Kef 105/3 Reference Speakers - Bass Distortion

[Boyse6748]

Forgot to mention, no problems with clipping or power. I Drive these Speakers with a McIntosh MA 2275., more available power than a formula one GP Motor ��

[Boyse6748]

Hi Jez,

Torsion bars are very tight and so are the plastic port inserts. I can only describe the bass a being extremely low or virtually non existented, which omits a sort of fart occasionally (sorry didn't mean to rude) but it's the only way to explain.

Regards

Peter

[walpurgis]

If, as you say the cone surrounds have been replaced, could it be that a cone is slightly misaligned and allowing the voice coil and former to bind within the magnet gap?

Actually, I don't remember these speakers having foam cone surrounds, but perhaps I'm wrong.

[Reffc]

By all means drop them over Peter and I'll take a look for you. I can run a full impedance V's frequency test for each unit for you. Could be something as simple as a dodgy solder joint.

[Arkless Electronics]

It could indeed be something as simple as a dry joint...

The front baffles are indeed held on only by the hex bolts but the gasket may be "gluing" it down and a bit of leverage may be required...
There are two crossover boards per speaker but you probably already know that.

As an aside, the bass system is two infinite baffle enclosures (one at the top and one at the bottom) driving a central cavity. This has a very wide (5" or so) port and the idea is that a "plug" of compressed air forms in the port and this acts as the actual "driver".. IIRC from a long while ago when I read up on KEF's coupled cavity bass loading technique. I once spoke on the phone to a KEF design engineer who told me that they stopped using the system partially due to expense but mainly, bizarrely, because they had complaints from customers that "my mates aren't impressed enough at the bass drivers 'cos they can't see them as they're inside"!

The two 8" bass units per side (equivalent in cone area to a single 12" driver) have foam surrounds whilst the mid drivers don't...

They have KEF's conjugate load matching technique (the last model to have it AFAIK and due to cost, again according to the KEF engineer I spoke to) which theoretically makes them a perfect resistive load, 4 Ohm in the case of the 105.3.

I have often seen remarks along the lines of "they take a lot of current and need a meaty amp to drive them"... in my experience this is total rot!
They are 93dB/W efficient IIRC and I can personally attest to the fact that even my Leak Stereo 20 drives them really well and to amazing volumes for a 10WPC amp... The lack of any "awkwardness" to the load, due to the conjugate load matching technique, no doubt helps here.

[karma67]

I am reasonably near and live in Melksham Wiltshire

small world! i was there a few weeks ago fitting a new turnstile building at the local football club

[Boyse6748]

Hi Jez,

Many thanks for that information. I did removed the Hex Bolts but didn't use any exsisve force to detach the Pod if fear of damage, that I might live to regret.��

Reffc ( Paul) has offered to sort this issue out and the speaker will be with him on Monday Week. Nedless to say, I am delighted .

Many thanks to you good self and all the members for there valued comments.

Regards

Peter

[Wilbur]

Mine need re-foaming....If only I was brave enough!!

[Light Dependant Resistor]

Mine need re-foaming....If only I was brave enough!!

Why not use rubber surrounds ? which last a lot longer.

[Reffc]

Why not use rubber surrounds ? which last a lot longer.

Not usually recommended because it will change compliance, mechanical Qms and therefore free air resonance and hence tuning. Whilst this may not be much of an issue in some designs, it will be in others, especially at crossover where natural slopes from smooth roll-off transition are often used for woofers (ie it will shift crossover point and create phase inaccuracy problems).