Audioholics Amplifier Measurement Testing Methodology

[gene]

New Video of Hugo and myself discussing amplifier measurements.

Audioholics Amplifier Measurement Interview
​

 

[cpp]

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...

I don't think any manufacturer regardless of who they are actually discloses their actual measured performance, until people like Stereophile actually test it and mesurement then you know.

I think Gene needs to add a NAD AVR to the test...

 

[Marshall_Guthrie]

I don't Know if I hold Stereophile as a paragon of objectivity. Just today, one of their professional reviewers wrote this:

The speakers partnered with Emotiva's XDA-2 DAC and XPA-1L monoblocks. I didn't write much in my notes about the music, but I recall wondering if the "nice classical music" the boys were playing would have made a greater impression had the price of the electronics been more commensurate with that of the speakers.

I don't think any manufacturer regardless of who they are actually discloses their actual measured performance, until people like Stereophile actually test it and mesurement then you know.

I think Gene needs to add a NAD AVR to the test...

 

[Reverberocket]

Great article - thanks!

Gene (and crew),

Thanks for this timely article!

Being in the camp of 'never too much power', I recently purchased a Crown XLS 2500, fed from the pre-outs of my Yamaha RX-659 (your awesome 2006 review: Yamaha RX-V659 Overview and Build Quality | Audioholics ).

In my middling system, the Crown feeds a pair of JBL L5's and specs out at 600 watts/channel into their 6 ohm load. For sure, I won't need another amplifier upgrade for a looong time. Added benefit - I can use the front channels of the receiver to run added presence speakers. One step closer to the 'musicians in the room' goal.

 

[cpp]

I don't Know if I hold Stereophile as a paragon of objectivity. Just today, one of their professional reviewers wrote this:

The speakers partnered with Emotiva's XDA-2 DAC and XPA-1L monoblocks. I didn't write much in my notes about the music, but I recall wondering if the "nice classical music" the boys were playing would have made a greater impression had the price of the electronics been more commensurate with that of the speakers.

Well regarding Stereophile, since it is one of a few sites that perform some measurements on Audio equipment its the best we have unless someone else has a lot of quality test equipment and are up for reviewing and validating vendors measurements. I use any measurements as a guide nothing more, I let the ears decide.

 

[gene]

Well regarding Stereophile, since it is one of a few sites that perform some measurements on Audio equipment its the best we have unless someone else has a lot of quality test equipment and are up for reviewing and validating vendors measurements. I use any measurements as a guide nothing more, I let the ears decide.

Not to toot our own horn but Audioholics amplifier measurements and analysis goes much deeper than any other AV Magazine in the industry including Stereophile. Also we are the only publication I know of using the $40k APx585 HDMI Audio Analyzer.

 

[jinjuku]

Not to toot our own horn but Audioholics amplifier measurements and analysis goes much deeper than any other AV Magazine in the industry including Stereophile. Also we are the only publication I know of using the $40k APx585 HDMI Audio Analyzer.

That and you are not John Atkinson.

 

[cpp]

Not to toot our own horn but Audioholics amplifier measurements and analysis goes much deeper than any other AV Magazine in the industry including Stereophile. Also we are the only publication I know of using the $40k APx585 HDMI Audio Analyzer.

Got that right but, since Gene doesn't test and measure all of the devices out there we got to fall back on a few other mag's to tell us, something. I would like to see Gene compare the following : a Bryston 4BSST2, ATI2002, Parasound Halo A21, Emotiva XPA-2

 

[Russ750]

Thanks Gene, so much for your dedication

I would like to thank Gene so much for his interest and dedication to honest, no nonsense reviews. No six loons hyperbole. I can actually read the articles and they make sense. I think this standard will really help in the class D arena. Especially with smps power supplies.

 

[Russ750]

Line sag and testing

The following only applies to monster amplifiers.

I noticed Gene, that you are not using a Variac, which i applaud. I was wondering about the test environment though. In Audioholics testing of the Emotiva XPR-1. I noticed that you had a 20 amp circuit. Which is what is required for this amp. However you also started to get line sag once the amp was pushed. Which brings me to the question of what length, and what size wire was between the amp and the main panel?

