KEF transmission line project

[koozoop]

Good evening.

I decided to try the 1972 Bailey design. I will built the cabin for the B139 alone and place on top the CS1's enclosure after removing the CS1 crossover since the FN10 will be used (with SP1057 though).

What kind of amplifier would you recommend for these speakers? I've heard people here in Greece saying that even a 100Watt amp couldn't "move" the B139 in these enclosures. These will be placed in a 50sq.m living room.

[planet10]

44 minutes ago, koozoop said:

I decided to try the 1972 Bailey design..

I have done a redraw of the original Bailey cabinet to aid anyone doing this project. 

dave

[koozoop]

Good evening Dave,

 

isn't this the 1965 design?

[planet10]

Oct 1965.

 

dave

[Zaphod Beeblebrox]

4 hours ago, koozoop said:

Good evening.

I decided to try the 1972 Bailey design. I will built the cabin for the B139 alone and place on top the CS1's enclosure after removing the CS1 crossover since the FN10 will be used (with SP1057 though).

What kind of amplifier would you recommend for these speakers? I've heard people here in Greece saying that even a 100Watt amp couldn't "move" the B139 in these enclosures. These will be placed in a 50sq.m living room.

A GOOD 100 Watt amp will run them perfectly well. I ran mine with various amps over many years in a large room (7 Metres X 4 Metres, well damped). Even my 60 Watt Luxman SQ507 ran them very nicely. Good luck with your project. The Radford crossover is an excellent choice. Don't forget: ONLY use long haired sheep's wool for damping material. Not too much and not too little. 

[koozoop]

Thank you, I will post pictures during the construction phase.

 

Sth else though... since I'm an electronics rookie , what components would you suggest for the particular XO? Which AWG and core is suitable for inductors? The capacitors should be polypropylene or electrolytic?

 

Thank you in advance!

[koozoop]

OK, I managed to find the specs for the components through a shop here in Greece that has made these before.

 

Dave, could this XO be possibly used with any of your TL's here: http://www.t-linespeakers.org/projects/vProjects.html

The triangulated one could be a nice alternative. The B110-T27 enclosure could be placed next to to the B139 enclosure on a stand.

[Al.M]

As a variation to the Bailey design the best DIY sub I have used is a Kef B139 in a TL with external box dimensions of 70cm tall x 36cm width x 56cm depth, with woofer and slot port facing up, which made it less directional sounding.

 

The internal TL cross section area was about the same as the woofer cone surface area about 11 x 32cm folded 4 times with no tapering so about 2.8m TL length. I used a modest 65 Jaycar sub plate amp and it was good enough. The design had incredible bass extension that I never heard in any other commercial sub although sensitivity was lowish and max output could in some cases have been a little more as the woofer maxed out when pushed harder.

 

I plan to build this sub again and maybe lower its height and add another TL fold to compensate, which would be less bulky than the Bailey dimensions.

 

I have a spare driver and might experiment with an isobaric TL sub, which would halve the internal volume but probably affect the TL length and reduce efficiency another 3dB.

Edited October 20, 2017 by Al.M

[koozoop]

Would love to see this design as well...

[Al.M]

I understand the B139 is good for a 100L ported cabinet, so an isobaric design with two clamshell woofers would only need about 50L. Downside is that a single B139 has about 83dB efficiency so isobaric would be 80dB so quite low.

Edited October 20, 2017 by Al.M

[planet10]

11 hours ago, koozoop said:

Dave, could this XO be possibly used with any of your TL's here: http://www.t-linespeakers.org/projects/vProjects.html

I’m not surw of which XO you refer, but if all the parts are the same it should work ok. xos are very driver specific and the box can also play a role.

 

The triangulated TL topology was based on one i developed for the B200 back in the late ‘70s.

 

dave

Edited October 20, 2017 by planet10

[koozoop]

Thank you Dave. I was referring to the Radford FN10 XO mentioned in this thread. This is the one I'm going to use and because timberworks are not a problem for me I'm thinking of trying one of your designs, maybe next year, to hear the difference.

