Axiom Home Page Forums General Discussion Technical Questions Driver woes - the investigation

So i'll try to make this concise, but the detail will stretch this out a bit.

After working up to the tests on the Audyssey this week, I was going to do some with and without critical listening. Just happened to be on the main floor and played some music we hadn't heard in awhile which i thought I would like to hear in the media room for the Audyssey test.
Then what do i hear?
Some kind of distortion from the big Tannoys, right channel, bottom driver. Let's say it sounded like a reverberating buzzing with the polypropylene cone and not like the sound of a wire vibrating against a part.
I did take some video/audio of the sound.
Tannoy Speaker driver 1a
Tannoy Speaker driver 1b
Pick out which has the distortion sound.

For reference in the upcoming text, the song played was: La Goutte D'Or by St. Germain (it has a constant bass beat, starts after the first minute of the song, which runs the remainder of the song so very easy to replicate this distortion noise)
https://www.youtube.com/watch?v=QxCI05Vz4LU
When i refer to a second test song, that one was from my standard test list: Calcium by Future Sound of London (same thing, it has a strong bass beat which makes it easy to reproduce the distortion sound)
https://www.youtube.com/watch?v=a4iyPMWOZkY

Here's where i'm going to detail the list of things i did after:

1. check the counterpart/left channel speaker for the same sound to eliminate song as source--> nothing, bass playback was fine, smooth
2. swap the speaker cables to see if the sound followed the source channel to eliminate left vs. right from source song, or source equipment--> it did not, the sound remained with the suspect speaker driver
3. listened to the song on another system, speaker set (Axioms) to further eliminate song as source or equipment--> the distortion was not reproduced, bass sounded fine on the Axioms
4. gently pushed the suspect Tannoy driver down and back to see if i could hear any scraping--> nothing evident that the cone is rubbing against anything or that the voice coil sounds crackly
5. pulled the Tannoy driver, checked ohms--> read 5.4 and the speakers are rated as 6ohm so all seems ok with the voice coil from that perspective
6. swapped the suspect driver with the 'good' driver in the other speaker (to eliminate crossover as any problem)--> no change, the sound remained with the suspect driver

After all this, what is there to conclude except something is going on with this driver? Though it doesn't seem like the obvious things; no clear rubbing of the cone against anything, voice coil has electrical integrity, no apparent rips or tears on the inside, source sound/music and x-over eliminated as faults.
I have a local friend who is a long time stereophile that hopefully can help to figure this out, but in the meantime i decided to bring my old vintage Mission 737 speakers to the main floor to use as a replacement for now.
Here's where things get ridiculous.

I hook up the Missions to the gear that the Tannoys were hooked up to, play the song and the Missions produce a nearly identical/similar buzzy sound and only from one driver (coincidentally it also was on the right channel at the time).
I mean WTF??
I started to second guess myself that the issue had nothing to do with the Tannoys, but then what about the results of the other tests; how do they explain this?

So, i did some of the same tests on the Mission speakers as i did with the Tannoys.

1. check the left channel Mission speaker for the same sound--> nothing, bass was playing fine, distortion still only in the right speaker driver
2. swapped the speaker cables to see if the sound followed the source channel--> it did not, the sound remained with the suspect speaker (coincidentally same result i got with the Tannoys)
3. instead of listening to the song on another system since i already did that with the Axioms, i brought the Missions from the main floor to the media room to play the song down there instead on all different equipment of course (cables, amp...the only thing that was the same was playing the song through Sonos but since the Axioms never played back the sound, and all other test results included, there is NO way it has anything to do with the source material)--> the distortion was reproduced on the suspect Mission speaker driver in the media room system as well
4. gently pushed the suspect Mission driver down and back to see if i could hear any scraping--> nothing
5. to eliminate the possibility that the Axiom speakers don't play back this sound the same way as the other two brands, i hooked up the new office Monitor Audio Golds to the media room system and played the song. No hint of distortion from either bass driver, same result as for the Axioms. I will mention again here that only ONE driver from each of the Tannoys or Mission speakers had this distortion sound while their counterpart driver in the second speaker did not.
6. to further eliminate the song as somehow being the problem, i used my second test song for testing bass--> same result with the Mission speakers suspect driver (by this point i had unhooked the Tannoys so i never tested the 2nd song theory with them but again, with all other tests run, i don't think there is evidence to point to the source song as the problem).

From all that, looking for thoughts.
The only conclusion i have come to is that i have a problem with two woofer drivers; one on the Tannoys, one on the Missions.
Does this make sense?

There may be other things to test, but we're starting to get beyond my knowledge level of what else to look for and why let alone anything i can fix (loose wires, dust cone that isn't fully attached, sure, but broken voice coil or cone misalignment, not so much). I can add that we did find a small red truck inside the suspect driver's tower which apparently my daughter shoved in there probably 10 years ago, but even removing that didn't change anything. It was buried in the batting at the bottom anyway. Is it possible when that truck got pushed in though that it hit and damaged something in the driver that went undetected for all this time?

What happens if you play the Axioms in the media room?

Tannoys (problem driver) - main floor
--only 1 driver makes distortion with 1 song regardless of L vs R channel or different speaker cabinet

Missions (problem driver) - main floor and media room
--1 driver makes distortion with 2 songs regardless of L vs R channel or room/AV gear

Axioms (no problems) - media room

Monitor Audio Golds (no problems) - media room and office


The room, song(s) and source equipment are not the issue. The results do not support that hypothesis.

I've had issues with the voicecoils on drivers even when they haven't separated from the spider. They had almost a dry rubbing sound and I could reproduce the sound at high or low volumes. I could also make the sound just pushing/pulling on the driver.

Listened to your posts and it doesn't sound in the videos to be the same sound I have experienced. I'll try playing a few more times and see if I can pick up on the distortion

The more I listen the more it sounds like voice coil rubbing but that's just my opinion.

Driver1b has the distortion. Very obvious listening on my Android phone. This is very surely the driver. It sounds like the voice coil expanded slightly and is rubbing against the top pole plate.

1B bad.

Tighten fasteners all around and retest.

I should have elaborated. unless the sound is obviously mechanical (in this case no) it is usually vibration caused by certain notes or excursion. Tightening the driver fixes this up.

Fixes tweeters too. I always tighten up speaker screws before I dial things in. The screw gun at Axiom is probably air driven and varies through production. I always get a full turn or more before they are truly tight. Sometimes more.

All manufacturers are likely the same. Even expansion and contraction of MDF can cause slack on the fasteners. Anyway, it works.

#1 Cause of speaker distortion. Amir never seems to mention that....

I swapped the drivers from one cabinet to the other to rule out any crossover issues. During that i would have tightened down the bolts to an acceptable max. It didn't change the sound.
I suspect at this point it is likely a slightly out of alignment voice coil, possibly from gravity sag over time. It is also possible that the coils in both the Missions and Tannoys are ok and for some reason as you mention, a specific frequency, is causing the sound but then if the paired driver in the other cabinet isn't doing this, i would say the suspect drivers are somehow out of spec.

Considering the cost of the Tannoys (aside from the fact that i don't have the workbench, materials, time or practiced skill to undertake a voice coil realignment) i'll be bringing the unit to a local repair shop with a fellow on staff that knows speakers really well. Just hope that there's nothing unrepairable such that i have to go and find some old stock driver which would be a rather difficult hunt i think.

As for the Missions, well, they are circa 1982 and might just be up for the sale block to someone that wants to take the time to sort them out. The cabinets are in rough shape. I haven't used them in 4 or 5 years up until this week, so probably time to move them on.