Crossover question

Ok this is my first thread and I am probably going to get owned but here it goes. I have an Alpine 9887 and old school soundstream REF amps a 604 and a 500 i am using boston tweets in the front and Image dynamics 64v.2 mids in all 4 doors. ( subs are not installed yet,...waiting on box.) My question is this. Is it ok to just use the active crossover to the 4 channel at say 80hz 12db slope AND THEN ONLY USE THE PASSIVE FOR THE TWEETER? or do i still need to run the passive to the mid bass drivers? I tried to understand all the crossover mumbo jumbo but just got confused. All info appreciated thanks guys.

Gunny

 

You need to have a crossover (either passive or active) to cap off the high freq. from the midbass. Crossover should around 2500 HZ to 3500 HZ. (Depends on your tweeters)

The midrange (or midbass) speakers are the only speakers with crossovers to limit there low freq. and high freq.

 

Killer
thanks for replying however that brings another question for clarification. What is the use of having crossovers built into the headunit if the midbass should have both a high and low pass attached?

I currently have a passive setup on the tweets I was just using the headunit crossover to adjust the mids. My concern was although this worked will sound quality be improved by running both passives. It sucks that Boston does not provide the crossover points of thier passive crossovers.


thanks again for your help

 

Your Boston should have a crossover built into them for taking the highs out of the midbass speakers as well as taking the midbass out of the tweeters. This crossover is around 3000hz.

Your headunit or amp has the crossover around 80hz for taking the low bass out of the midbass speakers as well as taking the midbass out of the subwoofers.

Most car stereo system are setup with one amp to run the midrange speakers and the tweeters through a passive crossover (like Boston's). Then one amp to run the subwoofers. The reason for this is because the subwoofers normally take more watts to sound better.

 

You did not mention what type of Boston you had but, in the following photo below the 6x9 and to the right of the tweeter is the passive crossover. This passive crossover will take the highs out of the midrange speakers and the midrange out of the tweeters.

http://www.bostonacoustics.com/PDFs/newproduct/S_NPA.pdf

You normally still run an active crossover between the midrange speakers and the subwoofers with the above system.

 

I might be able to shed some light, since I recently moved my system into my Tacoma using a 9887 active. If you want to run active with your 9887, here's what you need to do.

It will need to be set in the active position with the switch physically located on the 9887.

Look up your owners manual, or find it if you have it. Somewhere in there is the page about which way to run your RCAs in order to have the correctly displayed controls for each speaker. IIRC, alpine messed it up in the owners manual and it's actually backwards, the Front Pre-outs end up being the midbass, and the rear preouts are for the tweeters, arrange them however you see fit on your amplifier but remember that you need to know which is which because sending 500hz signals to your tweeters is a quick way to need a new set.

You'll also need to decide if you want to run separate crossovers for the left and right side, or if you want them to adjust the same. This can be found in the functions settings menu for audio (F/R or F=R).

From there, assuming you know to turn your gains down until all your active xover settings are completed, then reset them, just go into your xover settings and figure out where you want to cross them.

Your tweeter will need a HPF, generally in the range of 2k-4k, depending on the tweeter. I'd look up the factory passive xover location and try and get as close to that as possible. Depending on how close you are on either side you can choose to run whichever slope you feel pertinent for said situation.

The midbass will need both a HPF and a LPF, although the HPF is much less important if you dont intend on running them really hard and/or you have a subwoofer. Set your LPF as close to the HPF xover point on your tweeter, that way you have the midbass playing up to a certain frequency, and your tweeter taking over from there, adjust slope there as necessary.

If you're running a subwoofer, LPF your sub at whatever range you want in relation to where you midbass HPF drops off.

The idea with active, is that you can play with your xover points, and fluctuate slopes in order to help blend your speakers together. As opposed to the passive xover, that crosses at only one point, and only at one slope.

There's really no point in running the midbass active and the tweeters passive, unless youre tryin to run a semi-active 4 way stage off the 9887s capability of only doing 3 way, in which case I'd probably cross the subs / midbass active and let the midrange and Tweeters go passively, which still being able to control a bit of added flexibility off of them, albeit only on the more restrictive side of things.

For reference, the way I have mine set up is as such:
Tweeter: HPF - 2.5khz @ 18db
Midbass: HPF - 80hz @ 18db and LPF @ 2.5khz @ 18db
Subwoofer: LPF - 80hz @ 18db
and a subsonic filter set at my amplifier around 26hz

It's alittle confusing at first, but as long as you get a decent setup going at first, the added flexibility is well worth the extra trouble.

Let me know if you have any questions and I'll try and explain it better.