Many years ago I constructed a version of the P Atkinson Mini-Line Tranasmission Line speakers, using a T27 and B110 with a WilmsIow Audio crossover, which I regret getting rid of. I am now experimenting with making mini transmission line using a T27 and a B110 in a sealed compartment, with a second B110 in a separate compartment feeding a 1/4 wave length transmission line. For this I am using a Falcon 33Mc crossover, which I purchased for Concertos, which was unused in the end.
The spekers so far sound great in the mid and base regions, but are uncomfortably shrill at the very top end, and I am therefore looking at what changes could be to the crossovers. I also have several DN12 crossovers, and there are two versions with different phase configurations for the B110 !!
I had previosly contacted Falcon to query the phase arrangement on the 33MC and they replied that the B110 should definately be out of phse. However, before I start adjusting crossovers, I wondered what DiyAudio members thought was the correct phasing on the DN12 crossover.
I do not have test equipment and so have to do everything by ear, which is not helped by the aging process of my hearing.
Any help much appreciated
The spekers so far sound great in the mid and base regions, but are uncomfortably shrill at the very top end, and I am therefore looking at what changes could be to the crossovers. I also have several DN12 crossovers, and there are two versions with different phase configurations for the B110 !!
I had previosly contacted Falcon to query the phase arrangement on the 33MC and they replied that the B110 should definately be out of phse. However, before I start adjusting crossovers, I wondered what DiyAudio members thought was the correct phasing on the DN12 crossover.
I do not have test equipment and so have to do everything by ear, which is not helped by the aging process of my hearing.
Any help much appreciated
Please see attached the two different versions of the concerto Sp1004 DN12, with the B110 in phase in one and out of phase in the other, and a picture of my version of the Mini Transmission Line under testing before altering the x-over and completing the aesthetics.
The DN12 XO will not be good mid to bottom, a B110 is not a B139.
The aB version of the XO for the T27 also helps out.
I would look to a completely different design, one that uses both B110 in the lowest frequencies, either a 2.5 way or 2-way system. Modern TL desig is much better than teh guess and try method used to design the miniTL.
In the day i did build an MTM B110/T27 that i really liked.
from the factory data i have there are 2 different DN12 XOs, an SP1002, and an SP1004. Both flip the B110 phase.
dave
The aB version of the XO for the T27 also helps out.
I would look to a completely different design, one that uses both B110 in the lowest frequencies, either a 2.5 way or 2-way system. Modern TL desig is much better than teh guess and try method used to design the miniTL.
In the day i did build an MTM B110/T27 that i really liked.
from the factory data i have there are 2 different DN12 XOs, an SP1002, and an SP1004. Both flip the B110 phase.
dave
If you want to reduce T27 output without affecting crossover phase to to the B110 mid insert series resistor before the first tweeter cap. I.e at the start of the tweeter circuit.
If you add an lpad this will change phase
If you add an lpad this will change phase
Thank you Planet10, I apprecite what you say about not going the guess-and-try method, but my approach was to use the a similar volume for the B110/T27 compartment as used in the Concertos, so that the HF/Mid element of the crossover via either the 33Mc or the DN12 should work as well as they ever did in the Concertos. The main guess-and-try element of the crossover design is then reduced to just the B110 Mid to B110 Transmission Line section, which I hoped to be able to deal with by experimatation. In the end, it was the Mid to TL section that sounded very good indeed - pure luck for me there. The High to Mid section turns out to be the main problem, using the 33Mc, which I was not expecting as it worked well in the Concertos - I'm obviously missing something beyond my present (limited) understanding. So to sort out the harshness in the upper frequencies, I am looking to use the Kef CS1 crossover's Low Pass section with its Parallel Cap/Coil/Resistor upper response adjustment and parallel Coil/Resistor equalising response stages for the Mid B110, introducing an 82ohm parallel to the T27's 0.18mH coil to tackle ringing. As the Mid to Transmission Line section worked so well, I will utilise the same caps and coils that are presently in the 33Mc, but expect to make other adjustments as needed. I'm retired and so need something to keep the grey cells active.
Thank you also for the two DN12 schematics. It still leaves the mystery as to why Kef produced the in-phase version ? When I have made my alterations and additions to the
Thanks also Dave, I will try as you suggest if the 82ohm resistor parallel to the 0.18 coil does not do the job. Presumably an Ipad instead of a resistor would keep the inductance steady, but I did not realise the it would reverse the phase . If I go this route would I be correct in assuming that the T27 and Mid would be set up in-phase and the B110 in the Transmission line would be out of phase ?
