What causes clipping?

I am trying to understand why my Kinergetics SW-200 subs are clipping so easily. I had a thread in "speakers", but realized this "tech talk" forum might be a more appropriate forum to help me understand what actually causes clipping.

I am mostly using my system for home theatre with a HK AVR300 receiver and pairing the subs with Spica TC-50's. The Kinergetics seem to be easily overwhelmed when "bassy" scenes come up in movies. But, other than when aliens are landing, they don't seem very loud.

The Kinergetics have their own 150W x 2 amp which is fed from the pre-amp out on my HK receiver. The receiver only has a mono pre-amp out, so I am splitting that to the L/R Kinergetic amp inputs.

What I am calling "clipping" is when the subs make a fast, loud, popping noise. A fuse in the Kinergetics sub may also burn out if this goes on for a long time.

1. What causes the clipping? Is it the sub amp being overloaded or is the speaker itself in the sub being overloaded?

2. Would a bigger sub amp solve the problem? If so, any recommendations?

3. Can clipping be caused when the amp can't get enough current to power the speakers? For example, I have the Kinergetics amp plugged into the switched AC outlet on my HK receiver. Can the amp be overloaded as it tries to suck the power it needs through the AC cable maybe causing a dip / spike pulse to the speakers?

4. Does room size or speaker placement have any affect on clipping?

Thanks for the help.
What you describe sounds like a mechanical noise made by the woofer cone exceeding it's excursion limits (although I'm just guessing.)

"Clipping" in the normal sense of the word is the flattening of the sine wave in a signal when an amplifier "runs out of steam", ie, it can't produce the required voltage. The power of the amp, the efficiency of the speaker, room size and placement, and of course listening level are all factors.

Hard to say what the exact cause is in your case. A bigger amp might help, but before you invest, I'd begin by 1) making sure your listening position isn't in an acoustic null (this would require you to really crank up the level in an effort to overcome room acoustics....a losing battle), then 2) moving the sub closer to a corner to try and take advantage of room loading to increase the acoustic output.

If you haven't done some research here on the 'gon or elsewhere on the net for some information on room acoustics and subwoofer placement, it's a good place to start. Proper positioning of the sub and the listening chair can make a huge difference in getting fast, tight. tuneful bass.
Thanks for the info.

Hmmm... if you're correct (which I assume you are), then my amp is actually overloading the speakers themselves. I usually only have the amp at half power or so and can have this problem. Interesting.

Does "clipping" ever have a load crackling, popping noise associated with it? The sound it is making just doesn't sound good for the speakers! ... so it would make sense they are being overpowered and pushed beyond their excursion ranges.

Is there a quick way to test if it is the speakers or the amp that is the problem?
You might have blown the drivers.
150W to a subwoofer should not overload it. Maybe your sub drivers are actually 2-4 ohm loads, and it is affecting the amp.

Do the amplifiers get real hot?

If it doesent seem loud, and the amplifier is not cooking, and you still get that cracking my bet is the drivers are toast.
I concur with Robotman it doen's sound like clipping. Most powered subs will have a matched amp to the requirements of the driver. I would try an ac outlet direct. The HK may be limiting it some. It really does sound as if the voice coil is reaching it's excursion limits, whish is most likely a result of overdriving it. Try reducing the crossover setting.
My guess is the speakers have been fried.It doesn't take much 'crackling' to fry a driver,now the original reason as to why can sometimes be from a momentary short. (In addition to what others have posted)
I don't think the driver is blown. It still seems to work fine at moderate volume levels. Just at loud, bassy times (i.e. organ in phantom of the opera or a big movie scene), they start having problems.

The fuses that sometimes blow are the ones inline to the speakers. Therefore, it seems like the amp itself is sending too much power to the speakers (causing them to exceed their excursion limit).

