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AHB2 Mono v Stereo - what is audible?

jaykay77

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Do any other AHB2 owners hear a difference between the mono and stereo units besides the extra +6db the monoblock nets you?

I usually buy equipment that measures well here...have had zero issues.

Thinking i'll grab another Ahb2 but...Mine sounds really good with my F208s...If I play things really loud, I can clip the amp but that's not until things get too loud for my liking.
 

virtuovice

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@Coach_Kaarlo recording #1 is forward, dare I say better instrument separation(?), and potentially stronger bass response.

What are the results of this test?
 

pjug

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Rather than a microphone recording, could you make a voltage divider to make a line level voltage to record? It seems to me background noise would always get in the way of using a microphone recording for comparison.

Then compare in DeltaWave in addition or instead of a listening comparison.
 
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Coach_Kaarlo

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@Coach_Kaarlo recording #1 is forward, dare I say better instrument separation(?), and potentially stronger bass response.

What are the results of this test?

Well, currently 3 people have participated.....so no results really.

However, it's interesting that such a divisive topic as what is audible in the real world has not generated much interest in my little experiment.

Many many respected members on this very forum would argue to the death that the differences between mono and stereo on an AHB2 are inaudible unless the amplifiers are clipping. Clearly a 100% result is not very meaningful with only 3 respondents, so hopefully others will also try their luck, preferably with a foobar printout attached to validate their claims.

THERE IS A DIFFERENCE!

Unless someone has hearing loss in which case why bother arguing about audibility and just enjoy that which one can hear.
 

RichB

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Well, currently 3 people have participated.....so no results really.

However, it's interesting that such a divisive topic as what is audible in the real world has not generated much interest in my little experiment.

Many many respected members on this very forum would argue to the death that the differences between mono and stereo on an AHB2 are inaudible unless the amplifiers are clipping. Clearly a 100% result is not very meaningful with only 3 respondents, so hopefully others will also try their luck, preferably with a foobar printout attached to validate their claims.

THERE IS A DIFFERENCE!

Unless someone has hearing loss in which case why bother arguing about audibility and just enjoy that which one can hear.

I have a setup for comparing amps using a MiniDSP SHD DSPs to duplicate the channels and level match within .1 dB measured with a Fluke 87V multimeter. The two outputs go to an A/B switch. This permits instantaneous switching with nearly perfect gain matching. The amps are driving Revel M126Be speakers.

Things are busy now, but I can setup a single AHB2 Stereo and compare it with 2 bridged AHB2s.
This is not a blind but it is otherwise a damn near perfect quick switching test.

I have thus far compared the AHB2 stereo to the Sunfire Cinema and ATI AT522NC and find no appreciably difference in bass response but the channel separation and high-end detail have been easily discerned with the AHB2. This is my sighed opinion anyway.

I should not when the Sunfire was running a bit louder than the AHB2, it sounded like it had more bass but when I adjusted the levels, the perceived bass advantage disappeared.

- Rich
 

pjug

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Well, currently 3 people have participated.....so no results really.

However, it's interesting that such a divisive topic as what is audible in the real world has not generated much interest in my little experiment.

Many many respected members on this very forum would argue to the death that the differences between mono and stereo on an AHB2 are inaudible unless the amplifiers are clipping. Clearly a 100% result is not very meaningful with only 3 respondents, so hopefully others will also try their luck, preferably with a foobar printout attached to validate their claims.

THERE IS A DIFFERENCE!

Unless someone has hearing loss in which case why bother arguing about audibility and just enjoy that which one can hear.
With regard to fixing levels: for RMS I get -20.1435 and -23.2806. So 3.14 dB difference not 3.33 dB.

Just eyeballing them in audacity they look quite different.
 

richard12511

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Dogma is not being able to consider rational alternatives. Rationally if only a few people can hear a difference no big deal, carry on.

However, if a large portion of listeners hear the same difference then we can start the science.....blind tests etc......because there may be some basis to the hypothesis. Rare that it is ever done the other way around in the real world.....apart from on ASR in the endless discussions of what is audible etc etc etc etc.....


