Pre/Pro which has bi-amping capabilities

lovinthehd

lovinthehd

Seriously, I have no life.
What’s the difference between bridged and bi amped as My 10 channel poaa1hd can be bridged to 300 watts in a 5.1 setup.Otherwise it’s 150 watts per channel.
Bridging a pair of amp channels combines them into a single channel output; bi-amping is sending two channels of amplification to two parts of a speaker (like the midbass driver and the tweeter in a two way speaker).
 
Grassy

Grassy

Full Audioholic
Bridging a pair of amp channels combines them into a single channel output; bi-amping is sending two channels of amplification to two parts of a speaker (like the midbass driver and the tweeter in a two way speaker).
Thanks mate, I have never bridged my amp before but have been thinking about doing so. I just don’t know if it would be worth doing. What benefits would i get from doing it.?
 
Irvrobinson

Irvrobinson

Audioholic Spartan
What’s the difference between bridged and bi amped as My 10 channel poaa1hd can be bridged to 300 watts in a 5.1 setup.Otherwise it’s 150 watts per channel.
Bridging uses two audio amplifiers operating on the same input signal in opposite phase, combining the outputs before the speaker terminals, doubling potential amplifier power output. Bridged amplifiers also have the advantage of an increased Common Mode Rejection Ratio, which significantly reduces noise and distortion in the audio path relative to unbridged versions of the same circuit, by using phase cancellation. On the other hand, bridged amplifiers see half the load impedance of unbridged amplifiers. This means a bridged design needs increased capability in the output stages and the power supply to handle similar speaker loads, especially speakers that have very load (e.g. 2 ohms) impedance dips. Because almost all modern solid state amplifiers have balanced output stages anyway (usually called differential output stages), a balanced amplifier's outputs are effectively dual-differential, so you have four output stages doing the work of one. It's arguable whether or not balanced/bridged amplifiers are really audibly better or not, but it makes for great advertising copy.

The more sane reason to bridge amplifier channels is to get the 3db more output voltage, meaning the power doubling. So bridging two 150 watt channels makes a single 300 watt channel. The question is, do you really need 300 watts per channel, or does it just seem cool? If you have inefficient many-driver speakers in a huge room the greater power output may help, but most people don't. (If your speakers only have two or three drivers of modest size the answer is almost certainly no.)
 
Grassy

Grassy

Full Audioholic
Bridging uses two audio amplifiers operating on the same input signal in opposite phase, combining the outputs before the speaker terminals, doubling potential amplifier power output. Bridged amplifiers also have the advantage of an increased Common Mode Rejection Ratio, which significantly reduces noise and distortion in the audio path relative to unbridged versions of the same circuit, by using phase cancellation. On the other hand, bridged amplifiers see half the load impedance of unbridged amplifiers. This means a bridged design needs increased capability in the output stages and the power supply to handle similar speaker loads, especially speakers that have very load (e.g. 2 ohms) impedance dips. Because almost all modern solid state amplifiers have balanced output stages anyway (usually called differential output stages), a balanced amplifier's outputs are effectively dual-differential, so you have four output stages doing the work of one. It's arguable whether or not balanced/bridged amplifiers are really audibly better or not, but it makes for great advertising copy.

The more sane reason to bridge amplifier channels is to get the 3db more output voltage, meaning the power doubling. So bridging two 150 watt channels makes a single 300 watt channel. The question is, do you really need 300 watts per channel, or does it just seem cool? If you have inefficient many-driver speakers in a huge room the greater power output may help, but most people don't. (If your speakers only have two or three drivers of modest size the answer is almost certainly no.)
Thankyou for that explanation. I think I will just leave things as they are. My setup sounds good as is, although I would love to hear my in ceiling speakers in the atmos mix as sometimes I forget they are there.I can never hear them.
 
lovinthehd

lovinthehd

Seriously, I have no life.
Thanks mate, I have never bridged my amp before but have been thinking about doing so. I just don’t know if it would be worth doing. What benefits would i get from doing it.?
Like Irv says, one consideration is the impedance change and whether you need the power aside from that. Some amps aren't meant to be bridged, too. Yours is, tho, should you find the situation that that's a better way to go than not. Sounds like you're fine as is.
 
