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Postby sahelee » Thu Sep 09, 2010 9:43 am

How to connect a woofer in my car? My car radio has output 4x45w. I have four speakers at present (2 in the front and 2 in the back) and I want to put a sub woofer. Is it possible to connect it without disconnecting my current 4 speakers and can it be connected without amplifiers. I haven't the woofer yet, but i am going to buy one. I only know that the woofer max power is 400w. Please answer fast..
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Last edited by sahelee on Mon Sep 20, 2010 5:42 am, edited 1 time in total.
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Re: woofer

Postby DVDdoug » Thu Sep 09, 2010 5:41 pm

Yes, you need an amp.*

This is a bit tricky, and you might want to visit a car stereo shop for help & advice (even if you buy online and install it yourself). I think you can find an amp that takes care of all the following issues, or you might need some additional stuff:

1. Most amps need a line-level signal. If your stereo has line-level (or "preamp") outputs*, that's good. If the stereo only has speaker outputs, there are two or three possible solutions - Look for an amp that has speaker-level inputs, or get a speaker-level-to-line-level adapter, or get an amp with a volume control (or "gain" adjustment) and hook-up to the stereo's speaker outputs and adjust-down the volume as necessary. NOTE - If your stereo has "balanced" or "bridged" speaker outputs (without a common ground) do NOT connect the speaker-outputs to a line-input (with a ground) as this can blow the stereo! If you're not sure, don't do it!!!

2. You have a 2-channel signal, but a single mono woofer/subwoofer. You need to combine the left & right channels (probably the rear channels), but you cannot "short" the lett & right channels together without damaging the stereo. So, you need an amp (or crossover) that can combine the left & right signals (without mucking-up the left/right separation and without damaging your stereo). Or, you can simply connect the amp to the left or right channel. (With most recordings the bass is the same in both channels, so you can "get-away" with using only one channel.)

3. You need low-pass filter or active crossover to filter-out everything but the bass. This is a common feature in car amplifiers, or you can get a separate crossover. (An electronic crossover will also have outputs for mid & high frequency amps, but you can use if for the bass-only.)

Good luck!

* This could actually be done with a passive crossover and no additional amp, but it's not the "standard way" with car stereo setups, and it's not a straight-forward solution either.

** Line-level outputs will usually have RCA connectors (like the red & white audio connectors on the back of a home DVD player or home CD player).

Please answer fast..
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Re: woofer

Postby rob » Mon Sep 20, 2010 8:49 am

not an expert on car audio so could be wrong, but think the following is close to the truth and you wanted a fast answer.

It is possible to build a passive network and attach a sub to the signal cables going to the rear speakers - BUT - no-one does it because the cost of components don't justify the result which will be a change to the tonal quality at the expense of loudness due to the resistance of the passive components.

The rapid path to a ruptured spleen is to get a powered sub with a high level input and use the feed to the rear speakers as input - or a sub amp with a high level input (most have it) plus the 400watt sub you mention.

Go to a car audio shop if you're in a big hurry but do shop around. Whatever the claimed power ratings are, divide by ten.

If you really want to learn about crossover/speaker design, have some time and want a project to work on, do some more research on the web and read lots while you wait for more scholarly tuition from those on this forum more enlightened than I.

Best of luck,
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