Hi,
stop a moment and think.
Take a hypothetical 100W + 100W into 8ohm amplifier that is bridgable.
It will give 200W into 16ohm, if it is designed properly.
Now look at what you have, a pair of 4ohm speakers, in single mode they have too low an impedance and in bridgable mode the series pair have too low an impedance.
Let's take your thought processing a bit further.
Assume you have two 8ohm speakers.
The stereo amp will drive them to 100W + 100W. The total power delivered to the speakers is 200W.
Wire the amp in bridge mode. Wire the speakers in series.
Now when you drive the series pair in bridge mode you find the amplifier delivers 200W to them. You have gained (and lost) exactly nothing, except your time.
Don't wire your 4ohm drivers into an 8ohm amplifier.
stop a moment and think.
Take a hypothetical 100W + 100W into 8ohm amplifier that is bridgable.
It will give 200W into 16ohm, if it is designed properly.
Now look at what you have, a pair of 4ohm speakers, in single mode they have too low an impedance and in bridgable mode the series pair have too low an impedance.
Let's take your thought processing a bit further.
Assume you have two 8ohm speakers.
The stereo amp will drive them to 100W + 100W. The total power delivered to the speakers is 200W.
Wire the amp in bridge mode. Wire the speakers in series.
Now when you drive the series pair in bridge mode you find the amplifier delivers 200W to them. You have gained (and lost) exactly nothing, except your time.
Don't wire your 4ohm drivers into an 8ohm amplifier.
AndrewT said:
That makes no sense to me.
Hypothetically, lets say I have two 4 ohm 200 watt speakers, and a two channel amp capable of 100 watts rms per channel into 8 ohms. Lets say this amp is also capable of 200 watts rms into 8 ohms, bridged.
The math all adds up, to me.
4 ohm + 4 ohm in series = 8 ohms, and would split current equally since the resistances are equal on each voice coil, so why wouldn't it be the same at an 8 ohm 400 watt speaker?
I don't understand why you guys are saying in bridged mode the amp has to drive a 16 ohm load, because all the amps I have are capable of 8 ohms stereo and bridged mono.
One of them also says something about "maximum load bridged 4 ohm pair" but I'm not sure what that means.
Sammich said:
I isn't complicated, you can't get more power from the amp than it is capable. If it is a 400W amp than great.
But if it is a 200W amp, than it will try to produce 400W, then the outputs will burn up.
Bridging is like putting two channels in series, hence the load impeadances must be in series also. 2) 8 Ohm loads in series is 16 Ohms. If the amp is capable of driving 4 Ohms per channel, 8 Ohms bridged will work. BUT if it is 8 Ohms per channel, you are still putting a 4 Ohm load onto an 8 Ohm channel by bridging 8 Ohms(4 + 4), and the magic smoke may escape from the outputs.
Yes, but in a series circuit, current is the same for both resistors and voltage is split. AKA 2 series resistors is known as a voltage divider. Likewise, 2 parralell resistors is a current divider.
Hmmm..........
Making an amplifier bridgeable but only suitable for 8 ohms per
channel in stereo is stupid, though a few chips amps have been
built like this.
A bridgeable amplifier needs to be able to work into 4 ohms (2 ohms
for some some car amps) per channel. Bridged it will drive 8 ohms.
Is simply wrong one way or the other, per channel is half bridged.
A perfect stereo amplifier say 100W per channel bridged will deliver 400w one channel.
In practice a 100W 4ohm per channel gives 200W 8 ohm bridged.
In practice if the above has 8 ohm speakers its 50W per channel.
Adding a bridging circuit to a 8 ohm min per channel amplifier is a poor idea.
In practice is the same as wiring them parallel and driving them
with both channels in parallel, i.e. 4ohms connected to 8 ohm output.
Bridging does not make any difference.
/sreten.
Making an amplifier bridgeable but only suitable for 8 ohms per
channel in stereo is stupid, though a few chips amps have been
built like this.
A bridgeable amplifier needs to be able to work into 4 ohms (2 ohms
for some some car amps) per channel. Bridged it will drive 8 ohms.
Is simply wrong one way or the other, per channel is half bridged.
A perfect stereo amplifier say 100W per channel bridged will deliver 400w one channel.
In practice a 100W 4ohm per channel gives 200W 8 ohm bridged.
In practice if the above has 8 ohm speakers its 50W per channel.
Adding a bridging circuit to a 8 ohm min per channel amplifier is a poor idea.
In practice is the same as wiring them parallel and driving them
with both channels in parallel, i.e. 4ohms connected to 8 ohm output.
Bridging does not make any difference.
/sreten.
I hope I'm not coming over as argumentative, I know quite a bit about troubleshooting and building electronic devices, but it only comes from talent and doing it all my life as a hobby, as the math and science behind most of it I'm just now in the process of learning.
I'm just trying to understand.
