Can I suspend / hang speakers?

All right, I'm setting up a home theatre for dad (father's day and all), and he'd prefer to suspend the rears from the rafters rather than have stands. It know. Can someone give me a sound technical reason this is a bad idea? Thanks. -Dave
Seeing that no one else has answered I think I shall!

I cannot see any problem with doing it as I have thought about it myself.

As long as they are suspended correctly ,taking how they should be if on stands and vibration is minmised.

If the tweeters are at ear level the speakers should perform adequately and maybe better seeing there is no stand involved.

Just thinking!
The tweeters don't have to be at ear level; they can be angled downward so that they are pointing at ear level. I helped a friend install his home theatre and we hung a pair of Linn Tukan bookshelf moniters and a Linn Centrik from the ceiling using mounts from Good Guys. The Tukans are rear ported and sound great on the ceiling; just enough additional bass from the ceiling to give them a little more weight.

Just make sure the mounts you use are more than adequate for the speaker; ie, don't use one rated for 30 lb max for a 30lb speaker. Get a larger mount in that case; overkill it.
Sorry, I wasn't clear. He's talking a non-rigid mount, like with chain, rope, etc., that could be raised and lowered easily.
Non-rigid mount would be a bad idea, since the speakers would move in the opposite direction as the cones, according to Sir Issac Newton's First Law of Thermodynamics (at least I think it #1)- for each action there is an equal and opposite reaction. Only a little bit, but think how hard we try and make sure that speaker stands are rigid.
I did this in college when I lived in a storage room for a term (cheapest rent ever!) Hung 2 Boston Acoustics A60s from the rafters. Can't remember if they sounded good because I was drunk most the time. I doubt they did. There was a hardhat on the wall, in case anyone felt uncomfortable with it.
Yeah hanging from pipes mounted to the ceiling Joist would be sonically much better, all things considered(should strongly consider finding best sonic placement "in space first"). simply letting the speakers "hang" wouldn't sound so good, unless the speakers were "so heavy" they wouldn't react much to movement in the speaker.
I would "X" the hanging idea with chains, etc, yes. I mean, if the speaker is haning there anyway(obstructing walkways, etc), you might as well "hard mount" the suckers!
Someone has to say it...

It was Newton's THIRD law of MOTION
vs 1st of thermo.

"For every action, there is an equal and opposite reaction."

If I didn't think Newton was the greatest scientist ever I would have kept my mouth shut. Regardless of the historical slip you make an excellent point regarding the tendency of suspended speakers to shake themselves rather than produce sound.
Thank you Wade- Its been over 30 years since I studied any physics. I was just guessing on which law. I'll gladly take you word for it.
Here is required reading for rigging flyable speakers from ATM-Flyware:

If you don't do it correctly, DON'T do it at all.
Poor Issac must be spinning in his grave! Yes, the voice coil will push with equal force on the driver cone and on the speaker enclosure, but Newton also came up with F = M*A, which tells us that movement of the massive enclosure will be tiny.

The only drawback to hanging speakers by chains is cosmetic. If the wife agrees, go for it.
The movement of the enclosure will indeed be small, but given the generally universally accepted goal of rigidly mounting speakers, why in the world would you hang them in space, to let them move (swing) on their own? Imagine a recording with bass almost entirely in one channel, with large excursions of the woofer and small excursions on the other side, sending the imaging info all to !@#$. Remember that our ears/brains use millisecond delays to localize sound. YOu would't consider mounting speakers on a columnar spring which could move around in response to the driver motions; isn't this similar to what you are considering by hanging them? Maybe one of our speaker designer/builders could chime in. Maybe my intuition is completely wrong here.
Swampwalker, be carefull of intuition and "common sense", they are what people use to explain that heavier objects fall faster than light ones.
The movement caused by the counter movement of the speakers can be calculated to be virtually, if not literally, nil.
inpenin- I agree with your comment on intuition. Point made. However, I do not believe that allowing a speaker to move freely in space (even a small amount) is beneficial to good sound. I must admit I will NOT hang my 90 lb Merlins from the ceiling when they arrive to experiment.
Ok, has anyone done the math? I'm no physicist, but can't you figure out the force caused by the displacement of air for a single note, the force caused by the movement of the voice coil, and, based on the weight of the speaker, figure out how much reverse displacement would be caused? Wouldn't that give you a damping factor? Granted, its probably totally ballpark, but I'm guessing to would not be "virtually ... nil."

I'm curious, because of my experience with my old ProAc RS2s. They sounded awful until I mounted them on the recommended Target sounds, and then they sounded awesome.
The speaker cabinet will indeed move in response to the cone and this movement will be quite small by daily human standards. However, this small movement IS in my view enough to smear the sound. I cite the same reasons as others on this thread for rigidly mounting speakers to stands.

Given that woofer cones are generally made to be as light as possible and that the reverse is true for speaker boxes, the reaction movements of the box are indeed very slight, but not in my view insignificant.
Bottom line is that this system is for "dad" who is not likely an audiophile, else he'd be setting it up himself. With some folks esthetics, convenience, whatever far outweigh imaging, purity of tonal balance and the rest of our arcana.

My advice is to make sure that the system is safe - the hooks have adequate safety margins, the cables don't get tangled with the raising/lowering, etc. - and then let your dad enjoy it.
The positive aspects of suspending speakers are complete mechanical isolation from the floor (so that it doesn't vibrate) and removal of the speaker from all adjacent surfaces. (You would not, for example, put the speaker right next to a side wall).

As to speaker addition to being a tiny force applied to the massive enclosure, it is at the wrong frequency to induce "swinging". The pendulum frequency of the suspended speakers will be lower than one Hertz, and no loudspeaker goes quite that low. Finally, musicians do not clamp their instruments into rigid mounts as they perform, and neither do audiophiles clamp their heads when listening. The instruments move about at least several inches, so I can't believe that tiny speaker movement is would be a problem.

As always, those who have not tried the idea are on thin ice when commenting. For cosmetic reasons my speakers are not suspended, but I have heard excellent results from suspended setups. In fact, many years ago I heard the original Bose speakers hung about six feet in front of a brick wall in a warehouse with a ceiling of about 20 feet. You would not believe how good they sounded. I have also heard Maggies hung near the middle of a very large room with high ceiling. Also superb.
This thread seems to have just about died - but in hindsight it looks like a Michael Moore film: Lots of itty-bitty factual pieces taken and spun to support the outcomes each of us are after.

For my closing remarks on the physics of this situation - the system will certainly be enjoyable to even the most prudish audio nut provided at least most of the other considerations are taken into account. Just as the poor electrical/vibrational/speaker positioning environment doesn't preclude us from enjoying music in the car, the slight change in rigidity due to suspending speakers do not prevent people from enjoying the stereo system.

I do have to disagree with the statement by Eldartford regarding...
"The positive aspects of suspending speakers are complete mechanical isolation from the floor (so that it doesn't vibrate)"
The speakers are not isolated from the floor - and this is not in reference to an abstract and academic concern regarding the inability to achieve "complete" isolation as cited above. The suspended speakers are simply another coupled element in the system although the speaker supports (chains?) have the unique ability to have no meaningful compressive load resistance, this does not mean the element (speaker) is isolated from the rest of the system.