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Subwoofers
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 Posted: Tue Apr 2nd, 2019 09:48 pm
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Stan S
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So...True confessions, I'm an audio guy.

I'm building a small On30 layout.

Is there a way, maybe with a stationary decoder, to drive a fixed-location subwoofer?

There's a whole lot of bass that a 3/4" speaker can't make.


Stan




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 Posted: Tue Apr 2nd, 2019 10:51 pm
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Si.
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Hi Stan  :wave:



I've found that an Eminence Beta-15" is hard to beat when it comes to ... BASS !!  :pimp:





You're right Stan ... it's not really very practical for an On30 tender !!  :shocked:

Does a great job on getting an UNBEATABLE sounding B-zero though.  :cool:


;)


There is quite possibly a 'certain amount' of bass, coming from sound-decoder audio outputs.

I guess it rather depends on the sound-file itself & if the specific decoder 'limits' the low frequencies.



Just a word of warning concerning the connection of sound-decoder outputs to larger external amplifiers ...

... the amplifier on the sound-decoder board, is almost certainly a 'digital-amplifier' ...

... connecting the sound output of the board, to the 'line level input' of say a regular hi-fi amplifier ...

... will almost certainly I think FRY ! the board !!  :shocked: :shocked: :shocked: :shocked: :shocked:



An 'impedance-converter' needs to be connected between the sound-decoder & hi-fi amplifier.



I think you could connect it directly to a 15" loudspeaker ^^ though ...

... as it's just a 'regular' 8-Ohm load, albeit a rather LARGE one !  :shocked:



Juergen has put together a  C :cool: :cool: L  'box of tricks' using an 'impedance-convertor' ...

... to connect his loco-sound to a larger external hi-fi amplifier & loudspeaker.

He was getting excellent results I believe & has since been tweeking it a bit as well ...

... using an exceptionally 'steampunk' vacuum-tube amplifier !  :P



:)



Si.




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 Posted: Wed Apr 3rd, 2019 02:08 pm
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bobquincy
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I have ported the speaker output of one of my trains (monorails) to a stereo receiver input, it sounds *much* better,
so there is plenty of bandwidth in the original signal that the 30mm onboard speaker can't reproduce. 

Most inputs to receivers/amplifiers are capacitor coupled (AC coupled)
and can accept (actually eliminate) the potential DC offset of the audio board output.
Adding a capacitor to the circuit may slightly reduce the low frequency response but adds some safety.

One of the output leads has to be ground potential to match the ground side of the input.
If not, we probably need transformer coupling.

Some amplifiers have a DC coupled input, that can be real trouble,
as the amplifier tries to amplify the DC offset, usually with disastrous results for the speaker.

The input to the "subwoofer" should rolloff any frequencies above true bass,
to reduce the tendency to detect the direction of the source of the bass sounds. 

I note "subwoofer" because to me if I can pick it up it is not a real subwoofer!   ;)




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 Posted: Wed Apr 3rd, 2019 08:15 pm
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Si.
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Hi again Stan  :wave:



I previously mentioned ^^ the solution which Juergen & I came to ...  :thumb:

... for connecting the sound-decoders 'digital-amplifier' output, to larger external amplifiers ...

... without FRYING !  the sound-decoder board !!  :shocked: :shocked: :shocked: :shocked: :shocked:


I called it an 'impedance convertor' ...  :brill:

... as this is what the device is known as, if you happen to be searching on eBay for one.  :P





It is in fact, just a pair of 'isolation-transformers', similar to what you'd find in a geeetar DI-box.  :cool:

Only 1 channel is used, as I don't believe there are any 'stereo' loco sound-decoders out there.  L:



It's easy to understand, simple & cheap, at something like a $1 Buck inc. P&P ...  :)

... & it should guarantee 100% ...

... that you won't be looking at $100 Bucks worth of FRIED !  sound-decoder !  :f:



:pimp:



Si.




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' M:R:W Motor Speedway !!! ' - 1:32 Slotcar Racing Layout
http://www.slotforum.com/forums/index.php?showtopic=59295&st=0&a
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 Posted: Thu Apr 4th, 2019 06:27 am
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Toeffelholm
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Si. wrote:
... Juergen has put together a  C :cool: :cool: L  'box of tricks' using an 'impedance-convertor' ...

... to connect his loco-sound to a larger external hi-fi amplifier & loudspeaker.

He was getting excellent results I believe & has since been tweeking it a bit as well ...

... using an exceptionally 'steampunk' vacuum-tube amplifier !  :P  ...



No, I'm afraid not Si.  Didn't proceed on this since then.

To divide high and low frequencies and sending them to the loco and to a separate speaker under the layout sounds good so far,
but in the end not quite satisfying for me.

My impression is, that the frequency spectrum of the used 'Phoenix Sound' device is not sufficient for the effect I'm after. 

So it's still in the stadium of my test setup.





For further interest here's the link to the "Replicant" thread.  The Repilicant

But my part is completely RC based, so may be in detail not of interest for a DCC user.


Juergen




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 Posted: Fri Apr 5th, 2019 03:05 am
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Si.
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Hi Guys  :wave:



Most of the fairly long conversation Juergen & I had about all this, was done by eMail ...

... so there isn't a full description of what was done, or how it was got to, on the Site.


As Juergen said, his installation was radio-control based ...  :brill:

... it was also quite complex, using 2 sound-decoders & transmitting the sound via. 'Bluetooth'.



One thing, again, easy to understand, simple & cheap, which was used ...

... is this 'low pass filter' bought from eBay for a couple o' Bucks inc. P&P.





