CLSmike

Hey guys are our speakers 4 ohm or 8 ohm...also most amps what are they 4 or 8 ohm.....I have a boss 650 amp....but its in the shop with my car and i cant get to it...also im getting the type s alpine 12 inch subs and was wondering i i should get the 8 0r 4 ohm thanks for the help?

AztecRol

iTrader: (2)

I don't know what our speakers are rated at, but if the amp you have now can handle 4 ohm loads, get the 4 ohm speakers!!!! 4 ohm speakers will draw more watts out of your amp!!! Most, if not all, of todays car amps can handle 4 ohm speakers with no problems!!! Most can actually handle 2 ohm loads!!!


Most amps are rated for 8 ohms, but can handle 4 ohm loads, just to make sure I answered your question. Just go online and get the specs for your amp. I am sure you will be fine!!

chrw

Almost all car speakers (non-subs) are 4 ohms. Amps are 4 ohms but some can handle 2 ohms and even lower. Subs can come in a variety of configurations--2 ohm, 4, 8, as well as single or dual voice-coils. Unless an amp is stable at 2 ohms try and make your sub configuration ending up at 4 ohms. If you're getting just 1 Alpine sub go for 4 ohms. Good luck

3.2cl-s

Depends on how good your amp can hold low ohms.......i used to have 3 RF 12's and they were only 4 ohm speakers.........so i was running the amp at 1 ohm, the lower the ohm, the more power, US amps, which was the amp i was using, can handle down to a 1/4 ohm....very good amp IMHO.

SilverKnight

hehehe, at first I thought you guys are talking about home speakers .

Now a day, in car stereo, output power (in watts) is rated at 4 Ohm load unless specified otherwise. Most of the amp in the market are 2 Ohm safe. Some mono blocks can handle 1 ohm. I would go with 4 ohm because of the Boss (you meant 650 watt, right? if the amp takes 650 Amp x 14.4 V = 9360 watt your alternator wouldn't last 10min ) runs very hot. Do not put any load less than 4 Ohm on that sucker.

The impedance of the Blose speakers is uncertain. Words say they are low impedance but no one knows for sure (except for the maker who is somewhere in Asia)

mattg

actually i think they may be high impedence speakers.

EricL

I “believe” that the Blose in our cars (the CLS) are 4-ohms. I’m basing that on the type of power amp they use (no switching supply, but full-bridge/floating output), the volume that is output, and my experience with the 1-ohm speakers in the Maxima (smaller, but they had the acoustic chamber, $hity cone material, and power amp built into the speaker). There was a guy who I talked to who replaced the el-cheapo caps in the “crackle-‘n-squeal Blose speaker boxes/amps”, and he said the speakers were 1-ohm. I measured them and it sure looked that way. I’m pretty sure the output per speaker was close to 50-watts x 4 speakers (they didn’t exactly run the thickest wires to the powered speaker assemblies)

I suspect that the, "Boss 650 amp" was like, "Well, I have a Boss model 650 amp".

You would be looking at more than 13-15HP to power the alternator (assuming some efficiency loss of the alternator and the 9360-watt figure .

Heck, they would weight the car down with all of the copper!


The 4-ohm seem to be pretty common for car speakers these days. It allows folks with powered head units to spec around 45-50 RMS watts per channel into 2-ohms or 18-22 RMS watts into 4-ohms, and 9-11 RMS watts into 8-ohms (Hey, nothing like using 14.x volts as the voltage your getting with the alternator shut off – hey? )

14.4 volts * 0.707 = 10.2 volts RMS AND power = V^2/R = 104/2 = 50 watts into 2-ohms speakers. The R is the impedance of the speakers in ohms (1, 2, 4, or 8 ohms)

There is a point, where the distortion will go up, and when it comes to speakers, it would be better to go with a 4-ohm over a 2-ohm especially if the efficiency of the 4-ohm was a good deal higher that the 2-ohm...

