[Closed] 4 speakers on a 2 channel amp .... Certain death?

If you wire them in series you have nothing to fear.

If you don't get the polarity right ie both pluses together and both minus' together the audio will be out of phase which basically means that any "mono" signals will cancel each other out - in practical terms that means the vocals amongst other things will be quiet (if you stand directly between a pair of out of phase speakers it sounds really odd.) Also the whole setup will be quieter as each channel will be split between two speakers instead of all on one.

It wont kill you though. 🙂

It might be quieter because the higher impedance of the speakers in series will reduce the power output of the amp, but two speakers instead of one makes little difference and is usually a bit louder for the same impedance. IME four speakers instead of one of the same impedance sound louder than one speaker. For example a 4x12 16 ohm guitar cab is louder than a 1x12 16ohm cab driven by the same amp on the same settings.

The 4x12 cab uses 16ohm speakers with pairs of speakers in parallel (8ohm) connected in series to get 16ohm.

You are right about needing to get the phase right. IME it's standard across the industry (for guitar speaker anyhow). If the red + and black - terminals are right the phase will be right.

The only risk of killing it is wiring two speakers in parallel which halves the resistance, doubles the current and increases the heating of components four times.

I've got a 2000 era Sony Hifi. It owes me nothing, so I completely ignored the advice given in a shop after seeing the price of dedicated amps, and for the last 6 years or so it's been running two pairs of hi-fi speakers, two pairs of ceiling speakers and a single stereo ceiling speaker through a speaker switch box.

Most of the time it's playing to at least 3 pairs and sits there for hours streaming music, more so now my wife works from home. And it plays the radio every morning for an hour on timer. It hasn't missed a beat, it was cutting out the sound for a while but it turned out to be a problem with the speaker connections inside the unit.

I wired my kitchen and bathroom speakers in series after a while as those rooms were too loud compared to other rooms (I don't have individual volume control, just off or on)

If you wire them in series you have nothing to fear.

Other than it sounding a bit crap. Better to wire them in parallel, but then the fear is too low an impedance load for the amp. Even then I wouldn’t worry too much, it may get hotter than usual if really working it.
What’s the impedance of each speaker and what’s the minimum rated impedance on the amp? If both speakers are 8 ohm and the amps rated to 4 ohm you’re laughing.

You need to see what your amplifier is rated for and what rating your speakers are. There will be a Watts rating for a particular impedance load, commonly the load will be 8ohms. Eg 30watts into 8ohms

Wiring the speakers in series will double the impedance, wiring in parallel will half the impedance, assuming the speakers are identical.

So using ohms law: volts = amps x resistance. And power = volts x current.

The amplifier will have a maximum voltage it can output which is fixed. The resistance you changing by changing the speakers wiring topology and the current will change in reactance to this.

So if you double the resistance you will half the current, which will half the power.
Eg 30watts into 8ohms -> 15watts into 16ohms

And if you half the resistance then you double the current and double power.
Eg 30watts into 8ohms -> 60watts into 4ohms.

Wiring in series is usually safer as you are reducing the amount of current and power the amp is supplying. But it won’t provide twice the sound due to two speakers. The power is halved so you end up with same level of sound but usually you hear slightly less as there are losses in the system and your ears are not linear.

Wiring in parallel will give you a louder sound as the power has been increased but that assumes your amplifier can supply double the current. The transformer or power supply may not be rated to supply twice the current. At best you will get clipping ie the output will be highly distorted at worst something in the amplifier will melt or go pop. The voice coil in speakers could also be damaged as they might not be able to handle the higher current.

So check what your amplifier is rated for and what impedance your speakers are.

Sorry to hijack thread, but can somebody explain what 'wiring in series/parallel' actually means, like how it is done?

For example, I have an amp which is listed as 70w per channel. It has two pairs of speaker outputs, A + B. You can select either or both, or off for headphones only. Now I have one pair of speakers currently so have them wired in to outputs A. However, I have another pair of speakers that demand more power. I'm wondering if I could wire them in such a way as to use all the available power of the amp: like wiring the left speaker across outputs A, and the right across outputs B, and selecting 'both' speaker outputs on the amp. Hoping that makes sense?

There will be online explanations, and there is even more to what you are asking also.

