ohms

[elraido]

Ok, I sound like a noob here but what exactly is an ohm and how does it effect sound quality etc. I know that most home theater speakers and receivers are 8 ohms and a lot of car audio is 4 ohms or lower. Also how do you wire for a specific ohm?

 

[CSVT_2004]

Read the 1st section of the Basic Installer book from MECP one idea, but that costs about $20..... so I'll do what I can for you....

Ohms is a measure of resistance which it seems like you sort of already know... Most HT systems are 8ohm, known as high impedance speakers, MOST car audio speakers are 4 ohms, some factory systems are 1 ohm speakers and some subs of course are 2, 4, dual 2, or dual 4 for the most part. The most basic thing to know about ohms is how to put them together, which there are 2 ways of doing so, series and parallel. when speakers are hooked in series you go + to - to + to -, and this style of hookup your resistance values are added together so Rtotal = R1 + R2 + R3......, the other way is by taking all of your +'s and -'s and combing them. Knows as Parallel, the computation for parallel is a little more crazy... 1 / R = 1 / R1 + 1 / R2 + 1 / R3 +... Usually series and parallel are use more for doing subs IMO than for interior speakers. I guess one other thing would be normally you notice an almost doubling in speaker output for every halving of resistance, for example, an amp I'm looking at puts out 500w x 1 @4 ohms, and it outputs 900w x 1 @ 2ohm, so halving the resistance almost doubles output at the amp that is... if you were to hook up an 8 ohm speaker, you'd probably only see about 200 or 300 watts output i'm guessing...

If someone wants to correct me go ahead, Some of this is things i've heard talking with other installers, most of it though is text book knowledge...

 

[yamaha racer 686]

you did a good job but im going to put insight on the dual 2 ohlms or dual 4 ohlm subs. edesigns.com has great info and videos to help you out. but what i can say is with a dual input sub you can get ether twice the resistance or half with just one sub. so say the amp puts out 100amps at 8ohlms 200 at 4 ohlms 400 at 2ohlms and 800 at 1 ohlm.

first set up is with a dual 2 ohlm sub. using one input would give you 2 ohlms resistance. by series or parellel you are able to either double resistance to 4 ohlms or divide it down to 1 ohlm. meaning you can run anywhere from "800 to 200rms on said sub.

Second using dual 4 ohlm sub. same thing applys going to 8 ohlms or 2 ohlms.

dual inputs just give you more of a selection on how to wire your sub to your amp.

i think im about right?? correct me if im wrong

 

[SoundQ SVT]

Ok, I sound like a noob here but what exactly is an ohm...

http://en.wikipedia.org/wiki/Ohm
http://en.wikipedia.org/wiki/Ohm's_law

...and how does it effect sound quality etc.

An ohm does not affect sound quality. It is simply a measure of electrical impedance/resistance. What that resistance does to the source of power being resisted (the amplifier) will affect the sound you hear from a speaker. Also, do not assume that a stated, or nominal, impedence of 4 ohms (for example) on a speaker indicates that it provides a constant resistance no matter what it is reproducing. A speaker is a dynamic load, therefore, the impedance changes continuously depending on the frequency being played. This impedence curve by frequency does have a big impact on the sound you will hear coming from the speaker. This impedence curve by frequency could also be very different for the same speaker mounted into two different types of enclosures. So not only does the impedence curve affect the sound, but so does the enclosure the speaker is in.

Unfortunately the topic of impedence/resistance, which is measured in ohms, and its impact on sound quality is quite sizable and would be difficult to cover fully here. If you are really serious about wanting to learn this topic, then I suggest reading from more authoritative sources than those of us on this forum, myself included.

I know that most home theater speakers and receivers are 8 ohms and a lot of car audio is 4 ohms or lower. Also how do you wire for a specific ohm?

Home audio speakers tend to be in the 6 to 8 ohm range, which just happens to be the resistance range that home audio amplifiers like to run power into. (that was sarcasm... )

Aftermarket car audio components tend to center on 4 ohm devices, but it is not unheard of to see anything from 2-8 ohm resistance levels on speakers. Some of the higher current amplifiers can power speakers that provide 2 or even 1 ohm of resistance.

I could go on, but I need to get back to work....

 

[96Mystique]

There's no need to go out and buy the MECP study guide, unless you plan on becoming an installer. Do some reading on Bcae1.com, and you should be good to go on the more basic (and some more technical) parts of car audio.

 

[CSVT_2004]

There's no need to go out and buy the MECP study guide, unless you plan on becoming an installer. Do some reading on Bcae1.com, and you should be good to go on the more basic (and some more technical) parts of car audio.

