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Any advice on lining and damping Baileys tl speakers ?

 
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frank
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PostPosted: Sat Aug 16, 2008 5:53 am    Post subject: Any advice on lining and damping Baileys tl speakers ? Reply with quote

I have got MDF cut ready to construct a pair of Baileys Transmission lines, the second version with internal triangular folds, using my Kef-Kit 3 drivers.
I'm just not quite sure how to line and damp them.

I managed to get some long haired wool (Leicester). Australia is the worlds biggest producer of wool and I thought it must be possible to get some somewhere.Its messy to wash but it turned out ok.

My question is how to line the cabinet walls and the internal baffles. Ive got some limited quantities of 10mm and 12mm thick felt. I thought it should be applied on the cabinet walls and rear with some sort of acoustic foam on the internal baffles ?
But then I don't know what sort of acoustic foam ? I am actually finding it hard to work out and get acoustic foam - would any sort of reasonably dense, egg-shell contoured foam from a rubber supply place do? Do the whole of the internal baffles need to be lined with it ?

But then I also thought the felt could be put on on the internal baffles with something else on the walls and rears and would I need foam in that case ?
I gather the foam damps a different part of the sound spectrum.

Any recommendations ?
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ColinR
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PostPosted: Sun Aug 24, 2008 10:46 am    Post subject: Reply with quote

Bit quiet around here Sad .

Bitumised felt (use car underseal and a staple gun) is sometimes known as Deadshete, for the middles of panels and thin dividers.

You want to find 2” thick upholstery foam down at your local market.

In the UK one firm in Middleton, Manchester also makes acoustic foam and duvet/speaker glass wadding; it's not the chemistry that changes between products either Shocked .

The lowest density (weight per lump) is the type you want, so when you pick up a metre length it’ll droop a bit.

The 0.75” egg-crate foam is a bit dense but ok for mounting crossovers, you want the lighter 2” if you want to do a lumpy IMF bass section.

Lumpy because the induced micro eddies causes standing waves to build up. The maths and physics involved are used in weather pattern monitoring and forecasting; got a Cray? Cool
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proffski
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PostPosted: Sun Aug 24, 2008 10:53 pm    Post subject: Reply with quote

Please look up our extended tuning fiasco building the HALF Wavelength TL or Labyrinth or whatever!
It did take forever and the outstanding results were magnificent.
I will not subscribe to any other theory. Once tuned the TL is glorious.
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DrBoar
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PostPosted: Fri Sep 12, 2008 1:35 pm    Post subject: Reply with quote

First third. Have a lot of damping material. All walls covered by flet and them som BAF to top it of.
Second half: Less damping say som felt on the walls only
Third half: No damping at all or a dense rockwoll wedge in the bends of the pipe.

The idea of the pipe is to use the fundamental output but reduce the unwanted harmonics. Damping material is most effective at the velocity maximum (at the open end for the fundamental and at 1/3 and 2/3 for the thrid harmonic and 1/5 2/5... for the fifth and so on)

Damping material in the first 1/3 to 1/2 of the pipe will be att velocity maxima for all higher harmonics but not affect the main resonanse that much.
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proffski
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PostPosted: Fri Sep 12, 2008 1:48 pm    Post subject: Reply with quote

I reiterate.
The TL or Labyrynth or Mutant Reflex we built was tuned almost half that of the Bailey design.

It took longer in long extended listening tests to get it to sound correct to two peoples ears before it was finaly glued and screwed together.
As my postings already mentioned, it took several damping materials to stop the thing hooting at specific frequencies or not work properly at all.#
We tried the density loading as in the Bailey design, it was close.
Perhaps I was foolhardy to try and be clever and make it twice as long... Embarassed

I am now a convert and restate from yet another posting...

"The best (not the deepest) and most accurate, fast bass I have ever heard was from B&W DM70s. They were let down by low power handling.

