Fitting Sound to Hornby Thompson L1

[Pete22]

Hi, Can anyone help ?

 

I wish to fit a sound chip & speaker into a new Hornby Thompson L1 (DCC ready) tank loco.

I searched the web but can't find any fitting guides or info regarding which speaker to fit, and where it can be placed in the loco.

 

Has anyone converted one of these before ? I am keen to learn before I start pulling it apart !

 

Many thanks,

Peter...

[Ed-farms]

Having put a normal chip in mine, but not a sound chip, I know there is ample space in the bunker for the speaker. Howes, however do a sound chip for one so they must have a fair idea of what will fit if they are offering a chip ready for fitting.

[pauliebanger]

Hi, Can anyone help ?

 

I wish to fit a sound chip & speaker into a new Hornby Thompson L1 (DCC ready) tank loco.

I searched the web but can't find any fitting guides or info regarding which speaker to fit, and where it can be placed in the loco.

 

Has anyone converted one of these before ? I am keen to learn before I start pulling it apart !

 

Many thanks,

Peter...

 

Peter,

 

Sound, firebox glow, smoke can all be fitted to the L1. 

 

ZIMO from Digitrains is a less expensive alternative to Loksound decoders (about £40 less, depending from whom you buy your Loks).

 

Paul

[Pete22]

Many thanks for all the advice, I am pleased to hear there's room for the speaker inside.

I was toying with the idea of fitting a Hornby Sapphire decoder (which I already have), and then fitting one of the new MRC sound only chips (model 1908), as I hear they are not too bad ....

Anyway no decisions made yet, but I will fit sound to the loco soon.

 

Peter...

[Lady_Ava_Hay]

Many thanks for all the advice, I am pleased to hear there's room for the speaker inside.

I was toying with the idea of fitting a Hornby Sapphire decoder (which I already have), and then fitting one of the new MRC sound only chips (model 1908), as I hear they are not too bad ....

Anyway no decisions made yet, but I will fit sound to the loco soon.

 

Peter...

 

One wonders who told you they are 'not too bad' and whether you will agree with them after fitting.

 

The problem with 'piggy back' decoders is that they take a an awful lot of effort to synchronise sound with motion and much midnight oil is burned attempting to do just that and with very mixed results.

 

I personally have no experience with MRC sound decoders apart from hearing one or two and deciding as a result that I would stick with the majority and opt for combined motor and sound decoders . I have personally wrestled with both CT and Digitrax piggy back decoders and one of the latter remains in my N1.

[Rombald]

Hi, Can anyone help ?

 

I wish to fit a sound chip & speaker into a new Hornby Thompson L1 (DCC ready) tank loco.

I searched the web but can't find any fitting guides or info regarding which speaker to fit, and where it can be placed in the loco.

 

Has anyone converted one of these before ? I am keen to learn before I start pulling it apart !

 

Many thanks,

Peter...

Hi Peter,

 

I am also aiming to fit sound in the L1.  I have seen good reports of the Zimo decoders so it's a choice between the MX645R and the MX648R.  Both can be loaded by Digitrains with the Paul Chetter soundfile. This can be changed between heavy load or light engine sounds, and sounds change with acceleration and coasting.  See

 

http://www.digitrains.co.uk/ecommerce/dcc-sound/uk-sound/zs011-class-l1-tank-steam-soundfile.aspx

 

for details.  I would prefer the 645 as it's £8 cheaper (from Digitrains) and has 'stay alive' cap support.  The down side is it may be a couple of mm too long to fit in the bunker space, even if angled up over the DCC header.  The 648 is a later, and much smaller, decoder and would easily fit in the bunker space, but doesn't support a 'stay alive' cap.  I have already removed the coal from the top of the bunker and that space has a solid floor, measures 26x20mm internally, 9.5mm high at the sides and 12mm high at the centre.  This space is therefore large enough for the Loksound 16x25mm speaker. The 648 must have an 8 ohm speaker, whereas the 645 can be either 4 or 8 ohm, although I suspect the 4 ohm speaker may be overloaded at max volume, so I would prefer to use 8 ohm.