Just because it's from a certification, doesn't mean that it's not a great source of car audio knowledge in that book... I'd say its worth it, espically if you have a job that will pay for you to take the test, otherwise besides Bcae1.com, I think the12volt.com is better..... IMO

 

[fordsvt98]

Also how do you wire for a specific ohm?

You should know that when you twist + and - speaker leads from two subwoofers together, the ohm impedance will be cut in half. Thats one way to wire for a specific ohm.

So if you did that with two single voice coil 4 ohm subs, the amplifier would see a 2 ohm load.

You can also raise ohms wiring + to - on the other sub, and then take the other terminals and wiring those left over to the amp, you would raise them to 8 ohms.

There are alot of variables when talking about wiring specific ohms.

for instance dual voice coils and single voice coil subs.

Heres a cool guide to use if youre ever in doubt....

http://www.rockfordfosgate.com/rftech/woofer_wizard.asp

 

[CSVT_2004]

You should know that when you twist + and - speaker leads from two subwoofers together, the ohm impedance will be cut in half. Thats one way to wire for a specific ohm.

So if you did that with two single voice coil 4 ohm subs, the amplifier would see a 2 ohm load.

You can also raise ohms wiring + to - on the other sub, and then take the other terminals and wiring those left over to the amp, you would raise them to 8 ohms.

There are alot of variables when talking about wiring specific ohms.

for instance dual voice coils and single voice coil subs.

Heres a cool guide to use if youre ever in doubt....

http://www.rockfordfosgate.com/rftech/woofer_wizard.asp

Love that page!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! When I was first doing subs I woudl use that when I got stuck...

 

[Teal4Banger]

This may have been mentioned in detail, but I'll over simplify here:

In regards to speakers:

ohms is impedance (not resistance)

higher ohms give more control over the speaker for (ususally) better sound

lower ohms allow more power to go to the speaker allowing more volume

general (full range) speakers usually have 8 ohms for this purpose

 

[Steeda...]

higher ohms give more control over the speaker for (ususally) better sound

lower ohms allow more power to go to the speaker allowing more volume

general (full range) speakers usually have 8 ohms for this purpose

Please explain I guess I don't understand?

 

[Ray]

wow.. I wish I'd have seen this thread earlier..

that's okay.I got in on this one just in time... I'm waiting to understand this theory, too.

I'm not making the connection here, even in LAYMAN'S TERMS, about how impedance has any "control" over "more quality"??? Maybe.. (just maybe) I'm an electronics idiot, but I was always under the (uneducated??) impression that impedance had nothing to do with "control" over "more quality" and was more a measure of the internal makeup of coils/wiring and was a representation of the amount of effort it would take to overcome that particular build...

less wasn't more volume, more wasn't "more quality".. but what do I know.. I'll be waiting in the back row there...




















I was just a nuclear electronics technician for the US Navy specializing in High Frequency systems, power amplifiers, and radar theory, with a miniature and micro-miniature soldering rate. Not to mention basic electronics theory, digital/analog theory, transistor theory, and PCB interference/construction engineering training.

 

[Steeda...]

I would love to know too. Granted I don't know much about electronics...

B-2A Stealth bomber Electronic Warfare journey man
MECP First class installer
Avionics and Electronics Degrees
ohh and
Electromagnetic Compatibility Test Technician specializing in RF Radation

 

[dnewma04]

I would be willing to bet he will be referencing an amplifiers damping factor. Damping factor is a ratio of the output impedance of the amplifier to the impedance of the speaker (wire+crossover+drivers). High damping factor amps do have more "control" over a speaker than a low damping factor amp.

However, in reality, the damping factor is a highly overrated specification because by the time everything is considered, the effective damping factors of amps are all very similar. An amp claiming 500 for a damping factor will not be significantly different performing than an amp with a damping factor of 20.

I guess my point in a nutshell is that a high impedance speaker can (all else being equal) be negligibly better than a lower impedance speaker. But there are MUCH more important spefications than impedance that it can be almost completely ignored.

Also, there are some amps that do have measurable differences in THD at different impedances, but hopefully everyone understands that THD and IMD in an amplifier have absolutely no correlation to sound quality.

 

[dnewma04]

I would love to know too. Granted I don't know much about electronics...

B-2A Stealth bomber Electronic Warfare journey man
MECP First class installer
Avionics and Electronics Degrees
ohh and
Electromagnetic Compatibility Test Technician specializing in RF Radation

See, thats what I've been saying all along but no one would listen...

Nice little rainbow...

 

[Steeda...]

HAHAHAHA!