stereo suggestions requested

Due to a time / money crunch, my time frame for producing a sound system has been severly shortened, although it still is relativly long time. I have about 1 to 1 1/2 months to do this, however I am re-fabricating everything (door panels, center consol, rear divider, speaker monts, etc) as an intensive  crash-and-burn, learn-as-you-go project for myself / my car. I've been researching as much as possible, and still intend to, but I do need some help on a few things to help speed me along.

I intend to put 4  12-inch subs in my hatchback, my questions are these: I'm still unclear on whether a dual 2 Ohm sub is better/louder/lower than the dual 4 ohm. also, how am I going to calculate the size of box, with little-to-no equipment, I've seen the calculations, which have told me there is a method, and that method dumbfounds me. Is a ported box designed  to be a smaller than sealed, or is the difference just in SQ, as opposed to box size? "R8.0:1 Car Amplifier 800 watt" what does the R8.0:1 mean? Also, going through the wiring system calculaters, I found the diagrams provide for the dual 4 ohm to be wired into 2 and 8 ohm loads, and the dual 2 ohm to be wired into 1 and 4 ohm loads. Am I right in assuming that the lower the ohmage is easier on the amps and provides a lower freq?

If, when answering, you could provide a bit of info/reasoning as to how you came to the answer, so that I'm getting not only the answer, but also the whys to it, that would be great!  Thanks for any and all info!

Craig McKee

I don't want to sound negative or discourage you from your goals, but with the questions you have posed, you will more than likely run in to issues that may be out of your league.

I suggest you wait and spend more time researching more, then apply your knowledge. Things done in a last minute fashion often yield undesirable results.

The bcae1.com has a plethora of knowledge and truthful help. In fact most of the answers to your questions are there.

Ok.  I'll answer what I can and leave the stuff I can't to better qualified people. 

First...  A dual 2 ohm sub and a dual 4 ohm sub are no louder than one another if they are the same make and model.  The dual 2 and dual 4 ohm refer to the voice coils.  The dual 2 ohm sub can be wired in a 4 or 1 ohm configuration.  On the other hand the dual 4 ohm sub can be wired into a 8 or 2 ohm configuration.  With this in mind, the amount of current draw from the amplifier changes.  An 8 ohm load doesn't extract as much power from an amplifier due to the higher impedance.  The higher impedance makes it harder to draw power.  The lower you go in ohms the easier the current flows.  A 4 ohm load will draw more from an amp than an 8 ohm load, but less than a 2 ohm load.  So a dual 2 ohm sub will be able to draw more power from an amp if it is configured in a 1 ohm load.  A dual 4 ohm sub can only show a 2 ohm load, so it will receive about half the power.  The sub itself isn't louder, but it is drawing more power to become louder.

Second...  To calculate the specs for a box you can just look at the company recommendations or a program that plots woofer response in different enclosures.  I can't remeber the name, but someone surely will.

Third...  Ported boxes are larger than sealed boxes.  Sealed boxes allow for better sound in a lot of cases, but a very well built sealed bow will sound just as good.  Sealed boxes also allow for more error when being built.  In a way they are more forgiving.  Ported boxes also don't handle as much power as sealed boxes, but are generally louder.

Fourth...  The R8.0:1 amplifier is referring to a Phoenix Gold model right?  That is just the name of the amp.  I think it puts out 800W RMS @ 2 ohms if I'm not mistaken.

Finally...  The lower the ohm configuration seen by an amp the harder it is on the amp.  Lower ohms draw more power which causes the amp to work harder.  Also, the lower in ohms configurations you go the more sound quality you lose.  An average listener won't notice the difference between speakers seeing a 4 or 2 ohm load, but in SQ competitions it can become very important.

Well that's all I can think of now.  Welcome to the forum and I hope I helped.  If you got anymore questions just keep asking.  And for anyone who reads this correct me if I'm wrong, but I think I was pretty accurate.

You made a very good explanation, arrow12.  I agree with what you said and, unreality, I also agree with what dwarren said.  Some of your questions are such that you will need to put this project into perspective and get through it step by step.  The first would be dwarren's suggested reading, which will take some time but be thoroughly worth the time you spend.

After, and during that time, put your system objectives in order:

• After you have gone through and completely understand those first 12 chapters culminating in the one on Ohm's Law, you have to select the components of your system.  Before purchase you have to verify how each component will affect another component in the chain.  By this time you will know what configuration of subwoofer you should buy, and what amplifier will power them.  Same with the front speakers and the amp that powers them.
• Turn toward the wiring and power aspect of this project.  Find out:  will the added power load affect the car?  How much added load can you put on your car without having to improve the factory alternator, wiring and battery?  Find this out by taking your car to your local shop and having an electical system test done on it.  Or, as we do in most cases, upgrade it afterwards if needed, but don't say you weren't warned...
• The preparation of the car itself can come after those critical steps are done and the buying is done.  Don't sweat that stuff yet...start with the BCAE1 site and put everything into perspective.  The prep should be the fun part of it all.

Use this forum to your advantage.  One advantage has already been given to you with the first answer you got from dwarren.  There are plenty of other qualified sites with good info as well, but that one is referred often because it is done so well.  I learned from it myself because someone on this forum linked to it.

You will have more questions, so freely post them here.  The subjects should be singular in nature, though, to avoid a confusion of responses.  When you have successfully completed this and are basking in admiration of your sound system, we welcome your input here.  We also have a gallery section set up for pics, so you can post pics that could help someone else out.

Hey, big thanks to everyone so far, and to dwarren for providing the link. The advice given is great, and I will take the time to go through everything. This first build is to do just that, learn. Then, a second build will follow, and that, in turn, will be followed by the 8 week course at Mobile Dynamics. I have allready made my first speaker enclouser, meant to house 2 6x9's on the rear panel in my hatch back. It sucked, so I destroyed it with a crowbar. It was strong, but ugly. But I learnt a lot of things I hadn't read on any forum, book or site, which is why I'm doing these builds of the car and audio system. Reccommended reading is always appreciated, tho, as the build/destroy method takes a lot of funds.

I just want to confirm on arrow12's last bit, a higher ohm-age is easier on the amp *and* gives better sq?

Thanks for all the info so far!

Craig McKee

yes arrow12 is right! the higher ohm your sub/speakers are the cooler and less distortion. but it's a trade off too. lower the ohm = more power. higher the ohm= less power but cooler running and better sq.   lets say an amp is tated at 100 watts rms and .05 distortion at 4 ohm's at 2 ohms in theory that amp will put out 200 watts rms and higher distortion. with the same amp at 8 ohms that 100 watt amp is only going to put out about 50 watts rms but lower distortion than the 4 ohm rating.  the more you drop the resistance (ohm) the more power it will produce and the more current it will need to produce that power. resulting in heat. cause your amp is working harder to keep up with the demand.

i hope i explained that okay?

every amp (same as subs,speakers h/u's, eq's and so on) has its own model # which tells you (if you read it right) about it R=octane series, 8=800 watts 0=part of the power rating 1= one channel/mono. like a mtx 4301  4=4000 series 3=300 watts 0=even number (part of the powerating) 1=mono