Better sound for your Bachmann Deltic

[legomanbiffo]

This article details a loudspeaker design which will significantly improve the sound from your Bachmann Deltic regardless of whose version of Deltic sounds you use (mine, Howes, SWD etc). Of the four different speaker designs I tried, this one performed the best by some margin. Photographs of the prototype design follow the text. The article is offered in good faith for the common good. No responsibility is accepted if you destroy your model trying!

 

 

Aim;

 

To construct an airtight chamber in the underframe fuel tank area of the Bachmann Deltic, with a long reflex tube, open to the air at one end, and using the drive unit from a bass reflex speaker. The reflex tube acts like an organ pipe; resonating at, and reinforcing the lower frequencies that are needed to produce a convincing Deltic sound. In the finished article, the open end of the tube and the loudspeaker drive unit will be at the same end of the loco, such that the distance the sound has to travel to the outside air is as large as possible.

 

You will need;

 

A length of Evergreen StripStyrene number 258 (rectangular tube 4.8 x 7.9mm / 0.187 x 0.312”) or similar

Some plasticard sheet, 30 thou or thereabouts for the bottom (next to the track), and something thinner for the top (next to the motor)

A 21 x 57 x 9mm bass reflex speaker

 

Method;

 

1. Read the method in full before starting work!
2. Remove the body, desolder the connections to the pickups at both ends, remove the bogie screws and drop the bogies.
3. Unclip the underframe moulding and set the casting to one side.
4. Use a disc cutter in a dremel to carefully cut out the central section of the underframe, leaving the two ends and the cosmetic fuel tank sides in place. Tidy up with a file and sandpaper so that the long internal sides are completely flat (you’ll need all the width you can get at this stage) .
5. Cut a piece of the rectangular  tube section to the length of the tanks plus 10mm or so initially. Make a flush cap for one end and glue in place, then cut the tube to the match the overall length of the tanks.  Make sure the cap is airtight. In the finished article one end of the tube will be open to the air and visible on one side of the loco, but painted black will be largely unnoticeable.
6. Take the bass reflex speaker and using a razor saw, cut off the end with the hole such that the length is reduced to around 44mm long. The actual length is not critical, but it looks better if you keep it symmetrical. Carefully split the speaker enclosure in half along the seam and discard the back. The drive unit remains in place in the other half in the final design.
7. Carry out a dry run and see if the tube and the remaining speaker  assembly will fit side by side in the tanks. Remove plastic carefully until they will. It is quite a tight fit.
8. Take the underframe moulding and place it the right way up on the bench. Use the thinner plasticard to construct a ‘lid’ for the tanks. It needs to be completely airtight, and must not protrude upwards too far or you won’t be able to clip the moulding back onto the casting. Carry out a dry run after glueing to make sure you can clip it back on before leaving things to dry.
9. Loosely fit thetube section into the tanks along one side and mark a rectangular hole in its side, at the same end as the cap. The hole must be open to the inside of the sealed chamber and approximately the same size as the cross-sectional area of the tube (it should be around 3mm x 6mm). Only cut into the side of the tube, not the top or bottom.
10. Desolder the red and black wires from the speaker and carefully pull them away from the glue at the end of the speaker. Remove any residual glue and sand the ends flat in readiness for reconstruction. Replace the speaker wires with thinner ones of sufficient length to run back to the chip.
11. Place the reflex tube and speaker assembly side by side such that the open end of the tube is at the same end of the loco as the loudspeaker drive unit. Drill two tiny holes in the ‘lid’ of the enclosure and pass the speaker wires through. Glue tube and speaker in place and use a square across the bottom to ensure they remain flush whilst drying.
12. Gently pull the speaker wires through so there isn’t too much slack inside the chamber and nothing is touching the speaker cone. Use Evo Stik or something similar to seal around the speaker wires where they pass through the ‘lid’, to make sure the holes are airtight.
13. Once dry, close any remaining gaps at the speaker end of the tank assembly using plasticard or filler, such that the finished enclosure can be completely airtight.
12. Using the thicker plasticard, cut out a rectangle to form the final part of the sealed chamber and glue in place, taking care not to obstruct the hole cut in the reflex tube. Use filler to block any remaining holes in the completed enclosure and tidy up cosmetically.
13. When dry, confirm that the enclosure is completely airtight by sealing your lips around the open end of the reflex tube and gently sucking and blowing. If the speaker cone moves up and down significantly then all is well. If not, seek out and fill any leaks (dampen the backs of your fingers and feel for cold air around the seams etc whilst blowing into the reflex tube).
14. Paint the underframe assembly including the inside of the reflex tube where it will be seen, allow to dry, then reassemble and test.

