Hello all... there's a lot of experience and knowledge out there that I'm hoping to tap into. I've built the odd speaker before, (but have more experience with building/repairing wooden acoustic instruments than working with mdf and the like) - and I'm at the 'ideas' stage at the moment.
This is a medium-term idea with a lot of cogitation needed before commencing work in maybe 6-8 months time. If anyones got any bright ideas or comments it'd be much appreciated.
I've got 2x KEF 139 Mk2 SP6171 (the 'Racetrack' I think?) and two T15 tweeters - both from a Celeste Mk2. I inherited the speakers and the cabinets have suffered badly from damp. I grew up with this very pair of speakers, the cabinets are not really worth the work given the overall sound of the speakers - the box is too small for a B139 and it needs a mid-range.
So, call me a sentimental old fool ("you sentimental old fool!") but I'd like to use both the B139s AND and the T15s (if possible) in a TL. If the T15s are not a good idea I'll use them in something else down the line - a few people regard them with some favour I think.
The room is about 21' by 18' and 11' high. Size of cabinet is largely not relevant given the room size - the WAF measurement indicates that taller is better than broader and Black Ash is very definitely out. For these (and other not definable reasons) I like cabinet iii) the KEF B139 Triangulated TL from @planet10
I think I've narrowed down the box to one of the following (not an exhaustive list):
Variant a)
i) Atkinson SOTA (with a B110? in the mini-box inside or something else other than the B110). Matched B110s are £270 from Falcon :-(. T15 in the main box. Disadvantage - the woodwork required is crazy.
The woodwork on the following should be easier.
ii) Bailey triangle - with closed back mid? T15 in the triangle - or maybe in a separate box together with a mid?
or
iii) KEF B139 Triangulated TL @planet10. The B139 seems to be about ear-height so where's a tweeter to go with a 1300mm tall cabinet?
or iv) any other ideas
OR...
Variant b)
Cabinets as above with a single range driver (such as Alpair 5.2/3) in the Woden Babylabs 'Bloodhound' or 'Skyflash' (MA CHN70). A separate box though would rule out iii) KEF B139 Triangulated TL because of the height I suspect?
This is a medium-term idea with a lot of cogitation needed before commencing work in maybe 6-8 months time. If anyones got any bright ideas or comments it'd be much appreciated.
I've got 2x KEF 139 Mk2 SP6171 (the 'Racetrack' I think?) and two T15 tweeters - both from a Celeste Mk2. I inherited the speakers and the cabinets have suffered badly from damp. I grew up with this very pair of speakers, the cabinets are not really worth the work given the overall sound of the speakers - the box is too small for a B139 and it needs a mid-range.
So, call me a sentimental old fool ("you sentimental old fool!") but I'd like to use both the B139s AND and the T15s (if possible) in a TL. If the T15s are not a good idea I'll use them in something else down the line - a few people regard them with some favour I think.
The room is about 21' by 18' and 11' high. Size of cabinet is largely not relevant given the room size - the WAF measurement indicates that taller is better than broader and Black Ash is very definitely out. For these (and other not definable reasons) I like cabinet iii) the KEF B139 Triangulated TL from @planet10
I think I've narrowed down the box to one of the following (not an exhaustive list):
Variant a)
i) Atkinson SOTA (with a B110? in the mini-box inside or something else other than the B110). Matched B110s are £270 from Falcon :-(. T15 in the main box. Disadvantage - the woodwork required is crazy.
The woodwork on the following should be easier.
ii) Bailey triangle - with closed back mid? T15 in the triangle - or maybe in a separate box together with a mid?
or
iii) KEF B139 Triangulated TL @planet10. The B139 seems to be about ear-height so where's a tweeter to go with a 1300mm tall cabinet?
or iv) any other ideas
OR...
Variant b)
Cabinets as above with a single range driver (such as Alpair 5.2/3) in the Woden Babylabs 'Bloodhound' or 'Skyflash' (MA CHN70). A separate box though would rule out iii) KEF B139 Triangulated TL because of the height I suspect?
Of those, only the third one is a modern design. I have drawn a numnber of variations of Scott’s line.
Tweeter can go right above or right below the woofer. The issue is what and where do you put the midrange. B139 has a nasty 1kHz resonance and i would not use them above 300 Hz.
The WAW idea is the best IMO, you can buikld skinny enclosures that stick tot he sides of the bass TL.
dave
Tweeter can go right above or right below the woofer. The issue is what and where do you put the midrange. B139 has a nasty 1kHz resonance and i would not use them above 300 Hz.
