Kef Transmission Line score. Modification advise needed

[kelossus]

After hearing a pair of KEF TL's a few years ago I was somewhat impressed by their sound. Always had the intention of picking up a pair locally if they came up for the right price and today was that day. Paid very little for these so I am wanting to give them a bit of TLC to restore them.

 

These were a DIY job and are a bit of an oddity in their appearance and design. They appear to be DIY Bailey cabinets with the hf/mf drivers mounted on an open baffle on top, this is removable. One of the woofers is cactus, sunken spider and the coil is grinding. Obviously over driven at some point.

 

Looking to source another driver but more importantly I wanted to move the B110 and T27 into the cabinet with the woofer as is standard with the TL designs. Happy to keep the crossovers external and bi-wire them. Crossovers are rather unique and I am trying to match the values to any known TL designs.

 

Does anyone have any advice or caveats regarding the movement of the drivers into the TL cabinet? Anyone have a B139 SP1044 spare?

 

[Zaphod Beeblebrox]

Orienting the mid/high panel vertically will improve things considerably, as will removing the piezo driver. I don't like (actually, I HATE them with a deep, unabiding passion) the old PIO caps. You can expect significant improvements by replacing them with modern, poly carb or poly prop replacements. The inductors should be re-aligned for minimal interference too. It would be worthwhile tracing the schematic of the crossover, measuring the inductors and see what can be retained. I have always mounted the B110 in a long, open tube, lined with sheep's wool. Works well with that driver. 

[kelossus]

17 hours ago, Zaphod Beeblebrox said:

Orienting the mid/high panel vertically will improve things considerably, as will removing the piezo driver. I don't like (actually, I HATE them with a deep, unabiding passion) the old PIO caps. You can expect significant improvements by replacing them with modern, poly carb or poly prop replacements. The inductors should be re-aligned for minimal interference too. It would be worthwhile tracing the schematic of the crossover, measuring the inductors and see what can be retained. I have always mounted the B110 in a long, open tube, lined with sheep's wool. Works well with that driver. 

Would you recommend not placing the Mid/High drivers in the TL cabinet? The top panel is already fairly high and orienting the drivers vertically would put the tweeter around 1.4m high.

 

I do intend to remove the Piezo tweeter.

 

The MH of the inductors is actually written on them. Apparently they were hand wound by the gentleman who built the speakers. Unsure how good they would be.

 

If I do put the speakers in the TL cabinet can I mount the B110 in the tube like you mentioned?

[Zaphod Beeblebrox]

22 minutes ago, kelossus said:

Would you recommend not placing the Mid/High drivers in the TL cabinet? The top panel is already fairly high and orienting the drivers vertically would put the tweeter around 1.4m high.

Well, that would be up to you. It would be easier, but a little less tidy. There are advantages in placing HF drivers away from large, flat surfaces, which is why B&W have been doing it for several decades. 

 

22 minutes ago, kelossus said:

 

I do intend to remove the Piezo tweeter.

 

The MH of the inductors is actually written on them. Apparently they were hand wound by the gentleman who built the speakers. Unsure how good they would be.

They appear to be fine. Value-wise, they're easy enough to check. 

 

22 minutes ago, kelossus said:

 

If I do put the speakers in the TL cabinet can I mount the B110 in the tube like you mentioned?

Sure. It's how I did mine. A tube all the way through the back of the box and open at the end. Mids were fabulous. You could do worse than re-using the inductors and building a set of Radford crossovers. You should be able to find my uploaded schematic on SNA. 

[kelossus]

2 hours ago, Zaphod Beeblebrox said:

Sure. It's how I did mine. A tube all the way through the back of the box and open at the end. Mids were fabulous.

Just took of the rear baffle to confirm the design of the TL. They identical to the below design which I believe is the Bailey TL?

 

If I were to put the B110 in a tube all the way through the cabinet it would have to go through the internal panel that forms part of the TL. Is this what you did?

 

[Al.M]

You could also orient the midrange on top with dome tweeter under it.

 

If there is a crossover network dividing the dome tweeter from the piezo unit it should also be removed if the piezo is going.

 

Tubing the mid driver through the transmission line cabinet in theory may reduce the TL cross section area and affect sound.

[kelossus]

13 hours ago, Al.M said:

Tubing the mid driver through the transmission line cabinet in theory may reduce the TL cross section area and affect sound.

Yes I was curious as to how the tube displacement would affect the TL design. @Zaphod Beeblebrox Is this a non issue?

 

On the original Bailey TL's was the T27/B110 in an internal enclosure inside the TL?

[Zaphod Beeblebrox]

6 minutes ago, kelossus said:

Yes I was curious as to how the tube displacement would affect the TL design. @Zaphod Beeblebrox Is this a non issue?

Pretty much a non-issue.

 

6 minutes ago, kelossus said:

 

On the original Bailey TL's was the T27/B110 in an internal enclosure inside the TL?

Bailey suggested running a tube through the back would be better than his original idea. I will try to locate the original 1972 article for you. Don't hold your breath.

[kelossus]

1 hour ago, Zaphod Beeblebrox said:

Pretty much a non-issue.

 

Bailey suggested running a tube through the back would be better than his original idea. I will try to locate the original 1972 article for you. Don't hold your breath.

I think I found the 1972 article. In it Bailey states:

 

In practice, it has not been found necessary to use a separate enclosure for the Mid-Range unit*

*However there may be an audible improvement if an absorbent filled enclosure is used behind the mid-range unit ED.

