Mike Frye

Happy New Year Everyone!

Anybody out there a real techno-geek?

I could use some help hooking up my new stereo if you don't mind.

Here's my *intended* setup:

Sony head unit (CDX-GT510) 52Watts X4 max power (I know, but it fit the budget )
Pioneer 4.5" (10 cm?) 2-way speakers for the doors (closing up the tweeter hole)
Pioneer 6 1/2" (16cm) 2-way speakers for under the B-pillars (flush mount in the old housing, eliminating the old rear 3"? tweeters as well).
Pioneer 10" Subwoofer in deck right behind the driver's seat (rear seat delete in progress)

I have a Sony amp (XM-1252GTR) that I'd like to use to power the rear speakers and the sub.

Here's my question: How do I wire the sub and rear speakers so that I don't blow anything up?

Here's a diagram that I think will help some of you. (It didn't help me).

I've got the rest of the specs available here if they will help. It looks like I need 2 capacitors and a coil to be wired in series. I just don't know what to get.

All speakers are 4 ohm. The sub said something about 20-4-500 Hz. I don't know what this means either .

Thanks in advance for any assistance on this.

PS- Please no comments on the relatively cheap setup. I just blew my interior budget ordering a carpet set and leather seat covers from Rob Budd.

Courtshark

Yes, you need two inline capacitors installed on the respective positive supply wires. The capacitor you choose depends on what frequency you don't want coming out of the smaller full range speakers. So, if you want to cut them off at 80 Hz (bass frequencies go down to a low of 20 Hz, at least that a speaker can produce; cutting them off at 80Hz means the full range speakers will put out everything they can above 80Hz, typically upto about 20k Hz), you want a 500 uF capacitor on each of the positive lines. The woofer supply is spliced into the positive output of the left speaker before the capacitor and the negative output of the right speaker; the coil you want, presumably to fill in what you've cut off with the 500uF capacitors (i.e. any bass frequency below 80Hz), would be the 8.2mH coil.

You could also try this product:
http://www.crutchfield.com/S-7fW69Hb...spx?i=127TM100

Crutchfield is out of it, but Best Buy and Circuit City carry these in their roadshops.

OR, you could sell this 2 ch amp, and spend a little cabage to get a decent 4/3/2 capable amp, or buy another one of that same amp (which is 2 ohm stable, meaning it can handle a "heavy load" of power draw). It is not, however, daisy-chain-able, which means your headunit will need to have more than 2 preamp outputs. Even a Best Buy Jensen/Dual/Blah Junk is going to sound better than whatever you end up with here because capacitors and coils affect sound quality. You're going to spend a lot of your time, and maybe $10 - 20 at Radio Shack, messing with this wiring wackiness for minimal satisfaction. Also, wiring speakers in series puts a huge strain on an amp, shortening its lifespan. Whatever you do, use a large power wire and ground wire, at least 8 gauge for both, and an inline fuse (yes, in addition to the built in fuse(s) on the amp).

RngTrtl

I second courtsharks opinion. save some more money and get a 4/3/2 capable amp, you will thank your self later I promise. Also, the option that you describe above is really very subpar for wiring up a stereo and amp. Its akin to doing a TB/WP job and using the absolutest cheapest materials that are possible to find, and then throwing it together as haphazerdly as possible. I know that money is tight on this project, but skimping on the final details will drastically hurt the effect of the car.
THis link explains what the caps and inds are attempting to do, and also what a good amp with a built in cross-over will do. http://en.wikipedia.org/wiki/Audio_crossover

For the technical part of the capacitors and inductors to use, use the frequency version of ohms law... Z = 1/(jwc), and Z = L/(jw)
Z = desired impedance (in our case low value for pass through, hi for cut off)
j = sqrt of -1
c = capacatence
L = inductance
w = frequency that you are trying to pass or cut
Solve each equation for C and L respectively.

Like I said earlier though, as a elec eng I do not advize this route. It will sound like poo.

Mike Frye

Thanks for the input guys.

I really don't know about this stuff, but I'll obviously take your word for it. I can easily return the amp and get a different one. I didn't know which one to get.

