I have a customer whos kids keep blowing the outside speakers,
the amplifier is in the next room and is controlled via a control panel.
Is there any way of monitoring / displaying the volume outside and if not what is the best way of protecting the speakers?

Thank you.

If the problem is that the kids don't know how loud it is, then why don't you try and set it up so that they can control it from the other room.

The problem is the kids DO KNOW how loud it is: When the cat's away, the kids R gonna rock the house no matter what anyone says. (Rock On Kids !)
Get them beefier outdoor speakers or make it a zone and set up a keypad or volume control that has a "preset max volume" setting for that zone. My control unit has that function and no matter how many times the UP arrow on the keypad is pressed the local volume will not exceed the preset.

Perhaps the owner will spring for smallish PA style "outdoor event" speakers. They won't be audiophile grade but do you think the kids will know the difference while they splash in the pool/yell/scream? What the kids really want is BASS: Maybe you could install (sell) one of those subs that you bury in the planter - they'd probably still just crank it up.

I agree - if speakers are continually being blown, I'd investigate speakers that can take more punishment!

It's usually not the speakers fault. It's usually them clipping the input signal to the amplifier that's causing the speakers to blow. Square waves in an audio signal is NO GOOD!

Most of the time, a speaker should have 3 times the rated amplifier power. I've very rarely heard about a speaker blowing from too MUCH power. You really need to calculate how loud you want the sound level to be at the distance they are really using it and pick the speaker that is efficient enough, or has enough power handeling to deliver that kind of level that distance. If you want more info on these calculations, just give me an email. It's fairly basic really.

Not having visited the site most of us would be hard pressed to precisely identify the root cause of CMO's problem. Trusting that CMO has already done some investigative work I have to assume that he says he has a "customer whos kids keep blowing the outside speakers" because he believes that is roughly where the problem lies.

CMO: HAVE you assessed the amplifier AND the speaker cabling?

Until recently consumer-level outdoor speakers have been designed to produce "muzak" at best. There's no substitute for cubic inches, and even speakers with a mid-bass hump are going to give after being tasked to continuously perform duties they are inherently incapable of.
Under 8" (minimum) woofers = no REAL bass. Kid want bass = Kid kill speaker = Dad buy more.

Even the kids in Ghana and S.A. listen to rap and hip-hop. With a few exceptions the majority of mass produced consumer-grade outdoor speakers are just not going to last very long at ANY elevated levels, especially while being pushed to reproduce lower frequencies.

CMO: Once you exonerate the speakers as the culprit you MIGHT consider lightening their burden by limiting the low end sent to them. If there's no built-in method in this installation for limiting the lower frequencies you could also try using passive inline crossovers like Harrison Lab's FMOD's or PMOD's.
If you do decide to implement crossovers you could still limit the volume to the satellites and add a sub to satiate the little angels. (Probably have to limit the volume to the whole outdoor zone if you do add a sub - mad neighbors could sound worse than blown speakers.)

Although it's usually not the speakers fault you could use fairly basic calculations to pick the speaker that is efficient enough, or has enough power handling to deliver that kind of level at that distance.

To add to Matt's input (no pun intended), it's usually the tweeter that bites the bullet from clipping. The leading and trailing edges of square waves produce a lot of ultrasonic noise because of harmonics, and these high-frequency signals overheat the tweeters' voice coils.

Especially if there is more than one pair of speakers, I might suggest a separate (possibly multi-channel, if there is more than a single pair) amp to power the outdoor speakers. This way, the power delivered can be both regulated and assured to be up to the task.

Larry
www.fineelectricco.com

Before anyone can make an accurate assessment, it would be helpful to know a little bit about the system.

What kind of amp is being used? How many channels? What type of power output? What type of speakers? How many? What is the "spread" of the speakers (How are they laid out, how much area are they covering, and what is the ambient noise level.)?

Knowing some or all of the above will help greatly in suggesting a solution.

JJP

Sage advice from JJP for posters and prognosticators alike.

Really all we need to know is...

1) How far away do you want to listen?
2) At what level do you want to listen at that location?
3) The sensitivity of your loudspeaker of choice.
4) The power handling of your loudspeaker of choice.


