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How loud do i have to choose

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Visti View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Visti Quote  Post ReplyReply Direct Link To This Post Topic: How loud do i have to choose
    Posted: 25 February 2019 at 4:02pm
right now i am choosing the parts for a loudspeaker i'm going to make.
So was just wondering if all the speakers need to be about same loudness, or if there is difference in the loudness.

Thanks in advice Smile.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djeddie Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 9:22pm
If you mean the difference between a woofer and a tweeter, for instance, it's not like that.

In simple terms, if a 15" woofer has a sensitivity of 100dB 1W/1M and a power rating of 500W then at maximum it will go to 127dB. A compression driver has a sensitivity of 110dB 1W/1M and a power rating of 50W then at maximum it will go to 127dB. So they'd be (kind of) matched.

Have a Google for loudspeaker sensitivity and power rating.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Visti Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 9:31pm
So it will need to have about the same loudness in dB.

And then I read somewhere that if you pair an 8 ohm speaker with a 4 ohm amp. It will be quieter. But how much.

Lastly thank you 


Edited by Visti - 25 February 2019 at 10:05pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Danielr Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 10:59pm
It will be 3db quieter as you halved the power by doubling the resistance of the load.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Visti Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 11:02pm
So you are saying it would be like giving it 400 watt?
And does 3 dB make a big difference. 

ThanksWink


Edited by Visti - 25 February 2019 at 11:09pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 11:04pm
Amps aren't rated in ohms (impedence) they are rated in watts at a given impedance.

If an amp is being advertised as 100w at 4ohms a rough rule of thumb is that at double the impedance the power output will be about half.

The impedence is the speakers very very rough resistance rating in ohms (actually resistive reactance) in its given frequency band.

Read a little more on the subject or ask more questions here... 

 
If it sounds like a gorilla is trying to escape, turn it down.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Visti Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 11:09pm
But I don’t understand you write at dubble independence t would be half watts. But the amp I’m looking at is half the independence of my speaker.

Thanks 


Edited by Visti - 25 February 2019 at 11:10pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote markie Quote  Post ReplyReply Direct Link To This Post Posted: 25 February 2019 at 11:35pm
The power of the amplifier (watts) is relative to the impedance of the speaker (ohms).

An amp which gives 100 watts into a 4 ohm speaker will give AROUND 50 watts into an 8 ohm speaker, and 25 watts into a 16 ohm speaker.

The same amp would give 200 watts into a 2 ohm load BUT (big but), the amp must be rated as being stable with a 2 ohm load. It will give around 400 watts into a 1 ohm load..... till it goes bang very loudly.

Most amps are rated as stable down to a 4 ohm load, a few amps are rated sown to 2 ohms, and VERY occasionally (and very expensively)  an amp will be rated down to 1 ohm load.

All the above examples are a rough guide only so always refer to manufacturers spec. Also all the above are per channel, so a stereo amp will give however many watts into a 4 ohm load PER CHANNEL.

Normally when in bridge mode (where the power of both sides is combined to operate one speaker. So an amp giving 100 watts per channel into 4 ohm load, will give 200 watts into 8 ohms in bridge mode.


Edited by markie - 25 February 2019 at 11:47pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 26 February 2019 at 1:02am
Originally posted by Visti Visti wrote:

But I don’t understand you write at dubble independence t would be half watts. But the amp I’m looking at is half the independence of my speaker.

Thanks 
Amps are NOT rated in ohms. They are rated in watts output.

They are called POWER amplifiers. Power is rated in watts.

Use markies rough user guide to understand better how to calculate what your amp is capable of.

If it sounds like a gorilla is trying to escape, turn it down.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Visti Quote  Post ReplyReply Direct Link To This Post Posted: 26 February 2019 at 6:55am
Thank you very much Smile.
It definitely helped.
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