Printer Friendly Forum Posts - Not Enough Power? Or Knowledge?

Sorry for the probably obvious to most questions, but I have never experimented with speakers until now...

2001 Chevrolet Silverado 1500HD Crew Cab

- Just installed Alpine 6-1/2" Type R Components In The Front, 6-1/2" Type R Coaxials in the back. Wired directly off head unit (40w x 4 - Also Alpine Din & a Half) and I am disappointed with their output. I believe the obvious is that in order to have it louder and crisper, I need to step up to the plate and install a 4 channel amp. Looking to stay with Alpine, and considering the MRV-F345. I will eventually add another amp to run 2 10" Alpine Type R Subs, but for now looking to resolve the first part of my install.

Can anyone advise/help me with resolving my issue? I don't understand the full use of watts per channel in relation to ohms, and after reading the info on certain amps, I'm lost. I don't want to purchase another part and be unhappy with it again.

Also, I'm sure there are those out there that will criticize me for using all Alpine, but I just wanted to stay consistent in the whole vehicle. I'm not out for competition, just good clean sound (that can be played somewhat loud).

I appreciate any advice/help in advance.

the problem you have is that your headunit is rated at its peak output power not its RMS output power, the headunit is probably something like 18wRMS x 4

The speakers you have are 4 ohms, you should be looking at a 4 channel amp that gives you approx the RMS power that your speakers are rated at when running at 4 ohms

First off, keeping all the electronics "consistant" from a single company only helps you when it all gets fried & you have to send it all back - you can use the same box. Nothing wrong with Alpine stuff, but why limit yourself? anyway...

Ohms work like this - an ohm is a measure of resistance. If you put a wire across your battery terminals, there's no resistance (& you'll melt things). By putting resistance in there, you're metering the amount of current flow. More ohms = more resistance = less current flow (or fewer watts per channel). Speakers have resistance - usually 4 ohms each in cars. Amps usually rate their output when using a 4 ohm resistance (IE one speaker), but frequently will also give ratings at 2, 1, even 1/2 & 1/4 ohms. Anytime you cut the resistance in half, say from 4 ohms to 2, you'll effectively half the resistance "between the battery terminals" (in this description) and double the amount of current flowing. But ignore those ratings for now, it just confuses your baseline of comparison.

look for a 4-channel amp that has RMS (that's constant output) of about 50 wpc into 4 ohms. Good place to start. Go bigger if you want more. Like NicP says, watch out for the "Peak" power rating, that's the RMS plus the headroom reserved for musical peaks - usually twice the RMS but not sustainable for more than a few millisecs. Companies use this number as a marketing ploy to make you think you're getting more than you are - like your headunit did.

Invariably someone's going to try to sell you a 2-channel amp & tell you to run it at 2 ohms (meaning two speakers per channel output - - effectively doubling up). What this does is in theory doubles your constant power output from those 2 amp channels by cutting the resistance (ohms) in half. Don't ask how, that's another topic. What you're doing here is tricking the amp into putting out twice the power, which is fine. What they won't tell you is that the amp's ability to respond to musical peaks - the amp's headroom, or peak power - can't be doubled.

So say you've got a 100w RMS amp with 100w of headroom, you trick it into doing 200w RMS by operating in 2 ohm, but still only have 100w headroom. The amp can now only respond to peaks with 25w per speaker instead of 50w. It makes the music louder, but much less dynamic.

So the take-home message is to stay with a four-channel amp w/1 channel per speaker for best results. Do that & you can mostly ignore all the ohm ratings.

Alpine amps are a little more confusing than some others. They will produce a given amount of power no matter what the impedance of the speakers are. Have a look at several different brands of ampifiers...look at the output ratings...and it will click as to how an impedance load (measured in ohms) causes an amplifier to produce output differently.

Without impedance, there is no power output. Thus, when you install your amplifier the deck would then become the "preamp", and will not provide power. It will perform at its best this way.

