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Author Topic: Sound System  (Read 2120 times)

stoney

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Sound System
« on: January 04, 2011, 04:35:20 PM »


 Hi Gents

 I've used some 4" plastic tube and fitted the speakers to the ends . The sound units are the P100's with the Trent diesel engine sound . The speakers are loud enough
 but very ' tinny ' would the speakers be better fitted into wood cases .


                                      Thanks Paul
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malcolmfrary

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Re: Sound System
« Reply #1 on: January 04, 2011, 06:03:34 PM »

Are the bottom ends of the tubes closed?  If not, the sound coming off the back will cancel the sound coming off the front when used as in the picture.
You normally have to regard the boat itself as the speaker cabinet - the speakers should face outwards, the rest of the hull should be pretty much sealed to act as a cabinet.  The deepest note is then a function of the longest straight line dimension.
Are the two speakers on separate channels or a pair?  A pair of speakers handling mono with one out of phase with its mate can give nasty results, answer in that case is to reverse the connections of one of them.
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stoney

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Re: Sound System
« Reply #2 on: January 04, 2011, 06:25:51 PM »

 
 Hi malcolmfrary

 Yes the bottom ends are closed , and the speakers are on separate channels . Does any body know if there is some padding that can be put in the tubes ?


                                 Thanks Paul
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Stavros

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Re: Sound System
« Reply #3 on: January 04, 2011, 08:28:49 PM »

Top tip get rid of the tubes,make bulkhead where the speakers are located,cut holes for speakers but make sure you put a divider between both speakers,as one wil counteract the other well worth it.I fitted a single speaker on my eldergart and used ACTion amp on it The sund can be heard 100 yds away



Stav
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malcolmfrary

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Re: Sound System
« Reply #4 on: January 05, 2011, 10:58:53 AM »


 Hi malcolmfrary

 Yes the bottom ends are closed , and the speakers are on separate channels . Does any body know if there is some padding that can be put in the tubes ?


                                 Thanks Paul
Papier mache egg box pieces and fibreglass loft insulation spring to mind.  I've also used dense foam carpet underlay for the same job.  Either will cut internal reflections in the small cabinets that have been made.  For deep, throbbing bass without using the modern HiFi techniques of pre-distorting the signal to make a small speaker sound like a big 'un, a big box is needed, much like Stavros has arranged. 
Whenever cabinet padding is used, efficiency suffers.  With domestic HiFi, this is relatively unimportant since its easier to reduce the efficiency of the rest of the system to match, then use a bigger amplifier to get the required volume because the thing is powered from the mains.  With battery power on a boat, this is not usually an option.
A full set of connections does exist between source and amplifier input?  Just a thought, since a disconnection or wrong value of capacitor in between the source and amplifier input can act as a high pass filter, remove the bass and give a tinny effect.  Again, if the same sound if being presented through each speaker, watch out for phasing.
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stoney

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Re: Sound System
« Reply #5 on: January 05, 2011, 04:27:27 PM »


 Thanks Guys

 Your advice and help taken onboard.I will fit some ply horizontally cut out the holes so the speakers are facing up into the wheelhouse and hopefully this will improve the
 sound quality.

                                        Thanks Paul
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wombat

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Re: Sound System
« Reply #6 on: January 22, 2011, 11:03:02 PM »

If you have sealed the back of the speaker, you will prevent the sound from propagating out. The energy of the speaker will be dissipated in trying to compress the air sealed in the tube. More than that, the pressure in the tube will prevent the cone from transmitting the movement of the coil to the edge of the speaker cone - the cone will deform. This will make the propagation of bass very inefficient.

I would suggest a port in the speaker tubes and acoustic wadding

Wom
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stoney

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Re: Sound System
« Reply #7 on: January 22, 2011, 11:31:44 PM »


 Hi wombat

 What size hole shall i drill in the bottom of the tubes ?


     Thanks Paul














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malcolmfrary

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Re: Sound System
« Reply #8 on: January 23, 2011, 11:48:03 AM »

Start with about 1/4".  This is small enough to let the pressure in and out, but not so small as to induce whistling as the displaced air passes through.  Making a hole bigger is easy - making it smaller less so.
Wadding as Wombat suggests is good - it breaks up the pressure waves inside the enclosure and reduces internal reflections to the back of the speaker cone.
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John W E

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Re: Sound System
« Reply #9 on: January 23, 2011, 12:25:48 PM »

Hi ya there Paul,

When I first fitted the sound unit in the RTTL build, I played round for a while with a plastic Christmas Pudding dish for a backing for the speaker with varying bits of success but it still didnt sound right.   There seemed to be a lot of background noise/vibration coming from the enclosure.  So I dispensed with that idea; and I had a look at a few speaker enclosures on the web (homemade ones), also I came across a picture of an old JJC unit with the speaker mounting and that speaker mounting was like an elbow shape.  This elbow shape was supposed to enhance the sound - so - I set about building a form of reflex speaker box and this was the end product.   The back of the speaker is open, and the bow of the boat acts as a form of amplifier to the sound.  If you would like verification of how loud this unit is coming from this little four-inch speaker, I think Mr ACTion can confirm this as it was on show at the South Shields show on their stand and it could be heard in the 4 corners of the show room.

aye
john
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Geoff Cropper

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Re: Sound System
« Reply #10 on: February 13, 2011, 07:58:32 PM »

If all else fails, just put a plastic tie-wrap round the propshaft without cutting the end off.      Great motor sound and proportional too. {-) {-) {-) {-) O0 O0 O0   Geoff
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allanb131

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Re: Sound System
« Reply #11 on: February 14, 2011, 09:41:02 AM »

Neat job thank you will use this idea in my Eskgarth.
Busy trying to move right now so project has ground to a halt.

Regards Allan.
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