 

 

The overall concept. The reflex tube is on the right, with the hole at the corner furthest from the camera

 

 

 

A view from the opposite end showing the drive unit and reflex hole

 

 

 

A close-up of the reflex hole, which is not noticeable in normal operation

 

 

[virginhst539]

This will be this weekends project, can't wait to fire it up for the first time

[nimbamoss]

Hi Biff,

 

I sense another project on, luckily I have a spare V4 deltic chip to use.

 

 

Ian

[jessy1692]

Ooooh, got a shawplanned Pinza crying out for a sound chip, tanks already cut.......................

 

Best get saving!

 

Cheers Bif

James

[virginhst539]

Just a quick question did you remove the entire bottom of the tank or just enougth for the speaker and the pipeing

[legomanbiffo]

In this one I didn't remove the entire tanks but in later ones (as the method matured) I removed most of them leaving only the cosmetic sides and the ends. To an extent it's the end result that's important, not how you get there. The end result should be a big sealed box with a long tube to the outside air.

 

Bif

[7APT7]

Hi Biff

 

Hope all those deep sounds have been mastered.... would love to hear one next time I'm at a show and you have one for all to hear.

 

excellent work...

 

Jamie

[legomanbiffo]

Jamie,

 

You can hear them in our 7mm demo loco which often has people grinning so something must be right. All of the 4mm ones I did were a pal's so I don't actually have one in 4mm to demo.

 

Bif

[7APT7]

Cheers Biffco

 

will you be doing one for in 4mm...? to show on tour show tours....

 

Jamie

[virginhst539]

So fired up my attempt at this today and for the most part I have got it working. Only down sides was when firing up did not get the low drone and the overall volume was a tad quite when running with rolling stock

[legomanbiffo]

It sounds like your enclosure might not be completely airtight. From experience of building four I found that the slightest leak made a big difference. Check seams and corners carefully and apply extra liquid-poly or sealant if necessary. The best way to check is to put the reflex port to your mouth and gently apply breath pressure and see if it leaks away. Gentle breath pressure in and out should move the speaker cone up and down. If it doesn't move very much, or not at all, you probably have a leak. You can check where air is leaking by dampening the back of your fingers and feeling all round for cold air whilst you blow gently into the reflex tube. If the model is reassembled it's difficult to get a seal around the hole with your mouth so put a short length of tube (eg the middle of a ballpoint pen) into the hole and seal all around it with blu-tac to try. This all sounds a bit Heath-Robinson but believe me it does work.

[virginhst539]

Will give it ago, will it make a difference to the volume as well when this is resolved?

[virginhst539]

A quick video of my attempt to let you hear it so far and suggest how to improve. So far from someone who has worked a fair bit on deltics has said it's by far the best sounding it just needs to be a bit more "meaty"

[charliepetty]

We are currently doing bespoke speaker conversions for Bachmann Class 55, this work includes complete new fueltank speakers, the sound brilliant and better still they also sound like a Deltic. 

 

Details if interested can be had from Charlie@dckits.co.uk    'Power to the People'   Charlie 

 

Look on 'youtube' for Merlin DCC, our Sound fitting man.    You will be impressed.

Edited July 25, 2015 by charliepetty

[tractor_37260]

We are currently doing bespoke speaker conversions for Bachmann Class 55, this work includes complete new fueltank speakers, the sound brilliant and better still they also sound like a Deltic. 

 

Details if interested can be had from Charlie@dckits.co.uk    'Power to the People'   Charlie 

 

Look on 'youtube' for Merlin DCC, our Sound fitting man.    You will be impressed.

 

Impressed !  Wow this sounds just brilliant  - easily the best sounding model Deltic I've heard. 

 

Regards

Ken

 

[charliepetty]

Impressed !  Wow this sounds just brilliant  - easily the best sounding model Deltic I've heard. 