 

I think my next move will be to make a dummy MX645 decoder out of cardboard and see if I can make it fit in the space available.  It may be necessary to cut away part of the floor of the coal section.  If I can fit the 645 I'll then go for the largest speaker that will fit in the remaining space in the top of the bunker.  The 'stay alive' cap will have to go in the cab through a hole in the cab floor.

 

When the speaker is finally fitted in the coal space, I plan to cover it with mesh and then glue scale size lumps of coal to the top of the mesh, leaving sufficient air gaps to let the sound through.

 

If anyone has already fitted the MX645R decoder to a Hornby L1, or tried and failed, please let us know.

 

I will post again when I have more information, or have chopped up my new L1 beyond repair.  This is my current project so should have more in a few days.

 

BTW, I had to fit a spring to keep the L1 front pony truck on the rails.  Is yours OK Peter?

 

Alan

[Pete22]

Hi Peter,

 

I am also aiming to fit sound in the L1.  I have seen good reports of the Zimo decoders so it's a choice between the MX645R and the MX648R.  Both can be loaded by Digitrains with the Paul Chetter soundfile. This can be changed between heavy load or light engine sounds, and sounds change with acceleration and coasting.  See

 

http://www.digitrains.co.uk/ecommerce/dcc-sound/uk-sound/zs011-class-l1-tank-steam-soundfile.aspx

 

for details.  I would prefer the 645 as it's £8 cheaper (from Digitrains) and has 'stay alive' cap support.  The down side is it may be a couple of mm too long to fit in the bunker space, even if angled up over the DCC header.  The 648 is a later, and much smaller, decoder and would easily fit in the bunker space, but doesn't support a 'stay alive' cap.  I have already removed the coal from the top of the bunker and that space has a solid floor, measures 26x20mm internally, 9.5mm high at the sides and 12mm high at the centre.  This space is therefore large enough for the Loksound 16x25mm speaker. The 648 must have an 8 ohm speaker, whereas the 645 can be either 4 or 8 ohm, although I suspect the 4 ohm speaker may be overloaded at max volume, so I would prefer to use 8 ohm.

 

I think my next move will be to make a dummy MX645 decoder out of cardboard and see if I can make it fit in the space available.  It may be necessary to cut away part of the floor of the coal section.  If I can fit the 645 I'll then go for the largest speaker that will fit in the remaining space in the top of the bunker.  The 'stay alive' cap will have to go in the cab through a hole in the cab floor.

 

When the speaker is finally fitted in the coal space, I plan to cover it with mesh and then glue scale size lumps of coal to the top of the mesh, leaving sufficient air gaps to let the sound through.

 

If anyone has already fitted the MX645R decoder to a Hornby L1, or tried and failed, please let us know.

 

I will post again when I have more information, or have chopped up my new L1 beyond repair.  This is my current project so should have more in a few days.

 

BTW, I had to fit a spring to keep the L1 front pony truck on the rails.  Is yours OK Peter?

 

Alan

Hi,

Thanks for your reply & info.

You are probably ahead of me in the fitting process, as I have not yet got round to opening my loco yet. The Zimo range sounds interesting. Do post some updates and photos if possible !

My L1 seems to run rather well, no requirement yet to add a spring to the front pony truck, fingers crossed>...

 

Peter.

[Pete22]

One wonders who told you they are 'not too bad' and whether you will agree with them after fitting.

 

The problem with 'piggy back' decoders is that they take a an awful lot of effort to synchronise sound with motion and much midnight oil is burned attempting to do just that and with very mixed results.

 

I personally have no experience with MRC sound decoders apart from hearing one or two and deciding as a result that I would stick with the majority and opt for combined motor and sound decoders . I have personally wrestled with both CT and Digitrax piggy back decoders and one of the latter remains in my N1.

Hi,

Thanks for your reply. I read on a few posts somewhere that the sound on the MRC was not bad, and the users were well satisfied. My dilemma is that I have 2 unopened Hornby Sapphires and 2 new Bachmann chips, all of which I want to make use of, hence my thoughts on buying the MRC sound only decoders to link with them. However, what you say about sound sync problems worries me....I thought the chuff rate was designed to increase in line with the throttle setting ? but not so sure now. How does the Digitrax Sound Bug do this (sync), and would it be a better bet if used with my Sapphires ?

