4ohm 8ohm.???

[spoolnaround]

I did a little research here but I dont understand the difference in speakers. Arent car speakers supposed to be 4 ohm? My neighbor bought a set of marine speakers for his deck boat and they are 8ohm. He isnt running an amp or anything, will they work? What is the difference? Someone school me

 

[cdoggwsu]

Ohms are just a rating of the amount of resistance the speaker will create when introduced to the circuit. Circuits need a certain amount of resistance otherwise you would have a short (things get hot, burning and melting ensues). Speakers are rated on the resistance that is created by the voice coil (the electromagnet or big heavy part on the back of your speakers) or multiple voice coils as the case may be.

As resistance drops, current and voltage increase (wattage being a function of all three), however that's not necessarily a good thing. Most stereo amplifiers (including amps built into the deck) are stable from 4 ohms up to around 16 I believe. Below that can cause parts to get too hot and fail and above that sound output is too diminished. Manufacturers usually rate at their most efficient so if they say "100 watts at 4 ohms" that means if you hooked up a 4 ohm speaker you would get 100 watts of power. It would follow then, that if you hooked up an 8 ohm load to the same line you would get "50 watts at 8 ohms" Keep in mind that even though it's only 1/2 of the effective wattage the difference will be fairly negligible. You won't lose 1/2 of your sound output.

Anyway, sorry if that doesn't make any sense. It's been quite a few years since i've studied electrical theory. If you really want to see it, check out Ohm's Law. If you're interested, look into calculating watts as well and you can see how arbitrarily ridiculous the numbers are when the manufacturers cram them down our throats.

 

[spoolnaround]

Ohms are just a rating of the amount of resistance the speaker will create when introduced to the circuit. Circuits need a certain amount of resistance otherwise you would have a short (things get hot, burning and melting ensues). Speakers are rated on the resistance that is created by the voice coil (the electromagnet or big heavy part on the back of your speakers) or multiple voice coils as the case may be.

As resistance drops, current and voltage increase (wattage being a function of all three), however that's not necessarily a good thing. Most stereo amplifiers (including amps built into the deck) are stable from 4 ohms up to around 16 I believe. Below that can cause parts to get too hot and fail and above that sound output is too diminished. Manufacturers usually rate at their most efficient so if they say "100 watts at 4 ohms" that means if you hooked up a 4 ohm speaker you would get 100 watts of power. It would follow then, that if you hooked up an 8 ohm load to the same line you would get "50 watts at 8 ohms" Keep in mind that even though it's only 1/2 of the effective wattage the difference will be fairly negligible. You won't lose 1/2 of your sound output.

Anyway, sorry if that doesn't make any sense. It's been quite a few years since i've studied electrical theory. If you really want to see it, check out Ohm's Law. If you're interested, look into calculating watts as well and you can see how arbitrarily ridiculous the numbers are when the manufacturers cram them down our throats.

So there is really no problem running an 8 ohm speaker with a 4ohm deck, right?

 

[cdoggwsu]

Yeah you are pretty safe running an 8 ohm speaker with any car audio stuff.

 

[joshthemule]

Speakers are set at a certain resistance (4ohms, 8ohms, 16, 32 etc) in order to accommodate the wiring scenario. If the goal is to run at 4 ohms to achieve the best efficiency of you amplifier, you can wire two 8ohms speakers in parallel and the overall resistance will be 4 ohms. You might find a 2 ohm sub woofer that is meant to be wired in series with another 2 ohm woofer to achieve 4 ohms. IF wired in parallel, divided the resistance by the number of components (speakers in this case). If wired in series, multiply the resistance be the number of components. To answer your question, they will work fine.

 

[chevyin]

Running a pair of 8ohm speakers off deck power wont yield much output.

 

[jonrpick]

Speakers are set at a certain resistance (4ohms, 8ohms, 16, 32 etc) in order to accommodate the wiring scenario. If the goal is to run at 4 ohms to achieve the best efficiency of you amplifier, you can wire two 8ohms speakers in parallel and the overall resistance will be 4 ohms. You might find a 2 ohm sub woofer that is meant to be wired in series with another 2 ohm woofer to achieve 4 ohms. IF wired in parallel, divided the resistance by the number of components (speakers in this case). If wired in series, multiply the resistance be the number of components. To answer your question, they will work fine.

It's a little more complicated than that... That works IF and only IF the components are of the same resistance.

The formula goes like this:

1
-------------------
(1/r1) + (1/r2)

"R" meaning "resistor", or in this case speaker.

For example, say you've got two 8 ohm speakers...

1 / ((1/8) + (1/8)) = 4 ohms

1 / 8 = .25
+ 1 / 8 = .25
-------------------
.50

1 / .50 = 4 ohms

Yep... it works.


But with say, a 16 ohm speaker, and a 4 ohm speaker...

1 / ((1/16) + (1/4)) = 3.2 ohms



Add a 3rd speaker...

1
------------------------------
(1/r1) + (1/r2) + (1/r3)

We'll use 8 ohm speakers for this example.

1 / ((1/8) +(1/8) +(1/8)) = 2.667 ohms

It still works IF the components are all of the same impedance (ohms). 8 / 3 DOES equal 2.667 ohms, so you can simply divide the ohms by the number of components. But not always...

I realize for the purpose of car audio (and specifically this thread) most folks won't be mixing and matching resistance values with speakers, but I've seen some pretty ghetto-fabulous stuff before in some people's rides. I was even guilty of installing such a system in a friend's VW bug when I was 14 or 15...

 

[readymix]

I was just about to post that same info.

 

[chevyin]

In all fairness, Id never recommend paralleling speakers together that are not of the same impedance.

