Bi-Amping Question

[Slave IV]

I'm experimenting with bi-amping and amplifiers in general.

Quick background is I got a couple of monobock amplifiers to start replacing channels being run from my receiver. The monoblocks have slightly higher power rating at 8 ohms, which is what my front and rear surrounds speakers are rated at. My first test using the monoblocks to run the front mains resulted in very positive and noticeable difference. My receiver has Audessy and it was already calibrated using all internal amps and I did not change any settings when switching to external monoblocks, just used the RCA pre-outs for the channels and swapped the speaker wire over. The output wasn't noticeably louder but the soundstage, clarity and everything else I could think of was improved.

Next test and this is where my question comes in is when I tested the monoblocks on the center channel. The center channel is matched from the same brand and line as the mains but it is rated at 4 ohms and my receiver is not rated to run 4 ohms but it has been fine in that configuration. The monoblocks are rated to run 4 ohms and should be delivering more than double the power the receiver could at that load. First thing I did was just use one monoblock hooked up to the center speaker same way I did the mains, by using the RCA preout and swapping the wires over and no changes to any settings. My expectation was that the difference would be even more noticeable but what resulted was lower volume and clarity. This is already very odd to me and makes no sense considering the results I got earlier with the fronts. So, I then used an RCA Y splitter cable to feed the center preout to both monoblocks and added wiring to bi-amp the center speaker. Now, it would be getting more than 4 times the power between the tweeter and mids and surely be a huge difference. Only thing is it ended up sounding about the same as just the single monoblock running the center and still less loud and clear as just using the receiver's internal amp. I haven't had time to test any further and just went back to running the front mains off the monoblocks since that had the best results but what could be causing this issue?

My first thought is that using the Y cable should be reducing the input signal to each amp so I need to adjust the gains but I was surprised that I did not see any mention of this when I was searching for a solution. Has anyone else had this issue and does this sound like it could be the culprit? I haven't done any math other than the basic understanding that the power ratings alone should have resulted in a higher output in both center channel tests regardless of gain settings since everything else stayed the same between all these tests. Am I missing anything? Thanks for any insight on this as it is my first post here and my first time dealing with monoblocks and bi-amping.

 

[Doodski]

I got a couple of monobock amplifiers to start replacing channels being run from my receiver. The monoblocks have slightly higher power rating at 8 ohms

My first test using the monoblocks to run the front mains resulted in very positive and noticeable difference.

The output wasn't noticeably louder but the soundstage, clarity and everything else I could think of was improved.

The center channel is matched from the same brand and line as the mains but it is rated at 4 ohms and my receiver is not rated to run 4 ohms but it has been fine in that configuration. The monoblocks are rated to run 4 ohms and should be delivering more than double the power the receiver could at that load.

So, I then used an RCA Y splitter cable to feed the center preout to both monoblocks and added wiring to bi-amp the center speaker. Now, it would be getting more than 4 times the power between the tweeter and mids and surely be a huge difference.

What are these mono-blocks and what AV receiver are you using? It is debatable that you actually hear a difference and most likely that you have expectation bias tricking your mind to think a sound quality difference is noticed. Your mono-blocks are most likely not delivering double the power into 4 Ohms speakers. We need to know what amps these are and what speakers.

 

[Slave IV]

What are these mono-blocks and what AV receiver are you using? It is debatable that you actually hear a difference and most likely that you have expectation bias tricking your mind to think a sound quality difference is noticed. Your mono-blocks are most likely not delivering double the power into 4 Ohms speakers. We need to know what amps these are and what speakers.

Thank you for the quick response and let me just add that I am not doing this to get higher output. It’s just the results I got with just the center channel, which was highly unexpected. I didn’t mention any brands or specific numbers because I’m trying to get a theoretical understanding of what happened. My ultimate goal is just to get better quality sound (clarity, soundstage) and I think my first test with the front mains already proved that part to me and I’m trying to figure out what went wrong with the center. Could be as simple as adjusting the gains but I wanted to learn more before I go back swapping wires around.

