Axiom Home Page Forums General Discussion Stereo Power into M80s from my cheap Denon

Dead horse, nothing. That thing's a zombie.

Hi Randy... a few weeks ago you said:

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Good point Rick, and one I've been wanting to ask as well. Seems many like to reference articles and base everything on math, etc., but have they actually been involved in real world test themselves.

I'm looking at a Russound AB-2 switcher so I can jump back/forth between my Denon and Amps. I plan to invite some friends over for some tests. I'm not even going to tell them what they are testing.

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How bout putting those Odyssey's to the test?

Peter and Ken,

Just curious, I believe both of you had heard Dennis's Halo system in his large room and high spl volumes. Do you actually think a cheap Denon could provide the same performance?

I plan to figure out a blind test scenario at some point, but to my ears I can easily hear a difference on most songs when using my Denon by itself versus throwing the Odyssey's into the equation.

No, I don't. Where I have my doubts is at low(er) volumes, say up to around 80dB. Shutdowns are patently, provably the case with higher volumes, as both you and he showed. Presumably distortion occurs before those shutdowns.

What I also know (from my own experience) is that audio memory is remarkably short--on the order of seconds. Instant switching is the only way that one can trust one's ears--and brain.

When deciding to buy my RV-8, I auditioned one driving speakers with it's internal amplifier, and then through an LX-7 amplifier with the RV-8 feeding it as a preamp. Although there was some time for "switching" involved (it wasn't an easy A/B switch), I couldn't hear any difference, so I figured this AVR was good enough to my ears.

My AVR is rated at 140W per channel into 8 Ohms fully driven, and the LX-7 was 200W per channel I think. So I'm sure I would have heard a difference once the RV-8 was pushed current-wise past what it could deliver, where the more powerful separate amp would give a little more. I guess we didn't get it that loud in our testing, but it was plenty loud enough.

I've found its difficult to tell the difference at low volumes where there is no clipping or compression. At moderate volumes with music containing a mix of quiet and loud passages you can hear the onset of compression and distortion. It manifests itself as loose one note bass, smeared drums and shrill, unclear music. Switching to a better amp, usually a more powerful amp, means you can play the speakers much more loudly without the nasty artifacts you get from a clipping amp trying to reproduce quick musical transients.

There is a great jazz cover of "Walking on the Moon" by The Yuri Honing Trio that has excellent drum and sax attack and quiet plucking that make it ideal for testing your system. Bass, drums and sax go from barely audible to not hearing yourself speak and back again several times. You'll know if your amp clips or how well your speakers perform with this one.

When my brother visits he brings his favourite CDs and DVDs and keeps raising the volume to much higher levels than I am used to and complains my system doesn't sound loud enough. He is used to hearing much more distortion from clipping on his system at lower volumes.

I agree with Alan's and Jakeman's posts on distortion. As I mentioned, I didn't have the necessary equipment to conduct distortion measurements. This was a "poor engineer's" characterization . One day, I'll borrow a scope to satisfy my curiousity.

It's worth noting, again , that I keep my Denon at -25 for music and around -20 to -15 for movies. This translates to about a half watt to 2 watts (measured under a different experiment). So when listening to movies, this gives me about 22dB of headroom and music 16dB of headroom (referenced to 90W). This is more than enough headroom. Now admittedly I don't know for sure if my receiver is clipping at 90W but I certainly don't hear any clipping. BTW, these power levels translate to 80 to 90dB SPL in my room.

Another item worth noting is the effects that high power have on your listening experience. Higher power to your speakers translates to more heat that must be dissipated. Speakers are not heatsinks and they are not terribly efficient at cooling themselves. The sinister aspect to this is that as the voicecoil temperature rises, its resistance increases. As its resistance increases, the power to the speaker goes down. As power to the speaker goes down, SPL decreases. So now a "portion" of your high powered amplifier is acting as a heater . The question of course is to what degree? If you are putting 300W into a speaker, is 150W going into heating? I'd need to work the math out on this one.

And now something even more sinister. Ever wonder what happens to the speaker's passive cross-over design with these heating effects? Very simply, the cross-over frequencies will shift with volume.

And there are also deleterious effects on the magnetic circuit...I won't go there .

Most of us need not concern ourselves with these worries. But there's a few out there that may want to take note. Those that want more power may not only need a larger amp. They may also need larger speakers. And perhaps even active cross-overs. And ear plugs .

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Another item worth noting is the effects that high power have on your listening experience. Higher power to your speakers translates to more heat that must be dissipated. Speakers are not heatsinks and they are not terribly efficient at cooling themselves. The sinister aspect to this is that as the voicecoil temperature rises, its resistance increases. As its resistance increases, the power to the speaker goes down. As power to the speaker goes down, SPL decreases. So now a "portion" of your high powered amplifier is acting as a heater . The question of course is to what degree? If you are putting 300W into a speaker, is 150W going into heating? I'd need to work the math out on this one.

And now something even more sinister. Ever wonder what happens to the speaker's passive cross-over design with these heating effects? Very simply, the cross-over frequencies will shift with volume.

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I wonder if Ian knew this when he designed the M80s

Well, I wasn't specifically referring to the M80s but speakers in general. The M80s are rated to 400W. So I am sure they don't experience any of these issues until above that level. 400W is an amazing figure for a speaker, period! Especially a pair that sounds so darned good!