How to use speaker A+B at the same time.

[izeek]

I have seen several kits where there were say a set of towers and a set of bookshelves or even another floorstander that looked like they were being used at the same time. I know looks are decieving.
Are folks using 4 amps? I'm sure there are several possibilities.
I've also read some using both speaker A and B at the same time.
Lets say one set is 6 ohms and the other set is 8 ohms. How's that work?
And if, in fact , it is four speakers running, how to get them to sing the same song.

 

[mhardy6647]

The traditional way to do it is in parallel.
Impedances (Z) in parallel add thus: 1/Zt = 1/(1/Z1 +1/Z2 + ...)
connecting 8 and a 6 ohm (nominal!) impedance loudspeakers in series [EDIT: parallel; thanks @Jim Taylor!] will present a nominal load impedance of 1/(1/8 + 1/6) = 3.429 (ish) ohms.

If one's amp is happy with a low impedance load, that's the "better" way to do it.
If either of the loudspeakers' actual impedance curves tend to make them harder to drive, it will be harder for the amplifier to provide them with adequate current -- in extreme cases, shutdown of the amp, or even damage, could result.

It is also possible to connect loudspeakers in series: Zt = Z1 + Z2 + ... when the loudspeakers ("loads") are connected in series. Easier (at least on paper) for the amplifier to drive; but the signal has to flow through an extra reactive component ("speaker 1") en route to "speaker 2"... which, a priori, ain't a great idea. It will work, though.

A random image from the web showing series vs. parallel connection of 8 ohm speakers and the resultant impedance(s).
the little "loop"going across the "-" wire in the top speaker in the LEFT image means there is no connection between that wire and the "-" wire underneath it (in case that's not obvious).

http://www.bass-guitar-info.com/SpeakerWiring.html

 

[Deleted member 21219]

connecting 8 and a 6 ohm (nominal!) impedance loudspeakers in series will present a nominal load impedance of 1/(1/8 + 1/6) = 3.429 (ish) ohms.

I think you meant the underlined word to be "parallel". Jim

 

[Chrispy]

Good grief why would you duplicate transducers on a single channel like that? Speaker A and B are really more intended for different rooms/times rather than some sort of dual stereo output in a single room (which is daft to me).

 

[izeek]

Good grief why would you duplicate transducers on a single channel like that? Speaker A and B are really more intended for different rooms/times rather than some sort of dual stereo output in a single room (which is daft to me).

The point of the question was to find out why people do such.

 

[mhardy6647]

I think you meant the underlined word to be "parallel". Jim

yup. drat it all!
sorry about that @izeek ?

Thanks @Jim Taylor!

 

[raindance]

The point of the question was to find out why people do such.

You've been hanging out at audiokarma, haven't you I was silly enough to ask someone about this and also about why all their speakers were shoved into corners or against the wall directly beside the 80's style hifi cabinet... Not a popular question, I can tell ya. Anyway, it seems some people use old floor standing speakers that direct the treble at your ankles, so they add a bookshelf on top to add sparkle. Or they only use one set at a time. Or they use the old worn out ones at the bottom as a speaker stand. Or, perhaps their front porch is already full of old sofas and the old speakers don't fit out there, Or, and this would be the only scientifically valid use case, the speakers are divided into a bass cabinet and a mid/treble cabinet which share a common crossover.

 

[izeek]

You've been hanging out at audiokarma, haven't you I was silly enough to ask someone about this and also about why all their speakers were shoved into corners or against the wall directly beside the 80's style hifi cabinet... Not a popular question, I can tell ya. Anyway, it seems some people use old floor standing speakers that direct the treble at your ankles, so they add a bookshelf on top to add sparkle. Or they only use one set at a time. Or they use the old worn out ones at the bottom as a speaker stand. Or, perhaps their front porch is already full of old sofas and the old speakers don't fit out there, Or, and this would be the only scientifically valid use case, the speakers are divided into a bass cabinet and a mid/treble cabinet which share a common crossover.

Absolutely not.

 

[raindance]

I'm not saying I haven't tried it... if the amp doesn't emit smoke, it gets louder - great for parties or listening from another room perhaps

 

[mhardy6647]

There also was, is, and apparently always will be the Cult of the Stacked Advents -- in terms of four loudspeakers reproducing two channels in one space!
https://community.classicspeakerpag...s-as-reviewed-by-the-absolute-sound-magazine/

 

[mhardy6647]

Absolutely not.

Don't sweat it.
There will always be opportunity, and reason, for experimentation.
Conversely: Beware the dogmatic.

There's another interesting wrinkle on four loudspeakers in one room -- the "ambience recovery" scheme first popularized (to the best of my knowledge) by David Hafler (he of Acrosound, Dynaco, and Hafler fame) and later adopted as a "quadraphonic" synthesizer by many lower-end components/manufacturers in the early-mid 1970s and precursor to "Dolby ProLogic" in many respects.

The "Hafler Circuit" essentially reproduces out-of-phase information carried in the two stereo channels by a clever, simple, but potentially hazardous (to some amplifiers!) scheme of connecting four loudspeakers to two channels. The amplifier must have a common ground for its two channels to do this.
The commercial versions of this (including Hafler's/Dynaco's own) usually have some sort of level control for the "ambience recovery" speakers.

Dynaco QD-1 front by Mark Hardy, on Flickr

A vaguely similar (at least from my perspective) scheme using only two loudspeakers (but with multiple drivers connected in interesting ways) was also developed and commercialized by Polk Audio (initially in the early 1980s, but reintroduced a couple of years ago with their flagship L-800 loudspeaker) to minimize aural crosstalk and enhance stereo "dimensionality". Polk calls this "technology" SDA ("Stereo Dimensional Array").

Copy of SD A2.3 by Mark Hardy, on Flickr
The SDA models produced by Polk in the 80s and (?) early 90s got pretty... Byzantine.

EDIT: For completeness here's the current SDA Polk model L-800.

 

[raindance]

I had the Hafler "ambience recovery" system in place in my system in the 80's. I basically fed the two speaker positives into a floating volume control and amplifier. On some recordings the effect was very interesting. On others it was quite awful. It brought out of phase stuff to the foreground, albeit behind me, and sometimes this content was recording defects, such as extreme sibilence. But it was definitely the precursor to Dolby prologic style quasi surround.

Another thing I've seen, that my inner engineer finds irksome, is people who invest in surround sound systems and pile all 5 or 7 speakers around the TV. Then they tell all their friends about their fantastic surround sound. I guess they have surround sound from the TV's perspective

 

[Chrispy]

I had the Hafler "ambience recovery" system in place in my system in the 80's. I basically fed the two speaker positives into a floating volume control and amplifier. On some recordings the effect was very interesting. On others it was quite awful. It brought out of phase stuff to the foreground, albeit behind me, and sometimes this content was recording defects, such as extreme sibilence. But it was definitely the precursor to Dolby prologic style quasi surround.

Another thing I've seen, that my inner engineer finds irksome, is people who invest in surround sound systems and pile all 5 or 7 speakers around the TV. Then they tell all their friends about their fantastic surround sound. I guess they have surround sound from the TV's perspective

Reminds me of my sister who had her 5.1 set on top of the cabinet her tv was in....and it was only about 3 x 2 feet, too. She didn't want to deal with wires in the room.