Connecting multiple speakers to one output.

 

New member
Username: Jkingma

Post Number: 1
Registered: Nov-11
I want to connect 8 speakers to my receiver but there are only connections for 4 speakers. Can I connect 2 speakers in parallel to each jack or will that damage the speakers and/or receiver?
 

Gold Member
Username: Hawkbilly

Nova Scotia Canada

Post Number: 1441
Registered: Jul-07
I think the general rule is that for parellel connections the impedence is halved, and for series it is doubled. So, assuming you have 8 ohm speakers, connecting any 2 of them in parallel would lead to a 4 ohm load. Keeping in mind that the impedence of your speakers flucuates across the frequency spectrum (above or below 8 ohms) the overall impedence could at times be closer to 2 ohms. Most big box receivers will struggle mightily with that type of load, which can overheat your receiver. Frying your receiver could also lead to unfortunate results for your speakers as well.

A series connection may be more advisable but I'm far from an expert.

Why would you want to connect 8 speakers ? Are they in different rooms ?
 

New member
Username: Jkingma

Post Number: 2
Registered: Nov-11
"Why would you want to connect 8 speakers ? Are they in different rooms ?"

Yes, thats correct.
 

Gold Member
Username: Superjazzyjames

Post Number: 1763
Registered: Oct-10
My suggestion: Connect two speakers in series to each pair of terminals. This will maintain a NOMINAL impedance of 8 ohms. Keep in mind that what Chris said with regard to impedance and receivers handling it is correct.
 

Gold Member
Username: Illuminator

USA

Post Number: 5616
Registered: Apr-05
Not only will it just overheat your receiver, but you risk frying the output IC's or components in the power supply. Once upon a time I had a flagship Onkyo TX-DS939 and I hooked up a 3 ohm load (unknowingly) to it and blew a capacitor in the PSU. Fortunately it was an easy fix (new cap for $2, though slightly difficult to find locally), but could have easily been worse.

Like James said, best to wire the speakers in series. Also, you could consider getting a speaker selector box to switch between the sets of speakers (radioshack carries these devices) if you don't need each set of speakers playing simultaneously.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16953
Registered: May-04
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"I want to connect 8 speakers to my receiver but there are only connections for 4 speakers. Can I connect 2 speakers in parallel to each jack or will that damage the speakers and/or receiver?"


"4 speakers" would normally mean two pairs of speakers and "eight speakers" would be four pairs. If "eight speakers" means eight pairs of speakers, then we need to clear up the confusion. You don't mention what receiver you have but I would hope it's a fairly safe bet to conclude any modern "stereo" receiver has two pairs of speaker outputs wired internally to be in parallel. (if you're trying to make this connection to a home theater type of receiver, we once again need to clarify what components you own and intend to use. Very little that applies to a two channel stereo receiver transfers easily to a 5.1 HT receiver when multi-room speakers installations are desired.) In other words, with a two channel system, when only speaker "A" is engaged, the amplifier sees a load which represents one pair of speakers. When both "A" and "B" speaker outputs are engaged, the amplifier sees a parallel connection which would then show the amp approximatey half the impedance of the lower impedance speaker of the two pairs. (There are also receivers being built today which do not allow both speaker ouptuts to be active simultaneously. In this case, when you engage one speaker switch, the other switch is automatically disengaged in order to provide protection to the amplifier.) Therefore, if one set of speakers presents a nominal eight Ohm load while the second speaker set represents a nominal impedance of six Ohms, the amp will see a load of approximately three Ohms. Most modern receivers would be hard pressed to withstand a three ohm load for any length of time if the volume levels are being pushed.

You also do not mention whether the speakers you intend to connect are all the same speaker model or whether they differ from each other. In other words, here you have failed to provide any information which might tell us more about the load the individual speakers will present. Further, if one set of speakers is rated as a "nominal" or average eight ohm load, the strong possibility exists that any speaker will not remain at eight ohms for its entire frequency response. With a wandering impedance from each speaker set it would be quite possible for even two pairs of "nominal eight Ohm" speakers to show the amp a load which would qualify as dangerous. Since we know nothing about the impedance of each speaker set or the capacity of youru receiver to drive low impedance loads, the safest way to recommend you go about this matter would be to suggest you insert a master speaker selection switch box between the amp and the individual speaker pairs.