But if it helps get a better answer, the equipment involved is a Marantz receiver, SR-5007 and the monoblocks are the Fosi V3 Monos. The receiver is rated at 100w @ 8ohms with 2 channels driven and it is not rated to run 4 ohms and no ratings are given when multiple channels are driven but should be around or under 80w per channel. The Fosi are rated at 120w @ 8ohms and 240w @ 4ohms. Thanks!

 

[Doodski]

Now, it would be getting more than 4 times the power between the tweeter and mids and surely be a huge difference.

This is not correct. The crossovers permit higher frequency energy to go to the tweeters and mids and the power reaching them is very low compared to the low frequency woofer(s). The amount of power that reaches the tweeters and mids is a small fraction of that reaching the woofers. The bass frequencies are where the most energy is and that can be seen in the excursion of the woofer cones as compared to the excursion of the mids and tweeters. Bi-amping is not a beneficial method even if speaker manufacturers use bi-amping terminations at the rear of the speakers. If you want multiple amps and to divide up the power to the various drivers then go with an active crossover and use separate amps for the drivers. Bi-amping is a very very small difference in a passive crossover system that is not really audible but it has certainly taken over folklore and snake oil science.

 

[raindance]

You're confusing sensitivity and power. Not the same thing. The external amp is less sensitive than the built in amp and so you need to turn the volume up more.

Bi-amping is a waste of time and money and buys you nothing, except more complexity.

Going fully active, now there's something that could be good, but it requires more knowledge than it would appear you have to be successful.

 

[Slave IV]

I totally get going fully active as I have messed with that a lot in car audio but find it odd it is much less common and seemingly more difficult to get what is needed for it in home audio.

I get what you are saying as well about the possible benefits or lack of with this passive bi-amp setup and the way the power is being split. I agree and at this point, just trying to get a clear understanding how the same test I did with the mains got such different results with the center? If you are saying the sensitivity of the external amps is less than the internal, why did I get at least equal if not better output with the mains compared to noticeably less with the center, especially when the center has less resistance and was getting fed two amps that each have higher rating than the internal one? If there is a simple answer to this I'm not getting, that's what I'm here to try to learn.

 

[Doodski]

especially when the center has less resistance

The impedance of the speaker does not correlate with the efficiency of output. A 4 Ohm speakers and a 8 Ohm speaker can and oftentimes do have the same efficiency rating or similar.

I totally get going fully active as I have messed with that a lot in car audio but find it odd it is much less common and seemingly more difficult to get what is needed for it in home audio.

I used a Coustic XM-7 car audio electronic crossover for my home system for years and it functioned very well in the capacity.

trying to get a clear understanding how the same test I did with the mains got such different results with the center?

If you are saying the sensitivity of the external amps is less than the internal, why did I get at least equal if not better output with the mains compared to noticeably less with the center

The voltage output of the AV receiver center output is possibly lower than the mains pre-amp output and then the gain of the power amp(s) is starting out with a lower level signal right from the start.

 

[Slave IV]

The impedance of the speaker does not correlate with the efficiency of output. A 4 Ohm speakers and a 8 Ohm speaker can and oftentimes do have the same efficiency rating or similar.

I used a Coustic XM-7 car audio electronic crossover for my home system for years and it functioned very well in the capacity.
View attachment 398199


The voltage output of the AV receiver center output is possibly lower than the mains pre-amp output and then the gain of the power amp(s) is starting out with a lower level signal right from the start.

Haha, that is awesome! I've been considering using car audio equipment for home audio like that but I didn't want to deal with the power conversions and just figured it should be easier to do for home audio especially considering how so many people consider that a "higher class" than car audio. Makes me wonder why when I've been messing with fully active systems in car audio since high school and have heard the benefits there long ago and it's still such an uncommon thing for home audio.

Your comment about the pre-amp out for the center possibly being lower makes sense but then again, I don't get why they would do that and assume it would be the same but it is a simple explanation. Do you think my theory that the signal is also being reduced to each amp since I am splitting it also makes sense? Either way, it sounds like I should just try it again and bump up the gains this time. Appreciate all the input!

 

[Doodski]

Do you think my theory that the signal is also being reduced to each amp since I am splitting it also makes sense?

The voltage should not decrease by any large amount and you should still have enough voltage to the amps that you may adjust the input level control if it has one and be good to go. I don't have hard numbers to crunch but it almost always works well this way.