For reference, a 15A load with 12GA wire (common modern house wiring), You need less than 40 feet of electric wire to maintain 2V or better line sag. For 20A less then 28 feet. (Voltage Drop Calculator). This is with only one outlet. If the multiple outlets are daisy chained (which is common), it increases impedance even more.

For those not familiar with idea of line sag. Try hooking five, 50' foot garden hoses together. Then, turn the water on and see how much water comes out. Its fairly similar with electricity. You either need a bigger hose, or shorter length.

Anyway Gene, I was just wondering about your wiring. I just thought i would ask, as it could make a difference. And if your not going to use a Variac. Is the wire the right size so the amp can really shine? If not, your not letting it live up to its true potential. For a run of up to 45 feet , a 10 gauge wire, could make a significant difference on a twenty amp circuit. If going fifty to seventy feet 8 gauge is needed. So even though these gauge wires are rated for more amps, than we are using. To prevent voltage drop they are a must. And to be fair to any amplifier in the review, voltage drop is not the amps fault. It is inadequate wiring.

I also thought it might be useful to make people aware if, they are thinking about buying a very powerful amplifier. They most likely will need to hire an electrician, to get the most use out of there amp. Also it never hurts to up the wire one size to prevent any line sag. In fifty feet it would add less than fifty dollars.

 

[DaMaster]

As the Most hardcore Audio review site in the world

To bad you guys don't do enough reviews.
Maybe start doing Car equipment reviews so you can get more content.
infact the car audio guys are struggling for a high def Dsp with over 100db but nothing .

Precision power just released the P63c3 wich users an air motion tweeter but other components claim to offer HD sound but no proof from any sites that their equipment is audiophile quality.

 

[gene]

To bad you guys don't do enough reviews.
Maybe start doing Car equipment reviews so you can get more content.
infact the car audio guys are struggling for a high def Dsp with over 100db but nothing .

Precision power just released the P63c3 wich users an air motion tweeter but other components claim to offer HD sound but no proof from any sites that their equipment is audiophile quality.

I'd love to do more amplifier reviews if I had locally qualified people to use our test gear and write an accurate test report. But we focus more on quality than quantity.

 

[gene]

The following only applies to monster amplifiers.

I noticed Gene, that you are not using a Variac, which i applaud. I was wondering about the test environment though. In Audioholics testing of the Emotiva XPR-1. I noticed that you had a 20 amp circuit. Which is what is required for this amp. However you also started to get line sag once the amp was pushed. Which brings me to the question of what length, and what size wire was between the amp and the main panel?

For reference, a 15A load with 12GA wire (common modern house wiring), You need less than 40 feet of electric wire to maintain 2V or better line sag. For 20A less then 28 feet. (Voltage Drop Calculator). This is with only one outlet. If the multiple outlets are daisy chained (which is common), it increases impedance even more.

For those not familiar with idea of line sag. Try hooking five, 50' foot garden hoses together. Then, turn the water on and see how much water comes out. Its fairly similar with electricity. You either need a bigger hose, or shorter length.

Anyway Gene, I was just wondering about your wiring. I just thought i would ask, as it could make a difference. And if your not going to use a Variac. Is the wire the right size so the amp can really shine? If not, your not letting it live up to its true potential. For a run of up to 45 feet , a 10 gauge wire, could make a significant difference on a twenty amp circuit. If going fifty to seventy feet 8 gauge is needed. So even though these gauge wires are rated for more amps, than we are using. To prevent voltage drop they are a must. And to be fair to any amplifier in the review, voltage drop is not the amps fault. It is inadequate wiring.

I also thought it might be useful to make people aware if, they are thinking about buying a very powerful amplifier. They most likely will need to hire an electrician, to get the most use out of there amp. Also it never hurts to up the wire one size to prevent any line sag. In fifty feet it would add less than fifty dollars.

I hear you but I was at the liberty of the builder when I was building my house and they use the local electrical codes to conform for 15 and 20A lines. They wouldn't let me change the power cable but I was able to use my own line level and speaker cables.

I was still able to get over 2kwatt of power from the XPR-1 in my test rig which is more power than anyone could ever dream to use. The issue wasn't as much as getting more power as it was about keeping the distortion low due to the line sagging. In any event, its one beast of an amp and that's using it as 120V. I could only imagine 220V plugged into this baby!

