ICE Question from Noobie

[Liberator]

Hi everyone,

just hoping you guys could shed some light on ICE for me...

As far as speakers are concerned, I know bigger is better, so if I wanted to fit a 12" / 15" sub in my mini, with the other speakers/tweeters, then what kinda amp do I need?

I read here in a mod magazine, that you can get the VR-4000D, which is a 4000 Watt amp into 2 ohms.

It says it makes 250-watts x 4 into 4-ohms, 500 watts x 1 into 2-ohms, 1000 watts x 1 into 1-ohm.

my question is, if I had a 15", 5000Watt Sub, then how does that amp fix in with that? or even if it was a 1200watt sub, surely the 1000watt x 1 @ 1-ohm wouldn't be enough to power that sub, let alone any other speakers/tweeters...

my other question is, whats the big deal with these ohms... what does that mean, and I know basic electronics, so its to do with resistance, and I've seen these huge resistors advertised at 1-farad, etc...... where does it all fit into the big pICturE?

Thanks,

Jon , 27 year old noob to motoring 'n' modding



edit:

oops, almost forgot this question.......

I've noticed on the face-plate things of radios/cd-players that some say things like 4x50watts.....

I don't understand if it only outputs 4 channels at 50watts, then how can the (for example) 150watt tweeters, and 1200-watt sub be adequately supplied.....


thanks again.

[snid]

It's a MINI, not a Hummer H2

I put in a JL Audio Stealthbox, which has one 10" woofer. I'm powering it with a 250watt JL Audio amp (250/1). It's pretty durned loud in there already.

Of course, people have done dual 12"s... there are probably some 15"s out there, too. But, really, thousands of watts? I wouldn't want to ride in that MINI. Unless the speakers were horrifically inefficient (take a ton of power to make a little sound), that is: inefficient speakers are also generally higher quality speakers.

As for watts and ohms... pick a speaker - it will say it is so many ohms (4 or 2, generally), it will also say it is recommended to have so many watts driving it (at that resistance). So, now you have the specs for the amp you need to drive it.

The things that say farads are capacitors - used to provide extra power (in addition to what is coming from the battery) during the spikes. Not necessary in a small system.

[Liberator]

thanks snid...

so is it generally a rule that the higher the ohm of a speaker, then the less wattage?

which figure is important to look at for sound quality as well as volume?

If I had 4 front speakers each 4 ohms, totalling 16 ohms, how would I have to configure my amp in the example above.....

would I need more than one amp?
and does it matter if I used one amp giving 250 watts at 4 ohms to each speaker or could I have 2 amps, giving 500 watts to each speaker at 2 ohms per speaker?

Jon will get ther eventually...... don't give up on me yet

[snid]

Quote: Originally Posted by Liberator

thanks snid...

so is it generally a rule that the higher the ohm of a speaker, then the less wattage?

Yup... that's the law Power (watts) = voltage^2 / resistance. The voltage part of that equation is out of your hands (of course, now someone will step in and say I'm wrong). So, increase the resistance (more ohms) and the power (watts) goes down. But, don't get hung up on that.

Quote:

which figure is important to look at for sound quality as well as volume?

None of them. There is no figure that will give you "sound quality". You'll have to use your ears. What I like might not be what you like.

And, the numbers don't even really tell you much about volume, either. You'd have to add in speaker efficiency / sensitivity to get closer, but I don't think even then you'd have all the info to look at the numbers and say "this system will be louder than that system". Some speakers take a lot of power to make a little sound, these will usually have high power handling numbers (lots of watts) because you'll need lots of watts to make it listenable. Othe speakers can make a lot of sound with a little power...

Again, looking at numbers will only confuse you. Listen to some speakers. Pick one you like and can afford. Then, worry about how to power them.

Quote:

If I had 4 front speakers each 4 ohms, totalling 16 ohms, how would I have to configure my amp in the example above.....

would I need more than one amp?
and does it matter if I used one amp giving 250 watts at 4 ohms to each speaker or could I have 2 amps, giving 500 watts to each speaker at 2 ohms per speaker?

Jon will get ther eventually...... don't give up on me yet

It's cool...

I'll gues that by "four front speakers" you mean one tweeter and one mid for both right and left, making a total of 4 drivers (speakers). The catch is that a tweeter / mid pair really count as only one "channel". The pair present one 4ohm load to an amplifier.

So, to amplify speakers front and rear, right and left - you're looking at 4 channels (even though it will probably be 6 or 8 seperate drivers). When and amp says something like 100watts x 4 at 4 ohms, it means it has four channels (front right, front left, rear right, rear left for example), each 100 watts at 4 ohms. And remember that a channel can be multiple drivers, like in a two way (tweeter / mid) speaker.

I don't completely understand subs yet, so I'll avoid that question (single voice coil vs dual voice coil)

If you want to run all four corners and a sub, you're looking at (most likely) 5 channels that need to be amplified.

My advice: Stop looking at numbers. Start listening to speakers. Find one you like. Get its specs - power handling and load (resistance). Find some amps that are close to those specs and listen to the amps driving that speaker.

I'll dig up the numbers on what's in my system and post them for an example. But, I'm getting a new head unit (CD player) next week, so things are changing.

[snid]

Alright, time for numbers

My system is:

front speakers - MB Quart DSD213 2-way components (seperate tweeter and mid). 4ohm load, handles 35-90 watts

front speaker amp - McIntosh MCC82 - 2x40watts at 4 ohms.

So, for the fronts, my amp is on the low end of the speakers range. But, it's one of the better amps you can buy, so all 40 of those watts are pretty usable.

rear speakers - MB Quart DKC169 2-way coaxial 6x9's. 4ohm load, handles 60-130 watts

The rear speakers are being driven by the head unit, not an external amplifier. The head unit puts out 15watts at 4 ohms to each channel. So, my rear speakers are really underpowered. But, that's okay (as long as I don't crank up the volume, sending a crappy, overstressed signal to the rear speakers and damaging them).

The head unit is going to be replaced by one that puts out 50 watts at 4 ohms, and a pretty clean 50 watts. So, that will help a lot.

Subwoofer (in the JL Audio stealthbox) is a JL Audio 10w3v2-d2. It is wired to present a mono (single channel) 4 ohm load, and is rated to handle 300 watts

Subwoofer amp: JL Audio 250/1. output is 250wattsx1 (it's a monoblock amp) at 1.5 ohms to 4 ohms. I don't get that... but that's what the specs say. Kinda breaks the rule of more ohms = less watts. But, oh well.

Amazingly enough, the front and rear speakers, which were the first thing I upgraded, are about to become the weak link in my system again.

[kapps]

Also remember that speakers have an rms and peak wattage. RMS is what the speaker can take continuously and that's the important number - there is actually a range of wattages. For example, I'm easily driving two speakers that can handle 75 watts rms with a headunit that puts out 19 watts rms. You don't need an amp that powers the speakers to their highest wattage values. As for subs, the MINI will probably sound fine with a good single 10". Sub amps are mono and usually feature low pass controls so only the low frequencies get to the sub. Subs should be powered to at least half their rms power to get a good sound. Say a sub that can handle 350 watts rms should have an amp of 250-300 watts.

As for single and dual voice coil, a single voice coil is just like any other speaker - read the wattage and resistance, say 350 watts at 4 ohms and that's what it can take. A dual voice coil will have two 4 ohm voice coils so it allows you to either hook up two amps at 4 ohms or a single amp with bridged channels (to 2 ohms) and get more power. Just stick with single voice coil subs to make it easier. There's no need to push out that much power in any car much less a MINI.

[Liberator]

thanks guys, I think I understand now......

I thought those big amps in the boot were needed for all 5 speakers.

small amp for front speakers, I didn't realise the head-unit powers some speakers buy itself, and also didn't realise that the front speakers have a seperate amp.

Thanks a ton guys

Am I right in thinking that you don't really want a 1000-watt amp or higher for a 1000-watt sub because you may end up blowing the sub? or does the system know what amount of wattage to send through to the speaker, thus future-proofing your amp incase you want to add a more powerful sub, or front speakers in the future?

I know Im asking niggly questions, but it would help me to know these kinds of things. Id rather buy a better amp say for my front speakers so that when I am confident enough I can upgrade my front speakers, but already have a decent amp to handle them. Or would this damage my existing speakers.

~ Jon