digital distortion/damaged PA speakers - help!

[eventhelosers]

I play guitar in an 80s pop covers band that doesn't have a keyboard player, hence our use of backing tracks.

Our problem is that the backing tracks seem to be having an adverse effect on our PA system (the horns keep cutting out), which we have been told is down to digital distortion.

Our tracks are downloaded from the internet, mixed in Garageband, converted to Wav file format via Audacity and then played back via a laptop/DIb box through our mixer.

My question to all you knowledgeable folks is, at what point in this process would the audio begin to digitally distort? My own feeling is that they're probably compressed to the point that the quality of the audio is compromised when it is converted to a downloadable file format, but I am interested to find out what other people think.

Thanks in advance for any help/advice you can provide!

[Sporky_McGuffin]

Sounds like bunkum to me. You'd know if there was any igital clipping - it's ear-gougingly unpleasant.

[eventhelosers]

The person at Digital Village that our drummer spoke to said that it was to do with the signal being amplified too much, too early in the chain and that if the signal was too hot coming out of the laptopamabob then it would cause a squaring of the waveform and that SS gear doesn't like that much, hence our current technical issues. The tracks don't actually sound distorted, which led me to thinking that it was something to do with some other sonic shenanigans generated during the mixing process. If it helps, our tracks are downloaded as midi files, apparently.

[ianpdq]

if you are taking the signal from the headphone output try and keep it as low as possible on the laptop that mite solve the problem or try this to convert http://www.koyotesoft.com/audio-soft...converter.html

[ICBM]

If the output doesn't actually sound distorted, it sounds like your speakers (tweeters especially) are just not up to the job.

What are they? What power amp are you using?

The usual rule is that you need more amp power than speaker rating, in order to prevent amp distortion - but this only works up to a point. The reasoning is that with an uncompressed signal (typical of live music), the peaks are always far above the average signal level, so if you hear the peaks distorting and back off slightly to stop it, the average is then much lower, and the speakers are safe. But if they're being fed with a very compressed, near-constant-volume recorded signal, this doesn't apply anywhere near as much and if you then turn the amp up far enough, you will blow the speakers.

If the bass drivers aren't failing, you could always up-rate just the tweeters, or possibly modify the crossovers or any protection circuitry to reduce the power they get slightly.

[colonel65]

Are the tracks MIDI? If so I'd probably keep them that way and play them through a decent sound module. If the tracks are Mp3 theres no point converting them to audio, the loss is already there and you're just wasting disc space.

[ecc83]

There is also a possibility that in all that rats nest of wiring you have produced HF instability and could be putting 30W at 18kHz thru the tweeters.

A 'scope on the speaker line would tell you in a instant as would an old fashioned Avometer but most cheap DVMeters don't go that high.

Laptops are notorious for groundloops and squealy noises.

Always, always had an AC meter hung on 100V speaker feeds!

Dave.

[*Noodles*]

I'd go with dodgy box / speaker not able to cope.

'Digital distortion' can take a driver clean out of an enclosure, so I really doubt unstable tweeters are being affected by square waving.

My experience would tell me that your boxes aren't up to the job of amplifying the backing tracks along with everything else. [my presumption here is that you're not running the laptop at 100% volume from a 3.5mm to a 1/4" into the back of the box. Hopefully you're using a balanced cable from a DI box]

[cacofonix]

Why not try an EQ cut in the high frequencies. Isolate which frequencies are causing the tweeter circuit to cut out (there may be an RCD to protect the diaphragm), and cut that frequency.