Adding an external amp to an AVR - placebo or am I actually hearing a difference

[ConfusedAF]

Hey everyone – greetings from South Africa.

I know this has been asked many times before. I've read through a bunch of threads, but I haven't found a satisfying answer yet. The opinions I'm getting are all over the place, so I'm not sure who to trust.

Here's my setup:

• Denon AVR-X4500H running a 6-speaker configuration
• Fronts: Bentley FS250s (200W, 6Ω, 32Hz–25kHz, 92dB sensitivity)
• Rears & ceilings: nothing fancy
• Sub: SVS SB1000

The system is 99% for music listening. I've calibrated with A1 EVO and usually listen in Neural X (all speakers playing – I know some might consider that sacrilege).

Coming from Logitech Z680s, I was absolutely ecstatic with this setup. I never knew music could sound this good.

But I got curious: would an external amp help? Many people say that if it's not distorting, an external amp won't make a difference.

I figured the only way to know was to test it myself. So I bought a second-hand Marantz MM7025 (140W x 2)
I bi-amped it to my fronts – the amp handles the bass, while the AVR still covers mids and tweeters.
My plan was to try it out, and if the difference wasn't significant, sell the amp and upgrade something else (like a second sub).

I was expecting a small improvement. But honestly, I feel like I'm hearing a substantial difference.

It seems like my AVR was holding the FS250s back – I definitely wasn't getting their full potential. The fronts felt throttled before. Now the soundstage feels wider, more "effortless." And that's saying something, because I was already thrilled with the old sound.

Bass is tighter and better integrated. Even lyrics are clearer – which I really didn't expect. Everything feels like it's been turned up to 11.

After calibrating, I listened to music for five hours straight. Songs I've heard hundreds of times sounded different – better. I could hear audible differences in almost every track. Some lyrics in dynamic songs that I'd long assumed were just inaudible suddenly popped out.

So here's my question: Am I actually hearing a real difference, or is it placebo – all in my head?

I asked this on a local forum and got wildly different answers. Some agreed with my findings. Others said I'm basically full of it – that the amp only adds extra gain, and what I'm hearing is just loudness bias.

I'm hoping for a more scientific answer here. I'm not looking for validation – just a better, more nuanced explanation. If it's just confirmation bias, please tell me straight.

Thanks.

 

[Oddball]

Hey everyone – greetings from South Africa.

I know this has been asked many times before. I've read through a bunch of threads, but I haven't found a satisfying answer yet. The opinions I'm getting are all over the place, so I'm not sure who to trust.

Here's my setup:

• Denon AVR-X4500H running a 6-speaker configuration
• Fronts: Bentley FS250s (200W, 6Ω, 32Hz–25kHz, 92dB sensitivity)
• Rears & ceilings: nothing fancy
• Sub: SVS SB1000

The system is 99% for music listening. I've calibrated with A1 EVO and usually listen in Neural X (all speakers playing – I know some might consider that sacrilege).

Coming from Logitech Z680s, I was absolutely ecstatic with this setup. I never knew music could sound this good.

But I got curious: would an external amp help? Many people say that if it's not distorting, an external amp won't make a difference.

I figured the only way to know was to test it myself. So I bought a second-hand Marantz MM7025 (140W x 2)
I bi-amped it to my fronts – the amp handles the bass, while the AVR still covers mids and tweeters.
My plan was to try it out, and if the difference wasn't significant, sell the amp and upgrade something else (like a second sub).

I was expecting a small improvement. But honestly, I feel like I'm hearing a substantial difference.

It seems like my AVR was holding the FS250s back – I definitely wasn't getting their full potential. The fronts felt throttled before. Now the soundstage feels wider, more "effortless." And that's saying something, because I was already thrilled with the old sound.

Bass is tighter and better integrated. Even lyrics are clearer – which I really didn't expect. Everything feels like it's been turned up to 11.

After calibrating, I listened to music for five hours straight. Songs I've heard hundreds of times sounded different – better. I could hear audible differences in almost every track. Some lyrics in dynamic songs that I'd long assumed were just inaudible suddenly popped out.

So here's my question: Am I actually hearing a real difference, or is it placebo – all in my head?

I asked this on a local forum and got wildly different answers. Some agreed with my findings. Others said I'm basically full of it – that the amp only adds extra gain, and what I'm hearing is just loudness bias.

