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LS3/5a cabinet damping

4

40imp

Active Member
I'm building up a flat pack cabinet kit from Falcon to use for some experiments. They included damping
panels for the top,bottom and sides but none for the back. This is deliberate and made me think
why this was done as its a larger panel than the sides and back. Does anyone know ?
 
The sides,top and back are cut from 12mm birch ply. The supplied damping pads are 4mm dedshete. I also have
real Falcon LS3/5a's and as far as I can see they are same ie no damping on the rear panel. All the cabinet top,sides
and back have acoustic foam applied to them 16mm top,back and sides and 25mm on the rear panel but this shouldnt
provide much panel damping.

As its deliberate I'm wondering whether it has some sort of effect on the bass response. The LS3/5a is renowned for
having an engineered bass "hump" and maybe the undamped rear panel's resonance add's to this in some way.

Anyway I'm going to try damping this to see what happens but it would be nice to know why it was omitted in the first place.
 
I think Ive found the answer and I should have read the BBC research paper on the LS3/5a more closely. It
seems that they didnt measure any significant panel resonances from the speakers panels on account of
their small size. However some damping was applied to the sides, top and bottom to tame driver induced
resonances. There was no need to do the same for the rear.

So I'll go ahead with applying damping to the rear panel on my kit build and see what happens as I dont think
I'll do any harm.
 
I find it intriguing that some LS3/5a's used MDF rather than Birch Ply cabinets (I think Spendor did this in their later models) - you would have thought this has a different resonance.
 
Its probable that because of their size panels in mdf dont have much resonance either. Anyway I
intend to measure the panel resonances if I can find a suitable accelerometer though the one
in my mobile phone might work well enough.
 
One of Rogers cabinet suppliers told me that MDF was so much easier to work with, They made all of the Studio series but not LS3/5a.
 
I thought it was the Kef versions that were built with mdf, pretty certain the 11 ohm Spendors i owned were birch ply.
I presume any that were built using mdf would have been after the BBC had stopped using them for monitoring purposes themselves so perhaps the licence conditions were not being applied as strictly.

TS
 
sktn77a said:
Reliable citation for this (other than the clown on YouTube who just raps the cabinet with his knuckles)?
Click to expand...
How about from Andy Whittle then? MD of Rogers when they were making them in the 90's. He confirmed that when we were both heavily involved with these.
 
TonyScarlett said:
I thought it was the Kef versions that were built with mdf, pretty certain the 11 ohm Spendors i owned were birch ply.
I presume any that were built using mdf would have been after the BBC had stopped using them for monitoring purposes themselves so perhaps the licence conditions were not being applied as strictly.

TS
Click to expand...
Some Spendor ‘3/5as were made with MDF baffles and ply cabinets, but I don’t know when
in their production cycle that happened.
 
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