Haha, that is awesome! I've been considering using car audio equipment for home audio like that but I didn't want to deal with the power conversions and just figured it should be easier to do for home audio especially considering how so many people consider that a "higher class" than car audio. Makes me wonder why when I've been messing with fully active systems in car audio since high school and have heard the benefits there long ago and it's still such an uncommon thing for home audio.

Car audio active crossovers work very well for home audio and in fact they are some of the nicest active crossovers available. Don't be afraid to use a car audio active crossover for your home speakers.

 

[Slave IV]

The voltage should not decrease by any large amount and you should still have enough voltage to the amps that you may adjust the input level control if it has one and be good to go. I don't have hard numbers to crunch but it almost always works well this way.

Car audio active crossovers work very well for home audio and in fact they are some of the nicest active crossovers available. Don't be afraid to use a car audio active crossover for your home speakers.

Thanks for all the info! I’m going to be a bit more diligent and go back to test the center setups again and this time, I’m going to measure the output with a basic phone app so I at least have something more solid to work with. Once I confirm the center is playing at the same level, I’ll see how much a difference in sound the amps make. My guess is I’ll just go back to running the mains with the external amps and depending on how it goes, plan on getting one more matching amp to run the center later on.

I’m also convinced I won’t be fully satisfied until I go fully active so I’ll try it out now to see but until I get what I need to go fully active, I’ll save the bi-amping until then.

 

[Chrispy]

I'd not bother with bi-amping unless actively doing so and more with a specific design like diy vs taking a box made for specific drivers/crossover setup.

 

[DonH56]

Bi-amping 101

This article provides a quick look at how bi-amplification works. The conventional scheme is to split the signal into two frequency bands before the power amplifiers that drive the speakers. The bass (LF) amp sees only LF signals and drives only the LF driver (woofer). The treble (HF) amp sees...

www.audiosciencereview.com

 

[Slave IV]

I'd not bother with bi-amping unless actively doing so and more with a specific design like diy vs taking a box made for specific drivers/crossover setup.

That’s pretty much what I’ve been thinking. I was looking at some of the diy kits on Madisound along with coaxial drivers for high/mids and convinced myself that I’m not messing with regular passive crossover speakers again when the time comes to upgrade. It’s also funny going back to my car audio days and how coaxials were always considered lower end but I remember one particular system I put together for a friend using coaxials and being so impressed with the imaging. Driver designs have come a long way since then but the basic principles remain.

I’m listening to my HT now with the center hooked up to a single monoblock now with the levels properly set and it made all the difference. I found that it was indeed running 4db lower through the preout for the center vs less than 1 db lower when I ran the front main preouts so as little sense as that makes to me why they would design the outs that way, it makes all the sense to why I was hearing what I did. This is all also reassuring me that my hearing is not off, lol!

I am going to now hookup the other amp and try the bi-amp method out on the center with levels matched just to hear the difference for myself but it’s a concept I never even thought about except for in fully active setups before and agree it shouldn’t make a difference other giving me headroom I don’t think I need.

 

[Slave IV]

Bi-amping 101

This article provides a quick look at how bi-amplification works. The conventional scheme is to split the signal into two frequency bands before the power amplifiers that drive the speakers. The bass (LF) amp sees only LF signals and drives only the LF driver (woofer). The treble (HF) amp sees...

www.audiosciencereview.com

Thanks for sharing this! Really good info that I haven’t fully digested but get the gist of it.

FWIW, I now have my system setup bi-amped as I was originally asking about and I did not need to adjust the gain compared to the single external amp. Maybe .5 or 1 db so it was most certainly a case of the center preout just having less output for whatever reason. I will say that there is a noticeable difference in clarity but it is so subtle, I wouldn’t get an extra amp solely for the purpose of passively bi-amping. No surprise to anyone here about that.

Also, I know there is the natural bias to make yourself want to think you hear differences that aren’t there and I always second guess myself but I’ve had a “helper” basically doing blind testing and they have been spot on with their feedback without knowing anything about the different configurations.

