[Deda]

Hi from a new member.
This will be another B200 thread, which obviously don't lack here on forum:)
As I already own pair of 12" sealed subs with F3 of 30Hz, and lately I was thinking of going OB, I thought of adding B200 in OB above them, something simmilar to Bastanis concept. I thought of crossing them over no higher then 60Hz. Is this doable on a baffle no wider than 50cm or am i just daydreaming?
Thanks in advance

[scorpion]

Hi Deda, Welcome here !

Well, you have put a tricky question. If you are determined to use the B200 anyway. Then just build some testbaffles and see.

If you don't know, provide us with some sub-data like efficiency and X-max of your units ! Or as many parameters as you have regarding TSP.

From the beginning I would say 60 Hz is way too low. I would like the subs to play as high as possible at least to 150 Hz. That is because of B200's limited X-max and the demand to handle bigger power at low frequencies.

/Erling

[JeffB]

I have 18" baffles.
You can run the B200 full range if you want.
I have the B200 highpassed at 60Hz.
I have my subwoofer lowpassed at 150Hz.
However, I am using an electronic crossover with potentiometers for the frequencies.
I am not sure how accurate this labeling is or what the slopes are.

Richard uses a 4.7mH inductor for a 270Hz lowpass.
See this thread.
http://www.audiocircle.com/index.php?topic=47314.0

[TerryO]

It certainly is possible to do what you suggest, although I believe you should use a wider baffle (like JeffB) which enables you to cross over at a lower frequency. Using a HiPass filter for the Visatons isn't a bad idea either. Just use some 3/4 inch A/C plywood cut to the minimum desired width and then try it out. Add cardboard wings (fastened with Duct tape) of various widths to one side or both, and adjust the Subs crossover point until you get to what you want. Believe me, some Ultra-HiEnd speaker designers (like Magico's Alon Wolf) do exactly the same thing when "they" design. Speaker design is still as much art as it is science, and no matter what, a good design is still tweaked by ear.
BTW: get some Planet 10 phase plugs for your Visaton's, they will take you to the next level.

Best Regards,
TerryO

[panomaniac]

Where to cross?  There are several schools of thought on this.  Let's look at 3.

1) Cross low.  This is the intuitive school of thought.  "I have this great fullrange driver, let's use as much of its range as possible."  The idea is that the FR driver just needs a little help on the bottom end, so we cross low.  Maybe below 100Hz.
This way most of the audio range is covered by a single driver.  The woofer only fills in the lowest ~2 octaves where SQ is less important - and there is no x-over in the critical midrange.  Makes sense.

2) Cross higher.  This is the "Why burden the FR driver with bass?" school.  That's what your woofer is for.  A good example was listening to Nelson Pass' very nice OB system at the recent RMAF.  I was seated right next to Lynn Olson who was dismayed that Nelson had crossed the Lowther FR drivers so low to the 2x10" woofers. About 80Hz, IIRC.  The problem there (for me) was Doppler.  At 80-250Hz the Lowthers on OB will move quite a bit.  That movement will modulate the higher frequencies.  Not hard to hear the effect.  A driver in a box will not move as much, so you won't notice the Doppler so much. (Except for very small FR drivers).  Crossing up higher will eliminate a lot of that effect, as well as other problems. Driver don't work the same way on OB as they do in a box or pipe.

3)  Cross it where it works the best.  This is the school of thought I'm working in now.  E.G. a 15" woofer crossed to an 8" FR at about 900Hz.  Why so high?  Because that is where it works the best for 1st order.  This also allows some phase alignment for driver offset.  Where the x-over point comes depends a lot on baffle size, and also on the drivers.  Reasonably sized baffles have a bass roll off a lot higher than you might think.  The idea is to forget the textbook values and go with what sounds best.  An after the fact computer simulation of what sounds best can often lead to a "oh, yeah, now I see" moment.

As the filter slopes get steeper, the freedom to move the points around becomes greater.  But with 1st and 2nd order filters the drivers will be working far beyond their x-over point, so you need to get it right.

All my opinion and experience, not gospel.  Hope it helped some.