Audioholics Amplifier Measurement Testing Methodology

[bandphan]

Yeah, but a typical loudspeaker is probably more like an 8 ohm with the ocassional 6 ohm dip.

I'm more interested in knowing if an amp is going into shutdown trying to drive something like a magnepan IE not only low impedance but with occasional very low dips. THis is because I think most amps can in fact drive a typical 8 or 6 ohm speaker load and while 4 ohms continues is nice to see as well; it's the atypical loads that seem to create issues in the first place.

I wouldnt say that the typical loudspeaker is 8ohms, its all over the place. As for "very low" dips, that is dependent on where it occurs as to the current call. Martin Logan ELS pannels for example have become increasingly efficient, whereas in the past, especially Full Range, electrostatics where not only inefficient, phase angles seem to play just as big a role. The LSI series polk bookshelves dip into the high 2s and have strained many an AVR.

 

[3db]

Looking at NAD specs of their receivers:
http://nadelectronics.com/products/av-receivers/T-785-A/V-Surround-Sound-Receiver

They don't specify load impedance for their power measurements. I suspect their ratings are for 8 and 4 ohm loads with current limiting employed for the latter hence why their power ratings are the same under both load conditions.

You are correct. According to their spec sheet it's both 4/8 ohms:

http://nadelectronics.com/content/100419105830-NAD_T785-09MDC.pdf

 

[AcuDefTechGuy]

I have no doubt that Audioholics make the best amp measurements - the most comprehensive & real-world.

Life would be simple if Audioholics did measurements for every single amp out there, and people would not need to subscribe to Home Theater Mag (HTM) or S&V.

But I think HTM comes closest to Audioholics standards. HTM comes short for sure, but closer to Audioholics than S&V & most other reviews. Thus, I think it would be helpful if Audioholics could measure and publish both the "real-world" numbers and the "souped-up" numbers published by other magazines.

One example is the signal-to-noise ratio (SNR).

Audioholics do the unweighted SNR (real-world), whereas other people publish the A-wt SNR (souped-up). It would be helpful if Audioholics would publish both the unweighted SNR & the A-wt SNR.

HTM does measure @ 1 watt, but at 1kHz. I'm sure Audioholics can measure @ both 1kHz & from 20Hz-20kHz.

 

[M Code]

Looking at NAD specs of their receivers:
http://nadelectronics.com/products/av-receivers/T-785-A/V-Surround-Sound-Receiver

They don't specify load impedance for their power measurements. I suspect their ratings are for 8 and 4 ohm loads with current limiting employed for the latter hence why their power ratings are the same under both load conditions.

Gene...
Typically NAD amplifiers put out about 50% more power into 4 Ohms vs 8 Ohms. However the basic reason NAD only specs 4 Ohm power = to 8 Ohm power is that whatever 4 Ohm power they publish then the respective safety agency UL, CSA or CE will do their testing @ that spec.
And if they use the higher 4 Ohm power spec, all of their critical component temperature measurements will be done at the higher power spec and to pass the compliance standards would require bigger heat sinks, power transformers, power supply capacitors, bridge diodes...

In a higher priced component amplifier, the higher cost and heavy duty components are affordable but not in a broad distribution AVR..
They are simply too price sensitive to afford the added expense..

Just my $0.02...

 

[3db]

Gene...
Typically NAD amplifiers put out about 50% more power into 4 Ohms vs 8 Ohms. However the basic reason NAD only specs 4 Ohm power = to 8 Ohm power is that whatever 4 Ohm power they publish then the respective safety agency UL, CSA or CE will do their testing @ that spec.
And if they use the higher 4 Ohm power spec, all of their critical component temperature measurements will be done at the higher power spec and to pass the compliance standards would require bigger heat sinks, power transformers, power supply capacitors, bridge diodes...

In a higher priced component amplifier, the higher cost and heavy duty components are affordable but not in a broad distribution AVR..
They are simply too price sensitive to afford the added expense..

Just my $0.02...

Sounds plausable but its just a guess on your part. If you compare weights of NAD products to those of others like Onkyo Denon or Yamaha, you will notice that NADs run heavier do to their power supplies being more robust.

 

[M Code]

Sounds plausable but its just a guess on your part. If you compare weights of NAD products to those of others like Onkyo Denon or Yamaha, you will notice that NADs run heavier do to their power supplies being more robust.

