If I wanted to buy some used active monitors, what should I be aware of ? For instance, if the monitors have been really thrashed then it would probably be possible to see / hear it in the cones / drivers. But if they've been replaced, what damage could have been done to the amplifiers, and what would it sound like? I have very little knowledge of anything outside the hi-fi world.

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"There's only 45 degrees between the Hitler and the Zombie" - me, Saturday night, in front of the speakers

I'd say if they sound fine, feel fine, don't rattle when shaken and are reasonably priced, go for it. It's the same with buying anything s/h - but faults aren't obvious straight off, and may become apparent after you've been using the gear a while.

Amplifiers and monitors are probably safer to buy used than most things - provided you can see and hear them before you hand over the money. Any faults are usually obvious - they'll sound strange or you'll see torn/deformed diaphragms.

Some people will even tell you that well run in speakers and amps sound better.

Cheers.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

here are two very good tests for second hand speakers of any kind. After listening to your normal selection of music (and speech if possible -- far more revealing of tonal problems)...:

1. switch the feed to mono. You should here a tight, well focussed central sound source. If different frequency components appear to wander left and right of centre there could be a driver (or amp) frequency response problem. Beware though that such image shifts can also be produced by nearfield reflections from side walls, computer screens and so forth. If in doubt, resite the speakers somewhere less cluttered and try again.

2. Still with a mono signal, unplug each speaker in turn and listen carefully. They should both sound the same. If they don't one is poorly! This kind of problem is surprisingly easy to miss if you only listen in stereo with both speakers running.

Hugh

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Technical Editor, Sound On Sound

James, I don't really know what to listen out for - if I provide reference material to play back, if it sounds a bit weird, how will I know its just because I'm listening to a completely different amp / monitor combo, or more specifically, somethinga lot flatter than what I'm used to... I mean, a crackling or harsh, or muffled distortion I could spot like you say; its all new ground to me.

Cheers (again) Hugh, the 'mono' test sounds like a winner... now, anyone selling any monitors in the North East?...

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"There's only 45 degrees between the Hitler and the Zombie" - me, Saturday night, in front of the speakers

Edited by markoos (16/11/04 03:57 PM)

The kind of things you need to worry about with speakers are deformed voice coils which could cause them to rub against the magnet and cause distortion - sine waves are the best test here but failing that, try some music without too much high frequency activity. I would also put my ear up close to each drive unit and make sure that it is putting out the right sort of sound.

Cheers.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Cheers for those suggestions, James... I know this might sound a bit wierd, and it might look even more so, but - would there be any sort of burnt smell inside the cabinet, perhaps from overheating, would that be detectable through any ports?!!

There is one other thing I thought of - I've noticed you can send a super low frequency with a high amplitude that generates a very slow cone excursion. I got my nova to create some bizzare waveform that could be seen and not heard (at least, from the cones, anyway). So maybe then you could hear any scraping / coil sounds - is that worth doing via a minidisc recording of the waveform?

And if I could hear something mechanical, would the monitor be best avoided or should the price be bartered down?


A couple of other theoretical questions, if a cone has distinct damage, will any circuits inside be damaged also? ie, crossovers components, can you overdrive them?

For powered monitors, what state might the amps generally be in if the drivers have gone? Can you damage amplifiers if you drive monitors hard - or is this all unquantifiable, in reality...?

If you know of a good monitor resource, a link would be appreciated.

cheers

markoos

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"There's only 45 degrees between the Hitler and the Zombie" - me, Saturday night, in front of the speakers

Speaker cabinets often smell a little strange if you open them up - probably due to the fumes from the glues used in their construction which, in the case of an infinite baffle speaker, might have been there for a few years. Burning resistors tend to have a distinctive smell but I suspect that you'd immediately hear the problem if you have a burnt out resistor.

The low frequency idea might work but chances are you'll find that low frequency sounds are deliberately filtered out in the active circuitry.

A good active speaker should have protection circuitry to prevent damage from overdriving but I have known some protection circuits to not match the capabilities of the speaker well enough and slightly overdriving them was enough to blow a tweeter over the course of a few hours.

If you find a problem then I'd advise against buying the speakers - there are plenty of decent used speakers around so you shouldn't be short of possible choices.

I'm not sure that I can suggest any single resource for speaker information - usually you'll find different sources for different manufacturers. Do a search on this forum and the old one for more info.

Cheers.

James.

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JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net

Thanks again James; and I have indeed been trawling around for monitor info on the old forum... I'll be keeping an eye on the readers ads as well.

cheers

markoos

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"There's only 45 degrees between the Hitler and the Zombie" - me, Saturday night, in front of the speakers