Many thanks again.
nd Dave Bullet. I appreciate
Thank you also for the two DN12 schematics. It still leaves the mystery as to why Kef produced the in-phase version ? When I have made my alterations and additions to the
Thanks also Dave, I will try as you suggest if the 82ohm resistor parallel to the 0.18 coil does not do the job. Presumably an Ipad instead of a resistor would keep the inductance steady, but I did not realise the it would reverse the phase . If I go this route would I be correct in assuming that the T27 and Mid would be set up in-phase and the B110 in the Transmission line would be out of phase ?
Many thanks again.
nd Dave Bullet. I appreciate
I was wrong sorry. I should check my facts before I post 🙂
Adding any resistance to the tweeter (series before crossover, or L Pad after crossover and before tweeter) will change the phase relationship, therefore crossover summing with the mid.
If you add an LPad, you can vary the parallel leg to uniformily raise or lower SPL without impacting phase.
Again, I'd load this into a crossover simulator (e.g. VituixCAD) and see the phase changes.
Adding any resistance to the tweeter (series before crossover, or L Pad after crossover and before tweeter) will change the phase relationship, therefore crossover summing with the mid.
If you add an LPad, you can vary the parallel leg to uniformily raise or lower SPL without impacting phase.
Again, I'd load this into a crossover simulator (e.g. VituixCAD) and see the phase changes.
It works. How well is questionable.
I’d look to a DN13 XO for the B110+T27 with the butterworth mod or something better (lots of examples)
Then i would series wire the B110s and put a big shunt cap across one of the drivers to roll of its top, and have both B110s in an enclosure for 2 x B110. Likely an MLTL.
dave
Thanks planet10. That's a very interesting alternative that I will look at if (when ?) the current project fails!. The first problem I see with it for me is that my B110 pairs are different generations and so I would not want un-matched drivers covering the same frequencies in the same enclosure. I my current project I have one generation in the Mid and the other in the TL. I see that the DN13 is the Chorale crossover for the T27/B200 (not sure which version) . I'm not sure what other changes the DN13 crossover would need to swap the B200s for two B110s in series, but I am always willing to learn (experiment). I never thought that the two B200's that worked that well in parallel in my Concord 3s, but that may have been due to other factors. I still have the crossovers (SP1112) and 15ohm drivers from the Concords that I was once considering using in an isobarik configuration. I'll probably move them on to someone who will make better use of them soon.
Thank you also Dave, for clarifying the phasing adjustment when using a LPad. That will be very useful.
All your advice and opinions is greatly appreciated.
Thank you also Dave, for clarifying the phasing adjustment when using a LPad. That will be very useful.
All your advice and opinions is greatly appreciated.
There are quite a few SP variations. One of them is for B110/T27. I sold lots of them. I can’t quickly turn up my blue KEF binder to dig out the exact one.
dave
Many thanks for the offer, but no need for now. I will proceed with an iterative approach and deal with the 'ringing' of the upper frequencies first, starting by adding a 0.6uF cap plus 8.2ohm resistor in // behind the T27 to the 33Mc. Then if that does not work I will follow the design used in the BBC LS3/5a for further tailoring the T27, using a Wilmslow Audio 2-way crossover produced for the T27/B110 drive units that I'm using in the HF/Mid section, which can be easily adapted. I will apply the extra elements in stages until I am satisfied (or devastated !), and then turn my attention to the B110/B110TL stage using the DN12/Falcon XO approach to start with (which sounds very good to me at present). I know that it will take some sucking-and-seeing to get it all right, but that's where the fun is for me. Although the cabinet alterations are 99% complete I'm only in the early stages of getting the XO sorted.
Later on I might start a new thread dealing with the B110/B110TL section and wait for the ricochet !!!
Later on I might start a new thread dealing with the B110/B110TL section and wait for the ricochet !!!
Hi @Mogster44 , how did the project proceed?
lovely project, looks nice even in the "project" shape.
