Greetings all,
I'm not very experienced in DIY Audio, but man I'm loving it!
I'm currently working on a design of a small lecture room, media will be displayed via laser projector to a 150" screen. the design of the space utilizes 4 in-ceiling 8" full-range drives. A laptop will be connected to the projector via HDMI, for ease of use, in which the projector will send the audio signal to an amp powering the speakers.
Audio doesn't have to be top-notch high-end immersive, but it needs to be much better than a standard tv speaker. (budget is very limited)
so the plan is to have a 2 channel amp where two speakers would be wired in parallel to one channel, here are more details
Room dimensions: 7.5m × 4.5m
Audio drives: Dayton Audio ME820C 8" 8-Ohm 45W RMS (×4)
Amplifier: not yet decided, maybe (Fosi Audio BT20A100W + 100W)
I've been reading about parallel vs series connections, Parallel seems fine but there is always a warning about the risk of running it due to increased voltage which can damage equipment. I've searched how voltage is calculated and how to compare it to the amp and speakers specs but couldn't find anything useful. So, what is the procedure and calculation necessary to avoid damaging equipment when connecting speakers in parallel?
I would be grateful for any explanations or comments in general.
Cheers.
I'm not very experienced in DIY Audio, but man I'm loving it!
I'm currently working on a design of a small lecture room, media will be displayed via laser projector to a 150" screen. the design of the space utilizes 4 in-ceiling 8" full-range drives. A laptop will be connected to the projector via HDMI, for ease of use, in which the projector will send the audio signal to an amp powering the speakers.
Audio doesn't have to be top-notch high-end immersive, but it needs to be much better than a standard tv speaker. (budget is very limited)
so the plan is to have a 2 channel amp where two speakers would be wired in parallel to one channel, here are more details
Room dimensions: 7.5m × 4.5m
Audio drives: Dayton Audio ME820C 8" 8-Ohm 45W RMS (×4)
Amplifier: not yet decided, maybe (Fosi Audio BT20A100W + 100W)
I've been reading about parallel vs series connections, Parallel seems fine but there is always a warning about the risk of running it due to increased voltage which can damage equipment. I've searched how voltage is calculated and how to compare it to the amp and speakers specs but couldn't find anything useful. So, what is the procedure and calculation necessary to avoid damaging equipment when connecting speakers in parallel?
I would be grateful for any explanations or comments in general.
Cheers.
The first thing is to not run the amp into too low of an impedance. Two 8 ohm speakers in parallel is 4 ohms so check the amp can do that.
I'm not sure where the part about increased Voltage fits into it.
I'm not sure where the part about increased Voltage fits into it.
There is no voltage increasing, but current increasing (from amplifier output) when connecting two speakers in parallel.
ME820C are 8-ohm speakers, in parallel combined are 4-ohm, so no problem for the amplifier, although I would rather choose 18Vdc supply then, instead of 24Vdc for the BT20A amplifeir (or any other amp with TPA3116 chip inside).
ME820C are 8-ohm speakers, in parallel combined are 4-ohm, so no problem for the amplifier, although I would rather choose 18Vdc supply then, instead of 24Vdc for the BT20A amplifeir (or any other amp with TPA3116 chip inside).
This is exactly what I've been skeptical about, how did you come to such conclusion? Is there a way to calculate, or is it through experience?
Also, I assume the issue of high current would ovcut only if the speakers are blasting at maximum power.
Also, wouldn't there be a problem with the TPA3116 board since each channel can run 50W max, while both speakers RMS Total 90W?
No problem with that.
Connect one pair of paralleled 8 ohm speakers to one channel of the amplifier.
Connect the other pair of paralleled 8 ohm speakers to the other channel.
The speakers only consume as much power as the amp is capable of supplying to them - in this case up to a maximum of 50 W.
90 W speakers can not overload a 50 W amplifier, if that's what you are thinking.
I'm aware of the underpowered amp situation, but why sacrifice volume?
Also, signal distortion might occur as well
It seems I misunderstood your question.
In this PA situation, I would choose a combined speaker power handling capacity which is at least equal to, or preferably greater than, the RMS power rating of the amplifier.
That way, you are less likely to run into speaker distortion.
In this PA situation, I would choose a combined speaker power handling capacity which is at least equal to, or preferably greater than, the RMS power rating of the amplifier.
That way, you are less likely to run into speaker distortion.
I've just looked at the Fosi Audio BT20A100W+100W amplifier and would suggest that it is underpowered for your purposes.
