I am very new to the car audio scene and I have a question involving connecting up a crossover network box to a new head unit I bought.

When I bought my car ('86 IROC), it came with new speakers, two 10" subs, three amps, and a crossover network box. I'm replacing the old head unit with a new one (Nakamichi CD40z). The new head unit has three preamp outputs: front, rear, and subwoofer. How would I go about connecting this up to the crossover network box being that it only has one pair of input jacks? I asked a guy at Circuit City and he told me to use a Y-cable to combine the front and rear channels and plug that into the crossover box, then use the subwoofer outputs from the head unit to connect up to the subwoofers' amp. Is this the correct way to do this?

Sorry if that sounded a little confusing, but I'd much rather connect this up myself than pay an audio shop to do it for me.

 

Usually a crossover will have it's own sub-out channel. You'll want to run the sub-out from your deck to the crossover. Leave the front & rear outs disconnected. The reason is because most sub-outs are non-fading and won't give you any weird (or accidental) problems.

------------------
'91 RS 3.1
SSM SFC's
Energy Susp. Hyper-flex kit
GTA Sway bars
Clarion, Phoenix Gold, JL Audio, etc.
Quote "If you can't beat them, arrange to have them beaten."
- George Carlin

 

Rez, what do you mean by "non-fading?" Sorry, but I'm not too knowledgeable about this stuff. Yeah, I should have mentioned the outputs that the crossover box has. It has outputs for the tweeter, midrange, and subwoofers. So, you're saying that I just run the front/rear outputs from the head unit directly into the amps, bypassing the crossover box?

 

Whoa, hold on there. No, don't bypass the crossover. Leave the front & rear from the deck disconnected. You don't need them if you want your mids & highs to have a filtered signal (which you do). Your crossover only takes one input. The sub-out from your deck will provide that. By non-fading I mean the level will stay constant even if you set your fader to all rear or all front.

Now here's a new can of worms:
If your amps all have internal crossovers, you can run the front & rear outputs from your deck straight to the amp and still have fader control from your deck.

If your deck has a seperate sub volume then you may want to run the sub-out directly to your sub amp (assuming internal crossover) so you can still use your deck's sub volume.

Sorry if this is confusing, but there are so many variables to consider it's hard to give a straight forward answer to what will work best for your system without having just about every spec on every peice of equipment you have.

 

Thank's VERY much for clearing that up; I understand now. I have three amps, two 30W and a 250W. Don't amps with crossovers have switches on them for various settings? I don't think that the 30W's have a built-in crossover (they only have a gain control) but the 250W might, it has a little switch that adjusts between +0dB, +6dB, or +12dB. If the 250W does in fact have a built-in crossover, would I just use a Y-cable to "combine" the front and rear channels from the deck into a single input going into the crossover?

 

Your +0, +6, +12 switch is more than likely just a bass "boost" controller, not a crossover. If your amp has a built in crossover it will have settings like LP/HP or 60,90,110 (freq). It sounds like your sub amp doesn't have a built-in crossover. So now that that mystery is solved, you can use the sub-out from your deck into your crossover.

No 'Y' connectors, just the single sub-out from your deck into the crossover. Then a single RCA from each of the crossover outputs to the corresponding amp. Your fade control and sub volume will have to be set at the crossover, but hey that's life right?

Hope I could help.

 

Sorry if I'm sounding like a complete moron, but I have a question about the subwoofer channel you talked about. You said to connect up the sub-out from the deck into the crossover and hook up the crossover accordingly. Does the sub-out from the deck contain all of the frequencies (high/mid/low)? Then, does the crossover box just "strip away" the unneeded frequencies and distribute them to the appropriate output?

I should probably wait until I receive my deck until I ask this next question, but what the heck... if it has a separate subwoofer volume control, would the "regular" volume control just change the volume of the front/rear outputs? If that were the case, wouldn't I have to adjust the subwoofer volume control every time I wanted to change the volume (assuming that I connected up my crossover the way you described)?

I'm probably coming across as an idiot, but this connection stuff is confusing.

 

Another thing:

I should really post this in my other topic on this board but I figured that it'd make more sense in here. The following link explains how to remove clipping from a system using an oscilloscope http://www.andysaudio.com/howto/scope.html . Here is an excerpt from the article:

"If your headunit has subwoofer pre-amp outputs you'll need to test them using a different tone. I usually test subwoofer outputs at a level midway between the crossover points. For example, if your subwoofer outputs are crossed over at 80Hz then you would want to use a 40Hz test tone."

Should I use this procedure to tune the sub-outs even though they are the only input going into the crossover? Wouldn't that tune for clipping just at the low-frequency end? Or, should I use the explanation preceding that paragraph (follow the link)?

 

On the decks that I've seen what you said is correct. The subwoofer channel contains all of the frequencies. You would have to read up on your deck to make sure. The seperate sub level control acts less like a volume, and more like a bass or treble control. You can turn it up or down relative to the main volume, but it will still go up & dn with the main volume. Make sense?

If your deck's sub-out actually has only low freqs, then:
Your deck has an internal crossover which means you can run your sub-out directly to your sub amp.
Also:
If that's the case you would run your rear out to the crossover, and just use the crossover for your mids & highs. You could use Y connectors to make sure you have a full front & rear signal, but I don't think there are many recordings that seperate front & rear, in other words, you could probably never tell the difference.

Keep the questions coming, you're making me think!

 

Thank you soo much REZN8R, this is actually starting to make sense now. I'll keep you posted on how this works once I get my new deck.

I'm not sure if you saw my previous post dealing with tuning for clipping using an oscilloscope...

Let's assume that the deck's sub-out did include all of the frequencies. Would that excerpt still be the desired way to tune for clipping? I was thinking that that would only tune for the lower-frequencies, but I could be (and probably am) wrong.

Again, I really appreciate all of the help you're giving me.

[This message has been edited by blue86iroc (edited July 31, 2001).]

 

Yep, the paragraph you quoted would only be correct for a low frequency only application. Glad I could help!

 

You're probably sick of me asking all these questions

How would you recommend tuning for clipping if I use the sub-out from the deck? Should I just choose a midrange frequency and tune using that?

I stopped in an audio shop today to look at the head unit I bought on eBay. It turns out that the deck doesn't have a built-in crossover OR a subwoofer volume control. Because of this, the guy there said that I need a three-way crossover, yadda yadda yadda. Is that really necessary? I'm guessing that he told me that just so that I buy their crossover box. The only discrepancy with your method is adjusting for clipping on the sub-out channel (and the purpose of this post). Thanks.

 

Ummm.... You have a 3-way crossover.

As far as level setting goes, I usually listen (don't have an oscilliscope) to a test track that goes from 20,000 to 20 hz. They have a bunch of test tracks like that on the Bass MeKanic CD I have. That will let you hear any distortion at any frequency, and will also allow you to adjust for peaks & valleys in sound.

I don't mind the questions, I'm sure there are probably other friendly 3rd genners learning something from this stuff too.