So how does it sound without the Power Amp ?

rccarguy2

Distinguished Member
Remind me again @Mr Wolf, how does sensitivity on a 4 ohm speaker relate to sensitivity on an 8 ohm speaker?

They don't. They're two seperate values

dB is sensitivity how much a give watt results in a dB output.
Ohm is indendence, how much load is seen by the amp, harder to drive requires heftier PSU and will result in more heat from output gets. A perfect amp will be able to double watt output every halving ie from 8 to 4 should be 100w and 200w respectively.
 

rccarguy2

Distinguished Member
Also speakers aren't 8ohm across the frequency range, so a 8 ohm speaker could drop to low impedance at lower frequencies. One of kef speakers about 2 ohm lower down
 
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Deleted member 901590

Guest
As @Mr Wolf has tried to reiterate in the thread already, the ACD measured figures can be and indicators of overall available power but, mostly, are a waste of time.

How they can be an indicator is as follows. (All at 1% THD) My power amp measures around 120ish wpc 5 channels ACD. It measures 150ish wpc (1% THD) with two channels. The reason the ACD figures is handy is that it tells me in a freak LCR peak (89dB LR, 90dB C sensitivities) it would probably bang 150ish wpc to all three as the surrounds (91dB sens) wouldn't be asking for bugger all watts simultaneously. As you all know, the surrounds cannot demand the same peaks.

So, the ACD figure at least gives a pointer towards what the total delivery can be.

Another, rather picky point, in the x4000 series Denons the amplification/PSU changed from x4300 onwards when they added two more internal amps to make it 9 channel amplifier. This thread keeps quoting ACD power figures for the x4200 at SoundandVision. The x4300 onwards would be very close to the equivalent 9 channel Marantz SR7011 onwards that tested as such:

1643702696655.png


As the wise Wolf has touched on, there are many other factors (most that I wouldn't understand, as I don't know enough about amplifier design) that affect its ability to hit peaks, adjust to speakers phase and variance in impedance and overall sound quality.

Two of these as an example:

One, a comparison of the delivery into 8 Ohms versus into 4 Ohms. See the post here:

My power amp measures (as above) 150ish wpc 8 Ohms but then nearly 260 wpc in 4 Ohms. As a percentage, this well exceeds my AVR.

Another example is the onboard capacitance. I believe the AVR-X4400 onwards has 30,000µF held by two caps. My power amp is 96,000µF spread across 8 caps. Don't forget that capacitors generally degrades over time.

Again, there is much more deep science to these comments, which I am more than aware of.
 
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Deleted member 901590

Guest
It's about budget I already had decent 100w stereo amps pretty much all round, something like eight boxes, wanted to decrease number of boxes, no point downgrading to budget multi channel,.

That could be read as a little misleading. For example, using 7x100wpc power amps versus one IOTAVX, there are so many variables involved here that I do not think anyone can make the sweeping statement that the IOTA would be a downgrade.

The number one potential advantage of the multi-channel amp is that the power supply is shared, instead of separate. Given our understanding of the power peaks that could occur in any known AV setup of those amplifiers, the multi-channel amp has the ability to draw more power for the LCR.

I'm not saying which is better and and don't think anyone could - far too many variables.
 

SeanBrothers

Active Member
One, a comparison of the delivery into 8 Ohms versus into 4 Ohms. See the post here:

if you're looking at 4-Ohm speakers like these Arendals, when considering power I think it's better to consider 4-Ohm power ratings and knock 3dB of their sensitivity as their ratings are taken at 2.83v which 2W into a 4-Ohm load, not 1W.

This is what I was asking about! Thank you @Dobbyisfree (and, of course, @Mr Wolf)!
 
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Deleted member 901590

Guest
It's a very good point and the answer to this explains why a 30W/channel stereo audiophile amp can sound so much better than a 150W/channel flagship AVR or a 300W HT power amp when playing music.

