OK.. I want to upgrade the factory speakers in my car and I'm sort of confused about something. I was looking at a local sound dealer at some speakers and the rep showed me a nice set of speakers that was tempting.

I asked him what RMS power the speakers required and he said 50W. Well I explained to him that the amp I had only did 30W RMS on each cahnnel and he said that it wasn't a problem, I could run the amp at 14.4V. Well here's the amp I have:

Alpine V12 F357
**RMS Continuous Power (Watt) at 12.0V 4ohm; Stereo (0.08% THD) 30Wx4+(0.3% THD) 100x1 2ohm;
Stereo (0.3% THD) 40x4 Bridged 4ohm; (0.3% THD) 80x2+(0.3% THD) 100x1

**14.4V RMS Continuous Power 4ohm; Stereo (0.08% THD) 50Wx4+150x1 2ohm;
Stereo (0.3% THD) 60x4 Bridged 4 - (0.3% THD) 120x2+150x1

He is right, if I ran it at 14.4V then I would get 50W on each channel. BTW, I'm running it in 5 channel mode and I want to upgrade the 4 factory speakers (1 on each of the other four channels) since i have a sub on Ch. 5.

Now my question is, can I run it in 14.4V mode and how can I do this?

can I run it in 14.4V mode and how can I do this?

I'd think that would be in the manual for the amp if it were really an option (as your specs seem to suggest).

Question about the speakers...

Do they require 50w RMS power, or is it just that they can handle 50w RMS power? Usually, I've only seen the latter in specifications. I've never heard of a regular speaker that required a minimum amp power. Unless you're talking about something special like a subwoofer driver.

If it's the latter, then 30w RMS will drive those speakers just fine. A 50w RMS amp will drive them louder and cleaner, but 30w will work too.

I looked at the website for the speakers (to confirm the rating) and it says RMS power 50-120W. It would probably work though like you said, but I think I wouldn't get the best sound at 30W.

Unfortunately I don't have the manual to the amp anymore. I have no idea where it went, but there is no switch on the amp itself to set power input or anything like that.

From what it sounds like, I don't know why anyone would want to run it at 12V when you can get more power to your speakers at 14.4V.

Now my question is, can I run it in 14.4V mode and how can I do this?

I don't believe the voltage is an optional feature. The manufacturer is just being kind enough to report to you what the specs are for each of two different (common) voltages. Most car batteries are actually 14.4 volts, regardless of what the specs on your car's electrical system might say. But there are cars (economy usually) whose batteries do not run at that voltage, and instead run closer to 12 volts. This is how it was explained to me by mechanics and car stereo professionals in my area.

As for the speakers, some stores/companies still don't bother to report the RMS handling of their speakers. But many do. What they neglect to report is the RMS range of a speaker. You can see an example of the RMS range of a speaker on Crutchfield's site, as they report this spec for nearly all of the speakers they sell. If your amplifier's RMS output is within the RMS range of the speakers, then you can safely drive that speaker with your amp. A speaker with a max RMS of 50 watts should be just fine for that amplifier, regardless of whether it is running in 12- or 14.4 volt mode. If however, the speaker's minimum RMS is 50 watts, you may want to look for a new amplifier or choose a different speaker.

Well that's where I'm running into an issue. Do i get the speaker thats rated 50-120W RMS and assume I have 14.4V running that can push 50W to the speaker? Or do I get a lesser rated speaker? I really would like something that will use the full potential of the amp.

Here's the link to one of the speakers I was looking at:

http://www.mbquart.com/2003/en_US/products/prod_detail.asp?cat=auto&strt=1&model=DSD+216&series=DISCUS+Series

You can see its rated at 50-120W (which is RMS).

So assuming I can only push 30W per channel, would these speakers sound alright.. and I don't mean would they work, I mean would 30W be sufficient to drive these decently.

BTW, peak power on the amp is 90Wx4 if that helps.

I have been under the impression that speakers need for their amps to supply at least their minimum power requirements. If they don't, then they can get severely clipped waves and end up blowing the speakers. This impression also led me to believe that you can never have an amp too powerful for speakers. If the speakers don't require that much power, they won't draw that much. If I'm totally off base, someone tell me, but this is the information I think I gleaned from past postings on the subject.

But if your speakers and amps are both of higher power ratings, then, all other things being equal (which isn't really going to happen IRL), you'll get better fidelity.

The way I've been thinking about this is that you can plug a 40W light bulb into an outlet, but you can plug a 1400W space heater into the same outlet. In both cases, the outlet doesn't determine the power, but, rather, the thing we'd intuitively think of as being passive. But it makes sense. The value of the resistor is what's changing, not the voltage from the outlet. In the case of speakers, the voltage changes, too, which is what makes the sound vary, but, if it was playing a static sine wave, the voltage wouldn't vary. Then it devolves into a more simple scenario; you can just think of it as an outlet (the amp) and a light bulb (the speaker). In that case, the wattage becomes another way of thinking of the current capacity of the circuit. In your house, that would be the fuse (and wiring). In the case of the amp, it's telling you that you can't accurately reproduce signals with that much current. If it tries, it'll fail and produce square waves.

Again, though, I could be way off base.

So assuming I can only push 30W per channel, would these speakers sound alright.. and I don't mean would they work, I mean would 30W be sufficient to drive these decently.

Your ears may not be able to detect it, but if the amplifier is only capable of 30W RMS, and the speaker's minimum RMS is 50W, then there will be distortion. You need to be sure of the voltage that is being supplied to the amplifier. You can put a meter on your battery to find out what its actual output voltage is.

But in my amateur opinion, even if that amplifier was receiving 14.4 volts, and its output was at the higher specs, I still wouldn't use those speakers with that amp. I'd want the amplifier's RMS rating to be somewhere inside the RMS range of my speakers, not right on the edge. For example, my current 6.5" speakers have an RMS range of 2-50W, and my current CD receiver's RMS ability is 22W. If I decide one day to finally get an external amplifier that was more powerful, I would get new speakers as well, so that my amp's rating fell somewhere near the middle of my speaker's RMS range.

Edit:
BTW, peak power on the amp is 90Wx4 if that helps.

I wouldn't use that rating as a reference point when selecting your speakers. At peak power, you would very likely have distortion (clipping).

I have been under the impression that speakers need for their amps to supply at least their minimum power requirements. If they don't, then they can get severely clipped waves and end up blowing the speakers.

From research and speaking to car stereo experts around here, I would partially agree. If you don't supply at least the minimum power requirements, then the speaker is not faithfully reproducing the sound (distortion or clipping). But, I just don't see how you could blow a speaker by supplying it with too little power.

Of course, I could way off base as well.

In general, it won't hurt your speakers to run with too little power. By that logic, it'd be bad to play your speakers too quietly no matter what amp you have hooked up to them. The logic behind minimum power rating is probably that the speakers are not that efficient, and you will need to turn the amp up fairly high to get to an acceptable volume level. With a low power amp, the likelyhood that this "acceptable" level is actualy distorting the amps output is fairly high. You're probably better off looking for more efficient speakers designed for the power you're going to be putting into them.

Matthew

Most car batteries are actually 14.4 volts, regardless of what the specs on your car's electrical system might say. But there are cars (economy usually) whose batteries do not run at that voltage, and instead run closer to 12 volts. This is how it was explained to me by mechanics and car stereo professionals in my area.


A nominal 12V battery (6 serial connected lead-acid cells) has a "idle" (at rest, no current drawn or pushed into the battery) voltage of ~12.6V.

To fully charge the battery you need (depending on temperature) between 13.8 and 14.4V delivered from the alternator.

So a 12V rating is typically applicable when playing with the engine off, or possibly at low idle where some alternators don't produce full effect, while the 14 or 14.4V rating is applicable for when running the car. Some amp manufacturers list power at 13.8V as that is a fairly realistic target voltage at an amp in the rear of teh car considering losses in the wiring.