Don't feel like you have to understand Ohm's Law and all the variables associated with power, current and resistance right away. It takes months of study to grasp it all. Other than this forum, which in time will provide you with just about all the info you would need...another site to look at is https://www.BCAE1.com.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Thanks to everyone for the replies! (NicP, boulderguy, stevdart)

Looks like an amp will be the key to unlock the potential of what I just installed.

I will look at a few, I've read in other forums about pro's & con's of various brands, will be going out today and checking a few places out.

On the same subject, once I install the amp, should I run new wire to each speaker from the amp, or simply splice in at the door jambs inside the cab, or run wires back up to behind the head unit and tap the factory wires? I've already installed them in the factory wiring, soldered, but I want to do it right from here on out. Any help is again appreciated, I've never installed an amp either. Basic wiring no problem, hookup the right way, unknown by me.

I always run all new wire. It takes a little longer but better safe than sorry.

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Nik
Jeeputer Progress
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Check it out.

I agree - if you're doing the amp, might as well do new wire too. Don't take a 2nd mortgage on it tho - a decent quality 16 guage is fine for 50wpc +/-. And Stevdart's right, you don't need to grasp Ohm's law at this point, just know enough to be able to look at the same type of specs when comparing equipment (EG - power produced at 4 ohms RMS). Apples to apples, you know.

Great Info & Thanks!

I stopped at a few places this weekend and two different shops both refered me to the JL Audio 4 Channel Amps, either the e4300 or the Slash Series 300/4. Onces price conservative, the others alittle higher. Any recommendations or other brands to refer to ?

Thanks again for all the help! It's been a relief! Nothing like a holiday weekend project...

I'd spend the extra $. It sounds like the car audio bug has bitten you, and if so, you'll just wish you had gotten the better amp anyhow. Regret's more expensive than credit card interest rates.

The JL amps are excellent choices. I hear the MB Quart amps are good, but I haven't listened to them (anyone have an opinion there?). I'm partial to Soundstream. There's plenty of higher end stuff, but you'll pay for it. If you ain't afraid to Ebay you'll find some screaming deals.

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I've looked around eBay and found better deals than the shop (no overhead of course). I'm considering the JL 300/4 which states:

75 W RMS x 4 @ 1.5 ohm-4 ohm (11V-14.5V)

My 6-1/2" Components in the front say they are rated @ 70W RMS (4ohm) (Peak 350W). My rear 6-1/2" Coaxials say they're good for 50W RMS (4ohm) (Peak250W). If I use the amp, do I have a higher chance of blowing the rears since the amps gonna push 75w to them? Or is that only if I crank it hard?

It sounds like the amp will be plenty to run all 4 channels, but am I going overkill and risking damage to the rears? (Dang Audio Bug).

Now that I'm commited, I can't stop there. Subs & Amp. Considering 2 10" (Rated @ 300w RMS @ 4ohm) Alpine Type S with a JL Audio 500/1 (500 W RMS @ 1.5 ohm-4 ohm (11V-14.5V)). Obviously I'm not maxing the RMS power out to the subs since I'm running two, but would I be happy with this setup (thump for the buck) - also keeping in mind I'm not trying to blow out my windows. I looked at the type R 10", but they are rated for 500w RMS (two of those would only equal 250w RMS from the amp, so why not run a smaller rated sub right? (I think I'm catching on to this now - Man, I really hate this audio bug!)

Thanks in advance for the replies - hat's off to you boulderguy! Big help!

if you are sensible there wont be a problem, you can just turn the gain down on the amp for the rear channels

Ive heard that the type r is far more superior than the type s subs, do you really need 2 subs? maybe you could investigate getting a single type r, maybe a 12"

First of all, your interior vehicle space really isn't very big - a single 10" or 12" would be fine IMO unless you're really looking for some bump. I like the sound of a 10" better, you lose a tiny bit of the very bottom end, but in truth very few musical tracks have anything but secondary resonance that low and even fewer people's ears are good enough to hear it. If you're going for purre musicality, stick with the 10", it's usually more accurate. If you want to feel the power, go 12", it'll have more true output with the same wattage.

