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Bi-amping Revel Salon2 makes an ABX audible difference

NiagaraPete

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full range of signals in each channel, but the crossover in the speaker attenuates (filters) the frequencies not used by that set of drivers.
That defeats the purpose.
 

Pdxwayne

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For me it seemed very apparent. I guess ABX will tell if I heard what I thought I heard. There isn't much low end in the music to mask the rumble.
When I have time, will check with speaker system with a sub.
 

Tangband

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Does bi-amping make a difference? My Revel Salon2 speakers come with two pairs of binding posts, and the manual says:

Revel does not endorse one particular connection method over another.... The design of this loudspeaker is such that optimal performance can be attained using the standard connection method.

By connection method, do they mean bi-wiring, or is bi-amping included? When I switched to vertical bi-amping (one stereo amp per speaker), I sensed a subtle but definite improvement in clarity of high frequencies.

To start, let's compare frequency responses. In the vertical bi-amp configuration, each Salon2 is powered by one Benchmark AHB2 in its low gain mode, with the high and low frequency binding post each driven by one of the amp's two channels. In the normal configuration, the manufacturer supplied shorting bridge is used and the speaker is powered via one pair of binding posts. Note that in the normal configuration, each Salon2 is still powered by a separate AHB2, i.e. monoblocking using a single AHB2 channel per amp. This means any differences would be attributable solely to separation of high and low frequency amplification, and not to elimination of stereo crosstalk between the amp's two channels.


View attachment 199194

As we can see, frequency response is unchanged. Variations below 50hz are within usual variation on each measurement, so I wouldn't put any credence on differences there. Still, I was not convinced that the difference I was hearing was all placebo. It's impractical for me to do a blind test, given the time and effort required to change from bi-amp configuration to normal. An ABX with enough repetitions to prove audibility would take dozens of changes, each of which takes longer than ideal for our short audio memories.

Recently in my previous experiment, it was shown that recorded speaker outputs can be used in an ABX test to demonstrate an audible difference for a change of speaker feet, so I wanted to see if this ABX method would also work here. I recorded the output of my Revel Salon2 speakers playing music in stereo using a pair of high quality cardioid microphones (Shure SM81), each mic 2' in front of the tweeter's logo.

I've attached sample clips of the recordings. The original is available free on 2L.co. I think you'll agree upon listening that these recordings are a good enough representation of the original to plausibly reveal differences. I did the ABX test using a piece I'm more familiar with, another recording of a classical string quartet.

The difference was minute, and ABX is hard. There's the time, effort, and mental fatigue. The default of 16 trials requires at least 32 intense listenings of the same passage, likely more. It takes training to tease out perceived differences that are real and can be repeatedly ascertained, versus those that turn out to be due to memory blur or too weak to be detected repeatedly with sufficient accuracy. Repeated listening causes a kind of burn in of the senses and memory. Eat a bite sized piece of single-origin chocolate and you can taste the nuances down to the trees that were planted next to the cocoa. Now imagine eating 32 pieces in a row and then asked to distinguish the nuances between the last two pieces.

I only take a test when I'm able to get good accuracy in training mode, and still my first two tests were only 10/16 and 9/16 correct, which led me to devise techniques to limit fatigue and its effects. It helped to identify an extremely short passage of 2 seconds and to limit listenings by reducing trials from 16 to 10, which is a tradeoff that requires a higher accuracy for statistical significance. I did the third test after training and improved to 9/10 trials correct (p = 0.0107).

View attachment 198976

It's no wonder to me now that ABX tests have come up null for all manners of changes. If I were a random subject brought in off the street, with no practice and no incentive to get the right answer, I would have performed even worse than my initial trials and we would have concluded there was no difference.

I do think the real difference is greater than is captured by the recordings, but that cannot be shown by this ABX setup.


TLDR

Vertical bi-amping of Revel Salon2 using 2x Benchmark AHB2 has the same frequency response but makes an audible difference.
Biamping causes less IMD distortion , very difficult to measure because its variable depending on the music content . The sound gets better .

Remember though that two amplifiers for the same price as one , might result in slightly less soundquality so the gain with biamping isnt always clear .

