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Linn Sara to EPOS ES14s - An insight

YNWOAN said:
Have made the gaskets now - and very nice they are too :).
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When I replaced the b200s in my Saras, I made up gaskets from that white packing material which compresses very slightly. I was going to use someting more rigid and conventional but read that a possible problem with making the chamber completely airtight is that with changes of temperature the volume of the chamber can alter slightly and put a small pressure +ve or -ve on the B200s. Makes sense so I opted for a material with I thought would leak ever so slightly - not enough to change with the music - but which would over a pronged time allow changes in air pressure inside and outside the chamber to equalise. Seems to have worked OK as they sound fine to me - and now much eaier to remove if ever needed!
 
Yes, I've looked into that phenomena and the logic is justified. However, in this case I think the controlled air leak is likely to be introduced by adding a small hole. In the case of my own speakers, the bass driver roll-surround is partly porous.
 
YNWOAN said:
Yes, I've looked into that phenomena and the logic is justified. However, in this case I think the controlled air leak is likely to be introduced by adding a small hole. In the case of my own speakers, the bass driver roll-surround is partly porous.
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What drivers are you using ? I thought the B200s were pretty well airtight.
 
Yes, this is such an issue it's a wonder that manufacturers of sealed box speakers dion't incorporate Schraeder valves on the back, so you can equalise pressure whenever the little man and the little woman swap places outside the chalet.
 
Joddle said:
What drivers are you using ? I thought the B200s were pretty well airtight.
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Oh sorry, my fault for causing confusion; yes, you are quite right, B200's are airtight. However, my own speakers are Yamaha NS-1000Ms. Which use a doped cloth surround to the bass driver (I managed to completely omit this detail before :)).
 
RustyB said:
Yes, this is such an issue it's a wonder that manufacturers of sealed box speakers dion't incorporate Schraeder valves on the back, so you can equalise pressure whenever the little man and the little woman swap places outside the chalet.
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Yes and I think in the Sara its more important in the Isobaric chamber itself where it would cause a differential force on the two B200s i.e. either being pulled together or pushed apart. There is then the main void behind the rear B200 to consider as well!!
 
What temperature do we think the air behind the back unit gets under heating from the coil? ambient temp and ambient air pressure makes the square root of exactly bugger all difference.

@Rusty, to be honest I'm surprised they haven't implemented some active pressure equalisation system at great expense- maybe called the ekspansion ;-)
 
Infinite baffle speakers are seldom fully airtight, there's almost always some route for air pressure to equalise e.g. via the back-plate, speaker connectors, driver mounting bolts etc. The classic LS3/5A 'box test' where one pushes the B110 in and expect it to slowly return to position proves this - if it really was air-tight it would not behave in this manner! (this is actually explainable as, even with a perfect cabinet seal, there's still an air route via the T27 tweeter cable routing which goes via two holes in the tweeter faceplate!).
 
flatpopely said:
Indeed they are!
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And maybe this could be a problem albeit a small one, nevertheless something perhaps to consider if doing a rebuild or serious mod. I think the main issue is to retain an apparent "airtight chamber" whilst the cones are moving (ie the movment of the cones does not cause air to go in or out) yet allow the pressures to equalise when the unit is not in use (ie let enough air in or out to prevent differential pressure in and out of the box). This would mean allowing the tinyest of air weeps which may be difficult to construct, guage or control - so perhaps Linn just sealed it all up and said thats good enough rather then bother!
 
Mdf is inherently pourous

My big cnc machine has a vacuum bed that will happily suck down an 8x4 sheet through another 8x4 sheet.

Air tightness over a musical transient is not the same as a box that will over a couple of days equalise atmospheric pressure.

So please no more talk of putting pin pricks in roll surrounds or some dickhead will actually do it!
 
And if you are wanting a project there are some Sara cabs with crossovers on fleabay - pretty cheap at the moment - the Xovers must be worth a bit on their own.
 
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