I am a sealed enclosure advocate for 2nd best and for 1st if I could afford them would be two pairs of the top new QUAD panels as a frind has driven by MF 1KW amplifiers...
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frank
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PostPosted: Wed Sep 17, 2008 9:27 am    Post subject: Advice on Lining and damping Bailey's TLs. Reply with quote

Apologies for not responding to any of these posts, someone died in my family so I have been preoccupied elsewhere.

Proffski-I haven't been able to narrow down your tuning posts on the TLS - your prolific and finding them out of 560 postings is a little difficult.

I thought that combining DrBoar's and ColinR's suggestions I might use:

1st compartment: 10 or 12 mm felt on the walls and dividing panel
2nd compartment: felt on the back wall and equivalent of Deshete on the two dividing panels.
3rd compartment: limited felt on the panels and walls ie to the extent of the mid and treble drivers. Kef recommended using damping behind the mid-range in the KefKit3 and similar designs but then I might leave the rest of that section undamped as DrBoar suggested.

Also suspend long-haired wool with a net in each enclosure in the densities recommended in the original article.

Any comments on that? Thank you for your replies by the way.
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proffski
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PostPosted: Wed Sep 17, 2008 10:16 am    Post subject: Re: Advice on Lining and damping Bailey's TLs. Reply with quote

We ended up using the following.

Dr Bailey Specified Wool from Wilmslow.
Sculpted foam.
2cm thick felt and BAF wadding.

THe initial problems were horrendous.
No bass, resonances at many frequencies.
It was a long time before we got it 'right' and the results were indeed magnificent.

I'll stick with 1st order boxes though, easier to calculate and no voodo involved or back to education... Laughing
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frank
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PostPosted: Wed Sep 17, 2008 11:12 am    Post subject: Re:Any advice on lining and damping Baileys tl speakers ? Reply with quote

Yes,well, in retrospect I have to admit that something like Wouter's design would have been a lot easier and would probably give a decent bass extension without the trouble.Some of the materials in the original design have become a bit esoteric by now and cutting the angles for the internal panels wasn't that easy for me.
But it will be interesting to see how they sound.

http://www.hifiloudspeakers.info/PersonalKefTreasures/Wouter/Wouter.html
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proffski
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PostPosted: Wed Sep 17, 2008 1:20 pm    Post subject: Re:Any advice on lining and damping Baileys tl speakers ? Reply with quote

Another thing I never figured out was that to my ears at least in the same cabinet but with removable baffles the old shape B139 sounded quite different to the new one?
Any ideas anybody?
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frank
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PostPosted: Thu Sep 18, 2008 1:27 am    Post subject: Re:damping & lining Baileys TLS Reply with quote

Proffski -
Where did you put the long-haired wool, the BAF and the sculpted foam?

I would be interested in reading your posts on tuning
but - do you have a starting link ?
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proffski
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PostPosted: Thu Sep 18, 2008 10:57 am    Post subject: Re:damping & lining Baileys TLS Reply with quote

I may still have the pictures of the internals during testing, memory is playing tricks as these were finished when I bought the first model of the Philips CD player when it was released. A long time ago!

The sculpted foam was on front and back all the way down to the port.
Probably a net of fairly closely packed wool half way down and much looser packing density elsewhere. BAF was a roll immediately behind the B139.

The B110 was also in a long tube with a multi density foam plug shaped like a pyramid at the back, sharp end facing the B110, rest of tube was filled with wool... HF was Decca London Horn.
Tri-Amped 24dB octave crossovers. Six seperate mono amplifiers.
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frank
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PostPosted: Thu Sep 18, 2008 2:43 pm    Post subject: Re: stuffing and lining Bailey's TL's. Reply with quote

You didn't anything by halves there! An interesting project though by the sounds of it.
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proffski
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PostPosted: Thu Sep 18, 2008 5:49 pm    Post subject: Re: stuffing and lining Bailey's TL's. Reply with quote

frank wrote:
You didn't anything by halves there! An interesting project though by the sounds of it.


Still working in a friends house in Cheltenham... Smile
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