Next step to lessen IMD distortion even more is a fully active loudspeaker.
 

Pdxwayne

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For me it seemed very apparent. I guess ABX will tell if I heard what I thought I heard. There isn't much low end in the music to mask the rumble.
I checked with my stereo setup. With just sub on (stereo amp for speakers off), indeed I could sense the rumble with regular clip. However, once I turned on my stereo amp and my speakers start playing, the rumble was masked and I can't sense the rumble. Maybe you can sense the rumble with everything playing, but I can't.
: )
 

R Swerdlow

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Do you even know what is ABX? You first sentence shows that you don't.....
The OP admitted he didn't do a blind comparison test.
… It's impractical for me to do a blind test, given the time and effort required to change from bi-amp configuration to normal. An ABX with enough repetitions to prove audibility would take dozens of changes, each of which takes longer than ideal for our short audio memories.
Instead, he made recordings made with standard wiring and bi-amping, and compared them in an ABX manner. Unfortunately, he didn't run a series of comparison ABX tests, where one was done with recordings of std. wiring vs. bi-amping and the other was done direct, without recording. He did previously run ABX tests with recordings he made of his speakers with and without silicone rubber pads. But he doesn't know if recorded comparison of std. vs. bi-amping results in a valid test or not.

He wants us to believe recordings provide similarly equivalent results to non-recorded results in his bi-amp experiment, but he didn't provide any info or data from "previous experiments" that would demonstrate that.
Recently in my previous experiment, it was shown that recorded speaker outputs can be used in an ABX test to demonstrate an audible difference for a change of speaker feet, so I wanted to see if this ABX method would also work here. I recorded the output of my Revel Salon2 speakers playing music in stereo using a pair of high quality cardioid microphones (Shure SM81), each mic 2' in front of the tweeter's logo.
Finally, ABX tests or blinded non-ABX tests are convincing only when done with larger numbers of listeners. The OP did his tests with only himself as the listener. He may have repeated the test a number of times, but statistically N=1. That ain't statistics in any sense of the word.
 
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Blumlein 88

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The OP admitted he didn't do a blind comparison test.

Instead, he made recordings made with standard wiring and bi-amping, and compared them in an ABX manner. Unfortunately, he didn't run a series of comparison ABX tests, where one was done with recordings of std. wiring vs. bi-amping and the other was done direct, without recording. He did previously run ABX tests with recordings he made of his speakers with and without silicone rubber pads. But he doesn't know if recorded comparison of std. vs. bi-amping results in a valid test or not.

He wants us to believe recordings provide similarly equivalent results to non-recorded results in his bi-amp experiment, but he didn't provide any info or data from "previous experiments" that would demonstrate that.

Finally, ABX tests or blinded non-ABX tests are convincing only when done with larger numbers of listeners. The OP did his tests with only himself as the listener. He may have repeated the test a number of times, but statistically N=1. That ain't statistics in any sense of the word.
I'm not sure any of your criticisms hold water. Certainly a single person can do enough trials if truly blinded to determine if they can or cannot hear a given thing.
 

Blumlein 88

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The only obvious difference is a wide peak in response in the 30-50 hz range of nearly 20 db. This is just what I would suspect. It could be from a delivery truck 2 blocks away that you'd hardly notice, but it gets recorded. And under careful examination even if you don't discretely notice it, it can still be the reason you are able to detect the difference. Now whether that is audible will depend somewhat on how loud and what gear is being used. I suppose you could EQ it out and see if the difference is still there.

The best approach is to make 3 or 4 recordings of regular and bi-amping. Analyze it in Deltawave for low end anomalies and use any recordings that look clean. The reason I suspected this from the beginning is having done similar recordings and you have a heck of a time keeping unwanted noise differences out of the low end. Those low frequencies travel too far and are hard to keep out. Trains 5 miles away, planes overhead, trucks a few blocks away all get picked up. The fact the response is identical in both channels in that 30-50 hz range makes me even more suspicious this is unintended noise pickup.
 
