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6-ohm speakers. Why?

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Old 04-03-2014, 11:02 PM   #1  
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Default 6-ohm speakers. Why?

I've perused many pages of the threads in this forum but haven't found one that discussed this topic. There may be one around, though, so if you are familiar seeing/reading one, please provide a link.

First, I do not not have any diagnostic equipment to measure what the effect might be replacing an 8-ohm speaker configuration with a 6-ohm one so it would only be my own ear to detect the difference(s).

Electrically, I am assuming that the wire itself will be conducting more amperage so would expect the temperature of the cable itself (and perhaps the amp as well?) would rise some amount with the reduced impedance. Whether this amount is enough to cause a detrimental effect on the components themselves, I have no way of knowing.

More importantly is the listening experience itself and I am as much in the dark as to the consequences of changing the impedance by 25% on the ear. I have read during my travels that I would need a power increase of at least that much (~25%, or at least 125wpc RMS) to realize the same performance that existed with the 8-ohm speakers that are being replaced. The 6-ohm speakers are rated at 120w, replacing the 8-ohm 100w pair. Not sure how much that rating difference matters, so assume that I have found a 6-ohm pair rated at the same (100w) level.

In this case, I am using a receiver that claims to deliver 100wpc min RMS @8 ohms. The dynamic ratings vary according to impedance as: 2 x 140wpc @ 8ohms, 2 x 135wpc @ 4ohms (this rating makes no sense to me, expecting a value more around 155wpc... perhaps a misprint in the manual? dunno), 2 x 170wpc @ 2 ohms. The dynamic ratings mean nothing to me since, in the past, I have only ever matched amp/speaker using the RMS output (possibly short-sighted on my part but the technicalities are beyond my own knowledge anyway).

So... What should I be likely to expect from the change in speaker impedance from 8-ohm to 6-ohm?
  • A different frequency distribution, possibly requiring adding an equalizer to compensate? (BTW, I never had an equalizer with this rig.)
  • An overall drop in delivered output at the speaker itself at the same volume setting?
  • A more severe/pronounced impedance fluctuation over the entire frequency range?
  • A noticeable distortion or general decrease in performance at higher volume settings?
  • (All or some of the above)
  • Or "other" characteristics?

I suppose I am simply confused why any manufacturer would design and sell a 6-ohm speaker when 8-ohm have been established as a standard for at least 30 years of which I am aware. Unless I am informed otherwise, I must assume it is done just to confuse consumers like myself, shopping for speaker replacements.

I have read one thread in this forum about a comparison of an 8-ohm vs. a 4-ohm system which I was attempting to extrapolate for this discussion but not knowing if it really applies. I'd rather not get into another 4-ohm discussion though, unless it is used to simulate some common point.

At this writing, I am not situated to upgrade my current amp though I suppose it wouldn't be a bad undertaking, considering that power consumption of contemporary components seems to have increased since I began configuring sound systems, ancient as it is. But I would like to form some sort of target power capacity for that eventuality and any input towards that end would be greatly appreciated. [Please refrain from furnishing suitable replacement amp/receiver component links as understanding the dynamics is the most helpful method to make an effective purchase.]

Thank you for your kind indulgence, folks.
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Old 04-04-2014, 07:42 AM   #2  
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A lot of individual speaker drivers are actually not 8 ohms in speaker systems (when I say speaker systems I am referring to a speaker cabinet with multiple drivers, such as a woofer, a midrange and a tweeter) that include a crossover that uses a choke in series with the driversr since the crossover will add some impedance. You really did not give us enough information to be able to get down into the weeds to answer your question.

If you are dealing with a solid state amplifier (you did not specify) the importance of impedance matching is not nearly as important as it once was when dealing with tube output amplifiers. The fact that your amp specs power ratings for different loads tells me that you probably have a solid state amplifier, although there were tube amps that had multiple taps for impedance matching.

The impedance of speakers when dealing with solid state amplifiers will have very little to do with the sound output quality, but rather the amount of power required for any given db sound level. Unless you run at full volume you should not notice a quality difference if the speaker system is 6 ohm. What will matter is the quality of the speaker system itself and generally speaking any speaker system that is rated at 6 ohms will be part of a complete system such as a home theater in a box (HTIB) system and will generally be of lower quality. Bose is known to have some weird impedance speakers, for example.

As far as any increase in temperature goes, it should not be a problem since your amp specs loads down to 2 ohms.

That is a thumbnail response without having specifics of the amplifier and speakers you are using.
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Old 04-04-2014, 09:03 AM   #3  
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Quote:
So... What should I be likely to expect from the change in speake
r impedance from 8-ohm to 6-ohm?
one thing is increased power to the speaker. Most amps will increase in power when impedance is dropped.
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Old 04-05-2014, 07:20 AM   #4  
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Originally Posted by leevitalone View Post
r impedance from 8-ohm to 6-ohm?
one thing is increased power to the speaker. Most amps will increase in power when impedance is dropped.
True, but unless the volume is very high, it won't matter to the amp. Also many amps actually have increased damping at lower impedance loads.
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Old 04-07-2014, 02:15 PM   #5  
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I went through this exact thing with Sony in the mid-80's. I bought a new receiver, took it home, hooked up my existing speakers and fired it up to enjoy my new toy. Some hours later I'm perusing the docs and there was a big ominous warning, "This is a 6-ohm system. 8-ohm speakers will burn it up."

