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Author Topic:   Speaker Wiring (Shore based)
David Jenkins posted 12-16-2005 11:30 AM ET (US)   Profile for David Jenkins   Send Email to David Jenkins  
I want to be able to listen to music from my home stereo system while I am outside working on the Boston Whaler.

The problem is that my inexpensive KLH stereo receiver/amplifier only has outputs for one set of speakers. Speaker selector boxes range in price from $40 (Radio Shack) to $80 (Circuit City). I think that the receiver itself only cost $100 so I am reluctant to spend that much on an accessory that will allow me to add another set of speakers.

What would happen if I added the second set of speakers by inserting into the back of the amplifier the new speaker wires alongside the existing wires?

The speakers are all 8 OHMS, and the amplifier recommends using 8 OHMS speakers. Will my output still be 8 OHMS if I double up the wires?

I apologize in advance for asking this off-topic question. But the salesman at Circuit City recommended that I do this if I was too cheap to buy his $80 speaker selector box and I knew that someone here would be able to tell me in an instant if this setup could damage my speakers or amplifier, or if the worst that might happen is that I would have some loss of sound quality.


Buckda posted 12-16-2005 11:46 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Don't know if it damages your amp or not, but certainly not your speakers.

I did this all the time in College and High long as the speakers are at equal impedance, you should not have a problem. I'm still using the same amplifier I bought as a Senior in High School in my bedroom and it works fine. The receiver/amplifier set I bought in College still does serious duty in my living room, and delivers the same high-quality sound that it did when it was new, powering 5 channels of sound and driving an amplified anecdotally, what you suggest has not damaged a Yamaha preamp in 15 years of regular use, and has not damaged an Onkyo receiver/amplifier in about 7 years of heavy use.

It's not the "best" way to set it up, but since you have an inexpensive system in the first place, my guess is that you're just concerned that you don't blow things up, rather than being proper.

You should be fine.


David Jenkins posted 12-16-2005 11:49 AM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
That is what I had hoped you would advise. Thanks!
Jerry Townsend posted 12-16-2005 01:17 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
David - paralleling additional speakers to an amplifier will present an increased load to the amplifier and is, in all probability, not recommended by the amplifier's manufacturer. Amplifiers are designed for a given load (impedance / resistance).

One might be able to get by with 'hanging additional speakers' with some amplifiers, while others might 'crash and burn'. And, of course, it depends on the speaker(s) as well - little 'dinky' speakers don't draw as much power as big, multi-speaker enclosures. Try it and listen to each of the speakers when 1) someone connects in the additional speakers and 2) after all speakers have been operating for some time - to see if the sound is distorted which would be indicative of the amplifier having problems. --- Jerry/Idaho

Buckda posted 12-16-2005 01:32 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Good point Jerry -

Having efficient (expensive) speakers is a plus.

My speakers at that time in my audiophile-crazed life, were all 4 OHM impedance - in some cases, I had installed new crossovers to make it so, meaning that even if I doubled the impedence, it was within the 8 ohm range for my fairly high quality amplifier (which may also have something to do with the survival of the amp with doubled up impedance).

But 8 Ohm impedance with doubled up speakers would mean that your amp is pushing 16 ohms resistance rather than the 8 ohms. Couple that with a lower-quality amplifier and it is possible that you may overheat or damage the equipment.

David -

One other thought...since your amp was only $100 in the first place, and the speaker selector switch can cost as high as $80, it would be money better spent to just buy another amp; or don't worry about it for now and replace the amp if you do damage it.

I still don't think it will damage your amp, unless you're a big Metallica fan and want to really rock when you're wrenching on the Whaler, or worse, listening to classical music on a very loud volume (Classical music requires the very best system, from speakers all the way to amplifiers, in order to sound good). If you're just piping in sound at a normal level, I don't believe you will damage your amp (other than it may run a bit hotter).

David Jenkins posted 12-16-2005 01:47 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
These are Optimus Pro-X55AV speakers from Radio Shack. They are about 8 inches high, 5 inches wide and 4 inches deep. They probably weigh 10 pounds each. Power handling is 70 W (RMS) and maximum power is 140 W.

The receiver amplifier is a cheap thing that I bought from Wal-mart. I would normally follow the manufacturer's recommedation but I hate to buy a $40 plus tax speaker selector box when I could probably spend $100 and get a brand new receiver with built-in capability to power 2 sets of speakers.