This simple audio board, allows low-frequency content to be output, separate from the higher-frequencies.



The 'frequency adjustment' control is centred on 300 Hz I seem to recall ...  L:

... & can be adjusted easily, to 'subjectively' get the 'non-directional' low-frequency point you like best.



Personally I have nothing much good to say about subwoofers !  :td:

I own & use every conceivable piece of audio equipment & loudspeaker under the sun ...

... but have never owned, or wanted to own, a subwoofer, cos I've never heard a good one.  :f:


In attempting anything like this, I would simply use a regular hi-fi speaker, of pretty much any sort ...  :old dude:

... since the bass response, in my opinion, would be more than adequate for almost every circumstance.  :thumb:



Subwoofers are great at making those kinda annoying rumbling farting noises in the background of Hollywood movies ...  :f:

... or ruining the sound, of a perfectly good pair of hi-fi speakers.  :P



Just my 5-Cents worth !  ;)



:pimp:



Si.




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' Mysterious Moose Mountain ' - 1:35n2 - pt.II
http://www.freerails.com/view_topic.php?id=7318&forum_id=17&page=1

' M:R:W Motor Speedway !!! ' - 1:32 Slotcar Racing Layout
http://www.slotforum.com/forums/index.php?showtopic=59295&st=0&a
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 Posted: Sat Apr 6th, 2019 02:45 pm
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Stan S
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Wow, lots of good info here,

thanks for all the good responses guys!






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 Posted: Sat Apr 6th, 2019 02:51 pm
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Stan S
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Si. wrote: Hi Guys  :wave:



Most of the fairly long conversation Juergen & I had about all this, was done by eMail ...

... so there isn't a full description of what was done, or how it was got to, on the Site.


As Juergen said, his installation was radio-control based ...  :brill:

... it was also quite complex, using 2 sound-decoders & transmitting the sound via. 'Bluetooth'.



One thing, again, easy to understand, simple & cheap, which was used ...

... is this 'low pass filter' bought from eBay for a couple o' Bucks inc. P&P.





This simple audio board, allows low-frequency content to be output, separate from the higher-frequencies.



The 'frequency adjustment' control is centred on 300 Hz I seem to recall ...  L:

... & can be adjusted easily, to 'subjectively' get the 'non-directional' low-frequency point you like best.



Personally I have nothing much good to say about subwoofers !  :td:

I own & use every conceivable piece of audio equipment & loudspeaker under the sun ...

... but have never owned, or wanted to own, a subwoofer, cos I've never heard a good one.  :f:


In attempting anything like this, I would simply use a regular hi-fi speaker, of pretty much any sort ...  :old dude:

... since the bass response, in my opinion, would be more than adequate for almost every circumstance.  :thumb:



Subwoofers are great at making those kinda annoying rumbling farting noises in the background of Hollywood movies ...  :f:

... or ruining the sound, of a perfectly good pair of hi-fi speakers.  :P



Just my 5-Cents worth !  ;)


Good stuff, Si.

I agree it doesn't really need to be a subwoofer,
any speaker that can make bass down to even 100 Hz would be fine.

Part of my rationale for the subwoofer,
was that it would naturally roll-off the high end,
eliminating the need for a low pass filter or crossover.

The grounding issue is interesting,
the speaker output of a typical DCC board is probably floating,
since unlike DC systems, there is no reference to ground on a DCC system,
or am I missing something?




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 Posted: Sun Apr 7th, 2019 01:08 am
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bobquincy
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Semi off-topic:

Before synthesizers there was little music with true subwoofer content,
*but* if you ever heard Bach played on an organ with a 32' pipe,
you would certainly miss the experience when you played it at home without a subwoofer.

Back then most vinyl and turntables could not reproduce those frequencies anyway.


Jumping ahead to now:

I am certain a steam or diesel locomotive produces frequencies below 100 Hz.
Whether we feel those sounds add to the experience or not may be a matter of taste.
 
In a special sound booth I listened to the sounds of a passing steam locomotive,
it was impressive and I would miss not hearing those low frequencies.




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 Posted: Thu Apr 11th, 2019 07:00 pm
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Si.
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" The grounding issue is interesting,
the speaker output of a typical DCC board is probably floating,
since unlike DC systems, there is no reference to ground on a DCC system,
or am I missing something? "



Hi Stan  :wave:



Yeah ... "floating" is 'kinda' what I'd call it, I suppose.  L:


Although unlike a 'floating' analog-audio circuit ...  :brill:

... the DCC sound-decoder boards 'digital-amplifier' output ...

... I don't think even has reference to 0 Volts, on the actual board either.  :us:



This is why you have to be VERY careful ...

... if you want to connect its output to other 'electronics', like an external hi-fi amplifier input.



I figure a DCC sound-decoder, using ^^ my 'Eminence' Beta 15" would be pretty darn LOUD ! ...

... I think the 15" is something like 105dB for 1 Watt @ 1 Meter !  :shocked:



Madonna in mono on it, with no additional high-frequency driver, sounds INSANE  :Crazy:  in my kitchen !  :P

Todd Trainers drum set, on 'Shellac' recordings sounds AWESOME on the 15 !  ;)



Anyone remember the BIG ! old vintage 'Karlson' 15" (often mono) loudspeaker cabinets ?  :old dude:



:!:



Si.




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' Mysterious Moose Mountain ' - 1:35n2 - pt.II
http://www.freerails.com/view_topic.php?id=7318&forum_id=17&page=1

' M:R:W Motor Speedway !!! ' - 1:32 Slotcar Racing Layout
http://www.slotforum.com/forums/index.php?showtopic=59295&st=0&a
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