# Need help with a passive crossover



## supermaxx123 (Jan 4, 2010)

I want to build and mate these 2 drivers in a T-line enclosure. 
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-372
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-1012

I was thinking of a crossover at 2khz with 12db slope. I've never really dealt with crossovers other than an adjustable digital one. 
I was wondering if that would work well. 
I can't find one that will work on that site, does anybody have any sugestions?


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## Anthony (Oct 5, 2006)

A couple of things: one, Parts Express will help you design a crossover for their drivers. Call them up and ask for some speaker building help. They are very helpful.

Two: 2kHz is smack in the middle of the most sensitive region of human hearing (1kHz-3kHz). If you can avoid it, you should try to stay out of this region for a crossover. However, for a 2 way speaker, this is almost unavoidable unless you have a high-end tweeter, or a very wide-band woofer/midrange speaker. Usually the trade-off is cost (for the tweeter that can play lower) or bass response (for a woofer/mid that can play higher).

Sadly, I have done more with sealed and open baffle, not TL enclosures, so I'm no help there. Hopefully someone else will chime in with some experiences.

Good luck and keep us posted!


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## Derry (Apr 10, 2010)

give this site a try to see what all is possible,, you can enter any HZ you want and it will figure out the components as well offering many different type crossovers and orders,,

http://www.diyaudioandvideo.com/Calculator/XOver/

Derry


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## Anthony (Oct 5, 2006)

The problem with that is that it assumes a constant impedance for the speakers. This is almost never the case. It might get you close, but if there are any impedance bumps, breakup modes, or other non-linear responses of the speakers themselves, then the quick-crossover calculator won't work.

There are some free Excel tools from the FRC consortium. Kinda tough to get the hang of, but you can import driver models and play around with crossover design. There are also pay software packages that do similar things. The Parts Express guys use Sound Easy, I think.


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## villastrangiato (Apr 15, 2010)

You may want to consider a third order electrical slope to head off a distortion peak in the RS150 at around 3.2khz. You might find the 12db per octave slope is not enough to effectively suppress this. Also keep in mind that although a properly designed/built T-line is one of if not _*the*_ most effective way to optimize performance from any woofer, the RS150 with its very modest Xmax may still be a little disappointing for bass duties. If it were me, I'd bump up to the RS180 if I wasn't planning on adding a sub. The Xmax for that driver is significantly higher and the T-line will really bring out that improvement. Using this driver would require a 4th order crossover down closer to 1.5khz to deal with the onset of distortion at around 2.3khz. Given the XT25's low frequency limitations, if you haven't already bought these drivers, I'd go with the pairing of an RS180 to a SEAS 27TDFC or Dayton RS28. These two driver's have been used extensively in a variety of projects (Modula MTM and Natalie P come to mind) so you could actually build a crossover without "reinventing the wheel" and you'd have a stellar performer. Don't get me wrong, I love the Vifa Xt25 and I consider the RS 150 to be a fine bass mid (more mid than bass) but the breakup in most straight aluminum drivers places strong limitations on their midrange usability. The optimal design using the drivers you've chosen should seek to drive the crossover point as low as possible and with the Vifa's limitations below 2khz, you're hand is kinda forced. You really need a third or fourth order crossover if you're planning on staying with the drivers you've selected and a 2khz crossover point. A notch filter could be used with the 12 db/oct filter but you'd be pretty close to the 3 rd order crossover component count anyway. If you're planning on adding a sub later, I'd consider a simpler bass alignment for the RS150 and put the energies of building a high performance transmission line into the sub.


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