Model Railway Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
2,151 Posts
Discussion Starter · #1 ·
Planing to use 2 speakers coupled together with loksound 3.5 decoder.

Question : both speakers are 100 ohms, will that have any back effect on the performance of the decoder consequently to the performance of the loco? Also is the below schematic the correct way of wiring?



If it is, the 2 wires coming out of the decoder to the speaker has the same color, guess it does not create a problem of which pole you solder it to with one single speaker. However with two speakers how do you know which is the positive and which is the negative? There are no signs relating to the poles on the speakers. Intuition?

Thanks for your help.

Baykal
 

·
Registered
Joined
·
193 Posts
Dear Baykal,

You do need to make sure they are connected the right way round, otherwise they will be out of phase and the signal from one speaker will cancel out the signal from the other. There should be some marking on the speaker terminals to indicate + or -, so you know which way to connect them. If not, then you have to use trial and error to work this out.
 

·
Just another modeller
Joined
·
9,983 Posts
QUOTE (ebaykal @ 31 Mar 2008, 02:23) <{POST_SNAPBACK}>Planing to use 2 speakers coupled together with loksound 3.5 decoder.

Question : both speakers are 100 ohms, will that have any back effect on the performance of the decoder consequently to the performance of the loco? Also is the below schematic the correct way of wiring?

If it is, the 2 wires coming out of the decoder to the speaker has the same color, guess it does not create a problem of which pole you solder it to with one single speaker. However with two speakers how do you know which is the positive and which is the negative? There are no signs relating to the poles on the speakers. Intuition?

Thanks for your help.

Baykal

Hi

speaker configuration has NO effect on loco performance. Audio and loco drive are linked for back EMF reference only - however audio and loco drive sections are effectively separated for all other purposes.

You have shown a series connection, and your wiring is correct. It doesn't matter about which terminal is positive or negative, as long as your approach is consistent as per the drawing.

(its equally OK as [wire > + > - > + > - wire] or [wire - > + > - > + wire] )

My preference though is parallel.

With them oriented the same way as you showed in your image, wire them in parallel. ie one wire to both left terminals, one to both right terminals.

The difference:

Series will double the inpedance and effectively halve the power available. That doesn't mean half volume, just half the energy, which will affect low frequencies mostly.

Parallel will halve the impedance to 50 ohms which is still safe for the decoder, and will incresase the available energy which is anyway needed to overcome the double mechanical resistance of two cones. You will hear a slightly louder and more "full" sound by using parallel connection...

TWO in parallel is however the safe limit. demanding more and more energy by lowering impedance adds to heat generation and while 50 ohms is still safe for the LS 3.5, below 50 ohms can conceivably cause damage long term.

Regards

Richard
DCCconcepts
 

·
Registered
Joined
·
2,151 Posts
Discussion Starter · #4 ·
Thanks for all the info Richard.

I'll go for the parallel and see how it turns out.

Baykal
 
1 - 5 of 5 Posts
Top