How to connect more speakers to my existing home theatre system?

Question

I have a 5.1 channel home theater system, all the 6 channel jacks are connected to speakers of 3 ohms each. I have 4 old speakers from a previous system. two main speakers are 6 ohms each and the other two satellite speakers are 16 ohms each. and to top it all my home theater system does not have a line out jack at the back. How do I go about wiring these 4 speakers to my existing system?

Answer 1

Strongly unadvised... I'm with the others on this one... Don't do it.

Guessing with this sort of thing, voids your warrantly... has the potential to fry things that are at this point working. However, since you're asking...

3 Ohms, I'll also agree is a rather peculiar load... it's usually 2,4 or 6 Ohms... regardless... this is what you posted... so...

If for instance your amplifier is Class AB and running 50% effiency at 3 Ohms, and say 50 Watts... when you double the Ohms rating you've lost power ouput capability by as much as 1/2... So at 6 Ohms the given channel is now only capable of producing 25 Watts. When you half your power you've halved your effective dB levels by half. It takes twice the power to increase output by +3 (+10 db SPL's) which is a doubling of effective loudness to the average listener.

Typically, you don't want to step up or down more than a single impedance load level... I've yet to see a standard amplifier that'll drive 1.5 Ohms, stabily for your average home theatre system, so that leaves you with going up a level, or trying to stay as close as you can to the existing impedance load... so the maximum target impedance load would be 6 Ohms, and the minimum would be 2. I guess what you're asking, are there any combinations that I can safely wire so I don't fry my gear.

-=[The math...]=-

I don't know if you have a Philips HTR 5000, but it was the only one I could find with 6 channels, and a 3 Ohm load on all those channels... so... we'll work off that one... for examples.

http://www.p4c.philips.com/files/h/htr5000_01/htr5000_01_dfu_eng.pdf

Running Series we Add... running Parallel we take...

1/(1/a+1/b+1/c+1/...)

Where a,b,c are the differnt speakers wired in parallel. Another things you need to make sure, is that the RE (Thiele-Small Spec - RE is the actual DC resistance of the drivers voice coil) be matched to all the other drivers. I'll guarantee you this is not the case... and you'll find that on the satellites, and the mains that were shipped with the system will be working harder than the other drivers at the increased output levels. The high impendance drivers that you're attempting to wire in are more resistive, so the drivers are going to be handling different power levels, and now you risk underpowering scenarios to the motors which is far more likely to fry speakers. Anyways... warnings aside... And you can pretty well guarantee, as mentioned above this this just voided your warranty... ;)

Front speakers...

checking them in series... 3+6 = 9 Ohms... that's likely not going work... or if it does, it'll sound very quiet.
parellel... 1/(1/3+1/6) = 2 Ohms... that might work... but make sure you're watching heat levels on your gear...

So on a hypothetical, you can run your mains in Parallel... and still be able to hear something... at the servere risk of, you guessed it... 'cooking your gear'...

Rears...

> What you could do is run the sats as a
> second set of surrounds in SERIES.

I have to directly contradict The Sound Broker on this one...

> You now have 4 speakers running off the
> rear surrounds at a higher impedence which
> is easier on the amp as far as load.

I'll agree with you to a certain extent... but let's do the math on this...

Running the Satellites in Series... 3+16 = 19 Ohms...

If the amplifier is functioning at 3 Ohms stable, or likely recommended optimum... this just critically underdrives the speakers. 3 Ohms, doubled... becomes 6 Ohms, to 12 Ohms... to nearly 24 Ohms...

If the Channel has a maximum output of 50 Watts... we just went to 25, to 12.5 to 6.25 Watts... Over two speakers... 16 Ohms, suggests they were possibly driven from a Class A, or AB, Tube at some point. The liklihood of hearing much of anything out of those speakers is slim... as the output stages of the Reciever probably aren't functioning at much past 6 Ohms... This is more likely to cook the speakers, and disable the output capabilities of the amplifier stages.

If you run them parallel... 1/(1/3+1/16) = 2.52 Ohms... that's pretty close to 3 Ohms... but... it's obvioulsy pulling more current, something you have backwards, as you state here, that current is stable, indifferent to the impedance load.

> What it won't do is lower the current demands
> since you now have double the drivers to control

This really makes it sound like you know what you're talking about... but come on???

You've got is totally backwards... almost all amplifiers are VOLTAGE DRIVE... NOT CURRENT DRIVE... the difference? A big one... I see an awful lot of crap posts being dished out to unsuspecting people expecting to receive a decent answer... This is nonsense...

