How does adding speakers in series, parallel, and combos affect acceptable volume? - AVS Forum
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post #1 of 10 Old 07-12-2009, 08:21 PM - Thread Starter
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I have always wondered this, but now I may need to put it to a real application. I want to put background music in my yard. 4 speakers would be "OK", 6 would be almost perfect, 8 would be maybe more than I need.

I'm trying to learn the science here and apply it to how it would make the system sound.

I know running 2 8 ohm speakers in parallel makes them a 4 ohm load. running them in series makes the amp see 16 ohms. Then if you want 4 speakers on the same channel, you can series 2 pair to 16 ohms, then parallel the 2 16 ohm pairs to get back to 8 ohms.

But will any of that actually make the music play louder with good quality more than the other or is it more about protecting the amp?

I have an old Sound Craftsman Pro Power 10 amp in great condition (not used much at any laod or volume at all). It has 4 channels 200wats each at 8 ohms, 400 at 4 ohms, and I read somewhere (not in the manual, on another forum) that it is stable at 2 ohms.

What exactly happens to the real world sound (volume and quality...if anything) if I were to go from 2 8 ohm speakers per channel, parallelled to 4 ohms...to 4 speakers per channel set up as above as a "series-parallel combo" to end up with 8 ohms to the amp? Which setup would play louder, or perhaps it better asked, which would allow you to occasionally crank it up for a party (still for ambiance, not for dancing...just louder enough to be heard above a large number of people who could still converse?

I cant imagine you could do this adding of speakers forever with more and more speakers, it seems eventually there wouldn't be enough "oomph" in the amp to power multiples of this (say 16, 24, 32 speakers). assume the speakers are all the same for now.

Put more simply, do 2 pairs in parallel play louder with the same quality at 4 ohms than a single pair a 8 ohms? (I know they would cover more area, but does each speaker you add take a little of the amps usable "volume production" or increase it because of the higher watts at less ohms?)

How about 3 pairs in parallel at 2.66 ohms? same question, is it a lot louder because of more watts, or less so because there is more speaker cone mass to move?

And do impedance matching speaker selectors like Niles and Russound decrease the overall volume available, or is it a moot point?

I do know that in the past, I have had the Russound controlling 3 pairs of 8 ohm Polks on 2 amp channels - with the other 2 channels powering 2 16" woofer, horn mid, and tweeters (big grey felt carpet covered "band" speakers by Cerwin Vega - dont know the ohms), and I could blow away the homes across the water. The band speakers weren't great quality, but loud and usefull in my younger, stupid days. The point is the amp seems strong, and I want to do the right thing by planning this in advance.

Anyone know anything that can help point me in the right direction?

Please feel free to point me to other links, but I've tried to find this out all over the web, and have been a member here so long I figured someone here may know...even if it isn't HT.

Thanks,

Jeff

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post #2 of 10 Old 07-13-2009, 07:08 AM
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Originally Posted by Jeff Smith View Post

I have always wondered this, but now I may need to put it to a real application. I want to put background music in my yard. 4 speakers would be "OK", 6 would be almost perfect, 8 would be maybe more than I need.

I'm trying to learn the science here and apply it to how it would make the system sound.

I know running 2 8 ohm speakers in parallel makes them a 4 ohm load. running them in series makes the amp see 16 ohms. Then if you want 4 speakers on the same channel, you can series 2 pair to 16 ohms, then parallel the 2 16 ohm pairs to get back to 8 ohms.

But will any of that actually make the music play louder with good quality

The general rule is that running more speakers in parallel will make things louder until you create a low impedance load that the amp can't handle.

Most receivers will drive 4 ohm loads no matter what their spec sheets say, particularly if you don't push the levels too high.

Loads under 4 ohms are a different matter, and really should only be used with pro audio amps and the few heavy duty consumer amps that are designed to go that route.

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more than the other or is it more about protecting the amp?

Modern amps are supposed to protect themselves. For example, I'm informed that some Sony amps will actually check out their speaker loads during power up, and flash a warning if the speaker loads are too much for it to comfortably handle.

More typically, excessively low speaker impedance loads will cause the power amp to actually put out less power before distorting, which is counter-productive.


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I have an old Sound Craftsman Pro Power 10 amp in great condition (not used much at any laod or volume at all). It has 4 channels 200wats each at 8 ohms, 400 at 4 ohms, and I read somewhere (not in the manual, on another forum) that it is stable at 2 ohms.

If its in good shape and meets original spec, that all might be true.

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What exactly happens to the real world sound (volume and quality...if anything) if I were to go from 2 8 ohm speakers per channel, parallelled to 4 ohms...to 4 speakers per channel set up as above as a "series-parallel combo" to end up with 8 ohms to the amp?