 

[Adam2434]

Hi, new to this forum.

Posted this same question on the AVS forum, but thought this would be a good place, given the subject of this thread and the article's indication that bass management is a factor in whether a receiver can provide enough power.

Are there quantifiable amplifier benefits when a bass management high pass filter is applied, and how does this vary with high pass filter frequency?

I've read that amplifier headroom increases, but is headroom or some other performance parameter quantifiable?

I've been curious about this for a while.

Thanks.

 

[gene]

Yes since bass uses the most amplifier power (long duty cycle nature of bass waves), setting all speakers to "small" with a crossover of 80Hz will alleviate much of the strain on the receiver since the powered sub will be handling the bass. This can give you a significant amount of headroom. However, it's also important to choose speakers that don't dip down below 4 ohms at high F as that could still be problematic with some receivers, notably the older Pioneers employing ICE amplification.

 

[PENG]

I did a quick experiment to compare the amplifier voltage output for the center channel between full range and 80 Hz crossover, using:

The Dark Knight Rises,
04:35 to 06:35

Full range: Max 3.4 Vrms, Average 1.4 Vrms
XO at 80 Hz: Max. 2.85V rms, Average 1.16 Vrms

So the power difference is >40% between full range and XO=80 Hz in this particular test.

 

[Adam2434]

Gene and Peng, thanks for the replies.

I can see that power consumption would be lower with the high pass engaged.

I'm trying to understand if there is way to quantify or estimate the impact to headroom, watts/ch, or some other parameter. Like, does setting the high pass to 80 Hz increase headroom by "x" dB or increase power by "y" watts/ch?

 

[PENG]

Gene and Peng, thanks for the replies.

I can see that power consumption would be lower with the high pass engaged.

I'm trying to understand if there is way to quantify or estimate the impact to headroom, watts/ch, or some other parameter. Like, does setting the high pass to 80 Hz increase headroom by "x" dB or increase power by "y" watts/ch?

In the example I used based on the center channel, by setting XO to 80 Hz the amp output voltage dropped from 3.4V to 2.85V. Since power output is proportional to V^2, the corresponding power output reduction would have been approx. 42.3% and that's about 1.56 dB. So you can see that in my case, XO at 80 Hz versus full range equals roughly 1.56 dB headroom gain. Or you can think of it this way, that supposing I need 140 W for the center channel, by setting XO to 80 Hz, that requirement would drop to 100 W. Keep in mind, this example may be used as some sort of a rule of thumb only, the actual figures would also depend on the impedance characteristics of the speakers, the contents of the source media, and other factors.. The benefits would have been greater if, for example, the impedance of my center channel speaker drops well below 8 ohms between 20 to 80 Hz and the source media happens to have lots of low frequency contents. In that case, the otherwise heavier current demand on the amp for the low range would have been picked up by the subwoofer(s). If the contents have nothing below 80 Hz, then it wouldn't have made any difference in the example I used.

 

[Adam2434]

Thanks, Peng.

I wonder if the output voltage drop and headroom gain would be even higher in a 2.1 ch music context, since all of the bass frequencies are in those 2 channels, unlike a video soundtrack where much of the bass is in the LFE channel. I expect that the ratio of 20-80 Hz content would be higher in a lot of music vs. a video soundtrack's center channel. I'm talking music with a decent amount bass...say rock, country, blues, or pop with bass guitar and kick drum.

 

[PENG]

Thanks, Peng.

I wonder if the output voltage drop and headroom gain would be even higher in a 2.1 ch music context, since all of the bass frequencies are in those 2 channels, unlike a video soundtrack where much of the bass is in the LFE channel. I expect that the ratio of 20-80 Hz content would be higher in a lot of music vs. a video soundtrack's center channel. I'm talking music with a decent amount bass...say rock, country, blues, or pop with bass guitar and kick drum.

From what I have seen so far, I think in general the center channel probably does have comparable content to that of the left and right channels, aside from dialog. For music, it obviously would depend on the types of music and vary from title to title. If the music you listen to typically have a lot of bass guitar, double bass, and kick drum contents, then of course you will gain more headroom (as always, relatively speaking only) by setting XO to 80 Hz or higher.