Speaker Wiring

[cheezes]

Here's one for all you Techy-types:
If I connect 4 8ohm speakers in parallel to a single jack socket, will I get 2 or 4ohms?
I think I'm right in saying that in series it'd be 32ohms and series/parallel 8ohms.

[Sporky_McGuffin]

All in series it'd be 32 ohms. All in parallel it'd be 2 ohms. Parallel pairs in series (or series pairs in parallel) it'd be 8 ohms.

[cheezes]

Cheers for that!
How do I get 4 ohms with 4 8 ohm speakers then? Is it by using 2 jack sockets?

[Sporky_McGuffin]

You can't get 4 ohms with four 8 ohm speakers.

You can get two 4 ohm loads - two of your 8 ohm speakers in parallel for each - but as soon as you connect to both you'll be presenting a 2 ohm or 8 ohm load.

[cheezes]

Of course I am a twonk!
It's obvious when someone explains it to me. I'd been mulling over the permutations for some time. I'm gonna get me some 16 ohm jobbies.
Thanks!

[Sporky_McGuffin]

Or 4 ohm. You can series/parallel them to get 4 ohms.

[ecc83]

The formula for ANY set of resistors in parallel is..

1/Rtotal =1/R1+1/R2+1/R3.........If you don't have a calc' with a 1/x key there's one in Accessories!

Dave.

[imported_Dannyboy]

Originally Posted by Sporky_McGuffin

You can't get 4 ohms with four 8 ohm speakers.

You can get two 4 ohm loads - two of your 8 ohm speakers in parallel for each - but as soon as you connect to both you'll be presenting a 2 ohm or 8 ohm load.

Sporky - could you do something clever here and have all 4 8R speakers in parallel, to give 2R of load and the have these in series with a 2R power resistor to get 4R ? Works on paper but would it sound OK ? I've never played around with speakers so I've no idea.

[ecc83]

Sure you could Dannyboy!

The resistor would need to be rated at about 300W and be bolted to about a square foot of 3mm ally! Assuming you have full drive capabilty.

As to the sound, if you were using a 100W valve amp it probably would not make that much difference since valves don't damp speakers much anyway but you would be losing 50W in the R.

The right way to do it would be a transformer with a ratio of 1.414:1 could be an autotranny to save a bit of cash, still be costly tho! BTW Never EVER connect any kind of transformer to a transistor amp unless The Book says you can!

In fact if you found an old 100W valve o/p trans with a knackered primary, you could strip that off and use the secondary taps as an auto. No, not very kosher but it would work.

Fact is it is bad "hi fi" practice to ever put speakers in series and there are some custom bass cabs that use specially built 32R drivers so they can all be paralleled. But of course the wring of a classic 4x12 gives us the sound we know and love!

Dave.

[Sporky_McGuffin]

Wot he said.

Though rather than one whacking great 300w one I'd say build a matrix of lower wattage ones so that if one goes you don't end up with the whole load disappearing. I made a loadbox for my 10W Cornell, and that's actually 4 35W resistors in parallel, rivetted to an aluminium casing and with thermal compound in there too. Rather over the top, I'll concede.