I'm all for simplification but I don't think the 3800 (and not even the 4800) could handle the 3 front channels' 4-ohm load on its own.
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Denon AVR-X3800H Review
- Thread starter amirm
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I'm all for simplification but I don't think the 3800 (and not even the 4800) could handle the 3 front channels' 4-ohm load on its own.
Karls_speaker_works
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My X3800 seems to handle my Martin Logan Sequels (L-R) + Motion 6 (Center - 4 ohms) just fine. The plot below is the impedance curve of the Sequels. They are below 4 ohms from 50 - 600 Hz (~2.6 ohms @ 400Hz), then below 4 ohms from 9 - 50 kHz, below 2 ohms from ~ 17 to 50kHz. I'm also driving 4 ohm ADS 400i ceiling speakers for rear height and Cambridge Soundworks satellites (6 ohm?) for front heights. The surrounds are self-powered. I can achieve 100 dBC SPL levels while pushing the output to it's maximum of +6dB (-80 - +18dB scale - max level depending on tactile transducer level.) Room is 12' x 14' x 8-12' lofted ceiling + loft area over adjacent room. The amplification in the X3800 hasn't complained or even sounded terribly congested at those levels, though admittedly I don't run at such volumes for more than 10-20 seconds at a time.
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I will definitely keep this in mind once the 3800 is in hand. I could always use the XPA2 for a separate zone...
tesseractASR
Member
Emo XPA-2 Gen 2 is 500 watts/4 ohm and 300 watts/8 ohms. Wish mine and my XPA-3 Gen 2 weren't 1400 miles away from me in storage.
tesseractASR
Member
I'm going to be trying a MartinLogan Classic 9 and Focus 18 LCR on my 4800 soon. I expect it to be able to handle the 75-85 dB levels I normally listen at, but this is not a recommendation to do so, especially for the 3800. The 4800 can handle a bit more of an impedance drop.
I was just going by the measurements from the Audioholics review since I don't trust manufacturer specs:
Emotiva XPA-2 Two Channel Amplifier Review
The Emotiva XPA-2 is a two-channel amplifier is one of the most powerful, highest value amplifiers we've reviewed to date. It is a lone wolf in a pasture of sheepish amplifiers.
I took the 410W and divided by 2. I think I would concede it might be 410W per channel to a 4-ohm load but not 500W. Independent measurements are why we're here!
Those Gen 2 amps from Emotiva are super heavy. Why are yours in storage?
I would be surprised if there weren't - there is a big gap between the X4800 and the A1H...
With my speakers - I would take your bet...
My Gallo's are 4 ohm nominal, with drops down to 1.6ohm at the tweeters (Some of the ML's have similar impedance dips!) - and although the AVR doesn't shut down, release smoke, or do anything else that is obvious - the sound just doesn't sound right...
Put a beefy power amp in there, capable of driving a 2 ohm load without strain, and the sound improves markedly (in my case I have tried Quad 606, and Crown XLS2500) - past generation flagship AVR's from Onkyo/Integra could handle these same speakers without trouble... but current mass market AVR models (of all brands), don't have power supplies capable of providing enough current to do the job. - I'm pretty sure the A1H could do the job, but I doubt the X4 could do it.
tesseractASR
Member
"That being said, the XPA-2 exceeded its power specifications by considerable margins. Into 8 ohms it was rated to 250 watts at 1% THD , yet I measured 312 watts at 0.1% THD. Into 4 ohm loads it was rated to 500 watts at 1% THD while again my measurements exceeded this rating producing 512 watts at 0.1% THD. Make no mistake folks this is one POWERFUL amplifier and most definitely the most power for the money amplifier that has ever come across my test bench since I launched Audioholics nearly 10 years ago!"I was just going by the measurements from the Audioholics review since I don't trust manufacturer specs:
Emotiva XPA-2 Two Channel Amplifier Review
The Emotiva XPA-2 is a two-channel amplifier is one of the most powerful, highest value amplifiers we've reviewed to date. It is a lone wolf in a pasture of sheepish amplifiers.www.audioholics.com
I took the 410W and divided by 2. I think I would concede it might be 410W per channel to a 4-ohm load but not 500W. Independent measurements are why we're here!