My understanding is that it's to do with how an amp has been designed to deliver sufficient current in the face of difficult loads (i.e. high phase angles) so things like PSU, capacitance, output devices, transistors, rectifiers etc. all matter. Some AVRs will be designed much better in this area than others, even though they may have similar wattages. It's why an X8500 can sound much better than some of the lesser D&M models.

So the less great an amp is at handling difficult loads the more it makes sense to use it with easy to drive speakers. In my book, that's >89dB sensitivity for LCRs, 8-ohm nominal rated and no impedance dips under 4-Ohms in the critical 80Hz-400Hz region that has the loudest and longest peaks above the crossover point.

I've talked about some of this as well in post 54.

Love your point about the 30wpc audiophile amp though.

Isn't it interesting, if you look up quite a lot of the NAD AVRs and multi-channel power amps do not boast high peak wpc figures. I think we know there's probably a reason for this.
 

Harkon321

Well-known Member
@Mr Wolf

You stated that at -10db, my MK IW150 would only be pulling about 5W. Does this, by any chance increase exponentially as you approach -0db?

-10db is actually fine, but above that is where I think there is an issue. (Usually when I'm trying to demo something)
 

Mr Wolf

Well-known Member
Remind me again @Mr Wolf, how does sensitivity on a 4 ohm speaker relate to sensitivity on an 8 ohm speaker?
Strictly speaking, speaker sensitivity is not impacted by impedance at all as speakers are voltage driven devices and all sensitivity ratings are is a measurement of their SPL output at 1 metre when they are fed 2.83V.

As most speakers are 8-Ohm nominally rated, 2.83V was adopted for the rating because it's the voltage required when to generate 1 watt of power into an 8-Ohm load [P=(V^2)/R]. You can see from the formula that, when fed into a 4-Ohm load, 2.83V produces 2W of power. As doubling power increases SPL output by 3dB, arguably a 4-Ohm speaker's sensitivity rating needs to be de-rated by 3dB for comparison with 8-Ohm speakers as it requires twice as many watts to produce the same SPL. This is why 4-Ohm speakers are generally considered harder to drive than 8-Ohm ones.

But these impedance ratings are just nominal values, a bit like an average but less objective. In practice, most good speakers' impedance level fluctuates from about 3 to 30 Ohms across its entire frequency range and many manufacturers overstate their nominal ratings to make them look easier to drive on paper.

The thing to really care about is the speaker's impedance and phase angle around 120-250Hz, as this is where they have their lowest impedance dips in a region that contains a high amount of sound energy (i.e. longest, loudest transient peaks).

As an example, this is the impedance/phase angle to frequency chart for my 8-Ohm rated main speakers published by Stereophile. The red line shows, from an impedance standpoint, the most "difficult to drive" frequency is 200Hz where impedance is 4.2-Ohms. Fortunately it has a very shallow phase angle at this point but due to the impedance it will still be drawing about twice the amount of power than it would under an 8-Ohm load. Due to this low point, I’m more interested in my amplifier‘s power output capability at 4-Ohms, especially those measured on a burst/dynamic power basis as this better reflects the demands of real world material.
1643669808303.png


Speaker phase angles impact amplifier efficiency. The worst possible phase angle a speaker can have is about 45° which can double the amount of current required from the PSU due to extra heat losses (blue line shows it’s 45° at 800Hz where impedance is fortunately a relatively benign 9.3 Ohms). So you never want a high phase angle coinciding with a low impedance dip, especially in a high energy frequency region. A good speaker designer will ensure this doesn’t happen.

Sorry, this is probably far more info than you were expecting but it’s a really important subject and understanding it enables better speaker/amp purchasing decisions which is of course why charts like the above get published. It’s far too simplistic to just think of speakers in terms of their nominal impedance ratings.