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Blumlein 88

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It also might be worth doing a few sweeps in REW using your miking setup. It might show both a frequency response difference and distortion differences between regular and bi-amped.
 

billyjoebob

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It's within measurable statistical variation, I'd say.
So long as you are not using telephone wire, my guess is "bi-amping" is a myth designed to sell more overpriced cables.
But then again, I cannot remember where I left my RF ear-trumpets, so I may be wrong.
I am more or less in line with you....
But I have to ask.
Why would a speaker company place bi-amp connections on a speaker to sell cables that they do not produce and have no financial stake in?
I don't belive there is a sonic difference, but selling (another) company's speaker cable is not the reason.
I may be wrong, but I have never purchased speaker cables of the same brand as any speaker manufacturer.
In fact I have never purchased speaker cable other than standard 12-14 Guage lamp cord.
I also have never bi-amped any speaker that had the provisions,
So I may not know a whole lot anyway.
Just asking.
 

pjug

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I checked with my stereo setup. With just sub on (stereo amp for speakers off), indeed I could sense the rumble with regular clip. However, once I turned on my stereo amp and my speakers start playing, the rumble was masked and I can't sense the rumble. Maybe you can sense the rumble with everything playing, but I can't.
: )
I used headphones. It's just a flawed recording where the rumble can give it away, at least that is what I heard. I don't think you can get anything useful from this; I doubt that any microphone recording would get at whether bi-amping makes a difference.
1649789106468.png
 

voodooless

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Why would a speaker company place bi-amp connections on a speaker to sell cables that they do not produce and have no financial stake in?
I don't belive there is a sonic difference, but selling (another) company's speaker cable is not the reason.
It’s all one big system. The speaker cable companies want to sell cables, so advocate for bi-wiring. The speaker companies give them the means to do that, and it gives them an extra marketing opportunity to show of the dual or triple terminals some more that the magazines tout as the best thing since sliced bread. The thing is: speakers with dual terminals sell better than with single terminals. You can’t sell a respectable speaker without at least dual terminals. So yes, there is a lot of incentive to put these thing in!
 

pjug

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As I mentioned the differences were in high frequencies, and that's what I listened for. I mainly relied on one note from the violins/violas.
I assume you are talking about the recording? What I heard when doing the ABX, is that the track with less rumble sounded much better, with clearer mid and high freqs. Because the rumble wasn't there to muck it up. So even if you think you are only concentrating on the high end, the rumble still makes the difference.

I suggest you HP the tracks at 60Hz. There isn't much music in this track below 60Hz anyway. Then ABX the filtered tracks and show us your results.
 
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neutralguy

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I used headphones. It's just a flawed recording where the rumble can give it away, at least that is what I heard. I don't think you can get anything useful from this; I doubt that any microphone recording would get at whether bi-amping makes a difference.
Good job, and thanks for doing this investigation. It does look like this particular 2Lhaydn recording has a rumble that you can detect.

However, as I mentioned in my original post, I did my ABX using a different string quartet that I'm familiar with, which corresponds to the ABX log I posted. I didn't post that because the original source is not free.

I checked whether there's a rumble there. Here's how it looks in Audacity after 100hz 48db low pass and normalized (bottom is "haydn33 biampedNOT.flac" which is normal):
1649790473907.png

To compare, here is the same for the 2L file, which shows the rumble

1649790391059.png

so I don't think the same issue exists on the recordings I ABX'd. The entire recording is too large to post but I was distinguishing by listening only to the first couple seconds anyway, so here's a clip of the first 8s.
 

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  • haydn33 8s.zip
    1.3 MB · Views: 58

pjug

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Good job, and thanks for doing this investigation. It does look like this particular 2Lhaydn recording has a rumble that you can detect.

However, as I mentioned in my original post, I did my ABX using a different string quartet that I'm familiar with, which corresponds to the ABX log I posted. I didn't post that because the original source is not free.

