[Joseph L]

I'm new to site and decided that this would be the best place to ask, because in my independent research your forum came up the most, but I have yet to find a direct answer to this question.


I have some basic electrical engineering knowledge, so I understand amps, volts, and ohms, and I understand the idea that 4 ohm speakers require a receiver or amplifier that can deliver more amps, while 8 ohm speakers are more common because they are easier to drive. What I don't understand is why 6 ohm speakers are not more common. It seems like almost everything out there is 8 ohm or 4 ohm, and you would think that with all the debate between whether to go with 4 or 8, a 6 ohm speaker would be a good compromise between the two.


I'm sure many of you can give me lots of reasons why most manufacturers go with 8 ohms, but if 8 ohms are so much more ideal than 6 ohms, then why even bother with 4 ohms? Why are 8 and 4 the most common with 6 overlooked? Am I wrong in thinking that 6 ohms is a good compromise? What am I missing here?

 

[Bill Fitzmaurice]



Quote:
Originally Posted by Joseph L  /t/1468048/why-arent-6-ohm-speakers-more-common#post_23197926


What am I missing here?

Manufacturers make mostly 8 ohm drivers. Two may be parallel wired for a 4 ohm load; that's the most common 4 ohm configuration. And while 4 ohm drivers are often used singly they're also used in pairs series wired if a two driver 8 ohm configuration is desired. 6 ohm drivers are rare as there's no need for them.

 

[Joseph L]

I'm not convinced that there's no need for them, particularly if 6 ohm speakers are a good compromise between 8 ohm and 4 ohm. In a 3-way speaker, could two be run in parallel and then in series with the third to achieve 6 ohms? Some may say that this is not necessary as a 2-way is good enough in high-quality speakers, and that 3-way speakers are made from cheap parts with weird responses to fill in the gaps. I don't quite buy that. A manufacturer could build a 3-way speaker with good parts to get perfect range across the board, and it would be 6 ohm. I still don't see why a 6 ohm speaker is not a good compromise.

 

[RicardoJoa]

Ohm are not a fix thing. The swing up and down from the Frequency range.

 

[Joseph L]

Yes, I'm aware of that, but that doesn't answer, or change, my question. When I say 8 ohm, 6 ohm, or 4 ohm, I of course mean rated at 8 ohm, 6 ohm, or 4 ohm. We could have a whole different discussion about how manufacturer's rate them and how meaningful their ratings are, but that's for another topic. It doesn't get to the heart of my question.


Or, are you implying that many speakers could more accurately be described as 6 ohm but manufacturer's round off to 4 or 8 because 6 is sort of non-standard?

 

[RicardoJoa]

What compromise are talking about between 4,6,8 ohm? Unless the amp cant handle the low impedance, i see no diference in ohm rating. In a way, the actuall impedance response in more important.

 

[Joseph L]

If I understand correctly, the compromise between 4 ohm and 8 ohm speakers is that 4 ohm speakers can get about 3dB louder if your amp can put out enough power to drive them to their full potential, while 8 ohm speakers are much easier on your amp, but will be about 3dB quieter. I understand that impedance response, wattage, and frequency response can all play a factor as well, but apples to apples, that's the trade-off. It seems logical then, at least to me, that 6 ohm speakers would be the best compromise between these two trade-offs. This is why I am wondering why 6 ohm speakers are not more common. I apologize if I was unclear about this in my original post. So, what's wrong with 6 ohm speakers?

 

[RicardoJoa]



Quote:
Originally Posted by Joseph L  /t/1468048/why-arent-6-ohm-speakers-more-common#post_23198486


If I understand correctly, the compromise between 4 ohm and 8 ohm speakers is that 4 ohm speakers can get about 3dB louder if your amp can put out enough power to drive them to their full potential, while 8 ohm speakers are much easier on your amp, but will be about 3dB quieter. I understand that impedance response, wattage, and frequency response can all play a factor as well, but apples to apples, that's the trade-off. It seems logical then, at least to me, that 6 ohm speakers would be the best compromise between these two trade-offs. This is why I am wondering why 6 ohm speakers are not more common. I apologize if I was unclear about this in my original post. So, what's wrong with 6 ohm speakers?

Unless you are comparing apples to apples, but how often do you find comparison between two same thing?

Which speaker would be louder? A speaker rated 4 ohm 85 db/2.83 vs speaker B rated at 8 ohm 95 db/2.83?

 

[Joseph L]

Judging by your responses, it's clear that you are of the opinion that impedance really does not matter. In other words, you would go with the last poll option. However, you still haven't answered my question.

 

[Joseph L]



Quote:
Originally Posted by Bill Fitzmaurice  /t/1468048/why-arent-6-ohm-speakers-more-common#post_23197961


Manufacturers make mostly 8 ohm drivers. Two may be parallel wired for a 4 ohm load; that's the most common 4 ohm configuration. And while 4 ohm drivers are often used singly they're also used in pairs series wired if a two driver 8 ohm configuration is desired. 6 ohm drivers are rare as there's no need for them.

