Point well taken Larry, but I guess where it's clipping is not important in most cases, both 'kinds' of clipping destroy speakers, by either delivering high frequency noise, or by simply delivering DC to the voice coil of the speaker, thus pretty much welding it to the gap if it's long term. Also, when you clip a signal you deliver about twice the ouput power of the amplifier to the speaker, and if your speaker is not rated for these power levels, whamo.

But it is interesting to see everyone's input into this common problem with budget audio distribution issues.

John, Yeah the autoformers lose some power, but how much to heat, I mean have you ever felt a warm autoformer in a wall? But wouldn't you agree you need to keep the gain structure to the last stage volume control at it's absolute maximum signal level? Letting the VC in the wall attenuate the signal to the level you want? I guess that's what I'm saying...

How bout this, guys...

Take the tape out from your system. It's a fixed level signal.

Run it into a power amp with gain controls.

Set the gains to the loudest your customer's likely to want it. Set an autoformer outside (I like the Russound Walt2), so the customer can turn the signal down or off.

Voila. Kids can do nothing to damage the speakers, because you have given them the ability to turn the level down only.

Collect your check.

Yeah, gain structure...

Hey CMO: We've not heard from you since you posted. There are learned/learning people discussing your install. Give us some particulars so we can quit chewing on air.

Did you resolve the problem? If so, how? Maybe we'll learn something from you.

I totally agree.


I've just never been a big fan of autoformers. You can hear a difference between using one and not using one. And most of the clients I deal with don't like "knobs".

Like I said before, it all depends on what you're trying to achieve. And I agree that the use of autoformers in the average "muzak" level system is a cost effective way of designing a long lasting system.

JJP

'They' make some great VC's these days.... pretty much flat from 20 to 20K. Check out www.audioplex.com.

If your not a fan of autoformers alter the line level signal feeding the amp, then use a line level system. Radio Desing Labs make some great VCA's.

Hi everyone, sorry I haven't replied earlier as I have been away for the last few weeks.

Superb response from you guys and some interesting opinions.

The original setup has changed somewhat, it was originally a Rotel RC972 pre amp with a RB971 power amp and a pair of Sonance Mariner 200 speakers
(Rotel was off their original hifi system).

The problem wasn't that the speakers weren't loud enough(they have neighbours after all) but that the kids (teenagers!) kept turning the volume up too much
and blowing the speakers. This being possible because control was through a Xantech WPK1 waterproof (outdoors panel).
Sheik_Yerbouhti - you mentioned that you used a panel that had a volume limiter on it. How does this work as the Xantech simply relays infra red commands back to the Rotel pre and doesn't monitor the actual volume in any way.

Anyhow the system has now changed to the same Rotel RC972 and a Rotel RB1066 6 channel power amp along with three pairs of Boston Voyager pros, since the Rotel power amp has gain controls for each stereo pair I can limit the maximum volume.

For the technically minded here:-

speaker cable is QED Qudos (heavily shielded 79 strand, not sure on equivalent gauge) about 5m, 10m and 15m stereo pairs (er about 17,33 and 50ft).
Ambient noise probably depends on the weather, screaming kids.

I don't suppose this is the most theoretically technically correct way of getting the best from the speakers although it does let me sleep easy at night and not having to dread the next phone call of 'The've blown again'.
I just hope the little blighters don't discover the gain controls!

Thanks again for all your advice

Or the volume control of the Pre amp...

Unless it's a fixed output level, you could still have the same issues at some point.

Why do people have to make things so hard gee wiz.
Any dumb kid whos messed with their car stereo knows how to get around a volume nob on a remote amplifier. Install a compressor limiter behind a security face plate AND install an inline fuse for the speakers. you could also measure the resistance of your volume setting and replace the volume control with a resistor. Please don’t give me any of that oh it will hurt the delicate balance of the sound, out door speakers will never be that good. If the kids need the base all that bad, sell them a sunfire sub in a garden rock kit, that will wake up the folks next door.

Enjoy

cmo: What I said was..


That max volume function is decided at the multizone controller itself when the system is setup - the keypads are uniquely addressable. Each keypad has a home-run of Cat5 to the controller. (They are daisy-chainable but if you've got a bad wire it's more work to troubleshoot.) When the controller gets a request it knows (by keypad address) which zone requested which source and the max volume that should be sent to that zone. No audio signal is distributed to or through the keypads, rather the keypads each send installer defined pre-programmed commands back to the controller via the Cat5. The controller has six 40wpc stereo amps and the audio is sent directly to each zone's speakers through regular speaker cable as commands are entered at a given zone's keypad. These keypads also accept and relay IR commands to the controller which then distributes them to the sources. The controller and keypads are both from Audioaccess.

There are keypads that DO have the volume limit function at the keypad - I read another post that mentions Russound having governors on the back.

Matt, the Xantech control pad actually controls the Pre-amps volume control up to max.
By setting the gain controls on the power amp it was possible to set the max volume with maximum pre amp volume to each speaker pair.

Sorry if this was unclear.