I also want to use a $400 Yamaha subwoofer in this arrangement. So I was thinking that I would have one set of wires go to the subwoofer, then I would push the two sets of speakers (with the parallel wires) from the subwoofers' single pair of "speaker out" ports.

Is this going to put my subwoofer at risk?

Would my subwoofer be safer if I ran the parallel speaker wires out of it or would the subwoofer be safer if I had the parallel wires come out of the receiver/amplifier and then I just ran one pair of the wires to the subwoofer on the way to one pair of speakers?

Am I making any sense at all?

If you are taking the trouble to read this, thank you for trying to help me!

Buckda posted 12-16-2005 01:56 PM ET (US)     Profile for Buckda  Send Email to Buckda     
I'd rather overload a $100 amp than the amp on my $400 amplified subwoofer. run the extra impedance off the $100 amp, and if she does die on you, consider it a good opportunity to get a better amp (with the ability to select A/B or subroom speakers.

Buckda posted 12-16-2005 01:58 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Also - running the wires for the extra speakers from your subwoofer amp will adversely affect the quality of sound (richness) from those speakers. It probably has a built in crossover in it that is diverting the lower frequencies to the subwoofer and only sending the higher frequencies to the bookshelf speakers.
Chuck Tribolet posted 12-16-2005 01:58 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
If you parallel two 8 ohm speakers, you have 4 ohms, not 16
ohms. The low resistance will cause the amplifier to
flow more current, and that might blow something.

Does the amp have an Aux output? You could look around for
some wireless speakers.


David Jenkins posted 12-16-2005 02:08 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
The receiver/amplifier has left and right RCA-type outputs called "PRE OUT" in addition to the crimp-wire outputs for a pair of speakers. And my Yamaha subwoofer does have inputs for an RCA-type plug as well as inputs for speaker wire. Wow! Maybe that is the solution.I have had this system for years and am just now realizing this. I will experiment with it now....
David Jenkins posted 12-16-2005 02:34 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
No luck with that idea. The speaker wire outputs on the amplifier get no power unless the PRE OUT port is plugged with a u-shaped piece of metal/plastic that connects it to the RCA-type port next to it which is labeled AMP IN.

I don't understand any of this. Maybe I should just go buy a new amplifier/receiver. I don't care about hurting the old one but I don't want to take a chance with harming the subwoofer or speakers....

David Jenkins posted 12-16-2005 03:03 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
I hooked it up as Buckda suggested (but without the subwoofer). Sounds good but I have to crank the volume up higher than I would have expected. Maybe that is because the amp is now having to work twice as hard?

The Altec-Lansing speakers that are connected directly to the Mac sound a bit better and are louder and have absolutely no hiss during moments of silence, but maybe that is because they have their subwoofer connected and are specifically designed to receive music from a computer-type device and software like iTunes.

Thank to everyone who provided assistance.

David Jenkins posted 12-16-2005 04:15 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Last follow up:

I trimmed the ends of all the wires to get fresh, shiny speaker wire on all of the connections, hooked up the subwoofer as suggested above, and it sounds great.

So now you can delete this off-topic article, Jim. Thanks!

where2 posted 12-16-2005 07:10 PM ET (US)     Profile for where2  Send Email to where2     
You could use the "Pre-Out" if you bought two "Y" adapters with 2 male and 1 female end. The two males would act as a jumper like the "U" shaped wire, and allow you to attach a male-male RCA cable to each "pre-out" before it is amplified. Attach your RCA cable to the female connection of each "Y" and to the subwoofer input. The "U" you removed just takes the center lead from one RCA jack and inserts it into the adjacent connector.

Happy Holidays (a former radio shack employee)

WT posted 12-16-2005 07:32 PM ET (US)     Profile for WT  Send Email to WT     
I thought impedance could be corrected with Viagra. :)
David Jenkins posted 12-16-2005 10:17 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Thanks, where2. I'll drop by Radio Shack ASAP.
swist posted 12-17-2005 12:21 PM ET (US)     Profile for swist  Send Email to swist     
I am an old f*rt but used to know my electronics well. Do not confuse impedance with resistance - it is only part that - think of it as AC resistance at a certain frequency. As a extreme example - think of your 50 ohm coaxial cable connecting a transmitter to an antenna - you can't put a regular DC ohmmeter anywhere in that configuration and read 50 ohms. Connecting something designed for one impedance to a different one can not only change the loading on the driving device (and hence possible loss of power), but may also impact the signal quality because the circuit was tuned to optimze a certain frequency range.

