I hope someone who has built Chris Rogers' Transmission Line Monitors from the August 1975 Hi-Fi Answers notes can help me here. I am trying to get MDF cut at a timber merchants but am not 100% certain that I entirely understand the dimensions.
Based on Figure 1 (LINK) I can see that the top (5) and bottom (6) fit inside the sides (3 & 4) and that the front and back (1 & 2) fit inside the resulting box. What I don't understand is why the top and bottom are half an inch less deep than the sides, surely they too should be 18 inches deep?
Figure 2 (LINK) is equally confusing. What is going on with the baffle board, it seems to be "notched" at the top and bottom panels but this isn't mentioned anywhere in the text. The various dimensions at the top of the cabinet add up to 18" assuming that the port panels (9, 10 & 11) are ¾" thick but I am somewhat confused by the exact positioning of the port panels. Having spent time trying to understand Figure 2 I get the impression that the depth of the B139 "duct" goes from 5" (bottom of 11) to 4¼" (top of 11) to 4" (top of 11 & 10) to something undefined (bottom of 10 & 11) to something else undefined (bottom of 10 & 9) to 2¾" (top of 9 & 10) to 3¼" (top of 9 & rear of baffle) to 3" (bottom of 9 & rear of baffle)
i.e. 5" => 4¼" => 4" => ? => ? => 2¾" => 3¼" => 3"
This despite the comment in the middle column of page 1 of the notes that: "The duct starts with an area of 66 sq.in. at the drive end and is reduced by 50% to finish at 30 sq. in. at the duct mouth."
Does it actually matter that the duct doesn't consistently reduce in size? Would it cause a problem if panel 9 was vertical, making the duct the same size for the whole length of the final inverted "U" section?
Figure 9 (LINK) also appears to be missing a dimension or two.
I need to convert all these dimensions into metric and in addition I aim to use 25 mm MDF rather than 18 mm (¾") for the external panels.
If anyone has built a pair of these speakers I would greatly appreciate any clarification, I would rather specify the cuts accurately first time around!
Many thanks.
Based on Figure 1 (LINK) I can see that the top (5) and bottom (6) fit inside the sides (3 & 4) and that the front and back (1 & 2) fit inside the resulting box. What I don't understand is why the top and bottom are half an inch less deep than the sides, surely they too should be 18 inches deep?
Figure 2 (LINK) is equally confusing. What is going on with the baffle board, it seems to be "notched" at the top and bottom panels but this isn't mentioned anywhere in the text. The various dimensions at the top of the cabinet add up to 18" assuming that the port panels (9, 10 & 11) are ¾" thick but I am somewhat confused by the exact positioning of the port panels. Having spent time trying to understand Figure 2 I get the impression that the depth of the B139 "duct" goes from 5" (bottom of 11) to 4¼" (top of 11) to 4" (top of 11 & 10) to something undefined (bottom of 10 & 11) to something else undefined (bottom of 10 & 9) to 2¾" (top of 9 & 10) to 3¼" (top of 9 & rear of baffle) to 3" (bottom of 9 & rear of baffle)
i.e. 5" => 4¼" => 4" => ? => ? => 2¾" => 3¼" => 3"
This despite the comment in the middle column of page 1 of the notes that: "The duct starts with an area of 66 sq.in. at the drive end and is reduced by 50% to finish at 30 sq. in. at the duct mouth."
Does it actually matter that the duct doesn't consistently reduce in size? Would it cause a problem if panel 9 was vertical, making the duct the same size for the whole length of the final inverted "U" section?
Figure 9 (LINK) also appears to be missing a dimension or two.
I need to convert all these dimensions into metric and in addition I aim to use 25 mm MDF rather than 18 mm (¾") for the external panels.
If anyone has built a pair of these speakers I would greatly appreciate any clarification, I would rather specify the cuts accurately first time around!
Many thanks.
I don't think that the front baffle is routered. Page 1 of the article notes "Obviously you can't get four 1 foot pieces from a 4 feet board but the thickness of the cuts allows for a slight clearance around the fronts and backs . . . Without this the panel fits tight and no one wants to have to bang into place panels with expensive drive units mounted on them!".
Having said that, figure 1 does show the top and bottom (5 & 6) as being ½" less deep than the sides (3 & 4) but then again, the front and back (1 & 2) are the same height, 1½" less than the sides, presumably to allow for the ¾" thickness of the top and bottom!