My hypothesis: the real world addition of Revel F208 speakers to my system (see signature) produces audible differences in sound reproduction between the mono and stereo settings when using the AHB2 amplifier.


My simple experiment:
  1. same source content (Stevie Ray Vaughan live in Montreux - Texas Flood https://tidal.com/browse/track/1217)
  2. playback via Tidal into PC into DAC 2 then AHB2's into Revel F208's
  3. levels matched using random pink noise - full range (delta wave does show a small difference in level - oops just adjust in playback see edit below)
  4. [edit: the levels are off apologies, adjust File 1 =+0.67dB / File 2 = +4.00dB]
  5. REW version 5.20
  6. MiniDSP Umik-2 with 90 deg calibration file - positioned at 1050mm high, on the centre LP
  7. speaker CRS 2100mm
  8. same AHB2 amplifiers (switched between mono and stereo, and channel 2 interconnect and speaker cable connected to stereo position)
  9. same length speaker cable (damping factor not affected, cable capacitance and resistance unchanged)
  10. room effects removed by listening outdoors in free field conditions - see measurements below

The test - what is audible?
  1. file #1 was recorded with amplifiers set to mono or stereo
  2. file #2 was recorded with amplifiers set to mono or stereo
  3. files are identical and this was a bias test not a listening test (ie. I tell you they are different but you believe / hear they are not)

Links:

File 1 = https://drive.google.com/file/d/1Xyn_yQ2LbrVZE4KAmUiLrvBBsVxKDj2f/view?usp=sharing

File 2 = https://drive.google.com/file/d/17GHit4JTZbAzXAb4QNxEj8zkAqkh1XWB/view?usp=sharing

Record your results here = https://docs.google.com/spreadsheets/d/1TBzr7uOlnReLAC-NVYUcfFqvnZUQ5Hy_Dz1QSPPzpIw/edit?usp=sharing


Measurements below taken from the LP (recording point), with everything setup as recorded;

View attachment 120888

View attachment 120889

View attachment 120887



This is an imperfect, and overly simplified test = yes! But not everything of import needs to be the subject of extensive blind testing or published scientific peer reviewed papers. Some things are so blatantly obvious that they require no such benchmark - for example speakers with correct phase versus out of phase incorrect wiring........

This is a bit of fun to see what can be heard. Don't cheat yourself, listen and vote.

Second file has a ULF off rhythm drum beat I can feel that the first file is missing . I'm listening rather low on my main system right now, and the difference is obvious because the second file shakes my body, but the first file doesn't. Off rhythm drum beat seems to start in between the 3 and 4 second mark(towards the end of 3?). Can't tell if it's part of the music or not, as it sounds kinda random. The don't sound completely different imo, but it's super easy to feel the difference.
 
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pjug

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Something is wrong; I suspect recording is not controlled well enough.

For example, after crude aligning:

Window001.png
 

pjug

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Could that big dip in the lower right be the start of the low frequency beat that I mentioned above(post 27)?
I have no idea but it seems that it would be difficult to do a mic recording for comparison, with external sounds interfering, the person recording moving, etc. I haven't listened but I would want a better methodology if we want to compare amps (or in this case stereo vs mono in AHB2).
 

richard12511

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I have no idea but it seems that it would be difficult to do a mic recording for comparison, with external sounds interfering, the person recording moving, etc. I haven't listened but I would want a better methodology if we want to compare amps (or in this case stereo vs mono in AHB2).

Indeed. The repeating sound I'm hearing seems sorta random, off beat, and very low, which makes me think it's not even part of the music.
 

restorer-john

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@Coach_Kaarlo Yes, it's typical behaviour isn't it? People making excuses about this and that, analyzing the files to 'look' for differences instead of putting their audiophile balls on the line and ABXing the files first.

It's not hard. I did it, heard a difference and focused on it- my results show once I heard the difference, it was easy. That was one test, no peeking at files or cheating. Just trusted my ears and what I know about BTL amplifiers and how stereo amplifiers change their sound when you bridge them into a monoblock.

People seem to think their season ticket to the Audiophile playground will get revoked if they publicly admit something not popular, or they fail some "test". It's hilarious.
 

restorer-john

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@Coach_Kaarlo Have the house to myself for a few days so I could do the same here with a pair of these:

SMSL toy amp for scale.
1623812753882.jpeg


200+200W@8R or >580W@8R (~1kW@4R)* BTL each. I have three of them here.

