Stereo system impedance?

YanKleber

YanKleber

Retired
Hi,

I am a bit confused about the calculation of stereo system impedance.

I have two pairs of 4 ohms loudspeakers and currently don't have any stereo system (they are idle) but I plan to buy one in the future and would like to connect all the four speakers on it.

Let me know if I am assuming it correctly: if I connect a pair on system 'A' and the other pair on system 'B' I will get a parallel association and therefore will end with a total impedance of 2 ohms, right? I think that it is a too low impedance for mostly of systems, so I am not going for it.

If instead I hook both pairs in the same system (A or B) am I correct to assume that they will be set in series and therefore the total impedance will be 8 ohms?

Thanks!
 
Not if I am reading this correctly:

You have a stereo system with an A & B speaker out, with a selector switch for having 1 pair or the other pair, or both sets of speakers on. Is that what we have?

If you connect 1 pair to the A speaker connection, 1 speaker left and 1 speaker right, this will give you 4 ohms on each output. Then do the same on the B speaker connection.

As long as the amp is suitable for 4 ohms this will work correctly. Assuming this is what you have.

Alan.
 
witzendoz said:
Not if I am reading this correctly:

You have a stereo system with an A & B speaker out, with a selector switch for having 1 pair or the other pair, or both sets of speakers on. Is that what we have?

If you connect 1 pair to the A speaker connection, 1 speaker left and 1 speaker right, this will give you 4 ohms on each output. Then do the same on the B speaker connection.

As long as the amp is suitable for 4 ohms this will work correctly. Assuming this is what you have.

Alan.
Click to expand...

Well, actually it will work anyway.

What I asked is if I was assuming correctly that connecting both speakers pairs together (using only one speaker connection -- 'A' OR 'B') it will make a parallel association and therefore two 4 ohms speakers will summ up a total impedance of 8 ohms.

---------- Update ----------

mdainsd said:
Yes
Click to expand...

Cool, thanks!

:)
 
If you stick the + wire from both speakers into exactly one + hole, and the - wire from both speakers into the corresponding - hole, then they are in parallel, and divide down to 2 Ohms.

In order to get series and sum to 8 Ohms, you plug the + wire of one speaker into the + hole, and the - wire of the other speaker into the corresponding - hole, and connect the other two wires (- of the one and + of the other) together, preferably taped off or wire nutted so that they can't short to anything.
 
ashcat_lt said:
If you stick the + wire from both speakers into exactly one + hole, and the - wire from both speakers into the corresponding - hole, then they are in parallel, and divide down to 2 Ohms.

In order to get series and sum to 8 Ohms, you plug the + wire of one speaker into the + hole, and the - wire of the other speaker into the corresponding - hole, and connect the other two wires (- of the one and + of the other) together, preferably taped off or wire nutted so that they can't short to anything.
Click to expand...

This ^^^^^^, Sorry I assumed it was a hifi type amp with an A & B selector.

Alan.

I found this little calculator for you, LINK
 
We may be experiencing a language glitch...

I replied YES to

If instead I hook both pairs in the same system (A or B) am I correct to assume that they will be set in series and therefore the total impedance will be 8 ohms?

Series resistance is additive, i.e. 4 ohms in series with 4 ohms equals 8 ohms.

Then you responded with:

What I asked is if I was assuming correctly that connecting both speakers pairs together (using only one speaker connection -- 'A' OR 'B') it will make a parallel association and therefore two 4 ohms speakers will summ up a total impedance of 8 ohms.

They WILL NOT equal 8 ohms, They will equal 2 ohms, not good.

Series OK, parallel not so good.
 
First of all you will not find a speaker switching system on a TRULY hi fidelity amplifier. Mr Walker of Quad fame would not even allow a switching headphone jack.

Then, those amps that have switches can use either system, i.e. Speakers A only, Speakers B only and then A and B are in parallel on SOME chassis and series on others. There is usually a stern warning on the amplifier and in the handbook about not using speakers lower than 8 Ohms impedance, which is after all the usual Z for "hi fi" speakers in UK and US. Europe is DIN and uses 4 Ohms.

Lastly. You should NEVER wire speakers with any pretentions to quality in series! Read up on "damping factor".

Dave.
 
ecc83 said:
Lastly. You should NEVER wire speakers with any pretentions to quality in series! Read up on "damping factor".
Click to expand...
I personally said nothing about quality.

I wasn't really sure on the A/B/A+B switch, so I didn't go there.

The key point being that to be in series, the signal must flow through one to the other and then back to the amp.

The rule of thumb I've generally heard is that you're usually safe enough running speakers that are off from the "nominal rating" for the amp by a factor of 2, and beyond that you're asking for trouble. So if the amp specifies 8 Ohms, you can usually get away with anything between 4 and 16. Solid state amps will usually let you slop even further in the upwards direction (they can "drive" an open circuit without exploding, but prefer not to be shorted) whereas tube amps should not go much higher, but might be okay a little lower (they need something connected or they fry!). 2 Ohms is getting into the range that scares me no matter what type of amp it is, though. The "impedance" rating of a speaker is a nominal rating at one specific frequency, and can vary dramatically with varying frequency dependent on several factors both electronic and acoustic. A 4 Ohm speaker by itself can get dangerously close to a short circuit at certain (usually low) frequencies. Parallel that so it's even lower-Z, and...
 
ashcat_lt said:
I personally said nothing about quality.

