I am trying to understand it all.....subs and amps.

[e30pwr]

Alright. I'm trying to figure out my sub/amp combo. I know i want some good power when i REALLY want to bump loud. I've narrowed down my selection but my real questions are understanding the numbers. I'm in AP Physics and we just did circuits and whatnot so I've got the gist of it all. But take for example my amp. Yeah it may not be the best but whatever.

1. I'm looking at the Lanzar MXA242. It says its got 400Wx2chan with 4Ohms of resistance. So If I understand these numbers right it will push out 400W on both channels with 4ohms of resistance for each channel?

2. With that being said if I bridge that amp would I want to run the subs(Autobahn AW1000V) in parallel or a series? And Could I do that?

I'm planning on running the Blaupunkt London with 4 gauge back to the amp and have a custom box with a single port. Please don't just tell me "it wont work...." I want to know why and how it works out like that. And thanks for any help!

[wagonizzle]

Okay, I'm sure Luke will chime in here and listen to him. My two cents:

The stuff you posted is relatively cheap stuff. You get what you pay for. There are no effective governing bodies regarding power rankings. A simple way to gauge how much power an amp will produce is to look at the sum total of the ATC fuses on the side of the amp. An amp claiming 1200W with one 25a fuse is a lying bastard (not referring to your proposed amps). Spend a little money for some good clean power and not on fancy radios or speakers. Also, get used electronics but not speakers if you want to save money. A speaker is a 100% mechanical device that wears over time and can be damaged without you knowing it. It can be hard to spot a damaged speaker for the inexperienced.

As far as your sub region goes, just make sure you are running an amp at it's intended impedance range. Some are designed to make max power at 4 ohms mono (bridged), some 2 ohms, some 1 ohm. No matter what, when you cut impedance in half to make more power, you cut the damping (the amp's ability to control the speaker) in half. Like adding more horsepower to your car and getting worse brakes. Some amps have the circuitry to deal with low impedance control issues, some do not.

Also, I would avoid a ported box. Vented enclosures definitely require an amp with good control, and unless the box is properly designed SPECIFICALLY FOR YOUR WOOFER (and car) you will not see maximum benefits and could easily lose output and almost always tightness. You will get the same output with two woofers sealed as you would with one woofer ported properly. You will give up a little more room for the enclosure, but not much, as vented designs usually require more air than sealed anyway. You are also less likely to fry a speaker. I'm sure you're learning this in class, but if you want a final impedance of 4 ohms mono, you will need two 8 (or 2) ohm drivers. For 2 ohms mono, two 4 (or 1) ohm drivers, etc.

Cliff notes: Good amp, sealed box, proper impedance.

Hope I was helpful and it all works out for you man.

[e30pwr]

So if I just forget the bridging to keep the control over the sub by the amp and forget the port I should be fine?

I just did the math and if I run the same setup and run them in a parallel circuit I will get a total impedance of 2 ohms. And the amp says 650 watts RMS for a load of 2 ohms x2 channels. but I wont have to use both channels will I? I know the power rating form the man. is probably off a good bit but lets just assume its right.

And about the fuses. I looked at the side view and its only got one fuse. A single 30A x 1 as the site says....good or bad?

[e30pwr]

After my shower I did some more figuring and heres what I got to make sure that the power rating isn't BS and that the single 30A fuse can handle the advertised 600w RMS power. Please excuse the double post.

Try and follow this:

lets assume that the 600W RMS is the right number, and isn't a blown up figure. I then know that the total resistance form the pair of subs ran as a parallel circuit gives me 2 amps. And that each sub is 4 ohms. For now we will figure one sub's current. I then use the two equations: P=VI and V=IR. I get 600=VI and V=4R. I substitute and get 12.247amps for one sub. Then using the rule that the total current is equal to the sum of all the currents from the individual parts that means that my total current is 24.495 amps. Then assuming that this website is correct in their figures that 30 amp fuse should be able to handle all RMS power given out by the two subs. Correct?

[StereoInstaller1]

OK, first off, stuff you need to understand: Bridging 2 channels of an amp DOUBLES the load, so if you have a 2 ohm load, that will show each channel 1 ohm...does that makes sense to you? So, that woofer is a piss poor choice fro that amp if you plan on running 1 of them...that woofer is 4 ohm/coil, DVC. So, basically, that woofer is either a 2 ohm woofer or an 8 ohm woofer, no other possibilities...unnerstand?

That amp is capable of a 2 ohm per channel load. That is where it will make its best power, so that is where you want to keep the load. If you try 1 ohm per channel, you WILL let the smoke out, sooner or later (no, I do not fucking care what "your buddies amp" did, sooner or later it will fail) So, since you want to understand the math part, groove on this: that amp is a shitty choice for one of those woofers, but just fine for 2. You can go either way, but you could wire 2 of those woofers to be 8 ohms each OR 2 ohms each and still come up with a 4 ohm load...or just wire it in 2 ohm stereo, IT MAKES THE EXACT SAME POWER!


So just exactly WHY would you think a $100 amp is accurate about ANYTHING on its spec sheet?

