Answered KEF Q300 - driver failure (pic included)

D J Fryer

Active Member
Have owned these for a few years (bought second hand on these forums) and very pleased with them. Always used with dust covers on. Recently thought the sound was a bit imbalanced. Removed the dust cover of the left speaker to find this. I am not aware of any physical damage (trying to rule out the kids!) occurring. Has anyone else seen a driver fail like this and does anyone have any experience of KEF repairing such things? No warranty now and second hand in any event.
IMG_2730.JPG
 

D J Fryer

Active Member
I run them with two amps for different purposes - home cinema is a Denon receiver from a few years ago never run loud and for stereo a Rotel 1062 - sometimes loud but never to the point of any hint of distortion. The cone is pretty inactive i.e useless - can hear treble but nothing resembling mids or bass.
 

davidf

Well-known Member
It has received some abuse somewhere along the line - did anyone had a party without you knowing? The last time I saw that it was the fault of their teenage offspring...
 

D J Fryer

Active Member
It has received some abuse somewhere along the line - did anyone had a party without you knowing? The last time I saw that it was the fault of their teenage offspring...

Not that anyone is admitting! No teenagers but do have two unruly dogs so I'm not ruling out that it has taken a fall - just no obvious signs of that being the case such as cabinet damage (and we have hard floors). Covers always on too. It's a mystery. Be interested in whether it's worth a repair or whether I get to spend some money on new things!

EDIT - just realised - these were your old speakers!
 

davidf

Well-known Member
Could be some electrical spike issue or something, but the other mid/bass driver would probably have died as well, and possible some of your electronics. Easiest way to tell is if you have a sniff near the driver - if there's anything resembling a burnt smell, it's been overdriven somehow.
 

Access

Active Member
Doesnt look like anything that could be caused from just playing loud. Just buy a new driver, id guess around £50 ish.
 

Joe Fernand

Distinguished Member
AVForums Sponsor
A quick Google throws up a few folk with the same failure - it seems to be unique to Uni-Q, which is why it looks so unusual!

Talk with KEF - ideally you would replace the matching driver in the other cabinet if this is a stereo system.

Joe
 

davidf

Well-known Member
It just looks a little unusual because of it being an aluminium driver. A paper or other type of cone wouldn't have stayed in that shape when it was forced so far outwards - they'd be misshapen of course, but returned back to something a little more representative of a cone...
 

D J Fryer

Active Member
Not repairable according to KEF service on the phone just now (they've seen the picture) - new speaker needed - no point replacing a single speaker at the cost they are quoting (which is almost as much as a new pair since the discounts kicked in). So time to look for something new! Open to suggestions for something new - using a Rotel RA1062 and a Project turntable (the one with the built in phono stage) on Partington Dreadnought stands.
 

PiperCub

Banned
Kef ls50 used or dealer demo is the obvious upgrade with a decent warranty obviously.
 

D J Fryer

Active Member
Kef ls50 used or dealer demo is the obvious upgrade with a decent warranty obviously.

I saw a set of these sold in the classifieds recently. Would certainly be interested at that second hand price point. Reviews all round seem favourable.
 

FrankSlater

Novice Member
Very similar experience here with brand new KEF q350. Within two or three hours, woofer/mid cone simply blew off the inner tweeter and split in half. Not overdriven as far as I can tell - 50% volume from an A-S501. Looking into it with KEF/supplier to identify possible causes, but looks to me like manufacturing defect.
 

Wavod

Active Member
Doesnt look like anything that could be caused from just playing loud. Just buy a new driver, id guess around £50 ish.
Close, but no cigar!
I bought the speaker from the OP in this thread & paid £140 for a new driver directly from Kef [emoji12]
 

Access

Active Member
Close, but no cigar!
I bought the speaker from the OP in this thread & paid £140 for a new driver directly from Kef [emoji12]
eitjer you were over charged or they have gone up a fair bit in the last couple of years. I used to buy these for repairs
 

adrdbr

Novice Member
Hi folks, I've recently bought a pair of Q350 paired with AV Receiver Denon AVR-X2500H, and with a SVS SB-1000. After a few hours of listening at a normal volume, one of the speakers had its driver blown off(can't attach the photo, unfortunately) and the other one started to 'crack' as well. The retailer from which I bought them said, at a first glance, that I used them 'too loud' which is nonsense, but they will send the speakers to KEF service for a final answer. The receiver is 95W and the speakers can be amplified up to 120W. Any ideas why this happened? I mention that there was nothing wrong with the electricity, power surge etc.
IMG-20190216-WA0003.jpg
 

