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explain parallel speaker cable current activity...please.

post #1 of 16
12/18/04 at 10:56pm
Thread Starter 
OK I'm an uneducated dolt regarding electricity.

A friend suggested a way I could run my subwoofer off my integrated amp.
Two pairs of speaker cables attached to the amp's binding posts, one pair to the main speakers and one pair to the sub (not from sub to main speakers!).
And it worked like a charm! Perfect.
I always thought of the volume control as turning a faucet and water/electricity flowing. I know where the flow to the main speakers is going. But the flow/electricity/signal to the sub's amp is going where? Back to the integrated amp unused? Is it bouncing back and forth down all lines and only "used" where a door is open sufficiently or enough?
Thanks
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post #2 of 16
12/18/04 at 11:39pm
if I am understanding what you are saying what you are doing is using a single amp to drive your main left and right channel speakers plus your subwoofer.

This is no different than driving any other loudspeaker that uses multiple drivers except they are not in the same cabinet.The sub has its own crossover right ?
If so it is only reproducing the freqeuncy band it was designed for just like the tweeter is only reproducing the frequency bad its crossover allows.

the only potential problem I can think of is the total parallel ohmage the amplifier "sees".

Two eight ohm loads in parallel equals four ohms and that can put a strain on an amp not designed to handle low impedance loads.If it has V/A protection it can trigger it repeatedly while playing music which sounds like "clicks" in most cases.If not it clip on demanding passages and take out the tweeters.worst case it can self destruct and take the entire output stage out.

If the amp can handle the load gracefully-cool
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post #3 of 16
12/18/04 at 11:56pm
Thread Starter 
Hi Rick.
I had these questions myself. I was Q&Aing with Michael Jones(Editor
18 years of audioenz). It was his idea to run two pairs.

"You will need to run two sets of speaker cable from your amp - one to the ATC speakers and one to the PSB sub."
"Whatever you do, do not run speaker cables from the sub to your ATC speakers (ie, using the PSB's internal crossover. You'll suck all of the goodness out of your hi-fi."
Michael Jones

After much thanks for saving me a bundle of cash with minimal equipment complications.
"I have just a few lingering, nagging questions regarding the set up Michael.
Will the amp be seeing anything differently as in no longer seeing an 8 ohm load (main speakers) and now seeing a 4 ohm load?
Will the main speakers be receiving any less current?
At 85 dB my speakers like all the juice they can get.
There will be no trade offs at all?"
Me

"This depends a lot on the input impedence of the subwoofer. Remember, your amp is not driving the speaker in the subwoofer, but is instead supplying a voltage signal (I think that's right) to the amp built into the subwoofer. There's no reason why the input impedence of the sub should be so low and affect the amp as if it were another speaker."
M.Jones

Will the main speakers be receiving any less current?
Me
Shouldn't be a problem.
MJ
There will be no trade offs at all?
Me
Shouldn't be. Just remember to keep the crossover frequency on the sub low, so you don't get much (or any) overlap. Otherwise the sound may go a bit boomy.
Mj

And afterwards I remembered that REL subs use this very same hook-up, so I felt reassured. I am planning to ask ATC just to be extra cautious. I did not receive a reply from PSB to the question, which is unusual as they are usually are good at that.
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post #4 of 16
12/19/04 at 12:06am
Thread Starter 
Quote:
Originally Posted by rickcr42
If the amp can handle the load gracefully-cool
Well I have rocked the place for two weeks without a hint of clipping to be heard. And I do mean rocked! So grace is present but I am a worry wart if I don't understand fully what is happening physically with the gear.
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post #5 of 16
12/19/04 at 12:22am
Are you sure you didn't use the speaker level inputs on the sub amp? If that's the case, the impedance/resistance on that input is very high. It doesn't take hardly anything from your main speakers, certifiably negligible.
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post #6 of 16
12/19/04 at 12:25am
Thread Starter 
Quote:
Originally Posted by ooheadsoo
Are you sure you didn't use the speaker level inputs on the sub amp? If that's the case, the impedance/resistance on that input is very high. It doesn't take hardly anything from your main speakers, certifiably negligible.
Yes. The sub's high-level input/binding posts. Not RCA.
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post #7 of 16
12/19/04 at 12:36am
Right, that's different from what Rick was mentioning. He thought you were driving the subwoofer with your amp. That's not the case. Take your faucet example. The speakers have a hose hooked up but there's a "y" adaptor and there's this tiny dinky little straw sized hose going to the sub amp because of the high resistance/impedance.
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post #8 of 16
12/19/04 at 12:42am
heh,left a party about an hour ago so a bit 'fuzzy".Bear with me here....

anyway-the parallel impedance i spoke of is if the sub was a passive sub.A powered sub is another beast entirely.

two speakers in parallel divide by two.Two speakers in series "add' instead of divide so two eights in series equal sixteen ohms.

