band pass crossover application

I'm a new user and a relative novice to car audio. The postings I've scoured haven't really addressed my issue. I've installed my own remote-start/entry/alarm in my 2006 Ford E-250 van and I'm a service tech for industrial air compressors, as well as a very minor hobbyist in the world of electronics. I.E. I can tackle whatever project I decide to, I just want to scope this one out.

I've bought some upgrades to the factory setup in my service van. There is a sheet metal partition right behind the front seats so my cabin is limited. The new HU will be a Panasonic CQ7103 w/ 50Wx4 and sub pre-out. The door speakers will be Infinity Reference 6812 (2) complemented by a Kenwood Powered sub (KSC-SW1) and Infinity Reference 1011t 1" silk tweeters (2). The sub and other components were chosen mainly for space and cost/convenience considerations. I don't want to spend too much time or money on this system, but I don't mind sinking my teeth into the learning experience of trying to optimize it. Since the sub has its own amp and internal crossover and the tweeters come with a high-pass cap filter, my thinking is to add a second-order band-pass crossover to the main 6812s. Anything wrong with this approach? And since I was unable to find an off the shelf product to do this, I'm trying to spec the components . It would seem I need to high-pass at 120 Hz (the cut-off of the sub) and - this where its murkier for me - low-pass around 2500 for the tweets. Basically, I think I want a passive band-pass CO for the HU-powered mains to spare them the lows and the highs. The 120 Hz for the subs seems like a clear spec to me, but 2500 seems low. Should I be looking to spec a higher low-pass point? If anyone knows of a supplier for such an animal, I'd probably go that way, but I'm kinda liking the prospect of crafting a couple of small circuits to get what I want.

Hi there.  Your approach is good, but you may not have to build a full BP filter network.  Does your HU have high-pass filters for the main outputs?  If so, set them to the same as your subwoofer LP.  Also, if it was me, I'd use the LP in the HU that is sure to be available for the sub output and defeat the one in the sub amplifier, just to ensure your sub LP and your main HP are the same.

According to the published specs from Infinity, your tweeter is supplied with a 2.5KHz HP filter.  This is a fairly normal crossover point, by the way.  If your HU has a HP for the mains, you now simply need to add a passive LP to the main speaker that matches the setpoint and slope of the tweeter.  I can't find the slope for the supplied crossover, but I suspect it is at least 2nd order if not 3rd order.  You may also have to pad the tweeter since I doubt the efficiency of your mid-woofers is as high as the efficiency of the tweeters.  Use good quality Xover components (poly caps, air-core inductors) for the LP filter.

Wait, you say you are using Infinity 6812's as your mains?  Those are coax speakers and already HAVE a tweeter.  Why do you want to add a second tweeter?  I do not recommend this.  You'll get far better and more controlled sound using just the coax set.  Adding tweeters often causes much more harm than good due to cancellation effects and over-emphasized high end.  Mount the 6812's with the tweeter pivoted towards the listening position and you will be fine.  Forget the add-ons: sell them and get a better subwoofer!

Hey DYohn!

Many thanks for the quick and detailed reply! That's what I get for thinking I guess. I just assumed that investing in some relatively inexpensive tweeters would spread the load and permit the coax mains to focus on a a lighter load. But I will defer to your better judgement. Also, the Panasonic CQ-C7103U head unit has no high pass for the mains. It does, as you correctly assumed, have an adjustable low-pass for the sub (at 80, 120 or 160Hz). Do I still need to defeat the sub's LP? And will I benefit by adding a passive HP filter to the mains (or will the HU take care of this with the sub LP setting?)

I chose the sub I did because of its size and my perceived lack of a need for more bass output. I did look at a couple of others (The Infinity Basslink and Basslink T to be specific) but figured I'd save space and cash without much sacrifice this way. Since I probably have time to change my order before it ships, should I stick with this sub and spend the tweeter bucks another way or go for another sub. One last question please by the way, The HU SAYS it puts out 50W x 4. Since I'm only using two mains, do you have any recommendation to go with an external Amp. Keep in mind I don't need teeth-rattling bass - I'm going for quality vs quantity. Thanks again. Great site by the way.:^:

kennymo