$0.02

BC

First, let me say that I know nadda about car stereo. Although I have a very good home setup. Sam Tellig of Stereophile magazine says that generally the higher the amplifier output the lower the quality of reproduced sound. I don't know why auto manufacturers push low efficiency speakers. My home speakers are 92db/watt efficiency. Thats 92 decibles of noise per watt measured 1 meter from speaker front. This allows me to drive the 150 lb./speaker dual woofer 3 way with only a 30 watt/channel vacuum tube amplifier. This low power integrated push/pull amp can drive these speakers way louder than even my neighbors can stand. Efficient speakers seem to let go of the notes more easily and many audiophiles are building or buying amps as small as 3 or 4 watts per channel which requires super efficient drivers, even horn designs. I went to a tube show in Silverdale, Wa. last summer and the very best of show was a 3.5 watt per channel triode tube amp driving a 10 speaker array. The soundstage went way to the left and right outside the speakers and had a 3D effect where you could easily perceive the soundstage depth. On an old 50's Muddy Water recording, you could hear that young Buddy Guy was standing well behind and to the right of Muddy. Very cool! I have not built a good auto stereo setup, but from years of study and experimentation on home audio, if I were looking to upgrade my type S, I'd look into speaker efficiency. Besides it would be easier on your car electrical system to power the amp. I don't post alot, but this allowed me to come forward and speak up on one of my hobbies.

chrw

Please tell me that you don't believe for a minute that a head unit will put out 45-50 watts RMS per channel. Sorry, I'm wrong, as long as LIGHTNING is hitting your head unit then it will put out whatever absurd claim the manufacturer says it will. Head units will *realistically* put out 8-15 watts rms per channel. Don't count on anything more than that, and use an amp instead--underpowering a speaker is worse than overpowering it (due to distortion).

Ciela

Go with the 4's! I put the 4ohm's in my car and they were fine. The car can handle them, no problem.....i bet you could even go lower. Lemme know which one you choose!

tmk70

I'd go with 2 "Ohms"

EricL

IF you are going to mention power, it would help to mention the impedance it needs to drive into – without that figure, you comment is meaningless.


If you are talking about a “cheap-o” head unit with some cruddy power amps running into 4-ohms, sure… The reason you will find some stuff that doesn’t cut-it, is they used amps with terrible designs and poor current output. When you only have 12.5-14.5 volts of “rail” to work with, you need as little drop as possible. The output will vary by huge amounts depending on topology, parts choice, and indirectly on max heat rise due to power amp topology (with new class-d ICs coming, expect non-switching supply outputs right around 50-watts channel into 2-ohms (x4) and 25-watts channel into into 4-ohms (x4)..

AND that 15-watts with a high efficiency speaker will be just as loud as a 60-watt amp with speakers that are 6db less efficient!

Testing isn’t that hard:

At least the test for a piece of audio gear is pretty easy:

1. Hook up a 12.5 to 14.4 volts DC supply to the radio (DUT) device under test.
2. Supply sine wave input and vary it from 20hz to 20khz.
3. Monitor RMS voltage into 2,4, and 8 ohms.
4. Hook-up distortion analyzer (THD, IM, TID, etc)

5. Then, decide what constitutes the maximum "acceptable" distortion at full power (5%, 2%, 1%, .1%, .01%, .001%), (In a pinch, a scope will show sine wave clipping with ease.) (If people only knew how much distortion there is in most speakers, they would be shocked!)


The makers rate with without any "solid" standards, however:

With a full-bridge amp, you get a MAX output close to 45-watts into 2 ohms, and that assumes 14.4 volts of DC supply. The 14.4 Volts is based on: no-sag/no line loss/no voltage drops in output devices at full load, and no current limiting. The current gain and Vsat and /or Rds of Mosfets in the output stage of an AB-class amp and/or class-D power amp can make for near zero losses. AS for the use of PWM amps in head units, I didn't see to many cheap DVD players for around a decade ago and now they are everywhere. The main problem with an A/B class amp is power dissipation and the cost of heat sinks. IC s keep getting cheaper, and metals keep getting more expensive. There is a cost incentive to head towards PWM/Class-D amplification in lieu of older class A/B amps.

