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

I would listen to the offending CD on another player (car?) to hear if the pop is on the CD.  The second thing is to determine if the amp is clipping....listen with a lower volume.  Next determine if the "pop" is coming from any of the drivers themselves.  This is a bass reflex design and therefore has a port.  You said it was an older speaker.   I'd pick it up and shake it to determine if there is anything in there that souldn't be there.  Let us know.

Stringreen... thanks.  It's not a particular CD.  The 'pop' correlates to certain sounds on any number of CD recordings.  For instance, a hard slap of the snare drum or tom tom drum by a drummer.  So the pop coordinates with certain sharp staccato sounds like that.  That's why I thought it had something to do with possible errant mechanical movement of a driver.  Perhaps, for all those years of being stored and not used, the actual membrane materials are not as supple as they were.

But I will definitely do the shake test and get back to you.

I’m afraid there is no rattle or anything loose when I shake the speakers. I would revise my description of the sound though, from a "pop" to something more like a "fart" or "burp"... sorry folks, that's what it sounds like ;-).

As far as amplifier clipping is concerned. A recently completely restored Marantz 2275, which was bench tested at about 85 wpc is what the Hales speakers are working with. I don’t know enough about clipping to know if it possible that my amplifier is producing this effect. Playing the same CD passages at lower volume does not produce any of the "pop" "fart" sounds.  It only happens at higher volumes.

Doing some research on clipping. My issue does seem to be (and sound like) amplifier clipping.  Only specific 'sharp' sounds seem to cause the speaker drivers to shutter.

Anyone want to confirm this? The amplifier in the Marantz receiver does not have a gain control. Is my only option playing at lower volume? A more efficient, powerful amp.  I really thought 85 wpc would drive these speakers properly.  Thanks.

Sure sounds like amp clipping, which can fry tweeters. It happened to me one time.

The Hales are 86db at 8ohms - that might be a pretty difficult load to drive at high volume for most amplifiers less than 100 watts. The review of them (1998) on Soundstage! had them powered by 200w Pass Labs. he did use a 40w Clayton S-40 tube amp, but I'm not sure how much that was also helped out by the Threshold FET pre-amp.

Your Marantz also has an input sensitivity of 180mv. WHat's your CD player's output?

Thanks all!  

Simao: Cambridge Audio CXC Dedicated Transport.  It says "Output Impedance" <75 ohms.

Hmmm. Then that shouldn't be the problem.
Your drivers are clipping because they're getting too powerful a signal from the DAC in your cd player when they play certain frequencies or ranges.

Do you have any other amplification sources you can try for a test?

The Cambridge CXC CD Transport does not have the DAC in it... it's just a transport.  I'm running all digital signals through the Cambridge DAC Magic Plus.  It's a digital converter and preamplifier (I'm not using the preamplifier part). Output impedance of the DAC component is <50 Ohms

I have another Marantz... the 2245. Also fully restored and putting out about 58 wpc. Probably not a good for testing with the 8 ohm Hales.

My bad for not reading your earlier post more clearly re: the Cambridge transport.

This is all helpful... So, the output of the DAC is <50 ohms.  Is that relevant?

You might be hearing the woofer voicecoils, bottoming out, or- when woofers exceed their max excursion, things can sound really nasty. Another possibility, that I’ve experienced: a bad filter capacitor in your amp’s power supply. I thought one woofer, in my TL, actively bi-amped, bass system was cracking, on big bass transients. Couldn’t find any issue with the driver, but replaced both anyway, as they were purchased in 1981. Same noise(crack/pop), after spending about $500(better woofers, so- no regrets). Took the cover off the amp and found a leaky electrolytic. Replaced/upgraded all four.

Filter capacitor: Not likely. They were all replaced & upgraded (along with a lot of other internal components) in the Marantz’s restoration process, only a couple of months ago. The unit was also extensively bench tested before it was returned to me. But, you never know...