Second, and again IMO, placed head to head the JL subs are HANDS DOWN better than the Alpine, provided both are set up correctly in the right type enclosure. I would go for a sealed box, no ports, but I'm partial to very tight, conservative & musical sound. Ported will give you more volume, but it will tend to peak at a certain frequency & have more "boom." You really need to listen to both to decide. One of them will speak to you. In reality, you can't go wrong with either Alpine or JL, but the JL Stealthboxes are very tough to beat if they make one for your truck.

Last, about power - how do you keep asking all the right questions? Power ratings on speakers are tricky. Here's the deal: 9 times out of 10 a speaker only blows because the amp is overdriven, not the speaker. Remember Headroom, the peak output of an amp responding to music dynamics? When that's depleted & the amp can't deliver enough power, it "clips," meaning (very oversimplified) it distorts. It's these distortion spikes that will cook a speaker, not the clean power even if it's more than the speaker's rating allows. I have a single 10" sub rated to 250 watts. I run 400 to it, but it's very clean power & never overdriven. 4 years old, never had a prob. My satellites are rated to 70wpc, I consistently send them 100+ (large class A amps), again no problems. I largely disregard speaker wattage ratings because if it's respectably built, clean power up to sometimes twice the spkr rating ain't no problem.

Now the disclaimer - this isn't a license to get crazy with your gear, and I'm not responsible if you start a campfire in your car doors. Just use your head & be sensible (don't run 1000w into a 500w sub, but 700's probably fine), and for God's sake turn it down if you hear distortion! Otherwise your amp choices sound great.

Enjoy it, if you get quality gear now it'll likely follow you car to car. If you get the cheapo stuff, you'll hate it & replace it 8 times, ultimately spending way more than just doing it right the first time. And when you install it, buy your wiring at Partsexpress.com for 1/3 the price of the shops. That's another topic.

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Hey, one other thing - reread your question (why didn't I do this in the first place?), that sub amp will send 500 watts into a single channel only. You plug two subs into that channel, you'll cut the ohms in half (down to 2) and theoretically double the output to about 500w EACH, plus cut the headroom in half (that's bad). That's 1000w of bass, enough to compete for most-ubsurdly-loud-truck award in your neighborhood. It'll also completely overshadow the other speakers.

Go with a single 10 or 12 with that amp, it'll complement the other speakers well & you'll probably never max it out. You could probably get away with the JL 250/1, tho you'll push that amp harder.

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that particular JL amp is rated at 500w from 1.5 ohms to 4 ohms, often when you half the load impedence the output doubles but not always, and not in this case

boulderguy wrote:

First of all, your interior vehicle space really isn't very big - a single 10" or 12" would be fine IMO unless you're really looking for some bump. I like the sound of a 10" better, you lose a tiny bit of the very bottom end, but in truth very few musical tracks have anything but secondary resonance that low and even fewer people's ears are good enough to hear it. If you're going for purre musicality, stick with the 10", it's usually more accurate. If you want to feel the power, go 12", it'll have more true output with the same wattage.

Yes, I agreee that on sub is USUALLY plenty for a car, however, in the rest of your statement, there is FAR too much of a generalization to be even CLOSE to the truth. I was using an Eclipse Ti10, on the Eclipse DA7232, and it went a good half octave deeper than the Ti12 I "upgraded" to. Both boxes were optimal sealed designs for the WOOFER ACTUALLY INSTALLED, not based on Eclipse's claims of the production run's specs... How did I get these numbers to build the box? Both of the woofers were taken to my engineer friend at Harman, in Northridge, where he put them on the Klippel machine (a very expensive and accurate loudspeaker testing machine, alongside the DUMAX system, also very highly regarded), and we got the EXACT specifications for those drivers. Also, efficiency determines how loud a woofer will play, not how big the diaphragm is.

