs. Other products I've thought about include coroplast (corrugated plastic) available from packing supply places, not too expensive, and polycarbonate (available under plastics in the yellow pages) more expensive but stronger.

It also seems like using digital eq could pay off big time here.

[-Richard-]

As Dan mentioned I have a ticket to ride the B200 rocket
off this planet to the next constellation called Sonic Bliss...
just follow that Dark Star to Nirvana...

My technical background is still somewhere in the
Pleistocene era however...so any help from the other
astronauts of the Dark Star Confederation would be
deeply...deeply...appreciated...

Cork on both sides of the baffle seems interesting Dan...
and would make the ultimate material considerations
less important...especially if it significantly effects the
smoothing out of the sound...something that would really
impact in my current space...

The entire area of digital EQ on the cheap is a mystery
to me...perhaps that can be included here as part of the
ongoing inquiry...to help AC member such as myself
still trapped in the Axial Age...

The B200 space ship is due to arrive in 2 weeks...
I am already making provisions for its arrival in
my launching pad...

Warm regards -Richard-

[JLM]

Mark,

You're right on regarding the driver offset.  I forsee a 1 inch baffle plus 1 inch spacing and another 1 inch of high density fiberglass with a 2 inch offset mounted to the front of the baffle board so that the driver is flush with the front of the fiberglass/space.  As only reflected sound makes it to the back of the baffle and must be reflected again to be heard it's treatment is less important.  Perhaps another 1 inch high density fiberglass mounted directly to the baffle (would help dampen the baffle too).  Add a 4 inch diameter half round to the entire perimeter.  In terms of WAF, the fiberglass should be covered anyway (to contain the fibers) so let her help to pick.  (Might even try covering the driver if it helps WAF.)

thayerg,

The baffle must have some stiffness to avoid doppler effects as it flexes back and forth, so I'm not sure about cardboard or plastic.

JeffB,

A 12 inch wide baffle is barely a baffle, more like a board.  If you have two adjoining corners, but little space you could try mounting the boards into the corners leaving openings at top and bottom.  This would provide corner loading to add bass and extend the size of the baffle to huge proportions and creating a nearly Infinite Baffle (used for subwoofer designs).  Check for clearances for the driver first.  A bit of padding behind the driver may be needed to cut down on the reflections.

[-Richard-]

Hi JLM,

"...corner loading to add bass and extend the size of the baffle
to huge proportions...creating a nearly Infinite Baffle..."

Nice thinking...a very interesting application of the baffle
board...no matter what width it is...one could make the width
wide enough for a stand alone away from the corners and
then place it into the corners to see what effect it has over-all...

Also one could extend temporarily the width of the baffle board...
assuming the initial material was a ridged plywood ...with a very
easy to work with material like thayerg suggests just to see what effect
that would have...the original board should be ridged enough to
resist the vibrations of the B200 drivers and the side "pieces" would
merely function as experimental extensions...

The other thought I had was side pieces made from the same
ridged plywood as the initial board that could be hinged...perhaps
a piano hinge which might prove somewhat stable...when the Dark
Star was not being played the side pieces could be folded back out
of the way...then folded out again when the speaker was being played...
perhaps that might help with the WAF...

This thread is moving rapidly into a very creative direction...

Warm regards -Richard-