Voltage Drive - As the impedance falls, the load voltage will remain constant, as the current increases, and more power is created...

Current Drive - As you are suggesting... a majority, if not all Solid-State amps do not work this way... As the impedance rises, voltage increases, to maintain the same level of current. So as the current rises, the power output level increases...

No matter how you look at this, varying the impedance on a Voltage Drive circuit will alter it's current! Sheesh... for an audio guy, I find this flabbergasting.

As for the last part of the question...

> so watch the heat and listen for audible signs
> of clipping. You will obviously have to
> recalibrate your surround channel levels.

As you have suggested to wire this up, heat is not likely the issue, as there's way to much impedance to even pull any current to the speakers.. so the output power has been critically damped. Without current draw, there's no amplification, so there logically wouldn't be any heat, because no work is being done... Clipping? Huh? And then to suggest recalibration of the surround channel levels... Too funny, I haven't laughed this hard in a long time.

> and to top it all my home theater system does
> not have a line out jack at the back. How do
> I go about wiring these 4 speakers to my existing
> system?

I'd say at this point, unless you understand what's been written so far, I wouldn't even attempt it... Otherwise...

http://en.wikipedia.org/wiki/Series_and_parallel_circuits
http://www.rocketroberts.com/techart/spk_wire.htm

There is little chance this will increase the overall productivity of system. And the above mess is why... ;)

Answer 2

I would wonder why you would want to do this. For a number of reasons mixing speakers is not advisable. While you probably could devise a way to wire all the speakers at once it would be potentially risky (for the health of your amplifier) and/or likely to result in bisbalanced sound.

Furthermore, and potentially a secondary concern, but adding mismatched speakers will adversely impact on the timbre or nature of the sound. Audiophiles try to "timbre match" speakers in a surround setup by ensuring all speakers are either the same or from the same family from a single manufacturer.

Getting to answering your question ....

The first link below provides some of the basics of wiring speakers in series and parallel and how this changes the impedence presented to the amplifier.

The second link provides a discussion thread regarding a similar issue ... for information.

I'll leave you to analyze various options regarding wiring extra speakers ... although wiring a 16 ohm speaker in parallel and a 6 ohm speaker in series with each of your current front speakers might be a configuarion to consider.

The fact that your current system is driving 3 ohm speakers suggests it has good low impedence stability (something many amplifers do not have). But it doesn't guarantee that the amplifiers will be able to withstand the higher amperage which would result form driving a lower impedence. And wiring additional speakers in parallel with the originals would reduce the overall impedence ... potentially causing protection circuits to trip or even burning out the amplifier.

If additional speaker(s) are wired in series on a specific channel the overall impedence (load) is the sum of the individual speakers' impedence. This means that the power available from the amplifier for that channel is decreased (volume will be reduced. Although, given there are two speakers now working this will be to some degree compensated for, but not linearly).

My advice is that If you want "better" sound consider upgrading the speakers. And simply use the extra speakers in another room for a stereo setup selected by an A:B switch. On the other hand if you want to try wiring the extra speakers to your existing setup, you probably now see why I suggested the combination of parallel and series wiring of two speakers to the front channels.

Hope this helps.

Answer 3

Probably not a good idea on the fronts. You want tonally matched mains and mixing can cause acoustical chaos with all sorts of phase issues and cancellations. If you have speakers that are at 3 ohms (are you certain this is the case?), then that is a very hefty impedence load for most 5.1 channel recievers. What you could do is run the sats as a second set of surrounds in SERIES. This won't give you a true 7.1 setup, but you may have better surround coverage (run one set of surrounds on the sides, one set in the rear). To wire in series, you do as follows. Keep in mind that red is always positive and this assumes you have standard twin wire positive/negative speaker hookups...

Amp positive to speaker 1 positive. Speaker 1 negative to Speaker 2 positive. Speaker 2 negative to amp negative. This is for one channel. Do the same for the other channel and then DOUBLE CHECK EVERYTHING! You now have 4 speakers running off the rear surrounds at a higher impedence which is easier on the amp as far as load. What it won't do is lower the current demands since you now have double the drivers to control so watch the heat and listen for audible signs of clipping. You will obviously have to recalibrate your surround channel levels.

Answer 4

Don't do it. If you want a louder system, simply adding speakers won't give you that much more volume since you will be dividing your amplifier power between more speakers. Not to mention that impedence mis-matching can easily blow your amp. And the other poster is correct to say that mis-matched speakers in a surround system don't sound very good.