 

Product

http://www.modelrectifier.com/search/product-view.asp?ID=12276

Manual

http://www.modelrectifier.com/resources/RAILROAD/0001908.pdf

 

Many thanks,

Peter.

[pauliebanger]

Hi Peter,

 

I am also aiming to fit sound in the L1.  I have seen good reports of the Zimo decoders so it's a choice between the MX645R and the MX648R.  Both can be loaded by Digitrains with the Paul Chetter soundfile. This can be changed between heavy load or light engine sounds, and sounds change with acceleration and coasting.  See

 

http://www.digitrains.co.uk/ecommerce/dcc-sound/uk-sound/zs011-class-l1-tank-steam-soundfile.aspx

 

for details.  I would prefer the 645 as it's £8 cheaper (from Digitrains) and has 'stay alive' cap support.  The down side is it may be a couple of mm too long to fit in the bunker space, even if angled up over the DCC header.  The 648 is a later, and much smaller, decoder and would easily fit in the bunker space, but doesn't support a 'stay alive' cap.  I have already removed the coal from the top of the bunker and that space has a solid floor, measures 26x20mm internally, 9.5mm high at the sides and 12mm high at the centre.  This space is therefore large enough for the Loksound 16x25mm speaker. The 648 must have an 8 ohm speaker, whereas the 645 can be either 4 or 8 ohm, although I suspect the 4 ohm speaker may be overloaded at max volume, so I would prefer to use 8 ohm.

 

I think my next move will be to make a dummy MX645 decoder out of cardboard and see if I can make it fit in the space available.  It may be necessary to cut away part of the floor of the coal section.  If I can fit the 645 I'll then go for the largest speaker that will fit in the remaining space in the top of the bunker.  The 'stay alive' cap will have to go in the cab through a hole in the cab floor.

 

When the speaker is finally fitted in the coal space, I plan to cover it with mesh and then glue scale size lumps of coal to the top of the mesh, leaving sufficient air gaps to let the sound through.

 

If anyone has already fitted the MX645R decoder to a Hornby L1, or tried and failed, please let us know.

 

I will post again when I have more information, or have chopped up my new L1 beyond repair.  This is my current project so should have more in a few days.

 

BTW, I had to fit a spring to keep the L1 front pony truck on the rails.  Is yours OK Peter?

 

Alan

 

Alan,

 

Think laterally! The MX645 will fit in one of the side tanks. See my Thomas project in the current (issue 68) Hornby Magazine, or my L1 in next month's issue.

 

Paul

[Rombald]

Alan,

 

Think laterally! The MX645 will fit in one of the side tanks. See my Thomas project in the current (issue 68) Hornby Magazine, or my L1 in next month's issue.

 

Paul

Thanks Paul, I hadn't thought of that and that will leave space for caps in the bunker.  Which speaker do you recommend?  I was considering a rectangular speaker in the top of the bunker and possibly a couple of small round speakers either side of the metal block in front of the motor, so that high frequencies come from near the cylinders, or is that a waste of effort?  The speakers would be connected in series/parallel to make 8 ohms.  I will certainly buy the next Hornby mag to see your L1 project.

 

Alan

[pauliebanger]

Alan,

 

I'm sorry, I can't say more until the mag's published. This is why I don't normally say what's coming up in future HMs. But you asked specifically about the fitment of MX645, and I wanted to give you a 'steer' before you started cutting up your model.

 

It's possible to get a good result without making any changes/mods to the L1 model, except to remove the DC blanking plug for the decoder to be connected!

 

Kind regards,

 

Paul

[Lady_Ava_Hay]

Hi,

Thanks for your reply. I read on a few posts somewhere that the sound on the MRC was not bad, and the users were well satisfied. My dilemma is that I have 2 unopened Hornby Sapphires and 2 new Bachmann chips, all of which I want to make use of, hence my thoughts on buying the MRC sound only decoders to link with them. However, what you say about sound sync problems worries me....I thought the chuff rate was designed to increase in line with the throttle setting ? but not so sure now. How does the Digitrax Sound Bug do this (sync), and would it be a better bet if used with my Sapphires ?

