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AUDIO FORUMS >> General Discussion and Support >> Two Pairs of Speakers From One Stereo Amp?...
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Message started by Mark on 07/19/18 at 15:52:57

Title: Two Pairs of Speakers From One Stereo Amp?...
Post by Mark on 07/19/18 at 15:52:57

I've often wondered what would happen if one were to hook two pairs of speakers up to, let's say, one SE 84 UFO amplifier...

For argument's sake, lets say that both pairs were nominal 8 ohm impedance... One pair of speakers hooked to amp with banana plugs, the other pair with spade lugs...

What nominal impedance would the amplifier 'see'?...

Would two pairs play louder than one pair?...

Could it work at all?...

Would the amp suffer, either immediately, or in the long run?...

Would you have to take pains to make sure that the two pairs were providing a coherent sound wave-front?... (m.)

Title: Re: Two Pairs of Speakers From One Stereo Amp?...
Post by deucekazoo on 07/19/18 at 16:42:26

So that would be a series load, the amp would see a 4 ohm speaker.
These amps love a 4 ohm load.
You will run into a few issues. The main one would be the combing affect. Where the frequency from one driver starts to cancel out the frequency from the other driver. This is an issue you run into with line array speakers and that is why you need to put the drivers as close together as possible.
I have done what you want to do with bookshelf speakers before, just to see what would happen. I flipped the second pair of speakers on top of the first pair to have the tweeters close together. So I actually made a MTM speaker. Truthfully it sounder better, fuller with both of them playing than with just one.
I even have a friend that is actually running two different makes of speakers as one and loves the sound. Give it a shot and see.

Title: Re: Two Pairs of Speakers From One Stereo Amp?...
Post by Lonely Raven on 07/19/18 at 20:37:36

BZZZZT. Thank you for playing DK.

That would be a parallel load and would drop the (nominal) impedance to 4ohms. So you got it half right. :P

You'll get more volume with more drivers and lower impedance. I shouldn't hurt anything. The results really depend on too many factors, so try it out and see!!

Title: Re: Two Pairs of Speakers From One Stereo Amp?...
Post by deucekazoo on 07/19/18 at 20:52:33

Oh sh*t I meant parallel load. I think I need to start drinking.

Title: Re: Two Pairs of Speakers From One Stereo Amp?...
Post by Mark on 07/19/18 at 21:27:47

Hmmm... Just thought of something: If the efficiency disparity was too much, you'd be getting a lot more sound from one set of speakers vs. the other pair... So, the efficiency of each pair should be close, no?...

Also, there was something else I discovered as an audio salesman way back... And that was that the woofers on one pair of live speakers would affect the movement of other woofers on speakers that were near, but not energized... I mean, the un-energized pair woofers would move out of phase with the live pair... In other words, they'd sorta act like passive woofers, which some speaker designers use in their enclosures...

So there's a lot to consider here... I've often wondered what effect all those speakers in Steve's soundroom(s) have when one pair is cranked up, but the others are just sitting there... It simply has to affect the overall sound, no?... I mean, if you do a test, you can see the dead woofers moving sympathetically with the live ones... I've seen this myself...

Then there's the issue of hooking up a sub or aux. bass speaker directly to the same terminals on the amp... That would bear on the same issue at hand here, no?...

Anyway, thoughts welcome here... (m.)

Title: Re: Two Pairs of Speakers From One Stereo Amp?...
Post by Mark on 07/19/18 at 21:35:17

BTW, deuce, I've done the speaker stacking thing with Advent speakers... Oddly enough, they were called ' Stacked Advents '... Go figure... Top pair upside down to make the tweeters close together... They sounded pretty good... And of course, it brings me right around to the original issue of how they were hooked up... Could have been off the 'B' speaker terminals...

At amy rate, I was particularly curious to know what would specifically happen to a Decware SE 84 UFO amp if you ran two pairs of speakers off of the one pair of terminals... As in, was there anything in the proprietary circuitry of the amp that might make it a problem?... (m.)

Title: Re: Two Pairs of Speakers From One Stereo Amp?...
Post by Lin on 07/19/18 at 23:33:29

Several years ago I used an older SE84B with a 1.5 ohm (nominal) load.