Bi-amping vs dual mono setup. Which would sound better?

[Grenadeslio]

If you're doing the ubiquitous 2-way with a 15" woofer crossed to a horn, you're hopefully crossing low enough to mitigate abrupt change in directivity. So you're going for a larger CD and giving up a little on the very top (the eternal 2-way compromise). Such CD's are usually rated well over 100W (with proper XO to limit excursion at the bottom end).

However, that XO point is going to have to be somewhere around 1kHz, depending whether you compromise on directivity or maximum volume. Power spectral density of music is balanced above and below about 250-350Hz, depending of course on the particular music. So the woofer will be using a good portion of the power between that balance frequency and the XO to the CD. It does seem that in that case a lot less power is needed for the tweeter.

I use three-way speakers and biamp between the woofers and the combined teeters and mids(passive XO retained for the tweeter also confers DC fault protection). The XO is at 300Hz, so it works out nicely. I still use more power on the woofers, because they present more reactive impedance and can handle the power.

All this talk about improved channel separation from vertical biamping is nonsense. You only need 30dB max (20dB for most people under most conditions). In a real setup in a real room, there's a lot of interaural crosstalk going on, no matter how perfect the amps and speakers. Even exceptional phono cartridges might only have 30-35dB of channel separation, but most are well below that. The analog tape machines that much classic music was recorded and mastered on had less than 50dB of channel separation. Any amplifier with less than 40dB of channel separation would be an atrociously bad design or broken, more so if it degraded to that degree under heavy load. Most amps spec better than 70dB of channel separation, far more than necessary. If you were really worried about channel separation, vertical biamping would be the worst case. There's much more difference between the high/low signals (and crosstalk would have more consequences, especially IM distortion in the amp and drivers) than there is difference between L-R channels.

You're right, designing an amplifier like this is a complete waste of R&D and makes absolutely no sense whatsoever lol.

 

[fill35u]

You're right, designing an amplifier like this is a complete waste of R&D and makes absolutely no sense whatsoever lol.

At that power level- yes.

Compared to a single transformer of the same rating as the two combined, two separate power supplies are wasteful of size, weight, materials, and cost. They might have an advantage in heat dissipation, but that would be offset by their lower efficiency.

Why this approach fails on its own logic:
The two separate power supplies are identical (of course, because we expect the average and peak demands to be of similar magnitudes for both channels, even if they differ at times). Their optimum utilization is is when both channels have identical signals- otherwise, one channel has unused headroom. If both channels have identical signals, crosstalk is irrelevant. And the capacity of the two smaller supplies is the same as the hypothetical one big one- just less efficient in so many ways.

If one channel is at full volume while the other is quiet, the capacity of the quiet channel's power supply is unavailable. But with a single power supply of double capacity, the full volume channel can draw twice the power as it could with its dedicated half-sized supply. At one channel full volume, crosstalk into the quiet channel is irrelevant, and the quiet channel has no signal to induce into the full volume channel.

At low volumes, there's no reason the main power supply architecture should affect much, let alone crosstalk. If it does, the amp has PSRR problems that dual supplies aren't going to fix.

So full volume in one or both channels, low volume in one or both channels, dual power supplies don't make sense at this power level. Note that Kenwood doesn't specify the crosstalk or even PSRR for the KA-7300. You'd think after all that trouble, they'd want to brag about what they actually achieved in that regard.

Crosstalk avoidance is much more about physical layout and grounding than it is about separate power supplies. BTW, crosstalk and PSRR vary with frequency, like most specs.

 

[Grenadeslio]

At that power level- yes.

Compared to a single transformer of the same rating as the two combined, two separate power supplies are wasteful of size, weight, materials, and cost. They might have an advantage in heat dissipation, but that would be offset by their lower efficiency.

Why this approach fails on its own logic:
The two separate power supplies are identical (of course, because we expect the average and peak demands to be of similar magnitudes for both channels, even if they differ at times). Their optimum utilization is is when both channels have identical signals- otherwise, one channel has unused headroom. If both channels have identical signals, crosstalk is irrelevant. And the capacity of the two smaller supplies is the same as the hypothetical one big one- just less efficient in so many ways.

If one channel is at full volume while the other is quiet, the capacity of the quiet channel's power supply is unavailable. But with a single power supply of double capacity, the full volume channel can draw twice the power as it could with its dedicated half-sized supply. At one channel full volume, crosstalk into the quiet channel is irrelevant, and the quiet channel has no signal to induce into the full volume channel.

At low volumes, there's no reason the main power supply architecture should affect much, let alone crosstalk. If it does, the amp has PSRR problems that dual supplies aren't going to fix.