Too many people around here are obsessed with adding more amplifier power without even thinking about what creates the need for that power. IMO, in many cases they would be far better off investing in more sensitive, easier to drive speakers as this can have a far greater impact on a system’s performance.
 
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Deleted member 901590

Guest
To elaborate further on the post above, have a look at the comparison in the link to a post below, this further strengthens the importance of choosing the type of speaker that is right for you and your room:

 

Mr Wolf

Well-known Member
@Mr Wolf

You stated that at -10db, my MK IW150 would only be pulling about 5W. Does this, by any chance increase exponentially as you approach -0db?

-10db is actually fine, but above that is where I think there is an issue. (Usually when I'm trying to demo something)
It sure does, -5db volume requires 3.2x the power of -10dB, 0B volume requires 10x the power. Most AVRs can cope with -10dB easily unless they’re driving very inefficient speakers.

I’ve never listened higher than -5dB but my AVR (running 7.2) sounds absolutely fine that high but then it‘s still only using <10W per channel at that level due to the high in-room efficiency of the speakers.
 

rccarguy2

Distinguished Member
That could be read as a little misleading. For example, using 7x100wpc power amps versus one IOTAVX, there are so many variables involved here that I do not think anyone can make the sweeping statement that the IOTA would be a downgrade.

The number one potential advantage of the multi-channel amp is that the power supply is shared, instead of separate. Given our understanding of the power peaks that could occur in any known AV setup of those amplifiers, the multi-channel amp has the ability to draw more power for the LCR.

I'm not saying which is better and and don't think anyone could - far too many variables.

Multiple audiolab 8000px versus iota would be a downgrade. With multiple stereo amps, demand on one pair won't effect the others
 

SeanBrothers

Active Member
Sorry, this is probably far more info than you were expecting but it’s a really important subject and understanding it enables better speaker/amp purchasing decisions which is of course why charts like the above get published. It’s far too simplistic to just think of speakers in terms of their nominal impedance ratings.
No apologies necessary! I appreciate the why to the what!

Unfortunately, all I have to work with is "Nominal impedance: 4 Ω; minimum 3.4 Ω" and "Sensitivity: 85 dB at 2.83 v/1m" for my speakers. There is no phase angle data that I've seen. It's all academic since I have the speakers and I like them. But I've been curious about how close the power I have in my system is to my needs.
 

rccarguy2

Distinguished Member
No apologies necessary! I appreciate the why to the what!

Unfortunately, all I have to work with is "Nominal impedance: 4 Ω; minimum 3.4 Ω" and "Sensitivity: 85 dB at 2.83 v/1m" for my speakers. There is no phase angle data that I've seen. It's all academic since I have the speakers and I like them. But I've been curious about how close the power I have in my system is to my needs.

Low sensitivity and low impedance. Need a good amp high power big PSU
 

Mr Wolf

Well-known Member
No apologies necessary! I appreciate the why to the what!

Unfortunately, all I have to work with is "Nominal impedance: 4 Ω; minimum 3.4 Ω" and "Sensitivity: 85 dB at 2.83 v/1m" for my speakers. There is no phase angle data that I've seen. It's all academic since I have the speakers and I like them. But I've been curious about how close the power I have in my system is to my needs.
If you want, I can estimate this for you if you give me the following:

  • Distance to LCR speakers from MLP
  • Room volume (ft3)
  • Maximum listening level with a reference source (e.g. DVD, Blu-ray) - this assumes your system is calibrated to 0dB volume being reference level, not all are.
  • Model of AVR/amp

I assume your quoted speaker specs are for the LCR speakers. If not, I’ll need those too.

Maybe create your own thread for this (or PM me) as, while its related, we‘re a bit off topic from Dodge’s AVR vs PA experiment.
 
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Deleted member 901590

Guest
@DodgeTheViper I've heard you now have an Anthem power amp of some sort. Please, it would be really interesting at some point when you have the time, to do the initial assessment you did in this thread again and comment. :)
 

rccarguy2

Distinguished Member
@DodgeTheViper I've heard you now have an Anthem power amp of some sort. Please, it would be really interesting at some point when you have the time, to do the initial assessment you did in this thread again and comment. :)


Buy this!

