Distortion in one loudspeaker only.

[Purité Audio]

Performed a quick measurement today on a neighbours system, the speakers were ‘Lumley ’ something or others, ribbon tweeter two 2” domes two 5” mids and a 10“ woofer, measurements were not spectacular, but what was striking was that one speaker had hugely worse distortion through the bass than the other, placement/background was more or less symmetrical , what might be causing that bass distortion apart from a faulty driver?
Thanks,
Keith

 

[Ron Texas]

Try switching speakers left to right and right to left to eliminate everything upstream.

 

[Purité Audio]

Really large/heavy loudspeakers but that would be a start, do you remember Lumley speakers, weren’t they John Jeffries own brand?
Keith

 

[Pluto]

Really large/heavy loudspeakers

Then swap the cables at the amplifier end, Keith

 

[Purité Audio]

Even that wasn’t possible as the amps were huge ‘Lumley’ reference monoblocs, each a two man lift and the rears inaccessible .
Keith

 

[pma]

So try different cables . And clean all the contacts.
Seriously, I would suspect amplifiers output relay first.

 

[Blumlein 88]

If you only did one measurement, and it was in the bass only it could have been noise contamination. Did you re-measure getting the same result?
Also if you did this with REW a graph of each and maybe even the MDAT files attached might give us more information to work with.

 

[Purité Audio]

When I get back I wil pose the MDAT.
The room wasn’t any noisier for either measurement , the speakers I believe are not highly regarded,

 

[Blumlein 88]

When I get back I wil pose the MDAT.
The room wasn’t any noisier for either measurement , the speakers I believe are not highly regarded,
View attachment 50190

In low frequencies say 200 hz and especially 100 hz and below noise you might not notice can contaminate the distortion readings. Like a garbage truck the next block over. I literally have had such a truck cause what you are describing here. Re-did the measurement and the issue was gone. HVAC units cutting on or off next door can do a little of this. I don't know if you are comparing 1% on one channel vs 3% on the other or a larger difference.

 

[Soniclife]

Even that wasn’t possible as the amps were huge ‘Lumley’ reference monoblocs, each a two man lift and the rears inaccessible .
Keith

Pop back round with a tiny class d amp and cables, worth it for the amusement value alone from the size mismatch.

 

[suttondesign]

Performed a quick measurement today on a neighbours system, the speakers were ‘Lumley ’ something or others, ribbon tweeter two 2” domes two 5” mids and a 10“ woofer, measurements were not spectacular, but what was striking was that one speaker had hugely worse distortion through the bass than the other, placement/background was more or less symmetrical , what might be causing that bass distortion apart from a faulty driver?
Thanks,
Keith

It's your left ear, Keith. I'd get that looked into, if I were you.

 

[Pluto]

Even that wasn’t possible as the amps were huge

Sorry for being so sarcastic... the lowest form of wit, I know...

 

[Berwhale]

Even that wasn’t possible as the amps were huge ‘Lumley’ reference monoblocs, each a two man lift and the rears inaccessible .
Keith

Is this one of them 'locked room' puzzles?

 

[Purité Audio]

It was the rarest of all things a Hi-Fi dealer ( trying) to do something for nothing.
I have read that Lumley used really poor quality drivers, and if there was space on the baffle then stick in another driver to fill it, whether that is true I can’t say these are pre-interweb .
Keith

 

[sergeauckland]

Seriously, If you can't get to the back of the power amps, let's assume that the power amps are OK, as I can't think of a mechanism by which an amp would distort heavily at LF and not elsewhere.

So, you must have access to the preamp or source to make the measurement. So, swap L and R and make sure it's the 'speakers. If it is, then likely to be the driver. Try listening to just that one.

S

 

[Berwhale]

There's an example of the same speakers here: https://www.whybuynew.co.uk/consumer-hifi/hifi-speakers/lumley-monitor-ref-ii.htm

The description says 'a few minor marks' but they look like they've been dropped on their corners several times!

Also, what do the fly lead and banana connections do on the back? Did you notice if they were set the same on both speakers?

 

[Pluto]

Seriously though, one thing worth checking with older speakers is that the nuts clamping the drive units to the baffle are as tight as they ought to be - a torque wrench is your friend here. If a LF unit is not securely clamped it will 'rattle' to some extent and that could be the source of the distortion.

The other thing to check is that the unit hasn't gone slightly eccentric. If it has, this might be treatable by inverting the drive unit, with gravity 'encouraging' the sag in the opposite direction but usually, if sag has occurred, it's time to get the drive unit off to someone who could refurbish the thing. In such a case, it might be useful to get them both done.

 

[daftcombo]

Probably that the "bad" speaker has the driver badly placed in the box, the coil rattling or something like that. Can you open it and check?

 

[Prana Ferox]

Is the problem audible enough that you can play with stuff and tell it went away, or do you have to remeasure to check?

If inaudible, are the rest of the measurements good enough to make a snark hunt worthwhile?

 

[amirm]

If you turn it up and the sound starts to cut off or get static, then it is the amplifier. Otherwise it is probably the driver.