Grassy

Grassy

Full Audioholic
Like Irv says, one consideration is the impedance change and whether you need the power aside from that. Some amps aren't meant to be bridged, too. Yours is, tho, should you find the situation that that's a better way to go than not. Sounds like you're fine as is.
Yep I think your right mate. :)
 
Irvrobinson

Irvrobinson

Audioholic Spartan
A lot of people are fascinated by bi-amping and bridging, but the truth is that most modern solid-state amplifiers are sufficient for most speakers in most rooms. In a huge room with complex hero speakers on demanding material there might be a difference, but most often not. It might be less exciting, but most people don't need either amplification strategy.
 
Good4it

Good4it

Audioholic Chief
How do you bridge an amp and how you know if can be bridged? Without harming it?
 
Verdinut

Verdinut

Audioholic Ninja
What’s the difference between bridged and bi amped as My 10 channel poaa1hd can be bridged to 300 watts in a 5.1 setup.Otherwise it’s 150 watts per channel.
Bridging two amplifiers together enables them to operate as a single more powerful amplifier. However, not all amplifiers can be bridged together.
 
Verdinut

Verdinut

Audioholic Ninja
How do you bridge an amp and how you know if can be bridged? Without harming it?
Bridging consists of connecting the output of two bridgeable amplifiers in series. This enables them to operate as a single amplifier with a power which is double to triple that of one single amplifier. The manufacturer always specifies when a multi-channel amplifier can be bridged as well as the minimum speaker impedance to be connected when bridged.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Bridging uses two audio amplifiers operating on the same input signal in opposite phase, combining the outputs before the speaker terminals, doubling potential amplifier power output. Bridged amplifiers also have the advantage of an increased Common Mode Rejection Ratio, which significantly reduces noise and distortion in the audio path relative to unbridged versions of the same circuit, by using phase cancellation. On the other hand, bridged amplifiers see half the load impedance of unbridged amplifiers. This means a bridged design needs increased capability in the output stages and the power supply to handle similar speaker loads, especially speakers that have very load (e.g. 2 ohms) impedance dips. Because almost all modern solid state amplifiers have balanced output stages anyway (usually called differential output stages),a balanced amplifier's outputs are effectively dual-differential, so you have four output stages doing the work of one. It's arguable whether or not balanced/bridged amplifiers are really audibly better or not, but it makes for great advertising copy.

The more sane reason to bridge amplifier channels is to get the 3db more output voltage, meaning the power doubling. So bridging two 150 watt channels makes a single 300 watt channel. The question is, do you really need 300 watts per channel, or does it just seem cool? If you have inefficient many-driver speakers in a huge room the greater power output may help, but most people don't. (If your speakers only have two or three drivers of modest size the answer is almost certainly no.)
This post is incorrect. Bridging amplifier channels doubles the voltage swing, not the power. In theory this should result in 4x the power, not 2x, but the actual gain is dependent on output stage design considerations. In the case the OP made the rated bridged output power is 2x, but I should have said twice the voltage in my post, not twice the power. I was thinking about what I posted this morning and thought that made no technical sense, and upon rereading I was appalled. My apologies for posting a brain fart.
 
Last edited:
M Code

M Code

Audioholic General
This post is incorrect. Bridging amplifier channels doubles the voltage swing, not the power. In theory this should result in 4x the power, not 2x, but the actual gain is dependent on output stage design considerations. In the case the OP made the rated bridged output power is 2x, but I should have said twice the voltage in my post, not twice the power. I was thinking about what I posted this morning and thought that made no technical sense, and upon rereading it was appalled. My apologies for posting a brain fart.
In theory.. Yes.. 4X the voltage is possible...
But.. How much is available?
That really depends upon power supply specs and where the output protection thresholds are set. Also when an amplifier is bridged both the + & - outputs are above chassis ground...

Just my $0.02... ;)
 
Irvrobinson

Irvrobinson

Audioholic Spartan
In theory.. Yes.. 4X the voltage is possible...
But.. How much is available?
That really depends upon power supply specs and where the output protection thresholds are set. Also when an amplifier is bridged both the + & - outputs are above chassis ground...

Just my $0.02... ;)
You did it too. It's twice the voltage, not 4x the voltage.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
I just wanted to throw in a few thoughts here.