Now it may be the case that (a) it doesn't matter much at audio frequencies on a boat, and (b) newer amplifiers have high tech solid state output stages that behave very differently from the old transformer-based designs (and I'm guessing that the former tolerate impedance mismatches better).

davej14 posted 12-17-2005 02:58 PM ET (US)     Profile for davej14  Send Email to davej14     
Might as well add my $.02 to this discussion.

First of all you didn't say if you needed to listen in both locations at the same time. If not, then just get a cheap single pole double throw (3-way) switch and connect the common pole to either of your amps speaker outputs. Then connect your house speakers to one side of the switched output and the garage speakers to the other side of the switched output. For the other polarity just twist the garage and house wires together and connect them in common to the other speaker output on your amp. You can then switch between the two locations.

If you just connect the 8 Ohm speakers in parallel you will be lowering their total impedance to 4 Ohms. This will result in a higher current draw from your amp which may or may not be a problem. At lower volumes you would be safe, but as you crank it up you could damage the amp or the speakers. The amp could be damaged because you could exceed the current rating of the output stage. The speakers could be damaged because you could be clipping the audio out and generating noise. Speakers, particularly the tweeters and mid range drivers, are not designed to handle continuous distortion which increases the average power delivered to them vs a pure audio signal. They could overheat in a short period of time and be damaged.

where2 posted 12-17-2005 10:58 PM ET (US)     Profile for where2  Send Email to where2     
Davej14: Actually, I typed up a rather lengthy response with that DPDT (double pole, double throw) switch concept last night, before I realized he had the ability to bi-amplify using the subwoofer. I scraped the low budget speaker selector switch in favor of bi-amplification.

Rather than a SPDT (Single Pole, Double Throw), I think you'd want a DPDT since it's a stereo receiver. Good call though. The switch in a speaker selector box is not an elaborate switch. The grounds can all certainly be tied to one another.

davej14 posted 12-18-2005 11:39 AM ET (US)     Profile for davej14  Send Email to davej14     
Where2, you are correct, DPDT due to stereo. It makes for a pretty low cost solution.
prm1177 posted 12-20-2005 07:58 PM ET (US)     Profile for prm1177  Send Email to prm1177     
The calcularion for the combined impedance of multiple speaker is as follows:

In series (amp + to SP1 +, SP1 - to SP2 +, SP2 - to amp -) is simple the sum of the impedances (4 Ohms + 8 Ohms = 12 Ohms).

In parallel, it is the reciprocal of the sum of reciprocals. In other words 1/(1/SP1 + 1/SP2) where SP 1&2 are the speakers' impedances. In this instance, paralleling a 4 Ohm and 8 Ohm speaker will get you 2.67 Ohms in impedance.

Many switch boxes either have a ballast resister (usually 2 Ohms) in series with the speakers them to raise the impedance to a minimal level (4 Ohms) or else the more expensive ones place an impedance matching transformer in the way.

David Jenkins posted 12-20-2005 11:14 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Do I risk hurting the speakers or the subwoofer by running two 8-ohm speakers in parallel (if that is the right term)? Actually, one of the speakers is coming off of the subwoofer, but the subwoofer is still wired in parallel with the other pair of speakers. Will putting the subwoofer and one set of speakers on the "U" split mentioned above reduce the risk of harming the equiptment? Or should I just go by a speaker selector box? Is the expensive ($80) speaker selector box worth the money or would I be okay with the $40 box? Thanks.
davej14 posted 12-21-2005 10:34 AM ET (US)     Profile for davej14  Send Email to davej14     

Yes, it is possible to damage the amp and the speakers.

You started out saying you had a $100.00 cheap amp and didn't want to spend unnecessary money to accomplish a modest goal of switching between two sets of speakers. A simple low cost DPDT switch will accomplish that for about $5.00. Unless you are looking to listen to both sets of speakers at the same time this is all you need. If you want to listen to both sets at the same time then you also need to get a volume control for at least one set of speakers and you may find your amplifier is not up to the task.

I personally wouldn't recommend spending $80.00 to be able to switch between two speakers because you will still have a low cost amp. Do yourself a favor and buy a better amp with two sets of speaker outputs. A Yamaha RX-397 receiver for $250.00 would be a good choice. You even get a remote and the benefit of AM/FM.

jimh posted 12-23-2005 12:48 AM ET (US)     Profile for jimh  Send Email to jimh     
Even most cheapo AM-FM receivers have a speaker selector.

Be sure to use Monster cable for low distortion. (I am kidding.)

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