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post #451 of 651 Old 04-11-2014, 10:45 AM
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Originally Posted by amirm View Post

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Originally Posted by arnyk View Post

One answer is that a common form of ABX test is the straight-wire bypass test. In that case an unimpaired signal is one of the two sounds being compared. There is your control.

Another answer is that there are two comparisons that are embedded in every ABX test. Remember X is either A or B. In ABX X is compared to A and X is compared to B. But X is either A or B, so every trial includes a control which is the comparison of either A to itself or B to itself. There is your control.
Thank you very much for the answer Arny. The litmus test of a control is whether it can catch errors in the "system" which in this case includes both the listener and the score keeper/test creator. Let's review if your controls would have caught the errors in the Boston Audio Society test I linked to earlier: http://www.bostonaudiosociety.org/bas_speaker/abx_testing2.htm

A set of 23 double-blind trials was conducted listening to music through the system, with Tiefenbrun voting for the identity of "X" at each trial. It was then that Vanderkooy pointed out that, although the relays in the A/B/X box were switching normally during this series, no tiny electrical clicks were audible from the loudspeakers during their operation, as normally would be the case. Investigation revealed that the preamplifier's "source/tape" monitor switch had inadvertently been left in the "source" position, and as Fig. 2 reveals, the A/B/X box and digital system were thus not being inserted into the chain at all during this run!

I hope you agree that neither one of your controls would have caught this error since the ABX was not even used!

So what? As I have detailed in other posts, those weren't the only controls that we used. Besides, the above post is again demonizing ABX for problems that it shares with many other forms of subjective testing.

ABX doesn't have to be perfect, it merely needs to be appreciably better. Since the most common equipment evaluation technique to this day is the not level matched, not time-synched, sighted evaluation, its hard to imagine why anybody keeps picking nits with ABX.

I don't know about you, but I have long known that nothing is totally idiot-proof. Often the idiot is me! ;-)
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post #452 of 651 Old 04-11-2014, 11:23 AM
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Originally Posted by J_Palmer_Cass View Post

That is called passive bi-amping!

No, I'm talking about active biamplification with the crossover in front of the amplifier. But at this point I think I'll check out of this thread. I'm obviously not doing any good.
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post #453 of 651 Old 04-11-2014, 11:24 AM
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I did not see any mention of passive bi-amping in that review.

Arguing religion is rarely fruitful. Enjoy your system.


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post #454 of 651 Old 04-11-2014, 11:33 AM
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Quote:
Originally Posted by J_Palmer_Cass View Post

Quote:
Originally Posted by arnyk View Post

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Originally Posted by J_Palmer_Cass View Post

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Originally Posted by FMW View Post

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Originally Posted by J_Palmer_Cass View Post

Yes, but you did not mention what happens when you passive bi-amp the speaker / amplifier in question. Will the speaker receive more current with a passive bi-amp setup as compared with a straight AVR setup? .

No. current is limited by the power supply.


Read!

http://en.wikipedia.org/wiki/Clipping_(audio)

Did you check the article out before you blithely recommended it?

Here are the items in that could be relevant to an AVRs amplifier:
Quote:
"(1) The peak-to-peak of a solid-state transformerless amplifier (most integrated circuit and discrete solid state circuits) is limited to the power supply voltage less a small amount that depends on the design of the circuit (especially the driver configuration) and the saturation voltage (Vce(sat) for bipolar transistors, or Rds(on) for Field Effect Transistors)..."

The above is about a limit that is enforced by the power supply.
Quote:
"(2) If the power supply capacitor is no longer able to keep the voltage "flat" due to a massive current draw, the positive and negative voltage supply of the amplifier will fluctuate resulting in sort of a clipped signal that contains some AC line frequency harmonics."

The above is about a limit that is enforced by the power supply.
Quote:
"(3) An amplifier can limit the current output, or the input voltage, for a variety of reasons both intentional or not. Intentional limiting circuits would not be expected to come into effect in normal operation, but when the output load resistance is too low or the system is connected to an exceptionally high signal level, for example. The result of this form of clipping might not create a flat top to the Voltage waveform, but rather a flat top to the current waveform."

The above clearly says that current limiting in the output stage "Would not be expected to come into effect in normal operation." That means that it is not a problem with a properly designed output stage. I agree that there are a minority of AVR output stages that are marginal in this department, but to say that Passive Biamping is anything but a niche solution would require evidence that a high percentage of AVR output stages are poorly designed. That's a tall assertion that nobody should agree with just because someone said so and didn't provide any reliable evidence of a widespread problem.