Not really a guess..
Its what we do...

Just my $0.02..

 

[gene]

Sounds plausable but its just a guess on your part. If you compare weights of NAD products to those of others like Onkyo Denon or Yamaha, you will notice that NADs run heavier do to their power supplies being more robust.

not when looking at flagship products like the Denon AVR-5805 or Yamaha RX-Z11 The AVR-5805 to date IMO has the best amp section a receiver has ever seen!

 

[3db]

Not really a guess..
Its what we do...

Just my $0.02..

Who's we and what do "we do? . Nothing like being up front

Unless you are prepared to backup your claim with both thermal and electrical analysis, I'd say your talking out of the end of the body that kisses the porcelain doughnut. Just my $0.02

 

[3db]

not when looking at flagship products like the Denon AVR-5805 or Yamaha RX-Z11 The AVR-5805 to date IMO has the best amp section a receiver has ever seen!

well excuuuuuuuuuussssseee me for not using the word typically!!!

Those two are excpetions rather than the rule.

 

[GranteedEV]

Hey I've got a question. Basically I'm building a sub with a pro-amp running it. Being a ported design the simulations give me tons of overexcursion below the tuning frequency at high power levels - but my problem is that I don't want to over-do a subsonic filter if I won't ever be hitting extreme power levels - especially considering that all my electronics should have slight rolloffs as you go lower in frequency.. I want to know the true power (including clipped dynamic signals) that the amp is capable of rather than the rated power. On paper the J2500 should be pushing ~2400W into a 4 ohm bridged load but realistically speaking:

1) On a 120v line with a 15 amp breaker and some likely voltage sag, I know that's not likely but i'm thinking it's certainly possible to get rather high instantaneous current even with that breaker in place.
2) I'm not trying to use the max power output, but I guess using "0 on the receiver" is a possibility and subwoofers AFAIK can peak at like 115db at these volumes. WIth room gain I'm sure my trims would be more realistic where I would not need much more than maybe 600-700W to do this with the sub I'm building but I just want to stay safe and not bottom it out... i'm sure its voice coils can handle tons of power based on what I've seen but I just don't need tons of power. I just went with this amp because of its non-limiting dynamic capability moreso than any plans to run it at full capacity. But I need to make sure that I'm not bottoming it out below the tuning frequency.

So my question is does anyone have any recommendations for making/buying a 4 ohm / 2000W-safe resistor for me to use in testing the amp's max capabilities so that I can figure out a more realistic high pass filter?

 

[M Code]

well excuuuuuuuuuussssseee me for not using the word typically!!!

Those two are exceptions rather than the rule.

There are more than 2 exceptions.
This is determined by the AVR's price-point...
If a brand is pushing for shelf space @ Best Buy the power output specs are hyped to the stinky side (BS), since Best Buy has difficulty in selling any AVR > $499 SRP. Also it makes little economic sense for a lower cost AVR (SRP < $499)to drive a 4 Ohms load as 90% of these AVRs are pushing bandwidth limited mini-cube satellites..

Now if the loudspeakers are quality full-range towers, and the AVR is a quality name brand whose SRP price point is > $1299 then it will have a much better probability for driving a 4 Ohm load...
As it will typically use more robust internal components such as power transformer, power supply capacitors, heat sinks, output devices.

One thing that many consumers have little understanding of is the royalty cost structure an HD AVR (HDMI 1.3 or higher) compared to an SD AVR (HDMI 1.2 or less).
The royalties of the HD AVR are 3x higher than the SD AVR..

Next question..

Just my $0.02...

 

[bandphan]

Hey M, are you from Cali, OK, or WVA?

 

[3db]

There are more than 2 exceptions.
This is determined by the AVR's price-point...
If a brand is pushing for shelf space @ Best Buy the power output specs are hyped to the stinky side (BS), since Best Buy has difficulty in selling any AVR > $499 SRP. Also it makes little economic sense for a lower cost AVR (SRP < $499)to drive a 4 Ohms load as 90% of these AVRs are pushing bandwidth limited mini-cube satellites..

Now if the loudspeakers are quality full-range towers, and the AVR is a quality name brand whose SRP price point is > $1299 then it will have a much better probability for driving a 4 Ohm load...
As it will typically use more robust internal components such as power transformer, power supply capacitors, heat sinks, output devices.

