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Could I use 4 ohm in place of 8ohm speaker here?

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Could I use 4 ohm in place of 8ohm speaker here?
Posted by Anonymous on Saturday, April 12, 2014 8:31 PM

I have a few of the inexpensive (not great but useful) digitrax SDN144 decoders.  Would I be able to swap in a higher quality Zimo 4 ohm speaker for the 8ohm default one?  I wish to use just one speaker in my new VO-1000.  Would I be able to do it with additional electronics added.....  I'm not a electronics smartie, but well able to solder up whatever I am told.

Unfortunately the 8ohm Zimo is too big.

Thanks for any tips.

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Posted by Mark R. on Saturday, April 12, 2014 9:42 PM

The ohm rating has nothing to do with the physical size .... unless that just happens to be the only options offered.

Simply put, you should not use a four ohm speaker on a decoder designed for an eight ohm load. You could go higher (16 ohm), but not lower (4 ohm) - you will damage the audio output amp.

You could wire two four ohm speakers in series to maintain your eight ohm load, but if space is a consideration, that's probably not an option. There are MANY sizes of eight ohm speakers available out there from numerous sources.

Mark.

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Posted by rrinker on Saturday, April 12, 2014 10:48 PM

Absolutely not. It's already pushing it to use an 8 ohm with those decoders, you will need to turn off BEMF to prevent slowdowns when blowing the horn, although that's not really an amplifier load problem, it's a "the cpu can;t do all those things at the same time" kind of load.

Is this an N scale ot HO scale VO1000? If it's HO, a Loksound Select Micro and a rather large speaker actually can fit, Bowser has done this with the factory sound versions. I bought a power chassis and swapped my existing shell from an older non-sound one. Sounds infinitely better than the old 8 bit Digitrax sound decoders.

You should be able to find small 8 ohm speakers - like the CT sugar cube speakers, to fit in an N scale version.

                --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Texas Zepher on Saturday, April 12, 2014 11:03 PM

Cisco Kid
Would I be able to swap in a higher quality Zimo 4 ohm speaker for the 8ohm default one?

No, not unless the SDN144 specifies it can use a 4 ohm speaker.

I wish to use just one speaker in my new VO-1000.  Would I be able to do it with additional electronics added....

Since you don't want to use a second speaker, you could get another 4 ohm inductor to put in series with it.  Something like this. http://www.mouser.com/ProductDetail/Sumida/5406-391-34-00/?qs=sGAEpiMZZMukHu%252bjC5l7YRKILtFu0hlh0nMowAHeUNc%3d.  Note that I am not recommending this unit, just using it as an example.

What I can't tell  you, without knowing a whole lot more about the speaker and doing come calculations,  is how to match the resonance frequency of the inductor with the speaker to prevent it from acting like a low-bypass filter. 

Since you say your not good with electronics this probably won't help.  All the on-line sites I can find that are related are for building crossovers.  This one has a "first order" section which is actually the most simple  Butterworth crossover.  The inductor would be L1.
http://www.apicsllc.com/apics/Misc/filter2.html

As the others have said, the best thing is to find an 8 ohm speaker that meets your size needs.  There are bunches and bunches of them out there.

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Posted by Graffen on Saturday, April 12, 2014 11:19 PM
But two 4 ohm speakers in series is equal to 8 ohms. Or 4 speakers of 4 ohm coupled in series/parallell.....

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Posted by Anonymous on Sunday, April 13, 2014 12:50 PM

Thanks, all.

Reason I asked was that I was just getting around to looking at the better quality speakers, and the Zimo I mentioned is one of those bass reflex types at about $18.00 ea.  I have other 8 ohms in the drawer that would fit, but wanted to put a superior speaker in as a test since these decoders are noted for poor sound and I have a couple more to play with in the future.

So, if anyone knows of another of the top end 8ohm speakers no bigger than .63" or 16mm wide, oval or round I would be interested.

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Posted by rrinker on Sunday, April 13, 2014 1:49 PM

 TONS of speakers that are 8 ohms and less than 16mm in the longest dimension:

http://store.sbs4dcc.com/sugarcubespeakers.aspx

 

No connection to this vendor, haven't even bought anything from them, yet. Just what came up searching for a variety of speakers.

          --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by Anonymous on Sunday, April 13, 2014 3:12 PM

Thanks, Randy.

It has obviously been a while since I added sound to a loco.....three years, I guess..and still using up my stock of large ovals.  These sugar cube speakers look intriguing.  I get the idea of sound chamber extensions.

Anyone have a quick opinion as to the best of these cubes vs. some of the bass reflex or expanded range speakers offered by Zimo and others.  Which wins in a comparison?

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