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Author Topic: Sound units, your thoughts  (Read 4742 times)

pakirk

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Sound units, your thoughts
« on: December 27, 2007, 08:31:26 PM »

Sound units, your thoughts
Hi all.
As you may probably know I am developing new sound units to replace the missed JJC units.

I need your input.

The AMP as you will know from the JJC units get quite hot.
There are several options to cool them I would like you thoughts.

Heat-sync:- To do this properly a LARGE expensive heat-sync is required, this is because in a model there is no air flow to cool the heat-sync.

Force cooled FAN:- This is another option witch reduces the size of the Heat-sync required. But increases the maintenances. These fans are only designed to run <4000 hours.

Water cooled:- Small compact reduces cost. The down side is, you need a pump and plumbing is not everybody’s cup of tea. Pumps and water lines also clog up.

What would you prefer??
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DickyD

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Re: Sound units, your thoughts
« Reply #1 on: December 27, 2007, 08:35:05 PM »

Something similar to the JJC, they work OK in my GRP hulls. O0
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John W E

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Re: Sound units, your thoughts
« Reply #2 on: December 27, 2007, 08:35:28 PM »

Hi there

What size wattage output are you talking about?  ..... when you say you will need a huge heat sync?

aye
john e
bluebird
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red181

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Re: Sound units, your thoughts
« Reply #3 on: December 27, 2007, 08:42:23 PM »

my short experience with 2 x jjc units was that they where VERY VERY hot, too hot to be comfortable in a wooden "damp" boat. Water cooling would be fine with me as my boats are water cooled anyway, and a fan would be fine as I have plenty of room, an old computer fan works fine!
THe sooner they are on the market the better, but I would like to hear them, dont want the robbe "angry wasp" sound!!
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funtimefrankie

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Re: Sound units, your thoughts
« Reply #4 on: December 27, 2007, 08:47:22 PM »

Surely a computer fan would last years in a model boat, a model boats run hours must be far less than a computer.
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pakirk

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Re: Sound units, your thoughts
« Reply #5 on: December 27, 2007, 09:07:31 PM »

WOW quick response.
DickyD, non’t mean to correct you but a can assure you they get HOT. I have over 50 JJC units in for repair. Most of them and amps are burn out with heat, some the PCBs have charred.
Philips recommend a very large vary large heat-sync 60x 75x10mm.

Bluebird, Not an easy question to answer. The max on the basic model I am doing is 15Wats using the same AMP as JJC did “Nice AMP”.
The wattage actually disperses varies to the sound frequency and amplitude , voltage and speaker.  The lower the frequency and larger the amplitude the higher the wattage.

People want the lower frequency to get that rumbling thumping effect.
The JJC Turbo-Cat had the lowest Frequency and the larger amplitude and dispersed approx 12Watts of power and got extremely HOT.

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longshanks

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Re: Sound units, your thoughts
« Reply #6 on: December 27, 2007, 09:54:37 PM »

Hi Pakirk,

Great to hear they may be a replacement coming for JJC sound units. I was looking to buy when I read on this forum it seemed to be going pear shaped - thanks guys.

Vis yr question (might be a dumb answer) is it possibe to offer perhaps a couple of options at time of purchase or will this push the cost up.

Regards longshanks
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banjo

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Re: Sound units, your thoughts
« Reply #7 on: December 27, 2007, 09:58:58 PM »

An enterprising fellow should be able to incorporate the "very very hot" heat sink into the pipe of the smoke unit and produce a "Sound & Smoke" unit???

 O0
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Stan

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Re: Sound units, your thoughts
« Reply #8 on: December 27, 2007, 10:17:30 PM »

Hi Guys .

Surely is it not possible to incorporate a small tube  built on to the sound unit amp.Water could be taken from a scoop in front of the prop/props  around the unit and  out of the hull . This is not rocket science  one electronic manufacture already  fits these pipes allowing units to be water cooled. :-\ :-\
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Colin Bishop

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Re: Sound units, your thoughts
« Reply #9 on: December 27, 2007, 10:22:58 PM »

I confess that I'm pretty ignorant when it comes to electronics but generating heat on the scale being talked about here suggests that there is a significant degree of inefficiency in the system. We don't have to watercool our home cinema systems do we? (not that I've got one!)
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Martin [Admin]

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Re: Sound units, your thoughts
« Reply #10 on: December 27, 2007, 10:48:34 PM »


How about a setup where there is fixed small heatsink where we can bolt on a range of options large metal plate, multi-finned compact heatsink, water cooling, fans.... anything we wanted, recommend or supplied as an option.
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cos918

