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Old 05-04-2008, 16:35   #1
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Stereo Question: Low power requirements?

Hi guys,

I'm switching all my lightbulbs and other goodies to low wattage, and I'm wondering if you guys would be so kind as to describe how you'd build an ultra-low power requirement stereo?

I'd like it to play in stereo, so it'll need two speakers. I'm thinking about mounting the speakers on the aft end of the cabin where an opening port or two right beside each would give sound both inside and out. Perhaps with a flap, like what is inside of air condition controllers to direct the sound waves out the port would be required?

What I'd really like is for it to have is a hand crank generator of some sort, maybe using a winch handle? So that for every hour of play its got to be cranked a few minutes. It'd be grand to leave the solar panel to power the VHF and nav lights, and entertainment be run off of sweat equity.

Thanks guys!
Zach
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Old 05-04-2008, 17:17   #2
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Hi Zack
I run LED everything.I have found that the stereo, which is a marinised cd/radio unit. (probably a car stereo painted white !) Pulls about twice what all the lights, including nav, do when running. I do like it loud at times, and I can see the amps gauge go up a little when this happens. Regardless I manage to keep the whole lot running with a single 20 watt solar panel. I leave the 27 meg off most of the time, and only turn the vhf on when I am sailing. As an aside ,I have a stock of rechargeable aa batteries. When the boat batteries are full I start charging these. They run my gps,scanner,small torches and a host of other things. The question I get asked is why dont you put in another big battery ? The problem is that I would end up with a bank that never fully can up to charge. Using the little batteries soaks up the last "drop" quite nicely. On my new boat I will try and dramatically increase the amount of solar charge. (Radar pulls 55 watts alone and thats a very little one)

cheers
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Old 05-04-2008, 18:06   #3
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Cooper sounds just like me. All LED light now and very happy but the stereo is the big sucker. Probably more so then Zachs as I have 4 large speakers which do get a work out often

I've been sussing and are swapping to a stereo that has a MP3 input plug and one of the ipod things. I'm told the motor driving the actual CD is what's using lots of amps and the ipods use bugger all. Probably good for Cooper with his rechargeable battery set-up. Not sure how much I'll save but I'm told it will be noticeable by a knowledgeable stereo mate but then he does know how much I use mine.

All I have to do then is get a LED masthead light and I'm good to go. They need to change some race rules first though, they specify 25W but no 'equivalent' is mentioned.
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Old 05-04-2008, 18:10   #4
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How about this??

The power consumed by a stereo is mostly proportional to the "loudness" coming out the speakers. So the louder you want it, the more Battery power used. Low frequencies take the most power, so thumping bass is soaking up your battery power quickly. To be able to hand crank something to produce music, it would be more like, crank for an hr to listen to a few minutes of Audio. There are small hand crank charged Transistor radios available. Personly, I think you would be best to use something like an Ipod and in ear phones. Batteries last awhile and you get good sound.
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Old 05-04-2008, 18:33   #5
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That's right, you know stuff about this stuff don't you Mr Wheels.

Ok then something I've been wondering, if I have 200W speakers, say, am I using twice to power than if I had 100W?

And if I have 4 speakers when I turn 2 off (fader thingy right down one way sort of thing) again am I save lots or not much?

Just trying to get a grip on what power is used to drive the speakers themselves compared with the head unit usage.
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Old 05-04-2008, 18:36   #6
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Alan, I've actually got one of those I need to sell. Would probably cause the boat to list, without counting the accompanying collection of black vinyl stamped disks. If I could only buy a bag of light weight black holes that play music...


Thanks for the input guys, I'm trying to shave off all the power use so I can get by with less panels. Keep waiting for this new technology thats supposed to slingshot solar to half the price per watt and double the power. Been "next year" for the last seven or eight years!

So if the low frequency takes the most power, would it be safe to assume that a few small midrange speakers would do better than a set of 6x9's and accompanying tweeters? I've spent enough time working factories and running loud equipment that I have a real hard time telling between FM and CD on even the best units.

Cooper, you sparked an idea.
Pondering those rechargeable individual batteries, and a boom box that runs off a bunch of C's. I've seen mini-solar panels that are only meant for recharging batteries, designed for strapping onto backpackers. (Now I'll need to find a few backpackers to stand on deck and follow the sun...) Wouldn't be the end of the world to always have a set charging, though it would require some creative wiring to relocate the speakers.