Widespread problem? Most people do not run large speakers these days. Most people run "small" 2 or 3 way speakers with limited FR. In addition, most people set their AVR to small speakers, so they do not run their amplifiers full range. I make no claim on how adequate any AVR amplifier stages and power supplies are these days. You may claim that you can run full range speakers with most every AVR, but that is just your claim!

Interesting approach. If responding logically is too hard, just miss the entire point of the post which is that widespread current limiting and poorly designed output stages are a prerequisite for passive biamping making a significant difference.
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post #455 of 651 Old 04-11-2014, 12:01 PM
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Quote:
Originally Posted by FMW View Post

Quote:
Originally Posted by J_Palmer_Cass View Post

That is called passive bi-amping!

No, I'm talking about active biamplification with the crossover in front of the amplifier. But at this point I think I'll check out of this thread. I'm obviously not doing any good.



You should not cascade electronic crossovers with passive crossovers. You have to move the electronic crossover out of the way and let the passive filters dominate.
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post #456 of 651 Old 04-11-2014, 12:08 PM
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So what? As I have detailed in other posts, those weren't the only controls that we used.
There were none documented in the article Arny. Why? Seems like you believe in controls yet there is not one word about them in the article. The one and only test that has ever been documented to include you is missing this critical ingrediant.
Quote:
Besides, the above post is again demonizing ABX for problems that it shares with many other forms of subjective testing.
I said nothing about ABX being a bad thing. I pointed out serious issues with the people using it. I showed specific examples of flaws in testing that your proposed controls would not have caught. So beside the problems, we lack awareness of what a control really is in this context.
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ABX doesn't have to be perfect, it merely needs to be appreciably better. Since the most common equipment evaluation technique to this day is the not level matched, not time-synched, sighted evaluation, its hard to imagine why anybody keeps picking nits with ABX.
No test is perfect so we are good on that smile.gif. Not having said a word about other comparisons, not sure how they became the metric of comparison. I have not advocated such tests as a substitute. But rather, stating that you are protocol errors in your testing and the rules that you stipulate did not include a control. Fact that other people do bad tests doesn't excuse you and I from practicing the same.

And there are countless tests being run everyday that are proper but not ABX such as codecs which routinely have controls. Here is a random comparison that came up in my first search results:

test_ebu_48.gif

Look on the very right. The worse scoring one (3.5 KHz LPF) is the control. It is a low pass filtered version of the original song that should present clear degradation. If that track had garnered higher praise, we would know something needed investigating.

Now look at your article. There is no such control. We don't know if any mistakes were made.
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I don't know about you, but I have long known that nothing is totally idiot-proof. Often the idiot is me! ;-)
Same here smile.gif. For this reason, I would rely on people who are far more careful than me to construct serious tests. When I published the results of my speaker wire testing, I tested and retested until I built up high confidence in not having made mistakes.

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post #457 of 651 Old 04-11-2014, 12:09 PM
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Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by J_Palmer_Cass View Post

Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by J_Palmer_Cass View Post

Quote:
Originally Posted by FMW View Post

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Originally Posted by J_Palmer_Cass View Post

Yes, but you did not mention what happens when you passive bi-amp the speaker / amplifier in question. Will the speaker receive more current with a passive bi-amp setup as compared with a straight AVR setup? .

No. current is limited by the power supply.


Read!

http://en.wikipedia.org/wiki/Clipping_(audio)

Did you check the article out before you blithely recommended it?

Here are the items in that could be relevant to an AVRs amplifier:
Quote:
"(1) The peak-to-peak of a solid-state transformerless amplifier (most integrated circuit and discrete solid state circuits) is limited to the power supply voltage less a small amount that depends on the design of the circuit (especially the driver configuration) and the saturation voltage (Vce(sat) for bipolar transistors, or Rds(on) for Field Effect Transistors)..."

The above is about a limit that is enforced by the power supply.
Quote:
"(2) If the power supply capacitor is no longer able to keep the voltage "flat" due to a massive current draw, the positive and negative voltage supply of the amplifier will fluctuate resulting in sort of a clipped signal that contains some AC line frequency harmonics."

The above is about a limit that is enforced by the power supply.
Quote:
"(3) An amplifier can limit the current output, or the input voltage, for a variety of reasons both intentional or not. Intentional limiting circuits would not be expected to come into effect in normal operation, but when the output load resistance is too low or the system is connected to an exceptionally high signal level, for example. The result of this form of clipping might not create a flat top to the Voltage waveform, but rather a flat top to the current waveform."

The above clearly says that current limiting in the output stage "Would not be expected to come into effect in normal operation." That means that it is not a problem with a properly designed output stage. I agree that there are a minority of AVR output stages that are marginal in this department, but to say that Passive Biamping is anything but a niche solution would require evidence that a high percentage of AVR output stages are poorly designed. That's a tall assertion that nobody should agree with just because someone said so and didn't provide any reliable evidence of a widespread problem.



Widespread problem? Most people do not run large speakers these days. Most people run "small" 2 or 3 way speakers with limited FR. In addition, most people set their AVR to small speakers, so they do not run their amplifiers full range. I make no claim on how adequate any AVR amplifier stages and power supplies are these days. You may claim that you can run full range speakers with most every AVR, but that is just your claim!

Interesting approach. If responding logically is too hard, just miss the entire point of the post which is that widespread current limiting and poorly designed output stages are a prerequisite for passive biamping making a significant difference.



So what you are saying is the power amplifier stage in a $300 AVR is just as good as the power amplifier stage in a $1300 AVR? More power means the same current output capability but more voltage output?

One common method of increasing the current capability of a power amplifier is simply doubling the number of output transistors in the output stage (parallel transistors). Better power amplifiers use more output transistors in the circuits so they can drive low impedance loads.
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post #458 of 651 Old 04-11-2014, 12:42 PM
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Originally Posted by J_Palmer_Cass View Post

You should not cascade electronic crossovers with passive crossovers. You have to move the electronic crossover out of the way and let the passive filters dominate.

Whatever you say. You're the expert.
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post #459 of 651 Old 04-11-2014, 12:57 PM
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Quote:
Originally Posted by FMW View Post

Quote:
Originally Posted by J_Palmer_Cass View Post

You should not cascade electronic crossovers with passive crossovers. You have to move the electronic crossover out of the way and let the passive filters dominate.

Whatever you say. You're the expert.


The person who designed the speaker was my original source of that information.

A newer generation of the speaker is the NHT Evolution. They can be run active or passive (AKA no HP filter) depending on the user. The crossover can be modified to bring the FR down to 20 Hz.


http://www.stereophile.com/content/nht-evolution-t6-loudspeaker-system-postscript-may-2005
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post #460 of 651 Old 04-11-2014, 01:58 PM
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Originally Posted by J_Palmer_Cass View Post


So what you are saying is the power amplifier stage in a $300 AVR is just as good as the power amplifier stage in a $1300 AVR?

Depends what your criteria is. If sound quality is your only criteria then far more likely as not they are all the same.

In some cases the cheap ones may measure better than the expensive ones:

For example:

http://www.soundandvision.com/content/yamaha-rx-v371-av-receiver-ht-labs-measures



Versus

http://www.soundandvision.com/content/yamaha-rx-v475-av-receiver-ht-labs-measures



At most power levels below 35 watts where most people listen most of the time, the cheaper amp measures better, right? The THD isn't enough to be audible with either amp, but as usual they measure differently.
Quote:
More power means the same current output capability but more voltage output?

The important thing is that the current capability needs to scale up proportional to the voltage capability. However, both of those things, especially current sourcing ability are not on most spec sheets.

Here's what a complete current/voltage measurement for a power looks like:

http://www.audiograph.se/Downloads/PowerCube_12p_brochure_complete.pdf



Its a surface, not a number!

The machine that makes this is a commercial product, but I'll bet money that not a lot of them have been sold to audio manufacturers.
Quote:
One common method of increasing the current capability of a power amplifier is simply doubling the number of output transistors in the output stage (parallel transistors). Better power amplifiers use more output transistors in the circuits so they can drive low impedance loads.

Not exactly.

The first question is where is the limit? It could be the power supply or it could be the output stage.

The most common method of increasing the current capability of a power amplifier output stage is simply picking output devices with more current handling capacity. The basic current spec of output transistors is given as a single number (DC, minimal voltage across the transistor), and a graph. The graph is current versus voltage across the device with several lines for different time durations This graph describes what is called Safe Operating Area or SOA.

SOA has increased by a factor of 3-5 times over the life of the application of silicon output transistors to audio power amps.

Usually SOA is the weakest link. It can be increased for the amplifier as a whole with the same output devices (OPTs) by either paralleling the OPTs or hooking them in series. There are two ways of hooking them in series, one with one power supply and one with two or more power supplies. Amps like the Berhinger EP2500/4000 do the latter.
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post #461 of 651 Old 04-11-2014, 02:14 PM
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After an extended series of digging and subtle revelations by JPC, it is obvious tht his Sony/NHT components were setup in a passive bi-amp configuration. The caper was solved entirely when Cass wrote:

<<I used a pair of NHT MA-1A subwoofer amplifiers for the test (one per 10 " subwoofer). I ran SPEAKER LEVEL signal to the MA-1A and set the LP filter to max (about 180 Hz). I ran the upper drivers of the 2.9 direct from the Sony AVR.>>

Using a seperate amp for the woofer with the Sony AVR in bi-amp mode is not an active bi-amp setup because the entire frequency band is still output to the Sony's front channel amps and filtered by the speaker's crossover. With 'speaker level' connectivity to the NHT amp, the Sony still sends a full band signal to its rear channel amps. While its true that the NHT filters the signal before it arrives at the speaker, the speakers 100Hz low pass filter is still robbing power as passive crossovers do.

The optimal setup would have involved removal of the speaker's 10 inch woofer low pass filter, and use of RCA line level connectivity between the Sony AVR's rear channel L/R pre-amp output and each of the NHT monos. The NHT amp crossovers would be set at 100-120Hz.

http://www.nhthifi.com/site/pdf/MA_1Manual.pdf

Though the remainder of the speaker would still be passively bi-amped, this setup might have yielded some benefit of an actively bi-amped system... In theory. The NHT amp is rated 80watts. What is the Receiver's power rating? Were the claimed benefits a result of increasing the NHT amp gain? Or off-loading from the Sony's power supply? Or both?
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post #462 of 651 Old 04-11-2014, 02:15 PM
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That is not active bi-amping by AVS standards. You are required to (by AVS standards) remove the passive filters in the speaker crossover to be considered active bi-amping.

There is no generally agreed-upon AVS standard. What you are referring to is someone's guideline. It is not cast in cement. It is not blessed by a priest. The requisite chicken was not slaughtered. ;-)
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In addition, the Sony receiver in question does not have preamp level outputs except for the subwoofer output jack so your so called active bi-amping is a no go.

Not exactly. The most important active filtering in the SA3 are the same as those used in the subwoofer side of many AVr's bass management circuits.

There is no rule that cascading active and passive crossovers is always a bad thing. It can work out. For example the classic Linkwitz-Riley 24/dB crossover is two second order Butterworth filters in series for each driver. Matters not whether the filters are mixed or matched or even composed of the inherent roll-offs of the drivers. I've seen all permutations used, tried most of them myself, and they can all work.

Furthermore, I looked up the schematic of the amp in some Sony receiver, and it was p!$$-poor - it looks to me like Sony sleezed off on the output stage, especially the OPT transistors. Remember there are AVRs out there that have paralleled output transistors and the transistors themsevels are stout, not the wimps specified by Sony for this one.

Face it, in a game that most people can win with no special thoughts of their own, you lost! That is not a reason to make up a global rule that passive biamping can work often enough to be a good recommendation.
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post #463 of 651 Old 04-11-2014, 02:19 PM
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Originally Posted by UndersAVS View Post

After an extended series of digging and subtle revelations by JPC, it is obvious tht his Sony/NHT components were setup in a passive bi-amp configuration. The caper was solved entirely when Cass wrote:

<<I used a pair of NHT MA-1A subwoofer amplifiers for the test (one per 10 " subwoofer). I ran SPEAKER LEVEL signal to the MA-1A and set the LP filter to max (about 180 Hz). I ran the upper drivers of the 2.9 direct from the Sony AVR.>>

Using a seperate amp for the woofer with the Sony AVR in bi-amp mode is not an active bi-amp setup because the entire frequency band is still output to the Sony's front channel amps and filtered by the speaker's crossover. With 'speaker level' connectivity to the NHT amp, the Sony still sends a full band signal to its rear channel amps. While its true that the NHT filters the signal before it arrives at the speaker, the speakers 100Hz low pass filter is still robbing power as passive crossovers do.

The optimal setup would have involved removal of the speaker's 10 inch woofer low pass filter, and use of RCA line level connectivity between the Sony AVR's rear channel L/R pre-amp output and each of the NHT monos. The NHT amp crossovers would be set at 100-120Hz.

http://www.nhthifi.com/site/pdf/MA_1Manual.pdf

Though the remainder of the speaker would still be passively bi-amped, this setup might have yielded some benefit of an actively bi-amped system... In theory. The NHT amp is rated 80watts. What is the Receiver's power rating? Were the claimed benefits a result of increasing the NHT amp gain? Or off-loading from the Sony's power supply? Or both?

Since the evaluation of the consequences of the alleged upgrade was a non level-matched, not time-synched, not quick switched, sighted evaluation IMO it really isn't worth a second thought to explain. He wished for a better sounding system and he got one! Magic! ;-)
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post #464 of 651 Old 04-11-2014, 02:34 PM
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Originally Posted by arnyk View Post

Since the evaluation of the consequences of the alleged upgrade was a non level-matched, not time-synched, not quick switched, sighted evaluation IMO it really isn't worth a second thought to explain. He wished for a better sounding system and he got one! Magic! ;-)

Not really. If I remember correctly, he dumped the setup because of component clutter... Apparently, any perceived or real ear measured improvements weren't ALL THAT GREAT! ;D
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post #465 of 651 Old 04-11-2014, 02:45 PM
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Originally Posted by arnyk View Post

There is no rule that cascading active and passive crossovers is always a bad thing. It can work out. For example the classic Linkwitz-Riley 24/dB crossover is two second order Butterworth filters in series for each driver. Matters not whether the filters are mixed or matched or even composed of the inherent roll-offs of the drivers. I've seen all permutations used, tried most of them myself, and they can all work.
Nuts. I was about to post almost the same thing. You could do it, but why you'd really want to I don't know. It would maybe make an interesting College assignment for the instruction but as FMW mentioned, amateurs should not attempt it.
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post #466 of 651 Old 04-11-2014, 03:28 PM
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Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by J_Palmer_Cass View Post


So what you are saying is the power amplifier stage in a $300 AVR is just as good as the power amplifier stage in a $1300 AVR?

Depends what your criteria is. If sound quality is your only criteria then far more likely as not they are all the same.

In some cases the cheap ones may measure better than the expensive ones:

For example:

http://www.soundandvision.com/content/yamaha-rx-v371-av-receiver-ht-labs-measures



Versus

http://www.soundandvision.com/content/yamaha-rx-v475-av-receiver-ht-labs-measures



At most power levels below 35 watts where most people listen most of the time, the cheaper amp measures better, right? The THD isn't enough to be audible with either amp, but as usual they measure differently.
Quote:
More power means the same current output capability but more voltage output?

The important thing is that the current capability needs to scale up proportional to the voltage capability. However, both of those things, especially current sourcing ability are not on most spec sheets.

Here's what a complete current/voltage measurement for a power looks like:

http://www.audiograph.se/Downloads/PowerCube_12p_brochure_complete.pdf



Its a surface, not a number!

The machine that makes this is a commercial product, but I'll bet money that not a lot of them have been sold to audio manufacturers.
Quote:
One common method of increasing the current capability of a power amplifier is simply doubling the number of output transistors in the output stage (parallel transistors). Better power amplifiers use more output transistors in the circuits so they can drive low impedance loads.

Not exactly.

The first question is where is the limit? It could be the power supply or it could be the output stage.

The most common method of increasing the current capability of a power amplifier output stage is simply picking output devices with more current handling capacity. The basic current spec of output transistors is given as a single number (DC, minimal voltage across the transistor), and a graph. The graph is current versus voltage across the device with several lines for different time durations This graph describes what is called Safe Operating Area or SOA.

SOA has increased by a factor of 3-5 times over the life of the application of silicon output transistors to audio power amps.

Usually SOA is the weakest link. It can be increased for the amplifier as a whole with the same output devices (OPTs) by either paralleling the OPTs or hooking them in series. There are two ways of hooking them in series, one with one power supply and one with two or more power supplies. Amps like the Berhinger EP2500/4000 do the latter.



Various Yamaha AVR speaker impedance notations: When connect to less than 8 Ohm speakers, yada, yada, yada.

You have to get up to the higher priced units to get a 4 ohm rating, and that only applies to the main speakers.








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post #467 of 651 Old 04-11-2014, 03:33 PM
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Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by UndersAVS View Post

After an extended series of digging and subtle revelations by JPC, it is obvious tht his Sony/NHT components were setup in a passive bi-amp configuration. The caper was solved entirely when Cass wrote:

<<I used a pair of NHT MA-1A subwoofer amplifiers for the test (one per 10 " subwoofer). I ran SPEAKER LEVEL signal to the MA-1A and set the LP filter to max (about 180 Hz). I ran the upper drivers of the 2.9 direct from the Sony AVR.>>

Using a seperate amp for the woofer with the Sony AVR in bi-amp mode is not an active bi-amp setup because the entire frequency band is still output to the Sony's front channel amps and filtered by the speaker's crossover. With 'speaker level' connectivity to the NHT amp, the Sony still sends a full band signal to its rear channel amps. While its true that the NHT filters the signal before it arrives at the speaker, the speakers 100Hz low pass filter is still robbing power as passive crossovers do.

The optimal setup would have involved removal of the speaker's 10 inch woofer low pass filter, and use of RCA line level connectivity between the Sony AVR's rear channel L/R pre-amp output and each of the NHT monos. The NHT amp crossovers would be set at 100-120Hz.

http://www.nhthifi.com/site/pdf/MA_1Manual.pdf

Though the remainder of the speaker would still be passively bi-amped, this setup might have yielded some benefit of an actively bi-amped system... In theory. The NHT amp is rated 80watts. What is the Receiver's power rating? Were the claimed benefits a result of increasing the NHT amp gain? Or off-loading from the Sony's power supply? Or both?

Since the evaluation of the consequences of the alleged upgrade was a non level-matched, not time-synched, not quick switched, sighted evaluation IMO it really isn't worth a second thought to explain. He wished for a better sounding system and he got one! Magic! ;-)


While that is accurate, with the passive bi-amp setup I could push the volume up louder than I could stand it.

The straight AVR to speaker ran out of gas at a much lower SPL level. The speaker sounded like there was a compressor in line. Turn up the volume control and volume level did not increase.
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Since the evaluation of the consequences of the alleged upgrade was a non level-matched, not time-synched, not quick switched, sighted evaluation IMO it really isn't worth a second thought to explain. He wished for a better sounding system and he got one! Magic! ;-)

Not really. If I remember correctly, he dumped the setup because of component clutter... Apparently, any perceived or real ear measured improvements weren't ALL THAT GREAT! ;D


Not correct. That test just proved that passive bi-amping did work with those specific speakers and that specific AVR. I did not spend an additional penny to run those tests.

There was really no clutter. If you want to see clutter, just look around AVS. I simply bought a 4 ohm rated receiver used (STR-DA4ES). On top of that, the speakers are not even used for HT these days. They are just used as PC speakers these days.

If I were to use the NHT 2.9s in a HT setting, I would most likely just use an NHT A-1 amplifier to run each speakers full range. I did not own that power amplifier years ago when I ran that test.



http://www.nhthifi.com/ServiceCenter/A1-Mono-Amplifier-vintage-nht


"Product Information
The A-1 is a workhorse amplifier designed for a number of applications. It is a full range amplifier useful for powering subwoofers, bi-amping large speakers or used in conjunction with a good preamp. FR: 20Hz – 20kHz. Power Rating: 250W (6 ohms). DIM/WT: 2.25”H x 17”W x 11”D, 18 lbs."
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That is not active bi-amping by AVS standards. You are required to (by AVS standards) remove the passive filters in the speaker crossover to be considered active bi-amping.

There is no generally agreed-upon AVS standard. What you are referring to is someone's guideline. It is not cast in cement. It is not blessed by a priest. The requisite chicken was not slaughtered. ;-)
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In addition, the Sony receiver in question does not have preamp level outputs except for the subwoofer output jack so your so called active bi-amping is a no go.

Not exactly. The most important active filtering in the SA3 are the same as those used in the subwoofer side of many AVr's bass management circuits.

There is no rule that cascading active and passive crossovers is always a bad thing. It can work out. For example the classic Linkwitz-Riley 24/dB crossover is two second order Butterworth filters in series for each driver. Matters not whether the filters are mixed or matched or even composed of the inherent roll-offs of the drivers. I've seen all permutations used, tried most of them myself, and they can all work.

Furthermore, I looked up the schematic of the amp in some Sony receiver, and it was p!$$-poor - it looks to me like Sony sleezed off on the output stage, especially the OPT transistors. Remember there are AVRs out there that have paralleled output transistors and the transistors themsevels are stout, not the wimps specified by Sony for this one.

Face it, in a game that most people can win with no special thoughts of their own, you lost! That is not a reason to make up a global rule that passive biamping can work often enough to be a good recommendation.


Are you Red Foreman's son? I made up no global rule about anything. Your global rule that passive bi-amping never works is not valid!


Here is the schematic for the SA-3 (which I do not own). Multiple parallel transistor output stage.

http://www.nhthifi.com/core/media/media.nl?id=7523&c=408900&h=7f9dc1bb62d98a15728e&whence=
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Only if the amp clips at a SPL that is below my preferences. My preferences are for listening at levels that are below 95 dB peak, and that's well below clipping for my AVR.
How did you figure out the peak SPL Arny?

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Only if the amp clips at a SPL that is below my preferences. My preferences are for listening at levels that are below 95 dB peak, and that's well below clipping for my AVR.
How did you figure out the peak SPL Arny?

Measured it with a peak reading/peak holding SPL meter.
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Here is the schematic for the SA-3 (which I do not own). Multiple parallel transistor output stage.

http://www.nhthifi.com/core/media/media.nl?id=7523&c=408900&h=7f9dc1bb62d98a15728e&whence=

That was just 2 small TO220 transistors in parallel.




Here's something a little more serious (Behringer EP2500/4000):



4 in parallel, and they are monsters:

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Originally Posted by arnyk View Post

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Originally Posted by UndersAVS View Post

After an extended series of digging and subtle revelations by JPC, it is obvious tht his Sony/NHT components were setup in a passive bi-amp configuration. The caper was solved entirely when Cass wrote:

<<I used a pair of NHT MA-1A subwoofer amplifiers for the test (one per 10 " subwoofer). I ran SPEAKER LEVEL signal to the MA-1A and set the LP filter to max (about 180 Hz). I ran the upper drivers of the 2.9 direct from the Sony AVR.>>

Using a seperate amp for the woofer with the Sony AVR in bi-amp mode is not an active bi-amp setup because the entire frequency band is still output to the Sony's front channel amps and filtered by the speaker's crossover. With 'speaker level' connectivity to the NHT amp, the Sony still sends a full band signal to its rear channel amps. While its true that the NHT filters the signal before it arrives at the speaker, the speakers 100Hz low pass filter is still robbing power as passive crossovers do.

The optimal setup would have involved removal of the speaker's 10 inch woofer low pass filter, and use of RCA line level connectivity between the Sony AVR's rear channel L/R pre-amp output and each of the NHT monos. The NHT amp crossovers would be set at 100-120Hz.

http://www.nhthifi.com/site/pdf/MA_1Manual.pdf

Though the remainder of the speaker would still be passively bi-amped, this setup might have yielded some benefit of an actively bi-amped system... In theory. The NHT amp is rated 80watts. What is the Receiver's power rating? Were the claimed benefits a result of increasing the NHT amp gain? Or off-loading from the Sony's power supply? Or both?

Since the evaluation of the consequences of the alleged upgrade was a non level-matched, not time-synched, not quick switched, sighted evaluation IMO it really isn't worth a second thought to explain. He wished for a better sounding system and he got one! Magic! ;-)


While that is accurate, with the passive bi-amp setup I could push the volume up louder than I could stand it.

The straight AVR to speaker ran out of gas at a much lower SPL level. The speaker sounded like there was a compressor in line. Turn up the volume control and volume level did not increase.

OK, so the AVR ran out of gain because of suboptimal internal trim settings.

The above does not describe what a clipping amp sounds like. A clipping amp continues to get louder as you turn up the volume because the average levels increase even though the peaks get chopped.

And without actual SPL meter readings, its all a big mystery!
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Here is the schematic for the SA-3 (which I do not own). Multiple parallel transistor output stage.

http://www.nhthifi.com/core/media/media.nl?id=7523&c=408900&h=7f9dc1bb62d98a15728e&whence=

That was just 2 small TO220 transistors in parallel.




Here's something a little more serious (Behringer EP2500/4000):



4 in parallel, and they are monsters:






No surprise there. The Behringer is rated down to 2 Ohms, so the 4 parallel transistors in the output stage allows for more output current. The output transistors also require a higher voltage rating due to the 2000 watt 2 ohm stereo rating of the amplifier.

An AVR can not compete with an outboard amplfier.
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Quote:
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Originally Posted by J_Palmer_Cass View Post

Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by UndersAVS View Post

After an extended series of digging and subtle revelations by JPC, it is obvious tht his Sony/NHT components were setup in a passive bi-amp configuration. The caper was solved entirely when Cass wrote:

<<I used a pair of NHT MA-1A subwoofer amplifiers for the test (one per 10 " subwoofer). I ran SPEAKER LEVEL signal to the MA-1A and set the LP filter to max (about 180 Hz). I ran the upper drivers of the 2.9 direct from the Sony AVR.>>

Using a seperate amp for the woofer with the Sony AVR in bi-amp mode is not an active bi-amp setup because the entire frequency band is still output to the Sony's front channel amps and filtered by the speaker's crossover. With 'speaker level' connectivity to the NHT amp, the Sony still sends a full band signal to its rear channel amps. While its true that the NHT filters the signal before it arrives at the speaker, the speakers 100Hz low pass filter is still robbing power as passive crossovers do.

The optimal setup would have involved removal of the speaker's 10 inch woofer low pass filter, and use of RCA line level connectivity between the Sony AVR's rear channel L/R pre-amp output and each of the NHT monos. The NHT amp crossovers would be set at 100-120Hz.

http://www.nhthifi.com/site/pdf/MA_1Manual.pdf

Though the remainder of the speaker would still be passively bi-amped, this setup might have yielded some benefit of an actively bi-amped system... In theory. The NHT amp is rated 80watts. What is the Receiver's power rating? Were the claimed benefits a result of increasing the NHT amp gain? Or off-loading from the Sony's power supply? Or both?

Since the evaluation of the consequences of the alleged upgrade was a non level-matched, not time-synched, not quick switched, sighted evaluation IMO it really isn't worth a second thought to explain. He wished for a better sounding system and he got one! Magic! ;-)


While that is accurate, with the passive bi-amp setup I could push the volume up louder than I could stand it.

The straight AVR to speaker ran out of gas at a much lower SPL level. The speaker sounded like there was a compressor in line. Turn up the volume control and volume level did not increase.

OK, so the AVR ran out of gain because of suboptimal internal trim settings.

The above does not describe what a clipping amp sounds like. A clipping amp continues to get louder as you turn up the volume because the average levels increase even though the peaks get chopped.

And without actual SPL meter readings, its all a big mystery!



Current clipping is not the same thing as voltage clipping. You do not gain any output voltage with a passive bi-amp setup, but you do gain output current. Sort of like current gain by use of parallel output transistors through a different route.

The STR-DE985 ran out of current until the NHT 2.9 speaker was bi-amped in a passive manner. NHT 2.1 speakers ( 3-way 8 ohm) had no problem being driven by the same AVR.
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Originally Posted by J_Palmer_Cass View Post

Quote:
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Quote:
Originally Posted by J_Palmer_Cass View Post



Here is the schematic for the SA-3 (which I do not own). Multiple parallel transistor output stage.

http://www.nhthifi.com/core/media/media.nl?id=7523&c=408900&h=7f9dc1bb62d98a15728e&whence=

That was just 2 small TO220 transistors in parallel.




Here's something a little more serious (Behringer EP2500/4000):



4 in parallel, and they are monsters:





No surprise there. The Behringer is rated down to 2 Ohms, so the 4 parallel transistors in the output stage allows for more output current. The output transistors also require a higher voltage rating due to the 2000 watt 2 ohm stereo rating of the amplifier.

An AVR can not compete with an outboard amplfier.

An AVR was not part of the above comparison. This is a comparison between a NHT subwoofer amplifer and another power amplifier. The SA3 ran about $400 about the same price as the Behringer.

However some Onkyo AVRs use 2 paralleled output transistors up and down for each of the 7 or more amplifiers inside.
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post #478 of 651 Old 04-12-2014, 04:55 AM
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Originally Posted by J_Palmer_Cass View Post

Quote:
Originally Posted by arnyk View Post

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Originally Posted by J_Palmer_Cass View Post



Here is the schematic for the SA-3 (which I do not own). Multiple parallel transistor output stage.

http://www.nhthifi.com/core/media/media.nl?id=7523&c=408900&h=7f9dc1bb62d98a15728e&whence=

That was just 2 small TO220 transistors in parallel.




Here's something a little more serious (Behringer EP2500/4000):



4 in parallel, and they are monsters:





No surprise there. The Behringer is rated down to 2 Ohms, so the 4 parallel transistors in the output stage allows for more output current. The output transistors also require a higher voltage rating due to the 2000 watt 2 ohm stereo rating of the amplifier.

An AVR can not compete with an outboard amplfier.

An AVR was not part of the above comparison. This is a comparison between a NHT subwoofer amplifer and another power amplifier. The SA3 ran about $400 about the same price as the Behringer.

However some Onkyo AVRs use 2 paralleled output transistors up and down for each of the 7 or more amplifiers inside.


AVRs do not have what is classified on AVS as a "quality amplifer"!

Those Onkyo AVR's are probably rated for 4 ohms. What price range are they in?

Do you have a schematic for the Sony STR-DE985 output stage?
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AVRs do not have what is classified on AVS as a "quality amplifer"!

Based on what reliable evidence?
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Those Onkyo AVR's are probably rated for 4 ohms. What price range are they in?

If memory serves, just over $1K.
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Do you have a schematic for the Sony STR-DE985 output stage?



It is a little better than the last Sony I looked at...

The OPT SOA is:



I have the entire service manual. I believe that it is freely downloadable from here:

http://elektrotanya.com

Just for comparison here is the schematic of the power amp of an low-mid Denon AVR power amp:



and here is the SOA of its OPT devices:

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post #480 of 651 Old 04-12-2014, 06:46 AM
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Yup, a $1000 AVR is better than a $300 AVR.


I replaced the STR-DE985 with a STR-DA-4ES AVR (EBAY USED). Both are vintage 2002 model year.

Weight 21 pounds as compared with 44 pounds.

Price around $350 as compared to around $1,200 (2002 dollars)

Speaker impedance rating 8-16 ohms as compared with 4 - 16 ohms.



https://docs.sony.com/release/specs/STRDE985spec.pdf


https://docs.sony.com/release/specs/STRDA4ESspec.pdf
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