I wasn't really sure on the A/B/A+B switch, so I didn't go there.

The key point being that to be in series, the signal must flow through one to the other and then back to the amp.

The rule of thumb I've generally heard is that you're usually safe enough running speakers that are off from the "nominal rating" for the amp by a factor of 2, and beyond that you're asking for trouble. So if the amp specifies 8 Ohms, you can usually get away with anything between 4 and 16. Solid state amps will usually let you slop even further in the upwards direction (they can "drive" an open circuit without exploding, but prefer not to be shorted) whereas tube amps should not go much higher, but might be okay a little lower (they need something connected or they fry!). 2 Ohms is getting into the range that scares me no matter what type of amp it is, though. The "impedance" rating of a speaker is a nominal rating at one specific frequency, and can vary dramatically with varying frequency dependent on several factors both electronic and acoustic. A 4 Ohm speaker by itself can get dangerously close to a short circuit at certain (usually low) frequencies. Parallel that so it's even lower-Z, and...
Click to expand...

No Ash' I brought up quality!

The usual regime on amps is that there are 8 speaker terminals two sets for each channel. You cannot know what the internal switching regime is unless the book tells you or you experiment (pulling one speaker will stop the other if in series) .

Solid state amps that can drive sub 4R speakers are almost unheard of in the consumer hi fi market but there are many "pro" jobbies that will do it. These are usually of monstrous power, 500W per chan and up.

This whole issue of "safe loading" of amplifiers is complex and full of caveats and maybes!
Absolute fact: You must NEVER drive a valve amp without a load, i.e. without a speaker or resistive load connected.

You must NEVER drive a sstate amp into a short......
Note the word "drive"? If you leave a valve amp' speaker terms open but don't drive it, no harm. Same if you shorted a tranny amp, if no power, no damage. Between these four "states" is the crux of the matter. If you put a 16R speaker on a valve amp tapped to 4 R and tinkle some tunes in the bedroom, almost certainly fine. If you go and gig with the same setup, chances are you will at the very least blow a valve, fuse and maybe an OP traff. (a valve amp will stand a short almost indefinitely. The anodes will go red under drive and a fuse will probably pop).

In theory transistor amps are just as accommodating. They should drive a very low load R if you keep the wick down but in practice transistors are just too damn fast and a few mSecs of high drive and they punch through....REALLY good sstate designs,Crown, Quad etc, are really bombproof but you can consider that any designer that put a speaker switch on an amp was NOT working at the cutting edge of quality and reliability!

Dave.
 
Why are you making it so confusing? I mentioned the A & B switch because in the original post it said "if I connect a pair on system 'A' and the other pair on system 'B' I will get a parallel association and therefore will end with a total impedance of 2 ohms, right? " so I though we were talking about a switchable amp.

Then we get all this stuff about "First of all you will not find a speaker switching system on a TRULY hi fidelity amplifier. Mr Walker of Quad fame would not even allow a switching headphone jack." While I understand what you mean about real HIFI amps, there are a lot of very good amps with speaker switching. And there was no indication about how high end we are talking.

So lets not go out of our way to confuse the OP about how to connect this. I did not get this at all "The usual regime on amps is that there are 8 speaker terminals two sets for each channel. You cannot know what the internal switching regime is unless the book tells you or you experiment (pulling one speaker will stop the other if in series) . Solid state amps that can drive sub 4R speakers are almost unheard of in the consumer hi fi market but there are many "pro" jobbies that will do it. These are usually of monstrous power, 500W per chan and up." So how is the OP going to get it? Most amps have a + & - terminal for left, and a + & - terminal for right.

Alan.
 
Ok Alan,
Yan said he was looking to buy a system, amp, in the future? He also said that he would like to connect two sets of speakers to the amp.

All I am saying is that there are two different ways that amplifiers (that did speaker switching) arranged things. Some put the two pairs in parallel, others put them in series.
Until we know the exact model of amplifier we cannot know which and clearly an amp that parallels speakers will not do for 4 R loads (or indeed 8+4). One that puts the speakers in series WOULD be safe but no longer "hi-fi!" IMHO.

Sorry for any confusion.

Dave.
 
Sorry - are we talking electronics or snake oil here? Never wire a speaker in series for quality? It's a standard design feature, and hence why drivers are available in different impedance ratings. An amplifier with a poor damping factor really doesn't deserve using!

There's a huge gulf between the hi-fi brigade and recordists and broadcasters. Both camps believe certain things that disagree with each other.