Those Gen 2 amps from Emotiva are super heavy. Why are yours in storage?
That is the Gen 1. The Gen 2 is more powerful, but even the Gen 1 managed 500 watts@4 ohms. I am friends with Gene and the XPA-2, as the article tells us, is partially due to his suggestion. The AH measurements handily exceeded the Emotiva ratings.
I took a job on the East Coast, hurriedly moved away from the home that I still own, into an apartment, bringing only what could fit in my SUV. Put my valuables in storage. Am building a new system here. I'll probably never live in my house again. Will either rent or sell it.
As it is, I will probably need another powerful amp, at least for the front three speakers.
The question I always want to see answered, is what is it like into 2 ohm...?
Speakers that are 4 ohm nominal typically drop down to well below 4ohm at certain frequencies... and many amps start to misbehave at low impedances (rising distortion).
Usually an amp as beefy as that one, will still have plenty left at 2 ohm - but sometimes it can be surprising how much "puff" is lost in lower impedances - my Quad 606, 135W@8ohm, drops down to only 90W @ 2ohm - but remains clean and stable... so it sounds good into low impedance speakers. My Crown XLS2500 is a beast of a different feather - 440W@8ohm, 1200W@2ohm
In actual use, into difficult low impedance speakers, the two sound identical.
But my speakers do tend to quickly sort the wheat from the chaff - speakers that cannot handle low impedances well, are ruthlessly exposed.
tesseractASR
Member
I wonder about 2 ohms, too, but am not terribly concerned about it. I suspect the XPA amps can manage. I've seen AVRs run ML speakers before.
Here is the XPA-2 Gen 2:
A good friend of mine is using two Crown XLS amps, one channel each with the other channel unused, into his ML Classic 9s. I'd like to try it, but need three channels and am not a fan of the AD/DA conversion, even though I am 100% it is inaudible. I looked at their non-DSP units, but they are too noisy.
I'm gonna try it first with just the 4800. I may get back home someday to grab my Emos or I may buy something else and sell those at my earliest opportunity.
If I owned an amp like this one, I would probably feel quite comfortable trying it into 2 ohm speakers...I wonder about 2 ohms, too, but am not terribly concerned about it. I suspect the XPA amps can manage. I've seen AVRs run ML speakers before.
Here is the XPA-2 Gen 2:
A good friend of mine is using two Crown XLS amps, one channel each with the other channel unused, into his ML Classic 9s. I'd like to try it, but need three channels and am not a fan of the AD/DA conversion, even though I am 100% it is inaudible. I looked at their non-DSP units, but they are too noisy.
I'm gonna try it first with just the 4800. I may get back home someday to grab my Emos or I may buy something else and sell those at my earliest opportunity.
The proof of the pudding however... I did try my latest mid-market AVR on my speakers, before connecting my power amps... and the result was not inspiring! - so when the amp is lacking, the results are quite obvious (at least with my speakers).
Flagship AVR's typically have substantially more robust amps, and can handle difficult speakers ( in my case a 2008 Onkyo SR876, and 2013 Integra DTR 70.4 - both handled the speakers fine) - and easy rule of thumb for an amp to tell whether it will have the required current, is to check its weight - unless it is powered by a SMPS (Switch mode power supply) - the current available will be pretty much directly proportional to the weight... my two AVR's that handled the speakers well, both weighed around 50lbs/25kg.... my current AVR weighs 10kg - no surprises that it fails!
So looking at this XPA2 - the rule of thumb is definitely applicable circa 40lbs for a 2 or 3 channel amp...
On the other hand the current Gen3 version specifically states (in the specs) "Minimum Recommended Load Impedance (per channel): 4 Ohms"
So caution would need to be exercised, as the circuit design may not be stable with especially low impedances... (the two flagship AVR's I mentioned above both had "minimum recommended load impedance = 4 ohm" and they worked fine)
Weight can artificially be added to trick old-school audiophiles who swear by that metric. When I bought my Oppo BDP-83 Universal Player, it was critically acclaimed for its performance and quickly duplicated as a digital transport. High-end make Lexicon shortly introduced the BD-30, which was literally the same BDP-83 player put into a brand new casing and marking it up $3000 over the 83's $500 retail price! If you haven't heard this story, you can read about it here:
Lexicon BD-30 Blu-ray Player (Oppo BDP-83 Clone) Review
We discovered the Lexicon BD-30 is an Oppo BDP-83 Blu-ray Player with a $3k premium. We prove this with pictures, measurements and an official response from THX. Lexicon no longer sells this product.