All I am saying, is that it depends COMPLETELY on the specifications of the driver, as to whether a 10" or 12" driver will play deeper or louder... I have seen an 8 inch driver play deeper with more output than some 15 inch drivers.

Also, I have many CDs in my collection that have VERY HIGH levels of sub- 25 to 28Hz fundamentals - not harmonics, I promise you... Check out Alphaville's "Dangerous Places" (this one's a tweeter-eater too, so be careful), Enya's "Longships", most any track from "It Came From Outer Bass". All three of those selections/tracks contain high-level fundamentals as low as 18Hz... And EXCEPTIONALLY clean recordings too, I might add. They WILL beat a vented woofer to DEATH...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

See that, anytime time you boil down complex subjects into a paragraph, you're bound to tick someone off. Of course it's a generalization. And of course you & everyone else has a personal story where the rules of *What's Typical* just don't apply. The idea here was to make a lot of info digestable & not overwhelming. A 12" moves more air than a 10", and therefore *usually* has more output.

And the only instrument I know that drops below 40 hz with a fundamental is a huge pipe organ. What are those recordings using? Particularly Alphaville?

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Well here's what I believe I'm gonna run at this time. The posts have been good to me (thanks all for the advice):

Tell me what you think; I'm looking for some opinions on the final call before I spend the bucks.

JL Audio 300/4 to Push the Door Speakers (75w RMS @ 4 @ 1.5ohm to 4ohm 11V-14.5v)
- (Front) Alpine Type R 6-1/2" Components (70w RMS @ 4ohms, Peak 350w)
- (Rear) Alpine Type R 6-1/2” Coaxials (60w RMS @ 4ohms, Peak 250w)

JL Audio 250/1 to Push the Sub (250w RMS @ 1 @ 1.5ohm to 4ohm 11V-14.5V)
- Single JL Audio 10” 4ohm 10W3v2-4 (300w Continuous) – Requires 0.60 to 0.90 cu.ft. Enclosed
Mounting Depth of 5.75”
- https://www.subthump.com/gmcrewamp.htm
Single 10” Down-Fire Configured Sub Enclosure (0.60 cu.ft.) – Mounting Depth 5.5” or 6” with Spacer

This just brought up another speed bump/question. My head unit only has two preouts, front & rear. Once I add the sub & amp, how am I going to get the input for it? The JL 250/1 does have a preout on it for the next amp. My Alpine head unit says I can change the settings to leave the front preouts unaffected by the fader, so would I run the front preout rca to the sub amp, then from the sub amp preout to the front channel input on the 4 channel amp? And run the rear channel preout from the HU directly to the rear channel on the 4 channel. Sounds right to me, but need advice (as always). I don’t want to upgrade the HU at this point, I’m working up to a flip-out DVD multimedia player, so don’t want to cough up money for a new HU just yet.

I think I almost got it. Maybe.

posted_image

boulderguy wrote:

See that, anytime time you boil down complex subjects into a paragraph, you're bound to tick someone off. Of course it's a generalization. And of course you & everyone else has a personal story where the rules of *What's Typical* just don't apply. The idea here was to make a lot of info digestable & not overwhelming. A 12" moves more air than a 10", and therefore *usually* has more output.

First, I was not trying to "tick somebody off" nor was I ticked off... I was not even saying you were completely wrong, but again with the generalizations. A 12 inch woofer will not necessarily move more air than a 10 inch woofer, and even if it DID move more air in every situation, that alone would NOT make it louder. Volume of air displaced is NOT what makes output. Rate of change is what makes output - how FAST can the woofer change direction from in to out or vice-versa. This is where magnet size, magnet strength, moving mass, voicecoil inductance all come into play. NOT the size of the diaphragm.