 

Product

http://www.modelrectifier.com/search/product-view.asp?ID=12276

Manual

http://www.modelrectifier.com/resources/RAILROAD/0001908.pdf

 

Many thanks,

Peter.

 

The piggy back concept is that the sound decoder is linked only to the pick ups and has a motor simulated load on the chip. The motor itself has its own chip and the two do not 'talk' to each other. Thus you have to lock out the sound chip, adjust the CV;s to give the right performance, lock out the motor chip, unlock the sound chip, adjust CV's almost blind as to effect but mirroring the motor chip CV values where possible, lock out the sound chip, test and then repeat ad infinitum until a passable result is heard. My Bachmann N class still chuffs but doesn't move at speed step 1 or 2 but is in perfect synch above 3 this took in excess of five hours to achieve. This sort of thing is not uncommon with these types of sound decoders.

 

As to the quality of the sounds, it is a fair estimate that if the memory on the chip is too low, the decoder will try all sorts of stunts to deceive the ear into believing that it is fully in sync with the loco. One listen to a properly loaded and modern sound decoder in comparison with the MRC will convince you. The quality of the sounds themselves is very much the poor cousin to memory but even there there is no comparison. Bear in mind also that MRC sound decoders are principally designed with the American market in mind. I believe there is one available that doesn't have a bell!

 

Sound is not cheap and there are no short cuts although many are offered. Be aware though that manufacturers and indeed RTR sound chip suppliers have all gone the route of using ESU and lately Zimo because the quality (saleability) of the finished product is way more than its price differential.

 

The Digitrax Sound Bug is designed to fit onto a Digitrax decoder that has the fittings to do that. I and several other people have not yet been able to load sounds onto a Sound Bug that play at any time ever. Be aware that the Sound Bug has a very small memory and a minuscule sound power output.

[Pete22]

Hi, Dwhite4dcc,

Many thanks for taking time to provide such a comprehensive answer !

I think you have convinced me to go with Zimo instead of MRC sound only decoders.

Shame I have 2 x Sapphires and the 2 Bachmann decoders...... what a waste.

I would have thought for example Hornby would spot this gap in the market and introduce a sound only decoder that can connect (and sync) to their motor decoders. Otherwise, there is no method for their customers to upgrade to sound without ditching the motor decoder and then investing heavily in a new combined sound / motor decoder.

Not that I know anything about sound decoders, but I thought if I make the sound decoder have the same address as the motor decoder, then I could adjust the CV's on both at the same time ?

 

Peter...

[Lady_Ava_Hay]

 but I thought if I make the sound decoder have the same address as the motor decoder, then I could adjust the CV's on both at the same time ?

 

You can but there is the very real danger that many of the CV's in the sound decoder are not mirrored or even present in the motor decoder and vice versa so a command to a CV in that instance will fail.

 

I appreciate your argument about upgrading and you can bet your bottom dollar that Hornby and Bachmann investigated this avenue but rejected it on the basis of customer satisfaction/warranty claims.

 

That in the face of a reduction in costs that would be very attractive. At the same time though, H and B are not in the business of allowing or wanting the customers or indeed the dealers probing about in their products retro fitting upgrades to a loco that wasn't designed to take that upgrade. Non starter commercially for many other reasons.

[pauliebanger]

Hi, Dwhite4dcc,

Many thanks for taking time to provide such a comprehensive answer !

I think you have convinced me to go with Zimo instead of MRC sound only decoders.

Shame I have 2 x Sapphires and the 2 Bachmann decoders...... what a waste.

I would have thought for example Hornby would spot this gap in the market and introduce a sound only decoder that can connect (and sync) to their motor decoders. Otherwise, there is no method for their customers to upgrade to sound without ditching the motor decoder and then investing heavily in a new combined sound / motor decoder.

Not that I know anything about sound decoders, but I thought if I make the sound decoder have the same address as the motor decoder, then I could adjust the CV's on both at the same time ?

 

Peter...