Sure enough the op amps fried (at a cost of $500 to repair). So I fired off a letter to Sony asking why they are selling a 6-ohm system in an 8-ohm country? And did they really expect me, or anyone else, to sell our expensive speakers for their receiver?

Their reply was (and I'm paraphrasing), "Some people are just too stupid to own Sony products." When I told them what my credentials were they ceased all communication. The receiver went in the junk and I've never owned a Sony device again (except a Playstation after the wife wouldn't shut up about it).
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Old 04-15-2014, 02:01 AM   #6  
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Default A bit more on this issue

First... thanks for the replies so far. And... apologies for the appearance of "beating around the bush" but since I was searching for general rules of thumb about matching speakers to amp I assumed (incorrectly, apparently) that I didn't need to detail all components to understand those basic tenets. I stand corrected. Let me add that I am revising my sound system by scratch and trying to utilize any components that are reliably serviceable rather than blowing a huge wad on a shiny new single-manufacturer-designed system or junking the existing usable components.

The amp (actually, a receiver, AFAIK around 10 years old): Onkyo TX-8511. Solid state.

The tower speaker pair I have been considering: Yamaha NS-777. These are the 6-ohm guys (cabinet output, not the individual speakers contained therein).

I decided to borrow a friend's Pioneer low-end towers that are also rated 6-ohm just to see if I could detect the difference between the output and that of my ancient Advents (model unidentified, we only ever called them Advents... the muscular 26hx14wx12d 2-way 8-ohm ones with the high-frequency toggle in the back) that finally succumbed to the forces of time and nature after at least 25 years of service. It was not my intent to compare sound quality between the 2 brands, just the relative efficiency of my Onkyo to power them. Testing it (the Pioneers), I noticed that in order to reach a similar normal listening volume (was about 40% maximum w/Advents), I needed to power up to about 50%. So that's just the bare bones dB issue and results really didn't surprise me all that much. I figured I may notice a need for more power even around 50% capacity and suspect a similar reaction with the Yamahas.

What my REAL question is: Why would any company (like Yamaha or Pioneer) even design a 6-ohm cabinet to begin with? I mean... what are they trying to accomplish that a "standard" 8-ohm cabinet will (would) not? Or are they just providing a cabinet that matches the impedance of a 6-ohm amp system (perhaps both the Pioneer and Yamaha examples have been integrated into those HTIB systems rbinck mentioned)? But it still doesn't explain why they would engineer an impedance counter to the plethora of most speaker cabinets (i.e 8-ohm). Black magic I guess. I read no other explanation to this point anywhere... so far.

Anyway... assuming that I do decide to integrate the Yamaha towers, does the impedance of the subwoofer matter? Though I don't own one for my sound system (The Advents' range was adequate without one), I do for my computer sound and in that arrangement both channels feed from the sound card into the sub which then splits off the channels into the higher frequency speakers. I am assuming that this is the way most sound systems integrate the sub (as a "parent" of the "child" towers) though I haven't begun researching them yet. (I wanted to get the impedance consequences understood first before venturing into that arena.)

I am also concerned about driving/balancing an additional set of speakers off the auxiliary speaker hub (one that I have not used up to this point). That would be getting closer to surround sound config. So would the pair of satellite auxs need to match the impedance of the main towers as well?

I expect (if you've read this far) you should be getting the picture now. If all the components' (amp/tower/sub/aux) impedances matched, I'd have no serious concerns beyond (hopefully) choosing the best speakers for my budget... case-closed. But integrating a 6-ohm tower creates issues I have never faced before and never sought to understand.

@straybeat: That sux! But... I suspect you are reading the manuals in detail today. They usually provide every language on the planet, so are typically 5 times thicker than the actual information they provide. I've become suspicious of Sony electronics these days. Seems like when companies decide to diversify the quality of their pioneering technologies suffer dramatically and they become Walmart. What's next? Sony garden tillers?
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Old 04-15-2014, 09:40 AM   #7  
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There may not be a good answer to your original question of why would a speaker not intended to be sold as part of a system be made 6 ohms vs 8 ohms. If there is, I've never heard one. They sell a lot of 4 ohm woofers as well as dual coil 4 ohm woofers for series or parallel hookup of multiple drivers, but many subwoofer amps will accommodate an impedance range of 2-16 ohms.

To your new question of the subwoofer, most people will buy a powered subwoofer where the amp is included in the subwoofer. There are some passive subwoofers still available, but in a true 5.1 sound system there is a separate output for the .1 LFE/subwoofer channel. That is what I would recommend, but since your Onkyo is a 2 channel receiver look for a powered subwoofer that has the high level speaker line connections in addition to the RCA connection.

