crossover questions for relative newcomer

[paul3221]

Hello all,

I have been eyeing the Aurum Cantus 165 driver on Parts express for a while now, and it's on sale in the new flyer, so I think I'm going to take the plunge, and build my first 2 way speaker pr. I was thinking of pairing it with the Morel MDT-12 in a tall, thin, ported cabinet to try to get as close to the 32hz low end as I can.

I've been reading quite a bit lately, but am still a little fuzzy on crossover design. I was thinking of doing a 2nd order at 2500hz, thus avoiding the wierd spike at around 5000hz on the woofer (here). Does this seem like I'm on the right path? Would the experts here do it differently? Possibly crossing over at a different frequency? Using a first order, as opposed to a 2nd order? I'm assuming I'd have to cross over higher with that tweeter to do a first order. Is there another tweeter that someone here knows of that may work better? Any input or advice is greatly appreciated.

Thanks in advance,
Paul

[paul3221]

While reading the crossover section of Introduction to Loudspeaker design, John Murphy recommends using first order crossovers wherever possible. Would that work with the drivers mentioned, or would it have to crossed over too low, and damage the tweeter? Would people here still recommend a 2nd order crossover? Maybe some sort of hybrid design (1st order for woofer, 2nd order for tweeter). Any input is greatly appreciated.

Thanks,
Paul

[tomcat9]

In a 2 way design like you have suggested, 1st order crossover is usually not a good idea. The drivers are already covering a large portion of the audio spectrum, and a 1st order just makes it worst. Go with a 2nd order, or higher.

[PeteMcK]

I'd use a notch filter to deal with that peak:
http://www.diyaudioandvideo.com/Calc...otch/Help.aspx
for protection of the tweeter, you're better to stick with 2nd order; 2500Hz looks about right as the xover freq

[paul3221]

has anyone here used the Dayton Audio crossovers that come pre-built from Parts Express? They use a 2nd order L-R design, and seem to get good reviews from the users on the site. Thanks for the input so far.

Paul

[PeteMcK]

pre-built crossovers are evil..... they are built for nominal impedance, and won't match the actual impedance of your drivers... they will work, but will be far from optimal.
How to procede if you can't measure the impedance: Look at the impedance graph on the data sheet supplied by the manufacturer, use the impedance value at the crossover frequency, and plug that into a calculator such as this: http://ccs.exl.info/calc_cr.html#second
Then you'll need to add an L pad for the tweeter, and a BSC Inductor for the woofer...

[paul3221]

Originally Posted by PeteMcK

How to procede if you can't measure the impedance: Look at the impedance graph on the data sheet supplied by the manufacturer, use the impedance value at the crossover frequency, and plug that into a calculator such as this: http://ccs.exl.info/calc_cr.html#second
Then you'll need to add an L pad for the tweeter, and a BSC Inductor for the woofer...

Thanks for the feedback. So, if I'm reading this correctly, the impedence for the woofer at 2500hz appears to be around 14 Ohms, and the tweeter seems to be around 5.5 or 6 Ohms?

Will I still need the L pad if they are both 89Db units? Is it always a good idea to use one?

[PeteMcK]

If you add BSC, you'll loose some sensitivity in the woofer, which means you'll need an L pad to even up the tweeter level... try it without either first, you might like it that way :-)