So, do the math...

14.4 * .707 is around 10volts of swing.

The formula for power is V^2/R = 100/2 = 50Watts (2-ohms), 100/4 = 25Watts (4-ohms), 100/8 = 12Watts into (8-ohms), so on. (Hmmm… I don’t see that many 8-ohm speakers being produced for car stereos…)

Subtract a volt or two from the 14.4 to get to a "more conservative" value for an class-AB amp… (Dropping the peak-to-peak voltage to 12 volts give: 40-watts into 2-ohms, 20-watts into 4-ohms, and 10-watts into 8-ohms.

Finally, if you stick with PCM (class-D), you can get full peak-to-peak swing with low Rds Mosfets and at 98% efficiency, a head unit only needs to get rid of 1- to 2-watts of heat per output channel. That’s: (1 or 2 times 4, with a max dissipation of 4- to 8-watts for the complete head unit working at full power).

There is also the "peak" myth (and other games):

Some “folks” will take 14.4^2 = 207/4 and arrive at the 50-watts peak power into 4 ohms (It’s totally meaningless and just indicates that this power rating is based on the voltage from peak-to-peak. It is perfectly valid if you listen to 100% duty cycle square waves or driver stepper motors. (The .707 is an integrating factor used to compensate for the area of a sine wave with a given peak voltage. 0.707 = 1/sqrt(2).)

So, before you "guess" and impugn, you might want to try some simple math and ASK what a particular head unit maker is using in their head unit. AS with all things, there's hype and there's advanced technology. If you go to a class-D amp, it actually gets cheaper in the end, since the "power transistors" (in the form of a monolithic chip with a set of drivers can certainly cost less than the metal (aluminum, copper, etc) needed to sink the waste heat.

So, next time you looking at some financial info -- tell me how the price of aluminum and copper changes with time (up, up, up) and then see how many transistors they are putting in a CPU and see if the price is going up on computers, stereos, etc...

With the price of metal on a general trend upwards, and with the cost of ICs and Semis going down, plan on seeing more high-output head units that run very cool.

BTW, there are some speakers out there (and they are really good), that have THDs are not so hot...

3db in speaker efficiency is worth double the power -- do the math...


And here is a link about RMS and Peak power and how to calc it. And info related to the 3db (in case there are doubters):

http://users.chariot.net.au/~gmarts/amppower.htm


First, the 3db speaker info:

1. 20-watt amplifier with reference speaker for a given output
2. 40-watt amplifier needed for speaker with 3db less efficiency that #1
3. 80-watt amplifier needed for speaker with 6db less efficiency than #1

(That’s why a speaker with magnets of SmCo, NdFeB, etc and proper design can blow the doors off a speaker with a cheapo ceramic magnet and a BIG stand-alone power amp.)


Excpert from the above link on calc’ing power (RMS & Peak):
Here are some typical ways to measure AC power:
”RMS (root mean squared) power is a statistical averaging method of the power delivered by a sine wave at some arbitrary low THD (total harmonic distortion) level. "Low distortion" usually means "at the onset of audible clipping". For a sine wave, the voltage is the sine wave's peak voltage divided by the square root of 2 (approx 1.4), and the resistance is the speaker impedance. So an amplifier that gives 14 volts peak (that's 28 volts peak to peak for the positive and negative halves of the sine wave) into an 8 ohm speaker gives a power of: 14 / 1.4 = 10 volts, 10 x 10 = 100, 100 / 8 ohms = 12.5 watts RMS.

