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Replacement of existing internal speaker foam

 
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henryc
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Joined: 01 May 2006
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Location: Gloucestershire

PostPosted: Thu Jun 01, 2006 3:11 pm    Post subject: Replacement of existing internal speaker foam Reply with quote

Hi
In my constant quest to tweak and improve all I was wondering whether replacing the internal dampening materials is worthwhile?
My LS5/1AC's have a circa 1.75 inch thick yellow foam on top of a 0.5 inch bitumen impregnated material layer which is bonded to the inside of the cabinet. The foam is not stuck to this layer but firmly shaped to fit over 5 sides, the baffle has no foam or bitumen material applied to it.
(See pictures on web link : http://www.hifiloudspeakers.info/PersonalKefTreasures/HenryCoelho/Gallery/index.htm)
Please have a look and give me your opinion if it's a good idea to replace the yellow coloured internal speaker foam with something else which has a better performance?
Will it really make any difference?
Any views?
All the best
Henry
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ColinR
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Location: Staffordshire

PostPosted: Thu Jun 01, 2006 8:05 pm    Post subject: Reply with quote

The yellow foam absorbs well up to @400Hz, above that like other speaker damping materials its a diffuser and attenuates reflections.

You'll have to get your head around sound and vibration absorbants, before playing in an anechoic chamber and redesigning your speakers.

If it's undamaged and does not smell of vinergar (bacterial activity due to dampness), leave it alone.
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henryc
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Location: Gloucestershire

PostPosted: Fri Jun 02, 2006 12:01 am    Post subject: Reply with quote

Hi Colin
Thanks , I do understand the principle of using the foam to absorb eroneous and unwanted internal vibrations and sound. My question was searching for a better solution and whether there were now better materials which would better dampen the internal reflections?
Ie have the materials today superceeded the performance of the old foam used?
The existing yellow foam is fine in terms of condition,happily no smelly foam! and structurally sound. so if it's adequate I will leave it all well alone
Thanks again for your views
Best Regards
Henry
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Gary
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PostPosted: Fri Jun 02, 2006 12:32 am    Post subject: Reply with quote

I know of someone who internally braced their speakers with wood (glue, screws), basically making them much heavier and the wood less prone to vibration. Afterwards they sounded better than before.

These speakers were not KEFs.

However, this would alter the internal air volume and probably affect the speaker in other ways that the designer did not intend.

Whatever you do, I recommend that you keep the original parts and the ability to restore the speakers back to original spec. Just in case.
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ColinR
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PostPosted: Fri Jun 02, 2006 10:31 am    Post subject: Reply with quote

Quote:
searching for a better solution and whether there were now better materials which would better dampen


As you're seeking an objective comparative analysis it's either a diy approach or finding records or large enough old samples of foam that can be tested against a modern material.

Vitafoam in Manchester may be able to assist with comparative analyses of their modern damping materials which may or may not outperform earlier products, however I doubt that they've got any old foam or comprehensive records from the 70's or 80's around.
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henryc
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PostPosted: Fri Jun 02, 2006 12:07 pm    Post subject: Reply with quote

Hello Colin
No nothing as scientific as that ,Just the quest to see whether damping materials had improved significantly since these were built and if so whether it is worth exploring .
Believe me I would only change the insides if a substantial improvement in sound quality could be created.
The speaker has only two units . The 15 inch LF unit and the T52 which is an enclosed unit . The Bass has improved since I rewired the speakers.
The output is faster , tighter ,seemingly deeper & more controlled than before.
The bass on some recordings organ Jazz Percussive works is so deep that I have had to go round the room searching out items that annoyingly vibrate in unison .
It is quite staggering and impressive, I guess the 15 inch cones can shift alot of air when needed and if they can be better controlled by newer materials perhaps the bass can be even better,who knows?
All the best
Henry
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proffski
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Location: Tewkesbury UK

PostPosted: Fri Jun 02, 2006 6:49 pm    Post subject: Reply with quote

At very low frequencies exotic foam has little effect on the bass; cabinet design is the secret as is type of loading.

I have however used combinations of foams and materials in TLs as well as reflex loudspeakers with considerable success. This was copious amount of time with trial and error, rather than science. Amongst some of the "foams" I used one of the better ones were these. Be warned, rather expensive!
http://www.canford.co.uk/commerce/resources/catdetails/2661.pdf

http://www.sonex-online.com/

Designed for uses other than loudspeakers, I was fortunate to get some leftovers as samples.
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henryc
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PostPosted: Sat Jun 03, 2006 11:47 am    Post subject: Reply with quote

Thanks Proff
I 'll look into it
ATB
Henry
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