Can I drive four speakers on a 2-channel receiver?

Factual Questions
1

I have a home-theater-in-a-box receiver that does a fairly good job of driving a standard 5.1 setup. For a few terribly uninteresting reasons, I want to move it to the parlor. In the parlor, we have NO television, but we do have four bookshelf speakers strategically spread out and a subwoofer.

While the receiver has enough speaker outputs, it is not possible to bypass the surround sound filtering. This means that the right and left “rear” speakers have an odd echo to them and are a bit behind the “front” speakers. They are all wired in the wall and strategically placed around the room so there is no true front and rear to correspond to, so it ends up sounding like crap.

So, looking at the bundle of wires coming out of the wall, I’m wondering if I can solder the two left speakers’ wires (four total) and end up with just two wires to plug into the left channel jacks on the receiver. I’d do the same with the right side, and, hopefully, end up with the receiver thinking it’s driving a 2.1 system—sans any surround effects.

Or will it end up sounding like crap?

Thanks,

Rhythm
Warning: boring parts ahead!
What, you’re curious as to why I’m asking this? Well, there are actually three receivers in the house. This one is not in use at the moment. The second just died. The third is in the parlor now. That one is a higher-end component, which would be great for 5.1 theater, but since it can drive two sets of speakers (A/B) without distorting the sound, it’s in the TV-less parlor. Given the aforementioned death of the den receiver, I’m hoping to move the good unit from the parlor to the den, and the subject of the OP from the basement to the parlor.

2

It will probably work fine. If you wire the speakers in parallel, they’ll have half the impedance of a single speaker. If the speakers are 8 ohm speakers, and the receiver can drive 4 ohm speakers, there’s no problem. If the speakers are lower ohms, or the receiver can’t handle lower ohm speakers, the resulting impedance might be too low.

I have a box to drive up to four pairs of speakers from a single output, and it has a “protection” button, which is basically just a resistor added in series. I don’t use it if I only use two speaker pairs, and then it’s just like your set up, and sounds fine.

3

Let me make sure I understand the problem. You want to power four speakers with a two-channel receiver (and not the 5.1 home theater system that the first and second paragraphs seem to be talking about). Right?

If so, the answer is a guarded “probably.” Powering two speakers in parallel halves the impedance the amplifier sees on each channel. Many amps can handle a range of impedances with no problem. Check the rated impedance range for the receiver and the rated impedance of the speakers you’re connecting. Most speakers are about 8 ohms. If the receiver says it can handle a 4-ohm load, you’re fine.

Someone else here will remind us what the risk is of putting too low a load across an amplifier’s output: whether it can damage the amp, or the speakers, or merely result in distorted sound. I used to know, but it’s been a while since I worked in pro audio, and I may not be up on all the latest technical developments that might have changed what I did know.

BTW, what did you mean by “it is not possible to bypass the surround sound filtering”? Are you talking about a malfunction in the 5.1 home theater receiver? If it’s not broken, there should be no reason why you can’t turn off the surround and/or the echo effects. But if you’re not going to use that receiver in the parlor, why bring it up?

4

Wow, sounds (heh) like this just might work. Maybe. I know how to solder, but I don’t know an ohm from a gnome.

From the manuals, the receiver’s power output is 8 ohms 40 Hz - 10 kHz, THD 0.7%, 70W + 70W.

The speakers’ rated impedance is 8 ohms.

How can I tell if the receiver can drive 4 ohm speakers? Should there be a setup somewhere in the manual? An actual switch? Or if it’s rated for the higher, 8 ohms, it will be able to handle the 4?

5

I tried using this receiver in the parlor when we first moved a few years ago. After a couple minutes of listening, something was sounding off. I traced it to the aforementioned surround problem, and I dug out the manual to see if I could just drive pure, non-encoded sound to each of the speakers. I went as far as getting Sony on the phone (three different techs, no less!), but to no avail. On this basic model (HT-DDW650) the L and R “rear” outputs are supposed to be surrounds, and their effects are hardwired. While I can change sound fields (e.g., stadium, hall, action), I can never get just pure sound to come out all four speakers. The “rear” ones were always a bit quieter and ‘off.’ This paraphrasing of a three-year-old conversation may be off in some details, but I did spend an inordinate amount of time on the phone with them, with the manual, etc.

In the end, this is why the better theater system is being underutilized in the parlor–it had the ability to drive the four speakers on its own. Now, if I can do a bit of wiring to get this receiver to do the job out of the two front speakers, I’ll finally be able to liberate the home theater receiver back to the den!

6

Ah, I see. But this is exactly how all surround receivers work and are supposed to work. The rear channels are only surround, never the full output of the front channels.

But you should be able to achieve what you want with the home theater receiver and perhaps even with the other stereo receiver, if either of them have A + B speaker outputs. If so, just connect the front speakers (L+R) to the corresponding A speaker outputs and rear speakers to the B speaker outputs. Then switch on both A and B speakers from the front panel. Presto!

(The question is, Why do you want to do this?)

If neither receiver has B speaker outputs, then all you can do is the parallel hookup that ZenBeam and I have described. Your manual should say what impedance range the amp can handle.

7

You’ll be able to get sound out of it, no problem. (Don’t even need to solder, just connect two wires to each amplifier terminal.) Bottom line: you’d be safest just running two speakers, but you’re mostly safe if the speakers are moderately efficient and are listened to only at moderate levels. But, functionally speaking, problems might arise:

Temperature. By hooking up speakers in parallel, you reduce the impedance, which in turn increases current for a given voltage. (Voltage is what you adjust by turning up the volume selection.) Increasing current increases temperature. Make sure the receiver has plenty of ventilation; when you start operating the unit, test to see that it doesn’t get too hot at normal listening levels, and then again at as-high-as-you-expect listening levels, before letting it run unattended. If heat is at all an issue, you’d be well served by dusting the unit–which requires opening it, which you shouldn’t do without knowing the basics of electrical safety.