I have now come up with the following dimensions:
From 25 mm MDF:
4 off 875 x 300 (front & rear - 5 mm undersized all round)
4 off 930 x 470 (sides)
4 off 305 x 470 (top & bottom)
4 off 930 x 470 (sides)
4 off 305 x 470 (top & bottom)
From 18 mm MDF:
I will probably position the front port panel vertically.4 off 305 x 305 (front two port panels)
2 off 250 x 305 (B110 box base)
2 off 260 x 305 (B110 box top)
2 off 450 x 305 (B110 box rear and rear port panel)
2 off 250 x 305 (B110 box base)
2 off 260 x 305 (B110 box top)
2 off 450 x 305 (B110 box rear and rear port panel)
You'd be ahead of the fame using quality plywood. Give you a better, and lighter cabinet.
You have the drivers for this box?
dave
The significant point is that this is a (reasonably well) documented and proven design. Added to this, I was under the impression that MDF is considered to be a better material than plywood? Perhaps the word "quality" has some bearing on this
Maybe true . . . are you able to suggest a superior (reasonably well) documented and proven design?
I am not an expert in this field, I just happen to have a pair of Kef B139s, B110s, T27s and Coles 4001Gs available and would like to make the best use of them I can. As the Irishman said to the lost traveller, "There are better places to start from than here".
From a time well before we had TL modelers and a better understanding of TLs came about.
That is a myth so well perpatrated by the marketing guys so as to have many talented designers believing it. MDFs only advantage is that it is cheap.
You could use the XO as a starting point, but if i were building a box for B139, i would use one of the modern B139 TL variations based on Scott Lindgrens base alignment: Transmission Line Speakers (top 3)
dave
As I have said, my starting point may be sub-optimal but it is where I am; I just happen to have a pair of Kef B139s, B110s, T27s and Coles 4001Gs available and would like to make the best use of them I can.
I accept also that better materials may be available, somewhere, at a price. However, 25 mm MDF is as you say, (relatively) cheap and easily available.
As to the Transmission Line Speakers link, they seem to be "woofers" and fairly "large" or in one case, HUGE? I guess that I could build a pair of LS3/5as using the B110s & T27s and maybe that will be the answer if I can't get anywhere with the Rogers Transmission Line Monitors.
I do appreciate the thought and the suggestions, I just don't think that they really address my requirements
Hi,
FWIW the T27's don't need the 4001G's in a month of Sundays.
I dont like the gap between the B110 and the T27's.
Or the airspace effects on the midrange.
There are different versions of the B110, and different LS3/5A
clones that are better / worse for the different B110 versions.
The B139 has very dissapointing excursion by modern standards.
I don't like the x/o, seems mostly guesswork.
YMMV but if I was you I'd sell all the drivers, as they all go
for very good prices on e-pray, way more than they are
actually practically worth IMHO and start from scratch.
I'd biuld this :
https://sites.google.com/site/undefinition/tarkus
(The nearest thing to a budget WATT/Puppy your going to get.)
or this :
https://sites.google.com/site/undefinition/diy-sunflowers
(Best budget OB mid design that is out there.)
or this :
zaph|audio - zdt3.5
(Just a supremely competent 3.5 way - if you want accuracy.)
All of which I'm confident would slaughter the HFA TL.
rgds, sreten.
FWIW the T27's don't need the 4001G's in a month of Sundays.
I dont like the gap between the B110 and the T27's.
Or the airspace effects on the midrange.
There are different versions of the B110, and different LS3/5A
clones that are better / worse for the different B110 versions.
The B139 has very dissapointing excursion by modern standards.
I don't like the x/o, seems mostly guesswork.
YMMV but if I was you I'd sell all the drivers, as they all go
for very good prices on e-pray, way more than they are
actually practically worth IMHO and start from scratch.
I'd biuld this :
https://sites.google.com/site/undefinition/tarkus
(The nearest thing to a budget WATT/Puppy your going to get.)
or this :
https://sites.google.com/site/undefinition/diy-sunflowers
(Best budget OB mid design that is out there.)
or this :
zaph|audio - zdt3.5
(Just a supremely competent 3.5 way - if you want accuracy.)
All of which I'm confident would slaughter the HFA TL.
rgds, sreten.
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FYI a dutch DIY shop sells a kit of these since decades. And they kept on improving and fine-tuning it, currently in version 8 - now without KEF components. They also use a ribbon tweeter nowadays.
A long time ago I had their build manual of an early version, that one still used KEF components.
