Installing components w/o an amp or crossover
 

Quick question for the audio gurus:

I'm helping a friend install a new set of component speakers on his car this weekend (8th gen civic). He doesn't have an aftermarket deck or amp powering these. My question is do we need to install the in-line crossover on the new speakers?

I'm thinking probably no, we can just wire the mid range drivers in the factory door location and the new tweeters in the factory tweeter location. I'm under the assumption the stock head unit/amp is already sending the right signals to each location.

I know this isn't the best way to go but can't convince him to spend the money on a new deck yet.

Any thoughts?

The factory wiring being crossed-over in the amplifier is not common in any honda vehicles. To check for this have a look at the factory tweeter itself. If you see a small capacitor attached to the tweeter itself then the signal being sent to it from the amplifier is full range and that small cap is the factory honda passive crossover. If there is no cap then it is likely crossed over however, the factory honda crossover frequencies may not be what is optimum for your aftermarket tweeters and wiring them as so could cause damage to the tweeters. The only way to be certain of what the crossover frequencies are is to RTA them to measure the frequency range of each individual channel. The included crossovers are optimized to work with the drivers they came with so you would most likely notice better sound if using the included crossovers. Not to mention we do not know the continuous power output of the factory radio or amplifier so it is possible to overdrive them without knowing and damage your aftermarket tweeters. The crossovers function as more then just frequency separation they also will include tweeter protection in most cases.

Thanks Nate.

So do you think I could wire the crossover off the current woofer's wires (and route that to the tweeter) to avoid pulling out the headunit or is there no getting around it?

Edit:
He just brought over the speakers for me to look at. Looks like the crossovers are only for the tweeters. In the package wiring diagram they have wires running straight from the amp to the woofer. Then you hook up the supplied wires with the in-line crossovers to the woofers and run those to the tweeters. So I think I can try tapping the stock tweeter wires into the new ones (with crossovers) and to the tweeters. That should help make the install faster and easier

The only problem I could see with that is your stock woofer may have a low pass filter at the amp, matching the high pass at the tweeter. Not likely, but possible.
Lets say your woofer has a low pass at 1800hz, and the tweeter has a high pass at 1800hz, now you wire your aftermarkets in, so your woofer still cuts at 1800hz, but your aftermarket tweeters crossover is high pass at 3000hz. You would miss out from 1800 to 3000hz. Probably not as great issue, but if you are a discerning listener, you may pick up on it.......

I used to have an 8th gen civic.

The tweeter does have a capacitor. It is receiving full range from the Amp (the honda civics come with an amp below the deck just in front of the shift lever).

The stock woofer also gets full range.

Problem solved.....

Thanks for the input guys. I ended up running it off the new woofer as the installation instuctions said and left the stock tweeter wires untouched. This will make it easier if he ever changes his deck or wants to put his stock speakers back in to sell.

It worked great and he's happy. thanks again for the advice.