*dummy load limited, not the amp.
 

pjug

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@Coach_Kaarlo Yes, it's typical behaviour isn't it? People making excuses about this and that, analyzing the files to 'look' for differences instead of putting their audiophile balls on the line and ABXing the files first.

It's not hard. I did it, heard a difference and focused on it- my results show once I heard the difference, it was easy. That was one test, no peeking at files or cheating. Just trusted my ears and what I know about BTL amplifiers and how stereo amplifiers change their sound when you bridge them into a monoblock.

People seem to think their season ticket to the Audiophile playground will get revoked if they publicly admit something not popular, or they fail some "test". It's hilarious.
What, it's not OK to ask to get the mess out of the files we are supposed to listen to? Personally I don't care about my ticket; I don't think I have any special hearing. I don't even think it is possible to level match these the way they are.
 

restorer-john

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I don't even think it is possible to level match these the way they are.

I'll try doing recordings with a reference (low level) tone which I'll electrically match prior and will also be on the recording. That should rule out some complaints?
 

pjug

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I'll try doing recordings with a reference (low level) tone which I'll electrically match prior and will also be on the recording. That should rule out some complaints?
If you want to compare amps I think you need to record output voltage. I suppose it could be done with a mic recording but but that seems to need much more care.

I'm as interested as anyone else about the premise that the bridged sounds different, just want good measurements.
 
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restorer-john

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If you want to compare amps I think you need to record output voltage. I suppose it could be done with a mic recording but but that seems to need much more care.

Output voltage does not tell you how they sound. That is the entire crux of the comparison. Does a single ended AHB-2 sound different to a pair of BTL mono AHB-2s? If so, can other people hear it? You have speaker interactions which an electrical capture will not show.

@Coach_Kaarlo maintains they sound different. Perhaps the recording rigour is inadequate. Sure, but an electrical capture is for measurements, not sound as perceived.

I'm of the same opinion as him. I have many amplifiers and generally, bridged mono versions of big power amplifiers do not sound the same to me. I have enough amplifiers here to make comparisons, and I long ago (many years) worked out BTL was inferior, regardless of the massive increase in available power. I never use my amps in bridged mono except if I want to wield a kilowatt, just for fun. :)
 

pjug

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Output voltage does not tell you how they sound. That is the entire crux of the comparison. Does a single ended AHB-2 sound different to a pair of BTL mono AHB-2s? If so, can other people hear it? You have speaker interactions which an electrical capture will not show.

@Coach_Kaarlo maintains they sound different. Perhaps the recording rigour is inadequate. Sure, but an electrical capture is for measurements, not sound as perceived.

I'm of the same opinion to him. I have many amplifiers and generally, bridged mono versions of big power amplifiers do not sound the same to me. I have enough amplifiers here to make comparisons, and I long ago (many years) worked out BTL was inferior, regardless of the massive increase in available power. I never use my amps in bridged mono except if I want to wield a kilowatt just for fun. :)
How can the speakers sound different if they are fed the same voltage?
 
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SIY

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How can the speakers sound different if they are fed the same voltage?

Exactly this. The speakers respond to voltage. Record and level match the voltage. Maybe this won't tell you which amp you'd prefer, but it will certainly tell you if they sound any different at matched levels.

Recording in the room adds a whole mess of variables. It's not something I'd do despite owning half a dozen calibrated lab-grade microphones, excellent recording interfaces, capable editing software, and well-marked positions for mike and speaker placement.
 

restorer-john

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How can the speakers sound different if they are fed the same voltage?

The impedance of the output stage and it's interaction with the load. You can feed a speaker 2.83V from a voltage source or develop 2.83V across that speaker from a current source. The speaker may sound and behave quite differently across its frequency range.

Imagine if I put a 10 ohm resistor in series with the speaker. And I turn up the amplifier, measure across the speaker 2.83V (1W@8R).

Then I disconnect the 10 ohm resistor, measure and level match across the speaker at 2.83V.

They will not sound the same with music.
 
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