X-over bandpass values

[angeloitacare]

hi

i want to try out a Vitavox S2, 15 ohm,bandpass between 500hz and 1500hz, first, or eventually second order.
Below S2, Fane Studio 8M, 8ohm . Above , Beyma TPL-150, 8ohm . I googled, but did not find a site to find out coil and capacitor values for bandpass the S2.

Someone can help me out ?

Angelo

[wintermute]

Hi Angelo, to get a band pass you basically put a high pass and a low pass in series. So you would put a 500Hz high pass and a 1500 Hz low pass in series, any of the calculators you use for a two way crossover should work fine. I use this one: Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)

Tony.

[Boden]

Angelo and Tony,

These standard calculators will most likely not produce the desired results.

For a proper calculation of component values of a bandpass with such close x/o frequencies you will definitely need good measurements of the SPL plus impedance curves of the driver in its enclosure, then plug the .frd ( spl measurement curve) plus the .zma (impedance measurement curve) in a good x/o simulator.
Because of their optimizers, SoundEasy, Calsod, LspCAD and LEAP will do in its seconds. You simply indicate the target (=ideal) filter curves you want, plug in starting values of the filter and the program does the rest, to make a long story short.

The x/o freeware such as Jeff Bagby's or Visaton BoxSim do not have optimizers, so it will take much longer since you have to do it yourself with trial and error by changing the component values of x/o. Personally I do find that a pain in the neck plus a waste of time. But he, it is all for free then!

Good luck,

Eelco

[wintermute]

Good point Boden (on all fronts). Though Speaker Workshop is an exception on the free-ware front, in that it does have an optimizer, and I've found so far that the crossover simulation is very accurate. If you consider using Speaker Workshop I'd highly recommend The 2nd addition of the Unofficial Speaker Manual. by Jay Butterman, and also Claudio Negro's site.

I too would not go down the route of trying to design a crossover without measurements of the actual drivers mounted on the final baffle, but many do.

The calculators as Boden say's will give you a starting point. But the filter combined with the drivers unique characteristics in your implementation, are what give the actual acoustic roll off (which is what is important).

If you haven't done so already, this thread is well worth a read: Introduction to designing crossovers without measurement even if you do intend to do measurements

Tony.

[Boden]

One caveat remains, no matter how sophisticated the software.With the x/o points so close (500/1500 Hz), there will be some interaction between the -3dB points. (or -6 dB foor L/R filter types) of the bandpass filter.

My guess is you will lose some dB's in the pass band as well. This is exactly why any crossover should be simulated and viewed on grafic display before grabbing the component-box and heating up soldering iron.

Eelco

[angeloitacare]

Tony and Eelco

thanks a lot for the explanations. What i want to do, is a quick experiment, nothing complex or very accurate. If i loose some db's, that is even welcome, since i will need to pad down Fane Studio 8M, and S2, to equalize to efficiency of the Beyma. I have a fostex scale which indicates me all capacitor and coil values for determined xover filter. For 500hz, second order high-pass, it indicates 20mF in series, and 5,4mH coil in parallel, while lowpass at 1000hz its just 2,5mH in series. So i just sum up the two values, and put 12,5mH in series, right ?

Angelo

[AllenB]

If you want the second order high-pass and first order low-pass then you should keep all three components . Although they will interact to some degree, and also possibly not work as expected due to the complex impedance of the driver, you can experiment with what you have there.

[angeloitacare]

this morning i hooked the S2 up with , using 10mF cap in series, and 5,5mH coil parallel , and L-pad. I like what i hear. I will wait measuring instruments to arrive, measure the response , and refine crossover. I was thinking to sell S2, but i rather keep it now, and use it in the mentioned frequency range.
I will use the Beyma where Coral H104 used to be installed, and adapt the wave guide i am making for it, to fit the space.

Angelo