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trespasser_guy 21st April 2003 06:56 PM

crossover/box design help needed
I have two Eminence Alpha-8A's, and two Selenium DT150's, that I intend to make a pair of 2-way speakers out of. I am thinking about crossiing over at 2500Hz. Is there anything wrong with crossing over here? Should I go higher/lower?

If this point is fine, I have found the values for the low pass and high pass on the PartsExpress page to be .72mH and 5.627uF. Are these the correct values for a 2-way, 12dB/octave xover at 2500Hz? When I use an online calculator, I end up with values not anywhere close to this.

On the box: I see the Vas of the Alpha-8A is .5 cu.ft. I intend to put it into a 1.1 cu.ft box, but do not know if it should be sealed or ported. I would really like to get some lower response out of these speakers... they are only good to about 80Hz or so, it looks. If I ported it and tuned to 55Hz or so, would I get more response down low? Is it worth it? Should I just leave it sealed?

I am at school right now, so I don't have any of my info with me... if any of thatw as wrong, that is why. Thanks for the help. :)

Battlepriest 21st April 2003 07:11 PM

Forget about these calculators, they'll never work if you long for satisfying results!

Formulas only work fine with ideal drivers: flat frequency response, linear impedance, no resonances of the surround and the cone material, no diffraction, no baffle step. what a pity, no one ever managed to build such a driver an a fitting cabinet ;)

What you need to simulate a fine workung crossover, are meassured frequency response and impedance plot in the destined cabinet. Even the place you'll put your driver in, is of importance! When you've all done, you will probably see, that even the simulated XO is not as perfect as simulated! DIY speaker building is a painful process. somewhat a hobby for masochists? *gg*

IMHO 8" drivers are a bit too big for a 2way XO at 2500Hz. Look here:

trespasser_guy 21st April 2003 11:30 PM

Ok... I have adjusted the xover a tad. I am now looking at 2000Hz, instead of 2500.

The values I have for this are: inductors- .9mH, caps- about 7 (7.02)

I have been wanting to make a pair of speakers for a long time... but have always given up because I don't understand the xover, and cannot find anything that helps, really. I have a speaker modeling program, but couldn't use it for the life of me.

The tweeter is significantly more sensitive than the woofer... the woofer is rated as 97dB. On the Parts Express page, it shows its response going up to 101dB at 2000Hz. However, on the Eminence page, it only shows 97. Which is correct?

What is basically the bare minimum I can use to get a great sounding pair of speakers going, xover-wise? This is all that is holding me back... all that ever held me back. I never can get one answer that will make me confident enough to take the plunge and buy the xover parts. I am on a VERY tight budget and cannot afford to have mistakes where $20 worth of parts are no longer useable. HELP! Please!

Thanks all

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