Joe Fernand

Distinguished Member
AVForums Sponsor
'The receiver is 95W and the speakers can be amplified up to 120W' - the recommended amplifier range is 15 to 120w, the important bit is the Max Output of 110db (measured at 1m).

The drivers may have failed or you could have overdriven them.

Hopefully KEF can identify the problem.

Joe
 

adrdbr

Novice Member
'The receiver is 95W and the speakers can be amplified up to 120W' - the recommended amplifier range is 15 to 120w, the important bit is the Max Output of 110db (measured at 1m).

The drivers may have failed or you could have overdriven them.

Hopefully KEF can identify the problem.

Joe

Thanks for the reply.

Here lies the conundrum:
- How could I have overdriven a pair of120W speakers with a 95W receiver?
 

Joe Fernand

Distinguished Member
AVForums Sponsor
The Max Output of 110db is the important bit - drivers usually fail when you put too much heat (power) through the voice coil.

Your Uni-Q driver is slightly more unique in its construction and catastrophic failure of the driver seems to be how they 'go'.

Watts have always been an inaccurate measurement in the world of Hi-Fi - often hijacked by the marketing folk to indicate higher is better.

Joe
 

adrdbr

Novice Member
Thanks, Joe. Now it makes sense.

My bad because I did not know to ask the retailer about the output of the receiver.
Well, most likely, I'll have to debate this in the store.
 

adrdbr

Novice Member
Came back with the solution from KEF service:

1. They can repair the Q350 set by replacing the damaged drivers;
2. Or allow it to refund, but I need to buy another set from their retailer.

The obvious question is:
- Would KEF Q750 be a sound choice (pun intended), since they are tower speakers, to be matched with Denon AVR-X2500H?

I'm not sure on the answer since on KEF site the difference between Q350 and Q750 is minimal (M.O 110dB vs 111dB for Q750; Sensitivity 87db vs 88dB etc).
The main difference is on the frequency, where Q750 is able to play from 48Hz instead of 63Hz, and obvious, the no. of drivers.
 

alextheg

Active Member
The sensitivity rating refers to how efficient the speakers are . The dB reading is maximum output. Obviously the 750's are much more capable speakers . They're floorstanders for a start and will produce more sound in a given room . Maybe then you won't need to push them so hard to produce pleasing levels of SPL.

The thing to note here is you seem to have pushed your driver's very hard and paid the price for it .
 

dogfonos

Well-known Member
Any ideas why this happened?

What is the size of your listening room?

How far do you typically sit away from the speakers when listening?

Did you use the receiver's bass management/EQ to modify the signal sent to the KEFs? If so, in what way was the signal modified?
 

adrdbr

Novice Member
What is the size of your listening room?

How far do you typically sit away from the speakers when listening?

Did you use the receiver's bass management/EQ to modify the signal sent to the KEFs? If so, in what way was the signal modified?

- The room is 50m²;
- No modifications on the signal sent to the speakers; - When watching the TV I sit at 2-3m.
 

The latest video from AVForums

Maverick UK Premiere IMAX Review + Top Gun, Tom Cruise, Tony Scott and 4K + Movie/TV News
Subscribe to our YouTube channel

Latest News

dCS announces Bartók 2.0 firmware upgrade
  • By Ian Collen
  • Published
Audiovector unveils QR 7 loudspeaker
  • By Ian Collen
  • Published
What's new on UK streaming services for June 2022
  • By Andy Bassett
  • Published
LG UltraGear Gaming Monitors get VESA certification
  • By Ian Collen
  • Published
Sony confirms UK pricing for A90K and A75K Bravia XR 4K OLED TVs
  • By Ian Collen
  • Published

Full fat HDMI teeshirts

Support AVForums with Patreon

Top Bottom