Large audio install

[Strut]

Okay i was on bimmerforums asking about this but I was referd to this site. I have a 1987 325i vert, and I want to put two kicker L7s running 1500 watts rms total and 4 alpine type r components that will be running probably 80rms each. I feel my alternator will not even be close to providing power to a system requiring so much constant wattage, so I want to know the best way to upgrade my alternator and replace it with a higher output alternator. I have measured all the specs and my subs in their current box with into the trunk although they take up all the space fit fine. and there is enough room to install both my amps. And my type-rs fit into the stock bmw speaker holes. So I am really just wondering what type of alternator I need to get this system to run properly and not fry the alternator. I was told that the memeber stereointaller was the best person to ask. Because I need a different alternator for sure, but I jsut need to know which one because I want to install this stuff as soon as possible.

[Dominic49]

most people install a 2nd (or more) battery in the audio world when they put in a large system

[dwvw]

A second battery is only good for extending engine off listening time. Once the vehicle is started it's just another load on the alternator. I ran 3500 watts RMS off the stock alternator in my 03 VW GTI, but I rarely cranked it up. I would contact Mechman High output alternators as I have heard of issues with other suppliers of HO alternators and only good things about Mechman.

[russhixmo]

If you wanna be on the safe side just get a cap that would be appropriate for your stero. I had two type x's and had a 1000 wat cap in my old five series and the lights didn't even dim after I put it in. As far as alternator company's go, I can't think of any off the top of my head.

[bmwman91]

You will probably be fine 99% of the time. While the amps may be rated to output 1500W, chances are that you will only be pushing a fraction of that most of the time. Honest to god, if you somehow manage to run 1500W into your sound system, you will come out of it with serious hearing damage. I assume that you are running the component speakers off of one amp and the two subs from the other amp?

The current Type-R component sets are rated as 87dB with 1W input. So if you have a 4x50W amp driving them, they each make 104dB (sound pressure). With all four running, you get 110dB, not including the subs. That alone is pushing the threshold of pain. As for the sub...well, you don't need 1500W to go deaf.

So, my advice is to not worry about it. To get each to ~100dB, you only need to run ~16W per component set, and assuming that the subs are less efficient at maybe 80dB/1W, each would need 64W, for a total sound pressure level of ~107dB. That is running 192W to the speakers, total. Assuming amplifier efficiency of 40%, that makes the total system draw 480W, which at 12V is 40A (or ~35A at 13.8V). This is assuming you have the music running at 107dB nominally with higher peaks...that is freaking loud and you probably aren't going to do that (maybe continuous level of 95dB with peaks around 105dB).

Anyway, the point is that you should just try it out before worrying about the alternator or battery. The amp is rated to put out 1500W, bit you will be using less than 10% of this most of the time, if not all of the time. Sorry if I got a little too technical.

[Strut]

The thing is i rarely if ever turn down the music so it plays at max compacity all the time, I should be deaf but low end frequencies dont damage your ear drums as much as extremely loud highs do. I already have a 2 farrad cap in the system, but from the looks of my cars electrical system i think i need a new alternator regardless of the new system or not. MY window roll up slower than anything I have ever seen, they draw too much power from my alternator on their own

[e30moneypit]

so just my two cents since I had this same mentality about 12 years ago and coincidently had an e30 cabrio as well.......

you are overthinking what you need and honestly will not benefit from what you are planning on using.... more/bigger is not better.

you havnt addressed th biggest issue......... the DUAL walls in the cabrio...... no matter how well you "port" the walls on your own you will be getting very muddy distorted and rattle everything to hell "thump". You NEED a cabin firing sub in THIS more than any other e30 since you are losing lots to the trunk and lack of a "cabin" remember its a cabrio--no solid roof.

As others said yeah you have ummm ambitous output goals that need recalibration. In my current e30 Im running some powerbass components 3xl-5c that nail the mids/highs so much better than the type Rs I have in my zed.......... at half the cost.

The sub is set with a 10" W6 being fed 900rms in a cabin firing luke box and that thing slams hard ..........with NO rattles. :drink:

your window motors sound like they are going out btw or you need to grease the tracks

[Strut]

My system never sound distorted before but tuning the box at 29hz gives it the ability to push lots of air, but still have nice clean sound, no distortion or woofer clap, and I am definitely going to drill a large hole bewtween the two back seats and so i Have like a 6in by 12in gap cut into my upholster and then seal it of to make it look professional, and even if I dont do that my bass is loud enough to here over a block away, my last decibel check says i was running 138dbs so I am pretty certain that bass will sound fine in my car. I jsut need to get a new alternator

[dwvw]

BTW I will be running 2400 watts RMS to my subs and 75x4 to my mids and tweets in my car with no upgraded alternator. Of course I don't blast dubstep full bore the entire time I am in the car either.

[StereoInstaller1]

The early M20 E34 cars had a much bigger alternator. You will need to use all the brackets fro that same car, but it will fit. You can use the air cooling on it as well, but it will require some work to get it to fit perfectly.

If I were running that kind of power, I would do 2 batteries and a big alternator, just to try and keep my electrical system stable. I would also upgrade my charge wire from the alternator to the batteries.

[Strut]

Quick question too, my sub box with both 12s in it weighs 100lbs, and my amps combined weih around 30lbs, is this going to dramatically affect my cars handling? Because I want ridiculous bass, but I alos dont wnat to destroy this cars perfect handling

[StereoInstaller1]

Oh yes...my last stereo was about 120Lbs all together...worse mileage, way less handling, definitely slower.

[Strut]

My amp is rated at 2200 rms and i am running them at 1400. i easily push 120dbs everyday some times i do near the low 140s. I listen to bass and my system has enough for 3 cars. I looked into the HO alternator website mechman or whatever and they have a universal alternator that has 200amperes, think that is enough? and I all ready have a 2 farrad cap

[e30slidewayz]

I'm not an audio guru or anything... but I have an Arc audio 10" woofer in a small box with an appropriate amp and it knocks like there's no tomorrow. It's actually quite fascinating that this much bass comes from a 10" woofer. I have people ask me all the time "What the hell do you have in the trunk?!". I tell um its just a 10". Dunno how many dbs it pushes... but if I had anymore bass my passengers would probably shit themselves. Dunno why you'd put 100's of lbs of audio in ur car when a little setup would be more than you'd need. However, I could use another amp for my component speakers to get the mids sounding nicer. Being that my e30 isn't a convertible, I may have an advantage with not being doubled walled or whatever, but my setup isn't ported to the cabin in any way either.

[deansbimmer]

The early M20 E34 cars had a much bigger alternator. You will need to use all the brackets fro that same car, but it will fit. You can use the air cooling on it as well, but it will require some work to get it to fit perfectly..

Well...Damn nice tip....That was some tasty info right there, Luke. I can skip dinner now! :p