So, since I have the two amps already and done my testing of the various configurations with them, I just want to get an opinion on what people here would do now in this situation. Things to note are this is in my living room, home theater setup so the priority is 5.1 for movies and shows. With two amps, the only configurations that make sense to me are using them one each for the two front mains or bi-amped for the center. The audible benefits are a tossup, both good in different ways. The only reasons I’m leaning towards bi-amping the center are because the receiver is not rated to run the 4 ohm center speaker and the center speaker generally carries the most information out of the three front. Ideally, I would just purchase a third matching amp so all three fronts are covered but until that happens, what would you do?

Thanks for all the responses here and I’m glad to have found this excellent resource and community for a hobby I’ve loved ever since I started paying attention and appreciating music as a kid. After rereading the responses, I just noticed that little dig thrown in by @raindance haha, I definitely don’t have a complete grasp of all the specific physics involved but I know enough to know really great sound when I hear it and enough to have been able to create systems that produce great sound in the past. Even though it’s always been a love of mine, my priorities have been in other areas for a long time and I’m slowly getting back into this in chunks here and there and that’s why I came here to learn.

 

[MaxwellsEq]

It's quite easy to get caught up in the mix of gain, amplifier input sensitivity, speaker sensitivity, speaker impedance, power etc.

The thing that often has the least impact on sound is amplifier power, since we mostly listen at a few Watts and doubling the power capability of an amplifier only makes a slight difference in max sound. Assuming the amplifier can handle different impedances OK, speaker impedance also doesn't have a massive impact on sound.

Speaker sensitivity can really make a large difference in how loud everything sounds.

Amplifier gain and input sensitivity also can make quite a difference. If you had a highly sensitive 20W power amplifier with a gain of 40dB and you swapped it for a 600W power amplifier with a low sensitivity and a gain of 10dB you would be amazed at how much quieter the 600W amplifier was (with the pream
plifier volume set at your normal level).

 

[DonH56]

Thanks for sharing this! Really good info that I haven’t fully digested but get the gist of it.

FWIW, I now have my system setup bi-amped as I was originally asking about and I did not need to adjust the gain compared to the single external amp. Maybe .5 or 1 db so it was most certainly a case of the center preout just having less output for whatever reason. I will say that there is a noticeable difference in clarity but it is so subtle, I wouldn’t get an extra amp solely for the purpose of passively bi-amping. No surprise to anyone here about that.

Also, I know there is the natural bias to make yourself want to think you hear differences that aren’t there and I always second guess myself but I’ve had a “helper” basically doing blind testing and they have been spot on with their feedback without knowing anything about the different configurations.

So, since I have the two amps already and done my testing of the various configurations with them, I just want to get an opinion on what people here would do now in this situation. Things to note are this is in my living room, home theater setup so the priority is 5.1 for movies and shows. With two amps, the only configurations that make sense to me are using them one each for the two front mains or bi-amped for the center. The audible benefits are a tossup, both good in different ways. The only reasons I’m leaning towards bi-amping the center are because the receiver is not rated to run the 4 ohm center speaker and the center speaker generally carries the most information out of the three front. Ideally, I would just purchase a third matching amp so all three fronts are covered but until that happens, what would you do?

Thanks for all the responses here and I’m glad to have found this excellent resource and community for a hobby I’ve loved ever since I started paying attention and appreciating music as a kid. After rereading the responses, I just noticed that little dig thrown in by @raindance haha, I definitely don’t have a complete grasp of all the specific physics involved but I know enough to know really great sound when I hear it and enough to have been able to create systems that produce great sound in the past. Even though it’s always been a love of mine, my priorities have been in other areas for a long time and I’m slowly getting back into this in chunks here and there and that’s why I came here to learn.

You are welcome.

Besides blind controls, level matching is usually the biggest issue when running audio tests. A very small (~0.1 dB) increase in loudness will sound better to us, so swapping amps with slight differences in gain can lead to favorable impressions, and perception bias is so very strong that once heard we cannot "unhear" a perceived improvement.

If your AVR is not overheating and the sound is OK I would not bother with another amp and spend the money elsewhere (or save for retirement!) Bi-amping implemented by an AVR does not add power so, if you do need more power, you'd be better off buying a single higher-powered amplifier instead. In your case, I would probably use one of the mono amps to drive the center, and sell or store the other amp until needed or you can afford to buy a third amplifier.