From this data you can calculate how big an amplifier you need to drive these speakers at your given level at your given distance. Now, if your speakers cannot handle the amount of power need to reach that level based upon your specifications, then it's time to look for a new speaker. This is probably your entire problem in a nutshell.

I have to disagree. More information is needed to accurately calculate the system design.

Following the items above in the design without considering the ambient noise level will result in miscalculation of recommended equipment specifications.

And again, it's more likely to blow a speaker from clipping (overdriving the amplifier), than from supplying the speaker with too much power.

The biggest mistake made when equipment is installed, is failing to, or incorrectly setting the level match between preamp and amplifier. Proper level matching and setting the limits of the system, will generally yield a long lasting design.

JJP



This message was edited by John Pechulis on 05/12/02 20:35.06.

This was simply design of the speaker amp power match, not the entire system design. But with a proper amp/speaker match, the preamplifier should simply not have any volume control what so ever, each speaker should be on it's own autoformer or some type of line level volume control. This will eliminate the clipping problem found in most if not all multizone audio systems that are not done with a 'system' type solution such as A/D/S Dominet, AudioControl Director, you get the idea.

Well, in most cases, ambient noise levels of sound systems in homes will not come into play. If your trying to reinforce sound levels that require this type of calculation, definatly don't do it as part of a multizone audio system. Set up the mixer in the back yard for those kind of parties.

But I agree totaly on the clipping part, but what a lot of people don't understand is that it's not the speakers nor the amp, it's you turing the preamps volume control to 'make the speakers louder' thus clipping the input stage of the amplifier. Most preamps will drive the amlifier to full output at about 12:00 or so, with a recording of proper levels. Of course you need the extra gain for that poor/low recording you want to listen to. Thus, I say run preamp at near max levels into the amplifier, and use external VC's for each set of speakers, NOT the preamps VC. This small extra cost of a system will save many headaches for the end user.

This message was edited by Matt on 05/12/02 22:50.09.

Again, without having knowledge of some or all of the system design, it is impossible to give an accurate possible solution to the originally stated question.

Autoformer volume controls are good at stabilizing the impedance seen by the amplifier, but in return, they absorb some of the output power from the amp which is lost in the form of heat. And autoformers of the commercially available variety are bandwidth limited.

Really it all depends on what you're trying to achieve.
If you're looking to create a level of sound close to reinforcement levels outdoors, then speakers and equipment of the "Home Entertainment" variety aren't going to cut it.

JJP

Sorry to disagree, Matt, but it's the output stage transistors' clipping that does tweeter damage. A severely-clipped sine wave looks a lot like a square wave, and square waves are notoriously noisy.

A clipping stage ahead of the output stage will not pass the same damaging high-frequency noise. It's the output transistors' being driven to the point of saturation (full-on) that define's clipping. The amp output approaches the power supply's rail voltage. (Typically 0.6v drop)

Transistors are great devices while operated within the linear region, but they are less than ideal near either extreme of their voltage swing. Noisy near turn-on level (which is why the A/B class of operation is so popular, where both polarities of the output devices are never fully off at the same time.)

With class-A amps, neither polarity is ever fully off. The power dissipation doesn't change with loudness. This is the cleanest amp, but the least efficient. With class-C amps, one polarity is fully off as the other is at the threshold of conduction. Noisiest, but most efficient. Class A/B is considered to be a design compromise.

Lastly, a weak power supply can cause premature clipping because the supply voltage drops just when (and because) the output current is the greatest.

Larry
www.fineelectricco.com

CMO: Looks like it IS rocket science! Quick; post an existing equipment list that includes every piece that contributes to the signal chain that leads to the outdoor speakers. Source (reciever?), pre-amp, amp, zone controller?, remote volume controls?, cabling including approximate length of the runs before and after keypads/volume pots, guage of the cable, model of/specs of/number of speakers, so we can stop the prognostication.

OR: Charter us a plane to the UK ([Link: gulfstream.com]) and we'll do an onsite group consultation. (You can pass the savings along to the customer.) Meanwhile he's buying the kids a boombox and losing your phone number: Problem solved.