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#170658 - 06/20/07 12:31 AM Power into M80s from my cheap Denon
Mojo Online   content

Registered: 01/21/07
Posts: 4622
Yesterday I mentioned that I would attempt to find out how much power I can get from my cheap Denon receiver into a pair of M80s.

A few words about my receiver: it's the Denon AVR-2105 rated at 90W/channel into 8 Ohms with 0.08% distortion and 125W/channel into 6 Ohms with 0.7% distortion. Dynamic power is 200W x 2 channels into 2 Ohms. The receiver cost me $350 a couple of years ago brand new.

So a few words about what I did: I wanted to use the worst possible load the M80s could present to the amp. As shown on the graphs below, this load presents itself at about 50 Hz and is 4 Ohms. At this frequency, the speaker has a resistance of 2.83 Ohms and an inductive reactance of 2.83 Ohms due to the 45 degree phase angle (R=4*cos45, XL=4*sin45). So I injected a 50Hz test tone from the Realtraps CD (thanks again Randy ) and measured the RMS voltage across the speaker terminals. I had both M80s going but I only measured one of them. The real power is ((V^2)/4)*cos(45), the reactive power is the same formula but substitute sin instead of cos. The complex power is the square root of the sum of the squares of the real and reactive.

The data below (see blue column) shows that I could source as much as 306 Volt-Amps (Watts) from the Denon at maximum volume. As I indicate on my notes on the graph, I only applied the test tone for about 5 seconds (long enough to get a reading) because frankly I was scared I might do some damage .

I did not do any distortion measurements as I don't have any equipment to do that. I can tell you though that up to +3 on my main gain knob, the 50Hz tone sounded "good" to me. After +3, I had to stop and put in earplugs. But I watched the M80 drivers a few times after +3 and they looked to be travelling linearly to me.

This tells me a few things:

1. Denon amps deliver! If my bottom-of-the-line unit can do this, I am sure the rest of them can do more.

2. I would certainly not hesitate to run this unit continously at the +3 level. As I've mentioned before, I have left it turned on continously for an hour at maximum volume with music while I left the house with no shut-down (come to think of it now maybe it did shut down and then re-start but it was certainly playing when I got home).

3. This was a test tone at the worst possible frequency. For real music and with a sub, the receiver would never experience these kinds of torturous conditions.

4. I don't know how anyone, in a room that is 4,000 cubic feet or less can possibly listen to any levels approaching 0 on the gain knob. I've listened to some classical at +7 but absolutely no more.

5. If this is the capability of my cheap Denon, what does that say about Odyssey, Emotiva and other more "esoteric" brands? Be careful that you don't fry your M80s!!!

I hope this is helpful to anyone out there looking for an amp. I am sure that the discussions about power will rage on but at least this is some quantitative data that we can draw on.

#170659 - 06/20/07 01:29 AM Re: Power into M80s from my cheap Denon [Re: Mojo]
JohnK Offline
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Registered: 05/11/02
Posts: 10621
Most interesting results under, as you say, extreme conditions that would never occur in ordinary listening(but what was the classical item you listened to at +7, which would be horrendously loud unless the passage in question was very low level itself). In particular, five seconds of 50Hz drawing 216 watts aren't going to happen except on an experimental basis.

Enjoy the music, not the equipment.

#170660 - 06/20/07 01:39 AM Re: Power into M80s from my cheap Denon [Re: Mojo]
na8c Offline
frequent flier

Registered: 06/18/07
Posts: 16
Loc: Texas
i'm newbie but very interesting to know the test you did. Is that mean Denon does a good job? Or M80? coz i'd looked for a NHT absolute Zero (6ohms) for my denon(8ohms), but finally i back to Axiom M3(8ohms). And now im still confusing about the risk of a sound system which seting up with compenents (receiver/speakers)come with diff ohms.


#170661 - 06/20/07 01:51 AM Re: Power into M80s from my cheap Denon [Re: na8c]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10621
Well Mark, the test was mainly of the 2105's capabilities. As I commented, especially at that +15 mark, there's nothing remotely like that in real-world home listening to music or movies, so it speaks highly of the capabilities of the 2105(and I suspect that there're other receivers in that price class that would also do well).

Enjoy the music, not the equipment.

#170662 - 06/20/07 07:53 AM Re: Power into M80s from my cheap Denon [Re: JohnK]
Mojo Online   content

Registered: 01/21/07
Posts: 4622

My apologies. I didn't mean to write +7 but rather -7. Good catch .