Only connecting speakers in series presents a few problems. By using a series connection between the speaker pairs both speaker sets must be playing at the same time - there is no way to switch off "set one" and only have "set two" playing. The same problem would apply to volume control, both speaker sets would have to be playing at an identical master volume level. Connecting two sets into speakers "A" on the receiver and two pairs into speakers "B" on the receiver without any intervening volume controls would further mean all four pairs of speakers will be set at the same output level by the master volume control of the receiver. It would be a very unusual installation where all four pairs of speakers were intended to play all at once and all at the same volume level.

Buying a small speaker switch box to insert between the receiver's speaker outputs and the individual pairs of speakers will; first, provide control over which speakers are playing at any one time. If there will only ever be just one pair of speakers playing at any one time, the switch is all you will need. However, it is also highly unusual for a multi-room installation to only have one pair of speakers playing. More likely is the siutuation where you want more than one pair of speakers playing and that you would also want to control the volume level of each pair of speakers. Now, if your system requirements are typical, you will require volume controls to be inserted into the system either at the master control area of the receiver and speaker selector or you could use a switch box located with the receiver and individual volume controls in each room with the speakers. You'll have to decide which set up is the most convenient for your installation. If you are doing a pre-wire of a new house being built, then individual controls located with the speakers is the best overall choice. For pre-existing construction, it's often simpler to locate the vc's in the same spot as the speaker switch box.

Using autoformer type volume controls or an autoformer based speaker switch box is the best way to ensure the safety of the installation. Autoformers inserted between the amplifier and the speakers will always ensure the amplifier sees a solid eight ohm load which would never vary up or down no matter how many speaker sets are in use. This is the safest way to protect your receiver from a dangerous drop in impedance load. Use either individual autoformer volume controls or a single autoformer based switch box with volume controls. You only need the autoformers in one location. If you buy the autoformer switch box, then use conventional L-pad type volume controls. If you use the autoformer type volume controls, then a conventional switch box is your choice.



There are less expensive switch boxes and volume controls available. IMO the autoformers are well worth the investment as they will last for the life of the install and there should never be a situation where the receiver blows up due to impedance loading. Any shop that specializes in full house automation or sound systems should be able to recommend the appropriate products once you've explained how you intend to use the system. The autoformer volume controls and switch boxes are also available on line. Generally, I recommend you go through a local dealer whenever possibe for after the sale assistance should you have problems installing the devices.




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New member
Username: Mike_q

Post Number: 1
Registered: Nov-13
I also have a 140 watt mini stereo with only 2 outputs. I want to connect it to 4 8-ohms speakers. What would be the best connection in my case? Series or parallel? Your feedback is appreciated. Thank you
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17807
Registered: May-04
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Are your intentions to simultaneously run all four speakers? Or is this an either/or situation?
 

New member
Username: Mike_q

Post Number: 2
Registered: Nov-13
Yes I like to run all four speakers simultaneously.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 17808
Registered: May-04
.

With a mini-system, there are no good options. Speakers are not just 8 Ohms and, if they swing their impedance by much, any connection scenario can cause problems. Try a parallel connection and don't push the amp. Check to make sure the amp is not running hotter than normal. If you feel it is heating up, try the series connection and again check for excessive heat.



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New member
Username: Papang

Cancun, Q. Roo Mexico

Post Number: 1
Registered: Feb-15
Hi all!,

I have a Kenwood AV 550, 5 speaker system rated at 100w. RMS per channel in stereo. And yes I got it around 1996. I don't use it a lot, maybe the reason it is still chugging along, but I just recently rescued a Realistic Optimus Pro SW-14 passive sub-woofer rated at 100w.@ 8 ohms (12" speaker) .