Hooking identical speakers in series creates a higher impedance load and will actually cut maximum loudness, all other things being equal. The power will be equally divided between the speakers, which will make life easier for them.

Hooking dissimilar speakers in series creates a higher impedance load and will also actually cut maximum loudness, all other things being equal. Unfortunately, the power will not be equally divided between the speakers, and can easily create a mess where the speakers just don't sound as good as they could.


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Which setup would play louder, or perhaps it better asked, which would allow you to occasionally crank it up for a party (still for ambiance, not for dancing...just louder enough to be heard above a large number of people who could still converse?

I'm not inexperienced enough to venture out and predict how things will work when you start cranking your stereo up at a party. If alcoholic beverages are served, then I'm running the other way really fast! I've seen a lot of equipment damaged that way. Your gun, your bullets, your toes! OTOH, your situation might be a picture of moderation, and no innocent audio gear may be harmed in the execution of your party.

What I will predict is that hooking speakers in parallel is a proven working methodology for making things louder, at least until you start breaking things.

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I cant imagine you could do this adding of speakers forever with more and more speakers, it seems eventually there wouldn't be enough "oomph" in the amp to power multiples of this (say 16, 24, 32 speakers).

You got that right!

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assume the speakers are all the same for now.

I doubt that you'll have any problems as long as you use the speakers and amps within their capabilities. To me that means that you will not create any effective loads for an amplifier channel that is less than 4 ohms.

It also means that no amplifier will ever be run into audible distortion in the judgement of a sober, experienced audiophile.

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Put more simply, do 2 pairs in parallel play louder with the same quality at 4 ohms than a single pair a 8 ohms?

As a rule, yes. Again this assumes that no amplifier will ever be run into audible distortion in the judgement of a sober, experienced audiophile.

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How about 3 pairs in parallel at 2.66 ohms? same question, is it a lot louder because of more watts, or less so because there is more speaker cone mass to move?

I would hesitate to try this with an el-cheapo receiver, but that heavy duty old SoundCraftsman might be up for it. Just blow the dust out of the heat sinks, keep it in a cool, well-ventilated place and put your hands on the heatsinks every once in a while.

Now, if you were talking about a modern Crown or QSC amp, or even one of the Berhinger EP-series power amps, I'd say go for it.

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And do impedance matching speaker selectors like Niles and Russound decrease the overall volume available, or is it a moot point?

They tend to err on the side of conservatism, which means that you might get louder results with wire strippers and wirenuts as your splitter devices.


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I do know that in the past, I have had the Russound controlling 3 pairs of 8 ohm Polks on 2 amp channels - with the other 2 channels powering 2 16" woofer, horn mid, and tweeters (big grey felt carpet covered "band" speakers by Cerwin Vega - dont know the ohms), and I could blow away the homes across the water. The band speakers weren't great quality, but loud and usefull in my younger, stupid days. The point is the amp seems strong, and I want to do the right thing by planning this in advance.

Sounds like nothing bad happens, so maybe you could stage a repeat engagement without breaking anything. But you're on your own!
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post #3 of 10 Old 07-13-2009, 10:25 AM - Thread Starter
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I want to thank you for this. I've been on the forum forever and this is one of the nicest and most honest yet comprehensive answers I've gotten in any sub-forum.

BTW - I'm 57 and way too old and wise to ever let anyone even know where the electronics are, let alone if they had a beer in their hand.

Thanks,

Jeff

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post #4 of 10 Old 07-13-2009, 10:39 AM - Thread Starter
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Oh, I forgot...do you have any thoughts on the wire size for such a long run and if that length affects impedance? Also, can I use outdoor UF cable, solid core, 12 gauge, 3 strand plus ground? The main question is about using the ground for the 4th "speaker wire". It doesn't have its own separate layer of color coded insulation, but the UV direct burial cable has all the wire molded into the plastic, not wrapped in paper and covered with an outer layer like indoor house wiring. I used calipers and the ground wire seems the same size as the other 3, and I would be extremely careful about insulating the bare ground wire in the short sections that would be exposed between where I strip the molded layer off and the amp and speaker binding posts. I only ask because I have over 100' of it laying around...easily enough to get to the first set of speakers.

Thanks,

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post #5 of 10 Old 07-13-2009, 02:03 PM
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Originally Posted by Jeff Smith View Post

Oh, I forgot...do you have any thoughts on the wire size for such a long run and if that length affects impedance?

In short lengths commonly used around the home, like 8 feet, speaker wire specs are less critical. IOW 24 guage is always a bad idea, and 12 guage is always a good idea. Evertyhing in-between slides along a scale of goodness.

Outdoors, where lengths can be a goodly number of tesn's of feet, more copper per foot is usually a good idea. Got some real-world lengths in mind?