Disclaimer: if you're a fan of THX, this was a very dark day for the company (and a black eye for Lexicon)! Not sure if it's the same @amirm from ASR, but he's mentioned in the article too!
My best metric for amplifier capacity is if you can nearly double the power output into a 4-ohm load vs an 8-ohm load, then you really have something (like the XPA2)!
It may often be the cases, but in many cases if you look carefully, especially if you examine available lab measurements you would find that manufacturers might have played tricks (intentionally or not) by the way they specify their 8 ohm vs 4 ohm outputs.
One easy way is to specify a lower output into 8 ohm so it would appear to almost "double down". That is very easy to do, for example, by just picking different distortions level.
The same amp could be specified in the follow way:
- 120 W 8 ohm 200 W 4 ohm, <1% THD
-150 W 8 ohm, 180 W 4 ohm, <0.1% THD
That's just a simple example, anyone can add and fill in the blanks.
As an EE, if I really want to assess the amp's voltage and current capability, I would try hard to secure a copy of the service manual and wouldn't mind paying for it if not available for free download. Otherwise, I would at least try to find out if there are specs of the power supply (caps, transformer VA info etc.). Weigt, as others mentioned, is a good rule of thumb but not too reliable. Emotiva amps are good example, quite heavy, but don't really have high VA transformers relative to others like Outlaw and Parasound, let alone Krell's.
It may often be the cases, but in many cases if you look carefully, especially if you examine available lab measurements you would find that manufacturers might have played tricks (intentionally or not) by the way they specify their 8 ohm vs 4 ohm outputs.
One easy way is to specify a lower output into 8 ohm so it would appear to almost "double down". That is very easy to do, for example, by just picking different distortions level.
The same amp could be specified in the follow way:
- 120 W 8 ohm 200 W 4 ohm, <1% THD
-150 W 8 ohm, 180 W 4 ohm, <0.1% THD
That's just a simple example, anyone can add and fill in the blanks.
As an EE, if I really want to assess the amp's voltage and current capability, I would try hard to secure a copy of the service manual and wouldn't mind paying for it if not available for free download. Otherwise, I would at least try to find out if there are specs of the power supply (caps, transformer VA info etc.). Weigt, as others mentioned, is a good rule of thumb but not too reliable. Emotiva amps are good example, quite heavy, but don't really have high VA transformers relative to others like Outlaw and Parasound, let alone Krell's.
Agreed that "tricksies" can still be played if you casually ignore the THD numbers (I don't). Another reason why I always wait for independent reviews.
I rarely make poor, uninformed purchases because this hobby ain't cheap!
Yep, I remember that debacle...Weight can artificially be added to trick old-school audiophiles who swear by that metric. When I bought my Oppo BDP-83 Universal Player, it was critically acclaimed for its performance and quickly duplicated as a digital transport. High-end make Lexicon shortly introduced the BD-30, which was literally the same BDP-83 player put into a brand new casing and marking it up $3000 over the 83's $500 retail price! If you haven't heard this story, you can read about it here:
Lexicon BD-30 Blu-ray Player (Oppo BDP-83 Clone) Review
We discovered the Lexicon BD-30 is an Oppo BDP-83 Blu-ray Player with a $3k premium. We prove this with pictures, measurements and an official response from THX. Lexicon no longer sells this product.www.audioholics.com
Disclaimer: if you're a fan of THX, this was a very dark day for the company (and a black eye for Lexicon)! Not sure if it's the same @amirm from ASR, but he's mentioned in the article too!
My best metric for amplifier capacity is if you can nearly double the power output into a 4-ohm load vs an 8-ohm load, then you really have something (like the XPA2)!
And yes getting close to doubling 8 to 4 to 2 is an ideal...
But the engineering challenge leads to some manufacturers under quoting their 8ohm power, so it can appear that it doubles down into 4 ohm.
