Sorry, but this is wrong.
Never in my life have I come across an instance where someone has computed the root mean square (RMS) of a power[sup]1[/sup] signal.
“RMS power” has no practical utility, and therefore the term should not be used.
[sup]1[/sup][sub]Where power = V*I and has units watts.[/sub]
Well, head units certainly list RMS power in their spec sheets. What do you suppose that number is, if not root mean square of a power signal?
Crafter_Man is technically correct.
The instantaneous power curve has a sin[sup]2[/sup] shape. If you do the RMS calculation on it, you’ll get P[sub]RMS[/sub] = √3/(2√2) x P[sub]Peak[/sub].
What you really want is P[sub]average[/sub] = 0.5 x P[sub]Peak[/sub].
The term RMS is properly applied to voltages and currents. For a sinusoidal voltage, you get V[sub]RMS[/sub] = 1/(√2) x V[sub]Peak[/sub]. If you calculate power using the RMS voltage, you automatically get average power.
The “RMS power” that’s referred to in the spec sheets is actually average power, calculated from RMS voltage.
Desmostylus is correct.
I don’t know why car stereo manufacturers use the term “RMS power”; they should say “average power.” At any rate, my best guess is that term "RMS power” implies that the power was computed using RMS measurements of voltage and/or current, as opposed to an el-cheapo (and usually wrong) “apparent power” measurement.
Like has been previously stated, any name brand deck (i.e. Sony, Pioneer, Kenwood) that is listed at 40-45W x4 will sufice. True, that rating is an exagerated peak power but it will sound fine at its true clean output, whatever it may be.
The only way you risk damaging your speakers with this deck is if you play with “noticible” distortion. That scratching sound coming through.
A lot of speaker damage comes from people driving on the freeway with thier windows down, cranking up the stereo to hear it, and with the car and wind noise, fail to hear the distortion in the speakers.
Or they crank up the bass and play it too loud it will cause the distortion.
SenorBeef: I have never owned, or even operated, a CD player that does MP3s. From what I have read, though, some are far easier to use than others, even among the good brand names. Some take forever to load the tracks, others make it hard to navigate through your different folders, and so on.
For that reason, I’d strongly suggest that you do some searches on the discussion forums of Car Sound magazine. I recall a lot of talk there about which MP3 players work better.
http://www.carsound.com/cgi-bin/ubbcgi/ultimatebb.cgi
If the rear speakers are still okay, you might consider keeping them, at least for now. Factory 6x9s will generally produce plenty of bass and midrange without a lot of power—but they lack treble because they probably don’t have separate tweeters. But that’s okay, because high frequencies from the rear don’t sound natural anyway.
(Many car audiophiles remove their rear speakers altogether so that the system sounds more concert-like—that is, all the band members are in front of you. But 5 1/4" front speakers don’t produce much bass, so in your case, you’ll be needing those 6x9s to handle the low end.)
As for front speakers, buy whatever sounds good to you. A good store will have a sound board that allows you to demo the speakers driven by a regular car radio, preferably the one you’re considering buying—and hopefully with your own music, too. They won’t sound the same in your car, of course, but it’s better than just buying them blind.
Ask the salesperson if you can exchange your speakers for different ones if you don’t like them, and also ask if you’ll be charged extra installation labor for doing so.
I have never noticed any benefit from “bass blockers”, which is 50 cents worth of capacitors that Best Buy peddles for $10 to anyone who will listen. If you’re worried about your speakers that much, put the $10 toward an extended warranty instead.
I’ve had the same Sony head unit through two pairs of OEM speakers. I always play it at the same level and my CD range doesn’t change much over time…
HOWEVER, when I had the head unit installed I blew the OEM speakers in 2 weeks (3 of 4).
I went back to Best Buy, bitched a lot, and they put in bass blockers and paid for new OEM speakers… haven’t changed anything except adding the bass blockers and all 4 are intact and happy 9 months later…
I stand corrected. Thank you.
Thanks for the forum, that should help a lot.
Where’s the best place to buy car stereo stuff? Chain places like best buy? Little independent shops that specialized in car stereos? Buy the parts yourself off the internet?
I have a friend that could probably install stuff, but I’d really rather have professionals do it. What sort of fees would you expect to install a head unit and front speakers?
no you dont need an amp.
i do have a 1000 watt rms rockford fosgate amp capable of leveling a block, but its connected to dual 12" MTX8000 subs that actually can handle this power. if you gona use some teeny 5" speakers, then you dont need more power than stock unit. the speakers will be the bottleneck.
peak power is a meaningless parameter. car audio is the only arena where this term is even used, this is cause car audio is sold to teenagers who have no clue.
you should not only use RMS power but also buy a product from reputed manufacturer, cuz many car audio amp manufacturers will lie.
ask on some car audio forum if whatever brand you’re looking at is not garbage.
rockford fosgate is actually same company as Hafler i think, which make professional and studio amplifiers, thats why i got it.
SenorBeef:
The chain stores offer average prices, product in stock, fast install, nice atmosphere, extented warranties are available if you want one, and there’s a chain of command to complain to if you have trouble. I used to work at both Circuit City and Best Buy, by the way.