I was just wondering if there is some "power surge" effect caused when the amp can't get enough power and then tries to compensate but ends up overcompensating and thus overloading the speakers. Just a theory, but wasn't sure if it made any sense.
Robotman: i have owned the SW200 in the past and had a similar if not identical problem. At low volumes, just fine, but turm it up and the broke up badly. Mine went back to Kinergetics, they were still in business then, and they replaced the power supply filters. It was running the power supply out when wanting higher currents. nilemi
Thanks for the info! This sounds exactly like what's happening to mine.

Do you think my power supply is damaged by now or do I just have faulty filters that fail at high loads?

For that matter, what are power supply filters and how easy can they be replaced? Sounds like a generic part that maybe someone can help me replace without being an audiophile.

Too bad Kinergetics still isn't in business. I feel stuck now.
While I suspect the Kinergetics needs to be seen by a tech. In your previous thread you indicated that your room is 15 x 15. I'm guessing that your ceiling is probably 8' high. Ouch, that the largest dimension is only 15' limits bass response. Those dimensions, which include exact duplicates and the third being roughly one half, compound the problem and is most likely going make bass response uneven. The point being that your room, no matter what the gear (with some unique and notable exceptions) is most challanging, and especially with regards to bass. Perhaps you might want to reconsider your expectations?
I think you are right with the room size, although this problem seems more than just a limited bass response. It seems like a bass malfunction or overload at louder volumes. I'm not sure if speakers overload if the room is too small, do they?!

Definitely will look into a tech to check out the Kinergetics, though. I wish I questioned the problem more when I got the system years ago!

Thanks again for your input!
If both SW are doing the same thing the problem might be the signal they are getting from your receiver.
Eldartford has a good point. Have you checked the cables and especially the connections?
Robotman, after you check the cables and speakers, go through your audio menu on the dvd player and the HK volume tweak settings. I have a HK AVR5 and Kinergetics SW200 amp and I did have problems with it. If you are using the SW200 Compusound 2 mono amp, which I am using, it clipped constantly when I used the THX input. I ended using the l&r inputs on the amp with the the toggle switch in norm, not THX. This way I could use the volume control on the front of the amp if I needed a change. If you have full range fronts, try selecting sub off, fronts large on the dvd menu, fronts large on the Hk and use the front pre-outs on your receiver. You should experiment with different settings on the dvd and HK menus. I did try this amp on my music system and I can blast the Kinergetics with no problems, even at a 4 ohn load. The only time a fuse would go was when it is turned on or off. Once you get it on, leave it on, unless you want to keep replacing fuses.

Good luck and keep in touch. You just may have a frustrating task on your hands, especially using the remotes. Now, does anybody know how to lower the xover on these amps from the current 80hz? Info would be appreciated.
While I certainly don't want to contradict Eldulcesol's first hand experience. I think it prudent to warn you that the Spicas are not full range or "large" and are not know for durability, original replacement parts may be hard to come by and matching other drivers around their unusual cross-overs might be tricky. You might want to excerise some caution in shifting some of the burden of the Kinergetics to the Spicas. THX usually rolls off a bit of the top end something the Spicas tend to do on their own. As such I suspect there is some very good suggestions here, keep the volume down and proceed with caution.
I did some experimenting over the weekend.

The Spica's are not full range speakers and if I don't call them "small" speakers on the HK receiver, NO signal will be sent to the subwoofer. Granted that they are physically large speakers, but their range is considered "small".

The SW-200 are "stereo" L and R subwoofers which have two 10" speakers in each box. The HK sends out a pre-amp mono subwoofer signal cutoff at 100Hz, so I split this and then go in the L/R pre-amps on the Kinergetics amp.

I found an old Enya CD which had some good simple monotone bass notes which helped me diagnose a bit more.

I tried switching the L/R speaker cables from the amp to the speakers. The problem stayed on the right speakers after the switch. This tells me that the amp is not the problem, but the right speakers themselves are having a problem.

But here are some notes / questions:

1. The problem is that both 10" speakers inside the right speaker sub box are vibrating to their extremes causing a jackhammer sound. This originally sounded like out-of-control, distorted, popping in the bass movie scenes, but with the clean Enya monotone, it was a steady pounding noise and I could visibly see what was happening.

