car stereo power requirement - data point

[walt]

I recently added some front bookshelf speakers to the car stereo system in the boat (stereo is about $150 Pioneer model with external and Ipod inputs) so now there are four bookshelf speakers. I have a linklite battery monitor so can see how much current is being used. The current will vary all over the place as music is playing so you have to interpret a little but if I'm inside the cabin playing the music moderately loud, I'm probably using on average 1.5 amps. With the companion way open, this is loud enough to easily hear in the cockpit while sailing and even annoy other boaters who like things more on the quiet side. At very loud - starting to go into distortion (and too loud to listen to for long), the current might be between 2 and 3 amps. I have an Ipod on this and a classical song came up and between quiet and loud passages, the current varied from .7 amps to 2 amp. I would say an average current for my overall use might be about 1.5 amps, maybe a little less. Not really all that bad.

One sort of interesting thing.. I just mounted the new front speakers (Polk Audio). I auditioned these in the store and mounted one in the head area and the second up in the V berth area. In the second picture, you can see a wood shelf on the port side V berth area which is not used. All the bare plastic causes some odd acoustics and with this speaker up there, it sounded like I had an echo and also a resonance in the 1K to 5K range. So I moved this speaker to the spot under the forward port settee (had to cut a hole). One of the nice things about book shelf speakers is that you can easily move them around to see if you like the placement. I even had to rotate this speaker so that its pointing "up" before I wasn't getting the resonance. I'm happy with it now, the system has a nicely filled in and even spectrum.

 

[walt]

Woops, I meant to post this over the Macgregor area.. Oh well. The power "data point" might still be interesting here.

 

[Maine Sail]

I used

Good data, and in-line with some bench experiments I've done..

I used a full spectrum white noise CD, an spl meter, and a DVM measuring amps. By doing this with a white noise CD I could see steady output. Music varies and will likely be less draw unless bass heavy rap.

On 8 Ohm KEF's at 94 db it drew 2.12 amps.

At 101 db (which is quite loud) it drew 4.58 amps.

Using more efficient 4 Ohm speakers I was able to play louder and at less current draw so the speaker choice can have some added benefit for system efficiency..

 

[walt]

Not a problem most people here have but the old Mac 26S is more like a stretched out 22 foot boat - and has lots of "audio reflecting" gel coat on the inside. When I put the one front speaker up in the Vberth area, it really made the whole system sound almost bad - weird echo and nasty very noticable resonance in the mid range from the Vberth area. Being able to move this speaker around made a huge difference. If I would have used 4 ohm car stereo speakers, I would have had to cut some nice big holes to find out I didnt like the placement. So for at least my application in the smaller boat, the bookshelf speakers have been a good idea. For a given DC voltage, you can get 3 db more power with 4 ohm vs 8 ohm but Im getting all the audio level I can handle at what I consider very reasonable current draw. I didnt check the spl level on any of the speakers I bought but think they are at least average or better efficiency. I think my distortion is more limited by FM broadcasts and MP3 compression than by the speaker/power amp at the levels I use the stereo at.