 

DodgeTheViper

Moderator
@DodgeTheViper I've heard you now have an Anthem power amp of some sort. Please, it would be really interesting at some point when you have the time, to do the initial assessment you did in this thread again and comment. :)
You mean go through those same scenes and put myself through it again ? :eek:

Ok, I actually did just that :D And my ears were thankful, especially with JW 2 :thumbsup:

This time it was a lot smoother, right up to -5.0db, with the sense that it could go higher without any particular issue. Even with that volume there was no loss of detail while retaining full on dynamics and no walking out with a busted head.
A little different with lower volume as well. Like a little livelier or dynamic without thinking that I need to whack the volume up for the enjoyment.

My mrs didn't know the new amp was in and after watching a movie on Saturday, she asked if i'd changed anything. Her comments were that it sounded more powerful and precise. Fair play to her :D
 

sebna

Well-known Member
You mean go through those same scenes and put myself through it again ? :eek:

Ok, I actually did just that :D And my ears were thankful, especially with JW 2 :thumbsup:

This time it was a lot smoother, right up to -5.0db, with the sense that it could go higher without any particular issue. Even with that volume there was no loss of detail while retaining full on dynamics and no walking out with a busted head.
A little different with lower volume as well. Like a little livelier or dynamic without thinking that I need to whack the volume up for the enjoyment.

My mrs didn't know the new amp was in and after watching a movie on Saturday, she asked if i'd changed anything. Her comments were that it sounded more powerful and precise. Fair play to her :D
Which amp did you get Dodge?
 
D

Deleted member 901590

Guest
You mean go through those same scenes and put myself through it again ? :eek:

Ok, I actually did just that :D And my ears were thankful, especially with JW 2 :thumbsup:

This time it was a lot smoother, right up to -5.0db, with the sense that it could go higher without any particular issue. Even with that volume there was no loss of detail while retaining full on dynamics and no walking out with a busted head.
A little different with lower volume as well. Like a little livelier or dynamic without thinking that I need to whack the volume up for the enjoyment.

My mrs didn't know the new amp was in and after watching a movie on Saturday, she asked if i'd changed anything. Her comments were that it sounded more powerful and precise. Fair play to her :D

Interesting, thank you. Do we gather that's an MCA 525 or the 325 just for LCR?

Any particular reason you chose it out of interest?
 

DodgeTheViper

Moderator
Which amp did you get Dodge?
Anthem MCA 525
Interesting, thank you. Do we gather that's an MCA 525 or the 325 just for LCR?

Any particular reason you chose it out of interest?
A few reasons tbh. Comparing a few specs and features, physical size, wanting to move away from Emotiva, and then online reading.
 

rccarguy2

Distinguished Member
Be interesting if you can tell the difference with side/surrounds between the two..it's one thing for LCR bit noticeable on other speakers during a movie?
 

mossym

Distinguished Member
No issues particularly. I just wanted to try something else.
i hear that, you know from your other thread i was watching this intently with a similar view in mind, absolutely nothing wrong with the emotiva i have, XPA-3 with 275W into 8ohms, so no shortage of power, but having picked up the AVM-70 the itch was there to pair it with an Anthem amplfier as well. I suspected you would like the Anthem, i would have been surprised if you had been disappointed.

scratching the itch myself now as well, not in the same way as you with the MCA-525 but with another 5 channel Anthem power amp i know you were aware of. added bonus for me is i will now be able to move from 3 boxes to 2, replacing the 3 channel emotiva with a 5 channel anthem will allow me to remove the rotel 1066 i was using for one of my atmos pairs, that can now get powered from my 7 channel Bas-x while the anthem will take the front 3 and side surrounds
 

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