Here is the link, it may be fun to try a google translate:
Rogers Monitor 8.0 kopen remo luidsprekers
A long time ago I had their build manual of an early version, that one still used KEF components.
Here is the link, it may be fun to try a google translate:
Rogers Monitor 8.0 kopen remo luidsprekers
You might want to get in touch with
www.falconacoustics.co.uk
Who have a lot of experience with those drivers. They actually make the T27 and B110 again for the Ls3/5a crowd. I believe they offered a kit for the Chris Rogers design at one point and will have experience in how it can be improved or a better use of drivers.
I can't recall if CR's design uses damped panels, in which case MDF may be ok - although apart from a few current BBC revival models, no seemed to follow the original BBC research on use of damping pads. As Dave says, birch ply is lighter and easier to work with. It's main drawback is that it is getting increasingly hard to obtain in the UK, IME.
www.falconacoustics.co.uk
Who have a lot of experience with those drivers. They actually make the T27 and B110 again for the Ls3/5a crowd. I believe they offered a kit for the Chris Rogers design at one point and will have experience in how it can be improved or a better use of drivers.
I can't recall if CR's design uses damped panels, in which case MDF may be ok - although apart from a few current BBC revival models, no seemed to follow the original BBC research on use of damping pads. As Dave says, birch ply is lighter and easier to work with. It's main drawback is that it is getting increasingly hard to obtain in the UK, IME.
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FWIW I heard one of the big TLs using this driver line up at Wilmslow Audio back in the early 90s. I don't know if it was the Chris Rogers or one of the similar variants. It had a lot of bass. In fact, it was overwhelming. This may have been the room or the particular design.
Have a look at Sigfried Linkwitz's site where he has an archive PDF of a Wireless World design using this set of drivers (minus the Coles). It was SL's first published design and, as you might expect, has a lot of measurements and data.
http://www.linkwitzlab.com/Removed pages/x-sb80-3wy.htm
Rogers (Chris not Jim) is not the most respected designer in the audio world. His reviews were often suspect and he started the whole "Quad electronics sound boring" bandwagon.
Have a look at Sigfried Linkwitz's site where he has an archive PDF of a Wireless World design using this set of drivers (minus the Coles). It was SL's first published design and, as you might expect, has a lot of measurements and data.
http://www.linkwitzlab.com/Removed pages/x-sb80-3wy.htm
Rogers (Chris not Jim) is not the most respected designer in the audio world. His reviews were often suspect and he started the whole "Quad electronics sound boring" bandwagon.
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Chris Rogers published a Mk2 version of his TL 3 years after the one referred to here; the article (and the design) was an improvement over the first in terms of the TL design & layout -albeit only retaining the 139 bass driver.
If, as you say, you wish to make best use of them, knowingly using a sub-optimal enclosure from the outset isn't the ideal way of going about it. The TL itself could stand some work, while the layout of the front baffle & spacing between the drivers is not great given the XO frequencies etc., as is pointed out above.
Frankly, unless you want to reproduce a ~early '70s vintage system, I too would be inclined to sell the drivers off. The fact is, more recent products significantly outperform the old KEF units.
If, as you say, you wish to make best use of them, knowingly using a sub-optimal enclosure from the outset isn't the ideal way of going about it. The TL itself could stand some work, while the layout of the front baffle & spacing between the drivers is not great given the XO frequencies etc., as is pointed out above.
Frankly, unless you want to reproduce a ~early '70s vintage system, I too would be inclined to sell the drivers off. The fact is, more recent products significantly outperform the old KEF units.
Thanks for that talaerts, your post led me to this LINK with lots of good images - not so happy about the "Low budget monitor project" slander, how dare they?
Colin, many thanks for your link to the Linkwitz three enclosure article. It looks interesting, particularly in terms of domestic harmony! The crossover looks "challenging", I have located the Linkwitz site but there is no contact email address to ask if the PCB is available.
Thanks to you all for your input . . . and I am unlikely ever to apologise for my love of the Kef drivers . . . or my ESL-57s either.
Colin, many thanks for your link to the Linkwitz three enclosure article. It looks interesting, particularly in terms of domestic harmony! The crossover looks "challenging", I have located the Linkwitz site but there is no contact email address to ask if the PCB is available.
Thanks to you all for your input . . . and I am unlikely ever to apologise for my love of the Kef drivers . . . or my ESL-57s either.
I have built the Linkwitz 3-way system. Had it in my car for some years. Used the b139 woofers in my home system until moving to larger quarters re-defined bass output requirements.
