Modelling the transition era as I do, I want to have good sound quality  for my narrow bodied diesels.  Unlike steam locos which have nice, wide  tenders to take big speakers and provide big sound chambers, the narrow  bodied diesels are challenging, to say the least.

Following on from my testing in another thread, viz:

http://www.loksoundtragics.com/view_topic.php?id=23&forum_id=10

I eliminated the contenders to speakers that are at least 23 mm in  diameter.  My targets were the loudest speaker configurations as I can  always turn them down.  I like to have the horn as loud as possible and  then set the other sounds below that.

I was left with the 8 Ohm 25 mm diameter 3 mm thick speaker and the 4 Ohm 23 mm ESU 3 mm speaker.

For my lab rats, I chose a pair of Proto 2000 GP 38-2s.  I picked them  up for just over A$100.00 for the pair.  I installed a couple of yellow  LEDs on the roof of each one and connected them to the Aux 1 (green) and  Aux 2 (purple), wires.  They will be handy for later testing.



My first test was using two 23 mm speakers vertically, sealed in a  hyperbaric set up with the sound exiting around the gearbox of the  bogie.



Hopefully this will show it a bit better.



Here you can see them mounted.  They were glued in place using PVA glue,  which provided an anchor similar to a gasket, and also sealed them from  the outside.



I assembled the loco and tested it.  The sound was really loud, but had no bass component.  I abandoned them.

Next, I reamed out the weight in the fuel tank area.  I was able to fit a 25 mm speaker flush with the bottom of the weight.



The speaker was once again glued in place to anchor it and seal it.  There was an air space underneath the motor.



In the second loco (number 328), I reamed out the weight in the tank  area and inserted an ESU 23 mm speaker and enclosure.  It fitted neatly  under the motor and was PVA glued in place.  I reduced the depth of the  enclosure about.5 mm so that it wouldn't protrude below the plastic tank  cover, as the tank on the GP 38 runs very close to the rails - also so  that it wouldn't be seen when it is running.



Before re-assembling the loco, I cut the pickup tabs off the pickup bars  and soldered wires direct on to the top of the brass strips.  The P2K  dry connectors can give trouble after a while, so I eliminated the  possibility at the start.



Next I inserted some double sided tape on top of the speaker enclosure and set the motor up nice and straight.





As these were both second hand locos, I serviced all of the moving parts before re-assembling the locos.



Then I made a video of the two locos running with their sounds set at the same levels.

I had to reduce the engine volume in Sound Slot 1 to 80% in both locos as they were so loud that the speakers were distorting.

The locos are fitted with ESU Loksound Select decoders which were  uploaded with Project File 73426.  This is listed as being for the 16  cylinder EMD 645E motor which is what Wikipedia lists as the motor for  the GP 38-2.

It doesn't really matter which project was used, so long as it's the  same for both test locos, but I thought I may as well have the right  one.

Anyway, here is the video of the two locos under test - and I stuck some  gratuitous running shots on the end of the movie, because I could. 

I reckon the ESU does a better job.  It's louder and crisper.  The 25 mm  was softer.  The comparisons with the horns are the most important for  me.

http://www.youtube.com/watch?v=3tD2FwUbfVg

http://www.youtube.com/v/3tD2FwUbfVg 

Thanks for that demonstration Max, interesting how you mounted the speakers.  The work is neat as well - mine always look pretty ratty.  As for the sound comparison, it's difficult to tell and frankly they both sound good.

Thanks for the video - always nice to see trains running.

Cheers

John

 

Thanks, John.   I guess that's why I'm a Loksound Tragic.   

Once I have fine tuned the volumes, I'll do another movie.

Cheers

[user=269]MaxSouthOz[/user] wrote:

.   I guess that's why I'm a Loksound Tragic.   

No, just a sound tragic :thumbs

I want one ……….or two………………..or three !!!!

Excellent Max and, as John said extreeeeemly neat. thumbs

I'm a huge fan of the QSI decoder you put in my GP40 (or was it a GP38 ….:roll:) - whatever it was, it's brilliant.

Thanks, Peter.  :cool:

Good work Max :thumbs

Now I'll ask the dumb question - why the LEDs in the roof ?:oops:

Thanks, Dave. It's buried in there somewhere.

The Loksound comes with two Aux wires (green and purple).  These two locos are set up so I can play with the different options available in the programmer and the LEDS (masquerading as beacons), tell me if I've been successful.

[user=269]MaxSouthOz[/user] wrote:

Thanks, Dave. It's buried in there somewhere.

The Loksound comes with two Aux wires (green and purple).  These two locos are set up so I can play with the different options available in the programmer and the LEDS (masquerading as beacons), tell me if I've been successful.

Wow Max.  How do you get LEDS to speak ………………..:cheers

[user=6]Petermac[/user] wrote:

[user=269]MaxSouthOz[/user] wrote:

Thanks, Dave. It's buried in there somewhere.

The Loksound comes with two Aux wires (green and purple).  These two locos are set up so I can play with the different options available in the programmer and the LEDS (masquerading as beacons), tell me if I've been successful.

Wow Max.  How do you get LEDS to speak ………………..:cheers

Morse code - how else quest:

Ah yes of course, I'd forgotten that ………..;-)  Presumably for steam engines, it would be semaphore …………:roll:

[user=269]MaxSouthOz[/user] wrote:

Thanks, Dave. It's buried in there somewhere.

The Loksound comes with two Aux wires (green and purple).  These two locos are set up so I can play with the different options available in the programmer and the LEDS (masquerading as beacons), tell me if I've been successful.

Thanks Max -  so the LEDS are not reflecting the sound but other decoder functions.

I enjoyed the video  but I'm sure the layout was the one you were doing up so that you could sell it :hmm

That's right, Dave.  Everything from ditch lights to fireboxes.

You're right.  I sat down and drew up my plan for my new dream layout.  When I was finished I looked at it - and guess what it looked like . . .   :shock: