When an amp clips, the waveform(simplified) looks like a sine wave with the peaks cut off flat.All of the energy above that cut off peak has gone straight to your tweeter in the form of distortion and distortion harmonics. Due to its nature, it is not filtered out by the crossover network, but slams right into your very fragile, low power handling tweeter. Avoid this practice. Yes, your amp is clipping, but don't be alarmed, all amps will clip when driven hard enough, especially on transients like the one you mentioned. Your very fine amp is simply running out of gas trying to reach the volume you are pushing it to. If you can't get the volume that you want with that speaker/amp combo, then you need to change something or lower the volume. The reason that CD(?) is the culprit is that the dynamic range difference from the normal passages to the drum hit is greater than your amp can bear, at the volume you are using. Many of us here have experienced similar circumstances, which is why there are so many amps for sale in the classifieds. You also could change your speakers to more efficient types instead of changing the amp, if you would rather keep the amp than the speakers. Or you could just turn it down a bit which is MUCH cheaper.
the speakers cones are bottoming out
Jimmy, I just checked the specs on Aeriel 6's and they are only 85db efficient. This low efficiencly will send a lot of amps into clipping trying to achieve high volume peaks. Briefly, you have to double the power for every 3db volume increase you want, so you'll roughly need 128 watts for 106db peaks. Your amp would probably do this, but the speaker also has a 4ohm impedance dip that may limit the amp's headroom. If you are trying to reproduce a peak louder than that, you are into at least 256watts. And that's at 3ft from the speaker. Significantly less loud at the listening chair. So, if you're cruising along at 100db and along comes the bass drum with a dynamic peak that's more than 6db higher than average - you're toast(clipping).
Could be a manufacturing defect of some kind. An Ace-of-Base CD I owned made a sound like a sliding patio door slamming shut (on the "all that she wants" cut...). The Best Buy agent couldn't hear it on the boom box he tried (can't imagine why) but took my word and let me return it.
This happen to anyone else?
Thanks TWL for the informative response - it puts it into perpective for me. But note though that even when connected to my MC300 (300 w/ch) at the 4 ohm tap I still got the same sound (I presume these would clip well beyond where the Rowland woud clip). But I realize you were just pointing out a reference point with the numbers, not knowing how loud it actually was registering. I will have to put the disk back in and see at what decibel level it starts to clip.
Jimmy, I am not familiar with that CD. Maybe it is an unusually large quick dynamic peak of maybe 10db or more. A 10db peak is twice as loud as the average sound level.If you're playing at 100db avg. and you get a peak like that with your particular system, you're gonna need over 300 watts to do it. That would account for the same behavior with the MAC 300 as they have very little headroom. This sounds like a very tough CD to me and it's likely that a lot of systems would have trouble with it, when played loud. If your speakers were just 3db more efficient(88db), then you would only need half the power(150w) to cover the peak without clipping. With a speaker efficiency of 91db, you could do it with 75 watts. Do you see how a little more efficency in speakers can go a long way in reducing power requirements?
Definitely the speaker. I've listened to the Aerial 6's and played a classical piece that had a gunshot type sound at the beginning. At about 1/3 volume it, the woofers quickly overextended themselves. There is no bottom end whatsoever in the 6's.
I really enjoy Aerial's as I own the 10T's. I also own the Copland "Fanfare for the Common Man". You are probably talking about track 2. There is no way the aerial 6's could handle that. IMO.
Interestingly enough, the speakers started making the sound at about 80-85 Dbls - which was the level recorded at the peak of the drum "thwack", 3 ft. away from the left speaker. Any more than that and it got worse quickly...
Twl has done a VERY nice job on this one. Kudos to him for putting in the effort and presenting all of the figures and effort that he has. As such, i tend to agree with him. SOMETHING ( speakers or amp ) is making VERY audible signs of distress. If you continue to do this, you can expect BAD results in a short period of time.
Not being familiar with the speakers, i assume that they are vented. Playing high energy notes that are centered below the tuning of the cabinet will produce the potential for massive over-excursion. This can manifest itself as the woofer severely bottoming out which sometimes sounds like "clicking". Since many voice coil formers are aluminum and they are bumping the back plate, which is also metal, it could be conceived as a high frequency note due to it's more "metalic" or "grating" tonal character.
On the other hand, your speakers are so in-efficient that i can imagine that you could drive an amp into clipping relatively easily. The only problem with this theory is that you state that the SPL when these conditions manifest themselves is quite low, pretty much ruling out amplifier overdrive. The fact that it does not occur at slightly lower SPL's points points towards the first scenario i.e. the woofer bottoming out.