To me the important spec is a full 2 ohm rating... or support for bridging into 4 ohm speakers... which is the same thing! ( but all too rare )
Just a reminder, one of the design goal of a power amplifier is the output "power" rating. To be more meaningful, it really should have been voltage and current. Since voltage, current and power are all related, they used power to keep things simple and easier to understand by the average consumers.
It follows that, if an amplifier's output specs are voltage limited by design, and not current limited at all, then the amplifier can come close to do the so called "double down", from output into 8 ohm vs into 4 ohm.
If it is current limited by design, and not voltage limited at all, then the amplifier will, instead of double down from 8 to 4 ohm load, it will "half down", based on the well known Ohms law that probably 99% of ASR members are familiar with.
That's obviously the extreme case, in reality, all power amplifiers will be designed to have both voltage and current limits. As such, if an amplifier is specified for 100 W into 8 ohms, it cannot be specified for 200 W into 4 ohms, but should most likely be specified for 50 W into 4 ohms, because for the same current output, the power output will be halved when the load impedance is halved based on Ohm's law and the power formula.
Here's simplified numerical example:
Designed maximum output voltage = 28.28 V, Load resistance = 8 ohms, current = 3.535 amperes, Power = 100 watts
If the designed maximum current is 3.535 A, then for load resistance = 4 ohms, Power = 3.535*3.535*4 = 50 watts
That is, when the resistance (same for impedance) is halved, such as from 8 to 4 or 4 to 3 ohms, power output is also halved, not doubled.
One may say, but how do you know the amp is designed for the same current regardless of the load impedance. Just think about it, supposing the amp used in this example is not 3.535 A, but say, it is designed to for a maximum current of say, 2*3.535 = 7.07 A, then of course the amp could be specified to double down from 100 W 8 ohms to 200 W 4 ohms, since power = 7.07*7.07*4 = 200 W, but then if this is the case, the amp should have been specified for 7.07*7.07*8 = 400 W into 8 ohms!!
In this numerical example, the amp is specified for 100 W into 8 ohms, that means it's maximum current has to be in the neighborhood of 3.535 A and it's output into 4 ohms will therefore be in the neighborhood of 50 W, that is, again, half down, not double down.
The main reasons for amps with power output specs "double down" would include but not limited to the following:
- The output into lower impedance such as 4 and 2 Ohms are based on short duration, minutes, or seconds, milliseconds etc., not literally continuous.
- Use power transformers that have above average overload capability. In general, power transformers is an electrical devices that inherently has excellent overload capability.
- Heat dissipation adequately designed, using passive and/or active cooling.
- Use output devices designed for maximum current into much lower load impedance such as 2 ohms or lower (again, duration for the high current flow considered).
The so called "double down" or close to double down output ratings are NOT unconditional, manufacturers just don't tell you the details in the specifications. They don't have to tell you either because they know full well that you will be using their amps to listen to music, movie sound tracks, not test tones so there is no need for them to design for output currents into 4 ohm or less load. Even for those using speaker rated 4 ohms nominal, with dips to 1.6 ohms, amp manufacturers know such low dips will not likely occurred over a bandwidth more than an octave or two, typically you will see such lowest dips over a very narrow range of frequencies such that the amp will only have to drive the resulting high current spike for a very short duration as the music content dictates, that is, such very high current demand periods are short and of intermittent nature.
The double down from 8 to 4 to 2 ohms requirements, similar to the all channel power output requirements are to a large extent, more myth, or ideal, than necessity. Regardless, the ability to do those things, like 120 dB SINAD vs 90 dB SINAD, are nice, whether we can hear the resulting "better sound quality" or not.
It's very early, and I am too lazy to spell check, so if there typos that may cause confusion or result in distortions/mistakes, please kindly alert me, and I'll do the editing accordingly.
It follows that, if an amplifier's output specs are voltage limited by design, and not current limited at all, then the amplifier can come close to do the so called "double down", from output into 8 ohm vs into 4 ohm.
If it is current limited by design, and not voltage limited at all, then the amplifier will, instead of double down from 8 to 4 ohm load, it will "half down", based on the well known Ohms law that probably 99% of ASR members are familiar with.