In hindsight, this answer will suffice. I guess what you're trying to say is that the difference between 4 ohm and 8 ohm speakers is so small that a compromise is not needed? That makes sense. There's no need to do a bunch of weird serial/parallel combinations to get them to be 6 ohms, but if the speakers are wired in a weird way that makes them 6 ohms it doesn't hurt anything either. Am I understanding this correctly? I guess I just thought 6 ohm would be more common.

 

[RicardoJoa]



Quote:
Originally Posted by Joseph L  /t/1468048/why-arent-6-ohm-speakers-more-common#post_23198579


Judging by your responses, it's clear that you are of the opinion that impedance really does not matter. In other words, you would go with the last poll option. However, you still haven't answered my question.

Impedance matters when you are talking about how the amp or AVR will handle, not because 4 ohm speaker are better or they draw more current then an 8 ohm when you are comparing apples to orange.

With your analogy, what happens when you have a amp that can only handle 8 rating? Will your 4 ohm speaker still be better. No, you will overload your amp.

If 4 ohm speakers are better then all car audio would all be better the home speakers.

 

[RicardoJoa]



Quote:
Originally Posted by Joseph L  /t/1468048/why-arent-6-ohm-speakers-more-common#post_23198583


In hindsight, this answer will suffice. I guess what you're trying to say is that the difference between 4 ohm and 8 ohm speakers is so small that a compromise is not needed? That makes sense. There's no need to do a bunch of weird serial/parallel combinations to get them to be 6 ohms, but if the speakers are wired in a weird way that makes them 6 ohms it doesn't hurt anything either. Am I understanding this correctly? I guess I just thought 6 ohm would be more common.

Bill is talking about Speaker driver and it seems you are talking speakers. Not sure what compromise you are talking about unless drawing more current has some advatage.

 

[commsysman]

To find the actual impedance of a speaker, you have to look at its frequency vs impedance curve.


A typical "8 ohm" speaker will have frequencies where its impedance drops to 5 or 6 ohms and some frequencies where it rises to 10 or even 15 ohms or more.


When a speaker is designated as 4 ohms or 8 ohms, that is only a rough approximation of its AVERAGE impedance and may be misleading.


It would be more meaningful if the manufacturer gave the MINIMUM impedance of the speaker and the frequency at which this applies.


It is not uncommon to look at the actual impedance graph of an "8 ohm" speaker and find that the impedance actually drops to less than 4 ohms at some frequencies.


In that case it should really be thought of as a 4 ohm speaker when choosing an amplifier to drive it.

 

[Bill Fitzmaurice]



Quote:
Originally Posted by Joseph L  /t/1468048/why-arent-6-ohm-speakers-more-common#post_23198486


If I understand correctly, the compromise between 4 ohm and 8 ohm speakers is that 4 ohm speakers can get about 3dB louder if your amp can put out enough power to drive them to their full potential, while 8 ohm speakers are much easier on your amp, but will be about 3dB quieter.

That's not the case. The impedance of the speaker isn't what limits how loud it will go, that's determined by the driver excursion. There is no correlation between impedance and excursion. If a 4 ohm and 8 ohm driver have the same excursion and both are driven to that full excursion they will be equally loud.

4 ohm drivers are 3dB more sensitive for equal voltage input at low signal levels. That can be of some value if the users amp is particularly weak, but not a lot of value. If the amp is pushed to full undistorted output it will only run 2dB louder into a 4 ohm load versus 8 ohms, and again, that 2dB would only be realized if the driver excursion limit had not been reached.

This points out that there's limited benefit to having both 4 and 8 ohm speakers, and even less to having 6 ohm as well.

 

[Joseph L]

I think I get the idea now. I assumed there were benefits and drawbacks to each, just like there's a compromise between sealed vs ported, paper vs poly, 2-way vs 3-way, etc, and that's where I was wrong. It seems knowing the impedance of your speakers is only important for making sure your amp can drive them and knowing what sort of output you're going to get. Understanding that the advertised impedance is just an average and that actual impedance varies a lot, the consensus seems to be that "well-behaved" speakers are the better way to go. That being said, do you have an ideal range that you like to see in your speakers/drivers? Why do you think manufacturers just go with an average instead of advertising a range like they do with frequency?

 

[russ_777]

There are several ways to answer your question...


I think the most basic one is way back when speaker mfgs started rating th enominalimpedance of their speakers the industry seemed to gravitate towards either 4, 8 or 16 ohms. If you will, a low, medium and high. So trying to split the difference between 4 & 8 didn't make much sense.


As others have noted, if you have a lick of sense, you will not rely solely on a speaker's nominal rating if you intend to play it loud in a big room and if it is inefficient. You don't get close to ground truth until you look at the impedance curves....both magnitude and phase, and then compare to test results showing how stable the amplifiers you're considering when driving speakers with worst case conditions.... IZI

Most AVRs are suspect when trying to do the above....most separate PAs are not. What you want to look for in a PA is one that comes close to "doubling down" its power output into 4 and 2 ohm test loads.


Considering all of that, whether a speaker is rated a 8 or 6 ohms nominal impedance tells you about as much useful information as saying a car has a maximum stopping distance of 70 feet but not specifying from what speed.