How easy is it to Damage a speaker during Distortion Testing?

[March Audio]

Yes if it's active with low frequency filtering then that should avoid the issue of excessive excursion.

 

[daftcombo]

Was it obvious you damaged it? How did you diagnose it?

Yes it was obvious. The sound was distorted and weird at any volume afterwards. We had only one speaker so couldn't compare but it was obvious.

 

[pma]

I did hear a very brief disturbing crackle during a couple of the parts of the frequency sweep

Yes this is the way how to find speaker damage. The frequency response might remain almost "normal", however the speaker damage reflects in audible "cracks" and subharmonics. This is the way how I test tweeters. I record a slow sweep and then analyze the file. You may find audible subharmonic tones and also see it in the spectrum.

Subharmonic tones indicating tweeter damage.

 

[tuga]

I don’t know if this has been suggested before but have you tried remeasuring your speakers?

 

[Robbo99999]

I've only recently got back from work, so don't have any desire/time to do in depth measurements tonight, but I will tomorrow I think....however I listened to a couple of my favourite tracks that I use for analyzing EQ tweaks (so I know them very well) - from what I remember it feels like the tweeter is missing some overall energy because the bass sounds more predominant, and there could be some holes in the frequency response of the tweeter judging by my impression that there are some sound effects of the tracks lessened in presence along with my impressions yesterday that there is an overall lack of clarity. For instance snare drums don't quite have the sharp attack that I remember. Hmm......just to back up my previous listening impressions, but I'll do some testing tomorrow, and I think I should check out the frequency response as well as the distortion, because the differences I'm pointing to seem indicative of a change of balance within the speakers as well as potential holes in the frequency response. I've read all of your posts and will probably reply tomorrow with any testing I've done. I haven't ruled this out as a "psychological placebo" yet, I'm aware of how strong those things can be (because I was worried I was damaging my speakers during that loud distortion testing a number of days ago, so that feeling has probably stayed with me)....so I'm gonna see if I can rely on some measurements tomorrow (will probably do the listening test of the sweep too to see if I can hear any anomalies at certain points).

 

[Robbo99999]

Wow, this is weird. Decided just now to clean the dust off my speakers gently with a soft microfibre cloth, turned my speakers off at the back of each speaker while I was doing it.....cleaned dust off woofer and tweeter & tweeterwave guide, and also out of the port at back of speaker....I mean not shedloads of dust, but a little.....turned speakers back on and started listening to a TV programme on them and they sounded different/clearer.....immediately I ran two of those tracks I know so well and it sounds back to normal with correct presence & balance along with clarity & imaging....if I'm being critical I got the impression the right speaker wasn't quite back to the same normality as the left speaker, but I think there's quite a clear difference in both. It also sounds louder overall, at the same volume settings.

What do you think's going on here? Do you think there can be a bug in these active speakers that requires power cycling...perhaps the bug was tripped by the high SPL distortion testing I was doing? Perhaps it's build up of static in the system that can be dissipated by extended power off? My speakers were off for probably at least 5mins, maybe 10mins. (Maybe I should try unplugging the right speaker for a longer time to reset it as I felt it wasn't quite back to full normality). (I'll still do the measurements tomorrow). (I know there's a bug with these speakers that sometimes they don't go into standby when not being used....if that can be related or add weight to extended power off bringing my speakers back to normal and removing their "bugged" state)

 

[617]

The 308P should be harder to damage than with a 94dB/0.33m sweep. After all, that is only 84.6dB/1m, which is nowhere the speaker's max output.

How did you determine that the SPL was 94dB? Could it have in fact been much louder?

Having said that, I would hope (and expect) that an active speaker with inbuilt limiters and a high-pass filter to protect the woofer from excessive excursion would not be easily damaged, even if your SPL reading was off by 10 or more dB.

If I were you, I would remeasure each speaker in the mid-field under the same conditions. If the two speakers measure similarly, neither is damaged (or both are damaged in the same way, but that would be very improbable).

I think this is correct. Most monitors including these JBLs have limiters, making damage from overexcursion unlikely. Do a gated frequency response sweep on each and see if they match. If they do, you should be fine.

 

[andreasmaaan]

I think this is correct. Most monitors including these JBLs have limiters, making damage from overexcursion unlikely. Do a gated frequency response sweep on each and see if they match. If they do, you should be fine.

Yep. And a distortion sweep would be good as a diagnostic tool. Damage may not show up on the FR, but it will show up as distortion.

 

[617]

Yep. And a distortion sweep would be good as a diagnostic tool. Damage may not show up on the FR, but it will show up as distortion.

Do we really want him doing distortion tests again??

 

[Robbo99999]

P.S. I got an update, I think it could have gotten missed as someone posted at the same time as I posted......this one:
https://www.audiosciencereview.com/...r-during-distortion-testing.18543/post-607238

 

[andreasmaaan]

Do we really want him doing distortion tests again??

Haha, fair point. If he wants to rule out damage, though, he might have to.

@Robbo99999 I'd say do the FR sweeps first obvs. If nothing shows up there, do further distortion sweeps at a low SPL. Damage, if present, should show up at low drive levels.

 

[andreasmaaan]

P.S. I got an update, I think it could have gotten missed as someone posted at the same time as I posted......this one:
https://www.audiosciencereview.com/...r-during-distortion-testing.18543/post-607238

You're right, I had missed that. Interesting...

