Stereo power usage

[arf145]

Doing a power budget and I see the usage spec for my Clarion CD/head unit says "< 15 A" Yikes. Just how much power does a typical stereo use when driving speakers at a easy going rate? I realize there are a lot of variables, but just trying to get an idea.

Thanks.

Tom

[CapnBilll]

Don't know, but when I was a teen I found out the hard way it will drain a car battery in an afternoon.

[PopeyeGordon]

The 15 amp number would represent wiring capacity for maximum possible peak current - Full volume, deepest bass notes. You could measure your approximate current draw by putting power lead in-line with an amp meter.

Rather than the usual stereo setup I went with an XM pocket tuner and a 25 watt per channel marine amp from Overtons marine. That model may not still be available from them but you could Google for sources. My simple 2 channel amp was a small package with aluminum ribbed case, volume knob on a 3 foot cable and a few input/output connections. It is miserly with power but you should turn off the amp at the fuse panel to avoid standby current draw. When I installed my first 22 watt solar panel on the boat I experimented by running the stereo and XM directly off that panel. It ran 2 speakers at full volume so aparently the setup draws less than 1.5 amps. This was good news, I ran my stereo all I wanted and had no worries about power. Went to sleep at night with relaxing jazz, using the tuner's 90 minute timer.

Since the setup used modest 4 inch woofers I added on a 12 volt powered subwoofer, also miserly with power draw. It was a woofer from a computer speaker set that came with 12 volt wall wart. This allowed me to micro-manage power use by turning on the woofer only when I was sure there was enough solar in the budget. Plenty of 12 volt powered woofers to choose from, with various power ratings. You choose the biggest you can handle but in my experience you will benefit from being able to switch off a separate woofer amp when you want to stretch battery power.

[LandLocked66c]

I'll will be buying this.

http://www.amazon.com/Pyle-PLMRMP3A-.../dp/B003K154IE

[scraph]

Instead of guessing ... or using spec sheets ... I'd recommend actually measuring it. I recently measured the current requirements of every individual DC load on my boat using a multimeter. Gain access to the back side of your DC breaker panel, remove the supply cable coming from the battery, and wire your multimeter (ammeter connections) in series with it temporarily. Energize all the loads of interest only one at a time and record the ammeter reading for each (one at a time is necessary to prevent overloading the ammeter). I recommend allowing lights to warm-up to allow their current draw to stabilize and ensuring pumps (ie bilge, shower sump, freshwater) are primed.

The current draw from my stereo (Fusion MS-IP600) is 0.453 amps at standby (0% volume) and 0.522 amps at 50% volume. The stereo is driving a pair of Standard AS101 speakers (5" 100 watt peak 2-way speakers). 50% volume is a more than acceptable listening level on my stereo.

[noelex77]

Originally Posted by arf145

Doing a power budget and I see the usage spec for my Clarion CD/head unit says "< 15 A" Yikes. Just how much power does a typical stereo use when driving speakers at a easy going rate? I realize there are a lot of variables, but just trying to get an idea.

Thanks.

Tom

The units do vary a bit, but just under an amp is typical

[PopeyeGordon]

Measuring with a meter is inexact for two reasons - the bass notes and constantly varying levels with music will cause irregular spikes in the draw that are too fast for most meters to register. Also the power supply filter capacitors in the stereo make a sudden large drain on the power source when you turn on the unit. This could even blow the fuse on your meter.

Hopefully you know that you should choose a stereo with LCD display because bright fancy fluorescent displays waste a lot of power.

If your installation reveals a flickering of the display or indicator lights that is worse with high volume this is a sure sign you need a heavier gauge power wire or have a poor fuse connection. I did once see a cheap car stereo that flickered just because of insufficient internal power filtering.

[arf145]

The stereo is a couple of years old--already have it. Just assessing my power draw. I think it has an LCD display but don't remember. I'm pretty sure my multimeter won't support measuring amps of the amount expected from the unit, but I like that idea. Appreciate the numbers, scraph, but it seems a little wierd that 50% volume is only .02 more amps than 0%.

Anyone measured usage with a Victron or other battery monitor?

[scraph]

Originally Posted by PopeyeGordon

Measuring with a meter is inexact for two reasons - the bass notes and constantly varying levels with music will cause irregular spikes in the draw that are too fast for most meters to register. Also the power supply filter capacitors in the stereo make a sudden large drain on the power source when you turn on the unit. This could even blow the fuse on your meter.

Your statement here is internally conflicted to some degree. The 'irregular spikes' in the draw that you refer to are filtered and regulated to a large degree by the filter capacitors you referred to in the second portion. There is a point where your statement is true ... take an ammeter to the supply side of a stereo and you'll see it. At lower volume levels, the filter capacitors and other regulating features of the power supply are very effective at keeping the current draw of the stereo reasonably clean and steady. Turn up the volume louder and you will see a point when that is no longer true. The 'irregular spikes' are not present to much degree on the supply side of the power supplies at moderate listening levels ... if they were then we wouldn't be dealing with a very good power supply anymore.

I understand how to use a meter to measure the things it is capable of measuring and when those measurements are meaningful. The amperage draw I provided for my stereo at 0% and 50% volume were meaningful. I did not provide the values measured at 100% volume on purpose ... they were no longer meaningful.

[scraph]

Originally Posted by arf145

The stereo is a couple of years old--already have it. Just assessing my power draw. I think it has an LCD display but don't remember. I'm pretty sure my multimeter won't support measuring amps of the amount expected from the unit, but I like that idea. Appreciate the numbers, scraph, but it seems a little wierd that 50% volume is only .02 more amps than 0%.

Anyone measured usage with a Victron or other battery monitor?

It is not at all weird that 0% volume draws quite nearly as much power as 50% volume ... if you'll follow...

First, sound at the levels we comfortably listen to doesn't have very much power ... when expressed in units of watts and amps.

Take a standard speaker as example ... they have a rating known as 'sensitivity'. It is a measure of the volume of sound they will produce for 1 watt power input at a distance of 1 meter. A good average number for a home speaker is 90 dB/1W@1m. A doubling of power produces an increase of +3dB. +10dB has been determined to 'sound twice as loud'. A jackhammer at 1 meter is about 100 dB. This speaker, with only 1 watt power input, would be half as loud as a jackhammer at 1 meter. Loud enough for you? 90 dB is probably about 8 times as loud as your TV is from 3 feet away (~60dB). This speaker would produce 60dB of volume with only 0.001 watts of power. Granted, there are discussions of what frequency the sensitivity is measured at and numerous other things but this is sufficient for the point.

Second, most amplifiers we use for stereos are known as class AB amplifiers. I'm not going to get into any detailed explanation on their operation but ... as you probably know, they use transistors. Transistors are used to amplify the output signal and function like 'electrical switches'. They aren't always 'turned on' though ... and they require a certain minimum amount of power to keep them just barely turned on (known as biasing) ... so that when the signal goes from silence to sound there is no delay in the transistor turning on and beginning to amplify. It is this constant draw that accounts for a lot of the 0.222 amps at 0% volume.

The power requirements for reasonable listening levels are not very high, and those same reasonable levels don't contribute very much to the existing power draw of the stereo. It may all seem weird but science isn't always 'common sense'.