I'm hoping for a more scientific answer here. I'm not looking for validation – just a better, more nuanced explanation. If it's just confirmation bias, please tell me straight.

Thanks.

The only objective way to compare is to measure. If the response with amp measures better, that would prove that your amp is worth it.

Absent that, it is difficult to tell. If you like the way it sounds and not regretting your purchase vs the overall budget, then I would not keep wondering but just enjoying the new setup.

Otherwise, can't say much but love my 7 amps and would not want to go back to AVR, although pretty sure it could do a jolly good job.

 

[RandomEar]

It's very unlikely that there would be an audible difference between the AVR and a stand alone amp. Blind tests in the 80s already showed that people fail to hear differences between amps. Doesn't mean all amps sound the same - you can sure buy "colored" tube amps and non-transparent transistor amps from certain boutique manufacturers. But that's not what you are using right now.

Disregarding the typical problems of sighted testing, the differences you report are consistent with you either listening louder now to "really test out the new amp", or there being some shift in level between the tweeters and the bass drivers due to a calibration error in your bi-amping setup.

So the first thing I would check is if the voltage at the speaker terminals of your bi-amped front units is identical. Use a test tone (400 Hz is fine) and a multimeter. Don't use a mic.

 

[thcdru2k]

You definitely are hearing something different ...you said it sounds like turned up 11. But no way to know if it sounds different unless you precise gain match two different amps down to the decimal of dB. Slight dB mismatch can make one amp sound better. That being said I use dedicated amps exclusively but I am pretty confident what I am hearing as improvement is just difference in volume or bias due to extra money spent.

 

[delta76]

X4500h is a beefy avr and it can drive your speakers no problem. Enjoy

 

[popej]

If external amp has different gain than internal, then biamping changes playback characteristic. Calibration can comensate, but it is difficult to estimate how well. Testing output voltages would give more informations.

 

[Chrispy]

Not a lot of difference between the avr's onboard amps vs that Marantz unit so I lean towards a setup issue in the addition of the external amp/passive bi-amping thing. You re-ran Audyssey after adding the external amp? Were you doing the passive I've not found passive bi-amping to be a difference in itself, either, so could be expectations in doing that if not setup/gain issue. I have a few Denon avrs I've used with a variety of external amps, and only get a difference when I get well out of the avr's amp range...and it takes a doubling of power just to gain 3dB, and the change from 125wpc to 140wpc isn't significant.....how loud are you listening, how far away are the speakers from your listening position?

 

[ConfusedAF]

It's very unlikely that there would be an audible difference between the AVR and a stand alone amp. Blind tests in the 80s already showed that people fail to hear differences between amps. Doesn't mean all amps sound the same - you can sure buy "colored" tube amps and non-transparent transistor amps from certain boutique manufacturers. But that's not what you are using right now.

Disregarding the typical problems of sighted testing, the differences you report are consistent with you either listening louder now to "really test out the new amp", or there being some shift in level between the tweeters and the bass drivers due to a calibration error in your bi-amping setup.

So the first thing I would check is if the voltage at the speaker terminals of your bi-amped front units is identical. Use a test tone (400 Hz is fine) and a multimeter. Don't use a mic.

Thank you very much for the reply.
Just to make sure I understand you correctly.
I should measure the voltage at the speaker terminals.
1. With just the AVR powering the speakers, and the terminals bridged.
2. Biamped - With the AVR powering the mids (And highs) and the external amp powering the low freq - without the terminals bridged - measuring at the low freq terminal?

If the voltage is the same - then it means I'm not running out of power and the external amp isn't adding anything?

 

[ConfusedAF]

Not a lot of difference between the avr's onboard amps vs that Marantz unit so I lean towards a setup issue in the addition of the external amp/passive bi-amping thing. You re-ran Audyssey after adding the external amp? Were you doing the passive I've not found passive bi-amping to be a difference in itself, either, so could be expectations in doing that if not setup/gain issue. I have a few Denon avrs I've used with a variety of external amps, and only get a difference when I get well out of the avr's amp range...and it takes a doubling of power just to gain 3dB, and the change from 125wpc to 140wpc isn't significant.....how loud are you listening, how far away are the speakers from your listening position?

Keep in mind - I'm Bi-amping - so theoretically I've got 265w on tap - so more than double the power

 

[popej]

2. Biamped - With the AVR powering the mids (And highs) and the external amp powering the low freq - without the terminals bridged - at the low freq terminal?