FWIWFM - Don

 

[Slave IV]

It's quite easy to get caught up in the mix of gain, amplifier input sensitivity, speaker sensitivity, speaker impedance, power etc.

The thing that often has the least impact on sound is amplifier power, since we mostly listen at a few Watts and doubling the power capability of an amplifier only makes a slight difference in max sound. Assuming the amplifier can handle different impedances OK, speaker impedance also doesn't have a massive impact on sound.

Speaker sensitivity can really make a large difference in how loud everything sounds.

Amplifier gain and input sensitivity also can make quite a difference. If you had a highly sensitive 20W power amplifier with a gain of 40dB and you swapped it for a 600W power amplifier with a low sensitivity and a gain of 10dB you would be amazed at how much quieter the 600W amplifier was (with the pream
plifier volume set at your normal level).

I agree with most of this and have found the power levels thing to be true in my tests given the amplifiers are of similar quality. But it also leads to another question I have that I’ll elaborate on below. I would say in this case, what threw me off the most was the difference in output level for the center preout compared to the mains preouts. The receiver was designed to output equal power to all channels when using internal amps so not sure why they would design the preouts that way. I just double checked the speaker specs and found the center is more sensitive than the fronts too so there really must be a big difference in the preout levels.

You are welcome.

Besides blind controls, level matching is usually the biggest issue when running audio tests. A very small (~0.1 dB) increase in loudness will sound better to us, so swapping amps with slight differences in gain can lead to favorable impressions, and perception bias is so very strong that once heard we cannot "unhear" a perceived improvement.

If your AVR is not overheating and the sound is OK I would not bother with another amp and spend the money elsewhere (or save for retirement!) Bi-amping implemented by an AVR does not add power so, if you do need more power, you'd be better off buying a single higher-powered amplifier instead. In your case, I would probably use one of the mono amps to drive the center, and sell or store the other amp until needed or you can afford to buy a third amplifier.

FWIWFM - Don

I really love how this community is kind of like anti-enablers whereas other hobbies I have seem to be filled with enablers who just want everyone to buy everything. It’s really refreshing!

So again, I agree that the levels make a big difference and it was partially my laziness but also partially my desire to just hear the difference without changing anything but the amplifiers. It worked fine with my first test on the front speakers but that difference in center preout level really threw me off but I’m glad such a simple fix led me to learn a lot more.

Which leads to this next question related to power output. My whole journey is all about getting better sound and I don’t listen to anything at max levels so the goal of the external amps was not because I needed more volume (otherwise, I would have needed much, much more power amps). Quality is one thing and I believe with all else being equal, an external amp should perform better than internal amps sharing circuitry with a bunch of other functions. That’s why I made sure when selecting my receiver that it had preouts and I have confirmed this in my tests. So my question is: what are the thoughts here regarding some speakers that seem to “come alive” with more power fed to them. I’ve heard people say that some speakers are known to be power hungry and feeding them more will make them sound better at the same levels (again, not for the purpose of max spl). I am experiencing this with my speakers and again, this is after adjusting the levels to match and with blind tests with another person. We both hear an extra layer of detail and openness. What the take on this thought here?

 

[DonH56]

Which leads to this next question related to power output. My whole journey is all about getting better sound and I don’t listen to anything at max levels so the goal of the external amps was not because I needed more volume (otherwise, I would have needed much, much more power amps). Quality is one thing and I believe with all else being equal, an external amp should perform better than internal amps sharing circuitry with a bunch of other functions.

This seems wrong. All else equal, you should not hear any difference. There is more in the chassis, true, but the power amplifiers themselves don't share "a bunch of other functions". The performance of the internal amplifier channels is most likely limited by the power supply and thermal management (heat). If you are not stressing the amps, there is no reason to assume an external amp will sound better even if it measures better. We have amplifiers (and most other components aside from speakers, and even them at levels within their capabilities) that measure better than we can hear (despite the marketing hype and mythology). Audio companies love to upsell customers whether they have a real need or not.

