Building the boat hifi. Help needed

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Oscarpop

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Why go for tiny ceiling speakers? Where's the bass going to come from? Why not just get some sensibly-sized car speakers?
 
Normal domestic hi fi speakers are rated at 8 Ohms and car hi fi units at 4 Ohms, but these are very nominal figures.
I had some great domestic hi fi speakers that were close to 1 Ohm over much of their range.

Higher impedance speakers will never cause any damage so 6 ohm speakers are fine to use in a car system. They may be slightly less loud but the difference will be small.

It's hard to tell from technical specifications, but the speakers you listed will be OK, but the sound quality is compromised by the size etc.
 
Oscarpop said:
possibly you're right.


I just need someone to explain the ohms thing to me.

Please
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I thought you might respond with a robust reasoning behind your choice of those expensive little speakers. I'm disappointed. But equally perplexed as to why you've chosen them in the first place.

I've got a couple of 8" (?) Pioneer speakers fitted under the seats in the saloon, good sound, rich bass.
 
Ok, well I am limited by the space I have behind the roof headlining.

I also don't like the aesthetics of many of the car speakers .

So I wanted a high quality ( if not bassy) small low depth speaker from a reputable manufacturer.

Hope this helps :)
 
We have a television on board with inbuilt speakers (probably) larger than you're favouring and the sound quality is totally carp.

A 2 inch speaker on its own will be good for frequencies over 1kHz or 2 kHz - maybe a little better than a mobile phone, but not much :(
 
If you don't like the look of ordinary speakers, how about something like the Bose Acoustimass 3-speaker system? Just have to find somewhere to hide the subwoofer.
 
As or more important than the 6Ohms is that their sensitivity is way down (82dB/W) so you may find they don't sound very loud. Also the frequency response only goes down to 120Hz at best - and that is simply not enough for anything - you would need a sub woofer as well and that makes things more complicated.
 
Oscarpop,

To answer the OP in the absence of any other explanation of "ohms".......

Put crudely the value of speaker ohms is a measure of the load on the amplifier. The higher the value the bigger the load and therefore the lower the current that load (speaker) will draw from the amp.

It is best to match the amplifier to the speaker because then the amplifier can cope with the current the speaker is drawing. If a speaker with a lower value of ohms is chosen then the amplifier may not like the extra current being taken and overheat causing failure. If a higher value of ohms is chosen then although the amplifier will cope with the resultant lower current the volume of sound out of the speaker will be lower.

The specification of the amplifier usually states the ideal loading value (ohms) for optimal performance. There is usually some tolerence in that figure but try to get as close to ideal as you can.

So if the amplifier output is for example 50 watts into 4 ohms (per stereo channel) then choose 4 ohm speakers. If you fit 8 ohm speakers the volume will be noticeably less but shouldn't damage the amp. If you fit 2 ohm speakers you chance blowing up the amplifier or significantly reducing it's life.

I hope this helps.
 
Impedance

Just to add to the above explanation. The correct name is Characteristic Impedance. It is described as ohms but does not relate very much to DC ohms as measured by a multimeter. It is a bit more related to the relationship of AC volts to AC current but even then the impedance (the AC equivalent of resistance) varies with the frequency.
A transmission of power from a source to a user can be at high pressure (voltage) low flow (current) or low pressure (voltage) high flow (current). High impedance or low impedance circuit or transmission. To get max power transfer we need to design the source and the load to be best for the same impedance. This ratio of voltage to current is easiest described as ohms.
As for speakers Yes the sensitivity is important. It is described in decibels. A difference of 6 decibels in sensitivity means you need twice the amp power to make the same noise. So a good (large) sensitive speaker can do a good job with a very low power amp. Small speakers for car stereo tend to be low sensitivity so they will cope with large powers and a wider range of frequencies. Big is best....
olewill
 
6 dB is 4 times the power, or twice the voltage.

If they are roof mounted speakers, presumably they're normally mounted in a significant void. What happens when they're put in a small enclosed void?
 
As for Hi Fi on a boat let alone with a car stereo you are kidding yourself:D get a simple pair of car speakers mount in bookshelf cupboards (enclosures) and be done with it, it's as good as you will get.
 
A boat is not a good hifi listening environment, because the speaker positioning and where you can sit to listen to them is very compromised by the boat having to be a boat first. Forget any idea of hifi on a boat, you just want a pleasant sound. With this in mind, I'd forget panel-mounted speakers, as these are usually based on car designs where the door voids act as the speaker enclosures - a vital part of the effectiveness of the speakers. Ideally the enclosures should be as large as possible and completely sealed. As this is next to impossible on a boat, I've ended up with small bookshelf speakers on mine (JBL Control One). I also discovered that the little JBL Duet II computer speakers sound surprisingly good, are self-contained, plug into anything with a headphone socket, and can be powered from 12v. They're also cheap (£30). You could probably epoxy brackets to them and screw them upside down on the ceiling.
 
It's not practical to achieve good sound quality on a boat. Most people want just background music and the practicalities of small speakers etc are more important than the sound quality.
It is however possible to install a boat system that is much better than average and for me passes the test that I can listen to the music and enjoy it.
The main limitation on most boat systems is the speakers and if you are prepared to pay a bit more money and put up with something a little more obtrusive you can achieve something with acceptable sound quality.
 
You need speakers with good sensitivity (higher db for 1 watt). The true maximum wattage (that is rms across the full frequency range into 8 ohms) from a car radio is about 6.3 watts. You only have 12v supply remember. Ignore any peak power or music power ratings. You really need to listen to speakers before purchasing. A high sensitivity speaker can be harsh with too loud midrange.
 
st599 said:
6 dB is 4 times the power, or twice the voltage.

If they are roof mounted speakers, presumably they're normally mounted in a significant void. What happens when they're put in a small enclosed void?
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Thanks for that I still get confused about 3db versus 6db and power but at least now I can claim old age as an excuse. The point is sensitivity makes a huge difference. I have a tiny little radio I sometimes use when I am working. Runs on 2 AA cells. It really is horrible on its little built in speaker. However If I connect it to a large speaker (12inch) in an enclosure the difference is so dramatic. More than loud enough and sounds brilliant. Still with the same 50 milliwatts or so of audio power. olewill
 
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