Great questions Gmac, I too would like to know the answer.
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Old 05-04-2008, 19:58   #7
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Quote:
Originally Posted by Alan Wheeler View Post
How about this??
Does it come with an mp3 input?
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Old 05-04-2008, 20:17   #8
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I doubt it even comes with a power input

Actually sussing, it doesn't. Who's feeling a tad silly about now?
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Old 05-04-2008, 21:45   #9
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Arm power!
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Old 06-04-2008, 01:09   #10
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Sure you are wanting to ask me these questions ??:-)

Quote:
if I have 200W speakers, say, am I using twice to power than if I had 100W?
No. The power rating is actually a complete red hearing. In fact, in Car Audio, it is mostly snake oil. They don't use "real power". The figure you want needs to be RMS. That tells you the real power, as in heat, going into the Voice coil. The rating most of these speakers have is peak to peak or peak music power. Both tell you nothing apart from the maximum short term(measured in Miliseconds)duration the Voice coil can handle before it is damaged. And even then, a frequency has to be specified. But all that aside, a 100W speaker may not go any louder than a 10W speaker. In fact there are speakers made that a 10W version can go considerably louder, as in hundreds of times. A bull horn for instance.
So the figure that you need and very few ever give is this. xdB SPL/1W/1m. That is the number of decibels the speaker will reproduce when fedd 1W of sound power and measured from a distance of 1metre. And if the manufacturer is realy realy good, he will tell you what frequency or spectrum of frequency he used for the test. Because that all makes a difference too. A speaker is going to handle more power with less spectrum. So before I go right off the rails here, a speaker that can have an SPL/1W/1m of say 87dB will be half as loud as one that has a rating of 90dB. Half or twice as loud is plus or minus 6dB of amplifier power required. So you would have to have four times the size of amplifier to produce twice the sound power. It is even more complex than this, but I can see eyes rolling now.

Quote:
And if I have 4 speakers when I turn 2 off (fader thingy right down one way sort of thing) again am I save lots or not much?
Yes you are saving power.

Quote:
would it be safe to assume that a few small midrange speakers would do better than a set of 6x9's and accompanying tweeters?
Unfortunatly no. Just because the speaker does not reproduce the sound, does not mean the sound is not being sent to the speaker.
But in saying that, all sound equipment is limited from 20Hz to 20Khz. Above and below these ranges, equipment can do some mighty nasty things. Only realy realy expensive gear can go beyond those points. And seeing as CD is not recorded beyond those points, there is not a lot of point owning the gear that can. FM radio is only transmited to 16Khz. We can't hear above that, so no piont in wasting energy on sounds that only dogs and bats will hear. Below 20Hz is another thing we can't hear and low freq takes huge power. So no point trying to reproduce it. But if your speaker will only reproduce 50Hz-10Khz for instance, then chances are the speaker will be trying to reproduce the ranges beyond that, but you simply can not hear it and the result is the Voice coil heating up.
Distortion by the way, (the noise when you turn it up too loud) is the equivilant of feeding 10x the power to the speaker. A 10W amplifier distorting hard enough can blow a 100W speaker.
Hope that helped.
Now think realy hard before posting anymore questions...do you realy want me to answer? ;-)
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Old 06-04-2008, 01:14   #11
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I have just bought a $50 mp3 player on trademe. Runs on 1 aaa battery and the sound is amazing.
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Old 06-04-2008, 03:01   #12
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Had to read it twice and slowly but I think I have it, thanks Wheels.

So with all my excitement diving deep into things electrical, figuring out my Watts from my Amps from my ABC's and STD's, I now run into Watts that don't do err.... Watts. No wonder just about every time I go near an electrical point I electrocute myself, traps everywhere.

So the chances I have low power use speakers that go load are slim, I'm assuming the Fusion gear is average at best (got a hell deal though).
Just sussing and Fusion has 'Efficiency (1W/1M): 90dB' as Sony has 90 for theirs as well. Is that good?

Seeing you're on a roll how about these 2 then;
1, What does an average car CD use in the way of power? It's damn hard to find numbers. Does that 52 x 4 output Power tell you anything?
2, Anywhere you know someone doing 5Watt 100dB marine speakers and as I race, at 10 grams each as well
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Old 06-04-2008, 05:14   #13
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[quote=Zach;149891]
So if the low frequency takes the most power, would it be safe to assume that a few small midrange speakers would do better than a set of 6x9's and accompanying tweeters?[quote]


You just need to change your taste in music:


Alvin & the Chipmunks MP3 Downloads - Alvin & the Chipmunks Music Downloads - Alvin & the Chipmunks Music Videos - Alvin & the Chipmunks Pictures - MP3.com

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Old 06-04-2008, 05:59   #14
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Hehe, what a great thread.
Obviously Alan is the man to ask here. To make things more simple i think saying that for power versus money versus quality versus not too complicated you should get speakers with high dB rating because they are more 'easy' on the consumption and thus better. 6"9 is in my opinion a little 'hard' on the consumption so i like the round ones around 5".
The stereo should be the one you have or a cheap one. If this gets to complicated you will lose on the budget and end up more expensive than a new solar panel, hehe.
Good luck
kjell
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Old 06-04-2008, 09:08   #15
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Speaker wattage aside (often misleading, as noted), there is a tremendous amount of sloppy power management in automotive electronics. They assume that the engine will be running most of the time, so can leave amplifier circuits in the active region, use power-hungry displays for maximum flash, etc. I haven't measured the stereos, but if it feels hot while just sitting there, it doesn't belong on a sailboat. Same with ham radio... it is not uncommon for mobile rigs to draw an amp on receive standby.

This is not a common spec in stereo marketing, so it's going to take some actual measurement of different brands... maybe share info in this thread?

Cheers,
Steve
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