This is a topic that has interested me for a while. What are the benefits of biamping, active crossovers, and why for each?

The conclusion I’ve drawn is that for the most part there is very little benefit to either over a well implemented passive design, but it’s still a superior approach for a number of reasons and something speaker designers should use where possible. Consumers should largely not worry about it.

Let’s start with bi-amping. A lot of benefits have been attributed to it such as more headroom and reduced distortion. I don’t believe they either is a real benefit. Let me explain why I feel that way:
-the reduction in amplifier distortion when its highpassed is really small within its linear range. Since amplifiers already have inaudible distortion any reduction in TIM or other non-harmonic distortions is so minimal as to be inaudible.
-I believe that the audible benefits attributed to biamping is actually an increase in dynamic range and that this could just as easily be achieved with a larger amplifier. However, if someone is using a receiver with this capacity and has no ability to add amps, it’s peobably a worthy thing to do. It may add a few dB of extra headroom. It certainly won’t hurt anything. Still, all else being equal, a bigger amplifier makes more sense. The woofers generally draw the most power and as such you may be exceeding your receiver in the woofer alone. The little bit of power the tweeter uses is too inconcequential to matter.

Some may suggest that an active crossover is superior because the amplifier only produces the frequencies it needs to in driving the speaker. That this is somehow not true of a passive crossover. That would actually suggest a misunderstanding of how a passive filter operates. Passive filters do not dissipate energy as heat below the crossover frequency (for a highpass filter). Instead they modify the load of the speaker that the amp sees. This means that the speaker presents a very high impedance load below the crossover and if there is no lowpass filter and woofer, the amplifier would not produce those low frequencies with any intensity. In other words, if you look at the transfer function or a tweeter and it’s highpass filter in isolation and find that it only draws 15 watts to produce 100dB. Then that’s all the amplifier will draw (crossover losses not withstanding). Crossover losses themselves are not that great. The series resistor in an l-pad is the greatest loss to heat and we still see that most speakers rarely could draw more than a few dozen watts across the tweeter before exceeding the tweeters maximum output. The actual losses toninefficiency here are fractions of a decibel. Again, an L-pad does not reduce the output of a tweeter by simplying soaking up excess power and converting it to heat. It raises the resistance of the load and the amplifier simplies produces less power.

For those who don’t believe me, if you put a load in an amplifier and then plug your soundcard mic input to the amplifier output, while the load might see 100 watts, the mic input would see fractions of a watt. Remove the load and nothing changes but the amplifier is no longer producing 100 watts, it’s now only producing a fraction of a watt. This is precisely how a headphone output on many receivers work. A few low wattage resistors create a high impedance load for the headphone out. Mixed with the high impedance of the headphones and the amplifier simply produces a lot less power.

So the take-away is that active or passive crossovers Both cause the amplifier to produce less power in a bi-amp scenario for the high-passed amplifier. This only really matters if the amplifier is being driven into a non-linear State. Which is possible, but then, a larger amp has the same sonic benefit.

See this diagram for an example:
1843CC84-1ED1-453B-BABC-D938CF1325CE.gif

So what about the benefits of active crossovers themselves? Well, here I see benefits but it’s not cut and dry for me. First, to go back to the classic argument of DBT’s as the gold standard for anything we do subjectively. I know or no studies where active vs passive were compared under tightly controlled conditions, nor am I aware of any such studies looking at objective measurable benefits either. Instead it seems to be a handful of selective experiments and conjecture. Some of it I think is valid and some I think is not.

Crossover accuracy: theoretically an active crossover can be more precise than a passive one ensuring greater consistency between speakers. While true, it’s very easy to match parts, hold tight tolerances, and ensure such accuracy in passive crossovers. I see this as false accuracy. I see no reason this could make an audible benefit given how accurate passive crossovers are.

Crossover losses: it is true that passive crossovers have losses that create insertion loss. This wouldn’t cause a sound quality difference but it is wasteful. I see this as more a minor but real problem. Good crossovers with low dcr parts have very little loss. Really bad crossovers might show a 1-2dB loss, but good crossovers are fraction of a dB. I don’t lose sleep over this.