This one. But details seems tricky, because of Audyssey correction.

Keep in mind - I'm Bi-amping - so theoretically I've got 265w on tap - so more than double the power

Amps share the power, but together you won't get more, than every one of them can provide alone. They are voltage limited.

 

[RandomEar]

Thank you very much for the reply.
Just to make sure I understand you correctly.
I should measure the voltage at the speaker terminals.
1. With just the AVR powering the speakers, and the terminals bridged.
2. Biamped - With the AVR powering the mids (And highs) and the external amp powering the low freq - without the terminals bridged - measuring at the low freq terminal?

If the voltage is the same - then it means I'm not running out of power and the external amp isn't adding anything?

Number 2. Test tone playing, multimeter in AC mode. You don't want to know the absolute level, because I assume that Audyssey tuned that for each group of speakers. The question is if both amps deliver the exact same voltage, because if not, you unwillingly did some "EQ" and reduced or increased the treble/mids compared to the bass.

As pointed out by @popej, you don't have the full 265 W on tap. The voltage limit is one thing, the other is that the bass driver may need more than the available 145 W when pushed while the mid and tweeter combo may still be sipping just 30 to 50 W. That's one of the reasons why bi-amping doesn't give you a significant power advantage.

 

[dualazmak]

Just for your possible reference and interest, let me share my similar subjective experience.

Not an AVR amplifier/processor, but I once intensively and subjectively tested YAMAHA MX-A5200 (class-AB) 11-channel AV amplifier in comparison with my ACCUPHASE E-460 integrated amplifier, as I shared here #175 on my project thread. (As for the specifications etc. of MX-A5200, please refer to #164-#168, #170-#171).

That evaluation of MX-A5200 (in June 2020) was the very first step of my long and intensive amplifier exploration journey in my PC-DSP-based multichannel multi-SP-driver multi-amplifier fully active audio system; you can find the summary and tentative/provisional decision of amplifier selections in my post #311, and you would also please find details of the latest total system setup here #931 and #1,009.

 

[ConfusedAF]

Thanks for the replies folks
Please forgive me ignorance - I'm just trying to understand a couple of things.
1. So, by biamping - the Denon doing the mids, then using the preouts to the Marantz, which then is wired separately to the bass drivers - I'm not effectively getting the combined power of both amps, it's still limited to 140w?

2. If a speaker is not distorting, then more power won't improve anything? It won't be able to play lower, improve transient response, or damping?

3. Adding more power would just enable me to play louder? If I don't listen at higher levels, then it's effectively worthless?

4. With the voltage measurement - should I not be measuring both (With and without a separate amp #1 & #2 scenario above) - so that I can compare?

 

[KenMasters]

@ConfusedAF - You never did respond to my answer on the SA AVForum. Did you ever use your UMIK-1 to compare the response across configurations?

 

[ConfusedAF]

@ConfusedAF - You never did respond to my answer on the SA AVForum. Did you ever use your UMIK-1 to compare the response across configurations?

Hey Ken
My apologies - that thread ended up being derailed.

I actually did end up testing responses on both configurations.
Both responses were identical - but - and this is only my uneducated understanding - I was only able to test one speaker playing at a time.
Wouldn't that effectively mean that the AVR isn't being stressed as it would normal be driving all speakers?

 

[KenMasters]

Hey Ken
My apologies - that thread ended up being derailed.

I actually did end up testing responses on both configurations.
Both responses were identical - but - and this is only my uneducated understanding - I was only able to test one speaker playing at a time.
Wouldn't that effectively mean that the AVR isn't being stressed as it would normal be driving all speakers?

If both responses were level and identical, it suggests your impression is placebo.

There really isn't much between the two amps. I would suggest though that you not bi-amp and power the L & R speakers with the external amp, since you have it already, and forget about it.

 

[Spkrdctr]

I have to agree with KenMasters post above. Your description of what you heard is EXACTLY what almost everyone describes when they audio test with their ears (and brain). It is not accurate at all. I think with the system you have you can just use it as you now have it and don't bother selling the newer amp. You are not hurting anything. But you are not most likely gaining anything UNLESS you listen to movies? at exceptionally loud levels. As others have stated if you AVR amp is not being pushed hard, then the adding an amp really does nothing. But if you think it sounds better you can use your ear/brain effect telling you it is better to listen to what YOU perceive as a better system. So, go with your ears even if it is not "correct" and enjoy! If you want another sub, go for it. That is the fun of the hobby.