I checked whether there's a rumble there. Here's how it looks in Audacity after 100hz 48db low pass and normalized (bottom is "haydn33 biampedNOT.flac" which is normal):
View attachment 199453

To compare, here is the same for the 2L file, which shows the rumble

View attachment 199451

so I don't think the same issue exists on the recordings I ABX'd. The entire recording is too large to post but I was distinguishing by listening only to the first couple seconds anyway, so here's a clip of the first 8s.
I don't mind trying, but if there aren't any cues from room noise pickup then I'm sure I won't pass. Is your posted ABX result for the whole track or the 8 sec version? If not the 8 sec version, do you mind doing it again with the short segment so we are all doing the same thing?
 

BDWoody

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Why would a speaker company place bi-amp connections on a speaker to sell cables that they do not produce and have no financial stake in?

Helping out the dealers.

Profit margins on cables is likelier higher than anything else they sell.

I may be wrong, but I think it was Benchmark, in their carefully worded answer on speaker cables said they don't believe esoteric cables will make any meaningful difference, but they encourage you to support your local dealer...or something like that.

They can't just say lampcord is fine...
 

blueone

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The OP admitted he didn't do a blind comparison test.

Instead, he made recordings made with standard wiring and bi-amping, and compared them in an ABX manner. Unfortunately, he didn't run a series of comparison ABX tests, where one was done with recordings of std. wiring vs. bi-amping and the other was done direct, without recording. He did previously run ABX tests with recordings he made of his speakers with and without silicone rubber pads. But he doesn't know if recorded comparison of std. vs. bi-amping results in a valid test or not.

He wants us to believe recordings provide similarly equivalent results to non-recorded results in his bi-amp experiment, but he didn't provide any info or data from "previous experiments" that would demonstrate that.

Finally, ABX tests or blinded non-ABX tests are convincing only when done with larger numbers of listeners. The OP did his tests with only himself as the listener. He may have repeated the test a number of times, but statistically N=1. That ain't statistics in any sense of the word.

A software ABX comparator (foobar's in this case) is blind. I agree that statistical significance is another matter altogether.

Personally, I think the fatal flaw in this test is using recordings for the comparisons, but who cares? This isn't a human drug trial, this is yet another attempt to find efficacy in the use of vertical passive bi-amping. What Revel says in their owners manual about potential audible improvements, is just marketing BS, if you're using competently designed amplifiers of sufficient power output. The Salon2 is just not an extraordinary load.
 

Blumlein 88

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Good job, and thanks for doing this investigation. It does look like this particular 2Lhaydn recording has a rumble that you can detect.

However, as I mentioned in my original post, I did my ABX using a different string quartet that I'm familiar with, which corresponds to the ABX log I posted. I didn't post that because the original source is not free.

I checked whether there's a rumble there. Here's how it looks in Audacity after 100hz 48db low pass and normalized (bottom is "haydn33 biampedNOT.flac" which is normal):
View attachment 199453

To compare, here is the same for the 2L file, which shows the rumble

View attachment 199451

so I don't think the same issue exists on the recordings I ABX'd. The entire recording is too large to post but I was distinguishing by listening only to the first couple seconds anyway, so here's a clip of the first 8s.
Can you drop both your recordings into Deltawave? It will do a null test of them and provide other information. You can download it for free here:


It is a Windows program.

Usually you can post music if you limit it to 30 seconds or so is the rule of thumb. That being said, I'm no lawyer and claim no expertise into the intricacies of the legal system for such matters.
 

Pdxwayne

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I used headphones. It's just a flawed recording where the rumble can give it away, at least that is what I heard. I don't think you can get anything useful from this; I doubt that any microphone recording would get at whether bi-amping makes a difference.
View attachment 199445
Very nice.

Curious, what is your listening chain?

At what listening level do you sense the rumble? Regular level where you typically listening to music or louder?

Thanks!
 
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neutralguy

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I don't mind trying, but if there aren't any cues from room noise pickup then I'm sure I won't pass. Is your posted ABX result for the whole track or the 8 sec version? If not the 8 sec version, do you mind doing it again with the short segment so we are all doing the same thing?

It turns out I can post the entire file if I separate them into individual zips. Here is the actual two files I ABX'd, and you'll see the same SHA1 as in my logs.
 

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  • haydn33 biamped.zip
    2.3 MB · Views: 39
  • haydn33 biampedNOT.zip
    2.3 MB · Views: 42
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