Ability to EQ response: ok I hear this a lot. That an active crossover can create a flatter response. Many point to the extremely flat response of many active studio monitors as proof. In fact, this is a real benefit but one that should be taken in context. Passive crossovers can eq as well. Trap filters can be built which apply PEQ that is more than adequate to create a flat response. The issue is that it is cheap and easy to apply many filters in an active system. It is complex and expensive to do the same with passive parts. Still, most good high end speakers have a handful of trap filters in the crossover. So while an active system may have a flatter response, it’s also possible that this is not audible. All else being equal, I prefer the active approach for this reason, but I also recognize that some of this is academic.

Time alignment: digital crossovers can apply time delay to drivers simply, easily, and accurately. Passive crossovers can do this too, but the circuit is complex and hard to calculate. It’s also limited in its range of values, but...given how close the drivers are to being time aligned typically, often this passive approach is adequate. Further, it’s hightly debates if there is any audible benefit to a phase linear system. A good deal of research seems to suggest that phase coherent is good enough and time delay isn’t needed for this. Again, I see this as an academic benefit that I want if I can have it, but I wouslnt lose sleep over it.

So in conclusion my view is that in a perfect world an active system is better, but a passive system is not as bad as people think. All else being equal, no reason not to go active. Getting back to reality, there are other speaker priorities that make a much bigger difference and should take precedence over biamping and active filters.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
And I’ll just add that in a scenario like mentioned by the OP, where the passive crossover is retained and biamping is applied, I suspect any audible difference is simply the small increase in headroom. I suspect how big a difference this makes is speaker dependent and that in general, a bigger amplifier is a better fix to this problem.
 
BoredSysAdmin

BoredSysAdmin

Audioholic Overlord
I just wanted to throw in a few thoughts here.

This is a topic that has interested me for a while. What are the benefits of biamping, active crossovers, and why for each?

The conclusion I’ve drawn is that for the most part there is very little benefit to either over a well implemented passive design, but it’s still a superior approach for a number of reasons and something speaker designers should use where possible. Consumers should largely not worry about it.

Let’s start with bi-amping. A lot of benefits have been attributed to it such as more headroom and reduced distortion. I don’t believe they either is a real benefit. Let me explain why I feel that way:
-the reduction in amplifier distortion when its highpassed is really small within its linear range. Since amplifiers already have inaudible distortion any reduction in TIM or other non-harmonic distortions is so minimal as to be inaudible.
-I believe that the audible benefits attributed to biamping is actually an increase in dynamic range and that this could just as easily be achieved with a larger amplifier. However, if someone is using a receiver with this capacity and has no ability to add amps, it’s peobably a worthy thing to do. It may add a few dB of extra headroom. It certainly won’t hurt anything. Still, all else being equal, a bigger amplifier makes more sense. The woofers generally draw the most power and as such you may be exceeding your receiver in the woofer alone. The little bit of power the tweeter uses is too inconcequential to matter.

Some may suggest that an active crossover is superior because the amplifier only produces the frequencies it needs to in driving the speaker. That this is somehow not true of a passive crossover. That would actually suggest a misunderstanding of how a passive filter operates. Passive filters do not dissipate energy as heat below the crossover frequency (for a highpass filter). Instead they modify the load of the speaker that the amp sees. This means that the speaker presents a very high impedance load below the crossover and if there is no lowpass filter and woofer, the amplifier would not produce those low frequencies with any intensity. In other words, if you look at the transfer function or a tweeter and it’s highpass filter in isolation and find that it only draws 15 watts to produce 100dB. Then that’s all the amplifier will draw (crossover losses not withstanding). Crossover losses themselves are not that great. The series resistor in an l-pad is the greatest loss to heat and we still see that most speakers rarely could draw more than a few dozen watts across the tweeter before exceeding the tweeters maximum output. The actual losses toninefficiency here are fractions of a decibel. Again, an L-pad does not reduce the output of a tweeter by simplying soaking up excess power and converting it to heat. It raises the resistance of the load and the amplifier simplies produces less power.

For those who don’t believe me, if you put a load in an amplifier and then plug your soundcard mic input to the amplifier output, while the load might see 100 watts, the mic input would see fractions of a watt. Remove the load and nothing changes but the amplifier is no longer producing 100 watts, it’s now only producing a fraction of a watt. This is precisely how a headphone output on many receivers work. A few low wattage resistors create a high impedance load for the headphone out. Mixed with the high impedance of the headphones and the amplifier simply produces a lot less power.