 

Peter,

 

We've only spoken about the sound aspect so far. Both ESU and ZIMO have far better and more configurable motor control than the basic non-sound decoders you mention. But all is not necessarilly lost anyway - depends on what you intend to model. There are several offerings, DMUs, which need two decoders. A motor (or sound and motor) decoder to propel the model and one in the other car to work the lights, and you don't need anything fancy for that.

 

Having a couple of 'spare' decoders which you can use for swapping over for trouble shooting might seem extravagent at the moment, but if you get into sound in a big way (and that can easilly happen!), the few quid 'lying idle' will seem insignificant. Far better to find out now than chucking more money tryng to upgrade with something that you may not be happy with in the end.

 

Many of us have been tempted by the prices of these budget sound solutions. Very few here would recommend any of them, as you will see if you search the site.

 

It's also relatively straightforward to get ESU or ZIMO decoders re-blown with new sounds and they are arguably the best choice for British outilne sounds.

 

Kind regards,

 

Paul

[Rombald]

Hi,

Thanks for your reply & info.

You are probably ahead of me in the fitting process, as I have not yet got round to opening my loco yet. The Zimo range sounds interesting. Do post some updates and photos if possible !

My L1 seems to run rather well, no requirement yet to add a spring to the front pony truck, fingers crossed>...

 

Peter.

Peter,

 

I have now ordered a Zimo 645 decoder and a Loksound 50326 'self-adhesive' speaker.  The Loksound catalogue claims the sound from this speaker is "amazingly good".  We'll see!  Now that I've had time to look closely inside the L1 and measure up, I'm confident the decoder and speaker will fit in the side tanks, one either side. Thanks again to Paul for suggesting this.  I particularly want capacitor 'stay-alive' and there's room in the bunker for a couple of 2200u caps.  I'll post again when I have everything installed.

 

Alan

[Rombald]

Hi, Can anyone help ?

 

I wish to fit a sound chip & speaker into a new Hornby Thompson L1 (DCC ready) tank loco.

I searched the web but can't find any fitting guides or info regarding which speaker to fit, and where it can be placed in the loco.

 

Has anyone converted one of these before ? I am keen to learn before I start pulling it apart !

 

Many thanks,

Peter...

Peter,

 

I have made some progress with the sound installation on my L1. I have now fitted the Zimo 645 decoder and a Loksound 50326 speaker in the side tanks.  The Zimo decoder is excellent.  I connected a couple of 1000uF caps for 'stay alive' and it works like a dream without any hesitations on the track. The caps are in the bunker space but I did have to rewire the Hornby rats nest to give maximum space. The Paul Chetter sound files are also excellent, as expected, but the tiny Loksound speaker is not so good.  It has a smooth response but as it only measures 12x14mm I didn't expect low frequencies to be very loud, and so it proved. Whistles, steam and low speed 'chuffs' are all good but high speed exhaust 'chuffs' are just not loud enough, even with the volume CV set just below distortion level. I looked at the 645 speaker output on a 'scope and found it is PWM (Pulse Width Modulated) so not so simple to measure accurate audio levels but it is possible to see approx pulse width variations with the differant sounds.  This showed that the high speed 'chuff's are more than twice the amplitude of the low speed 'chuffs' but because the low frequency content is greater on the high speed exhaust beats, that part of the audio is lost with this small speaker.  I have ordered a couple of alternative speakers to try and am confident one of those will be an improvement.  What I have now is good, but it could be better.  I'll post again when I've tried the alternative speakers.

 

Alan

[Rombald]

Hi, Can anyone help ?

 

I wish to fit a sound chip & speaker into a new Hornby Thompson L1 (DCC ready) tank loco.

I searched the web but can't find any fitting guides or info regarding which speaker to fit, and where it can be placed in the loco.

 

Has anyone converted one of these before ? I am keen to learn before I start pulling it apart !

 

Many thanks,

Peter...

 

Here are some pictures of my L1 mods:

The MX645 decoder.  The stay alive caps are wrapped in yellow tape:

The Loksound 50326 speaker:

The Hornby wiring to the DCC socket:

DCC socket after rewire:

 

Alan

[Pete22]

 

Here are some pictures of my L1 mods:

The MX645 decoder.  The stay alive caps are wrapped in yellow tape:

210113 0029b.jpg

The Loksound 50326 speaker:

210113 0030b.jpg

The Hornby wiring to the DCC socket:

130113 L1 DCC socket before tidy.jpg

DCC socket after rewire:

210113 0037b.jpg

 

Alan

Hi Alan,

The photos are really great, very clear and close up ! 