It may be that in Europe there are different speaker impedance that are popular. I noticed on page 9 in the Onkyo TX-8511 manual that 6 ohms is actually mentioned as a minimum for USA and Canadian models. See: http://www.intl.onkyo.com/downloads/...1_manual_e.pdf

Also I noticed your receiver will be ok with down to 4 ohm speakers as long as only a simgle pair of speakers are attached, like only the A pair.
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Old 04-15-2014, 05:40 PM   #8  
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Default Subwoofer recommendation for the Onkyo

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Originally Posted by rbinck View Post
There may not be a good answer to your original question of why would a speaker not intended to be sold as part of a system be made 6 ohms vs 8 ohms. If there is, I've never heard one. They sell a lot of 4 ohm woofers as well as dual coil 4 ohm woofers for series or parallel hookup of multiple drivers, but many subwoofer amps will accommodate an impedance range of 2-16 ohms.
I am beginning to suspect that a 6Ω offering may be nothing more than a compromised impedance that could be used in either a 4- or 8Ω amp system (besides a designed 6Ω amp system, that is). Noticing that European and Asian impedance specs are biased towards a 4Ω environment could mean that 6Ω speakers may work reasonably well in both extremes (4-8Ω). The ability to manage damping properly may have something to do with the chosen speaker impedance (I believe you may have hinted at this during a previous reply?) but mostly when designing the maximum efficiency of an integrated system like those HTIB offers.
Quote:
To your new question of the subwoofer, most people will buy a powered subwoofer where the amp is included in the subwoofer. There are some passive subwoofers still available, but in a true 5.1 sound system there is a separate output for the .1 LFE/subwoofer channel. That is what I would recommend, but since your Onkyo is a 2 channel receiver look for a powered subwoofer that has the high level speaker line connections in addition to the RCA connection.
So it sounds like (for my current Onkyo system) it would be a set-up similar to the one I described for the computer sound using the RCA to get to the sub which would need to contain terminals/plugs/posts for the 2 stereo channels to branch from. But... where would I output to the sub from the Onkyo? The only open RCA port I see is the Monitor Output (which I've never used before). The only other alternative would be to convert one set of speaker outputs (say the "A" pair) to an RCA jack for the sub. Or am I missing something that should be more obvious?
Quote:
It may be that in Europe there are different speaker impedance that are popular. I noticed on page 9 in the Onkyo TX-8511 manual that 6 ohms is actually mentioned as a minimum for USA and Canadian models. See: ~had to remove URL at this place cuz I haven't posted enough yet and even quotes count ... go figure!~

Also I noticed your receiver will be ok with down to 4 ohm speakers as long as only a simgle pair of speakers are attached, like only the A pair.
Yes. I did notice that as well. And even some other functionality that I never considered like switching the output impedance down and trying the Remote Control gizzy (would need some hardware to use this though). Problem is, if I plan to operate an additional set at Pair B, I won't be able to use both sets simultaneously unless they are all 8Ω (as you have already commented). For the time being, the 2nd set is 35 foot away, toggled on (w/the A pair off) as needed. But going with the 6Ω towers will prevent me from ever using both sets together (at least according to the manual). In that eventuality, I suppose engineering a 5.1 system would be the logical update, but, TBH, digital movies are not that important to me though it would get used by the rest of the household, most likely. ~tagged for wish list ATM.~

The engineered surround sound environment does interest me specifically, though, because listening I can do while still multitasking effectively. Not so with watching a monitor screen. I did notice a thread that had begun listing example movie discs that had been engineered for various versions of surround technology but what about CDs? Is there a label on a CD that defines whether it displays the auxiliary channels for surround speakers to use?

Thanks for your speedy replies and suggestions rbinck!
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Old 04-15-2014, 08:16 PM   #9  
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Originally Posted by Chipster2 View Post

So it sounds like (for my current Onkyo system) it would be a set-up similar to the one I described for the computer sound using the RCA to get to the sub which would need to contain terminals/plugs/posts for the 2 stereo channels to branch from. But... where would I output to the sub from the Onkyo? The only open RCA port I see is the Monitor Output (which I've never used before). The only other alternative would be to convert one set of speaker outputs (say the "A" pair) to an RCA jack for the sub. Or am I missing something that should be more obvious?
If you get a powered sub with speaker and line level inputs you hook up the speaker wires directly to the terminals. Often the subwoofer will have output terminals to attach the towers if you want to wire from the Onk to the sub then from the sub to the speakers. Like this one: http://www.amazon.com/Polk-Audio-10-...ords=subwoofer
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Is there a label on a CD that defines whether it displays the auxiliary channels for surround speakers to use?!
There are not any surround CDs to my knowledge. There are surround DVDs though. Most stereo CDs will add some surround effects when played through a pro-logic surround decoder though.
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