#170663 - 06/20/07 09:21 PM Re: Power into M80s from my cheap Denon [Re: JohnK]
jakewash Offline
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Registered: 12/26/03
Posts: 10415
Loc: Calgary, Alberta
Just goes to show you don't have to spend alot to get a good amp. If memory serves, the 2105 only had a about 5 receivers above it and numerous ones below in the Denon line up for 2005. Even though it didn't cost alot I would still consider it an upper middle receiver, certainly not cheap, just inexpensive.


#170664 - 06/21/07 11:01 AM Re: Power into M80s from my cheap Denon [Re: Mojo]
alan Offline


Registered: 01/29/02
Posts: 3256
Loc: Toronto/New York/parry Sound
Hi Mojo,

Excellent testing and I'd agree with you that the Denons, even the inexpensive models and the Sherwood Newcastles will drive the 4-ohm M80s without problems in average-sized rooms.

However--and it's a big "however"--you would really have to put an oscilloscope on the output and monitor the audio waveform to see when the Denon approached or went into clipping. I suspect that may be happening because our detection threshold for distortion with music and soundtrack material has to reach quite gross levels--from 1% to 3%--before we notice a grotty, edgy or nasty edge to the sound quality.

Psycho-acoustic studies have demonstrated this repeatedly. I'll be writing about this subject in an upcoming newsletter article, but what's surprising are the momentary peak power requirements in some music that you'd think wouldn't be demanding.

It's a matter of acoustical "ease" at loud listening levels, even with smaller loudspeakers when they're fed unlimited amounts of power with no clipping. I was testing some Axiom W2 in-wall/on-wall hybrid speakers driven by two older Denon Class A/B monoblocs rated at 250 watts per channel into 8 ohms with no subwoofer running--the tests were double-blind so I had no idea what I was listening to until after the test. I couldn't believe how clean and loud the sound was and how much good bass there was from the two W2's unassisted by a subwoofer.

Later, the tests were repeated again with several different and excellent subwoofers mated to them and the same Denon monoblocs driving the W2s. I wrote down comments like "excellent"; "really transparent and clean"; "very natural and uncolored", "wonderful deep and powerful bass", and "these are great speakers--what am I listening to? M80s, M60s?"

I was amazed that the satellites in these tests were W2s and I attribute my comments to the large amounts of unclipped power (and of course the inherent quality of the W2s).

Alan Lofft,
Axiom Resident Expert (Retired)

#170665 - 06/21/07 02:46 PM Re: Power into M80s from my cheap Denon [Re: Mojo]
jakeman Offline

Registered: 10/03/05
Posts: 853
Loc: Toronto
Thanks for posting the data, though I'm not sure you can conclude much without more testing. For example,though you couldn't measure it, the likelhood is you are clipping that amp and causing compression and unwanted harmonics from the 50hz signal. In other words the SPL from the woofer is not increasing as gain exceeds rated output of the amp. If you were running a mixed frequency signal you would hear the distortion from the HF drivers as the dynamic range compressed.

Clipping and damaged voicecoils go hand in hand so be careful.

#170666 - 06/21/07 03:35 PM Re: Power into M80s from my cheap Denon [Re: alan]
SirQuack Offline
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Registered: 01/29/04
Posts: 13565
Loc: Iowa
Thanks Alan for your comments supporting the use of monoblocks with more power and your results. I know a lot of math and engineer gurus around really push the whole 1 watt mumbo jumbo. However in real situations, as I believe Ian has pointed out, the more power/headroom/etc. the better results.

Yes my Denon does a good job, but it does not compare to my new Odyssey mono's to me in overall sound quality from lower volumes to higher volumes. Now I can easily tell when my Denon is starting to strain, my Odyssey's keep on going. Also, at louder SPL's there is no ear fatique as a result of no clipping, distortion, etc.

I'm a firm believer in seperates now. I wonder if a lot of people who are on the AVR bandwagon have actually experienced a true high-end amplifier.
Anthem AVM60 Outlaw 7700 Emotiva A500 Epson 5040UB

#170667 - 06/21/07 04:38 PM Re: Power into M80s from my cheap Denon [Re: SirQuack]
pmbuko Offline
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Registered: 04/02/03
Posts: 16437
Loc: Ben Lomond, California

I wonder if a lot of people who are on the AVR bandwagon have actually experienced a true high-end amplifier.

Not to beat a long dead horse, but I wonder how many people on the separates bandwagon have actually experienced a true double-blind listening test between separates and AVRs.
I can explain it to you but I can't understand it for you.

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