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Hey guys,
I've got an HK AVR-25ii & Paradigm mini-monitors for my dorm room setup and I recently downloaded a speaker design utility that included a sine wave generator. Now, I'm sure you can see where this is going. I was using the generator to determine the in room response of my minimonitors (they fall/[fell :-)] off between 40 and 45 hz - not to shabby) and (this is the kicker) max output. At 47hz with the volume at not quite 12:00 (not all that terribly loud since the volume knob has to be turned up significantly more using the computer than the CDP - line out voltage differences?) my roomate yelled at me something smelled funny (I was walking down the hall at the time marvelling at the interference phenomenon all the way down the hall... loud...quiet...loud...quiet...etc.) The driver was within excursion limits. I came in and quickly turned it down then stopped the sine generator. I stuck my nose to the reciever's vents and it didn't smell like it was coming from there. I touched the dustcap on the woofer cone and it seemed a hair warmer than it should (I imagine this generates a lot of heat). Now, my question for those of you who understand more of this than me is, what did I do? Crossover? Drivers? Melt some plastic/adhesive? Amp? I once blew up a pretty big cap in my high school physics class and it smells vaguely similar, but that was a long time ago. I haven't had the courage to listen to the speakers yet, I'm letting everything settle down for a while (what's a good time span?). Thanks for any and all help. Who knows, I may be upgrading sooner than thought :-)
Mark
Play them and find out. Usually, it would be the speaker voice coil that would go. Within a few minutes they would have cooled off so waiting won't change anything.
Compare r/l response with the balance control and with some good bassy music. It you caught it in time, it may be ok.
BTW: That's partly why test CDs use wobble tones I believe.
Well, I'm back from my 1:00 and just fired 'em up. Balance test checked out fine, played some music on them as well as some *much* quiter waves... 50,70,100,200hz, l/r vol at all freq was the same. Music sounds the same (I think - I'm so paranoid I'm listening for broken stuff, I'm going to let the psychological trauma wear off and do some more serious listening tests).
Question is, what would smell like that? It was sort of like burnt plastic but not as offensive. Would the voice coil do that? I've never blown anything before so this is all new to me :-) The amp seems to be working fine.
BTW, what is a wobble tone? Does it vary between two freq or an entire freq range? How does it improve voice coil heat dissipation? I am planning on building/buying a sub as a summer project and I'd love to know.
Thank you VERY much... I think I caught it in time. Darn, I wanted to upgrade too :-)
Mark
I just got done doing frequency response tests on my new Maggie 2.5's this weekend and did quite a bit of reading in the Stereophile Test CD2 booklet...
"[The warble] is fast enough that the effect of low-frequency room resonances on the perceived level will be minimized."
I've read that the "pure" digital tone from a PC can kill your system, so for God's sake BE CAREFUL. If I were you I'd put away my propellor (yes, I'm a computer nut too, but hey!) and spring for the SPhile Test CD2. I found it at Tower Records for like 15 bucks and it includes some music tracks that you know are recorded in a pristine manner.
Channel Identification
Channel Phasing
Acoustic Drum Solo
Acoustic Guitar Solo
5 Music Tracks
Mapping the soundstage
4 more music tracks
Pink noise at -20dBFS L+R
Bass Warble tone 200Hz to 20Hz
Midrange Warble 250Hz to 2kHz
Treble Warble 2.5kHz to 20kHz
MATT test
6 Jitter & distortion tracks
A bunch of test tracks that will damage loudspeakers if played too loudly
A total of 31 tracks for 15 bucks. I use the warbles to take measurements with my Rat Shack SPL Meter ($30 at a RS near you!). I then put my propellor BACK on & dump the data into Excel (making sure to compensate for the dips on my RS SPL meter) and graph my room response. Just about made my weekend. Girlfriend thinks I'm NUTS.
Good luck.
MDW
Great! Sorry, I don't know what would cause the smell. Jon Risch likely know.
Wobble tones go up and down around a center freq. It's easier on the driver than a pure tone that could cause sress as it's more like music. The Stereophile Test CD 2 has some decent ones on it or there are other sources. The test CDs also change tones every 10-15 seconds so you don't get stuck on on freq.
But, hey, don't let your good fortune stop you from upgrading ;)
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