 

[delta76]

Thanks for the replies folks
Please forgive me ignorance - I'm just trying to understand a couple of things.
1. So, by biamping - the Denon doing the mids, then using the preouts to the Marantz, which then is wired separately to the bass drivers - I'm not effectively getting the combined power of both amps, it's still limited to 140w?

2. If a speaker is not distorting, then more power won't improve anything? It won't be able to play lower, improve transient response, or damping?

3. Adding more power would just enable me to play louder? If I don't listen at higher levels, then it's effectively worthless?

4. With the voltage measurement - should I not be measuring both (With and without a separate amp #1 & #2 scenario above) - so that I can compare?

Yes more power means louder. But you need double power to increase loudness 3dB, which is why the first 10w is critical but after that it gets less and less impactful the more power you throw at it. From 1 to 100w you get 20dB increase but from 100w to 200w only 3dB!

Unless you have a very difficult to drive speaker, or if you have money to spend (which is likely not the case as you would have a x4800h), an amp is not needed. Just save money to buy better speakers

 

[Chrispy]

Keep in mind - I'm Bi-amping - so theoretically I've got 265w on tap - so more than double the power

You are passive bi-amping, there's a slight electrical advantage but not much, it is not additive like that at all. The mids/tweeters likely are doing just fine with no more power without blowing, and how direct it is wired to the bass driver varies and still isn't that important generally. Usual recommendation is simply use a more powerful amp if you need one. The concept is more about selling more wire in the bi-wiring/passive bi-amping scenario. Active bi-amping is a different subject, and has much more value.

Try this thread https://www.audiosciencereview.com/forum/index.php?threads/bi-amping-101.22817/
Maybe this article https://www.audioholics.com/frequent-questions/the-difference-between-biamping-vs-biwiring

ps did you re-run Audyssey to match the external amp to the avr?

 

[RandomEar]

Thanks for the replies folks
Please forgive me ignorance - I'm just trying to understand a couple of things.
1. So, by biamping - the Denon doing the mids, then using the preouts to the Marantz, which then is wired separately to the bass drivers - I'm not effectively getting the combined power of both amps, it's still limited to 140w?

You can't double the power even in ideal scenarios, because the crossover is not perfectly steep. So each amp has to drive a bit of an overlap region above/below the crossover freq. More about this here. It's a good read.

Your Denon delivers 165 W @ 6 Ω for the front channels. The Marantz does 170 W @ 6 Ω per channel. So they're effectively the same and deliver about the same peak RMS voltage (31.5 V). The only thing you could gain would be more amps. But to deliver additional amps into the same speaker load, you would need higher voltages on both amps, which you can only get with two more powerful amps to begin with. At least assuming that your Denon doesn't have any problem delivering the required amps to all five connected passive speakers at the same time, which depends on the total available amps of the internal PSU.

The power distribution between tweeter+midrange and woofer also isn't 50/50. For simpler two way systems, I have seen numbers of about 20%/80%. In your case, it may be closer to 40/60 due to the mid being combined with the tweeter - or it may be around 30/70, who knows. It depends on the crossover design and the efficiency of the individual drivers. So even disregarding the voltage limitation and the crossover overlap losses, you will never double the available power because the tweeter/mid drivers didn't eat exactly 50% of your power budget to begin with.

2. If a speaker is not distorting, then more power won't improve anything? It won't be able to play lower, improve transient response, or damping?

Mostly. Looking at it the simplest way, there are two upper limits: The speaker driver cones bottoming out or tearing and your amp clipping due to reaching the voltage limit. If you heard speaker cones hitting something using only the AVR, you had more than enough power. If you reached the clipping point of the AVR, you lacked power. If you had neither of those problems, you lacked courage In the latter case, there's nothing to gain by adding power.

3. Adding more power would just enable me to play louder? If I don't listen at higher levels, then it's effectively worthless?

Yeah.

4. With the voltage measurement - should I not be measuring both (With and without a separate amp #1 & #2 scenario above) - so that I can compare?

You could measure both setups. But assuming that the AVR isn't clipping at your normal listening level, the voltage on its terminals shouldn't change between the setup scenarios. So only comparing the voltage on both terminals of the front speakers for the bi-amped scenario should be OK, as far as I'm not missing something.