Comparison of 7 different speaker combinations for class 141/181

[Adrian]

Just posting this here in case it's useful for someone in the future - it's a set of comparisons of various different speaker types for the 141 including:

* double iPhone

* twin sugarcubes

* slim sugarcube

* bass enhanced

* twin megabass

* EM2 bass (knew it wouldn't fit but had to try it out )

* Direct comparison of double iPhone and combination sugarcube & megabass

* The winner (IMHO): Combination of 1 x Sugarcube & 1 x Megabass

Enjoy!

 

 

[Sean]

interesting, you have me thinking that i cant help but wonder what it would sound like if you added a low pass filter just before the megabass.

in theory you could drive the megabass a bit harder without the high frequencies going through it, any tinny high end sounds might be better handled by the sugarcube alone as that part of the sound would be translating poorly to the megabass and taking overhead from the low end sounds.

same goes for the sugarcube, if you removed the low end frequencies below a certain point where the speaker cannot reproduce decent sounding bass it would clear up any muddiness in the higher end of things and you could drive the speaker a bit harder.

the 2 speakers could sound a lot better overall if either one was carrying a different element of the sound and the end user was hearing a combination of both speakers tuned to their respective frequency ranges.

i am not familliar with these micro speakers exactly, but in a home stereo speaker with a tweeter and bass cone this is how the speakers are usually configured internally.

 

the circuit itself is simply made with a single capacitor and resistor, for all that waffle!.

 

low pass                                                                                                     high pass

 

basically in either case, the value of the cap and resistor will set the cutoff frequency, a variable resistor can be used for messing around  with cutoffs to develop an idea of what works and what doesnt.

 

also youve got me curious about somthing else, are you just using bare speaker cones mounted into the loco or are any of them a bit more complex ie in little enclosures of any kind?

 

Edited March 10, 2022 by Sean

[murphaph]

It might be worth a try but I wouldn't expect too much from adding filters simply because these model train "bass" speakers aren't comparable to a woofer etc. in your home audio setup. The travel of the speaker diaphragm is what determines its frequency response. The more travel, the lower the frequency, the more the bass. To get more travel, the speaker cone needs to get bigger. But these speakers are hemmed in by our models so in reality they are at best all mid-range/tweeters speakers or even pure tweeters. 

The other thing to note is that for some folks, me included, the sound should not be overpowering. If you have a few sound equipped locos running simultaneously you may well not want to hear the one on the other side of the room to where you are standing. It's not realistic to me to be able to hear a loco that is a scale 2 miles away at almost the same volume as the one I'm right beside. I want the sound to fade in as a loco approaches and fade out as it moves away from me. But this part is entirely subjective. If you want huge volume from your locos all the time that's fine too.

Mounting a bare speaker is always going to be a bad idea as the sound waves coming from each face of the diaphragm are 180 degrees out of phase (ie when the diaphragm moves forward and creates a positive pressure wave towards your ear, an equal in amplitude negative pressure wave is created from the rear face of the diaphragm and this pressure wave follows very closely behind the first one, largely cancelling out the total sound. That's why speakers have enclosures, to capture that negative pressure wave. They work very poorly without one. A speaker mounted tightly to the inside of the model body however is effectively mounted in an enclosure, though almost certainly not a very good one as they should have some relation to the speaker size which I forget now.

[Adrian]

That's very interesting information @Sean an @murphaph  Thank you!

That logic of having different speakers handle different parts of the sound totally makes sense but is beyond my capabilities for now  And I agree with Phil, that I do like the sound fading over distance as well. To answer your question, the speaker do have their own enclosures and are simply mounted on the chassis using black tack - again as Phil said there's not enough space to do anything else in most OO locos, to say nothing of the narrow CIE bodies on these models!

[irishthump]

This is a good video that clearly explains the basics of speaker enclosure design in the context of model railway applications. It's a bit dated, but still relevant.

 

[Adrian]

That's really interesting ^^ thanks for sharing