 

[Robbo99999]

I have another theory in addition to my observation earlier which was at this post (https://www.audiosciencereview.com/...g-distortion-testing.18543/page-2#post-607238). Just now I flipped up the volume on the back of the speakers by one notch (there's 20 notches, I flipped it up one not to notch #7 or 4.5 as labelled on the back of the speaker)....and the sound gained even more clarity, balance, and even better imaging....beyond the small increase in volume (I may have been running this setting historically). I think the volume pots on these speakers or something associated with the volume control is a bit dodgy on these speakers......at my post I linked in this post I did power cycling which seemed to clarify the sound, but I also twiddled the volume pots back & forth whilst I did that (albeit resting on the same notch).....so another theory could be that the volume pots are a bit dodgy somehow - I'm gonna do some distortion testing tomorrow with different volume pot positions for the same SPL and see if my theory is correct. For some reason I think notch #7 or 4.5 as labelled on the back of the speaker is the golden position for clean sound.....I have some vague recollections that I noticed when I first had these speakers that I had a notion that a certain position sounded better, but didn't pay it much attention after leaving it in the best position. An additional observation re the volume pot for the right speaker, it's quite stiff from half volume to full volume and a little gritty in it's movement over part of that range....if that can come into play at all......left speaker is fine from that point of view. I have a fairly strong intuition that I'm gonna be finding a correlation between volume pot position and distortion (maybe even frequency response)....independent of SPL measured.

 

[Robbo99999]

Ok, I'm now sure I haven't damaged my speakers during the distortion testing, it's definitely something to do with poor sound in relation to position of the volume knobs on the back of speakers. I did a quick listening session this morning with speakers at the 4.5 volume mark and sound is clear as crystal with full dynamics & imaging, turning it down lower than this removes those positive aspects, more than placebo can account for I'm sure.....I can reduce volume level on my DAC and it will still sound good as long as speakers on 4.5 volume mark on back of speakers.

I've only got one day off this week, so not gonna futz around with measuring my speakers for distortion to figure out what's really going on here with the change in volume dial position of the back of my JBL 308p speakers, but I've got a week off after Christmas in a couple of weeks so I'll dedicate a little of that time to get to the bottom of this & I'll update this thread with my testing. I'm sure there's something slightly funky going on with the volume adjustment on the back of these speakers, and I'm 100% sure now I've not damaged my speakers during the distortion testing. Will update with my testing in a couple of weeks. Thanks for your inputs so far.

 

[ernestcarl]

Ok, I'm now sure I haven't damaged my speakers during the distortion testing, it's definitely something to do with poor sound in relation to position of the volume knobs on the back of speakers. I did a quick listening session this morning with speakers at the 4.5 volume mark and sound is clear as crystal with full dynamics & imaging, turning it down lower than this removes those positive aspects, more than placebo can account for I'm sure.....I can reduce volume level on my DAC and it will still sound good as long as speakers on 4.5 volume mark on back of speakers.

I've only got one day off this week, so not gonna futz around with measuring my speakers for distortion to figure out what's really going on here with the change in volume dial position of the back of my JBL 308p speakers, but I've got a week off after Christmas in a couple of weeks so I'll dedicate a little of that time to get to the bottom of this & I'll update this thread with my testing. I'm sure there's something slightly funky going on with the volume adjustment on the back of these speakers, and I'm 100% sure now I've not damaged my speakers during the distortion testing. Will update with my testing in a couple of weeks. Thanks for your inputs so far.

Those cheap switches are finicky as hell. I have problems with LSR305 volume knob switches where turning the knob will not change the volume. It takes about three steps before the volume jumps up to where it should be. What I have done is set these to max and adjust the vol. level calibration via software instead.

 

[Robbo99999]

Those cheap switches are finicky as hell. I have problems with LSR305 volume knob switches where turning the knob will not change the volume. It takes about three steps before the volume jumps up to where it should be. What I have done is set these to max and adjust the vol. level calibration via software instead.

Wow, really, that's not good. I'll still do my testing I explained in my last post, but it's probably better after that if I just set it & forget it....excessive volume knob twiddling might be too much for the dodgy volume controls to handle!

 

[dasdoing]

I have also performed long sweeps at 105-110dB at a distance of 1m to my Sceptre S8s many times by now — besides playing pink noise measuring peaks up to 115dB (per speaker).

wow man. I always shit my pants when going anything above listening level lol
on the other hand Amir takes hundreds of meassurement at high volume, right?
only thing that still would scare me is that it might end the life of an old driver/tweeter?

 

[ernestcarl]

wow man. I always shit my pants when going anything above listening level lol
on the other hand Amir takes hundreds of meassurement at high volume, right?
only thing that still would scare me is that it might end the life of an old driver/tweeter?

Heh! I really meant very short dB transient peaks recorded, not at all sustained or continuous. And the limiters have saved the speakers from blowing more times than I recall. The limiters will not allow anything sustained beyond a 100+ dB or so. Doesn’t matter if you up the voltage. Dave Gunness knew the 1-inch compression HF driver used here was way too small and would not play as loud as his real PA speakers with giant neodymium magnets and voice coils.

 

[dasdoing]

And the limiters have saved the speakers from blowing more times than I recall. The limiters will not allow anything sustained beyond a 100+ dB or so. Doesn’t matter if you up the voltage.

than I wonder why users told me in the other topic that you can damage active subwoofers by playing them too loud

Dave Gunness

didn't knew this guy. now I want to see a Fulcrum speaker meassured at ASR

 

[ernestcarl]

than I wonder why users told me in the other topic that you can damage active subwoofers by playing them too loud

From what I understand, most active subs don't have limiters preprogrammed/built-in. This has to be manually added in the chain. There are some that have it like the small KEF KC62... The expensive and impressive Devialet Phantoms active speakers also come into mind. I used one for my sub via miniDSP back when I liked applying a lot of boost, but there is a loss in sound quality as peaks will get cut short too early if you want to "increase protection". Also, I wasn't able to get it to behave as intelligently as I would have preferred. What the other folks said about not using a sealed sub outdoors is very sensible. If you had one or two Kali WS12s available to use... hmmmn. That could've worked.