For a moment, forget that I mentioned bridging, I think I have the wrong idea of how it works;
Let's say an amp has a min load of 8 ohms per channel, and outputs 100 watts RMS.
If I wire two 4 ohm speakers in series, and connect them to one channel, the resistance would add up to 8 ohms. The current will be equal, and the voltage will be split. IE, if the stereo were outputting a perfect 12 volt 1 amp sine wave @ 1KHz, each speaker would be receiving 6 volts @ 1 amp. How is that bad for the amplifier, if it was meant to drive 8 ohm loads in the first place?
That said, I understand that bridged, it would be the right channel and left channel in series, decreasing the allowable load to 16 ohms. I'm not sure why the amp manual I downloaded said that, maybe I don't understand it. Like I mentioned before, it says; Stereo impedance: 8-16 Ohms Mono (Bridged) impedance: 4 Ohm + 4 Ohm pair". I assumed this meant 8 ohms stereo 8 ohms bridged, but with the way you guys explained everything, I must be reading it wrong.
Am I close or am I totally off?
I'm just trying to understand.
For a moment, forget that I mentioned bridging, I think I have the wrong idea of how it works;
Let's say an amp has a min load of 8 ohms per channel, and outputs 100 watts RMS.
If I wire two 4 ohm speakers in series, and connect them to one channel, the resistance would add up to 8 ohms. The current will be equal, and the voltage will be split. IE, if the stereo were outputting a perfect 12 volt 1 amp sine wave @ 1KHz, each speaker would be receiving 6 volts @ 1 amp. How is that bad for the amplifier, if it was meant to drive 8 ohm loads in the first place?
That said, I understand that bridged, it would be the right channel and left channel in series, decreasing the allowable load to 16 ohms. I'm not sure why the amp manual I downloaded said that, maybe I don't understand it. Like I mentioned before, it says; Stereo impedance: 8-16 Ohms Mono (Bridged) impedance: 4 Ohm + 4 Ohm pair". I assumed this meant 8 ohms stereo 8 ohms bridged, but with the way you guys explained everything, I must be reading it wrong.
Am I close or am I totally off?
A lot of good points here.
Why is it that people feel the need to bridge everything and run it at the edge?
What you achieve in output power bridged is dependent upon its design and the power supply limitations. In theory the maximum gain would be X4. In practice however it can be much lower. Generally a X3 power output is more in line depending upon how much power supply sag their is.
Just my .02
Why is it that people feel the need to bridge everything and run it at the edge?
What you achieve in output power bridged is dependent upon its design and the power supply limitations. In theory the maximum gain would be X4. In practice however it can be much lower. Generally a X3 power output is more in line depending upon how much power supply sag their is.
Just my .02
Sammich said:
I believe that's where your analysis is going wrong. An amp that's rated for 8ohm operation is rated that way because of limited current capability. When you bridge an amp, it causes a halving of the impedance seen by the amp, therefore doubling the current into the same load. So if you have an amp that's only rated for 8ohm operation, it needs a 16ohm load in bridged mode, so that the amp will see an 8ohm load.
This is a pretty good explanation: http://www.bcae1.com/bridging.htm
Sammich said:
Like I mentioned before, it says; Stereo impedance: 8-16 Ohms Mono (Bridged) impedance: 4 Ohm + 4 Ohm pair". I assumed this meant 8 ohms stereo 8 ohms bridged, but with the way you guys explained everything, I must be reading it wrong.
Am I close or am I totally off?
Hi,
Yes. > 8 ohm bridged (one speaker), > 4 ohm (pair of speakers each) per channel normal is what it means.
/sreten.I have read and re-read those instructions.Sammich said:
I now realise what they are trying to (badly) say.
is telling the user that the amp is suitable for 8 to 16ohm speakers.
is telling the user that the amp can be used with a series connected pair of 4ohm speakers.
Based on electrical requirements this advice is plainly misleading and particularly so for those users with little electrical knowledge.
However, the instructions can be read differently.
would indicate that the amp is 8ohm capable
and can be bridged into 16ohms. but then the
becomes superfluous.
Rely on the general (and always true) rule. Bridging doubles the power into double the impedance.
Hmmm..........
The manual or where-ever it says this is a misprint.
It should say :
Mono (Bridged) impedance : 8-16 Ohms
Stereo impedance : 4 Ohm + 4 Ohm pair
It simply should say : bridged > 8 ohm, stereo > 4 ohm.
As I said earlier, if it cannot manage 8 ohms bridged its next to useless.
/sreten.
The manual or where-ever it says this is a misprint.
It should say :
Mono (Bridged) impedance : 8-16 Ohms
Stereo impedance : 4 Ohm + 4 Ohm pair
It simply should say : bridged > 8 ohm, stereo > 4 ohm.
As I said earlier, if it cannot manage 8 ohms bridged its next to useless.
/sreten.- Status
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