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Also, can I use outdoor UF cable, solid core, 12 gauge, 3 strand plus ground?

Within reason, yes.

Quote:


The main question is about using the ground for the 4th "speaker wire". It doesn't have its own separate layer of color coded insulation, but the UV direct burial cable has all the wire molded into the plastic, not wrapped in paper and covered with an outer layer like indoor house wiring.

Sure, why not? In most audio gear the minus side of the speaker connections is connected to the amplifier or receiver's chassis ground.

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I used calipers and the ground wire seems the same size as the other 3,

That's code for most uses. Safety ground is the same gauge as the 2 hots and neutral.


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and I would be extremely careful about insulating the bare ground wire in the short sections that would be exposed between where I strip the molded layer off and the amp and speaker binding posts. I only ask because I have over 100' of it laying around...easily enough to get to the first set of speakers.

It should work.
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post #6 of 10 Old 07-13-2009, 04:12 PM - Thread Starter
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Thanks again.

Thanks,

Jeff

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post #7 of 10 Old 07-26-2009, 11:16 PM - Thread Starter
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Arnyk, if you're still out there, I have now run the basic wire and have some distances. The wire is 12 ga solid core UF direct burial cable (but still run in conduit in "dig prone" areas).

Its just about 100' to the first R speaker, 130' to the first L speaker. The distance to the last or furthest R speaker is about 160', and the furthest or last L speaker is about 190'. I only have enough 12 ga solid core to get to the first pair, so from there on I would have to buy more wire anyway and could either use the same solid core (if it were best to keep it uniform) or switch to 12 ga direct burial low voltage stranded cable if you advise.

I would love to be able to run 3 speakers per side (8 ohms each) and wondered if the wire length would actually help the amp by adding to the (calculated) 2.67 ohms? I saw you mention this on another thread. This would be the ideal number speakers for the area. I'll try to google a calculation for how much resistance per foot 12 ga solid or stranded wire adds, but didn't know if the entire length counted, or just the distance to the first speaker on L and R.

Also, whats wrong with just adding a 1 or 1.5 ohm resistor to each side to bring the resistance up to 3.67 (plus wire)? Granted its power wasted, but it still should play louder than 4 speakers per side (8 total) at 8 ohms...or am I off base there?

If I had to put in 4 per side (8 total in series/parallel = 8 ohms) I would do so - if strongly advised - but its extra money wasted if not needed for the amp's protection.

Either way the total wire length would be about the same, as I would just place the 4 per side closer together.

Is it fair to just ask what would most likely sound better (granted, its an EWAG - or educated wild ass guess)...the 8 speakers at 8 ohms to the amp dividing 200 watts/channel, or the 6 speakers at 2.67 ohms (plus wire plus resistor if you suggest) at 3.67-4 ohms to the amp at 400 watts per channel divided?

I did just order 4 speakers, and will try them 1st, and I may experiment with 3 and 4 on a single channel in the combo's above.

I have the original Sound Craftsman manual, but it doesn't say much about how to tell you're too low on ohms, or protection circuits, etc. I really don't want to kill it trying.

Thanks,

Jeff

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post #8 of 10 Old 07-27-2009, 06:03 AM
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Quote:
Originally Posted by Jeff Smith View Post

Is it fair to just ask what would most likely sound better (granted, its an EWAG - or educated wild ass guess)...the 8 speakers at 8 ohms to the amp dividing 200 watts/channel, or the 6 speakers at 2.67 ohms (plus wire plus resistor if you suggest) at 3.67-4 ohms to the amp at 400 watts per channel divided?

I would not add series resistance. The speaker cable will add some, but not a whole lot, probably about 1/2 ohm or so.

If this is mainly for background music, IMO, don't get too hung up on the 200W or 400W. Those are only the max power ratings, of which you'll be using a mere watt or two most of the time, maybe even less, if the use truly is ambiance/backrgound level where people can still converse easily.

If this is a large area, you might be better served by more speakers producing a more uniform coverage than less speakers where you might tend to play them louder trying to cover the same area, IMHO.

OTOH, impedance matching volume controls might not be a bad idea. That way you have some control over balancing the volume of the speakers, perhaps for creating quieter or louder zones as the need arises.

Just because there is a knob doesn't mean you should turn it.
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post #9 of 10 Old 07-27-2009, 07:43 PM
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Yes, you can use all 4 conductors in outdoor UF 12-3 cable for speaker wires. But, running long speaker wires through a metal conduit may cause problems with some poorly designed amplifiers.

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post #10 of 10 Old 07-27-2009, 08:53 PM
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You could try 2 speakers in series, then those 2 in parallel with one additional speaker, to get the impedance more in line with what home amps expect to see. But I think you'll get mismatched volume levels between the parallel pair and the series single - - whether it's enough to matter is a question I can't answer.
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