The problem is that there is no connection for this speaker (s-woofer) on the receiver. I tried wiring as recommended, both front channels to the woofer and then one each to the 2 main speakers.This resulted in no measurable/noticeable improvement in sound as the woofer cutoff left the two 10" speakers of the 2 main speakers practically useless (almost no movement) only working with the 4" mid and 2" tweeter. This is the "safe" way to connect everything but I was wondering if I could do the following, NOT wanting to risk my antique amp with something lame-brained, but just get a bit of "better" sound:

--connect the woofer and the main speakers in parallel. In essence, wiring the left channel of one of the main speakers along with the left channel of the woofer, into the same channel connection of the receiver, and the same with the right. I figure impedance would be (8 ohms from main speaker + 1/2 of 8 ohms of woofer) 6 ohms (?) per channel.

The backplate of the receiver where the 2 connections for the 2 main front speakers says: "8-16 ohms". I have no idea what it means--maybe 2 - 8 ohms speakers per channel?

I have to admit I got a "D" in Principles of Electricity in college and this has cursed me all my life making it hard for me to understand AC & DC current hookups. As my system is pretty old, I am sure it has none of the modern day fail-safes of modern systems. I haven't even opened the case so I am not sure if fuses exist if the amp is overloaded.

I do play my system at over 50% (windows shake) but for the sake of better sound, I guess I could turn it down and if I wanted to turn it up, disconnect the sub-woofer. I have added a 6" DC fan to the cabinet to ventilate the receiver with fresh air to help it (via a surplus PSU-will add led background lighting later on connected to this psu) similar to overclocking a cpu.

Anyways, I just need some reassurance/comments about this connection. BTW, it is not easy to wire something in series as the speaker wires are hidden behind the walls of a recent home theater remodel. I could send a pic of this setup if necessary. Your help is much appreciated. Later.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18022
Registered: May-04
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Your math is showing your grade in Principles of Electricity. Two nominal eight Ohm loads placed in parallel will result in a combined load which is 1/2 the value of each. Assuming the Realistic sub is 8 Ohms nominal AND yoyr main speaker load is 8 Ohms, that would result in a 4 Ohm load as average. "Average" doesn't take into account the variables which occur in a real world speaker.

Bass frequencies are the most demanding of any amplifier and this load would be extremely taxing on the amp. Driving the load at window shaking volumes would likely shut down your amp - possibly forever.

A Realistic "sub" woofer isn't a subwoofer. Sorry, but their audio products simply aren't very good and their specs are meant to mislead the ignorant. The device might possibly add slightly more midbass sound to a system capable of driving a passive speaker system. That's not a "subwoofer" and you could achieve very much the same affect by shoving your existing speakers into the corners of the room. That's not the path to good sound quality IMO.

Buy a for-real subwoofer if you feel your system requires the deepest octave and one half to be present. Though, given the age of your receiver, I suspect you lack a LFE channel output. You're running what, Dolby Pro Logic? Without a dedicated effects output, your receiver is simply not going to provide the discrete low frequency information any subwoofer expects to be available today. But just adding more drivers to the system is not, IMO, the way to go. After almost 20 years, it's time to step into 21st century technology if you want 21st century sound.



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New member
Username: Papang

Cancun, Q. Roo Mexico

Post Number: 2
Registered: Feb-15
Thnx for your response Jan. And yes, I run Dolby Pro Logic most of the time, pretty neat in its time, he-he.

LFE? had to look it up (low few frequency effects channel) --what I need and the receiver lacks, probably not yet invented when I bought this system. I never saw a woofer connected to a system back then, just big speaker boxes with beefy 10-12" speakers. As a matter of fact, powered sub woofers were quite rare and super expensive too. If my woofer were powered, problem solved IMO. I would connect it the "safe" way (the two front speaker channels to the woofer and from the woofer to each front speaker) and get booming bass which is the where tastes have drifted nowadays. It would also mean that the 2 - 10" speakers of my front speakers would in effect be there for "show", not getting any frequencies to drive them as when I used the recommended connection for the Realistic and did my trials.

I agree that the Realistic is just a big heavy speaker with a cutoff for lower frequencies, something I should have suspected, overall, because of it being of the passive type. It's just embarrassing telling everyone that it is not connected and is "work in progress", sitting next to my stereo. It does look impressive and huge (compared to most itty-bitty/wimpy looking "home" powered woofers nowadays) but that is about it.

