Any car stereo wiring whizzes here?

[ho'ard]

Al of the stereo forums I know of are too dead to expect an answer this century, so hopefully someone here has a knack for this.

I have a PA-style speaker (carpeted enclosure) w/ a 15" woofer and two
horn tweeters.

My overall plan is thus:

Run a 12 amp in tri-mode, bridged mono to this speaker, and also powering
two external self-contained 4-ohm speakers. I've tested this setup with
these speakers and it's stable.

Several questions:

-I want to switch out this woofer for a better one I have that's dual
voice coil-- is it preferable to run two sets of leads to the two coils
in parallel, or run the voice coils in series? If in series, is there
anything to know about the polarity?

-currently the leads come in to the (single coil) woofer, and then 2
sets come off of the woofer going to the tweeters. Effectively, this
speaker is already running at less than 2 ohms, no? I guess I don't see
how I could have cranked this thing so long with the amp bridged to
1-point-something ohms for this speaker, plus two more speakers at 4
ohms each. Something must be wrong with my calculations or thinking here.
The woofer and both horns are all 4 ohms.

-assuming the cabinet was ultimately 4 ohms, and I ran the amp in
tri-mode with two 4-ohm speakers plus bridged to this 4-ohm speaker, am
I then running the amp at 2 ohms, or does some other rule apply due to
tri-mode?

-I see nothing here in the way of crossovers-- can someone confirm that
horn tweeters naturally only accept the highs and it's fine to run 'em
full range? (I think I've heard this before).

To simplify (I hope) I have this cabinet with a single input, which is
going to contain one 4-ohm dual voice coil woofer and two 4-ohm horn
tweeters, and I'd like the end result to be 4-ohms. How do I wire?

Thanks for any help!!

[Dick Moore]

The tweeters are undoubtedly piezo units, which have a naturally high impedance and electrically act as their own crossover-- they just call 'em 4 Ohms to confuse everyone. These tweeters are faves for car audio for these reasons.

So when you bridge to the woofer (with tweeters -- just forget they are there) the woofer is 4 Ohms minimum, but more like 6 or 8 Ohms thru most of its operating range, and the sats are 4 Ohms each, minimum, but more like 6-8-10 Ohms over most of their range, which means that each channel of the amp is seeing a 4 Ohm sat paralleled by an effective 2 Ohm load from the woofer 'cause the woofer is drawing twice as much current as the sat speaker due to bridging, at MINIMUM impedance. Total load per channel will be roughly 1.3 Ohms MINIMUM, but more like 2-3-4 Ohms over most of the frequency range. As long as you're not head-banging, it'll run OK.....

For the dual voice coil woofer, I would run the coils in series, so the amp positive will feed one coil's positive, a jumper will connect that coil's negative to the next coil's positive, and the second coil's negative will connect to the amp's negative.

[mikebw]

Here's a lively forum you should check out- http://www.pesupport.com/cgi-bin/config.pl

It's free, no registration required, and there are many helpful people.

[ho'ard]

[quote mikebw]Here's a lively forum you should check out- http://www.pesupport.com/cgi-bin/config.pl

It's free, no registration required, and there are many helpful people.
Wow . . . half the internet is up right now caclulating ohmage . . .
Bookmarked. thanks.

[ho'ard]

Great answer, much appreciated.

At some point I decided to toss it all back together as is (pulled all the horrible wires out and redid it to my liking with appropriate wire and even some electrical tape :-)

I'll save the dvc woofer for the next project.

I managed to punch a hole in the rubber surround-- not my week (ruined an iPod a few days ago). I grabbed some bathroom sealant (only thing handy) and it looks repaired. Spent the rest of the night getting it set up on the bike trailer, mounting amp and batteries to it, etc.
I should stay home on Saturday more often-- I had a virtual parade of heroin addict prostitutes past my garage. Need to figure out how my alley became a preferred route.

Anyways, I don't see any sign that the amp is struggling, so I'm going to go with this setup for now.

I didn't think horns were typically used in cars . . .


[quote Dick Moore]The tweeters are undoubtedly piezo units, which have a naturally high impedance and electrically act as their own crossover-- they just call 'em 4 Ohms to confuse everyone. These tweeters are faves for car audio for these reasons.

So when you bridge to the woofer (with tweeters -- just forget they are there) the woofer is 4 Ohms minimum, but more like 6 or 8 Ohms thru most of its operating range, and the sats are 4 Ohms each, minimum, but more like 6-8-10 Ohms over most of their range, which means that each channel of the amp is seeing a 4 Ohm sat paralleled by an effective 2 Ohm load from the woofer 'cause the woofer is drawing twice as much current as the sat speaker due to bridging, at MINIMUM impedance. Total load per channel will be roughly 1.3 Ohms MINIMUM, but more like 2-3-4 Ohms over most of the frequency range. As long as you're not head-banging, it'll run OK.....

For the dual voice coil woofer, I would run the coils in series, so the amp positive will feed one coil's positive, a jumper will connect that coil's negative to the next coil's positive, and the second coil's negative will connect to the amp's negative.

[ho'ard]

Hope you don't mind Dick-- I couldn't resist and posted the question to the Parts Express forum just to see if it gets a response (testing the forum for future use).
You answered everything perfectly!
-h'

[Dick Moore]

Well, natch! Glad to help h'. I guess those years in the business weren't wasted after all.

[mikebw]

H', Glad to see you tried out the forum. For the money, the MacResource Forum and that PartsExpress forum are the best resources I have ever come across on this vast Internet.
Sometimes you can get a few goofy responses, but more often than not it's right on the money or nothing at all. Looks like you got some good advice there already.

You know, the funniest thing is I once remember driving down a street in DC, and there was this kid riding his bicycle on the sidewalk, and behind him he was pulling a red wagon, straight out of your childhood, loaded with some outrageous boom-box just blasting the tunes. This is the first thing that came to mind when I read your post.

I might add that many, (not all) horn tweeters do have tendancy to sound pretty bad, but like they said can get pretty loud. As you might already know, it all depends on what you are trying to do.

The best advice I can give to anyone on the PE forum is to simply state what your goals are in plain english. Too many people get caught up in the numbers when they don't necessarily understand what they mean, and that can only confuse the real issue of what it is they are trying to achieve.
It sounds like you have a good start on the concepts, but there is so much to learn if you're willing. I don't claim to be an expert by any measure, and as long as you don't either people of all levels will be there to help you. Cocky elitist types are generally not welcome, anywhere. (not saying that you or anybody else is of course, just an observation I have mode on both of these forums).

[ho'ard]

Thanks, mikeBW!

[ho'ard]

PS I hate the sound of horns but these don't sound half awful-- just the usual amount of not-goodness.
I think maybe because the woofer is running full-range, which maybe makes up for the missing warmth.
The "satellites" use these:
http://www.beachaudio.com/index.php?cPath=149_167_4327
A bit of scratchiness as you'd expect, but they put out a lot of sound and a surprising amount of bass.