Hi,

I have 3.5" coax in the dash and 4x6" coax in the rear. right now i set the x-over in my HU to cut off the dash speakers at 168HZ and the rear at 120Hz.
Does this sound right or can i go a little lower?

thanks
J

 

Depends on the speaker's capabilities. Naturally, a smaller speaker will be prone to playing higher frequencies, but the build quality will effect how effecient the speaker is at playing the lower tones. Best way to tell is to fade to front, play some songs or sine sweeps and listen to the speakers. Listen for when they start to lack fidelity, and set your roll off accordingly. Rinse and repeat for the rears.

 

thanks, i have a hard time to figure out what slope to use though. is there a simple rule of thumb for this?

 

Not really. It comes down to what you are looking for in terms of sound quality. Everyone has different sonic "tastes" so that's why I suggested tuning by ear. I don't get the impression you're trying to get the perfect soundstage and fidelity, so tune it until you feel it sounds right. Best way to select a slope this way is to play a series of sine waves at just above your regular listening volume from say, 200Hz, and continue to select lower frequencies until you hear the break-up in sound. Set your slopes at whatever freq you can on your deck that is closest to the clean sounding waves. If you don't have access to a CD with different sine waves on it, use the music you listen to the most, and select the slope that sounds cleanest.

 

Sounds about right. What are your slope options?

 

flat, 6, 12, 18, 24 (dB/oct.)

 

Wow that's a good selection, what head unit is it? Basically the steeper the slope the closer you can push a driver to the edge of it's envelope. With a 24dB/oct. slope your chosen crossover points should be good to drive those speakers with full rated power without worrying about bottoming out. Like mentioned above you can experiment with test tones to verify.

What make and model are these speakers?

 

I would most likely run a 24dB slope up front and a softer (18 or 12) slope for the larger rears, both at whatever frequency sounds right based on the tones. kevmurray brings up a good point I missed there about the slope itself. The more aggressive the slope, the more aggressive you can be with the freq's the driver sees

 

Head Unit Alpine CDA 9833

Front
http://www.futureshop.ca/catalog/proddetail.asp?logon=&langid=EN&sku_id=0665000FS10 088308&catid=

Rear
http://www.sonicelectronix.com/item_6473_Alpine+SPS-46C2.html

 

First link didn't work, but the rears at 120 with an 18dB slope would be my setting. For the fronts, they range on the low end from 43Hz up to 93Hz as far as how low they can handle, but I would be inclined to set it around 120 to 170 with a 24dB slope. That would have to be tuned by listening. Having so many possibilities with the Future Shop products, I have to give that range. Seems like you are there anyways