The WAW idea is the best IMO, you can buikld skinny enclosures that stick tot he sides of the bass TL.
dave
Thankyou kindly 🙂 Regarding XO I was thinking in the area of 300 Hz for the reason you stated. For midrange are there any suitable closed units for this TL design - other than the B110 which will, I've read on here, require its own enclosure.
WAW? Still learning acronyms here! Woofer Assisted Wideband? Does that refer to a full-range in partnership with a dedicated woofer? Please excuse my ignorance - I'm a fast learner but starting from a Briggs book read more years ago than I care to remember! This would mean extending the width of your design by 150mm or so - and designing a miniTL for that extension?
WAW? Still learning acronyms here! Woofer Assisted Wideband? Does that refer to a full-range in partnership with a dedicated woofer? Please excuse my ignorance - I'm a fast learner but starting from a Briggs book read more years ago than I care to remember! This would mean extending the width of your design by 150mm or so - and designing a miniTL for that extension?
Yes.
You don’t see many decent closed back mids these days. In the days of IMF/SOTA/Pro9 et all era, the Peerless K040 was common. It was probably less coloured (coated paper), didn’t go as low, or use as much volume with it’s can than the B110 in whatever.
The volum eis the issue, you don’t want to give up a whole lot of volume in the TL. Whenever i think of B110, i think 5” pipe out the back, too much impingement. But with the A5.2/3/CHN-50 that volume can be much smaller.
Sealed, or even a midTL could be fit in. Perhaps a double baffle and the use of the pointy end of the partition as part of the midenclosure. Or an xrk dagger-like shapeOr you can just hang a little box off the sides. With a full-on enclosure for the 3”, you could play with WAW (XO at 300 is just about perfect), or movve the XO down towards Satelitte + helper subs approach — woofers can be placed more optimally for even bass response.
An active XO makes things a lot easier — i leave desgning passive XOs to others. Even having something like a cheap miniDSP to dial in the right transfer functions and then translate to either passive XO or analog active (or hybrid). As the XO goes lower passive becomes more difficult to design (you are getting too close to the LF impedance peak of both the woofer & the midTweeter at resonance), and the parts become much bigger & pricier… If you know what parts are needed and avoid ending up with bunch of spare parts from experimenting to get it right, the cost of the spare parts could well be enuff to pay for the amp & XO just to play with.
And to quote @chrisb, how many of us don’t already have a spare amp in the closet.
The T15 could be trialed as an ambiance tweeter, firing upwards or to the side.
dave
B139 was used as the basis for most of the early TL experiments so a good choice for the above recommendations.
But the classic box for it is a large ported cabinet. The correct tuning is the original KEF Concerto. You could do a tall box of the same volume and tuning which IIRC was 35 or 40Hz.
You could use your original Celeste II xovers but replace all the Non Polarized Electrolytics. Make sure you mount the T15 s as in the original cutout. A extra midrange unit might give better results IF you design a proper xover for it and the other units. I regard DSP solutions as Black Magic as passive xovers especially if you can't measure frequency response accurately and conveniently.
Get the B139 as close to the T15 as possible. The T15 at about 0.9m ear height and the B139 vertical
Was there a partial plate in front of the B139s in your Celeste II ? Sorta like a phasing plug in front of a treble unit?
But the classic box for it is a large ported cabinet. The correct tuning is the original KEF Concerto. You could do a tall box of the same volume and tuning which IIRC was 35 or 40Hz.
You could use your original Celeste II xovers but replace all the Non Polarized Electrolytics. Make sure you mount the T15 s as in the original cutout. A extra midrange unit might give better results IF you design a proper xover for it and the other units. I regard DSP solutions as Black Magic as passive xovers especially if you can't measure frequency response accurately and conveniently.
Get the B139 as close to the T15 as possible. The T15 at about 0.9m ear height and the B139 vertical
Was there a partial plate in front of the B139s in your Celeste II ? Sorta like a phasing plug in front of a treble unit?
Last edited:
Thankyou for the suggestion. I did indeed think about that (the data sheet suggests a ported box of 62 litres with 3 drivers with the B139 crossing over at 400) - however I think it'd need a mid and the B110 (the classic combo) is £270 for a new matched pair - and that's a tad too much for an experiment. The original idea was just to recap (along with the various Dittons and others in the queue) - until I saw the state of the cabinets.
Also...there's an itch that needs scratching. Many years ago I pointed to the Celestes , picked up one of Dads hifi mags and showed him a picture of a Bailey TL with the request that he build one. He pointed out that the piano was in the way of anything larger than the Celestes. However I know he thought about it as I caught him soon after at a timber merchants closely examining plywood! So my interest in TLs and horns kind of adds to his interest all those years ago.