That’s why I made sure when selecting my receiver that it had preouts and I have confirmed this in my tests. So my question is: what are the thoughts here regarding some speakers that seem to “come alive” with more power fed to them. I’ve heard people say that some speakers are known to be power hungry and feeding them more will make them sound better at the same levels (again, not for the purpose of max spl). I am experiencing this with my speakers and again, this is after adjusting the levels to match and with blind tests with another person. We both hear an extra layer of detail and openness. What the take on this thought here?

Almost every time I have heard this, simply turning up the volume a hair achieved the same results. There are speakers that require much more power due to low sensitivity and/or low impedance, but without controlled tests (blind and level-matched), confirmation bias will win every time. I spent many years in the industry and my first series of blind tests were very revealing and quite humbling. The vast majority of the time I could tell how much better a new "thing" was, the difference disappeared in a controlled test. Or the new thing I heard, I could hear with the old system, when I switched back and looked for it. The wonderful new layers of detail and new things I never heard before in the recording that I could hear with the new component, I could also hear when I went back to the old, once I was looking for it. Blah.

I have not read this whole thread and do not know if you specified your exact test conditions and switching system. Well-controlled testing is a pain to set up and run; e.g., level matching is critical (0.1 dB is about 1%), fast switching is critical (our auditory memory is about 6 seconds), double-blind conditions where nobody knows what device is in the loop, and so forth are all required. Otherwise it is all too easy to let preconceived notions dominate the test results, and that includes any friends helping unless the test conditions are tightly controlled and nobody knows which component is being heard at any point during the test. It is virtually impossible not to pre-bias ourselves and our friends prior to testing. Ours ears are very sensitive, but our brain processes the sound, and is all too easily fooled.

Most people use far less average power and need more peak power than they imagine. If you are actually clipping the amplifiers in the AVR, you may hear a difference on loud passages, and if the noise floor is lower the amps may sound quieter, even if there is no real change in the sound when the music plays. An amplifier with lower output impedance (higher damping factor) will be less sensitive to the load (speaker impedance) and that can modify the frequency response you hear (I have an article about that, among other things, see the link in my signature). These are real things that can cause real changes in the sound, but marketing has played what are usually small if not insignificant changes into huge "night and day" differences. Consumers (you, me, everyone) pay the price.

I can confidently say, based upon a wealth of personal experience and decades of dabbling, that if you think you hear a difference and cannot perform a proper test (again, hard to do), then you will hear a difference even if imagined and nothing anyone will say here or elsewhere will convince you otherwise.

I will post my ancient "how much power do I need" post below in case it helps. It is 20+ years old now, and the handwritten notes from which it came are 40+, but it is still pretty relevant.

FWIWFM - Don


Power Needs:

For many years I have used 17 dB peak-to-average power based on an old AES article I can no longer find. Anecdotally various audio fora report 20 dB or more for movies. IME most people use much less average power than they think, but require more peak power. An online calculator can help you estimate your average power; note 80 dB is very loud to me (YMMV). Here is one:

Peak SPL Calculator

Most people think of volume in dB and most modern AVR/AVP/etc. units list dB on the volume knob. Power in dB goes as 10log10(Power_ratio) so the change in power is 10^(dB/10). Here are some reference numbers in dB and power:

1 dB is barely noticeable and requires 1.26x the power
3 dB is what most people hear as "a little louder" and requires 2x the power
6 dB is significantly louder and requires 4x the power
10 dB sounds twice as loud and requires 10x the power
17 dB is the headroom for music and requires 50x the average power
20 dB for movies requires 100x the power

If you listen at around 1 W average, then you need 50~100 W to avoid clipping on most source material. You can figure out your estimated average power from the calculator knowing your speaker's sensitivity and distance from them. Note music may be more compressed and thus require less headroom, and the loudest sounds in movies tend to be things like gun shots and explosions where a little clipping is likely unnoticeable.

HTH - Don

 

[Slave IV]

This seems wrong. All else equal, you should not hear any difference. There is more in the chassis, true, but the power amplifiers themselves don't share "a bunch of other functions". The performance of the internal amplifier channels is most likely limited by the power supply and thermal management (heat). If you are not stressing the amps, there is no reason to assume an external amp will sound better even if it measures better. We have amplifiers (and most other components aside from speakers, and even them at levels within their capabilities) that measure better than we can hear (despite the marketing hype and mythology). Audio companies love to upsell customers whether they have a real need or not.


