Pop Sound in my speakers when driven loud from studio recorded CD sources.

Al, Thanks for reviewing your original response. Most here seem to think that the amp is clipping. Is that what you are describing by saying....

No. What I was referring to in the post I deleted was clipping of the "small signal" circuitry in the receiver that precedes the volume control in the signal path, that is in the receiver’s preamp section. The others are referring to clipping of the power amp section of the receiver, that would result if the amp is asked to provide more power to the speakers than it is capable of providing. As I indicated in my previous post I deleted my earlier post when I noticed your statements that the problem only occurs at high volumes. If my hypothesis had been applicable the problem would manifest itself at any perceivable volume.

In any event, after looking further at the specs on the 2275 and doing some calculations, it’s hard for me to say whether the problem is inadequate amplifier power, resulting in clipping, or a defect of some sort in the receiver or the speakers.

On the one hand my understanding is that as a rough approximation rotary volume controls tend to provide attenuation at the 12 o’clock position (which is where you stated the problem tends to begin to appear, for those recordings which cause it to appear) that is roughly in the area of 20 db or so. 20 db of attenuation would reduce the 2.1 volt maximum output of the DAC to slightly more than the 180 mv that would cause the amp to reach its maximum power capability. Which in turn points in the direction of not having enough amplifier power.

On the other hand, according to the specs I’ve looked at the amp is rated to provide 75 watts into the speaker’s 8 ohm nominal impedance, and you indicated it was recently bench tested as providing 85 watts. In a medium sized room at typical listening distances (say 10 or 12 feet) 75 or 85 watts into two 86 db 8 ohm speakers should be able to produce sound pressure levels of around 100 db or so at the listening position, assuming the speaker specs are accurate (although that is certainly not always a good assumption, particularly when it comes to speaker specs). SPLs of 100 db or so are more than most listeners would require on most or all of their recordings, the most likely exceptions being recordings having exceptionally wide dynamic range (i.e., very large differences in volume between the loudest notes and the softest notes, such as some well engineered minimally compressed classical symphonic recordings). But in most cases the ability to produce that much volume at the listening position would suggest that amplifier power is adequate.

So I’m not sure what to point to as the likely cause of the issue, aside from the probability that it is being introduced downstream of ("after") the volume control in the signal path.

Regards,
-- Al

Al, Thank you! This is an education for me. I think I understand your detailed explanation. In summary, you are saying if I were to rule out some electronic or mechanical failure in either the Marantz or the Hales, it is most likely inadequate amplifier power based on your calculations of the published specs... or in your words, "...clipping of the power amp section of the receiver." Only solution to that, is a more powerful amplifier I presume.

If it is volume dependent clipping, the other simplest solution would be to live within my equipment’s boundaries and not play the CD’s too loud to the clipping point... and potential destruction of my gear! The problem with that, is that the effect is more pronounced with recordings on CD that are more compressed, which generally you want to listen to louder to give the sound more ’presence’ in the room. As you also pointed out, the more ’spacious’ recordings, within my system can definitely be played louder without the clipping effect emerging... no question about that.

Any other observations would be welcome from all... thanks again!

... the effect is more pronounced with recordings on CD that are more compressed, which generally you want to listen to louder to give the sound more ’presence’ in the room. As you also pointed out, the more ’spacious’ recordings, within my system can definitely be played louder without the clipping effect emerging... no question about that.

I’m not sure that we’re using the term "compressed" in the same way. I use the term to refer to a recording that has been engineered such that there is a relatively small difference in volume between the loudest notes and the softest notes. The opposite of that would be a recording having wide "dynamic range," meaning a large difference in volume between the loudest notes and the softest notes.

The majority of pop and rock recordings are dynamically compressed to a considerable degree, and consequently have a relatively small difference in volume between the various notes. Less than 10 db in many cases, which corresponds to the loudest note requiring less than 10 times as much power to be reproduced as the softest note.

**Some** well engineered classical symphonic recordings, on the other hand, can have dynamic ranges of 30, 40, or even 50 db. Those numbers correspond respectively to requiring 1000 times, 10000 times and 100000 times as much power to reproduce the loudest notes as the softest notes, the loudest notes usually being very brief, and the softest notes usually being far softer than on most pop and rock recordings.

Therefore it is the latter recordings, having wide dynamic range, that will usually result in the user turning up the volume control higher than for the highly compressed recordings. And consequently much more power will usually be required to reproduce the (usually brief) high volume dynamic peaks on recordings having wide dynamic range than on recordings on which the volume of the notes doesn’t vary a great deal.

But if in fact you are finding that recordings having wide dynamic range do not cause the problem, while some recordings having narrow dynamic range do, it would lead me to suspect that the problem is not inadequate amplifier power. Rather it would suggest the possibility that either the amplifier section of the receiver is not able to handle the thermal (heating) effects of having to supply high power levels fairly constantly, or the speakers are not able to handle the thermal (heating) effects of receiving high power levels fairly constantly. And perhaps the recordings with the strong drum beats that you referred to are putting that over the edge.


But the situation I described in the previous paragraph would be unusual, compared to problems involving clipping of an underpowered amplifier on brief high volume dynamic peaks, or problems involving defective equipment. Which leads me to suspect, as I said at the beginning of this post, that we may be using the term "compressed" to mean different things.


Regards,
-- Al

Can you see the cone popping out when it happens? 

blocking the ports prevents excessive cone excursion below the tuning frequency. You'll loose a little bass, but this is a temporary, reversible experiment.