If the statements you are making were fast and true, then you would need thousands of watts to make a small diaphragm like a tweeter make as much output as an 18 inch woofer - and that does not happen, does it? I never said that "what's typical" does not apply, but I did say that in audio you CANNOT make generalizations like those...

boulderguy wrote:

And the only instrument I know that drops below 40 hz with a fundamental is a huge pipe organ. What are those recordings using? Particularly Alphaville?

Here is a handy little chart to refer to when making statements like this... The piano's lowest note is 28Hz... (27.5Hz, actually) almost a full octave BELOW where you thought it cut off... Here's another, with a realtive loudness chart.

As far as the questions regarding what types of instruments - Ok, I'll give you the Outer Bass stuff, it's all synthesized, so it's cheating. Enya? a 32 inch kettle drum. Alphaville? Don't know, but it really does not matter, as I have already proven your generalizations false... The fundamentals are there, and it is necessary for a woofer to move a lot of air to reproduce these fundamentals accurately, it is true, but a 12" will not always do the job better than a 10" or even an 8".

All I am saying is be careful with the generalizations. They are just that - general - and can EASILY be rebutted.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

About instruments below 40hz, that was actually a question, and the chart you gave was interesting - I've been educated today, thanks.

haemphyst wrote:

Don't know, but it really does not matter, as I have already proven your generalizations false.

No. What you've proven is that my generalizations are not always true. That's why they're general, not hard facts.

You've also shown that some bonehead is always going to take things personally and make it a mission to disprove them, ultimately confusing the issue & defeating the purpose. Who the hell uses the last four keys on a piano anyway? And who plans their speakers around that?

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Now that those issues are resolved, can someone send some advice my way on my last post? I understand I've had way more help than I probably should have, but let's get back on topic. Keep in mind everyone will have their own opinions and outlooks, and regardless, we are all here for the same, Car Audio Help! At least I know I am, I'm the newbie here!

I appreciate everyone's advice and words, I wouldn't know what to do without this site/forum. Heck, I thought I'd have a fight on my hands when I posted I was looking to stay with all Alpine, but people made some good suggestions and now I'm not cutting myself short! Opinions are good, and in this site several heads are better than one!

Discussions like the above are good in general...educational for us all. Sometimes during a thread, as your intent changes from one subject to another ( remember "Not Enough Power..."? ) it becomes necessary to start another thread. It's not often we can enjoy the heavy-hitters here, so I'm all for a little educational diversion from time to time. I got two new links out of it as well, which I'll get more familiar with and use in the future. Hope some of the other regular members do the same...

Use the preout that is meant for the sub to the sub amp, the other full-range preout to the 4 channel amp. Use splitters on that one to feed the extra two channels. Your head unit will have a control for sub out, I believe, IIRC, and one of the preouts will be designated for sub use.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Well Said.

The back of my head unit (Alpine CDA-D852) only has PreOut Front & PreOut Rear. No Sub Preout. Per the Alpine Manual it allows the following setting:

Non Fading Pre-Out (N.F.P.)
- NFP On - In this position, the front Pre-Out will not be affected by the fader.This is ideal for driving a subwoofer
amplifier.

So what would be the best choice for hookup?

1. Front Pre-Out With "NFP On" To The Sub Amp, Then From The Sub Amp Preout To Front Input On 4 Channel
2. Front Pre-Out To 4 Channel, Y'd Out To Front & Rear, Rear Pre-Out To Sub Amp

As I mentioned, I don't want to purchase a new HU just yet, waiting to save alittle more and get an in-dash DVD. The flip-out I'm looking at does have 3 Pre-Outs (Alpine IVA-D310). Wife would not be happy to spend another $1300 at this point!