That's obviously the extreme case, in reality, all power amplifiers will be designed to have both voltage and current limits. As such, if an amplifier is specified for 100 W into 8 ohms, it cannot be specified for 200 W into 4 ohms, but should most likely be specified for 50 W into 4 ohms, because for the same current output, the power output will be halved when the load impedance is halved based on Ohm's law and the power formula.
Here's simplified numerical example:
Designed maximum output voltage = 28.28 V, Load resistance = 8 ohms, current = 3.535 amperes, Power = 100 watts
If the designed maximum current is 3.535 A, then for load resistance = 4 ohms, Power = 3.535*3.535*4 = 50 watts
That is, when the resistance (same for impedance) is halved, such as from 8 to 4 or 4 to 3 ohms, power output is also halved, not doubled.
One may say, but how do you know the amp is designed for the same current regardless of the load impedance. Just think about it, supposing the amp used in this example is not 3.535 A, but say, it is designed to for a maximum current of say, 2*3.535 = 7.07 A, then of course the amp could be specified to double down from 100 W 8 ohms to 200 W 4 ohms, since power = 7.07*7.07*4 = 200 W, but then if this is the case, the amp should have been specified for 7.07*7.07*8 = 400 W into 8 ohms!!
In this numerical example, the amp is specified for 100 W into 8 ohms, that means it's maximum current has to be in the neighborhood of 3.535 A and it's output into 4 ohms will therefore be in the neighborhood of 50 W, that is, again, half down, not double down.
The main reasons for amps with power output specs "double down" would include but not limited to the following:
- The output into lower impedance such as 4 and 2 Ohms are based on short duration, minutes, or seconds, milliseconds etc., not literally continuous.
- Use power transformers that have above average overload capability. In general, power transformers is an electrical devices that inherently has excellent overload capability.
- Heat dissipation adequately designed, using passive and/or active cooling.
- Use output devices designed for maximum current into much lower load impedance such as 2 ohms or lower (again, duration for the high current flow considered).
The so called "double down" or close to double down output ratings are NOT unconditional, manufacturers just don't tell you the details in the specifications. They don't have to tell you either because they know full well that you will be using their amps to listen to music, movie sound tracks, not test tones so there is no need for them to design for output currents into 4 ohm or less load. Even for those using speaker rated 4 ohms nominal, with dips to 1.6 ohms, amp manufacturers know such low dips will not likely occurred over a bandwidth more than an octave or two, typically you will see such lowest dips over a very narrow range of frequencies such that the amp will only have to drive the resulting high current spike for a very short duration as the music content dictates, that is, such very high current demand periods are short and of intermittent nature.
The double down from 8 to 4 to 2 ohms requirements, similar to the all channel power output requirements are to a large extent, more myth, or ideal, than necessity. Regardless, the ability to do those things, like 120 dB SINAD vs 90 dB SINAD, are nice, whether we can hear the resulting "better sound quality" or not.
It's very early, and I am too lazy to spell check, so if there typos that may cause confusion or result in distortions/mistakes, please kindly alert me, and I'll do the editing accordingly.
I can think of many factors, such as:
- physical design in the layout, if you look at the Denon A1H, and many of the relatively expensive McIntosh's and Luxman amps, EI core Tx might have fit better than Toroids.
- shielding scheme design, in some cases, the designers may prefer toroidal because it is better in terms of lesser less leakage vs EI core ones. Denon custom designed their EI core tx to address the more leakage flux/EMI related issues.
- Cost, on all else being equal basis, toroids are more costly, though all else are usually not equal. Two of my cheapest amp, QSC RMX850a I ever purchased, C$338, about US$260 in 2017, now about USD700!, and my also cheap NAD C326, uses toroids, my vintage Marantz amp uses EI core, that's examples that show cost is not always the factor.
- Weight, also on all else being equal basis, toroids would likely weigh less.
- Start up surge current: toroids typically have much higher inrush currents (again, only if all else being equal), so for larger power amps, it may cost more if the designer has to include some sort of soft start circuitry.
Here's a technical article on the benefits of EI core transformers, for audio amps:
But "7.07*7.07*8 = 400 W into 8 ohms" would only be achievable if the maximum output voltage from your simplified numerical example were doubled (i.e. 56.56 V).
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