Hey... I got an email that member "almarg" posted to this thread, but I don't see the full post here.  The partial post I got in the email is below.  Almarg, if you are out there I would like to know your full response.  Not sure why it didn't get posted here.
"Given the 180 mv sensitivity of the Marantz receiver and the 2.1 volt maximum output level of the DacMagic+ unbalanced outputs, it seems very conceivable to me that the problem may be due to overdr....."

If they are ported, seal the port with a rag. Repeat.

Yes, they're ported.  What will blocking the ports do??

Almarg, if you are out there I would like to know your full response. Not sure why it didn’t get posted here.

I deleted my post a couple of minutes after I submitted it, because when I composed it I hadn’t noticed your statements to the effect that the problem only occurs when the volume is turned up to loud levels. That fact makes what I had said in my post inapplicable, since it indicates that the cause of the problem is "downstream" of the volume control. FWIW, though, what I had said is as follows:

Given the 180 mv sensitivity of the Marantz receiver and the 2.1 volt maximum output level of the DacMagic+ unbalanced outputs, it seems very conceivable to me that the problem may be due to overdriving whatever circuitry in the Marantz precedes (i.e., is "upstream" of) its volume control.

As an experiment, and conceivably as a permanent solution, try enabling the DacMagic’s digital preamp function, reduce its volume control setting significantly, and increase the volume control setting of the Marantz to provide preferred volume levels. See if the problem still occurs.

Alternatively, you could try enabling the DacMagic’s digital preamp function and connecting it to the input jacks of the power amp section of the Marantz (initially with the DacMagic’s volume control set low!), while disconnecting the Marantz’ pre-outs from those jacks.

If one or both of those experiments confirms this diagnosis, an alternative solution would be to insert a pair of Rothwell attenuators between the DacMagic and the Marantz.

Again, none of this appears to be applicable, given the sensitivity of the problem to the setting of the volume control. Not sure what to suggest at this point, beyond what the others have said.

Good luck. Regards,
-- Al

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: 

"...Given the 180 mv sensitivity of the Marantz receiver and the 2.1 volt maximum output level of the DacMagic+ unbalanced outputs, it seems very conceivable to me that the problem may be due to overdriving whatever circuitry in the Marantz precedes (i.e., is "upstream" of) its volume control."

On the other hand, Rodman thinks:

"...You might be hearing the woofer voicecoils, bottoming out, or- when woofers exceed their max excursion, things can sound really nasty...."

If the woofers were really bottoming out, wouldn't that mean the speakers were being seriously overdriven (too much power)?  Simao, disagrees with that and says this:

"...The Hales are 86db at 8ohms - that might be a pretty difficult load to drive at high volume for most amplifiers less than 100 watts..."

The Marantz was bench tested recently at about 85 wpc.  Therefore it may not be driving the speakers efficiently enough.

Am I understanding all of these comments correctly?  Thanks!

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.

Kanjit, The covers on the Hales are nearly impossible to remove.

Erik, I did try blocking the ports, but no change.  In fact it may have made the phenomena worse... hard to tell.

Al... thank you again. I think that we are understanding the terms "compressed" and "spacious" in the same way in terms of dynamic range. It’s just that I handle the volume issue with each, differently than most, I guess. The truth is, I enjoy the wide dynamic range sound much more so than the narrow range employed in many of today’s recordings. Wide feels more live and ’in the room’ where as narrow sounds canned or unrealistic to my ears... hence my impulse to crank it up and make it feel more real. Perhaps a fool's errand ;-)

You’ve also added thermal overload, either in the amp or the speakers as a possibility. Is it possible that my Hales speakers, which I purchased new nearly 20 years ago and have spent the overwhelming majority of that time in storage and unused until very recently, may have some material degradation of say the membrane materials?

Change your electronics.

Hi All... I’m dredging up this 1+ year old thread because I think I discovered the solution to the problem I brought up here (I’m the orginal poster).