Having said all that even I'm capable of designing a reflex or IB cabinet so it's something I've not discounted entirely - even possibly swapping drivers over to compare - or sourcing some extra and older B139s. There's an addiction to large teak boxes here!
Regarding the plate - I believe this was done to the Concerto? (that's a speaker I've not heard) There's nothing like that on these K2s. I tend to share your views on DSP - although an analogue active XO (such as Rod Eliiot has designed) is ok with me. Testing and frequency measurement I can do in a largish field that has no obstacles to reflect sound- it'll amuse the sheep although the little buggers might want to have a nibble at the speakers - they're quite tame and very curious.
Please bear with me on this as I'm not so well informed as others!
You're suggesting, essentially, either:
a) use a small enclosure inside your TL design. I note that the graph you posted for the A5.3 has a box volume of 1.7L - so I guess losing that from 138 L (your design) is not so much a problem? Am I right in thinking that you specified such a small enclosure as a means of limiting the response below 200 Hz (ish) - so the enclosure acts as a kind of 'acoustic' XO or filter? Or is my grasp gibberish?!!
or
b) Piggybacking a larger enclosure on the side around ear height - more or less the same height as the B139. Scott's 'Bloodhound' Baby TL is 6 L - and that's too much to lose from the 138 L? There's also an issue with it looking very odd (unless the entire cabinet is extended width ways by 140mm) but gives the advantage of being able to play with the XO frequency to a greater extent than option a).
Is that a fair summary? Choices... hmm. I think I'll get out OpenOffice draw and see if it'll do 3D representations of a side-loaded cabinet.
Last edited by a moderator:
Fair summary.
The sealed box is to minimize volume. It does roll off th ebottom and one does have the option of using that as a 2nd order high pass filter. It limits you tothat frequency — 133.6 Hz in this case (you want a max flat enclosure which is the one with Q = 0,707
dave
The sealed box is to minimize volume. It does roll off th ebottom and one does have the option of using that as a 2nd order high pass filter. It limits you tothat frequency — 133.6 Hz in this case (you want a max flat enclosure which is the one with Q = 0,707
dave
If you are looking at a large transmission line from the 70s there is a Cambridge Audio R40 (B139, B110, T27) and an R50 (B139, B110, T27, STC 4001G) on ebay at the moment with asking prices of £264 and £325 respectively. A project with old KEF drivers is not worth spending much money on because the drivers offer only a modest performance by modern standards. The B139s are likely worth using in a new project (as woofers rather than midwoofers) because large reasonable woofers are expensive. The T15 is from the 60s and unlikely to be worth using in a new project given how much tweeters have improved since then and the modest price for modern tweeters.
When I lived in Tavistock I had some unwanted B110, T27 and 4001G in a draw from an old pair of scrapped 70s DIY transmission line speakers. I have just checked but they didn't come with me when I moved (nor did the draw they were in). If you ask/look around you may well find some old KEF drivers for free or little money to complete a project. Or buy and break some old speakers from ebay like the R40s or R50s.
The R50 was essentially the Pro9TL (1st version, there are 2)
http://p10hifi.net/TLS/downloads/Pro9TL-1.pdf
http://p10hifi.net/TLS/downloads/Pro9TL-Mk2.pdf
dave
The second one looks a possibility for the OP if he opts for a modern mid and tweeter with his KEF woofer in a 70s transmission line. A modern £30 SB Acoustics tweeter (or equivalent from SEAS or similar) should comfortably outperform a T27+4001G or T15 as should a £50 SB Acoustics mid/midwoofer (or equivalent) out perform a B110. It would require designing a crossover and choosing drivers with suitable parameters which the OP may not want to do. It may also not fit in with a retro transmission line speaker and/or KEF drivers.
Last edited:
It's a very old B139, which is very different from the more modern versions that went into the TL boxes. The drivers are very old, they have changed and are not as new for a long time. I wouldn't plan anything until the TS parameters, impedance and FR rasponse are measured, because it's all just a guess without measurements.
KEF K2 Celeste Mk. II is the successor of the K2 Celeste introduced in 1962.
Woofer: B139 Mk. 2,
Tweeter (hemisperical diaphragm): T15 Mk. 2,
Crossover: DN8, take-over frequency 1 kHz
Impedance: 8...16 Ohms
Max. input: 15 Watts rms, 30 Watts peak
System resonance: 80 Hz
KEF K2 Celeste Mk. II is the successor of the K2 Celeste introduced in 1962.