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Re: Sound units, your thoughts
« Reply #11 on: December 27, 2007, 11:17:03 PM »

if you had a fan would this run off the drive bat? as modlers use diffrent voltage to drive boats.
Personly the only down side i see to a fan or pump is current draw. Heres a possible scene the unit is cooled by a fan or pump. Shortly after your boat put to sea say for an hour the cooling fails .Say batter low etc how long before the unit will be cooked.
So on that thought i think a heat sink might have an advantage, will this work in a small space of say a small packed hull.
john
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Bunkerbarge

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Re: Sound units, your thoughts
« Reply #12 on: December 27, 2007, 11:55:30 PM »

Colin has a fair point there.  Instead of looking into ways of dissipating the heat it would be a lot more productive to be looking into ways of not creating it in the first place.  Not only is the heat itself undesirable but it is an obvious waste of battery power.

The question then has to be what creates the heat and how can it be reduced?  How can the electronics be redesigned to reduce this heat generation?  That would be a major step forward.

As for using a smoke generator to cool the sound unit, if you heated the cold water vapour you would evaporate the moisture droplets and reduce the effects of the smoke.  It may however be usefull to pre-heat the water in the reservoir to make evaporation easier.
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malcolmfrary

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Re: Sound units, your thoughts
« Reply #13 on: December 28, 2007, 12:07:16 PM »

The poblem is that we are using what is basically an analog amp designed for HiFi use.  Heat production is not usually an issue, but the instructions usually advise not blocking the airvents, and power used is rarely a problem as they are usually mains powered.  We have an enclosed box with a batery for power.
Mphmph years ago a young Clive Sinclair marketed a PWM amplifier that was "95%" efficient.  It ran on 12 volts and shoved 10 watts into a 16 ohm load.  Bass performance was terrific - distortion at higher frequencies (it only sampled at 40K) was not good, so other products that produced nicer sounds won out.  It was physically large by todays standards, but it pre-dated chips and was stuck with early 1960s transistors.
It should be well within the bounds of possibility for one of the PIC wizzerds out there to program a PIC to be a PWM amplifier - all that is needed for the output then becomes four nice big transistors which just switch on and off, with much reduced heat production.
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Subculture

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Re: Sound units, your thoughts
« Reply #14 on: December 28, 2007, 01:26:02 PM »

If you're developing new design, why not take a look at class D amplifier chips-

http://www.analog.com/en/subCat/0,2879,759%255F1075%255F0%255F%255F0%255F,00.html

Upto 25 watts, no heatsink required.

Andy

malcolmfrary

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Re: Sound units, your thoughts
« Reply #15 on: December 28, 2007, 04:21:09 PM »

They look like really handy devices. O0  You just need a job for the other channel if you cant parallel them up....... :-\
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wombat

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Re: Sound units, your thoughts
« Reply #16 on: December 28, 2007, 04:45:02 PM »

If you're developing new design, why not take a look at class D amplifier chips-

http://www.analog.com/en/subCat/0,2879,759%255F1075%255F0%255F%255F0%255F,00.html

Upto 25 watts, no heatsink required.

Andy

Scanning the data sheet, not sure I agree - looking at the integrated 25W unit, you can be dissipating up to 6 watts in the device - it will get quite sweaty without heatsinking. Saying that, class D has to be the way to go for small, high-effciency amplifiers. Remember to leave space for the output filter too  - that can be as big as the actual amplifier!

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Subculture

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Re: Sound units, your thoughts
« Reply #17 on: December 28, 2007, 06:03:52 PM »

But wouldn't that be at maximum duty?

I think it's unlikely the amp is going to be used like that.

Andy

malcolmfrary

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Re: Sound units, your thoughts
« Reply #18 on: December 28, 2007, 06:16:09 PM »

If it is going to handle large engine sounds, a healthy continuous rating will be needed.  Intermittent sounds like ships horns, less so.
Not too sure about just how needed the filters would be for boat use.  In the old Sinclair design, a lot of reliance was placed on the mass of the speaker to sort out high frequencies - the only time that the use of filters was mentioned was where a tweeter was being used, and we are not really into that kind of thing.
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red181

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Re: Sound units, your thoughts
« Reply #19 on: December 28, 2007, 06:41:30 PM »

I have heard of some people using cheapo mp3 players. Can the sound not be reproduced somehow one one of these, then the speaker plug in options are huge, depending on the size of the boat, and mp3's dont get hot, and are small. AS posted previously, surely some pc boffin out there can come up with a remedy
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wombat

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Re: Sound units, your thoughts
« Reply #20 on: December 28, 2007, 10:24:05 PM »

But wouldn't that be at maximum duty?

