Short answer...

Dear Yves,

Short answer:

LokSound Select (all variants) = 4Ohm (or greater) speakers will work
(If not using explicitly LokSound speakers, most common 3rd party "8 ohm speakers" will work just fine)

LokSound V4.0 (all variants) = 4Ohm (or greater) speakers will work
(If not using the Factory-supplied speakers, most common 3rd party "8 ohm speakers" will work just fine)

LokSound (Everything else) = 100Ohm (or greater) speakers required

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Longer answer

Impedance is shorthand for "how much current does this thing need?". Due to the Zen nature of Ohm's law, a lower impedance value means "more current required."

For amplifiers and other current sources, impedance means "how much current is available from this gizmo?" An amplifier with a 4 ohm rating will drive a speaker with impedance of 4 ohms and above-- there's plenty of current available (the speaker will only take what it needs). A 100 ohm speaker is no trouble to anybody. A 4 ohm speaker will burn out an 8 ohm amplifier, cause it draws too much current. (For the same reason, avoid shorting amplifier leads together*, because wire has 0 ohms impedance.)

There's no easy way to directly test speaker impedance, since it's frequency dependent in a complex way. For the very small speakers we put in rolling stock, the DC resistance is a rough approximation, but it's best to trust in the label.

pqe

*Good amplifiers will shut down when shorted, but you never know.

Most of the speakers I've

Most of the speakers I've seen are 8 ohm. Are there any advantages to 4 ohm ones?

Thanks for your reply,

Yves

maths VS "trust your ears"

Other things being equal

The only Loksound decoders to

The only Loksound decoders to use the 100 ohm speakers are the now obsolete 3.5 decoders. All versions of the current Select series and 4.0 decoders are designed to optimally use the 4 ohm speakers that Loksound also supplies. They will work equally well with 8 and 16 ohm speakers / arrays, but your volume will be dimished slightly.

Mark.

Has anyone tried...

... using the Select with two 8-ohm speakers in parallel?

TIA,

Ed

Google

Searching on Google pops up a few examples of parallel wiring of 8 ohm speakers,  resulting in a 4 ohm setup. 

Perfectly acceptable - as I understand it, that is actually the correct way to connect two of ESU's own sugar cube speakers in a single baffle. 

Connecting two speakers in series in a single baffle cons?

So connecting two speakers in series, the only con is lower volume? I actually have a Loksound Select with one sugar cube speaker with the Master volume CV set at 10. I should be receiving two sugar cube speakers and ESU's double speaker baffle today, to replace the single speaker. I might even try making a custom baffle to take advantage of the space.

I am going to a dual speaker setup to have better sound in the low frequencies. Not for loudness. 

A Single ESU 50321 is more than enough...

I am currently upgrading my entire fleet of sound equipped & non sound locomotives.  I have made the decision to stick with the ESU Cube Speaker - 50321.

They are extremely flexible in that they come with the baffles to make varying sizes and can be close coupled as mentioned above.  One Cube Speaker for my ears is more than enough, in fact I have installed a pair closed coupled and to be honest it's not worth the money to use two speakers and a series of baffles.

Below are a few shots of them installed in an Atlas MP15DC & Athearn GP35...

Here is a video I also shot, this unit has one ESU 50321 - Cube Speaker, I'll be turning these down a little too.

All of my decoders are ESU's LokSound - Select Direct's.  I have the LokProgammer and load all of my own sound files.

Cheers, Jas...

Great Post Yves

Thanks to Prof. and Pelsea for the explainations. And thank you Jas for the reinforcement that the ESU cubes are great. I have watched the DCC / Sound videos on Trainmasters, and came to the conclusion that I am going to use them in my future sound installations. I have a bunch of little brass Minarets that I have wanted to get DCC AND sound into for years, and every year I wait, the decoders and speakers are getting smaller and smaller so that can become a reality. Looks like it is just about time to pull the trigger.

Michael

Hook the speakers up in

Hook the speakers up in parallel - the same wire from the decoder goes to both speakers.

It would be like connecting batteries up so that the same wire connected all the + sides and the other wire the - sides. 

If you hook the speakers up in series I think the resistance gets higher for no real advantage. Series is where you would take a wire from the decoder, hook it to one side of speaker1, then hook the other side to speaker2, and connect speaker2 back to the decoder. That is what they DON'T want you doing. 

Okay, let's if I can do this graphically with a couple quick (and rough) sketches:

This is Parallel, with the wires staying on the same side - decoder is green, wires and speakers are black - 

This is serial, where it is effectively one wire going through all the connections:

Yeah, kind of rough sketches - I was using my finger on a tablet. 

V3.5 and earlier ESU decoders required 100Ω speakers