Hope you can post some pics of your choice of replacement speaker to the Loksound one,  and let us know about  the sound difference. I am struggling with building a platform at present using Peco edging with balsa & wet n dry sand paper top, so no progress with my sound conversion yet.

 

Peter...

[Rombald]

 

Hi Alan,

The photos are really great, very clear and close up ! 

Hope you can post some pics of your choice of replacement speaker to the Loksound one,  and let us know about  the sound difference. I am struggling with building a platform at present using Peco edging with balsa & wet n dry sand paper top, so no progress with my sound conversion yet.

 

Peter...

Peter,

 

I have now finished fiddling with my L1 sound.  I'm certainly not an expert and many others will have done similar work, probably with better results, but here are my conclusions:

 

I tried a couple more speakers and I think my final choice gives satisfactory sound, considering the space limitations.  The three speakers tried are:

 

ESU 50326 14x12mm 8ohm.  I thought this speaker had a smooth response but poor low frequencies, as mentioned before.

 

50330 Loksound 4 ohm.  16 x 25 mm rectangular with enclosure. The sound was resonant with poor low frequency response.  A larger, better sealed enclosure would probably have improved the LF but I abandoned this approach due to insufficient space in the side tanks of the L1, and I wanted to use the bunker space for the ‘stay alive’ capacitors.

 

CT Electronik ‘Sugar cube’ 8 ohm.  15x11x8 mm including the supplied enclosure.  I found this speaker to be the best of the three and it has been given good reports elsewhere.  It is sufficiently loud, even though the speaker is 8 and not 4 ohm.  The response is smooth, similar to the ESU 50326, but I think this speaker, when used with the supplied enclosure, has better LF response than the ESU 50326. I believe it is true to say that good LF response is all about shifting as much air as possible, with as large an enclosure as possible to reduce damping due to the trapped air. The supplied enclosure has an internal volume of just under 0.4 cc. To try and improve the LF of this speaker I built an enclosure from 1.6mm Plasticard with external measurements of 34 x 13 x 6 mm.  The speaker was fitted inside, with the diaphragm facing out, to keep the width of the enclosure within the available space.  I had to cut away part of the side walls inside the enclosure to allow sufficient space for the speaker, taking care that the enclosure was airtight.  Allowing for the volume of the speaker, the internal volume of the new enclosure is about 1.1cc.  The LF response with this larger enclosure is, I think, an audible improvement over the supplied mini enclosure. However, using the new enclosure I find the whistle on F2 causes a very short overload at its' start, audible as a click, so I need to tweak the F2 volume down with CV#300.  I suspect this particular sound file has a large LF component at the start that is normally damped by the smaller enclosure but not so much by my larger enclosure.  This is NOT a criticism of the sound files which are excellent. The enclosure dimensions stated will just fit in the space available in the side tank of the L1 and, if fixed in contact with the top of the tank, will clear the rims of the driving wheels.

 

I removed the original coal, and the floor of the bunker, to make room for the ‘stay alive’ capacitors so now I need to add a new load of coal to the bunker, and a driver in the cab, and my L1 will be finished.

 

This is my first attempt at adding sound to a loco and I acknowledge that many others have far more experience and knowledge but I enjoy the 'problem solving' aspect of the hobby. It is impossible to recreate the full power of the real thing but I think I now have a good compromise and I’m happy with the result.

 

 

Here are some pictures:

 

The 'Sugar Cube' speaker and the enclosure, before it was sealed:

 

 

 

The new enclosure with the one supplied with the speaker:

 

 

The enclosure fitted inside the loco body:

 

 

 

Finally, here's a short movie clip of the finished L1.  I think the sound is coloured by the workbench and the fact that the camera mic is on top of my camera and not facing the loco, but it gives the general impression.

 

 

'Hope all this is of interest.

 

Alan

[pauliebanger]

Alan,

 

Very ingenious and more 'progressive' than my installation - see Hornby Magazine this Friday.