 

Regards

Ken

 

A big thank you to everyone who bought, had reblown or better still got us to convert your Deltic to a 'Super Deltic !!!!.

 

HAPPY NEW YEAR from Steve, Ian, Alex & Charlie 'The Sound Team'   

[ColinK]

Looking forward to recieving my special super deltic. It will make my New Year very happy. Cheers.

[leopardml2341]

Me too.

[RBAGE]

Hello Charlie/Legoman,

I am about to try your improved deltic sound with decoder and speaker I got from you some time ago.

However, the speaker supplied was not a bass reflex so the technique might be slightly different to that described earlier.

The speaker you supplied had a frame which is about the size that fit right across the width of the tanks (less the visible sides which I should keep). This will make it difficult to fit the box section length along the full length of the tanks.

Can you provide any detail of your latest method please?

Bob

[RBAGE]

Hello All,

I carried out this conversion at the Missenden weekend (just past) and I can heartily recommend both the weekend and the conversion.

I was like a dog with two tail when I had finished and the transformation from a very disappointing and feeble, nondescript diesel sound to being at the end of Newcastle Central station when a deltic erupts was astounding. I still find it difficult to believe that so much sound can come out of a 4mm model.

Give it a go. You won't be disappointed.

If you don't feel up to it, Charlie offers a service and the price he quoted me is well worth it when you listen to the results.

I now have 3 more the convert.

Bob 

[Steve Brammer]

Hello everyone,

Thought I had better announce our latest development regarding the Deltic Sound Project. We have been trialing a new range of speakers, known as our new "Earth Mover" range. So far there are three variants EM1 to EM3.I have now shoe horned successfully one of these new EM1 speakers into a Deltic chassis. This also has the Alan Butcher speaker in there to keep it company! The result, I am afraid to say is now twice the bass and sound fidelity than it had before. Initial trials are looking really good and once it has finished being tested will be available as a conversion. A Deltic with this set up will be available for viewing at the 2016 Perth Show.

 

Cheers,

 

Steve,

 

Merlin DCC,

 

Part of the "Sound Team".

 

working with Charlie and Legomanbiffo.

Edited June 22, 2016 by Steve Brammer

[leopardml2341]

Hello everyone,

Thought I had better announce our latest development regarding the Deltic Sound Project. We have been trialing a new range of speakers, known as our new "Earth Mover" range. So far there are three variants EM1 to EM3.I have now shoe horned successfully one of these new EM1 speakers into a Deltic chassis. This also has the Alan Butcher speaker in there to keep it company! The result, I am afraid to say is now twice the bass and sound fidelity than it had before. Initial trials are looking really good and once it has finished being tested will be available as a conversion. A Deltic with this set up will be available for viewing at the 2016 Perth Show.

 

Cheers,

 

Steve,

 

 

Merlin DCC,

 

Part of the "Sound Team".

 

working with Charlie and Legomanbiffo.

Oh b@gger, only just had mine back from you!

Edited June 22, 2016 by leopardml2341

[RBAGE]

What? Better than the previous conversion?

I'll have some of that.

Bob

[Steve Brammer]

Hello there,

Don't worry I am working on it so that the previous version can be upgraded. The new version employs the same speaker as before with the addition of the EM1 speaker set up. So it is half way there.

The top of the chassis will require a degree of milling but should be perfectly doable, if that's a word.

It is definitely worth the effort.

 

Cheers

 

Steve.

[legomanbiffo]

This has become a significant moral dilemma for us. I am always upgrading and improving the sounds themselves and Steve and Charlie are doing the same with the speaker fits. There has been a huge amount going on behind the scenes since our searches turned up the 'EM' (Earth Mover) speakers as we'e christened them. Before putting them on general release we've got to confirm that they're sufficiently robust, so they are currently getting hammered on the demo stand. We've got to see which versions fit in which locos (with and without metal or plastic surgery) and what works and what doesn't. We've also got to source them at a price that people find acceptable (though it is becoming adundantly clear that the anticipated price is not going to be an issue when their effect on performance is demonstrated). Regarding your purchase, it's a bit like when personal computers were developng rapidly; at some pont you had to buy one or you'd wait for ever for the ultimate machine. Regular customers will know that we always look after them so please don't worry about getting left behind.