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#359578 - 11/28/11 02:30 PM Re: VP150 [Re: MarkSJohnson]
hawk1061 Offline
frequent flier

Registered: 11/26/11
Posts: 19

Thanks for the responses. However I'm not sure what you meant by 'clipping'... I am guessing that you mean i have the volume turned up so high that the amplifier in the receiver is overpowering the ability of the drivers to handle... Is that correct?? Is there a way for me to know whether I am in that mode? Would the receiver 'cut out' possibly, as though it was overheating and tripping a thermal breaker? Or would there be some other indicator??

Reason I say that is because my wife did say (now that I think about it) that she thought there was a problem with the receiver and that 'it just stopped working' a week or two ago... When i turned it on briefly i noted that it was working so i just dismissed it as a case of operator error, a one time fluke... Possibly she was jamming and she burned them out and I just didn't do enought testing?

Just noodling the room and adjacent rooms. Great room is 17x17 feet. Assuming the main floor is say 10 foot that would be a volume of 2890 cubic feet. Guesstimate half again for the cathedral ceiling so call it about 4500 cubic feet. The adjacent dining room is 12x14x10... Call it another 1700 cubic feet. The foyer/entry/stairs abutting the great room would be appx 15x7x18 for 1890 cubic feet. So a reasonable guesstimate would be about 8100 cubic feet (give or take a bit).... Knowing that, what are your thoughts??

Regarding loud... My ears haven't bled so it couldn't be loud....

#359581 - 11/28/11 02:39 PM Re: VP150 [Re: hawk1061]
Murph Online   content

Registered: 10/05/06
Posts: 6812
Loc: PEI, Canada
Hey Hawk,

Clipping as actually when the receiver is asked to produce more power than it can cleanly produce. In the case of clipping, the root cause is the receiver, not a weakness in the speaker. Specced to handle 400 watts, the VP150 can probably actually handle much more power than your receiver is capable of 'cleanly' producing.

If you turn up the volume to the point where the speaker needs to draw more power than the receiver can produce, then the receiver tries to oblige but the effect is that the top and bottom of the frequency wave gets "clipped" off (thus the term "clipping") because it's hitting it's limits at that point in the sine wave. The result is a squared off wave and this type of distortion gets increasingly audible the more you push it and eventually becomes damaging to speakers.

A regular sound wave.

A clipped sound wave.

Most modern receivers will shut themselves down before too much damage occurs but there is always this inherent danger if you push volume levels too high.

Edited by Murph (11/28/11 02:50 PM)
Edit Reason: added pics
With great power comes Awesome irresponsibility.

#359593 - 11/28/11 04:03 PM Re: VP150 [Re: Murph]
dakkon Offline

Registered: 02/08/04
Posts: 1846
Murph, thanks for explaining the clipping definition.

Most of the time in a situation like this, the speakers can actually handle much more power than the source is capable of providing, so the source (amp) is actually the cause of the problem, blown drivers is just the result.

Ask your wife if she remembers how high she had the volume turned up when the receiver "shut down", if she had the volume turned up almost to max, the receiver could have gone into thermal shutdown mode. This is to prevent any damage to the receiver, not to your speakers. Part of an amplifiers ability to produce power is it's ability to dissipate heat. For example, if you have a forced cooling setup, a given amplifier can produce more power safely than a an amp with only passive cooling (similar to over clocking a computer). Keeping the transistors cool is the number 1 goal in this instance. The way that power amps are able to produce much more power than receivers is that they have many more transistors, as well as much larger power supply and capacitor sections... But the point being, more transistors= less work/heat generated per transistor.. If you look at the large amps produced by many of the high end companies, they will have HUGE aluminum heat sinks that their transistors are bolted to... to dissipate as much heat as efficiently as possible.

So, where is your receiver located? Does it have lots of open space around it that would provide a natural efficient radiant cooling? On my AV rack, each amp has 1' of clearance above it to ensure that there is enough room for unobstructed airflow.

Room size, I would tell you to wait for Alan to give his opinion, or call axiom and ask Brent/JC. Any of those 3 guys will give you a realistic recommendation without trying to over sell you on your true needs. However, in the mean time. Try to quantify "loud" do you mean the same level as a rock concert? Movie theater? opera? Jet engine from 3' away? Try to come up with a real world relation that you can make, to give them an accurate level that you and your wife are trying to achieve, this will help them give you a good recommendation. The last thing you want to do is spend good money after bad, and not get the results you are truly looking for.

I think that in a way you have opened a can of worms my friend. I have a feeling the recommendation that you will receive will involve buying larger speakers.

#359594 - 11/28/11 04:14 PM Re: VP150 [Re: Murph]
hawk1061 Offline
frequent flier

Registered: 11/26/11
Posts: 19
Murph, thanks for the info. You said that most modern receivers will shut down before too much damage occurs, I wonder if that's what my wife described. I will ask when I see her tonight. Maybe it's happened more than once, I know I've never experienceda case where it shutdown. I wonder if the HK AVR7200 is modern enough to shutdown it detects clipping.

#359595 - 11/28/11 04:17 PM Re: VP150 [Re: dakkon]
J. B. Offline

Registered: 01/19/11
Posts: 1269
Loc: Quebec, Canada
Quote: "Regarding loud... My ears haven't bled so it couldn't be loud...."

wow! that must mean you like your movies/music very loud.
if that is so, then the minimum you should buy is M80 speakers and around 300 Watts per channel or more into 4 Ohms.

if you want to protect your equipment, try to find amps that have led peak indicators; if you have difficulty finding those, have a look at proamps, most have those peak indicators.
if those led's ever light up, then you lower the volume a little bit and you'll be ok; and the equipment too.

a good subwoofer would also be a good addition; your front speakers will work less hard.

others here will surely give you better tips than me.

Edited by J. B. (11/28/11 04:19 PM)
or: Axiom Gallery

#359596 - 11/28/11 04:34 PM Re: VP150 [Re: hawk1061]
hawk1061 Offline
frequent flier

Registered: 11/26/11
Posts: 19

Yes I will get more info tonight regarding what level she was running.

The receiver is on the top shelf of the 3 foot tall shelving unit. Normally there is nothing stacked on top but recently there have been DVD cases left on top of the receiver which would block the top vents. The Harmon Kardon AVR 7200 has passive cooling and has large aluminum heat sinks on the left and right side of the chassis. There is nothing blocking the left/right side vents.

So if clipping is the issue, one obvious answer is to reduce the max volume used. Another is to add a separate amp to drive the center channel (not sure why I would only drive center channel, is that to "spread the work out" so the separate amp is not overloaded into clipping mode)? Or I could upgrade to the VP180 (but then what of the M22's, are they at risk too?). What about my subwoofer (SVS cylindrical powered subwoofer 12") is that in danger or since it is already powered with its own amp, it should be safe?

Regarding loudness I would say as loud as a movie theater when playing movies. I don't think she typically goes much louder but who knows when I'm not home...

#359597 - 11/28/11 05:15 PM Re: VP150 [Re: hawk1061]
tomtuttle Online   happy

Registered: 06/20/03
Posts: 8284
Loc: Tacoma
Hawk, make sure you check the settings, too. It's not just "how loud" but "how loud at what frequencies" that matters.

Murph or somebody else smart already alluded to running the speakers as "large" which you probably should NOT do. That is, have the crossover in the amp send all signals below 80Hz (or whatever you choose) from all channels to the subwoofer. If your receiver only has to push signals above that frequency AND your speakers only have to produce signals above that frequency, everybody will be a lot happier. So, noodle around in the settings on your receiver some.
bibere usque ad hilaritatem

#359615 - 11/28/11 09:33 PM Re: VP150 [Re: tomtuttle]
dakkon Offline

Registered: 02/08/04
Posts: 1846
i think that all receivers have 1 power supply, that power supply is providing power to all channels of amplification, all processors for the signals ect.

the more powerful outboard amp is so that you can get the same volume without driving the amp into the clipping region on the affected channel.

the center channel is where 70% of the audio information in a movie comes from, hence the reason i was recommending a 180 to replace the current 150, and why Alan recommended an outboard amp. if you had blown the pair of m22's the recommendation would have been different.. you were trying to get the 150 to do a job it is not large enough for i think... You just need a larger speaker with more drivers.. The SVS, it depends on if you are driving it past the amplifiers limits.

This whole conversation can be boiled down to staying with in "design specifications"

I would say call axiom if you haven't already, and tell them the situation and see what they have to say. They do this stuff all day every day, and have experience with rooms such as yours i'm sure.

#359624 - 11/28/11 09:49 PM Re: VP150 [Re: dakkon]
hawk1061 Offline
frequent flier

Registered: 11/26/11
Posts: 19
So, now I know "the rest of the story"... My wife had a birthday party for her girlfriend and she had all the girls over and were playing the stereo "real loud" for "a while". I asked her to define those loose terms. She said they had it going for over an hour and had it loud enough so they could 'hear the music outside' which is where they were hanging out... mind you that was the other side of the house. So, I suspect the clipping theory is the most likely one.

Knowing that, I am now concerned that the M22's could have been damaged at this gala event... Any way to test them to determine if any damage has occurred?. Ditto on the subwoofer.

Now it's a case of what option to choose.... Replace the blown drivers, get a new VP180 to replace the VP150, get a new receiver able to withstand her onslaughts, or a new amp to drive the center channel.

#359629 - 11/28/11 10:23 PM Re: VP150 [Re: hawk1061]
alan Offline

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
Hawk, lots of speakers get blown at parties when users "crank it up" in the spirit of the occasion, especially when drinks are flowing.

Try playing a CD, one with cymbals, vocals and good bass in stereo, turn the balance control all the way to the left, and listen to each driver of the left M22, with your ear fairly close (use a moderate volume level) while covering the other two drivers to make sure you are isolating each driver. Usually, the driver will work fine or it won't issue sound at all. If the voice coil is warped from heat or overdriving, you might hear a distorted scraping sound. You can also use the battery check I described to check the woofer/mids. Repeat the test for the right M22, turning the balance control all the way to the right.

By the way, your H/K has good protection circuitry, but that's used to protect the output stage of the internal amplifier, not to shield your speakers from clipping damage.

I doubt the subwoofer is damaged, but you can try gently pushing in the cone of the driver with your hand (with the subwoofer switched off)and fingers applying equal pressure. You should not hear anything if the subwoofer is undamaged.

If you do hear a scraping sound, then the voice coil has become warped or fused from overheating/clipping and is scraping against the magnet assembly as you press the cone in and out.

If you're really planning on playing stuff super-loud, then you need an outboard amplifier for at least the front three channels, and preferably larger floor-standing speakers like the M60s or M80s. Either that, or keep the M22s, get an outboard amp and a new or repaired center, and control the maximum volume level. The M22s are great little speakers and will play remarkably loud and clean when supplied with clean unclipped power in an average living room or slightly larger space, but I really think your much larger room demands bigger more capable speakers and a big amp.

Alan Lofft,
Axiom Resident Expert

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