One thing that many consumers have little understanding of is the royalty cost structure an HD AVR (HDMI 1.3 or higher) compared to an SD AVR (HDMI 1.2 or less).
The royalties of the HD AVR are 3x higher than the SD AVR..

Next question..

Just my $0.02...

a.) NAD isn't sold at Best Buys here in Canada and who cares?
b.) Whats that have to do with your previous post? Gene and I were talking about the amp sections of NAD and how those two monsters from Denon and Yamaha ARE the exception rather than the rule when it comes to AVR power supplies and weight.
c.) You still didn't provide any thermal or electrical proof of why you think NAD rates its power? Is there an underlying reason for this or is this still speculative conjecture on your part?

Keep giving me your two cents and I'll have enough to buy me a coffee.

 

[M Code]

a.) NAD isn't sold at Best Buys here in Canada and who cares?

Best Buy was used an example as they are the largest CE retailer in North America, and to illustrate the different price segments of AVRs. One cannot use Canada retail pricing as it is significantly higher than the continental USA, beside Canada is a 10% market while the USA is 10x larger.

b.) Whats that have to do with your previous post? Gene and I were talking about the amp sections of NAD and how those two monsters from Denon and Yamaha ARE the exception rather than the rule when it comes to AVR power supplies and weight.

As mentioned previously AVRs built to meet mass price-points will have no headroom or capability into 4 Ohms.
However...
As you move up into the higher tiered AVR models (SRP > $1299) for the primary brands such as Yamaha, Denon, Elite, Onkyo/Integra, Harman/Kardon and Marantz they will disclose their output power into 4 Ohm loads. For further info take a spec sheet for their $299 AVR and $1499 AVR, compare the weights..
Is the light starting to come on now..

c.) You still didn't provide any thermal or electrical proof of why you think NAD rates its power? Is there an underlying reason for this or is this still speculative conjecture on your part?

Sorry...
We are unable to disclose the actual measured electrical performance specifications as we are under confidential disclosures agreements for the various mentioned brands. Doing so would only open up other legal issues. However my suggestion is that if you wnat to dig deeper..
Call NAD in Pickering, Ontario ask for Greg. Greg is their corporate director for Global Product Development of all NAD electronics, he can answer any technical questions you may have. Mention to him that Mark of D&H recommended that you call...

Keep giving me your two cents and I'll have enough to buy me a coffee.

No need to save the $0.00 as they are not worth much compared to the Canadian $. Instead send me a PM with your email address and we will supply you with a PayPal $5 voucher good @ Starbucks.


Just my $0.02..

 

[M Code]

Hey M, are you from Cali, OK, or WVA?

I spend most of my time in SoCal when not traveling to the Far East..
Also we have addresses in WVA and OK.

Just my $0.02..

 

[ichigo]

Sorry...
We are unable to disclose the actual measured electrical performance specifications as we are under confidential disclosures agreements for the various mentioned brands. Doing so would only open up other legal issues. However my suggestion is that if you wnat to dig deeper..
Call NAD in Pickering, Ontario ask for Greg. Greg is their corporate director for Global Product Development of all NAD electronics, he can answer any technical questions you may have. Mention to him that Mark of D&H recommended that you call...

If you can't disclosed measured performance of your products...I assume that means they don't jive with the marketing literature.

 

[M Code]

If you can't disclosed measured performance of your products...I assume that means they don't jive with the marketing literature.

Some brands are more honest than others, while others are just outright fibbers..
Regarding NAD they do pretty well against published specs..

Just my $0.02...

 

[gene]

I just added multi-tone IMD distortion testing and distortion ratio frequency sweep testing to our measurement standard.

 

[PENG]

I just added multi-tone IMD distortion testing and distortion ratio frequency sweep testing to our measurement standard.

Great, time to do a shoot out of the Denon X4000, 4520, Yamaha 1030, 3030, Onkyo 1010,5010, or just pick 1 from each if that's too much work for you to test in one day.

 

[RichB]

I just added multi-tone IMD distortion testing and distortion ratio frequency sweep testing to our measurement standard.

For the first watt'ers, could amp THD be measured starting at .1 watt?

- Rich