 

If you look at the orientation of the sugar cube speaker with its original resonator, you will see that the 'box' fits on the face which you would expect to be open with a conventional speaker.

 

That is to say, I think you have fitted the cut-down sugar cube the wrong way around in your new enclosure. The face with the speaker wire clips should be 'outwards'.

 

Reversing this should increase the volume and help dampen the F2 whistle at the same time.

 

Kind regards,

 

Paul

[Rombald]

Alan,

 

Very ingenious and more 'progressive' than my installation - see Hornby Magazine this Friday.

 

If you look at the orientation of the sugar cube speaker with its original resonator, you will see that the 'box' fits on the face which you would expect to be open with a conventional speaker.

 

That is to say, I think you have fitted the cut-down sugar cube the wrong way around in your new enclosure. The face with the speaker wire clips should be 'outwards'.

 

Reversing this should increase the volume and help dampen the F2 whistle at the same time.

 

Kind regards,

 

Paul

Thanks for the feedback Paul

 

I accept that you have far more experience in this field but I'll go through my thinking on this.

 

My initial tests were indeed with the speaker mounted on the 'resonator' with the diaphragm facing into the 'resonator', as intended by the manufacturer.  However, my new enclosure would have to be stepped to prevent a speaker mounted outside the enclosure from making the whole assembly too wide.  I did not detect any difference in volume when I changed the direction the speaker was facing but I don't have any SPL measurements to back up that impression.  If we assume the holes in the four corners of the speaker backplate do not significantly restrict the movement of air molecules (a good assumption or the speaker wouldn't work on the supplied 'resonator'), and if the speaker is well sealed to the enclosure, the damping effect from the air trapped inside the enclosure should be the same either way, although the speaker magnet/back-plate will slightly reduce the volume of air trapped inside the enclosure.

 

It is my understanding that the air trapped inside the enclosure acts like a spring, raising the resonant frequency of the speaker diaphragm above it's resonant frequency in free air.  The smaller the enclosure, the stronger the 'spring' and the higher the resonant frequency.  Increasing the volume of the enclosure will therefore lower the resonant frequency, although it will always be higher than it's resonance in free air.  If the resonant frequency is lower, the LF component of the signal applied to the speaker will cause a greater deviation of the diaphragm and, in the case of the F2 whistle, momentarily hit the 'end stop'. I am happy to adjust the F2 level as a trade-off for improved LF response.

 

I look forward to reading your article on Friday.

 

Regards

 

Alan

[pauliebanger]

Alan,

 

I understand your reasoning, and the actual practice of mounting the speaker the other way would indeed be a problem to solve.

 

You also have the empirical evidence of your own ears.

 

I liked the boldness of your approach; I have made modified enclosures for these in 'N' gauge.

 

I was not being critical, I hope you got that from what I said. I mentioned it only because I have, in the past, 'blown' this type of speaker when running 'free to air' without the resonator fitted.

 

If it works for you,and you are careful with the volume levels, then it's a good installation.

 

And for your first - excellent.

 

Kind regards,

 

Paul

[Rombald]

Alan,

 

I understand your reasoning, and the actual practice of mounting the speaker the other way would indeed be a problem to solve.

 

You also have the empirical evidence of your own ears.

 

I liked the boldness of your approach; I have made modified enclosures for these in 'N' gauge.

 

I was not being critical, I hope you got that from what I said. I mentioned it only because I have, in the past, 'blown' this type of speaker when running 'free to air' without the resonator fitted.

 

If it works for you,and you are careful with the volume levels, then it's a good installation.

 

And for your first - excellent.

 

Kind regards,

 

Paul

Paul,

 

Many thanks for your helpful comments.

 

Alan

[torikoos]

Indeed, I fully agree with Paul.  

If it works, leave well alone, trust your ears.   For your next install, I'd say try it out first the other way around. I did the same thing on a loco of mine, fully expecting the sound coming from the other side of where the wires attach on conventional speakers, but sugar cubes are build a bit odd, and the 'forward' face of the speaker is actually the same side as the wires.  

So perhaps worth a try to turn it around for the next one and see if there's an improvement to your ears, or not. Whatever the case may be.