Almost every time I have heard this, simply turning up the volume a hair achieved the same results. There are speakers that require much more power due to low sensitivity and/or low impedance, but without controlled tests (blind and level-matched), confirmation bias will win every time. I spent many years in the industry and my first series of blind tests were very revealing and quite humbling. The vast majority of the time I could tell how much better a new "thing" was, the difference disappeared in a controlled test. Or the new thing I heard, I could hear with the old system, when I switched back and looked for it. The wonderful new layers of detail and new things I never heard before in the recording that I could hear with the new component, I could also hear when I went back to the old, once I was looking for it. Blah.

I have not read this whole thread and do not know if you specified your exact test conditions and switching system. Well-controlled testing is a pain to set up and run; e.g., level matching is critical (0.1 dB is about 1%), fast switching is critical (our auditory memory is about 6 seconds), double-blind conditions where nobody knows what device is in the loop, and so forth are all required. Otherwise it is all too easy to let preconceived notions dominate the test results, and that includes any friends helping unless the test conditions are tightly controlled and nobody knows which component is being heard at any point during the test. It is virtually impossible not to pre-bias ourselves and our friends prior to testing. Ours ears are very sensitive, but our brain processes the sound, and is all too easily fooled.

Most people use far less average power and need more peak power than they imagine. If you are actually clipping the amplifiers in the AVR, you may hear a difference on loud passages, and if the noise floor is lower the amps may sound quieter, even if there is no real change in the sound when the music plays. An amplifier with lower output impedance (higher damping factor) will be less sensitive to the load (speaker impedance) and that can modify the frequency response you hear (I have an article about that, among other things, see the link in my signature). These are real things that can cause real changes in the sound, but marketing has played what are usually small if not insignificant changes into huge "night and day" differences. Consumers (you, me, everyone) pay the price.

I can confidently say, based upon a wealth of personal experience and decades of dabbling, that if you think you hear a difference and cannot perform a proper test (again, hard to do), then you will hear a difference even if imagined and nothing anyone will say here or elsewhere will convince you otherwise.

I will post my ancient "how much power do I need" post below in case it helps. It is 20+ years old now, and the handwritten notes from which it came are 40+, but it is still pretty relevant.

FWIWFM - Don


Power Needs:

For many years I have used 17 dB peak-to-average power based on an old AES article I can no longer find. Anecdotally various audio fora report 20 dB or more for movies. IME most people use much less average power than they think, but require more peak power. An online calculator can help you estimate your average power; note 80 dB is very loud to me (YMMV). Here is one:

Peak SPL Calculator

Most people think of volume in dB and most modern AVR/AVP/etc. units list dB on the volume knob. Power in dB goes as 10log10(Power_ratio) so the change in power is 10^(dB/10). Here are some reference numbers in dB and power:

1 dB is barely noticeable and requires 1.26x the power
3 dB is what most people hear as "a little louder" and requires 2x the power
6 dB is significantly louder and requires 4x the power
10 dB sounds twice as loud and requires 10x the power
17 dB is the headroom for music and requires 50x the average power
20 dB for movies requires 100x the power

If you listen at around 1 W average, then you need 50~100 W to avoid clipping on most source material. You can figure out your estimated average power from the calculator knowing your speaker's sensitivity and distance from them. Note music may be more compressed and thus require less headroom, and the loudest sounds in movies tend to be things like gun shots and explosions where a little clipping is likely unnoticeable.

HTH - Don

I’ve used that calculator before, thank you for creating it! Again, I really appreciate the details and experiences shared here. I think your point about dampening factor resonates with me and I’d add that distortion rating are the two factors that make the biggest difference to me in my experiences. Whether they be “real” or not, the best sound systems I’ve heard were usually powered by amplifiers with very low distortion ratings and high dampening factor ratings.