Woofer: B139 Mk. 2,
Tweeter (hemisperical diaphragm): T15 Mk. 2,
Crossover: DN8, take-over frequency 1 kHz
Impedance: 8...16 Ohms
Max. input: 15 Watts rms, 30 Watts peak
System resonance: 80 Hz
Easier but lower performance. The spec says 85 dB sensitivity and 5W power handling? That looks a bit quiet and delicate for a big old transmission line speaker which ought to be loud and thunderous.
The OP may not actually be able to do :-( My previous experience of building speakers is decades ago with Gilbert Briggs book!
Power handling is irrelevant. The A5.3 is more like 87 dB, the factory measxures were off. and suggesting they give lower performance is a matter of opinion. No XO for a tweeter makes for a huge advantage.
What is 11 V in 96 dB out give when you scale to 2.83v? For the SP1044.
The original factory burned down and all the tooling for the one in question was lost and we ended up witht he SP1044.
dave
What is 11 V in 96 dB out give when you scale to 2.83v? For the SP1044.
The original factory burned down and all the tooling for the one in question was lost and we ended up witht he SP1044.
dave
I hope I'm not causing fisticuffs!
The idea, essentially, was to use the B139s (and preferably the T15s so nothing is wasted) from a knackered pair of Celeste K2s - speakers that my Dad left me and that I grew up with - there's some sentimental value there. What's the best way to realise this without spending a fortune on extra drivers or XOs? - so I came up with a TL.
Dave is suggesting using the A5.3 in a separate enclosure mounted on the side - so I came up with this - basically his triangular B139 TL box and one of Scott Lindgrens Baby TLs using the A5.3 or similar. If the worst is realised - then I have a baby TL that I can use perhaps as desktop speakers - and the large TL can be used for something else. My major concern at present is whether my better half is going to like this rather odd looking speaker!
(yes, I know the depth is wrong - it ought to be the same as the width - it's my first ever excursion into creating images on a computer and it falls sort of professional standards by some distance!)
The idea, essentially, was to use the B139s (and preferably the T15s so nothing is wasted) from a knackered pair of Celeste K2s - speakers that my Dad left me and that I grew up with - there's some sentimental value there. What's the best way to realise this without spending a fortune on extra drivers or XOs? - so I came up with a TL.
Dave is suggesting using the A5.3 in a separate enclosure mounted on the side - so I came up with this - basically his triangular B139 TL box and one of Scott Lindgrens Baby TLs using the A5.3 or similar. If the worst is realised - then I have a baby TL that I can use perhaps as desktop speakers - and the large TL can be used for something else. My major concern at present is whether my better half is going to like this rather odd looking speaker!
(yes, I know the depth is wrong - it ought to be the same as the width - it's my first ever excursion into creating images on a computer and it falls sort of professional standards by some distance!)
Last edited by a moderator:
You want the midTweeter as close as possible to the woofer.
dave
dave
Find a way to measure the TS parameters of the bass unit. Then you can easily simulate the box in one of the many free simulators. As for the tweeter, I'd keep that one, and it probably needs a super tweeter. I suggest putting it in the back, like a backfire TW. As for the shape of that box, I'm very skeptical, the tweeter should be as close as possible to the bass unit, as in the original design.
https://artalabs.hr/AppNotes/LIMP_Tutorial_Version_2_4_English.pdf
In order to use the existing crossover, the front panel should be as similar as possible to the existing one (dimensions and arrangement of drivers), just extended downwards under the bass unit (or backwards) to increase the volume, keeping the upper part as in the original design. The crossover probably needs a capacitor replacement, and maybe everything needs to be replaced. If Qts is greater than 0.5 it is not for bass reflex. And I think it is greater. There is no data for that driver because they didn't even use TS parameters back then, it was all done by feeling and trials. TS parameters began to be used much later.
This proved to be good as a backfire tweeter. Exceptional sound for the money.
https://www.ebay.com/itm/225033916031
https://artalabs.hr/AppNotes/LIMP_Tutorial_Version_2_4_English.pdf
In order to use the existing crossover, the front panel should be as similar as possible to the existing one (dimensions and arrangement of drivers), just extended downwards under the bass unit (or backwards) to increase the volume, keeping the upper part as in the original design. The crossover probably needs a capacitor replacement, and maybe everything needs to be replaced. If Qts is greater than 0.5 it is not for bass reflex. And I think it is greater. There is no data for that driver because they didn't even use TS parameters back then, it was all done by feeling and trials. TS parameters began to be used much later.
This proved to be good as a backfire tweeter. Exceptional sound for the money.
https://www.ebay.com/itm/225033916031
Last edited: