Pioneer SC-07 and 4 ohm speakers

[kerrbust]

Hey guys

I am ready to make a huge investment in a home theater after a lot of research. This week end I was all set to make the purchase of:

Pioneer Pro 151 FD 60" Kuro
Pioneer Sc-07 receiver
Pioneer 05 Blue Ray

Kind of a dream system for me. I have a Martin Logan Fresco-center and a pair of Mosaic's for the fronts. They are not electrostaics but they are ATF. They are also 5 ohm speakers. So I thought I would call Pioneer tech guys, they told me if I was going to run the speakers cranked up I could damage the amplifier because the system is not rated for 5 ohm speakers. I downloaded the brochure off the Pioneer website and on the picture of the back of the reciever next to the speaker hook ups it says warning Impeadance 6-16 ohms. I am freaked a little bit here so looking for some advise. Is it really possible that I would damage the amp or is that just the party line from Pioneer? I am sure that I am not the only guy with less than 8 ohm speakers. I really want this system since I have gone back and forth about what to buy for about a month and half now. Kinda making myself nuts about getting the right stuff from all the choices out there and now this comes up at the last minute!! Any advise would be valued.

kerrbust

 

[Thunder18]

I envy you, that SC-07 seems like just what I want. Anyway, if you're really worried about it, you might look at a pair of these:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-812
They are believed to be the same as the Emotiva BPA-1's and deliver 75 Watts x 2 into 4 Ohms. Are the Martin Logan's Bi-ampable? Perhaps you could even bi-amp them using a combination of these and the Pioneer's amp section. Some speakers present a higher impedence rating when bi-amped.

 

[Seth=L]

THX Ultra II standards state an amplifier must be able to drive speakers at 4 ohms loads (around 3.6 ohms if I recal correctly) at reference levels of output in a large room. The SC-07 should be better equipped to handle those speakers than many budget home amplifiers. I would expect it to certainly outperform the Emotiva BPA-1s (which are no longer in production, they may be replacing them with something better hopefully).

I think you will be very safe and satisfied with that arrangement.

 

[Thunder18]

THX Ultra II standards state an amplifier must be able to drive speakers at 4 ohms loads (around 3.6 ohms if I recal correctly) at reference levels of output in a large room. The SC-07 should be better equipped to handle those speakers than many budget home amplifiers. I would expect it to certainly outperform the Emotiva BPA-1s (which are no longer in production, they may be replacing them with something better hopefully).

I think you will be very safe and satisfied with that arrangement.

Very enlightening info there.

 

[TLS Guy]

THX Ultra II standards state an amplifier must be able to drive speakers at 4 ohms loads (around 3.6 ohms if I recal correctly) at reference levels of output in a large room. The SC-07 should be better equipped to handle those speakers than many budget home amplifiers. I would expect it to certainly outperform the Emotiva BPA-1s (which are no longer in production, they may be replacing them with something better hopefully).

I think you will be very safe and satisfied with that arrangement.

We are heading into new territory here.

This receiver uses class D ICE (Intelligent Compact Efficient) amps.

This highly efficient, almost 100%, topology of class D amps was developed by Karsten Nielsen for his PhD thesis he defended in 1999. This technology has been developed by B & O who bought out Nielsen's share in July of this year.

B & O have licensed this technology to among others, Samsung for mobile phones and Sanyo for the development of dual channel output MOSFET switching amp chips, which appeared in 2004.

B & O have produced high end amps for among others ROTEL and Jeff Rowland.

The Sanyo chip has been embraced by the car audio amp manufacturers. Obviously amp efficiency is a big concern to them.

Now one of the problems with class D amps has been a very narrow optimal impedance range over which they work optimally. So the use of this technology has been very attractive for speakers with active crossovers and the amp connected to the drive units directly. In this way the impedance is a known quantity. Car audio manufacturers and enthusiasts have for a long time embraced active crossovers and bi and triamping.

Now we have long suspected that the next wave of A/V receivers would embrace this technology and the Sanyo chips in particular. These produce virtually no heat, are very cheap, small and minimize power requirements and ancillary circuit components.

I think I would be correct to assume that this Pioneer receiver uses the Sanyo dual MOSFET chips.

Now this post has caused me to study the details of these dual channel chips.

The following chips are available, 100 watts X 2, 150 watts X 2 and 200 watts X2

I assume that this receiver uses the 150 watt per channel chips.

Now these chips are 4 ohm rated, however there is a snag.

The line voltage of these chips is 33 volts. This gives 150 watts per channel into 8 ohms. The power into 6 ohms is 180 watts, and the power into four ohms is 150 watts, but THD rises to a whopping 10%

Now the THD into 8 ohms at 130 watts is an excellent 0.05%. At 140 watts it is 0.09%

At 180 watts into 6 ohms, the THD is 1%

Pioneer do not state THD figures below 6 ohms. However the Sanyo spec sheet quotes 10% THD at full power, 150 watts into four ohms. I can not find a power curve, but I suspect that at lower powers distortion drops.

Now as part of the licensing agreement with Sanyo to use the chip, current limiting has to be provided. Obviously it must be, otherwise it would deliver 300 watts to a four ohm load, or try to, but could not without self destruction. Also there has to be power supply shut down if certain current limits are exceeded. This could certainly happen because of the fact that in all speakers current and voltage are out of phase, and depending on the phase angle, the current can be significantly higher than calculated by ohms law.

The ability of the Sanyo chip to work with the complex loads that loudspeakers present is an unknown quantity. However one can say it will not perform as well as a traditional amp that can double its power when going from an 8 to a 4 ohm load.

These types of amps, I believe will mandate the development of speakers with active rather than passive crossovers and an amp for each pass band. I think that will produce better results than we have now.

The jury is out about the ability of these class D chips to drive the huge variety of loads presented by speakers with passive crossovers. The feeling is that at the current state of the art they may well come up short.

 

[AcuDefTechGuy]

So the Denon 5308 and Yamaha Z11 both use a Class AB amp, but his Pioneer uses a Class D amp?

 

[bandphan]

So the Denon 5308 and Yamaha Z11 both use a Class AB amp, but his Pioneer uses a Class D amp?

Yes, with their top 3 models. Pioneer is a partner with B&O on the ICE projects.

 

[TLS Guy]

So the Denon 5308 and Yamaha Z11 both use a Class AB amp, but his Pioneer uses a Class D amp?

Yes, look at the specs. No specs quoted below six ohms, and I'm certain for the reasons I outlined.
I think as processing power increases, takes more space, budget and generates more heat, you can be certain more receiver manufacturers will be using those dirt cheap Sanyo chips. That will save them space, heat and cash.

 

[AcuDefTechGuy]

Yes, look at the specs. No specs quoted below six ohms, and I'm certain for the reasons I outlined.
I think as processing power increases, takes more space, budget and generates more heat, you can be certain more receiver manufacturers will be using those dirt cheap Sanyo chips. That will save them space, heat and cash.

So do you think the quality will go down in the effort to save money?

But this Pioneer is $7,000. If the Class D ICE amps are saving them money, why is Pioneer charging so much?

You can buy a Yamaha Z11 @ J&R for $3,700 and a Denon 5308 for $4,300 @ J&R, and most likely even lower prices once you ask the salesman for discount.

I can't wait for HTM or AH to actually test this Pioneer SC-07!

 

[TLS Guy]

So do you think the quality will go down in the effort to save money?

But this Pioneer is $7,000. If the Class D ICE amps are saving them money, why is Pioneer charging so much?

You can buy a Yamaha Z11 @ J&R for $3,700 and a Denon 5308 for $4,300 @ J&R, and most likely even lower prices once you ask the salesman for discount.

I can't wait for HTM or AH to actually test this Pioneer SC-07!

Yes, and look what you can get the Pioneer SC -07 for!

I will post more on this later, as I think we are now at a watershed in audio history. You will see what I have been trying to tell you over the past year actually makes sense!

 

[TLS Guy]

Yes, and look what you can get the Pioneer SC -07 for!

I will post more on this later, as I think we are now at a watershed in audio history. You will see what I have been trying to tell you over the past year actually makes sense!

There is nothing intrinsically wrong with these Sanyo chips, it is application, application and application.

What are the two big bottle necks to improved performance.

1). Passive crossovers.

2). Loudspeaker drivers

Just look at the passive crossovers pictures posted some members of commercial speakers. What do we see miserable chokes with far too small a gauge of wire, wound on small iron cores, and electrolytic caps! Impossible to get good sound after that.

Now a lot of the processing of these new Pioneer receivers is to correct for phase and time problems induced by crossovers. I'm highly skeptical you can do that from a distant microphone in the average room anyway.

I think you could make active crossovers, and good ones, for less than passive ones. Op amps are very cheap. You could also correct the above problems at the speaker, which is the right place.

Now these Sanyo chips could very cheaply and excellently power each driver.

I'm certain that if speaker manufacturers would make alliances with amp manufacturers, far superior speakers could now be made cheaper, and also with huge energy savings.

I think the biggest resistance is consumers who have put a bunch of speaker wire behind walls not in conduit, which was a dumb move.

We need to educate the public about the real gains in performance that would come from using the above approach.

Consumers need to educate themselves about all this and embrace the concept. I think it is a waste of time spending R & D trying to get class D amps to better handle speakers with passive crossovers. I vote firmly for junking the passive crossovers. The technology is here to do it now, with benefits to the consumer in improved performance and cost savings.

 

[Seth=L]

I think it's funny that just because TLS guy makes a lengthy post that cites several numerical figures that the average reader just instantly assumes he must know exactly what he is talking about.

I'm not going to assume that the Pioneer doesn't use the Sanyo mosfets, and I am also not going to assume that it does. If it does, what if it uses 4 Sanyo mosfets per channel? Would this increase it's impedance handling abilities?

I will look into the THX Ultra requirements later and come back with some solid information.

 

[Seth=L]

Consumers need to educate themselves about all this and embrace the concept. I think it is a waste of time spending R & D trying to get class D amps to better handle speakers with passive crossovers. I vote firmly for junking the passive crossovers. The technology is here to do it now, with benefits to the consumer in improved performance and cost savings.

Of course we are leagues away from perfecting active cross-overs that the average consumer can utilize effectively. I do agree with you that active cross-overs properly implemented offer fine tuning that will help achieve better sound assuming other factors such as room acoustics, drivers, and cabinet design/build are also utilized correctly for the use.

To be honest I never really took the time to read most of your posts, because they where too long. I am glad I am reading them now.

 

[bandphan]

Im pretty sure the amps in the pioneers are solid. Class D amps when measured the same way as a,b,ab ect produce somewhat false results in measuring distortion, "Clearly, new tests that are specifically designed with Class D operation and behavior in mind are needed if the test results are ever going to be relevant.

Reconsidering THD in a Class D Environment Analog amplifiers modulate power continuously in accordance with an analog input signal, and generate continuous wave (analog) outputs. Class D amplifiers generally rely on the principle of Pulse Width Modulation, and, by virtue of their use of switching power devices, generate outputs comprised of discrete quantitized samples. So, while both amplifiers perform the same general task, the ways they accomplish this are as different as the way LPs and CDs play back sound. As we know, LPs drag a stylus over plastic, and CDs read a digital signal with a light source.

Some of the traditional tests used to validate the performance of the venerable but ancient Class A and Class A/B amplifier architectures such as Total Harmonic Distortion plus Noise Floor (THD+N) will reveal some useful performance or sonic characteristics in a Class D amplifier. However, these tests were originally conceived to show known common limitations of the analog amplifiers of that era. At that time, audio distortion was primarily harmonic, and more importantly, dynamic range was limited (and defined) by the noise floor.

Digital switching amplifiers, by their very nature, provide a completely new set of strengths and weaknesses. For example, distortion may be harmonic or enharmonic in nature, due to interactions with the sampling rate. Amplifier jitter rejection can also be critical. On the other hand, dynamic range is rarely, if ever, limited by the virtually non-existent noise floor of a digital system, especially when the incoming audio signal is digital and therefore also virtually noiseless. To compound the issue, most audio test equipment was designed to test within the confines of analog amplification and an analog sound source, therefore, this equipment - by design and definition - must give inaccurate results when confronted with inaudible switching frequencies.

The most significant analog amplifier measurement has now become the least reliable and least significant measurement for a digital amplifier. Since the test equipment was designed before switching amplifier systems were conceived, THD+N readings may easily be unreliable or misleading. In other words, in the world of switching amplifiers, THD is at least not as relevant as other tests and at worst is totally irrelevant as a standard by which to evaluate the performance of a digital amplifier. In fact, most THD measurements of digital amplifiers are no more representative of sonic performance than wow and flutter measurements are of a CD player. A single arbitrary ‘harmonic’ distortion category by itself is meaningless in the context of digital amplification without additional and more appropriate tests, such as intermodulation distortion and spectral display. Designing a Class D amplifier solely for good THD test results does not mean it sounds good, let alone qualifies it as “audiophile”.

Dynamic Range: The Acid Test for Class D Amplifiers Dynamic range, or the ratio of the largest accurately amplified signal to the smallest, has never been more relevant than in today’s world of 16 to 24-bit digital audio sources. A wide dynamic range is what makes music sound live, and 3-dimensional. With analog amplifiers, the popular shorthand for this measurement has become the ratio of the onset of clipping to the noise floor. This is practical for Class A and Class A/B amplifiers because any signal below the noise floor is largely masked. This does not hold true for Class D amplifiers. Here, the noise floor is generally much lower than Class A/B amplifiers, as a result of the noise immunity of digital circuitry. This does not mean that the amplifier can actually reproduce signals near that noise floor because most digital amplifiers, in fact, cannot. It is a limitation inherent in the architecture itself.

The critical fact to bear in mind is that all Class D amplifiers have outputs that are comprised of discrete power increments, a notion that can more easily be thought of as resolution steps. When the definition of dynamic range is applied in the context of quantitized increments, the result is that dynamic range of a Class D amplifier is defined as the ratio of the smallest discrete power level the amplifier can accurately output to the largest. Given this clarity of understanding, the obvious question becomes: How do we determine the smallest output power level in a Class D amplifier? The answer can be seen in its linearity. The Key Is Testing for Linearity.
Because Class D amplifiers are fundamentally different than Class A and Class A/B amplifiers, different tests need to be conducted to show performance. For more meaningful predictors of a switching amplifier, dynamic range is the critical test in an arsenal of new tests aimed specifically at digital amplification, since it shows the amplifier’s ability to reproduce the full range of signals it receives. A simple and effective way to measure dynamic range in a Class D amplifier is by its linearity in actual operation. With this test, you can be assured that great performance in the lab will equate to great performance under real world operation."

 

[Adam]

Scott - not at all trying to critique your post. I was just curious and looked up the source for your quote, and I'm linking it here in case others are also curious. I hope that you don't mind.

Adam

 

[bandphan]

Scott - not at all trying to critique your post. I was just curious and looked up the source for your quote, and I'm linking it here in case others are also curious. I hope that you don't mind.

Adam

not at all... there are a complete set of white papers by Jim Shanahan, ill try to find them..

 

[TLS Guy]

I think it's funny that just because TLS guy makes a lengthy post that cites several numerical figures that the average reader just instantly assumes he must know exactly what he is talking about.

I'm not going to assume that the Pioneer doesn't use the Sanyo mosfets, and I am also not going to assume that it does. If it does, what if it uses 4 Sanyo mosfets per channel? Would this increase it's impedance handling abilities?

I will look into the THX Ultra requirements later and come back with some solid information.

These are not Sanyo Mosfets, but integrated circuits that contain dual channel Mosfet class D ice amps in each integrated circuit.

Now B & O have licensed this to to Samsung for low powered devices such as cell phones, and to Sanyo. The Sanyo tie up is for joint development.

Sanyo semiconductors are one of the worlds giant integrated circuit (chip) manufacturers. As far as I can tell these are the only licensees of ICE technology. Both B & O and Sanyo seem to keep some degree of control over companies using this ICE technology in audio products.

Pioneer are not integrated circuit manufacturers. The cost of designing, developing and bringing an integrated circuit to market is out of site, so large demand for the device has to be anticipated. My son Andrew is involved in the design, evaluation and the bringing of integrated circuits into production. So I have some significant insight as to what is involved and the nature of the integrated circuit industry.

I doubt it would not be possible to couple these integrated circuits together. Although the two amps in each chip appear to be bridgeable.

Now the origins of this revolutionary audio technology is, as is so often Europe.

This technology of using these amps in speakers with active crossovers is rapidly gaining ground in the studio monitor side of the industry over there.

The most favored modules for this purpose is by UcD Hypex based in the Netherlands. Here is an example of one of their modules for active speakers. In Europe there are also a number of others.

The technology of producing active crossovers is nothing new. This goes back over 50 years. To the consumer it is seamless. The consumer just plus his speaker into the preouts.

There seems to be consensus that the advantages of connecting these amps directly to speaker drive units is greater than for traditional amps, because of the problem of their difficulty with loads with widely fluctuating impedance.

I think we will see products like the receiver under question, will become pre/pros with the power amps an afterthought much like a phono input and FM section has become, so they will work in a pinch with non active powered speakers.

I'm certain that speakers with active crossovers and this new generation of amps could be built as cheaply or cheaper than speakers with passive crossovers. Properly sized chokes and the large poly caps required to produce a good passive crossovers are very costly. These components are now being widely undersized in much commercial product. These products could be brought to market quickly.

I think the principle barrier to the spread of this exciting new technology is going to be the consumer, and the backward thinking of wanting things done the way they always have been done. This technology represents an opportunity for change that will bring benefits to the consumer.

 

[bandphan]

http://www.icepower.bang-olufsen.com/en/company/history/

 

[bandphan]

also chips journey with the new model...http://www.avsforum.com/avs-vb/showthread.php?t=1057599

 

[Seth=L]

True to my word...

In 1999, THX launched THX Select, and renamed what had previously been called just THX to THX Ultra.

Whereas THX/THX Ultra was specified and designed for rooms "up to" 3000 ft3, THX Select took that requirement down to 2000 ft3. Both the requirements of the amplification and the output of the speakers were scaled back appropriately, placing THX in the hands of a whole new audience who could not have otherwise afforded it.

When it comes to amplification, continuous output tests are run on up to one, four, and five channels (simultaneously) of an Ultra product, but only one at a time on Select. With all products, the dynamic amplifier tests are done on up to all available channels. Ultra amplifiers must be stable on all channels to 3.2 ohms and swing an 18A peak, while Select products must be stable into 4 ohms (front channel) and 8 ohms (surrounds), and swing peaks of 12.5A and 6.2A respectively.

source:

http://www.hometheaterhifi.com/volume_13_1/feature-article-thx-1-2006-part-4.html