Have you ever watched the woofer as this phenomena occurs ? Is it throwing like mad ( or at least MUCH more than normal ) when you hear this noise ? While i'm not encouraging you to keep repeating this situation, you do need to find out what is going on. The only way to do that is to repeat the situation and study it step by step. If you are going to repeat this a few times, i would highly recommend letting the system / speaker cool down in-between attempts. Clipping and / or over-excursion are bad enough, let alone adding heat build-up to the situation. Sean
Sean, thanx for your kudos. The reason I went in the direction that I did was because he stated that the noise was coming from his tweeters. Of course, you know how hard it is to diagnose something that you can't hear, so we're kind of running in the dark. Stehno says that he has heard the 6's break up pretty early on the bass, too. Could be that. But, if the noise really is coming from his tweeters, then he's clipping, no matter what the db level is. Whatever, the siuation might be, I'd say it's a bad combination of amp/speaker at best.
Another possibility of why this could happen is a low preamp/source level. This would account for the amp having to drive alot of power trying to hit normal listening levels. You could tell this right away if you have to turn up the volume knob quite high to get normal volume. The opposite could also be possible. If the source level is too high for the preamp input section, it might overload the preamp input on a high peak, thereby causing a distortion in the preamp that is passed on the the amp and then the speaker. You could tell this right away by not having to turn the volume knob up very much at all to get normal listening levels. Give us some more info, Jimmy.
Twl, i doubt that it is the source overloading the preamp, as this would evidence itself at any volume setting. It would be passed down the line as lack of detail and separation of notes with everything sounding smeared.
The part about non-linear gain could hold water though and come into play with the gain curve of the preamp or power amp. Hopefully, both of those devices are linear enough that this is not a major factor. Otherwise, one would have a heightened sense of the system sounding OVERTLY dynamic on any music that varied intensity levels to a noticeable degree. Some people might think that this was initially great as you would experience a heightened sense of impact and slam upon dynamic transients, but i think that it would come across as being un-natural in the long run.
If Jimmy is up to it, he can simply unscrew the tweeter and disconnect one of the wires going to it. If the noise continues, he's obviously expecting too much from the woofer. If the noise disappears, that would mean that the tweeter is the source. As such, he'd probably be clipping the amp pretty hard or something in the high frequency circuitry is defective and crying out for help. Sean
I have this cd as well, and auditioned it on 10 different systems, full-range Watt/Pupps etc. It is in the cd...it bothered me for awhile as I thought a tube was to fault in my preamp...not so.
Sean, the source input could be within acceptable limits, except for real strong peaks like this one, and still sound fine normally. Overload only on strong peaks can happen. It may or may not be the case here though. In fact, since we don't know any more than what we've been told, we really aren't sure what it is, yet. Also, if it is in the CD like Keithr says, then we're all barking up the wrong tree anyway. But, I enjoy trying to figure problems out like this, it's fun. And if there really is no problem and it's on the CD, it's a lot better for Jimmy than to have something wrong with his system.
Thanks again for your informative responses - I am impressed here with your level of interest/help. That been said, I won't dispute Keith's post, but I will repeat (see earlier) that when I plugged in headphones to this recording (back when I had the McIntosh C-15/MC-300 combination) the recording was clear (no sonic imperfections). For what it's worth, also, this CD has been named in some magazines as a great recording - even for the RR label (having read those reviews, and hearing nothing about an imperfection, I assumed it was my system). Anyway, as for the theory of the woofer overextending, I suppose that is very possible. And I have watched them during this passage. But it is too fast to see, presumably. Unlike other recordings I have (organ of Holst's "The Planets", Raven Records (astonishing BTW), wherein the woofers are "bellowing" in and out very quickly (I would think around 30 Hz) for some low notes and producing absolutely no sound whatsoever (I can tell something LOW is present from my Strom III), the Copland CD does not show me any visual signs of the woofers moving extensively. Incidentally, when I play the aforementioned organ CD at HIGH volumes, those woofers look like they're about to explode, yet nothing happens. So (at length...) I wonder about the overextension theory, as I have seen these things move at about 1" limits but with no similar sound. But that does not rule it out of course.
As for dismantling my tweeters, I am not sure I have the stomach for that. Is it no big deal?
I guess what I was hoping to hear was that other people had the same experience with this CD - that it was a "speaker killer," as Keith suggests...
My apologies. My Copland cd is Telarc not Reference Recording. But there are some serious kettle drum or some kind of drum episodes that I've cranked quite loudly and thoroughly enjoy it.