I have installed sound decoders into 3 versions of 48s - early and late Powerline and just recently into my long awaited Trainorama 48s. I have a DCC sound installation page on the latest Powerline on my web site at: http://members.optusnet.com.au/nswmn1/48Select3.htm using a Loksound Select Direct decoder with the prototypical correct 251B 6 cylinder sound and a MRC 18 mm speaker. I was never able to verify whether I had a 6 cyl sound but I hated the sound as it had too much turbo. On my layout, if I don't like the sound I'm not going to install it in my models. Call me Mr "close enough" sound man. Using Loksound decoders you can change the sound file but you cannot with Soundtraxx Tsunamis making it an advantage using the upgrade-able decoders.
The era for my Main North layout is 1965 - locos from from Gosford to Newcastle/Werris Creek were mostly steam. I only have a few diesel hauled trains - a Triple 48s "wheatie" (22 BWHs) from Werris Creek and a couple of "staged" 44 hauled North Coast trains - all hardly ever run. Two of my 44s are equipped with Loksounds with in my opinion, the bloody awful turbo 251 sound, so I thought I remove the Loksounds and put them into my recently arrived 46s. I need a few "electric" sound decoders so Loksound is the go with the 46s. Thanks to Chris Winston I have a superb V4.0 Loksound equipped 46. Now to make "electric" sound for the these older Loksounds but for now the GG1 sound will do.
The 48s will not be run much and as I'm a cheapskate I thought I'd fit my old DSD100-LC diesels into 3 of my Trainorama 48s using the original speaker - tinny sound but cheap. Two of these DSD equipped 48s are consisted with the 244 Tsunami equipped 4th 48 that'll be the "lead" loco of the with it's Horn being the one that is sounded in the Consist. Many of my locos including the Trainorama 48s have the Sugar Cube speakers from Streamlined Backshop - fantastic sound until.....
Recently I had to help a modeller with his his Loksound Select 251 equipped 48. The sound was woeful, too soft and poor performance. I reloaded the sound project and tinkered with the Speed Table etc and it still sounded woeful. He previously suggested his other 48 had too much turbo sound. I loaded a 244 and fitted a 15 x 11 x 8mm Sugar Cube speaker from SBS4DCC.
WOW!!! what a difference. I took it to another layout to "show off" the sound and one modeller said it just sounds like what I remembers the 48s sounded like.
Today I upgraded all of my Loksound Select equipped Diesels with the Loksound Alco 244 Project No 73401 and I am "seriously" thinking of getting rid of my "steamers" and move to the 80s.
Investigating the "sound" of a 48 I found a few Youtubes, where for me, they sound like the 244 sound file for both Loksound and Tsunami. I made a movie (below) where I have added the "real" sounds and the manufactured decoder sounds for the loco when it's idling and accelerating, where an easy convenient comparison of the sounds can be made.
Below video shows my Loksound equipped 4803 on my Main North layout crossing the Pages River, north of Murrurundi.