To get full voltage to the amp you need proper gauge wiring. It also helps some to upgrade the "big 3" wires under the hood: battery- to ground, chassis ground to engine ground and battery+ to alternator+.

/Michael

Thanks, Michael. I knew if I mentioned it, someone who knew what they were talking about would jump in with a better explanation.

So I guess I should find some speakers where 30W falls roughtly in the middle of the RMS range.

Any of you guys have some recommendations? I'm assuming the ones I've been looking at were just a tad too high.

I think what the salesman told you is right, and that the amp you quoted will drive those speakers you quoted just fine. No need to look for anything else.

I don't. It might work well enough, but I don't think that it will work totally properly. I don't think there's enough power there to really blow the speakers, but I wouldn't be surprised if you couldn't get it loud enough without clipping. Then again, I could be wrong, and you could always replace the speakers later.

Hmmmm.. decisions decisions....

You won't hurt the speakers, but you won't get out of them everything that you could. If a speaker is rated that high (keep in mind that each company makes those ratings in different ways), then it is probably designed for a high wattage system. The speaker will probably be built differently, with heavier components and stiffer surrounds, and have greater excursion as well. Basically designed for someone who wants to play it loud. What happens with your lower wattage amp? Nothing bad. You won't send it a distorted signal just by the wattage mismatch, that only happens if you overdirve and/or clip the signal before that point (such as having the volume maxed with the gains all the way up). You might possibly distort the sound from the speaker because there's not enough power to properly control the movement of the speaker, but I doubt you could measure it, if it even happened at all. Consider that a bigger amp that's capable of higher power will sometimes play music at a lower volume, and it's not like suddenly everything sounds horrible below a magic 50W threshold?

Also, it's been covered, but think of 12V as being the power supplied just from the battery (that is car turned off) and 14.4 is what is supplied from the alternator (car turned on). Various things can affect what the amp receives such as wire size, length, having your wipers or headlights turned on, etc. but it's not worth being concerned about. There's not a switch you can just hit to change from 12 to 14.4 or anything.

What exactly are the speakers you're looking at? There must be some others of similar quality, price, that sound good, and imply that they "need" less power.

OK, let me try to confuse things more. Max, and especially Min power doesn't make much sense for speakers.

Let's start with the "Min" power. There of course is no real "minimum" power for a speaker - you can actually play as quietly as you want without breaking the speaker and without it sounding bad. But there is a more important factor - efficiency. Some speakers require less power to produce a certain sound level, others more. And if you try to push an amp beyond it's rated *sine* power, it will distort. Distorsion not only sounds bad, but produces high frequency components that might blow your speakers.

So the amount of power you need from your amp depends on two things - how lound you want to go, and the speaker efficiency (measured in dB/watt - so X dB of sound per 1 watt of input). These together determine how many watts you need to deliver the required amount of sound (in dB).

As to the Max power, what you want to avoid is destroying your speakers. There are two major ways of destroying a speaker - mechanical and termal. If the speaker has to make movements that are just too large, something will break - the membrane rips, voice coil bottoms out and gets scraped, or whatever. And if you put too much electrical power into the voice coil, it gets too hot, and breaks.

Especially the mecanical limit depends on the frequency - low bass is most likely to break the speaker (depending on the resonant frequency of the speaker). So the max power limit reflects some idea of typical music power that won't break the speaker.

On a multi-element speaker (one with a separete tweeter), the power handling capability of the tweeter is usually much more limited than of the main/mid speaker, as there usually is much less energy in the upper frequencies. But if your amplifier clips and produces heavy distortion, it might produce enough energy in the high frequencies to blow out your tweeter even if you are within the power handling capability of the speaker system.

To make everything far more complicated, the enclosure and mounting of the speakers has a large effect on it's power handling (and even efficiency). Let's not go into that....

Confused? You will be even more confused after the next episode...