Is this clipping or just high SPL?

Hey everyone,

A question arose today during a listening session. I have a Yamaha M40 120wpc amp driving GMA C1's with a passive pre-amp. I usually run both my pre-amp and amp at about 12... but on rare occasions I will turn my pre-amp up all the way and boost my amp to about 2 or 3 o'clock. I do this on recordings that seem to be mastered lower than usual...

Anyways, today I was listening at the higher play levels and a particularly abrupt loud passage came... specifically, it was 'Dark Side of the Moon' when the bells come in on the beginning of the third track (that everyone has heard at least 40 times).

I didn't hear any clipping, and never have on this system... but things just sounded more congested with less separation and clarity than I'm used to. Given, it only lasted about 10 seconds during that one sequence... but it sparked the question of whether it was likely that the amp was clipping or that it was just loud beyond my comfortable listening level. I am in a small room about 8 feet from the speakers, btw...

Probably distortion somewhere - most likely clipping with the amp. When it sounds either loud or congested at higher SPL but fine at lower levels then it can be either the power amp or the speakers. (speakers do not clip but they rapidly run out of linear operating range and voice coils can get very hot if driven hard - if you have an SPL meter and if peaks are above 100 db SPL at the listening position then you are in speaker compression territory)
your amp is running out of gas at that volume and starts to clip.
could be you overloaded the room.
Hard to say if it's the amp or the speakers, but next time don't let 10 seconds elapse before turning the volume down.
It is common for many amps to sound "congested" just before reaching the point of clipping. You may find this as an early warning sign that you need to reduce volume.
Another possibility is inter-channel crosstalk through the amp's power supply or internal grounds, which would figure to be worst when the signals are both high amplitude and high frequency.

-- Al
My listening room is also somewhat small. I found that, at anything approaching a realistic(live or monitor) listening level; the room was overloaded. Treating the back wall(behind my listening position, about 2/3: top-down) with 3" Auralex and LENRD bass traps completely cured that issue. There are less expensive alternatives on eBay as well: ( Stand in the middle of your listening room and clap. If you can hear much reverb; that's probably the problem(based on your description).
I would have to agree that the amp is starting to clip as well; however the overloading of the room is also another thought that has merit.
Are you referring to "Time"?

If this is what you are referring to then it is likely you are over-driving the tweeter or midrange or both on your speakers...that track is beautifully clean apart from deliberate distortion on the lead guitar and some heavy compression on the drums.
Hmm... tough to tell. The thing is the amp sounds great at that volume on any other recording I throw at it...

Maybe this is a redundant question, but what exactly is room overload? Is it when the reflected sound is so strong that everything just turns into loud mush?
Yup - "Time"...

But the rated power handling of Green Mountain Audio Continuum 1s is around 200-250 watts I think... so I shouldn't even be close to distorting my tweeter or midrange with a Yamaha M-40 (120wpc) at 3/4 volume.. right? Any distortion would be coming from the amp or the room, wouldn't it?

Would this cause damage to my GMAs?
Do you have an SPL meter? How loud was it? If it was above 100 db SPL then you might be "pushing" your speakers too much.

See this article Unreasonably large distortion in midrange drivers. You can see that it gets bad above 105 db SPL.

The main issue in the midrange and tweeter is excursion outside the non-linear range of the driver rather than amplifier power. This is why many studios use horns and why most speakers for sound reinforcement uses horns. The fact is that most normal speakers (even good ones) compress and distort above 100 db SPL (at the listening position - which can be 110 db SPL for the speaker).
DJ- To answer your question: YES, reflected sound/loud mush at the listening position. As an experiment: find two or three large, thick comforters and drape them on the wall, behind your listening position. That should let you know if slap echo is the problem. Of course- it's also possible that the side walls can contribute as well, but the front and back walls are generally the main offenders.
As Linkwitz states, in the article I referred to,"the large low frequency voice coil displacements can cause large amounts of intermodulation distortion products near the high frequency signal due to the large low frequency variation of Le(x)."

A bell or chime is percussive and contains loads of low AND high frequencies all at once - just like a it is a tough to impossible test for most speakers to generate at high SPL levels without some audible distortion or congestion...
Gotcha - thanks guys.

I just listened again at a slightly lower volume and worked my way back up... because this was driving me nuts.

It sounds fine, actually... I think I'm just not used to playing at higher SPL's than what I'm used to... in fact I'm really impressed with these old Yamaha amps. I think what I was hearing was a combination of room reflection and having sensitive ears... (which seems to vary from day to day for me... some days loud sounds are less tolerable than others... anyone else experience this?).

Incidentally, I would like to measure the DB to get a sense of proportion.

Out of curiosity, if a speaker does have some audible distortion / congestion in a loud passage, but not to the point of obvious clipping... is this going to damage a speaker or just be annoying? Will high end speakers on high end amps all pretty much start to congest at these 100-105 DB ranges?

I doubt I'm up that high in this small room... I hope.
Will high end speakers on high end amps all pretty much start to congest at these 100-105 DB ranges?

At 2 meters from the speaker - yes absolutely. Soundstage will not even test speakers at 100 db SPL as most would get damaged - see quote below from soundstage:

As volume increases, all frequencies should rise at the same rate. However, as a speaker is stressed, compression will occur at certain frequencies. The stress may be mechanical, thermal or otherwise. This test shows those frequencies at which deviation occurs as a result of compression. Many speakers show slight deviations at 90dB. Most speakers start to show serious deviations at 95dB. Very few speakers can be tested at 100dB without damage.

Furthermore remember that soundstage are NOT making IMD tests - so their results look artificially good (when a speaker plays simultaneously high and low frequencies you get MORE distortion).
Thanks for the info Shadorne.

I guess I would need to test my DB to get a sense of where I'm at. There are DB charts with examples scattered about, but I'm not sure how the loudness of these compares to that of a lawnmower from 3 feet away or that of a jet engine at take-off.

The higher levels that I have been referring to are powerful with impact yet still comfortable and clear from only 8 feet away on DSOTM (as long as we are referring to this album I might as well stick with it). I consider myself to have fairly sensitive hearing... sooo chances are I'm not into the 90DB death range... right?
A lot of us like to get the "live" sound in our homes.Might
not be to late to turn it down and save your ears.You don't
want to be walking around in public and saying to your wife,
girlfriend,I can't here you,wait till I turn up my hearing aid!
Perhaps it was a stretch when I assumed most understood; a single classical guitar, a small chamber group, an acoustic jazz or blues set, through Heavy Metal bands or philharmonic orchestras playing fortissimo(ffff) all produce, "live" SPL levels, and those levels vary greatly. So do the levels at which various rooms will overload.
Ya... its all too relative to put definites on.

I do think that I have been listening to my speakers very politely though... the other day I gave them a bit more power than usual and things weren't really loud or harsh, but just had more impact and definition.

I'm not sure if I was at the 'live' level... it certainly is a nice sound as long as I keep it below the room overload level. I hope it's not detrimental to my hearing... I thought that only happened if you listened at painful levels for hours straight.