The circuit isn't hard to build, even without a board. Use more modern op amps, or, perhaps better, modern digital methods. I've replaced the analog crossover with a Linux system that does the crossover with all free software. A nice use for my old pentium II laptop.
The circuit isn't hard to build, even without a board. Use more modern op amps, or, perhaps better, modern digital methods. I've replaced the analog crossover with a Linux system that does the crossover with all free software. A nice use for my old pentium II laptop.
Thanks for that talaerts, your post led me to this LINK with lots of good images - not so happy about the "Low budget monitor project" slander, how dare they?
Colin, many thanks for your link to the Linkwitz three enclosure article. It looks interesting, particularly in terms of domestic harmony! The crossover looks "challenging", I have located the Linkwitz site but there is no contact email address to ask if the PCB is available.
Thanks to you all for your input . . . and I am unlikely ever to apologise for my love of the Kef drivers . . . or my ESL-57s either.
Hi, fun thread that you found there.
I must say that I always liked the general appearance of that big Roger box. And if you have the correct components, then why not build it (but I wouldn't spend too much on expensive marine multiplex).
Important is that in page 2 of the linked thread is a picture that shows how much damping material (Bailey's wool) should be used where in the box. TDL also had mighty tramission lines in the 1970s with the B139. It may be interesting to google for plans, if they exist.
Though the advice for selling off the speaker drivers and making a modern design is preferable, if only you were not so married to your vintage KEF units
PS your ESL-57s are amongst the very very best speakers that I ever heard. Fragile but oh so lovely with acoustic music. Quad really knew what they were doing back then.
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John Wright of TDL (and IMF in its earlier incarnation) had their own version of the
KEF woofer. He was also open in his opinion that the TL was a variant of the reflex. These designs - and the Radford which preceded them and the Rogers - seem to follow Bailey's first paper on the TL and ignore his second, which used triangular inserts to reduce internal reflections. If I was building a classic TL with these drivers, I'd have a look at that.
It's interesting that KEF themselves never went the TL route. I'd be inclined to try a sealed enclosure with the B110/T27 in a separate satellite enclosure, a little like the old Reference 105.
http://www.kef.com/html/gb/explore/about_kef/museum/1970s/Reference_Series_105/index.html
Re the Linkwitz crossover - using the MiniDSP digital crossover would be a good route to take to simplify things and add flexibility.
KEF woofer. He was also open in his opinion that the TL was a variant of the reflex. These designs - and the Radford which preceded them and the Rogers - seem to follow Bailey's first paper on the TL and ignore his second, which used triangular inserts to reduce internal reflections. If I was building a classic TL with these drivers, I'd have a look at that.
It's interesting that KEF themselves never went the TL route. I'd be inclined to try a sealed enclosure with the B110/T27 in a separate satellite enclosure, a little like the old Reference 105.
http://www.kef.com/html/gb/explore/about_kef/museum/1970s/Reference_Series_105/index.html
Re the Linkwitz crossover - using the MiniDSP digital crossover would be a good route to take to simplify things and add flexibility.
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I have seen Dr. Bailey's reference to triangular inserts - it makes lots of sense (to me) but it would probably be a nightmare to get it cut. Likewise, I had noticed that despite various TL designs using Kef drivers, Kef never made a TL speaker - perhaps because it would inevitably be large and heavy and this would result in few sales?
I have given considerable thought to putting the B110s & T27s into much smaller, more convenient cabinets (e.g. I have looked at the Falcon Acoustics LS3/5a kits and even thought of buying Falcon crossovers and building cabinets out of thick MDF rather than thinnish ply) and placing the B139s into their own cabinets (e.g. the huge "Coffin"). However, I am not at all convinced that I could get such a scheme past my partner who already complains that we have far too many huge unsightly speakers, amplifiers, tuners, turntables, vinyl, CD and wires scattered around the house. Replacing a pair of four foot high "boxes" with three foot high ones might actually gain me brownie points.
Fair comments (probably; I am definitely not qualified to comment).
I guess that I could forget about the 4001Gs, move the B110s to the side and put the T27s beside them in the same space, having the cabinets as mirror images of one another?
The IMF TLS80s are a wee bit like this.
Why would you compromise the cabinet by doing that?
It is a good idea doing the mid/top in smaller separate cabinets. The B110/B139 support a lower XO than typically used (would be best to do a Line Level XO and biamp)
dave
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