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Old 26th February 2013, 01:59 PM   #1
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Default Amateur Looking for Advice

Hi All,

Apologies if this is the wrong forum, but i'm looking for some super basic advice at a beginners level.

I know it seems to be the done thing at this stage but i'm trying to make a basic boombox for my small apartment.. I'm not after high quality sound or making sure the enclosure is the perfect environment - that will all come later

For now I just want to try to figure out the basics or how everything fits together. Don't feel you have to hold my hand, just a friendly point in the right directly would be a big help as i'm not sure where I should even start to look at the moment.

Basically I have a Lepai Tripath TA-2020A+ Amp (I will have) and off that I'd like to run 2 or 4 speakers and if possible a bluetooth receiver.

Questions

ohms and series/parallel

I'm trying to learn the basics, so for example if I wanted to attach 2 x speakers to a single channel on the amp am I best to connect these in Parallel? What's the difference as far as sound quality, or is that irrelevant?

The amp has a Speaker impedance of 4 - 8ohm. Does that mean the I would need to connect two speakers in parallel at 8ohm each to reach the amps minimum 4 ohm impedance? ie connecting 2 x 4 ohm speakers in parallel would give me atotal of 2 ohm which is below the amps specs - what issue does this cause (Is it under/over powered?)

Secondly is it even worth doing two speakers, or just one full range speaker on each channel?

Power

I don't even know where to start.. how do I work out my power requirements and is this solely down to the amperage required?

The Amplifier states it's "Input power : DC10~14.4V≧3A" and I read some people say to replace the power supply with one that has a higher amperage.

If I have a bluetooth receiver, Amplifier and 2 or 4 speakers.. how do I work out my requirements - also out of curiosity if I only needed say 3A but the power supply is 6A does this cause issues?

Lastly as a general power question, If I wanted to connect the bluetooth receiver to the power and it currently uses 5V DC USB connection, how would I go about this? am I likely to blow it up, or does it need some sort of power adapter? ie power supply says its 14.4V - how does that (Voltage) affect each component?

Thanks for your time and advice I really really appreciate it. I know this sort of stuff might not be nice for you, but it's just a way to start learning the basics and build up from there.

Thanks again
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Old 26th February 2013, 02:29 PM   #2
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Sorry one more question.. I noticed in another post that in addition to matching the impedance, the power of the drivers should match up with the power of the amp.

Question is what is applicable on the amp? Is it the maximum power rating (in my case 180W) or is it the RMS (20W)

That also brings me back to my other question of multiple drivers - how is the power requirements calculated and is it different for series and parallel connections.

Thanks again
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Old 26th February 2013, 03:51 PM   #3
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Quote:
Originally Posted by misterhill View Post
I'm trying to learn the basics, so for example if I wanted to attach 2 x speakers to a single channel on the amp am I best to connect these in Parallel? What's the difference as far as sound quality, or is that irrelevant?
You'd want to connect two 4Ω in series (=8Ω) or two 8Ω in parallel (=4Ω). I'm doubtful there would be significant difference in quality either way.
Connecting a 2Ω speaker load should be avoided. It increases the current and is likely to smoke components.
Quote:
Secondly is it even worth doing two speakers, or just one full range speaker on each channel?
One full range speaker is probably better, but a lot would depend on the speakers used.
Quote:
I don't even know where to start.. how do I work out my power requirements and is this solely down to the amperage required?
An included supply will probably be a 12V, 2A wall wart switching supply. It will work, but could be better. I power my Lepai with a 13.2V, 3A linear regulated supply and it works well.
Quote:
If I have a bluetooth receiver, Amplifier and 2 or 4 speakers.. how do I work out my requirements - also out of curiosity if I only needed say 3A but the power supply is 6A does this cause issues?
No issues; the amp will only take the current it needs.
I would probably use a separate supply for the Bluetooth; regulated 5VDC supplies for phone chargers and USB hubs are cheap and available.
Quote:
That also brings me back to my other question of multiple driver
Matching the amp power to the speaker power isn't important here. But to answer your question, when two speakers with the same impedance are connected in series, each sees half the voltage. In parallel each sees half the current. So the power rating becomes double that of a single speaker. Examples: 1) two 80W speakers = 160W; 2) a 50W and a 10W speaker = 20W (double the lower individual power rating)
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Old 26th February 2013, 03:56 PM   #4
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Wow! Thanks sofaspud, I really appreciate your time and advice. All makes complete sense.

I was hoping to avoid using two separate power supplies, but as you say it's probably the easiest.

Thanks again
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Old 27th February 2013, 05:45 PM   #5
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One more quick question... the amplifier has two outputs (Channels?) - Theoretically can you run a Sub off one and something else off the other.. and running the sub on it's own output still require a crossover, or does that come done to the capabilities of the Amp?

Also, what do people recommend for something this basic, would I just run a full rang speaker, or would a run two separate speakers in serial/parallel to cover a wider range (Is that even worth it?)

Thanks again and sorry of this is pretty basic knowledge - but I really do appreciate your advice
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Old 27th February 2013, 06:02 PM   #6
Mooly is offline Mooly  United Kingdom
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Most subs have their own internal amplifier that accepts as an input, the signal from the main left and right channels of the main amp. The amplifier in a sub has a filter on its input to allow only the low frequencies through.

Personally I think you are best aiming for good quality stereo first.

If you can build (or find a kit) then its easy to make a 14 volt to 5 volt adapter yourself. A couple of pounds for the parts (really just one three legged regulator and a couple of capacitors) is all you need.
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Old 28th February 2013, 09:45 AM   #7
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Thanks Mooly

Appreciate your time and advice
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