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Passive Speakers In Parallel


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For a bit of background info, I volunteer for a local youth cafe who need a small sound system upgrade.

 

I've suggested two small subs, two small tops and a single amp. Only thing I don't use passive speakers so connecting in parallel goes right over my head. My question is;

 

If I have 2 subs at 200w RMS, 8 ohms...

And 2 speakers at 100w RMS, 8 ohms...

And an amplifier at 300w RMS per channel at 4 ohms...

Will it work?

Without anything blowing up I mean?

 

I know that putting speakers of the same impedance in parallel halves the impedance. But my main concern is that, by looking at the whole set up... let's say one of my subs are putting out 150w of the 300w, won't the top (connected to it in parallel) be putting out 150w as well? What I mean is does the amount of power distribute itself evenly between both speakers, or does it balance depending on what each speaker is capable of? Like I said it all confuses me.

 

Help would be much appreciated, so thanks in advance! :)

 

D.

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So you're saying it won't work?

 

In which case i'd be better off with 2 x 200w subs and 2 x 200w tops... or 2 x 150w subs and 2 x 150w tops? Either way, as long as the top and bottom can each cope with half the output power? That sucks somewhat. Ah well. Thanks anyway =)

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Yep agree with spinner.

 

If your top cabs are rated 100W, then connecting them in parallel with 200W bass bins will mean you must restrict the output to 100W...so either underdrive the bass bins (wasting money) or overdrive the tops (and possibly overheat them).

 

Any retailer worth their salt will have what we call 4-box setups which comprise 2 tops and 2 bins which are designed to work as a foursome off one amp.

 

If you want to mix and match your cabinets then I suggest you get seperate amps for both so you can have a better idea of what you're forcing into them.

 

Speakers arent like light bulbs..a 100W speaker wont consume 100W if put on a 500W amp, the amp will try to force 500W through the 100W speaker much to its detriment.

 

Ive said it before...pro sound systems arent plug and play!

 

 

 

 

 

 

.

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Thanks guys. They've backed out of going for a new setup anyway. Otherwise it was just gonna be a case of four 150w RMS speakers from a 300w RMS per channel amp. I mean I've never been stupid daring enough to drive speakers with any more power than what they can handle. Just didn't quite understand how the power would be distributed with speakers in parallel... until now. But it's certainly useful information. Thanks again =)

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  • 2 weeks later...
If your top cabs are rated 100W, then connecting them in parallel with 200W bass bins will mean you must restrict the output to 100W...so either underdrive the bass bins (wasting money) or overdrive the tops (and possibly overheat them).

 

No you don't really, unless you're going to go start playing sine waves through the rig.

 

150w into a 100w rms rated cab should be fine so long as you don't go clipping the amp.

 

Even running flat out the average power the speaker is likely to see will be 90w or so.

 

'Restricting the output to 100w' would be just about impossible anyway.

DIY plans and pro audio related technical discussions

www.speakerplans.com/forum

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I know, my answer was simply to illustrate the problems that mismatched speakers can pose.

 

But we can't go saying that this setup will be fine otherwise someone will then say that the 150W bass bin is underpowered by the 100W amp!

 

We're best making people aware of how their system deviates from the ideal and let them decide if they want to run it this way or that.

 

I dont want the OP to assume that a 100W speaker will magically become a 150W speaker by shoving 150W through it. It will still be a 100W speaker! That's assuming its marked in proper watts and not disco-speaker watts.

 

Slow and steady wins the race!

 

 

 

 

 

 

 

 

.

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I dont want the OP to assume that a 100W speaker will magically become a 150W speaker by shoving 150W through it. It will still be a 100W speaker!

 

Absolutely, but I think there is value in detailing why the numbers don't equate equally between amp output and speaker RMS rating, how musical signal is different from test sine waves, how speaker ratings are actually devised, etc, etc

 

Unfortunately it's a big subject, but I think dumbing it down only leads to misinformation and misunderstanding about what is 'safe' and what are the causes of loudspeaker failure.

 

I think if there was one thing I'd advise anyone, it's 'do not clip your amps'.

DIY plans and pro audio related technical discussions

www.speakerplans.com/forum

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