Selecting "both" doesn't give you more power it just switched both outputs on. It doesn't have spare power it's not using. You control the power with the volume knob

And if you say your 2nd speakers "require more power" do you mean they are rated at higher W? The latter is about power handling, their power demands are about efficiency (dB/W).

like wiring the left speaker across outputs A, and the right across outputs B, and selecting ‘both’ speaker outputs on the amp.

Hypothetically if you were to do that you'd be splicing left and right channels together and you'd end up with a mono system. You'd be better off, assuming it to be a good idea in the first place, to wire the left speaker to the left output of A & B, and the right one to the right of A & B. Whether it'd be a good idea rather depends on your amp, most will just drive two sets of speakers in parallel off the same amplification circuitry so you'd gain jeff all by doing it.

In practice, I'm not sure as I'd chance it without knowing for sure unless the amp was deemed sacrificial.

But as Al says, audio power is... complicated. You're going to have to elaborate on what you mean by "demand more power". If you're just saying that you've got a pair of 100W speakers then you'll be right, that sort of rating is what they can handle rather than a requirement. If they explicitly require say a 100W-500W amp to drive them (do you live in a night club?) then that's a different barrel of whelks entirely.

But as Al says, audio power is… complicated.

Aye right, it is. And I thought I knew a thing about it...

The speaker say on the back: POWER CAPACITY PROGRAM 60W MAX 120 8 OHMS

Lots of people on the internet recommend using a "well powered amp" of at least 100W per channel to drive them. Which is why I sometimes worry that I'm at best, not getting the best out of them / worst case causing slow damage or risking blowing the drivers using my amp rated at 70W per channel 8 OHMS.

do you live in a night club?

Haha, not quite. I live in a normal flat. But to spare my neighbours I rent a unit in an industrial part of town where I can keep my noisy stuff and make a racket 24/7.

Thanks all, sorry for the hijack.

A+B speaker outputs are usually to bi-amp your speakers (if your speakers support that). It drives the tweeter (high frequencies) and woofer (low frequencies) separately in bid to get better sound quality and you have the option of using different cables for each one to further refine the sound you get. But as cynic-al and cougar say it won't get you more power. Never tried it my self so no idea if actually works or if its in the audiophile snake oil category?

Regarding needing at least 100W for a home speaker ... I call BS. 20-30W is usually more than enough. The main problem is the amp ale to supply enough current and preventing clipping of the output. The distortion from clipping can damage a speaker much more than clean signal at a higher level.

So unless your speakers are some eccentric speakers that specifically require higher power amplifier most normal speakers will be happy with 20-30W.

The speakers should have a sensitivity rating in dB/W, decibels per watt. ie how many decibels will they produce from 1W when measured standing 1 metre awy. usually this is in the range of 80-90 db/W. 80 db is a reasonably loud sound so really you only need a 1W to produce a reasonably loud sound and 2W for a very loud sound. This value will be for one particular frequency eg 100KhZ the lower you go the more energy required so the sensitivity drops off.

So usually after you've accounted for low frequencies and added headroom to prevent clipping and to cope with sharp spikes in the audio etc.. a figure of around 20-30W is normally stated as a good safe level that will also produce a loud sound for most home speakers.

Assuming the volume dial starts at the 8 o'clock position and rotates to around 4 o'clock as is usual on amplifiers. As long as you are not going too too far past 12 o'clock to get the desired volume you should be OK. Thats a very imprecise rule thumb so not applicable to every amplifier.

A+B speaker outputs are usually to bi-amp your speakers

I don't believe that's what is being described here, rather it's a multi-room feature. I used to have a similar amp, two sets of speaker connectors on the back and two buttons on the front. Each button controlled one set of outputs so you could drive one or the other, both, or neither.

... the latter of which had hilarious consequences when I decided to listen to some music in the small hours one night, jacked in headphones and dialled it up to 11. To then have my then-girlfriend screaming down the stairs going "WTF do you think you're doing?" It turned out that unlike every other audio device I'd ever owned previously, plugging something into the headphone socket doesn't automatically disable the speakers and you've to press the A / B buttons to turn them off. I probably woke up half the street. Whoops.

Never tried it my self so no idea if actually works or if its in the audiophile snake oil category?

I rather suspect the latter but the jury is out even amongst AV nerds.

Jambougie, that's more or less a nightcub