Warning: Best Buy employees are great pressure to move accessories, so be prepared for that. If you tell me what kind of car you have, and whether the exisiting equipment is factory or aftermarket, I can tell you what parts you do or don’t need.
At the chain shops, you’ll get the quickest install on weekday mornings—they typically open at 10AM. Weekends will be far busier. Make the chain store your FIRST stop, so you can shop the rest of the mall while they’re installing your gear.
An independent store will probably have slightly higher prices and a smaller inventory, but may be able to give you a better install and superior service. The shop I work for will do whatever it takes—we can come to you, we can give you a ride to work, we have drivers who can pick your car up…we do good work, but we also are always ready and willing to fix things if we’ve made a mistake. Sadly, some independents are just the opposite, so try to ask about your friends’ experiences before choosing.
You can definitely get some good deals online or through mail order, but beware—sometimes you’ll end up with refurbished product, or last year’s model. You might start at sounddomain.com or thezeb.com; those places are not the cheapest, but they are both pretty large operations. I have no experience with either, so I’m not making a recommendation—just giving you a starting point.
Also, have you heard of Crutchfield? They’re probably the most well-known mail-order outfit. They charge the same prices as the chain stores, but they offer knowledgeable salesepeople, free install parts, and tech support if you do it yourself. Their catalog is worth getting, even if just for the buying advice in there. crutchfield.com
Some shops won’t install gear purchased elsewhere, some will charge extra for it, and some won’t care at all. So do ask around first, if this is what you plan on doing.
Typical install prices: (this is for an ordinary car, or “basic install” as they say)
Head unit: $50 labor
Wire harness: $10-17 (this plugs into your car’s factory wiring, so they don’t have to cut it up)
Dash kit: $10-17 (if the new radio is smaller than the factory one, the kit makes it fit)
Antenna adapter: $10 (Some cars have unique antenna connections: Nissan, GM, 2002 Chrysler, some Ford, most European)
Speakers: $30-35 labor (per pair)
Wire harness: $5 (same as the radio harness, not available for all cars)
In my state, by the way, sales tax is only paid on product—the radio and the installation parts. There is no tax on service (labor) here. You may want to check how it works in your state.
crutchfield’s prices are ridiculously high. and the chain stores i would not even bother going to cuz all they sell is junk like sony and aiwa. i would buy somewhere online, and any car audio shop will install it for you for not too much $$.
I think I missed this the first time around. Knowing what I need would be very helpful.
It’s an 88 grand am with whatever standard GM radio they were using at the time with AM/FM and casette. All stock.
'88 Grand Am.
Wire harness— Metra part #70-1858 if memory serves. $17 full retail; about $4-6 wholesale, depending on the dealer’s buying power.
Antenna adapter— Metra #40-GM10. $11 full retail; about $1-2 wholesale.
Dash kit— The best kit to use is the Metra 99-4544, $17 full retail; about $6-8 wholesale.
The 99-4544 has a variety of front faceplates for the installer to choose from. One is flat and looks nice. The other ones stick out of the dash and look lousy, but this is to allow for more mounting depth.
On all the Grand Ams I’ve done, I’ve managed to use the flat face, occasionally having to trim away a few plastic bits inside the back of the Grand Am’s dash in order to do so.
There are plenty of other dash kits available for these cars, including the Metra 99-4500, but they all have bumped-out faces. I don’t like the look of them, but you might not mind.
It is highly likely your installer will have another customer’s GM vehicle that is being worked on. If you’re at all concerned about the appearance of the dash kit, ask to see how it looks in a similar car.
Speaker harness—I forget the part number for those, but they are available. $5 full retail; $3 wholesale.
Other things to keep in mind:
Most likely, the radio you buy will have a detachable faceplate, to deter theft. All radios except the low-end Pioneers will come with a plastic case for the face. The store may offer to sell you a fabric or vinyl case, and they are pretty stylish and durable.
But some people never both taking the face off anyway—if you’re not sure if you’ll do it, live with the regular case for a while before shelling out for the nicer one.
Also, I’m pretty sure those cars take a 3 1/2" in the dash, which is a very small speaker. It might be possible to shoehorn a 4" in there, but they’re going to charge you extra. 5 1/4" isn’t going to happen. Not unless you want to go with a non-factory location, such as cutting them into the doors.
Since your front speakers are so small, you might benefit from a radio that includes a crossover—that is, a device that will prevent low bass from making its way to the front speakers.
If you feed bass to those little speakers, they won’t make much bass sound anyway, and they’re likely to sound distorted from trying.
Higher-end Pioneer radios (including their three MP3 models—the DEH-P7400MP, 8400MP, and 9400MP) have this feature.
Also, you mentioned that your current system loses reception sometimes. It is hard to say whether this the fault of the radio itself, the antenna, or the antenna’s wiring. Since you plan to replace the radio anway, just go ahead and do it—and it is most likely the radio that is bad, anyway. But you’ll find out for sure after you replace it.