 

Zaphod mentioned that the best choice for insulation is the long-fibre wool (Bailey suggests 0.5 lb/cf, ie about 1,0 kilo for each speaker). I was wondering if low density open cell foam can be used instead (like Bud Fried did in his designs)? Of course one has to calculate the right viscosity... The reason I'm asking is that in order to keep the wool packed (it falls under it's weight after some time) I have to keep the bottom of the speaker cabin screwed (well screwed that is, about 3 screws with tee nuts at each side) so that it can be easily visited and maintained. With foam I could avoid this.

[planet10]

20 minutes ago, koozoop said:

 I was referring to the Radford FN10 XO mentioned in this thread. This is the one I'm going to use and because timberworks are not a problem for me I'm thinking of trying one of your  designs, maybe next year, to hear the difference.

The Radford XO was for very different drivers, it could be a bit of a crapshoot. Personally i would biamp the woofer and use the most appropriate XO you can find for the drivers in the satellite. Since i would most likely use a good small fullrange as a midtweeter there would be no passive XOs. A mod i’d love to try the next time i can bag a set of cheap IMF TLS80s or larger.

 

Zaphod mentioned that the best choice for insulation is the long-fibre wool (Bailey suggests 0.5 lb/cf, ie about 1,0 kilo for each speaker). I was wondering if low density open cell foam can be used instead (like Bud Fried did in his designs)? Of course one has to calculate the right viscosity... The reason I'm asking is that in order to keep the wool packed (it falls under it's weight after some time) I have to keep the bottom of the speaker cabin screwed (well screwed that is, about 3 screws with tee nuts at each side) so that it can be easily visited and maintained. With foam I could avoid this.

 

Some of the newest specialist fluff-type damping material is every bit as good as lamb’s wool without the issues of moths eating it or sagging. I use acoustastuff, in europe there are some others. At a minimum i would mix lamb’s wool half & half with something like acoustastuff to avoid the sagging issue. I really question how well open cel foam works.

 

As well as acouststuff volume fill damping, i will line the walls near the driver with 12mm cotton felt (recycled denim UltraTouch — wool felt also works).

 

dave

[koozoop]

Quote

The Radford XO was for very different drivers, it could be a bit of a crapshoot. Personally i would biamp the woofer and use the most appropriate XO you can find for the drivers in the satellite.

That's why I'm currently looking at an AMC 2445 (Power Amp, 2x90 Watt @ 8 Ohms or 4x45 Watt @ 8 Ohms, can be used for bi-amping, has volume controls for each channel). I can use this with the Radford XO as a stereo amp or with the CS1 crossover and bi-amp the B139.

 

Quote

At a minimum i would mix lamb’s wool half & half with something like acoustastuff to avoid the sagging issue

Nice thought! I can order Acousta-stuff from ebay or Amazon in Europe. I will check it's properties to decide for the proper mixing.

 

Quote

i will line the walls near the driver with 12mm cotton felt

eg the upper half of the first line?

[planet10]

10 minutes ago, koozoop said:

eg the upper half of the first line?

The right area, you might not need to be that thorough.

 

dave

[Zaphod Beeblebrox]

36 minutes ago, planet10 said:

The Radford XO was for very different drivers,

 

No, it was not. In fact, the Radford crossover addressed some of the flaws inherent to the B110 and T27 that KEF managed to ignore for years. 

 

Quote

 

Some of the newest specialist fluff-type damping material is every bit as good as lamb’s wool without the issues of moths eating it or sagging. I use acoustastuff, in europe there are some others. At a minimum i would mix lamb’s wool half & half with something like acoustastuff to avoid the sagging issue. I really question how well open cel foam works.

 

If done correctly, the wool does not sag (mine didn't, even after 10 years) and is VASTLY superior to any other product. Examine wool fibres under an electron microscope and you'll understand why wool is so good. See the little 'hooks' on the animal fibres? They don't exist on man-made ones. Cashmere would be nice too. Wool is cheaper. I will remind you that Dr Bailey spent a good deal of time researching the correct stuffing material on his enclosures. Over the years, I've heard a number of Bailey T-Lines. The crappy ones all used man-made filling and/or KEF crossovers. 