In the pro audio world, nobody cares very much about what goes between the amplifier output terminals and the speaker inputs, as long as it has high enough cross-section and the connectors can handle the current and are reliable. I see no difference between a connector in circuit and a switch. Hi-fi purists disagree. They'd also have you spend huge amounts of money on cable and connectors - Over the years, the BBC's R&D department have published in depth technical papers on all sorts of designs. Until I see them using vast quantities of precious metals in their connectors and using clever cable, I shall stick with their philosophy and forget all the other stuff.
 
ashcat_lt said:
If you stick the + wire from both speakers into exactly one + hole, and the - wire from both speakers into the corresponding - hole, then they are in parallel, and divide down to 2 Ohms.

In order to get series and sum to 8 Ohms, you plug the + wire of one speaker into the + hole, and the - wire of the other speaker into the corresponding - hole, and connect the other two wires (- of the one and + of the other) together, preferably taped off or wire nutted so that they can't short to anything.
Click to expand...

Dang! That's it!

:D
 
ecc83 said:
All I am saying is that there are two different ways that amplifiers (that did speaker switching) arranged things. Some put the two pairs in parallel, others put them in series.
Click to expand...
This is scary. I thought that it was universal. By the way... how to know if it becomes series or parallel? The manual should mention it? What if I don't have the manual? There is a way to figure it out?
 
Hi Rob,
we are certainly talking electronics here!

I think it is well accepted that for quality bass reproduction a speaker needs to be connected to an amplifier with a very low output impedance? "Damping Factor" as it is called is the ratio of the speaker impedance to the amplifier's output Z.
Transistorized amps can have vanishingly small OP Zs but it is generally accepted that there is not much to be gained past a DF of 50 which equates to an OP Z of 0.16Ohms for an 8R speaker. This limit is because the speaker itself has a resistance and this is in series with the whole shooting match!

However, put another speaker in series and the DF seen by each drive unit now becomes at least 5-6R for an 8R speaker, in other words we have worsened DF to about 1.6! This would be bad enough for a single drive unit but hi fi speakers are at least two drivers and a crossover network so the current through each speaker is now governed by a complex, frequency dependent network.

Of course drive units ARE put in series. The legendary 4x12 guitar cab* but even tho' this is technically "bad" engineering it was done originally for power handling purposes and we have now come to know, accept and love the sound! In any case, valve guitar amps tend to have bugger all damping factor anyway!

Even so! Bass players were sufficiently fussy to have special Celestions wound with 32 Ohm voice coils so that all four could be wired in parallel and match an 8Ohm amp!

*There is of course two ways to do this. Two in pllel, in series with the other two, or two in series in pllel... There are players who swear they can tell the difference! Personally that is where I believe the snake oil seeps in and Russ Andrew's voice whispers in certain ears.

Dave.
 
I don't think that I would hear the difference of the sound on parallel or series. I am just concerned on not fry my future new stereo! LoL!

Anyway, I already lived surrounded by this world of gold plated contacts, monster cables and such. My dad takes part of this club. Nonetheless I have deep suspicions that he doesn't hear any difference too and just put his money on such stuff because others says so.

Well... what can I say? I am that guy that converted all his CD collection to MP3 and then gave away all the discs the day after. I think my ears are a total crap.

:laughings:
 
YanKleber said:
I don't think that I would hear the difference of the sound on parallel or series. I am just concerned on not fry my future new stereo! LoL!

Anyway, I already lived surrounded by this world of gold plated contacts, monster cables and such. My dad takes part of this club. Nonetheless I have deep suspicions that he doesn't hear any difference too and just put his money on such stuff because others says so.

Well... what can I say? I am that guy that converted all his CD collection to MP3 and then gave away all the discs the day after. I think my ears are a total crap.

:laughings:
Click to expand...

I am betting you would hear the difference Yan. In any case there is a very simple experiment you can do to prove both the fact of electro-magnetic damping and its beneficial effects on speaker cones!

Best done on a naked, big old guitar 12incher but you can do this with a boxed "hi fi" speaker.
With the speaker unconnected, gently tap the cone. You will hear a distinct "boing" especially with a naked driver. Now short the terminals and tap again. This time it will be a dull "thud" and you will feel that the cone is far more rigid and disinclined to move.

But you are right! Almost all of the Audiophile world is that of the AudioPHOOL! Gold is fine as a coating to prevent tarnishing and it is GREAT to solder but endows no audio benefit whatsoever, it is in fact not such a good conductor as Silver which itself is little better than good old Copper!

There an ongoing pisstake at Sound On Sound | Recording Techniques | Audio Technology | Music Production | Computer Music | Video Media forum about "The £907 jack lead"!

MP3? Do you have a good converter? Folks say that the highest level, 320bps is almost perfect? Samplitude Silver Pro freebie has a good converter in it that allows of all the quality levels.

Dave.
 
I was reading a review by an "audiophile" describing how much better his system sounded by using a nearly 1000dollar mains cord. That truly reeks of snobbery to me. The mains made the first sixty or so miles going through all sorts of transformers, overhead, underground, cabling, to the house which in so many cases still has aluminum wire (from the sixties and seventies) and yet that last 4 feet of mains cord makes all the difference in the world? Snake Oil.
 
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