BUT .

In the case of a powered sub the input is a resistor network that shows a high impedance (in the thousands of ohms) to the amp while being invisible to the speaker.This network converts "speaker level" to "line level" and because of the high impedace is no load on the amp which in effect is now a line level device and only has to produce voltage drive,which is easy,instead of current drive to a speaker,which is not easy and determines how much power in WATTS it produces into a load in ohms.

Not sure how coherent that was but bottom line,a powered sub is not a strain on a power amp but parallel speakers are
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post #9 of 16
12/19/04 at 12:47am
Thread Starter 
Quote:
Originally Posted by ooheadsoo
Right, that's different from what Rick was mentioning. He thought you were driving the subwoofer with your amp. That's not the case. Take your faucet example. The speakers have a hose hooked up but there's a "y" adaptor and there's this tiny dinky little straw sized hose going to the sub amp because of the high resistance/impedance.
Thanks Abe

So if I did use the speaker cable out of the sub to mainspeaker option (which I will not) the current would just flow through/past the sub amp with just a trickle amount of signal being actually used by the sub amp? But as it is now the current is barely there somehow.

With all this faucet-flow-trickle talk I don't know if I'd rather go to the kitchen or bathroom!
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post #10 of 16
12/19/04 at 12:58am
Thread Starter 
Quote:
Originally Posted by rickcr42
In the case of a powered sub the input is a resistor network that shows a high impedance (in the thousands of ohms) to the amp while being invisible to the speaker.This network converts "speaker level" to "line level" and because of the high impedace is no load on the amp which in effect is now a line level device and only has to produce voltage drive,which is easy,instead of current drive to a speaker,which is not easy and determines how much power in WATTS it produces into a load in ohms.

Not sure how coherent that was but bottom line,a powered sub is not a strain on a power amp but parallel speakers are
The integrated amp is totally unaffected by having a powered sub hooked by highlevel sub binding posts then I take it?

(And I must say the only discomfort I had when banned was being unable to make a fun comical comment on the fact that a professional "banger of nails" had as his avatar some sort of 5 thumbed, thumb creature! That was killing me).
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post #11 of 16
12/19/04 at 1:12am
Quote:
The integrated amp is totally unaffected by having a powered sub hooked by highlevel sub binding posts then I take it?

Exactly.The impedance is so high it takes no current to drive it but voltage only.A low impedance device such as a loudspeaker needs muscle to move the cone and that is current.even a speaker rated at 8 ohms may hit 2 or 4 at various points in frequency because of the crossover/driver interaction and can stress some amps.

Quote:
nd I must say the only discomfort I had when banned was being unable to make comment on the fact that a professional "banger of nails" had as his avatar some sort of 5 thumbed, thumb creature! That was killing me).
you have been around long enough to know i like irony and the layers of meaning attached to anything I post but the funny thing is,no one ever asked me what my avatar was and just assumed it was some kind of big headed super hero (kinda like me ).

but the reality was it was the RCA radiotron guy and the "head" was a tube !

It was also the inspiration for my signature which also was a double meaning.

the "R" on my chest is a reference to a saying we have around here when a person has issues and whines like a whimper baby instead of just letting it go or taking care of business.

"Put an H on your chast and handle it" is the first part

"or be a punk,means nothing to me either way"is part 2

so i went with the big R and the "cool cape"

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post #12 of 16
12/19/04 at 1:20am
Thread Starter 
Quote:
Originally Posted by rickcr42
but the reality was it was the RCA radiotron guy and the "head" was a tube !
OH...I could have sworn it was an all thumbs creature. The irony! As I said it was killing me.

Anyways thanks Rick, thanks Abe.
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post #13 of 16
12/19/04 at 5:13am
No biggie. Rick here did most the heavy lifting
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post #14 of 16
12/19/04 at 5:39am
i have the same set up too.

sophia el34 -- dh labs Q10 feeding the silverline sr11 monitors -- and anothwer set of speaker cable to speaher / line level converter cable to the sub's line in( i think)
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post #15 of 16
12/19/04 at 3:54pm
Thread Starter 
Quote:
Originally Posted by screwdriver
i have the same set up too.

sophia el34 -- dh labs Q10 feeding the silverline sr11 monitors -- and anothwer set of speaker cable to speaher / line level converter cable to the sub's line in( i think)
I saw one of those connectors somewhere. Interesting.
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