 

Did you run the tubed enclosure in the Bailey cabinets? Did you have to cut into one of the internal panels that form the TL? From what I can see running a tube horizontally from the baffle to the rear of cabinet would foul slightly with one of the internal panels.

 

 

[Zaphod Beeblebrox]

44 minutes ago, kelossus said:

I think I found the 1972 article. In it Bailey states:

 

In practice, it has not been found necessary to use a separate enclosure for the Mid-Range unit*

 

Yeah, that's wrong. You MUST use a separate enclosure.

44 minutes ago, kelossus said:

 

*However there may be an audible improvement if an absorbent filled enclosure is used behind the mid-range unit ED.

Yep. Agreed.

 

 

44 minutes ago, kelossus said:

Did you run the tubed enclosure in the Bailey cabinets?

I did a pair with a small sealed enclosure and another with a long tube through the back. The long tube sounded much better. 

 

44 minutes ago, kelossus said:

 

Did you have to cut into one of the internal panels that form the TL?

Yeah, but don't forget: Me and dad did that part during the construction phase. Easy to manage at that point. Not so easy ater. 

44 minutes ago, kelossus said:

 

From what I can see running a tube horizontally from the baffle to the rear of cabinet would foul slightly with one of the internal panels.

 

Yeah, some cutting is required.

[Sansui77]

Any updates there @kelossus??

 

I was pretty impressed with the versions i did a while back for my father. The only issue was they needed a high powered amp to drive them. I also added a coles super tweeter for a more airy top end.

 

Edited November 22, 2018 by Sansui77

[kelossus]

On 22/11/2018 at 2:30 PM, Sansui77 said:

Any updates there @kelossus??

 

I was pretty impressed with the versions i did a while back for my father. The only issue was they needed a high powered amp to drive them. I also added a coles super tweeter for a more airy top end.

 

Got the replacement woofers and after a few minor issues the speakers are working again. As they are, they sound pretty good with the drivers up top. So much so I am considering leaving them that way.

 

I have heard the Kef TL's before and for some reason I remember them having a little more bass then I am hearing with this pair currently. I have no idea what crossover schematic has been used and none of the components match any of the available schematics. This may be the culprit for the lack of bass? I don't know.

[Sansui77]

Is the transmission line filled with insulation?

My dads Bailey's fitted with the extra Coles super tweeter.

[Zaphod Beeblebrox]

5 hours ago, kelossus said:

Got the replacement woofers and after a few minor issues the speakers are working again. As they are, they sound pretty good with the drivers up top. So much so I am considering leaving them that way.

 

I have heard the Kef TL's before and for some reason I remember them having a little more bass then I am hearing with this pair currently. I have no idea what crossover schematic has been used and none of the components match any of the available schematics. This may be the culprit for the lack of bass? I don't know.

Provided the line has been correctly stuffed (not too tight and not too loose) with sheep's wool (do not substitute) then the bass will be fine. Thing with the Bailey T-lines is that the bass is VERY uncoloured. Mine were flat to 23Hz. I found that if they didn't sound bassy, then there was likely to be no bass on the recording. 

 

Did you flip the mid/high enclosure 90 degrees? Should improve imaging considerably. 

[kelossus]

5 hours ago, Sansui77 said:

Is the transmission line filled with insulation?

My dads Bailey's fitted with the extra Coles super tweeter.

Yes they are insulated.

 

They look mint. My cabinets look bigger? May be an optical illusion but did you have the measurements of the box? They are bailey TL's right?

 

3 hours ago, Zaphod Beeblebrox said:

Provided the line has been correctly stuffed (not too tight and not too loose) with sheep's wool (do not substitute) then the bass will be fine. Thing with the Bailey T-lines is that the bass is VERY uncoloured. Mine were flat to 23Hz. I found that if they didn't sound bassy, then there was likely to be no bass on the recording. 

 

Did you flip the mid/high enclosure 90 degrees? Should improve imaging considerably. 

Definitely filled with sheeps wool. Unsure if it is packed to the right density though.

 

Just as an example regarding the crossovers the inductor in the woofer is 8mh. This does not match any schematic I can see. Also there is a 9mh inductor in the mid-range circuit somewhere? That seems insane right? Need to have a play with the crossovers and possibly look at removing the inline fuses as I assume these are not desirable in a network.

 

I have not flipped the top enclosure 90 degrees yet.

Edited November 23, 2018 by kelossus

[Graywulf]

On 11/11/2018 at 12:23 PM, kelossus said:

Would you recommend not placing the Mid/High drivers in the TL cabinet? The top panel is already fairly high and orienting the drivers vertically would put the tweeter around 1.4m high.

 

I do intend to remove the Piezo tweeter.

 

The MH of the inductors is actually written on them. Apparently they were hand wound by the gentleman who built the speakers. Unsure how good they would be.

 

If I do put the speakers in the TL cabinet can I mount the B110 in the tube like you mentioned?

Damn, wish I'd seen this thread back when (yeh EPIC thread dredge)

kelossus IF you still have these speakers, I hope you left the mf/hf drivers on the top. Reason? I think I know what the builder was doing (with an additional super tweeter) He was probably following the Nightingale NM-1 speaker design. Bailey TL enclosure but mf/hf placed on top of it. I had a pair of these for 20plus yrs, my ex wife ended up with them, and 'gave them away'  :((  because the foam round the peerless mid started to degrade. Aaaaaaargh!!!!!!!!! 

https://www.hifiwigwam.com/forum/topic/93842-nightingale/page/2/