Used Quadral Fortun X - distortion across the frequency range

[perkyagnostic]

Hi everyone,

I just picked up a pair of used Quadral Fortun X. I'm a huge fan of Quadral speakers from this era (late 90s, early 2000s) and when I saw them for 70€ I had to pick them up.
However, one of the speakers produces distortion across the frequency range. Since I listen to a lot of rock and metal, where distortion is part of the game, I didn't notice it at first. But in quieter parts and especially with notification sounds from Windows it's really apparent.
To confirm I played a sine sweep from 20Hz to 20kHz and yep, the distortion is pretty much the same across the whole frequency spectrum.
Which is really odd to me, if they got overloaded at some point I would expect the tweeter to go first, or at least to hear increased distortion at specific frequency ranges..
Also, I always thought that a defective passive crossover could only lead to linear distortion, not non-linear distortion - am I wrong?

Does anyone have any ideas what might be causing this? Is it possible that all 3 chassis are blown in a similar way? Could it still be the crossover?

Any help is much appreciated

EDIT: I might need to add that I tested it with two different amplifiers (Luxman LV-101 and Pioneer VSX-S510) and different audio sources (digital/analog).

 

[levimax]

What is the rest of your chain? Could it be digital clipping or an analog input over load up stream? How do know you are hearing distortion? Speaker distortion always varies by frequency so not sure it is your speakers.

 

[perkyagnostic]

What is the rest of your chain?

My edit came too late apparently, I tested it with two different amplifiers (Luxman LV-101 and Pioneer VSX-S510) and different audio sources (Toslink from my PC into the Pioneer and TRS/Cinch into the Luxman from a Fiio X3III set to Line-Output). Both chains sound absolutely fine with my other speakers.

How do know you are hearing distortion?

Because when I play pure sine waves at various frequencies and they don't sound like pure sine waves and instead have bunch of overtones it's fair to say I'm hearing distortion

 

[Sokel]

I would open it and check all wiring/soldering.
It's odd that distortion is all over the spectrum.

 

[Sokel]

You can also roughly compare it with the good one if you have a DMM, just put it at the resistance mode, disconnect everything, first measure the good one and then the other.
They should be identical ideally or pretty close.

If they're not, you know you have a problem.

 

[perkyagnostic]

I would open it and check all wiring/soldering.

I will totally do that once I reached an agreement with the seller (I don't want him to accuse me of breaking them myself by fiddling with them).

You can also roughly compare it with the good one if you have a DMM, just put it at the resistance mode, disconnect everything, first measure the good one and then the other.

I just tried that, measured right at the speaker terminals both show a reading of about 6 Ohm

 

[levimax]

My edit came too late apparently, I tested it with two different amplifiers (Luxman LV-101 and Pioneer VSX-S510) and different audio sources (Toslink from my PC into the Pioneer and TRS/Cinch into the Luxman from a Fiio X3III set to Line-Output). Both chains sound absolutely fine with my other speakers.

Because when I play pure sine waves at various frequencies and they don't sound like pure sine waves and instead have bunch of overtones it's fair to say I'm hearing distortion

OK sounds like a speaker problem then but an unusual one. Let us know how it turns out.

 

[perkyagnostic]

The seller offered to take them back for a full refund. I'm conflicted tho, I really like the speakers and would like to keep them, but if the chassis are blown I can't really fix them

 

[levimax]

The seller offered to take them back for a full refund. I'm conflicted tho, I really like the speakers and would like to keep them, but if the chassis are blown I can't really fix them

You probably checked, but just in case, did you make sure all the driver mounting screws are tight?

 

[perkyagnostic]

Yes, all tight :/ To me it doesn't really sound like mechanical distortion (especially because it's most apparent at lower volume), it somehow sounds like an opamp that's about to die or something like that, really weird.

EDIT: Nevermind, I found the culprit.. idk why I haven't tried this earlier, but I gently pushed in the mid range driver and can clearly hear it rubbing, it's shot I think even with a full range sine sweep it get's excited just enough to always produce audible distortion so that threw me off

 

[perkyagnostic]

Well, that explains the rubbing I guess..
Anyway, thank you both for your suggestions (and sorry for misjudging the situation)!