2. Although the right speaker set has this problem, it sounds perfectly fine until it gets turned up to a loud volume.

3. I can turn the left speaker sub up quite a bit more and get it to do the same thing.

So... does this sound like a problem with the right speaker set or possibly a small room problem? I was wondering if there is some effect I don't quite understand where the speakers aren't able to create the bass they are trying to generate which causes this over excursion problem and speaker jackhammer effect. If it is actually a problem with the speaker, what could it be since they sound fine up to a point?

Any ideas welcome. Thanks for all your help!

Robotman, for me I had to use a 5.1 out on the dvd player to the 6 ch. in on the receiver. What I did was set everything to large, sub yes,set the distances, effects and volume controls almost to the max. This is on the dvd player menu. Check also to see if your dvd menu has a sub freq. on it.

After that, then try to tweak the volumes with the HK. I believe the SW200 xover is 80hz. If you can, adjust the sub out freq on the HK to that. If you are finding out that the tweak volumes on the HK are at two extremes, fronts -10 center +10, go back to the dvd menu and make some changes. All this is possible if your dvd menu has the capability to do this.I know all of this is a pain, especially if you have to go through 4, 5 steps just to get to the audio menu on the dvd player as I had to do.

Try the other suggestions from above about placement and not plugging the amp to the HK. Also, if your are not sure about the condition of the amp and subs, try it out with a different receiver or system to be sure.
If these SW are acoustic suspension (sealed box..no vent) your box might have a leak. Tighten all the mounting screws on the drivers. Check for any other source of leakage.

Test the polarity of the drivers by touching the speaker wires to a battery. Make sure that the cones move in the same direction.
It is a sealed box. I don't see what I could tighten on the box. What are the drivers? An air leak would make some sense, although everything seems really tight on the speaker box.

What type of battery would you use to check polarity? I assume you mean compare the the left pair of speakers and right pair of speakers move the same direction? Or do you mean the two speakers in one box? I can also just try reversing the red/black wires on the right side and see if that makes any difference.

I don't have an expensive DVD. I'm just using a PS2 or TiVo as the source through an optical cable for movies. I also read in the HK manual that if you set your speakers to "Large", there will be NO signal set to the subs. I didn't confirm this, but I will.

I did try plugging into the wall and didn't notice any change in the problem volume point.

Thanks for all your ideas!
Robotman...The "drivers" are the things with cones that move in and out. Since your SW has a built-in amp I guess that you can't get at the amp output wires that go to the drivers. If you could get at those wires, a 9 volt battery momentarily connected to the amp output terminals (and therefore to the drivers) would verify that the two drivers in one box are not hooked up with opposite polarity. That would be a long shot but worth checking if it was easy.

Your sealed box could leak around the drivers. or around the amplifier if it is in the box as I suspect. Tighten the screws everywhere, and use silicone rubber sealant if the gasket is faulty.
The subs have an external amp. I highly doubt that the two speakers / drivers would be crosswired inside the sealed speaker box. I also can visually see that both speakers in the box are moving in and out in unison.

Would reversing the black / red speaker wire have any effect? I didn't think it really mattered which way you hooked up the speakers. I'm pretty sure everything is matched up, but just one more thing for me to try.

I'll also make sure everything is sealed well, although it all seems pretty rock sold.

Is there anything inside the speaker box that could be failing? I wasn't sure if there are any electronics inside the box itself.

Thanks again for your ideas.
Robotman....If the amp is external you could easily check for "crosswireing" using a battery, but perhaps you can do this by observing the cones during music. The battery is just a more definite method. Agreed that this would be unlikely.

Reversing the red/black speaker wires will have no impact on your problem, but would screw up the proper phasing of the left and right SW.

Try a different power amp.
I need to find an audiophile friend in my area who would be willing to bring over their amp for me to try out.

The Kinergetics has separate L/R channels. I can hook up the right sub to either channel and the problem still occurs. This makes me suspect something in the sub box itself.