Question, I am in the process of installing a new TCS Diesel WOW decoder into a Kato SD90. I want to install 2 speakers. I am using Railmaster Hobbies 8 ohm speakers. Do I wire the speakers in series or in parallel and why?
Meybic,
In the case of a decoder audio output....run them wired in series, the output will run cooler, versus parallel, which will run hotter, because it is drawing more power to drive the two. Explanation:
http://www.installdr.com/techdocs/999016.pdf
Take Care!
Frank
Here's a good explanation of speaker impedance and combining...
http://www.mrdccu.com/curriculum/speakers.htm
A single 8-ohm speaker will create 8-ohms of resistance.
Two 8-ohm speakers wired in parallel will create 4-ohms of resistance.
Two 8-ohm speakers wired in series will create 16-ohms of resistance.
There is a good reference here, too:
http://www.sbs4dcc.com/tutorialstipstricks/wiringmultispeakers.html
Hope this helps you out, Ed
If you add two 8 ohm in series, you are creating a 16 ohm speaker set from the decoder's viewpoint. If two in parallel, you are presenting 4 ohms to the decoder.
I'm not in tune with the TCS WowSound diesel particulars, but see in the attached link that one EMD decoder is "optimized" for 8 ohms.
http://tcsdcc.com/Customer_Content/Literature/Decoders/WOWSound/WOW101-Diesel-EMD.pdf
If you want two speakers (more air movement capability) you would then be steered to using two 4-ohm speakers wired in series. But you may want to ask TCS what they recommend basis their experience. It's possible they will say that 4 ohms presented will overload the decoder (and ruin it). Not sure what they would say about 16 ohms presented. Alternately, you could technically wire 4, 8 ohm speakers to present 8 ohms to the decoder, by wiring 2 pairs in series (these are then 16 ohms per pair) and wiring the pairs is parallel, which makes the combo 8 ohms. But fitting four with enclosures into the body would be tough, unless sugarcube types. The following has some good diagrams on multi-speaker wiring:
http://store.sbs4dcc.com/SBS4DCCSugarCubeSpeaker11x15mmw/2x2QuadCoupledSoundChamber.aspx
By analogy, I've used some LokSound Select decoders that are optimal at 4 ohms but 8-16 ohms can also be presented. These come with 4 ohm speakers. In a couple cases I installed multi (4) sugarcube speakers that presented the 8 ohms and they worked fine, and I still had to turn down the master volume from max. You might also pay attention to wattage, as the WOW decoder page talks about 1+ watt speakers, so I presume it's audio output is around 1 watt nominal. The LokSounds Selects are provided with 2 watt speakers but I'm unsure what the decoder max output actually can be.
Do also address the speaker(s) having an enclosure. This can be a box that comes with it, one you make from styrene, or mounting the speaker so it uses an enclosed portion of the body (e.g., sealed portion of roof), boxed in by styrene ends or sides to complete a box.
I had some fun installing LokSound decoder into Proto 2000 SD50 and SD60. Not sure how the Kato and 90 series would make it easier or more difficult. In my case, I was able to place the decoder above the motor. At the long hood end, I milled the weight down so a styrene (not big) enclosure with 2 13x18mm sugarcube speakers could fit, and added 2 11x15mm sugarcube speakers in the cab (with styrene box sides). A rather tight fit. IMHO, two sugarcubes will outperform at least some 18mm wide ovals that fit the narrow hood diesels, four sugarcubes is better than two, but the best I've done is two 1.1" round high bass speakers that fit nicely in a E-series diesel but are too wide for the 13mm wide long hoods.
Maybe someone can comment better on your application; i.e., whether 16 ohms is ok for the WOW Sound, or what 4-ohms speakers to acquire if you want two but not at 16 ohms.
Paul
Modeling HO with a transition era UP bent
If you wire an 8 ohm speaker in SERIES with a 1 Meg resistor, and then wire that combo in PARALLEL with another 8 ohm speaker, the value of the two will be very nearly 8 ohms.
Disclaimer: This post may contain humor, sarcasm, and/or flatulence.
Michael Mornard
Bringing the North Woods to South Dakota!
I called TCS today and asked them (since it is their decoder). Their answer was that it is perfectly fine to run the TCS Wow decoders with 2, 8 ohm speakers, wired in Series.
Wired in parallel, it will be twice the power (3dB), but run twice as hot.
Wired in series, the power of each speaker will be 1/4 of a single speaker. But because you have 2 (2 * 1/4 = 1/2) it will be about 3dB quieter. There are advantages to doing this...if you are running full volume, and the speaker cone is only rated for 1W, then you are less likely to distort. Also having a larger surface area is better for creating deeper bass. having two speakers of 1 cm^2 isn't as effective as a single speaker of 2cm^2 but it's still better then one speaker of 1cm^2 at reproducing bass. You may extend your bass range by ~1/2 Octave (roughly with a good speaker combo)
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Nitpicking:
3db is not twice as loud. Twice the power results in a 3db increase, yes, but twice as loud requires a 10db increase. 3db louder is just a small increase.
Solid state amps (meaning anything that is not vacuum tubes) have a lowest impedance rating, like 8 ohms in the example. You can use higher impedance, like 16 ohms, and the amp will work less hard. No harm to the amp.
Whatever the power output of the circuit at 8 ohms, a 16 ohm load will draw half as much power, and in the example, that means each speaker will get half of that. So two 8 ohmers in series will each get 1/4 the power as a single 8 ohm.