Did I damage my speakers?

[clemenules]

1. How likely is it I damaged my speaker based on situations below?
2. How do I test if my speakers are working to spec?

Equipment:
Speakers elac dbr62
DAC minidsp 2x4hd
ADC / mic interface Motu M4
Mic SoundID Reference Measurement Microphone
Amp IMG Stageline sta 800d (= 2x Hypex ucd400 = 2 x 400W @ 4ohm)
Decibel meter c weighted
Laptop with REW

Situation 1: accidental but short (1s) full blast signal through speakers.

Situation 2: full range sweeps @ 75db c-weighted @ 3m

Situation 1:
Dac has 2v output unbalanced, amp has 1v input sensitivity unbalanced. Hence, I set the minidsp at max - 6db, thinking this will ensure my amp NOT sending a clipped signal. Before finishing Rew/dac/amp and audio interface to get to 75db at listening position, minidsp is at - 6db but amp and windows are at 100%. Some background app decided to give me a notification, accompanied by a short windows "chime". At full blast. It lasted only 1 or 2 seconds, and I'm not sure if it was my speakers or my ears distorting at the moment, but it did not sound well. Could this have damaged my speakers? One song in particular sounds sometimes wonky in the first few seconds, and sometimes not. I'd like to know how likely it is I broke my speakers and or how to exclude them from the problem discovery.

Situation 2:
After I had completed a bunch of sweeps I watched my speakers while a sweep was running (instead of watching my laptop). No clicking sounds, but the movement of the woofers on the dbr62 was EXTREME at the low end of the sweeps. Sweeps were done at 75db c weighted at 3m. Could this have damaged my dbr62 woofers? Should I refrain from doing full range sweeps with bookshelf speakers?

Thanks for any input!

 

[AdamG]

Can you take some close up pictures of the Tweeters? Woofers are probably fine from a few seconds. Tweeters are another thing. Do you see any visible damage to the tweeters? Do you have REW and a Microphone? If so just run a frequency sweep and capture the results. That should indicate if the drivers are damaged.

Best uninformed guess from a couple seconds at max everything. No damage or possibly fried tweets. Again pictures of the tweets will help us diagnose.

Doing full range sweeps on bookshelves speakers shouldn’t hurt them as long as you don’t crank up the volume. Repeated torture of low frequency test tones will ultimately not improve life expectancy. Test tones have killed more speakers than any music ever has.

 

[DVDdoug]

It would be unlikely for both speakers to be damaged "equally" unless you completely fried your woofers and/or tweeters. So if they both still sound the same and you are not hearing any obvious defects, they are probably OK.

Speaker damage is usually obvious, like a driver not working at all or a rattling voice coil.

Note that speakers are not rated for continuous test tones and tweeters can't handle as much power as the woofer. So be careful when testing! Speakers are rated for momentary program peaks (with much less average power). Checking online I see your speakers are rated for 120 Watts. Assuming they are honestly rated, they should be safe with a 120W amplifier that's not clipping* (or barely-occasionally clipping) with normal program material.

but the movement of the woofers on the dbr62 was EXTREME at the low end of the sweeps.

That's not unusual, especially with ported speakers. At low frequencies (below resonance) there is no loading... There is no air-resistance or air pressure limiting movement. You might be surprised how much movement you get with a 1.5V battery (DC = zero Hz) and that's less than 1W

But it's still getting power and heating the voice coil so it's "not good" to feed energy into a speaker at frequencies it can't reproduce. A similar thing can happen on the high-end... You can fry a tweeter with high frequencies that it can't reproduce and/or that you cannot hear.


* When an amplifier clips it puts-out more power. If the clipping is bad-enough to turn a sine wave into a square wave, that's double the power (if the amplifier can sustain that). And that additional power is harmonics, so more energy into the tweeter. But worse than that, although the peaks are clipped the average keeps going-up and it's mainly the increased average power that damages the speaker.

 

[Salt]

1. and preferred: measure the speaker
2. if not possible: give a signal to the speaker (music, noise) and listen with one ear close to each driver if it works and if there are distorsions (if possible cover the other drivers)
3. Woofers and mid-cones can be slightly moved with pressing 3 fingers concentric to the center. If this give scratches the coil is damaged. Don't do that to tweeters or dome-mids!

 

[MaxwellsEq]

Another coarse check can be to move the speakers next to each other and play mono music, moving your head left and right at driver level listen to both speakers. They should sound identical at any particular height. Although simple, this can show up differences. If you think you hear a difference, physically swap them and listen again, which can cancel out room interactions.

 

[clemenules]

Thanks all for the replies! Due to work/life obligations no time to set up measurements yet. I will definitely follow up once I have time and post findings here.

In the meantime, found a major source for the "wonky" sounds I was hearing: when streaming spotify to my Kodi (LibreElec) setup, intermittently there seems to be a subtle change in pitch. This was driving me absolutely nuts as I was not sure if it was in my head or real because I could not reliably reproduce it. However my girlfriend noticed the same thing, without her being concerned with audio quality in the least or knowing about my concerns in this case - which I consider confirmation. Further investigation led me to some Kodi settings that should help me manage this effect ("sync playback to display" and "Threshold for pitch correction") which have resulted in me being able to introduce pitch "corrections" at will, but not being able to disable this feature (i.e. I still have pitch corrections when listening through spotify connect to the LibreElec's Librespot plugin). I have not found other instances of people having problems with this feature, which made the initial search for the root cause of what I was hearing rather difficult and led me initially to focus on potential damage to my dbr62's.

There is no pitch "correction" when playing from local network files, only when using spotify connect to the LibreElec box.

As, apart from the weird pitch issue, there seems to be no obvious defects in the sound reproduction, my working hypothesis for now will be that no damage has been done to my dbr62's during the REW testing and accidental full blast windows chime playback.

I will test this working hypothesis when I have time and report results here (proper near field mic test for both speakers).

Thanks again for everybody's responses.

 

[clemenules]

Had some time to do some quick & dirty measurements for verification. Both speakers measured at their normal locations, nothing fancy schmancy, at approx 30 cm distance each, 1/48th octave smoothing. decibel readings not calibrated as I was just interested in the shape of the curve. Nothing obviously wrong, as we were expecting.

I'm accepting my working hypothesis that my speakers have not been damaged.

Thanks again all for taking time to post in this thread previously.