I guess it's back to the drawing board...

RngTrtl

The amp that you are wanting to get (and still be on a budget) should be something like this one.
http://www.crutchfield.com/App/Produ...GM4300F&tp=115
Use the front two channels to run the back pair of speakers and bridge the other two channels to runs the sub. Then you can adjust the cross over frequencies for the main speakers and the sub independantly until the sweetspot is found in the car.
Hope I helped a little.

Alan

Agreed - you ideally need a 3 channel amp with crossovers (usually this is a 4 channel amp with chanel pairs bridgeable).

The active crossover needs to at least allow you a low pass filter for the subwoofer channel pairs and a low cut (or variable frequency high pass) for the normal pair.

Alan

Shark Attack

I have watched you post and you do not seem like the kinda guy that wants to go nuts with multi channel amps. Are you looking to blow your ears out? if not.... Jusy go to radioshack and pick up a crossover. You can pull bass off of just one side (bass is ususlly not in stereo). However you could also get a dual voice coil sub and power it off both sides. This is 1 sub that has a left and a right input.. let me see if I can go find you some links, Stand by

Shark Attack

here is a duel VC sub. if you can find a better pix you will see it has 2 inputs
http://www99.epinions.com/pr-Mobile_...splay_~reviews

here is an explanation of a crossover. I am talking a passive, Passive goes between the amp and the speakers, and active goes between the preamp and the amp.
http://en.wikipedia.org/wiki/Audio_crossover

here is one
http://www.usdaudio.com/usd/pc.html

Mike Frye

RngTrtl,

You have helped and I appreciate it. I don't want it to sound like poo.

Alan, even your explanation is WAY over my head. I'll re-read it a few times and see if I can make sense of it.

SA,

You're right, I'm not looking to blow the roof off the car. The amps I saw for sale are mostly tuner type that you want to 'show off'. I just wanted to make sure the sub is going to have enough power to run and I was thinking that the rears might need a little more juice. Maybe I should have posted with my real intentions here and just asked how to go about doing that.

Here's the goal: I want my music to be as clear as possible on my budget. I like the idea of a subwoofer in there because when I started using one in my home it rounded out the sound perfectly. I don't want to shake the car next to me, I just want to have enough juice to have the full range of sound without any distortion. If I can do that on my budget (as you can see, it's about $400-$500 for everything) then great. If not, I'll just make do with what I can.

I'll be re-reading everything that's been posted and checking out the links now.

Thanks for all the responses, I really appreciate it.

Shark Attack

if you have that sub in phase, even running it off one channel will be pleanty. the sound bounces right off the back glass and to the front of the car. I have a little 6" bazooka tube and it sounds like a freaking 15" back there

RngTrtl

SA does bring up another option, but then you are back to the redneck engineering and over all cheap factor appearance and sound. A four channel amp can be had for about the same price that you paid for the 2 channel amp. Using the four channel amp will make for a cleaner looking and more professional install appearance than using the passive crossover that SA spoke about, not the mention that the sound will be much cleaner and of higher quality.

RyanPerrella

as for Amps,

if there is a Frys electronics close by to you, go there, they sell a Sony "XM4-S" 4 channel amp on close out for $100. At least they do at the store here in austin. But those are pretty powerful and absolutely tiny!

Mike Frye

I just got back from the store. Paid exactly the same price for a Jensen 4/3/2 as I paid for the Sony amp I was going to install. I know it's probably even lower quality (if that's possible) but I want to get the best sound quality I can for the money, I think this will do it.

It's a Jensen Powerplus 840, and there is a very clear diagram with the setup.

Thanks everyone, I think I'm on the right track now.

Shark Attack

anytime you have a non factory, visable sub in the back, you might be a redneck.

Mike Frye

Aha!

There's where I got you! The amp is hidden and the sub is very low-key. I'll take some pics, but I think the look of my rear seat delete and amp/sub/enclosure will be very stylish and if not 'factory' at least it will look professional.

Thanks again for your input everyone.

and BTW- I agree, a visible amp in the back is either redneck, ricer, or if it's done REALLY well, asking for someone to lift it for you.