 

Quote

 

As well as acouststuff volume fill damping, i will line the walls near the driver with 12mm cotton felt (recycled denim UltraTouch — wool felt also works).

 

dave

I don't have a problem with treating the internal surfaces of the enclosure, but I don't see where anyone has done the research that Dr Bailey has with that particular enclosure WRT correct stuffing material. 

Edited October 20, 2017 by Zaphod Beeblebrox

[planet10]

No, it was not. In fact, the Radford crossover addressed some of the flaws inherent to the B110 and T27 that KEF managed to ignore for years.

 

I don’t know that KEF ever got the XO for these right, but the Radford was designed for Goodman’s sourced Bass & mid drivers & a Peerless tweeter.

 

...and is VASTLY superior to any other product.

 

A questionable assertion.

 

...but I don't see where anyone has done the research that Dr Bailey has with that particular enclosure.

 

Bailey’s research was some 40 years ago… much has been learned about TLs, particularily in the last decade & a half as modern, accurate modelers have spawned a new generation of TLs.

 

dave

[koozoop]

Mahogany sound suggest to line all enclosure walls with a layer of fiber: http://www.madisound.com/pdf/acousta-stuff.pdf

Edited October 21, 2017 by koozoop

[planet10]

Thanx i hadn’t seen that. 

 

A couple points:

1/ ½ pound per ft^3 is a very generalized figure, for sealed or TLs.

2/ i’d line a BR with something denser than fluffed acoustastuff… their method seems aweful fiddly to, but they are trying to see th stiff. Note that you are not building a BR.

3/ fluffing this stuff is not easy because it wants to stick together — lots of barbs like the worst in Zaphs micrograph — but it needs doing. Here 40g in a sandwich bag as i ship it, and after it is fluffed.

 

 

4/ A TL does not necessarily need to have damping through-out the entire length, depends on the TL. In an end-loaded TL like the Bailey you need more damping since not many of the tricks used to get away with less (and therefore usually more bass) are used.

 

 

[koozoop]

Bailey suggests a packing density of 0.5lb/ft^3 which is about 2.2-2.3lbs of sheep's wool. Maybe I will order some more to test...

[planet10]

That is where everyone gets their ½ lb per ft^3, but you have to adjust to taste.

 

dave

[koozoop]

That's why I will keep enclosures bottom removable (well screwed though on the perimeter including tee-nuts).

[koozoop]

On 10/18/2017 at 10:26 PM, Zaphod Beeblebrox said:

A GOOD 100 Watt amp will run them perfectly well. I ran mine with various amps over many years in a large room (7 Metres X 4 Metres, well damped). Even my 60 Watt Luxman SQ507 ran them very nicely.

I found a pair of Audiolab's 8000p power amplifiers but the seller told not to even think of using them to drive these speakers and I should look for something with lots of amperage.

[Zaphod Beeblebrox]

4 hours ago, koozoop said:

I found a pair of Audiolab's 8000p power amplifiers but the seller told not to even think of using them to drive these speakers and I should look for something with lots of amperage.

Nope. The KEF T-lines are dead easy to drive. Like I said before, I drove mine with a Luxman L-507. The biggest amp I used was a Marantz Model 500 (320 Watts/channel - measured). Except for the ME150, none of the amps I used could be classed as 'high current'. In any case, though I am not familiar with the 8000p, I thought most Audiolab amps were reasonably high current. Though, not if they are run 'bridged'. Bridged amps deliver far less current. 

Edited October 21, 2017 by Zaphod Beeblebrox

[planet10]

On 2017-10-20 at 12:47 PM, planet10 said:

I’m not sure of which XO you refer,

Caught out by time (i have a good excuse — starting almost 5 months ago i spent 5 months in hospital and no doubt lost track of somethings). I see i posted a redraw of the FN10 which zaph traced… yes that should work, my comments about Goodmans drivers refers to the FN11/12 here http://www.t-linespeakers.org/classics/radford.html

 

dave