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Visaton B200 with Rythmik Audio Servo sub (finally)
 

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24db built in to 350W plate amp.
B200 will be run from Charlize class "T" with a -3db filter ~ 70 hz.
Sealed sub, space because I wanted a specific footprint for the enclosure / baffle, there is a spacer which also acts to help support the sub enclosure. Finish (yeah right) will be a natural varnish. I have not played the subs yet, I just tried to put everything together this weekend, its been maybe 2 months just to get this far.

I'm off again on an ironbird tomorrow so will have to wait for next weekend to actually hear them with the subs. The B200's on their own are nice:)

Andrew
 
Honey I'm home!

I played with the ob's for a few hours yesterday. The subs are nice:)
The B200's need work. The speakers are too close to the (live) rear wall and there is too much sound being reflected. I plan on putting some fibreglass or polyester batting
across the rear of the speaker to kill some of the rear sound output.
The problem is to move them around 5 -6 feet away from the rear wall would mean moving them for every listening session and they are not exactly lightweight, I may end up putting some castors on them.
I also need to build the filter for the B200's to start their rolloff at ~ 70 hz.
So, for now they show promise but I miss my Jerico's with the 208 Sigmas', even
without the newfound tuneful bass, and what a bass it is!

Andrew
 
Nice looking system! There is something very nice about the sound of a wide/fullrange + sub. I am running the rythmik right now with WR125s and after tweaking the balance with sine sweeps through the XO region, the sound is very nice and extremely dynamic. BTW, I encorage you to try moving the crossover up... I have been able to get up to about 120hz, and the servosubs sound very clean crossed that high, plus removing the bass from thee fullrange drivers really helps them, much more than your typical two way.
 
Hi Morbo,
Thanks for that, I never considered crossing over that high, I suppose with stereo subs I can probably get away with it. Maybe I will try crossing up higher, the filter I had in mind was of course to do just what you say, free the fullrange driver and let it work it's magic unimpeded by bass. There is in the servo sub amp a highpass @ 100hz, I think it passes through an opamp, not sure, but why not, its worth a try.


Andrew
 
Andrew.. for curiosities sake would you do me a favor (assuming you have the materials on hand and some spare time)?

Try the B200 aimed up at the sealing in a very lossy "large" box pulled relativly close to you, (closer than normal.. say 6 feet away) and with the driver effectivly around 70 degrees off-axis from you (..still visible, but just barely).

In otherwords in "omni" fashion, not unlike the speaker here:

http://www.6moons.com/audioreviews/fj/om.html

..though in a larger box and without the tweeter.

I think you could get the "flavor" of this configuration with something as simple as a cardboard box, (perhaps dampened with a pinned-up blanket around all the side panels - including the hole), with a very large round or square hole in the backside panel.

Now I realize that treble response will suffer (significantly even), but I think its likely, (..or I wouldn't have suggested it), that you will discover something special that you might find addictive, and that could "pave the way" to a design far more to your likeing.
 
Scott,

I saw that design thought many years ago. (In a slightly differenent form) the first was in a pair of speakers that were part of a Zenith stereo my mother had in the 70's. The enclosures were cylindrical, can't remeber if there was a bottom but the single ~ 6" driver faced upwards with a white, conical shaped piece of plastic from the middle of the driver that was perhaps a foot or so long. It was not a typical cone shape but maybe an expotential shape? Geez, it was a long time ago.

Dick Olsher also did something similar sans the plastic cone with the Samadhi designs.

That makes an interesting idea but my baffle looks so nice (shameless blowing of ones own horn here:D ) that I need to get the OB's working properly.

Ron Clarke who posts on the FR forum has been working on a single driver horn with a somewhat similar theme where the driverfront output reflects off of a part of the horn at ~45 degrees.

There was a Lowther cab many years ago which did something like this with I think it was 2 drivers. I can't remember the name presently but it stood on three legs and was corner placed and it regarded as the Lowther cab of all Lowther cabs.

I am short of wood and space to keep these speakers. My "Afterburner" cabs meet their maker this weekend and join the rest of their family in speaker heaven.

Your idea has been done and does work, I am just trying to get away from boxes- horns excepted.


Andrew
 
Nuuk said:


Scott, surely there will be a big difference as the OM's use a tweeter crossed over at 2.2 Khz! So everything from there up is directed toward the listener. With a full-range, if you use a helper tweeter, it will typically come in at around 10 khz. Or have I missed the point? :confused:

I've tried discussing the basis behind why this design not only sounds better, but is more accurate - alas, most were too resistive to the idea (either thinking I was bashing SL, or perhaps something even more insidious), or they simple were not interested.. and I didn't want to post a treatise on the subject. (Note the thread was a "Second look at SL's Pluto", or something like that.. in the Loudspeakers section.)

Yes and no (as to the big difference).

You see the B200 has a rising response pretty much where it needs it to give a fairly flat response up to 2kHz+ in this design. Additionally the attenuation at higher levels subjectivly will be lessend because of the reflected energy. Still, you are correct that either a waveguide or an additional tweeter or fullrange (or some combination) will be needed to increase the spl at higher freq.s (or a "filter" which I wouldn't recomend).

Now the OM's do use a tweeter to correct for the loss in spl, but everything from there is not "directed" toward the listener.. at least not as you might think. In truth the Hiquphon tweeter is essentially omni directional up to 8-9 khz. Additionally, because of their low moving mass relative to a midrange or larger driver, the tweeter doesn't pressurize the air the same.

As to the principal of a full-range driver (at least as we accept it here), unless a filter or a waveguide is used, yes - the B200 isn't being utilized as a fullrange driver. Used properly though, it will still have some of the better properties that a good full range driver provides (while significantly suprasing it in many areas).