So full volume in one or both channels, low volume in one or both channels, dual power supplies don't make sense at this power level. Note that Kenwood doesn't specify the crosstalk or even PSRR for the KA-7300. You'd think after all that trouble, they'd want to brag about what they actually achieved in that regard.

Crosstalk avoidance is much more about physical layout and grounding than it is about separate power supplies. BTW, crosstalk and PSRR vary with frequency, like most specs.

And there's no reason for mono block amps other than MORE POWER either right? I've heard there are some out there that believe such nonsense but I always thought it just rumor lol.


No 600 Supreme for you, come back one year, NEXT!

 

[WaynerN]

I own the Sunfire II power amp. It boasts 660 watts RMS per channel. It is connected to my 20 year old Martin Logan reQuests. There is no other amplifier in my house (I have 15 others) that can produce effortless speed and dynamics, not to mention, sound fantastic basically at idle.

Power is not all of the equation. The speaker is an unusual load. It's impedance varies as the frequencies changes. Their efficiencies are bonded to this as well. Clean power produces clean headroom, and stable circuits within the amp.

 

[fill35u]

And there's no reason for mono block amps other than MORE POWER either right?

Isn't the point of all amplifiers MORE POWER?

Class A amps need all the dissipation they can get, monobloc designs help with that. Of course, if you go Class A you've decided efficiencies of cost, energy, materials, size, and weight are unimportant.
And some folks embrace excess as an aesthetic. There are some monobloc amp designs that are so heavy and bulky that they have multiple chassis.
Those are size/weight/power concerns, not for crosstalk prevention.

I've heard there are some out there that believe such nonsense but I always thought it just rumor lol.

What exactly do you consider "nonsense"? If it's so ridiculous, it should be easy for you to explain why...

No 600 Supreme for you, come back one year, NEXT!

That 600 is beautiful, just like the KA-7300. I wouldn't turn down either if offered. But I also wouldn't be able to fit either into my system.

And while we're still talking about vintage Kenwood, notice how the most powerful amp from the same lineup has only a single transformer for two channels? No 700M for you!

 

[Grenadeslio]

Isn't the point of all amplifiers MORE POWER?

Class A amps need all the dissipation they can get, monobloc designs help with that. Of course, if you go Class A you've decided efficiencies of cost, energy, materials, size, and weight are unimportant.
And some folks embrace excess as an aesthetic. There are some monobloc amp designs that are so heavy and bulky that they have multiple chassis.
Those are size/weight/power concerns, not for crosstalk prevention.



What exactly do you consider "nonsense"? If it's so ridiculous, it should be easy for you to explain why...



That 600 is beautiful, just like the KA-7300. I wouldn't turn down either if offered. But I also wouldn't be able to fit either into my system.

And while we're still talking about vintage Kenwood, notice how the most powerful amp from the same lineup has only a single transformer for two channels? No 700M for you!

Again, you're so concerned with more power when it's the nuances that make "music".

 

[fill35u]

Again, you're so concerned with more power

I think you misunderstood me?
I gave an example of Class A amps as monobloc design that made sense. Class A is usually the last direction anybody goes if they're looking for simply more power.
I'm also the guy who measured that I'm typically listening with only 1/100th of a Watt?:
https://audiokarma.org/forums/index.php?threads/one-watt.884740/page-18#post-13097786

This thread so far has been about the best utilization of existing amp power capacity. Power supply design, horizontal vs. vertical configuration, headroom vs. volume, channel crosstalk via poor PSRR, efficiency of active vs. passive XO's, output impedance and current capability of series bridging- none of that stuff matters unless you're actually using much of the available power.

when it's the nuances that make "music".

Not the inaudible ones.

 

[Grenadeslio]

Misunderstood nothing.

Your statements not mine.

"Isn't the point of all amplifiers MORE POWER?"

"And while we're still talking about vintage Kenwood, notice how the most powerful amp from the same lineup has only a single transformer for two channels? No 700M for you!"

Ya, it's not about the power for you, let's go with that lol.

I listen to music, not concerned with touting how much power my equipment has.

Nice how Kenwood's "statement" piece does have a true dual mono design isn't it? I think they might have had an idea or two on what they were doing.

 

[fill35u]

"Isn't the point of all amplifiers MORE POWER?"

How are you arguing that the purpose of a power amplifier is not to provide more power?

"And while we're still talking about vintage Kenwood, notice how the most powerful amp from the same lineup has only a single transformer for two channels? No 700M for you!"

Ya, it's not about the power for you, let's go with that lol.

Then you did misunderstand me. You gave an example of a Dual Power amp as sonically superior because it had two power supplies. I gave a counterexample of an amplifier from the same manufacturer and vintage that had a single power supply. If Kenwood really thought Dual Power conferred an actual sonic advantage (rather than mere marketing), why weren't all their amps built that way?

I listen to music, not concerned with touting how much power my equipment has.

Again, as I have pointed out in several threads, including this one, I typically listen with a *hundredth* of a Watt. Is it "touting" if I provide an example of how little power I use? If it makes you feel better, I admit that yes, occasionally I use more...
This thread has so far been about best utilization of available amplifier capacity, including your contributions. The presumption is that the participants are interested in optimizing power usage- while maintaining sound quality, not ignoring it.

 

[Grenadeslio]

I believe the point of this thread is musical quality, not how much power we can achieve. So maybe we can stop trying to run the thread of its track eh?

Bi-amping vs dual mono setup. Which would sound better?

And do you think maybe it cost a bit more to implement a true dual mono design and not everyone is concerned with spending more for it? Many like you are more concerned with watts/$ than quality and that's ok, but it's simple economics, Kenwood knew many wouldn't get it.

 

[Thud3]

Cajun, I vote one bridged power amp per channel. Easy to do if your amps have a switch for bridging.
Your preamp will still be in charge of separation, etc. Your power amps will just amplify the signal sent to them. No need to fuss with crossovers and such.

 

[Grenadeslio]

What if your speakers are 4 ohms?

Pro amps lol.

 

[fill35u]

I believe the point of this thread is musical quality, not how much power we can achieve. So maybe we can stop trying to run the thread of its track eh?

Bi-amping vs dual mono setup. Which would sound better?

Once again:

This thread so far has been about the best utilization of existing amp power capacity. Power supply design, horizontal vs. vertical configuration, headroom vs. volume, channel crosstalk via poor PSRR, efficiency of active vs. passive XO's, output impedance and current capability of series bridging- none of that stuff matters unless you're actually using much of the available power.

*You* were the one who tried to argue that multiple power supplies improve audio quality. We're still waiting on your proof, or at least a reasonable technical explanation.

And do you think maybe it cost a bit more to implement a true dual mono design and not everyone is concerned with spending more for it?

The Dual Power concept is needless excess for the point of marketing. Perhaps Kenwood abandoned it because not everyone is concerned with spending more?

Many like you are more concerned with watts/$ than quality and that's ok, but it's simple economics, Kenwood knew many wouldn't get it.

There's no practical reason to spend more than necessary to achieve a quality goal. There are *impractical* reasons such as aesthetics, brand loyalty, bragging rights, or ignorance. Kenwood was banking on people buying into Dual Power for the impractical reasons.

 

[toddalin]

Cajun, I vote one bridged power amp per channel. Easy to do if your amps have a switch for bridging.
Your preamp will still be in charge of separation, etc. Your power amps will just amplify the signal sent to them. No need to fuss with crossovers and such.

So, if I have this right..., your suggestion is four stereo amps, each bridged for mono operation, so that a bridged stereo amp runs the left woofer, another for the right woofer, another for the left tweeter, and another for the right tweeter in a bi-amp set-up or even just two stereo amps each bridged to produce stereo with two speakers and passive crossovers?

If this is the case, why bother with bridging the amps, adding to the complexity of the circuits and doubling the part count if you don't need the extra power? Seems like you would further degrade the signal over a non-bridged set-up. (I mentioned this way back.)

 

[fill35u]

What if your speakers are 4 ohms?

You could series bridge the Sunfire II amps @WaynerN mentioned above (with an external BTL adapter). They'd handle 4R loads just fine.

Or, parallel bridge each amp, to increase their ability to drive low impedance loads.

Or, simply don't play too loud. Series bridging would get you more headroom, at the expense of perhaps more noise due to increased gain.

But why go through the expense and trouble of buying separate amps and bridging them, if you don't need the power?

Oops, there I go talking about saving money and practical power requirements again...

 

[fill35u]

The bridged amp sees a 2 ohm load; if the speaker dips to 3 ohms then it sees 1.5 ohms.

Since you're splitting hairs:

The IEC standard 60268-3 specifies that impedance shall not fall below 80% of nominal, at any frequency. So if the impedance of a nominal 4R speaker dips below 3R2, you have an issue for the manufacturer or distributor to resolve.

The difficult part for an amp isn't impedance minima, it's regions of high reactance that demand peaks of current or power. You'd need the impedance and phase plot to determine the reactance at a given frequency, then compare to the SOA and response of the amp's protection circuitry.

Power compression from playing at continuously high volumes will help, since it will substantially increase the voice coil resistance. The effect depends on the speaker and signal, of course...

*Still not an issue unless playing at high volumes*. You guys keep bringing up power capacity...

 

[drp1003]

BI-AMPING I would do this if I had a very powerful home theater receiver like one of those Marantz's. I'd use the secondary pair of speaker outputs for the tweeter and the mains for the woofer.

Other than that, in any other circumstance, I would go with dual-mono.