Your going to have to hook it up and try it out, then try something else, until you find what you like. Each configuration is going to have pro's and con's. The NFP-On option would be most useful if you were driving a pair of speakers off the deck. Personally I would drive the 4 channel off the front pre-out's sub separately on the rear. Turn the gain on the rear channel down at the amp. And use the fader to help balance out the subs. The rear channel level will probably be more consistant between different songs than the sub level. I would not tie the rear channel level with the subs if you could help it. My antique Pioneer has the one set of preout's tied to the rear fader. I would have to pop the trunk and adjust the gain on the sub amp too frequently depending on what I was listening to. But like I said you need to hook it up and try it out until you like it.

I like option #2 for more flexibility - you're more likely to adjust sub volume on the fly than you are the front to rear fader. It's all temporary til the new HU comes in anyhow.

That brings up another question - does your main amp have an x-over, or is it running full range? If it has an x-over, I'd DEFINITELY use that, I like 80-90hz, but it depends on your ears & how the individual speakers do.

The other thought I had was the box size. .6 cu ft for a 10" ain't huge, and it means it won't be super efficient. It's certainly within parameters & will sound very tight, but generally a smaller box requires a bit more power than a larger box to get the same sound from (let's see who attacks that statement). It'll really depend on how efficient the sub is & how much bass you want. Check it out early, if it feels like you need more power, take the amp back & trade for a larger one. Most shops are good about that if the amp is still new. I still believe the 250/1 is a good place to start.

Good luck.

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I noticed something while readin a few descriptions of lower ohms equal higher wattage.

With a standard AC current, meaning no transformer, the higher the ohms the HIGHER the current. 120v = 120/1, 120v = 240/2, 120v = 480/4. Get the point?

Anyways, the difference is that an audio amplifier is a VOLTAGE source, not a current source. As you half the ohms you double the VOLTAGE. Notice the difference?

Now that I've said that it probably seems obvious to you, but I bet alot of you never knew exactly WHY the current increased when lowering the ohms.

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Poormanq45 wrote:

I noticed something while readin a few descriptions of lower ohms equal higher wattage.

And you feel this is wrong information?

Poormanq45 wrote:

With a standard AC current, meaning no transformer, the higher the ohms the HIGHER the current. 120v = 120/1, 120v = 240/2, 120v = 480/4. Get the point?

I honestly have no idea WHERE you are getting these numbers from. I agree with your math, but I think you are transposing your constants. Whether you are dealing with DC to AC conversion in a switching power supply (like in a car amplifier), or AC to AC, with or without a transformer, Ohms law says that this is so: "watts equals volts times amps" or "volts (squared) divided by impedance"... it does not matter at all... If you double the input voltage from 120 to 240, you will halve the input current for the same output power. Is this what you mean?

Poormanq45 wrote:

Anyways, the difference is that an audio amplifier is a VOLTAGE source, not a current source. As you half the ohms you double the VOLTAGE. Notice the difference?

Nope. This is WRONG. If you have one 4 ohm woofer, you have X voltage across it, if you put another in parallel with that same woofer, your output voltage from the amplifier does not double, does it? No, the amplifier will try to maintain that same voltage by producing more current. You are correct - an amplifier IS a voltage source, as it will try to maintain VOLTAGE by producing more current. A current source will output a fixed current, and adjust the voltage to make sure that current always stays at the preset level.

Poormanq45 wrote:

Now that I've said that it probably seems obvious to you, but I bet alot of you never knew exactly WHY the current increased when lowering the ohms.

...huh? this is exactly the OPPOSITE of what you said above...

boulderguy wrote:

It's certainly within parameters & will sound very tight, but generally a smaller box requires a bit more power than a larger box to get the same sound from (let's see who attacks that statement).

Well, since you seem to think I am attacking you, rather than trying to offer help and a bit of knowledge, I'll take that... except I am actually going to agree with you (weren't expecting THAT, were you? {emoticon SPECIFICALLY left out}). You are correct, in a smaller enclosure, a given driver will require more more power to achieve a given output. Dude, please lighten up a little bit, and recognize when people are offering experience and knowledge, and NOT attacking...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."