Can I use two sets of speakers with a hi-fi system?
March 23, 2011 12:01 PM   Subscribe

I have ended up with two sets of speakers for a hi-fi system. Can I use both sets, or will the result sound odd or damage something?

I have an Aiwa CX-ZL500 hi-fi system. I have two pairs of speakers for it. (One is for whatever the predecessor to the ZL500 was; I had one, it died, and I kept the speakers.)

I want to find out if I can use both sets of speakers at the same time. I'm guessing that I won't get full power from them, but I'm more concerned to make sure that I don't damage something. (I can't see that I should, but I know very little about hi-fi systems.)

The main unit claims to output 2x135W (via subwoofer) and 2x45W (main speaker, I guess). I can't find details for the speakers, but I presume they match that output.

If this is a bad idea, tips for how I can use these with a MacBook would be useful. (I presume I need some sort of amplifier.)
posted by Grinder to Technology (19 answers total) 3 users marked this as a favorite
Best answer: Your amplifier is putting out power to force the signal out to the speakers -- so how much resistance the speakers pose is the important part. Most home speakers are 8 ohms, possibly 4 ohms.

If you wire the speakers in parallel, the resistance drops; if you wire them in series, the resistance increases (more info) -- the back of your amplifier should say the minimum and/or maximum load for speakers. Too high or too low resistance causes more wear and tear on the receiver, and could burn something up. 45w per channel isn't a whole lot of power, so you'll probably be fine either way.

As for speaker watts, as long as the speakers are rated at higher than the amp puts out, you'll be OK.
posted by AzraelBrown at 12:32 PM on March 23, 2011

To know for sure, you would need to tell us the characteristics of the speakers.

Under-powering or over-powering can damage speakers.

If you're not too afraid of damaging the speakers, you can trying running it at very low volume. If you hear any distortion, stop.

A search for speaker clipping damage will give you more info.
posted by paulg at 12:40 PM on March 23, 2011

Best answer: The speakers are probably 8-ohm. (There are other impedance values for speakers but generally only found on subwoofers or older L/R ones, in my experience.) If that assumption isn't correct, you can forget everything I'm saying below.

What you're talking about doing is putting the speakers in parallel, if you're going to plug two speakers into the L channel and two into the R.

Two 8-ohm loads in parallel is 4 ohms. (The formula is 1/Req = 1/R1 + 1/R2 ... 1/Rn; I'll leave the math as an exercise for the reader.) Depending on how much you like your amp, I would be a bit nervous plugging a 4-ohm load into it when it expects 8. Although if you check your amp's documentation, it's possible that it might have a switch on it for 4 ohms ... I have seen some older amps that do that, but not too many made recently. But I guess it's worth a look.

If that's not the case I would probably not go forward with it. It's impossible to say without knowing the design of the amplifier how it'll react to having half the impedance that it expects; maybe it'll be fine, maybe it'll sound like crap, maybe it'll blow fuses. I'm not entirely sure but either one of those seem plausible. If this were some piece of junk that you weren't terribly fond of I'd say sure, go for it, but that doesn't seem like the case.

Pick yourself up another decent 2-ch amp and use it to drive the other two speakers.
posted by Kadin2048 at 1:04 PM on March 23, 2011

I'm absolutely not an audio guy like the folks above, but I have pretty much the setup you're asking about in my living room. I basically just spliced the speaker wires together and jammed them into the unit (and old CD changer/two tape deck affair like I think yours is- 40ish watts), and ran it to two "left" speakers and two "right" speakers, as well as a big old Bose subwoofer that's also spliced in there somehow. I think of it as the poor man's surround sound, and it works totally fine. I live in a small apartment, though, so I never really turn the sound very loud- if you're going to be cranking it, you may want to be more careful.
posted by zap rowsdower at 1:40 PM on March 23, 2011

Best answer: This is easy and inexpensive. What you want is an impedance matching speaker switcher. Do not do this any other way.
posted by PareidoliaticBoy at 2:01 PM on March 23, 2011

Response by poster: Thanks - the speakers are 6 and 8 ohms, for low and high frequency respectively. Yes, I am thinking of putting them in parallel. The back of the amp says that it wants the same impedances. It seems that this is a bad idea, so I guess I will go look for an amp that I can use with my MacBook...
posted by Grinder at 2:21 PM on March 23, 2011

Best answer: I wanted to get that post up right away, before you blew the voice coils in your speakers. Aiwa makes better than normal power supplies, but no mini-system can reliably power multiple speaker sets with unknown impedance. That switch-box I linked to solves this problem neatly.

Now, as to using the extra speakers separately with a mac book, this is different kettle of fish altogether. I suggest that you have a look at "T" class amps like this little mini-amp.
posted by PareidoliaticBoy at 2:24 PM on March 23, 2011

Above link is actually two different "T" class amps.