I think it's unlikely the amp is going to be used like that.

Andy

Hi Andy,

Looking in a bit more detail, if it were me, I would be heatsinking - without even on moderate power the junction temperature will be running fairly close to the wind - all up thermal resistance of the case is about 22C/W. The package would be a bit of a swine for amateurs and small manufacturers to deal with (unless they have access to a decent SMT line).

Malcolm,

I think that the output filter would be essential with one of these integrated jobbies - otherwise the inductive spikes caused by the speaker could play havoc with the output transistors. I think also you could find that any high frequency sound could be screwed.

Wom
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malcolmfrary

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Re: Sound units, your thoughts
« Reply #21 on: December 29, 2007, 10:57:08 AM »

PMDEVLIN  -  For low power the MP3 players are great, but for all but the faintest sounds you need an extra amplifier to get the sound level required.  MP3 players are usually intended to drive headphones rather than loudspeakers.  There are some out there who want the same sound level as with the full size, and that needs pure brute thrutch.

Wom  -  I was just referring to the '60's technology.   Agreed the output transistors would benefit from being protected, but the capacitors shown would have the effect of smoothing off the high frequency edges presented to the speaker.  The speaker used in a boat would probably be a single unit with plenty of mass, and so any signal presented above about 3.3K would be attenuated.  In any case, the chip used to hold the sound sample would be one developed for voice recording, and so the output would stop there.  Real HiFi demands a response up to over 20K, far beyond most human hearing, and these chips were probably developed with this market in mind.  No values are given for either capacitors or inductors, but I suspect that they are small and aimed more at calming down the spurious responses to the amplifier's PWM switching when the speaker can respond to them.  I reckon that with a single knobbly speaker, no-one would notice unless the speaker leads were long enough to radiate RF.
The big trouble is that the price was quoted in batches of 1000+. 
In a boat, which is intrinsically a sealed box, any cooling will need forced flow, be it water or air.  For air, a computer fan, should do the job.  Even with a life of 4000  hours, thats 6 months running 24/7.  At a couple of hours a week, its a long long time, and if its made accessible for replacement.....
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Circlip

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Re: Sound units, your thoughts
« Reply #22 on: December 29, 2007, 11:24:27 AM »

Come on guys, it's a b****y toy boat. you will NEVER get a true engine sound out of a three/four inch (OK 75/100mm) diameter speaker. Todays Youfs fall into the trap that loud is good and don't understand the QUALITY of sound. I suspect malcolm may have had some involvement with Hi-Fi so understands the principles. If you want the base response required to give a TRUE representation of modern diesels etc, you are going to need a speaker of AT LEAST 7"dia and the bigger the better. Yes I know manufacturers like BOSE have mini speakers but ALL of them use SUB-WOOFERS for the base units. Seen an electric powered DH Hornet with a HI-FI system built into it to emulate the sound of the Merlins, but it's 100" wingspan, and the amps heatsinks are aircooled, 2 X 40W amplifiers, gosh!
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Re: Sound units, your thoughts
« Reply #23 on: January 04, 2008, 09:13:03 AM »

Hi All

Now I may be missing something here, but during the 70's I used to take one of those hand held transistor radios that used 9volt batteries to bed and listen to the top 40 before going to sleep. Many times I would wake up in the morning and the radio would still be going. My point is that the radio after 8 or so hours of use was never warm. Surely technology has not gone backwards. I also have one of those (what used to be called "Ghetto Blasters") that runs on batteries it never gets hot and is so loud that it rocks the china in the cupboard. These Ghetto Blasters also have motors in them to run Tape and CDs so power consumption is not a problem. I can not see any problem in utilising this type of Amp in a sound module. And before you mention about the bottom end why not use a low frequency speaker or even a full range one as most of these systems have.

Seams simple really

Regards David
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Shipmate60

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Re: Sound units, your thoughts
« Reply #24 on: January 04, 2008, 09:52:35 AM »

Haven't we lost sight of the forest for the trees here.
The sounds from a ship isn't the sound of the engines, if it was the crew would all be deaf!!
You hear the sound from the exhaust!!
The engine room is sound insulated, the only way to hear the actual sound of the engines is to stand beside them.
Can you hear a Steam Recip, NO. You hear the feed pump clanking. In a Steam Recip engine room you can talk without hardly raising your voice, so how does that translate to the external sound emitted from the ship. It doesn't.
The main sound from a ships exhaust is from the generators not the main engine(s) as they are smaller engines with a higher frequency.

Bob
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