So the take-away is that active or passive crossovers Both cause the amplifier to produce less power in a bi-amp scenario for the high-passed amplifier. This only really matters if the amplifier is being driven into a non-linear State. Which is possible, but then, a larger amp has the same sonic benefit.

See this diagram for an example:
View attachment 27517

So what about the benefits of active crossovers themselves? Well, here I see benefits but it’s not cut and dry for me. First, to go back to the classic argument of DBT’s as the gold standard for anything we do subjectively. I know or no studies where active vs passive were compared under tightly controlled conditions, nor am I aware of any such studies looking at objective measurable benefits either. Instead it seems to be a handful of selective experiments and conjecture. Some of it I think is valid and some I think is not.

Crossover accuracy: theoretically an active crossover can be more precise than a passive one ensuring greater consistency between speakers. While true, it’s very easy to match parts, hold tight tolerances, and ensure such accuracy in passive crossovers. I see this as false accuracy. I see no reason this could make an audible benefit given how accurate passive crossovers are.

Crossover losses: it is true that passive crossovers have losses that create insertion loss. This wouldn’t cause a sound quality difference but it is wasteful. I see this as more a minor but real problem. Good crossovers with low dcr parts have very little loss. Really bad crossovers might show a 1-2dB loss, but good crossovers are fraction of a dB. I don’t lose sleep over this.

Ability to EQ response: ok I hear this a lot. That an active crossover can create a flatter response. Many point to the extremely flat response of many active studio monitors as proof. In fact, this is a real benefit but one that should be taken in context. Passive crossovers can eq as well. Trap filters can be built which apply PEQ that is more than adequate to create a flat response. The issue is that it is cheap and easy to apply many filters in an active system. It is complex and expensive to do the same with passive parts. Still, most good high end speakers have a handful of trap filters in the crossover. So while an active system may have a flatter response, it’s also possible that this is not audible. All else being equal, I prefer the active approach for this reason, but I also recognize that some of this is academic.

Time alignment: digital crossovers can apply time delay to drivers simply, easily, and accurately. Passive crossovers can do this too, but the circuit is complex and hard to calculate. It’s also limited in its range of values, but...given how close the drivers are to being time aligned typically, often this passive approach is adequate. Further, it’s hightly debates if there is any audible benefit to a phase linear system. A good deal of research seems to suggest that phase coherent is good enough and time delay isn’t needed for this. Again, I see this as an academic benefit that I want if I can have it, but I wouslnt lose sleep over it.

So in conclusion my view is that in a perfect world an active system is better, but a passive system is not as bad as people think. All else being equal, no reason not to go active. Getting back to reality, there are other speaker priorities that make a much bigger difference and should take precedence over biamping and active filters.
Sorry for a possibly stupid question, but is it possible that relatively inexpensive driver would show different distortion and/or non-linear response at a different power level, possibly requires more "active" EQ correction rather than a static one?
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Sorry for a possibly stupid question, but is it possible that relatively inexpensive driver would show different distortion and/or non-linear response at a different power level, possibly requires more "active" EQ correction rather than a static one?
For the most part, eq only applies to linear distortion. In this case, yes poor quality drivers require more eq. However the eq filters are still static. Active doesn’t mean dynamic. Very few speakers use dynamic eq. That is used on better systems to improve their performance at the limits but again, not something average joe needs to worry about. If I were designing a cheap speaker, I would apply limiters and dynamic eq to help the speaker play louder with less distortion. This is different from biamping or active filters generally.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Here are several arguments by Rod Elliott in favor of active bi-amping:

http://sound.whsites.net/bi-amp.htm
That’s the exact article I was referencing when I mentioned articles loaded with conjecture but lacking in proof. It’s a good read but it overstated the benefits in my opinion. Taking TIM from inaudible to more inaudible is of no practical benefit. He also makes a lot of claims about crossovers that assume pretty crappy crossovers and axagerate the seriousness of those distortions. Which is all to say, I think everything he says is right but I still question how much merit it has. Certainly we have no proof that it makes a difference. It just hasn’t been studied.
 

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