Generally, you can figure how much power and amp actually makes by its fuse. Baically, add a zero to the fuse rating...we can get all scientific about it and bust out Ohms law, do an actual impedance test and current draw test and do some math...but 99.9% of the time, adding a zero to the fuse value is pretty damn close, especially since wattage is meaningless.

So, this little POS Lanzar (damn, 15 years ago, they would NEVER sell a pile of shit like this) makes about 300 watts, RMS, on a damn good day.

Now, pay attention for just a moment: WATTAGE MEANS NOTHING! If you are looking for loud, you should sell your E30 and buy a hatchback. Keep in mind that is is damn near impossible to measure the difference between 300 watts and 500 watts...why the fuck do you think you would be able to hear it?

If you really care to learn more about the actual physics and science, not just some advertisers bullshit, go find and read a few of my lengthier post on the subject.

I will say this: the only chance you have of EVER getting LOUD in an E30 is ported, or 9 million watts and a 300 pound subwoofer...and my 600 watts RMS and single 12 will still shred your in clarity AND SPL. Getting loud is all about the box design...the box I build will play louder IN THE FUCKING CAR with 1 watt than the average box will with 100. Think about that...if there can't hear a difference between 300 watts and 500 watts (trust me, it is true) how much power does it take to hear a difference? Power is a logarithmic thing, so to get louder than 100 watts takes 1,000...we aren't talking about "Swap Meet" watts either, but actual real power.

So, if power is not what makes it loud, what is? Hint: box design.


Jacked up on coffee, need to go build some boxes. Building a under-bed subwoofer for one of my good customers today...kind of odd, but what the fuck, I am all jacked up on coffee. I like it!

Luke

[e30pwr]

Thank you for your insight. I knew none of the figures were really going to be accurate. I'm really just looking for some subs that I can hear clearly in the cabin and maybe port it through the rear deck. Kind of like the way you built your boxes. Although I couldn't do the ski pass regretfully.

And about the wiring. I know if I run them in parallel it would come out to a 2 ohm load. so then i just run those wires into one channel for the 650watts at the 2 ohm load? I'm assuming my way of saying it was the "it in 2 ohm stereo".

Power is really only a rating of the watts. the sound coming out of the speakers are based alot more upon the box they are in and how the amp can control them.

[smonkbmw]

i think hes trying to say to look at better product first before you continue your wiring quest.

[StereoInstaller1]

Well not even better product, just different product.

Either use a 1 channel amp intended for a 2 ohm load, or use a DVC 2ohm/coil woofer, or a SVC 4 ohm woofer. That particular mix just won't work.

[e30pwr]

So if I just go with the same pair of 10's and wire them parallel and use this Crunch PZi 1000.1 for the 2 ohm load it should be fine right?

[StereoInstaller1]

No, then you would have either a 1 ohm load (too low for that amp) or a 4 ohm load, which would make half its power.

1 DVC woofer would be correct for that amp, or a pair of SVC, or 4 DVC.

Dude, you are really trying to complicate this.You are gonna hurt yourself, relax!

Luke

[Turf1600]

So if I just go with the same pair of 10's and wire them parallel and use this Crunch PZi 1000.1 for the 2 ohm load it should be fine right?

Luke will set you up with a nice matching setup man. You realize he's a car audio dealer right? He's such a good salesman he's not trying to sell you stuff.

[e30pwr]

I know hes a dealer. I was just hoping I would be able to understand all this stuff as well as being able to get it. If its possible Luke could you just match up a pair of 10's and a amp that can push like 400-500W RMS? And around like $400?

[StereoInstaller1]

If you want the best combination of boom and clear, I recommend a single 12. Best mix of size, fit and cost, IMO. My box is $150, a decent amp that makes an honest 500 watts is $175, a woofer capable of handling most of that is $100, shipping and such would likely be about $70, maybe less.

A pair of 10's just does not work in an E30, due to the fact that it is hard to get bass into the car. You could of course build a box with the 2 10's firing into the ski hole, but that would be a raging pain in the butt.

You could of course fire the woofers into the trunk, but then you are back to the whole "hard to get bass in the car" thing.

[e30pwr]

Yeah. I have the eta so no ski pass, or so I think. I was thinking maybe a port that goes through the rear deck like the box you showed how to install in a previous thread. No offense I'd jsut rather buy the amp and sub(s) myself and make my own box. Will it be top of the line professional? Hell no. Will it work for getting some bass into my cabin and for a 17yr old? More than likely. I'm not looking for enough bass to flex my trunk or anything.

[Eric]

I will say this: the only chance you have of EVER getting LOUD in an E30 is ported, or 9 million watts and a 300 pound subwoofer...
Luke

luke, back in high school I worked at best buy when they first got rockford fosgate (before rockford took that huge dump that they just seam to be recovering from)

anyways with some high school ingenuity i crammed 3 JL W6 12's between the shock towers with a 800a2 running to each sub!

you could visibly see the windshield vibrate, i think that is plenty loud! haha!


but i will agree with everything you posted that i cut out, a proper box w/ a little power will go alot farther than a shitty box with a shitty amp