Axiom Home Page Forums General Discussion Technical Questions Room acoustic question

I think I partly misunderstood what you were saying and thought that you were perceiving the high frequencies as harsh. Getting a “blurry” sound as the volume increases sounds like distortion to me. Though I think it could also be related to the following, which I didn’t explain very well. To much Tequila?



Thanks for explaining what I was actually trying to say.

When I demoed speakers, besides the outstanding bass, the thing that actually struck me the most about the M80s was exactly what Chris describes. The M80s were the only speaker I demoed who’s highs “kept up” with the mids and lows as the loudness increased. With all the other speakers I heard the mids and lows became dominant as the loudness increased.

So there is very little chance that my problem is room related?

Without hearing exactly the same thing you were, it's impossible to say.

No, we're talking about would lead to it being a room problem. We're saying that because the M80s don't roll off the highs, as the room loads up, they become over-bearing. Where as other speakers that don't have highs which can keep up with the level of the rest of the music range won't have the same effect.

The other likely candidate, is the receiver is running out of power. That will cause a sort of dynamic range compression too, and also cause the sound field to shrink. This one is slightly more likely from your description, in that you mentioned a blurriness, that may be the onset of clipping, or a gross amount of harmonic distortion.

I guess you could buy bigger amps, and see what happens, if that doesn't solve the problem, go with more absorptive room treatments (although that may dull lower listening levels). Or just don't play it that loud.

Where were you on the volume knob anyway? -9, 0, +3?

Hi Bruno,

Agreed, extremely unlikely that it's room related. What you might be hearing is "incipient" clipping. That's when the amps in the Denon aren't actually chopping off the tops of the waveform, but getting close, so distortion has risen to audible levels.

Keep in mind that all amplifiers driving 4-ohm loads will have higher measurable (not audible) distortion because of the increased current flow through the output transistors---more heat, more distortion. If you look at the distortion curve on an amplifier as the power output increases, you'll see the distortion figures ramp up just before the amplifier reaches the "knee" of the distortion curve when it actually clips.

I suspect that you were pushing the Denon into this territory that precedes actual clipping, when audio may become somewhat edgy, mushy and unpleasant. I've heard similar qualities from both tube amplifiers (the stereo soundstage collapsed into mono and the sound became mushy) and transistor amps when pushed to levels at almost-clipping.

There is also a psycho-acoustic effect wherein your ears may have reached their limit in terms of loudness tolerance. When that happens (to me and to others I know), the sound subjectively is intolerable and may simply sound "distorted" even when technically it's clean.

Regards,
Alan

Thanks Alan and Chris.

The power might very well be the reason I experiencing this blurriness. Just for reference, my knob on the AVR was around -8dB and is was driving 2xM80s and the VP180, the Denon was pretty hot. I usually don't have it at this level unless in another room. I wasn't aware of this "incipient clipping", I just knew of the chopping clipping that I experienced once when I had the knob at +5dB and since then I set the receiver to the max on the knob being 0 in case the teenage daughter decides to crank it up as I never heard chopping at this level. I understand that the chopping can damage the tweeters but can this incipient clipping damage them too? Should I lower even more the max level on the receiver?

Bruno,

No, not usually, but remember that the "0 dB" point on a given receiver's volume setting is only approximate. I'd view anything close to 0 dB as dangerous territory in terms of rising distortion levels that may become audible prior to actual clipping. If certain levels sound mushy, edgy, harsh to your ears, I'd lower the level.

To determine a particular receiver/amplifier's point of actual clipping, you'd have to measure it on the test bench driving a fixed 4-ohm load with a distortion analyzer and follow that up with actual listening tests with a music program signal and a panel of listeners, noting the level at which everyone agreed that the playback signal seemed harsh. It's a very complex process, complicated by the fact that there is individual variation from one person to the next as to what is subjectively perceived as "too loud."

There are cultural factors as well. Have years of listening to over-amplified rock concerts conditioned or prepared some of my friend's and colleague's ears to tolerate much louder playback levels than I can tolerate? (I grew up with largely unamplified music, both in the instruments I play and the concerts I've attended). There are cetain kinds of highly amplified and distorted "grunge" guitar/heavy metal that I can't stand (TomTuttle likes it, because I presume his ears are "used to" or conditioned to like it, as are some of my Axiom colleagues.)

It's really interesting territory.

Cheers,
Alan

One thing I don't understand though, Many times I've read on this forum that the M80s actually will play very loud using not too much power (from my understanding, 60W will get them to play very loud) and the the extra power is overhead. I don't think that I had them to extreme levels, so shouldn't my 105W/ch have enough overhead for me to play them loud without distortion?

Keep this in perspective what Alan wrote and that you are driving 3, 4 ohm speakers.

Keep in mind that all amplifiers driving 4-ohm loads will have higher measurable (not audible) distortion because of the increased current flow through the output transistors---more heat, more distortion. If you look at the distortion curve on an amplifier as the power output increases, you'll see the distortion figures ramp up just before the amplifier reaches the "knee" of the distortion curve when it actually clips.

Do you have pre-outs on the 890? You might want to look into a separate amp stable down to 4 ohms for the front 3.

Since you said it is running pretty hot, you should take a temperature reading on the Denon during normal use and see what it is running at.

Correct, Bruno; unless the level was extreme, say above about 105dB, distortion in your 890 wouldn't have been an audible factor.

Dr, on the 890 I don't have pre-outs, but even if I did, I am not sure I would go with a separate amp in my current sized room. As I said, I rarely have them play at these levels. I'll try to get a temp measurement though.

John, I don't have a SPL meter but I don't think the volume was extreme, loud yes but not extreme. Extreme levels were once when I turned the knob to to +5 and started to experience clipping.

I still think it might be room related, the highs seem to have an accurate sound but both channels seem to get mixed together rather than well defined as at lower levels. Tomorrow I'll try to cover the rest of the hardwood floor with bed sheets and pillows and see if it helps.