Another question. I have a 30w. basic Archer (Radio Shack again which is older (1990) and still works!) amplifier that I could use to power the woofer. I had been dallying with the idea except I have found no info to the respect. I know the easiest way is to buy a plate amplifier and tack it on/adapt to the woofer except they are not available here in Mexico. Living in Cancun just makes it worse for these type of things (luv the weather and the place tho). Any idea(s) about this? Maybe through the headphone plug (banana type but something can be adapted/invented). Like I said, there are just the 5 connections to the five speakers, none more. I suspect that if I use one of the 5 powered connections, it would be risky (?) like maybe using the center speaker connection. Or the 30w. amp is too wimpy? Distortion maybe?

I guess this would be my last idea/query to this respect, besides upgrading to something more modern down the road. As mentioned, this system still shakes windows, hehe, especially not being "upper tier" stuff. Words of wisdom are appreciated. Later
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18023
Registered: May-04
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When discussing "loudness" or SPL (sound pressure level) potential in a system, the amp is seldom the constraining factor. The single most important issue is the electrical "sensitivity" of the driver. If the sensitivity changees by +3dB with the same amount of wattage into the driver, you have the same (potential) situation as doubling the amp's wattage would give. That's simply loudness however and doesn't look at distortion or other non-linearities.

Low frequency drivers are, on average, the least efficient of the driver types. You typically need large driver surface areas and highly efficient motor assemblies for a (sub) woofer to rise above an average sensitivity spec. Gaining those two typically mean you will either discard low bass response or increase cost dramatically. Deep bass frequencies are rather dependent upon very large drivers is very large enclosures - refrigerator sized enclosures for the most part. There are some exceptions to the rule but I certainly wouldn't expect the Realistic box to be one of them.

I would not expect your wooofer's driver to be anything more than average in its specs. That would make a 30 watt amp very underpowered when paired with a 3 times as powerful main amp. And those are simply looking at the on paper numbers. Reality tends to be even less forgiving to the cheap brand of gear Radio Shack peddled. Even should you have success with the combination by drastically lowering your main system's volume levels, you would still have the issue of the Realistic system being just not well suited to producing much beyond midbass boom.

Best, IMO, to just live with what you have until it's time to update the entire system.



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New member
Username: Papang

Cancun, Q. Roo Mexico

Post Number: 3
Registered: Feb-15
Yes, I sort of figured that but was not sure. Thnx for clearing up most of my doubts.

HOWEVER, I bumped into a site where the author suggested using a a "speaker selector switch". I had no idea what these were nor how they were used but apparently, it is recommended over connecting multiple speakers in parallel or even in series, without the mess of rewiring the gaggle of speakers involved.

What I have available in Mexico is through the local Steren shop, something like Radio Shack also a franchise chain. They offer this:

http://imagenes.steren.com.mx/doctosMX/SEL-400-instr.pdf

and is priced at $420 pesos or around $29 usd. In your professional opinion (or very high hobby knowledge), would something like this do the trick? Also if you scroll down 10 pagesof the .pdf, they have an English version of the info which starts out in Spanish naturally. Is it enough to make a decision or at least, an educated guess? I recon quality is about as good as any Radio Shack product but cost a bit more ($20 vs $29 usd) but are pretty good on warranties altho if the selector should let the amp get damaged, I would be pretty much up the creek, I suppose.

Any insights on the idea? Thnx in advanced again.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18024
Registered: May-04
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Inexpensive switches like that place all speaker pairs in parallel. As far as the amp is concerned, no different than you hardwiring the system in parallel. The "protection" device is a large, ceramic, high value load resistor. There is minimal protection since the amp is forced to work harder to get through the device. These switches are best suited to background music systems played at low volume levels and not all speakers operating simultaneously.

You can try it if you care. The load will still be less than your receiver would prefer to work into. And it's cheap.

Just remember, it's cheap. REALLY cheap. And it's not ideal for a system that shakes windows.

Are you just that convinced you need more boom from your system? 'Cause the box you have isn't going to produce anything resembling deep bass. If you want deep bass from a subwoofer, you're going to have to have a subwoofer.


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