Was looking at some info today on the KEF B110, and the KEF blurb says it should be front mounted on the baffle, recessed so the chassis is flush with the front of the baffle. Yet on perhaps its most famous application, the LS 3/5a, it's mounted to the back of the baffle.
The LS 3/5A is not really an example of how the B110 had been intended to be used.
John
That's how I did mine. Very fiddly making the recess around the hole.
Bill
KEF didn't design the LS3/5a, they (and others) made it under licence.
Related but not relevant, I was looking up some replacements for the B110, and came across the Monacor 135/AD. It and many others significantly cheaper than elsewhere at:
Of course. It is a BBC design. I just wondered why they'd chosen to not mount it as designed.
Yes - it was primarily designed as a mid range unit. But that would involve a narrower frequency range than the BBC used it for? So any effects due to the mounting would still be present?
You need a router and guide small enough to do a circle that size. and make the recess before the main hole. The 'odd' bits for the mounting holes would need to be routed freehand.
Is this to stop edge effects where the sound bounces off the edge of the baffle? Brian
Funnily enough a friend around that era bought soem Philips speakers and the mid range unit in those was recessed into the baffle as well. I'd not really considered this aspect of speaker design before. Brian
Which kind of begs the question if they had altered its mounting,would anyone have noticed the difference? Brian
no, not really.
Origi8nally you cut a circular or oval hole and mounted speakers behind that, then when routing became more normal, it was conventional to rout a recess for the speaker and front mount it. Front mounting also made boxes easer too make - you didnt need a detachable back to mount the speakers, just a detachable cloth baffle, or later on, when it became fashionable to expose the speakers, nothing at all.
Like most things hi fi, there is more bullshit talked about this than anything else.
Could you make a composite baffle? One thick panel and a thinner one to make the recess?
I'm not sure what a mid-range unit covers, but at 10kHz you have a wavelength of 3.3cm. I would presume any step more than a 1/4 of this will cause some spatial changes.
Oh this was donks ago and I wouldn't have recognised a router if one had hit me in the gob. In fact I doubt if routers were invented then, after all I've never seen a picture of Joseph or Jesus using one. There again I understand the mains is pretty unreliable in the Middle East.
Bill
Ha! I've been and had a look and that's what I ended up doing!
They've served me well those speakers. Still sound great.
Bill
Yes it made it much easier to replace the upper and lower register tweeters and the crossover after my teenage daughter's party.
Bill
FWIW I have Cambridge Audio R50s with B110 mid-range units, and they're front-mounted.
Very roughly 300 - 3000 Hz. 10 KHz is HF.
There's a fairly detailed BBC RD report describing the design of the LS3/5A:
(c) Units
The low-frequency unit is a KEF type B110 unit specially selected to BBC specification; the nominal impedance is 8 ohms and the free-air resonance frequency is 35 Hz (with a statistical spread having 95% confidence limits at 33 and 40 Hz). [...]
This does tend to suggest that the mounting of the drive units has been carefully considered, and probably empirically optimised.
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