You missed my link to impedance matching switch-boxes, I believe.
posted by PareidoliaticBoy at 2:30 PM on March 23, 2011

Response by poster: PareidoliaticBoy - thanks, and don't worry, I'm not going to plug anything in for a while.

Yes, those look like good solutions. I have a clueless question about the mini amps - those seem to be underpowered for the speakers I'd be using (the watt rating is less than half of what the speakers claim): does this matter? (I am going to go and educate myself on all of this in time!)
posted by Grinder at 3:33 PM on March 23, 2011

Watts in amplifiers and speaker ratings are actually meaningless. GASP! Yep, its mostly marketing drivel. It's all about the current. I won't bore you with the details right now. Tell me about the extra speakers you intend to drive; brand, model, size, any specs on them. Pictures of the speakers with the grills removed might be useful as well.

Having determined what hardware resources we have, the next question is the needs qualification. What is your sound goal? Did you want to connect everything into the Aiwa, and run two sets of speakers, say a pair in the living room, and another pair in the bedroom, as an example. OR are you wanting to create stand-alone sound from the computer?
posted by PareidoliaticBoy at 4:49 PM on March 23, 2011

I came in to suggest you look into T-amps for pairing with your powerbook. The wattage rating on speakers is a maximum and is pretty unimportant to the average listening scenario. Of more interest to your situation would be the sensitivity or efficiency of your speakers. That will be in XXXdB/W/M. That will tell you how loud your sound output will be. Keep in mind that tells you nothing about the quality of the sound. Here's a good primer if you want to delve a little deeper into that.

This is getting into stereo philosophy a little more than you probably want to go but I have certainly found that great speakers are the critical foundation of achieving a sound I like. If you do get a t-amp and are unhappy with the sound I'd suggest you look to your speakers first as the problem.
posted by tinamonster at 4:53 PM on March 23, 2011

Now that my post is written in white and green I realize that sounds a little dickish at the end. I'm not speaking about your speakers in particular since I don't know much about them. I'd say that to anyone unhappy with their sound. Best of luck.
posted by tinamonster at 4:56 PM on March 23, 2011

No tinamonster, you are absolutely correct. But if you read carefully, you'll see that this question isn't a quality issue for Grinde, it's a functionality issue. One step at a time, though. This is why I asked for specs on the existing speakers. We'll work with those initially. Then, once we get everything up and running, we'll gradually convert Grinder to the dark side of Hi-fidelity. We haven't even begun to address how the listening environment colours and affects sound, as just one tiny example.
posted by PareidoliaticBoy at 5:34 PM on March 23, 2011

Response by poster: OK. The extra speakers are Aiwa SX-FZ1800. They are bookshelf speakers. I don't think I have specs for them - I must have thrown out the manual for the old hi-fi when it died. The new speakers would be very similar, perhaps a little better quality but not as loud, and they are 89 db/W/m. As someone who knows nothing about hi-fi, I found the quality good with both sets. If you could help me identify good specs for an amp that would match those speakers, that would be great.
posted by Grinder at 11:33 PM on March 23, 2011

Well if they're another set of mini-system bookshelf's, then almost anything will work. The Lepai Tripaths linked above seem to have huge quality-control issues, and returning stuff sucks, so I'd stick with Pyle Pro. I have had 1/2 dozen successful applications of them with no QC issues so far. 15 watts is a bit on the thin side if you ever wanted to upgrade your sound, so for a few dollars more, I'd get this Pyle Pro 40 watt model.

Don't forget to add a 3.5 mm to rca cable to hook up your computer's audio output. You might also want to get some speaker wire, while you're at it.
posted by PareidoliaticBoy at 2:04 AM on March 24, 2011

Response by poster: Thanks. These speakers have two sets of inputs - one is speaker wire and the other is an RCA jack. I think the second is for the sub-woofer (which is built into the speaker). The amps you're mentioning don't have the second output. I did some quick looking around, and something like the Auna AMP-2580 seems to have both. Would something like this work?
posted by Grinder at 2:14 AM on March 24, 2011

Interesting. Can't find specs or owners manuals for either of those systems online. Let's try this. Substitute one of the speakers from the old system for one of the speakers from the new system, and listen to them to hear how different they sound. Can you takes pictures of the backs of both sets of speakers?
posted by PareidoliaticBoy at 5:03 PM on March 24, 2011

Response by poster: There are manuals and some links for the new system at

The old speakers are boxed in storage - I'll need to set them up but will test and take pictures shortly.
posted by Grinder at 4:34 AM on March 27, 2011

Yeah, I'm not giving them email to download the owner's manual for the new system. Anyway we don't need it, we can test this without the manual. Drop me another memail when you get those speakers out.
posted by PareidoliaticBoy at 7:23 PM on March 28, 2011

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