I would look to buy a 100W+100W PA amplifier. Something along these lines: https://www.kpms.co.uk/product/stereo-pa-2x-amp-8ohms/
I would look to buy a 100W+100W PA amplifier. Something along these lines: https://www.kpms.co.uk/product/stereo-pa-2x-amp-8ohms/
Still the problem with high current is there... How do professionals know if electric current can damage components?
Are you comparing the 200 W onto 4 ohm figure with the 100W into 8 ohm figure of the amp to which I linked?
I wouldn't worry about overloading the 4 ohm speaker combination as you likely to be drawing only a fraction of the maximum power in normal use.
To go back on what I previously said, as long as you employ judicious use of the volume control, you won't overload your 96W RMS, 4 ohm speaker combination. You would hear the speakers distorting long before you would damage them. A bit of amp power in reserve for peaks is no bad thing.
For a 100W amplifier channel working at full output, the current through a 4 ohm load is only 5A.
This splits between the two paralleled 8 ohm speakers, so that is only 2.5A in each driver.
And that is at full output, which you will never use. Typical use to avoid severe clipping distortion,
would be more like 10W total amplifier output. In this case the current would be only 0.8A per driver.
This splits between the two paralleled 8 ohm speakers, so that is only 2.5A in each driver.
And that is at full output, which you will never use. Typical use to avoid severe clipping distortion,
would be more like 10W total amplifier output. In this case the current would be only 0.8A per driver.
Power = I x I x R
average power in Watts
I = current in Amperes rms
R = resistance in Ohms
Yes, P = I x I x R. However, in case you don't know:
The calculation is complicated by the fact that an 8 ohm speaker does not actually have a constant resistance (or more correctly, impedance) of 8 ohm.
Instead, the impedance of a loudspeaker varies with frequency like in the attached graph.
8 ohm is simply the nominal value - usually to be found around 400 to 1,000 Hz.
The calculation is complicated by the fact that an 8 ohm speaker does not actually have a constant resistance (or more correctly, impedance) of 8 ohm.
Instead, the impedance of a loudspeaker varies with frequency like in the attached graph.
8 ohm is simply the nominal value - usually to be found around 400 to 1,000 Hz.
Attachments
Plenty helpful,
now if I may, I have another question relative to wiring in parallel. The speakers I've selected have banana plug inserts, so how do I go about connecting wires in and from the speakers. My first thought was to have two wires in one banana plug one from the amp to the first speakers and the second from the first to the second speakers. My gut is telling me this is not how banana plugs should be used, so how do I go on about creating the parallel connection?
Cheers
now if I may, I have another question relative to wiring in parallel. The speakers I've selected have banana plug inserts, so how do I go about connecting wires in and from the speakers. My first thought was to have two wires in one banana plug one from the amp to the first speakers and the second from the first to the second speakers. My gut is telling me this is not how banana plugs should be used, so how do I go on about creating the parallel connection?
Cheers
You said you had four, in-ceiling full range drivers.
Please attach a photograph of their "banana plug inserts".
I would 'daisy chain' each stereo pair together i.e. a single cable from amp to first driver, then another from first driver to second driver. That would necessitate a join in the two cables to be made at the first driver.
Please attach a photograph of their "banana plug inserts".
I would 'daisy chain' each stereo pair together i.e. a single cable from amp to first driver, then another from first driver to second driver. That would necessitate a join in the two cables to be made at the first driver.
It's not as simple as that. If I get sixteen 8ohm 1Watt speakers and wire them in parallel then the load on the amplifier is 0.5ohm. The amplifier will run into its current limit, due to the unusually low load impedance, long before it makes the 16Watts needed to blow up the speakers.
Anyway, to answer the OP's question the TPA3116 is a relatively sophisticated amplifier chip, so it should not be possible to damage it running something as trivial as a 4ohm load. Technically with a 24VDC supply you can make 71Watts into 4ohms, however that is only under ideal conditions (sine wave signal, perfect amplifier efficiency, a power supply that doesn't voltage sag under heavy load, etc). 24V and 4ohm is 6amps of current, which is below the 7.5A current limit of the chip. On music/movies it's unlikely that you'd even hit the rated 50W average power rating of the TPA3116, unless you drive the amp into clipping for some time. The only remaining concern is how well the chip is cooled. If the heatsink Fosi Audio uses in that particular design is inadequate, the chip may overheat and go into protection before it makes the rated 50W per channel power. I would say it will be just fine with what you're planning to do. If the amplifier shuts down when you're running it hard, then you know why.
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