 

[jonrpick]

In all fairness, Id never recommend paralleling speakers together that are not of the same impedance.

I may end up doing it intentionally on one of my guitar amps. It expects a 3.2 ohm load (that's where I got that number in the earlier example). One company can custom wind certain models to 3.2 ohms, but this will be a 2-speaker setup, and the only way is to have two in parallel, at 4 and 16 ohms each (to my knowledge, they don't wind them in 6.4 ohms).

 

[chevyin]

I may end up doing it intentionally on one of my guitar amps. It expects a 3.2 ohm load (that's where I got that number in the earlier example). One company can custom wind certain models to 3.2 ohms, but this will be a 2-speaker setup, and the only way is to have two in parallel, at 4 and 16 ohms each (to my knowledge, they don't wind them in 6.4 ohms).

You want a 3.2 ohm final impedance, correct? With two speakers you can achieve this by having two 1.5ohm coils in parallel, or two 6ohm coils in series. DVC's would make for four vc's, giving you abit more options.

If they will custom wire to 3.2 ohms for each coil (not what you need), why cant they do 6ohms? The problem is, if you have two speakers in parallel, one with a 4ohm impedance, and one with a 16ohm impedance, yes you will achieve a 3.2ohm final load. But, the power will not be dispersed evenly between the drivers. The 4ohm speaker will receive 4x the amount of power the 16ohm speaker does. If it was a 100 watt amplifier for example, one speaker would receive 20 watts while the other sees 80 watts. Obviously this would lead to power handling problems, as well as imbalanced output between the two speakers. This is why I say its generally best not to wire speakers of different impedances together.

 

[jonrpick]

You want a 3.2 ohm final impedance, correct? With two speakers you can achieve this by having two 1.5ohm coils in parallel, or two 6ohm coils in series. DVC's would make for four vc's, giving you abit more options.

If they will custom wire to 3.2 ohms for each coil (not what you need), why cant they do 6ohms? The problem is, if you have two speakers in parallel, one with a 4ohm impedance, and one with a 16ohm impedance, yes you will achieve a 3.2ohm final load. But, the power will not be dispersed evenly between the drivers. The 4ohm speaker will receive 4x the amount of power the 16ohm speaker does. If it was a 100 watt amplifier for example, one speaker would receive 20 watts while the other sees 80 watts. Obviously this would lead to power handling problems, as well as imbalanced output between the two speakers. This is why I say its generally best not to wire speakers of different impedances together.

True, however I plan on mixing two different speakers together (with different magnets and efficiencies) to get an overall sound.

To my knowledge the company already has the voice coils wound, but I have considered asking for something custom.

The only other option is to change the output transformer in the amplifier to one with multiple taps for 4, 8 and 16 ohms and run standard speakers.

Damn Fender and their weird ways of doing things...

 

[chevyin]

True, however I plan on mixing two different speakers together (with different magnets and efficiencies) to get an overall sound.

To my knowledge the company already has the voice coils wound, but I have considered asking for something custom.

The only other option is to change the output transformer in the amplifier to one with multiple taps for 4, 8 and 16 ohms and run standard speakers.

Damn Fender and their weird ways of doing things...

Yes, if you are playing with different drivers, and matching efficiencies, it can work. But it leaves me wondering why you want two different speakers reproducing the same freq band.

Sounds like you have your hands full with this project, good luck.

 

[jonrpick]

Yes, if you are playing with different drivers, and matching efficiencies, it can work. But it leaves me wondering why you want two different speakers reproducing the same freq band.

Sounds like you have your hands full with this project, good luck.

Guitar speakers are a different breed. Lots of guys, for instance, like Celestion Greenbacks (25W speakers) because they break up when overdriven. It's a specific sound that can't be had any other way than by pushing the speaker to the point of physical distortion of the cone.

I'm planning to run two speakers, one with an Alnico (Aluminum / Nickel / Cobalt) magnet and another with a ceramic magnet. Ceramics are tighter, but harsher on the treble. Alnicos are smoother up top, not so tight on the bottom end. It's a fairly common practice. Each will emphasize a frequency band better than the other, and the right combo will end up producing a really nice sound out of one cabinet.

Here's what I'm reproducing, but on a really small scale:

http://www.geocities.jp/beatcruise/showman03.jpg

That's an 85W tube amp with a single 15" JBL speaker. Mine will be a much smaller 6.5W amp with two 10's. Very portable. It was originally loaded with one 8", and the amp and speaker are one cabinet (a "combo" amp), and now the amp guts are in a single 12" cab... MUCH better frequency response, and obviously extended bass response. But I like the old stacks, and having the two 10's in a separate cabinet would look super cool, and have a neat tone.

Also, these amps often don't use sealed cabinets. The "bass" response on the speakers themselves are often flat only down to 75Hz... like I said, the guitar speakers are a different breed than your typical audio speakers.

 

[chevyin]

Interesting. That definitely flies in the face of traditional speaker building methods. Generally speaking, you do not want two different speakers attempting to reproduce the same freqs, be it with them emphasizing different characteristics or not. Most people would recommend an active xover network that would allow the speakers you want to play the lower freqs to only play those freqs, while the other speaker is dedicated only to those highs they excel at.

Cheers.

 

[jonrpick]

Interesting. That definitely flies in the face of traditional speaker building methods. Generally speaking, you do not want two different speakers attempting to reproduce the same freqs, be it with them emphasizing different characteristics or not. Most people would recommend an active xover network that would allow the speakers you want to play the lower freqs to only play those freqs, while the other speaker is dedicated only to those highs they excel at.

Cheers.

Yeah, "hi-fi" sound is definitely not pleasing to the ears when it comes to guitar amplification. The most popular sounds are 30-40 year old amps.