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Not that it makes a difference but it's for a boat with 4 speakers, two at the back and 2 at the front.
I have an existing old 4 channel amp which is big and heavy and playing up and sucks power. I'd like to change it for a little class D amp off ebay (nobsounds probs).
Simple question..... can I connect two (4 ohm) speakers to each channel or is it going to go bang? If so...... is there a special way to do this?
Are you sure your old amp isn't a 100V system rather than a standard hifi amp?
Edit: actually that doesn't matter if you are changing both speakers and amps, sorry
To answer your question, can your little class d amp drive a 2ohm load as that is what you will be doing if you connect two speakers in parallel to a channel
Wire them in parallel, be fine
Existing amp is a an old, inefficient car amp.
I think the nobsound amps handle 4-8ohm.
yes, just wire in series, you'll present an 8 ohm load with 2 4 ohm speakers. The amp will be 100% fine seeing 8 ohm.
If you wire in parallel, you'll give it a 2 ohm load which will stress it much more.
Higher ohms good, lower ohms bad.
Wiring them in parallel drops the resistance, giving more power to the speakers. so get speakers rated at a similar power to the amp. E.g. amp output 2x 100w @ 4ohm needs 4 speakers rated 100w (4ohm).
or, in series, + from amp to - on spk1 then from+ spk1 to - spk2 from + spk2 back to - amp
Depends on what the specs of the amps? Max power into how many ohms? and what is the minimum ohm rating for the amp?
If the speakers are identical and 4 ohm, wiring in parallel is going to give an impedance of 2 ohm. Wiring in series is going to give impedance of 8 ohm.
Halving the impedance will double your amp's output power, because its putting out twice the current but the amp's power supply needs to be big enough to supply this current load otherwise you'll get distortion and clipping which can create current spikes and damage the voice coils on the speakers.
If you are using an amp rated at 30W into 8 ohm (and can be driven as low as 2 ohm) and a inexpensive class D amp with a power supply with a low max current rating then you could end up stressing the amps and speakers out and get poor audio quality and burn out the components quicker. Think of it as revving the crap out of a little 1 litre engine hatch back, eventually the poor engine is going to give up as its constantly being used at max capacity.
If you are using an amp rated at 100w in to 4 ohms (and can be driven as low as 2 ohm) this is going to be stressed less as you are running closer to the operating window the amp was designed for. Just be careful and don't crank the volume knob too high.
Doubling the impedance will halve your amp's output power. While this might seem the safe option as you are halving the power you are also reducing how loud the speakers will sound. So you may end up turning the volume dial higher and then running the amp close to its max capacity again to get an acceptable amount of volume from the speakers.
I've a nobsound in my MG.
First up you need a power supply as they don't have any way to boost the incoming voltage. If you run it off 12V it's really quiet as power = voltage squared over resistance. So you'll need a 12V to 24V power supply (or a mains to 24V if it's for a shed).
Secondly, you're better daisy chaining speakers than running in series/parallel. This means you run 1/4/9/16 speakers in a grid so the overall impedance is the same as a single speaker. So if you want to run 4 speakers, look for an amp that can firstly convert stereo to mono, then drive all 4 speakers off one bridged channel.
Thirdly, the nobsound is about as good as it's £12 price tag. If the sytem works as it is, just get a car head unit off marketplace, I sold my nice alpine one when I scrapped my car thinking I'd get some of my money back from it. and made about £20 and had to deliver it the other side of town, the adaptor looms cost more than £20! The only reason I put the nobsound in the car was I could hide it behind a chrome trim plate in the original car interior and not have anything other than the dial showing.