In particular this driver (used properly) will not need ANY filtering. No high pass, no low pass, not even baffle step compensation (which most fullrange drivers really need - even dipoles, though it isn't baffle step but rather phase cancelation). The loss in spl due to baffle loss is effectivly raised up in freq. and works to provide a low pass character where you would normally cross-over to a tweeter.

Additionally the lower freq. response of the driver "tailored" to the user's needs. If you want dipole operation.. you can have it. If you want an aperiodic box (with perhaps an acoustic high-pass character).. you can choose this instead.
 
OK, thanks for taking the time to cxlear that up. I asked because I ahve my Ciare 250's here doing nothing, as well as a spare pair of tweeters. So if I can find the time, I could give it a try!

I think you could get the "flavor" of this configuration with something as simple as a cardboard box, (perhaps dampened with a pinned-up blanket around all the side panels - including the hole), with a very large round or square hole in the backside panel.

So, we have a box with a hole in the top for the driver, a small one in the front for the tweeter, and a big one in the back. Can you give an idea how big the rear hole is? I guess with a big hole in it, the size of the box isn't too critical! ;)
 
Andrewbee said:
Scott,

I saw that design thought many years ago. (In a slightly differenent form) the first was in a pair of speakers that were part of a Zenith stereo my mother had in the 70's. The enclosures were cylindrical, can't remeber if there was a bottom but the single ~ 6" driver faced upwards with a white, conical shaped piece of plastic from the middle of the driver that was perhaps a foot or so long. It was not a typical cone shape but maybe an expotential shape? Geez, it was a long time ago.

Dick Olsher also did something similar sans the plastic cone with the Samadhi designs.

That makes an interesting idea but my baffle looks so nice (shameless blowing of ones own horn here:D ) that I need to get the OB's working properly.

Ron Clarke who posts on the FR forum has been working on a single driver horn with a somewhat similar theme where the driverfront output reflects off of a part of the horn at ~45 degrees.

There was a Lowther cab many years ago which did something like this with I think it was 2 drivers. I can't remember the name presently but it stood on three legs and was corner placed and it regarded as the Lowther cab of all Lowther cabs.

I am short of wood and space to keep these speakers. My "Afterburner" cabs meet their maker this weekend and join the rest of their family in speaker heaven.

Your idea has been done and does work, I am just trying to get away from boxes- horns excepted.


Andrew


I know of all but the Zenith. And there are quite a few more designs that went into production as well.. recently Mirage and B&O (in addition to the Om - which looks almost exactly like DO's Black Dahlia). (SL's Pluto should be mentioned as well, though it really isn't "in" production.)

I can understand time/resource problem as well as the desire to complete your project. My request certainly isn't inteded to preclude finishing what you have started, but to suggest that at some point after you have finished finalizing* your current design that you try pulling out the drivers and using them as I've suggested and reporting back your results (..provided you have the time and the materials).

*(or if you want a break from it - try it out while you are continuing with the project.. but certainly continue until you have finished it, othewise you would never have a good point of comparison.)

Note that such a design CAN be a dipole - at least down to where it matters most (below the modal region of the room). Much of whats best about a dipole has NOTHING to do with its radiation pattern - and you can preserve these qualities with a directed dipole or most of these qualities with a good aperiodic box.

Oh.. try looking at Peder's rendition of DO's Basszillas (don't get to distracted looking at his 3-phase power supply PSE amps - you'll go blind).

http://www.arduman.com/aa/Sayfalar/peder/peder.htm

Asthetically they are one of the better "final products" I've seen based on this design.. And not incedentally, they are quite similar to your own.
 
Nuuk said:
I guess with a big hole in it, the size of the box isn't too critical! ;)

weeeelllllll.. it is pretty important (the size of the box that is) unless you have REALLY good internal damping on the interior panels of the box, or you use a directed dipole technique. Of course the problem is you wouldn't do either for a simple mock-up. The reason is partly because of the resonance the box will create, but mostly because of the reflections the box will bounce back to the diaphram (which you want to avoid - while still avoiding air flow resistance that most damping materials will cause when near the driver.. giving that "lifeless" sound). With the big hole though you do avoid back presssure on the driver that causes over'damping and ressonances in the crossover and down the "chain").

remember to make sure to cover the hole with a lossy material (fiberglass, a blanket, etc.) though or you will end up with something aproaching a TQWT with some disturbing resonances.
 
And not incedentally, they are quite similar to your own.
I bought the plans as soon as I had heard / seen them and thought why did'nt I think of that!

I liked everything in the plans except the reflex box. I even had the (and still have the FE208 Sigma's). I had intentions of building them but iirc the woofer became obsolete or in any case became pretty hard to source.

I played some more with my ob's tonight. pulled them ~6 feet from the rear wall, 6 feet between each other and about 30 inches from the side walls.
Also put some eggcrate foam over the back of the B200's. VERY Nice. Imaging that was out of this world, had some horn player way to the left of the left speaker who was particularly good ;) along with his cronies between the speakers but deep behind them as well as others who were in the speakers and even others who were behind the speakers. Astrud was also here singing just for me!

These B200's are superior imo to the FE208 Sigma.
Also lowered the sub crossover and output. I made a pair of filters for the B200's which should be -3db ~70Hz but have not installed them yet, trying to see how good I can get without them, truth be told I am not sure I will need them with the B200's, as they are designed to make bass, a low Qts Fostex or similar would need them though.

Now back to my regular programming, non-fiction - Webers, art of the grill.
 
Andrewbee said:

These B200's are superior imo to the FE208 Sigma.

from the posts I've seen on the driver, that does indeed seem to be the general concensus.. In fact I think at its price-point it will likely be very difficult to beat provided the user can accept a more moderate driver eff..

anyway.. good luck with the refinement process (..and the grilling :hot: ).
 
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