Peak power has been used in the past to give higher power ratings to the same amplifiers. This simply uses the actual peak voltage value in the "voltage squared divided by resistance" calculation. It is not realistic, because this power is delivered for only an instant, and the amplifier could not sustain that power continuously. So in our example above, the peak power would be 14 x 14 / 8 = 24.5 watts (actually, its exactly double the power). Fortunately, this is rarely used now, partly because there's an even better way to cook the books ...”
(Note: [again] 1/sqrt(2) = 0.707)

Power vs. db (check speaker efficiency…):




The limitation that you mention is not intrinsic to any “design” issues, but simply “scamster-esque” issues where the car people have not demanded “solid” tests and well-defined figures from the makers. If you notice, most of the makers don’t even specify the load for a given RMS output. Alpine does spec RMS power (around 27watts x 4) in one of the higher line units and based on the common “4-ohm” speaker, that’s not suprising.

You don’t need a switching power supply to get 40-watts into 2-ohms/channel. The voltage is there. If anyone is measuring lower voltages it is due to “cheaping-out” issues and/or heat issues!

I’ve seen the reviews and reviewer comments, and there is so many misstatements from both sides, that it makes it hard to know which unit has the juice and which didn’t do to “cheap-out” reasons…

BTW, one of the comments from some car audiophiles that I find so distressing are comments about how head units’ power supplies not be able to supply all 4 channels. What power supply? Outside of a few Alpine units with voltage boosters, they feed right on the 12.5-14.5 car voltage, and there is no power supply to task…

Alpine with V-Drive (higher power, but will sag with all 4-channels running)

V-Drive is volume, and plenty of it! Ingenious as it is rugged and reliable, the V-Drive power unit boosts the incoming voltage up to 17.2 volts — the built-in chip then converts this extra voltage into 60 watts peak power x 4 (27 watts RMS) — the most true power you can get from an internal amplifier today. V-Drive is a great option when you're adding an amp and sub, but don't have the room (or the inclination) to amplify your full-range speakers.

Important Note: The powerful output of Alpine's V-Drive internal amplifier requires a direct fused connection to your vehicle's battery! We recommend that you purchase a 10-gauge amp wiring kit with this receiver.

(this has a power booster and can “get” slugged down if all 4-channels are going)

(the output is into 4-ohms… not 2-ohms)


Finally, for those who would like to see a taste of things to come:

http://focus.ti.com/docs/prod/produc...Number=TAS5000

http://www-s.ti.com/sc/psheets/slaa117a/slaa117a.pdf

See 3.1.1 Requirements for Power Supply

25-watts/channel being available at 2-ohms with 13.3 volts supplied
20-watts/channel being available at 4-ohms with 15.4 volts supplied

At 3 bucks a chip with high-efficiency… well, you get what you pay for…

EricL

Yes, there is something to this...

If you want to burn up a ton of power, but want zero cross-over distortion, just go with a class-A amp.

BTW -- if you like that stuff, Yamaha had a Mosfet amp that came out for a short time with vacuum tube triode characteristics. (the mosfets were specially designed by them to emulate Triode power tubes used to drive 8-ohm speakers...)

If you have the giant Klipsch corner horns, about 10-watts will drive the natives insane -- they are rather effecient. Their impediance changes just by dropping them into the folded horn (yep!).

As far as going too far with the high power being a bad think -- it depends (there is some of the stuff that gets a bit "strange" for my experience)...

There are also concerns that regard the "distortion" with length of throw, and there is a lot to say for some of the high efficiency systems. (It all depends...)


I wonder how many people know that:

3 watts into 8 ohms is about 1-volt!
12 watts into 8 ohms is about 12-volts...
50 watts into 8 ohms is about 20-volts..


The tri-amp studio stuff would get around (and depending on who wanted to never hear again):

100w tweeters
200w midrange
400w base

for each channel

(and that was enough to do army crowd control experiments...)

CLSmike

Thanks for all the info its really helpful.... I orderd (2) Alpine 12 inch Type S speakers and im gonna run it on my Boss 650 amp and the speakers are 4 ohm speakers with single voice coil.


Thanks.