Of course, many of my tests were not perfectly measured but it goes back to the difference between something that sounds “right” is really noticeable to me, at least in my mind. This is when I’m listening to any sound system and in many cases not knowing anything about it other than what I hear and then learning about the details afterwards. I would also say that the speakers, placement and tuning are the three biggest factors that lead to great sound in my experiences but I’m really trying to nail down how much of a factor amplification plays.

A lot of what I’m hearing here seems to imply most people are saying the amplification doesn’t matter as long as you have the amount needed to drive your speakers at the desired levels. I just can’t wrap my head around that yet and find it hard to believe that you all are happy running swap meet amplifiers in your systems. Are you saying there should be no difference between a receiver, running separates, or different amplifiers as long as they are producing similar power under similar loads?

 

[DonH56]

I’ve used that calculator before, thank you for creating it!

Not mine, I just linked to it since I have used it a lot. The equations are well-known but I am too lazy to dig up my old graduate accoustics book and look them up again.

Again, I really appreciate the details and experiences shared here. I think your point about dampening factor resonates with me and I’d add that distortion rating are the two factors that make the biggest difference to me in my experiences. Whether they be “real” or not, the best sound systems I’ve heard were usually powered by amplifiers with very low distortion ratings and high dampening factor ratings.

"Damping"; "dampening" is about getting wet.

We are fairly insensitive to distortion in music, depending on the type of distortion, and unless something is broken the speakers are usually orders of magnitude higher in distortion than the electronics.

Of course, many of my tests were not perfectly measured but it goes back to the difference between something that sounds “right” is really noticeable to me, at least in my mind. This is when I’m listening to any sound system and in many cases not knowing anything about it other than what I hear and then learning about the details afterwards. I would also say that the speakers, placement and tuning are the three biggest factors that lead to great sound in my experiences but I’m really trying to nail down how much of a factor amplification plays.

Speakers and room most certainly have the biggest influence on the sound, with amplification a distant second unless the amplifier is not up to the task. An underpowered amplifier that is clipping, one with high noise level, or one with high enough output impedance that it changes the expected frequency response of the speakers are common issues when folk really do need a different amplifier.

A lot of what I’m hearing here seems to imply most people are saying the amplification doesn’t matter as long as you have the amount needed to drive your speakers at the desired levels. I just can’t wrap my head around that yet and find it hard to believe that you all are happy running swap meet amplifiers in your systems. Are you saying there should be no difference between a receiver, running separates, or different amplifiers as long as they are producing similar power under similar loads?

The answers are usually (should be) qualified by all sorts of stuff I and others have been saying. It is not just power, but the amount and type of distortion, noise level, output impedance, input sensitivity/gain, and less tangible things like build quality, warranty, and so forth all factor into choosing an amplifier. IMO there is a bias here for performance, such as Benchmark's AHB2 and similar amplifiers that exhibit outstandingly low distortion and noise, that clearly outperform any AVR I have read about. But how much of the difference is audible is up for debate; many people would be astounded to discover how little difference in sound there is among competent amplifiers driving typical speakers at levels well within the amplifiers' power range. But there are always exceptions, difficult speaker loads, noisy amplifiers, etc. that lead to marketing that "everybody" has systems that are above average and represent extreme cases requiring only the best (or at least most expensive) amplifiers on the planet.

In practice, the answer to your last question is "yes" more often than people think, even among amplifiers considered widely disparate like tube and solid-state designs (not all tube or SS amps, natch). But I have added amplifiers to an AVR that was clearly not up to the task of driving an array of inefficient low-impedance speakers, and also experienced the case of finding no difference between the sound of a different AVR driving the same speakers with and without an amplifier. Easily measurable in both cases. If one amplifier produces (or is rated for) the same power but >1% distortion whilst the other is delivering the same power at 0.1%, you may tell the difference. Similarly if one amplifier's output impedance is a few ohms (e.g. a tube amplifier) and the other is a SS amp with output impedance <0.1 ohms, again you may be able to tell a difference in frequency response for certain speakers. The problem is figuring out what we actually hear versus what we think or what to hear, and that is where controlled testing becomes so important. I have on many occasions been sure of the difference between two components, only to discover there was none I or others could hear in a blind test. And almost as often discovered differences I did not expect among similar components. Life goes on.

Whatever - Don