I had complained of a pop or burp sound when I was playing CD’s and there was a brief spike in sound, like when the drummer slaps the snare drum. This would happen at fairly loud volume. So, it was preventing me from turning the volume up on my amp to a nice loud concert level. If you want to know more, see the original post at the top.
All of my digital sources are routed through a Cambridge Audio DAC Magic Plus. This DAC has a "pre amp mode" with a volume control knob that is activated when headphones are plugged into the DAC... or when it is purposely selected by the user for speaker listening. Until now, I have been using the DAC without that pre amp mode selected... and THAT is when I find that the amp’s volume knob tops out early and the popping/burping sound starts happening coincident with the brief spikes in sound.
Now, I am using the DAC in pre amp mode and putting the amp’s volume knob much higher and then adjusting the DAC volume knob to get the music to a good listenable loud concert level... and to my surprise, I no longer get those pops/burps in the same instances that I was before. I believe that one of the posts earlier in this thread hints at trying that very thing out. But it was not until now that I tried it.  I'm still working on the optimal ratio between the two volume knobs.

Of course, I’m happy about this, but what I would like to know from you all, is what might be happening within my system between the receiver (pre amp/amp) and DAC (with pre amp volume control activated). Now there’s actually 2 pre amps working simultaneously. I don’t really have the technical knowledge to know why it’s working better, but I’m sure curious. Thanks!

Glad that the problem is finally solved.

It seems that what I had said in a post which I subsequently deleted (because it seemed inconsistent with the sensitivity of the problem to the setting of the volume control), but which I quoted in a subsequent post after you asked what I had said, was in fact applicable:

Given the 180 mv sensitivity of the Marantz receiver and the 2.1 volt maximum output level of the DacMagic+ unbalanced outputs, it seems very conceivable to me that the problem may be due to overdriving whatever circuitry in the Marantz precedes (i.e., is "upstream" of) its volume control.

As an experiment, and conceivably as a permanent solution, try enabling the DacMagic’s digital preamp function, reduce its volume control setting significantly, and increase the volume control setting of the Marantz to provide preferred volume levels. See if the problem still occurs.

I can’t explain, though, why putting a smaller signal level into the Marantz has helped, given that the problem had only occurred at higher settings of the volume control. Detailed knowledge of the Marantz' circuit design might be required to explain that.  As I indicated earlier sensitivity of the problem to volume control settings would seem to signify that the "pop" is being introduced "after" the volume control in the Marantz’ internal signal path, where signal levels are presumably about the same for a given perceived volume regardless of whether you are using the DAC’s preamp function or not.

Regards,
-- Al

Wow... Thank you again Al.  I'll continue to monitor the situation and try various other CD's where I know the "pop" was happening before.
As you point out, the mystery may be within the Marantz's circuit design:

Detailed knowledge of the Marantz' circuit design might be required to explain that

At this URL, scroll down to the bottom, and there are links to PDF's for "schematic" and "diagram" for the Marantz 2270 I'm using:http://spacebullet.net/marantz-2270.html.  If you feel like it, take a look; my curiosity continues!  Best, Mike

Hi Mike,

Thanks for providing the link. I had previously found the service manual, including the schematic, at hifiengine.com, but the block diagram provided at your link is also helpful.

But after looking at these documents I’m still at a loss to explain the mystery. The circuitry between the line-level inputs (Aux, Tape In 1, Tape In 2) and the volume control looks pretty straightforward and conventional. With nothing I can see that would explain why the problem is apparently introduced in circuitry that is "ahead" of the volume control while also manifesting itself or not depending on the setting of the volume control, when the DAC’s preamp function is not used. As you said in one of your earlier posts:

Playing the same CD passages at lower volume does not produce any of the "pop" "fart" sounds. It only happens at higher volumes.

And as I indicated previously, signal levels in the circuitry that is "after" the volume control are presumably about the same for a given perceived volume regardless of whether you are using the DAC’s preamp function or not.

Best regards,
-- Al

Hi Al... further experimentation with using the DAC in pre amp mode is proving that I can play at higher volume now, without inducing the "pops".  Thanks for your help!  I'll make any updates here.  If you have any further thoughts, post here.