There may also be an issue with using in-wall wiring, but I’m not sure if that’s a factor here or not. (Thin wiring heats up with more current, so there is a possible fire hazard.)

Bass response. If the output impedance is high, which it might be on a commodity receiver, and the nominal speaker impedance is low, which you are creating by running them in parallel, you may find that the speakers simply don’t deliver as much bass as they would in normal circumstances (e.g., a single speaker per channel). This probably isn’t an issue, though, if you move your subwoofer into the parlor.

Clipping. If the amplifier cannot deliver the current you’re asking of it, clipping will occur. This sounds bad, but also can cause damage to your speakers. And, in this instance, if it is in the range of clipping, it is probably running hot, which can cause damage to the amplifier. Clipping would be your primary signal that this setup is not a good idea with this receiver.

Another option would be to run the speakers in series. This would avoid the impedance issues… but, I haven’t heard of people doing this, and I’m guessing it is because of phase or interaction issues. You’re certainly welcome to give it a try and listen to it, though.

8

The JVC unit currently in the parlor has A/B switching – it’s how we’re driving the four speakers now. The Sony, the unit in question, doesn’t have the two outputs, so without doing the above I can’t get it to drive all four without it treating two as rear. Since the JVC is the better theater unit, we’d really like to move it to the 5.1-enabled den to take advantage of its prowess. Since the parlor is only CDs and minidisks, digital sound processing by the receiver isn’t as paramount.

Why the obsession with four speakers? The parlor is roughly rectangular, running north to south. Our two main chairs (think Archie and Edith Bunker, but much more chill and much more comfortable) face each other, but are each about five feet away from the north and south walls. There is also a couch that’s about five feet from the west wall – all seating has walkabout room behind and between them. The east wall has the bookcase/fireplace. The speakers are arranged so that the northeast and southeast corners each have a left channel, and the northwest and southwest corners have a right channel. (This is all very general, nothing is so linear.)

The end effect is that practically wherever you sit, you’re placed fairly between two well-defined channels. They’re small speakers, so there isn’t overlap per se – rather, the stereo definition is sharply defined. Dark Side or Unsquare Dance, for example, effortlessly dance back and forth. Another benefit of the setup is that lower volumes sound fantastic as well. There’s no place to put two speakers that won’t sound either too loud to the person sitting near them or too soft to the person sitting further away.

I don’t know off hand what gauge the in-wall wires are, but they are heavier than the standard, thin speaker wires that come out of a general box.

The parlor has its own subwoofer, one that came from another theater system (merged systems yield some fun extras!). It doesn’t have regular speaker terminals, but rather relies on the in-receiver crossover and output. But it sounds great for the setup, and allows for extraordinarily rich sound to come from a relatively cobbled together system. Yes, I do drool over the Crutchfield catalog, but am amazed at the quality of what we’ve been able to do.

As for clipping, if I have all the specs in front of me, what should I look for to see if it’s worth re-wiring everything? Or is this something that can’t be gleaned from stats, only from trying it out?

What is running speakers in series? Does that mean wiring one speaker to the next, then to the receiver?

9

That’s the quickest way of finding out. If you start off with a low volume and slowly increase it, you can tell when you start to clip.

Yes, and a lot of people don’t recommend it, as you can get distortion. No speaker is identical, even similar models from the same manufacturer. I haven’t tried it myself, but have heard can can create back EMF which would be a source of distortion.

10

Thanks for the explanation. That all makes sense, more or less. I’ve never heard or thought of a setup like that, but if it works for you, why not.

Series means: AMP + ----------> + L SPKR - ----------> + R SPKR - -----------> - AMP.
I seriously don’t recommend it. It will put your speakers out of phase.

In the specs for the Sony, look for “speaker impedance.” If its low range is at or near 4 ohms, you’re golden.

If not, try it out carefully, and look for the warning signs awk.pine describes: clipping (crackly distortion) and overheating. If you tend to keep it at low levels, you’ll probably be okay. If you like to crank it up, watch out for problems, and if they don’t turn up after 30 - 60 minutes, you probably won’t have any long term trouble.

However, IANAPHTI (professional home theater installer), I am not licensed to practice in your jurisdiction, I’m not your PHTI, and you’re not my client. If you fry your receiver, you’re just getting what you deserve for following the advice of some anonymous poster on a message board who, for all you know, could be a dog or Osama bin Laden.

11

Note to the DHS guys banging on my door: I’m not Osama bin Laden. Really!

12

While I used to work in Pro Audio, recording studios don’t hook up speakers either in series or parallel so I never played around with it.

(Or I’m a dog with better than your average canine typing skills. I’ve got enough things going on in my life without the police showing up, so I’m not going to claim any affiliation with terrorist organizations.)

13

I used to work in pro audio, too, both in studios and PA sound for bands, and TokyoPlayer is right.

We should be perfectly clear about this: wiring more than one speaker to an amplifier speaker output is simply not done in any form of professional sound system or well-designed home theater system. It’s never recommended.

What we’re suggesting here is just to help you do what you can with what you have. Chances are pretty good that the parallel setup will work fine, or that if not, you can catch the problem before any permanent damage is done, if you’re careful. But if you’re unwilling to take a small risk of damaging the Sony receiver or the speakers, you should just buy a decent low-cost receiver with A + B outputs that will do exactly what you’re trying to do. You could probably find something on eBay for $100 or less.

14

I hope not the part about being a dog. . .

Agreed. If you start with the volume at zero and slowly increase it, then you should be able to catch the problem in time, but there could be a small risk.