In my rebuild of the KEF Concerto crossover with an aB circuit it turned out that the midrange (B110 SP1003) was a big problem. It sounded just horrible with the standard DN12 SP1004 crossover. The bad sound might mistakenly be taken as coming from the tweeter, but is from the midrange. I did a lot to tame down the B110. I found that also the Cantata (with the SP1057) suffers from that and I have not yet found the solution (see my thread here about Cantata tweeters sounding dull).
The Falcon 33Mc has not the right aB section, it is a simplified one. I'd suggest to use the full one as per my schematics in this post: https://www.diyaudio.com/community/...th-full-ab-circuit.370666/page-2#post-7495361
Maybe also the changes I did to the B110 SP1003 circuit might help.
Also the "bass" B110 The SP1057 might need some notch/equalisation; what about using the bass section of the DN23 (CS1) crossover (probably more or less the same as in the Ref 101) but with a higher value for L2, so higher rolloff (sorry for bad pic quality)? But if if the bass unit is crossed over low (really low, like 250 Hz max) and steep, this might not be a problem.
lovely project, looks nice even in the "project" shape.
In my rebuild of the KEF Concerto crossover with an aB circuit it turned out that the midrange (B110 SP1003) was a big problem. It sounded just horrible with the standard DN12 SP1004 crossover. The bad sound might mistakenly be taken as coming from the tweeter, but is from the midrange. I did a lot to tame down the B110. I found that also the Cantata (with the SP1057) suffers from that and I have not yet found the solution (see my thread here about Cantata tweeters sounding dull).
The Falcon 33Mc has not the right aB section, it is a simplified one. I'd suggest to use the full one as per my schematics in this post: https://www.diyaudio.com/community/...th-full-ab-circuit.370666/page-2#post-7495361
Maybe also the changes I did to the B110 SP1003 circuit might help.
Also the "bass" B110 The SP1057 might need some notch/equalisation; what about using the bass section of the DN23 (CS1) crossover (probably more or less the same as in the Ref 101) but with a higher value for L2, so higher rolloff (sorry for bad pic quality)? But if if the bass unit is crossed over low (really low, like 250 Hz max) and steep, this might not be a problem.
Hi Eschenborn,
The project has gone very well. I used an adapted version of the CS1 crossover for the High/Mid band section. I decided that the T27 sectiion needed some attention and so adopted two parts of the BBC LS3/5a design that deal with the T27 being a little shrill and ringing, as follows:
1. I used a 0.6uF capacitor in series with a 8.2 Ohm resistor, parallel with the T27 to adjust the frequency response at the upper end, and
2. I used a 82 Ohm resistor in parallel with the 0.18mH coil (L3), to reduce 'ringing'.
The purpous of using a second B110 to drive the Low frequencies was to free up the strain on the Mid band B110. As the Mid to Low band section links two identical drivers, this simplified that section of the crossover. For this part of the crossover I therefore used the same coil and cap values used in the DN12 for cutting the low frequencies from the mid section (400Hz) , and reversed them for the Mid/High cut to the second B110.
The speakers have now lost the shrillness and ringing I had from the Fallcon crossover, without loseing the beautiful detail and character that the T27 has, and now has a very nice bass extension, without booming.
The project has gone very well. I used an adapted version of the CS1 crossover for the High/Mid band section. I decided that the T27 sectiion needed some attention and so adopted two parts of the BBC LS3/5a design that deal with the T27 being a little shrill and ringing, as follows:
1. I used a 0.6uF capacitor in series with a 8.2 Ohm resistor, parallel with the T27 to adjust the frequency response at the upper end, and
2. I used a 82 Ohm resistor in parallel with the 0.18mH coil (L3), to reduce 'ringing'.
The purpous of using a second B110 to drive the Low frequencies was to free up the strain on the Mid band B110. As the Mid to Low band section links two identical drivers, this simplified that section of the crossover. For this part of the crossover I therefore used the same coil and cap values used in the DN12 for cutting the low frequencies from the mid section (400Hz) , and reversed them for the Mid/High cut to the second B110.
The speakers have now lost the shrillness and ringing I had from the Fallcon crossover, without loseing the beautiful detail and character that the T27 has, and now has a very nice bass extension, without booming.
Thank you @Mogster44 , this is lovely! I am happy that you got this great result. I'd love to hear those speakers. Would it be possible to post the schematics of the crossovers as they now result here? I imagine they'd also be an alternative for the Concertos... which are neither good with the factory DN12 crossover nor – obviously, and according to my attempts to recreate it – with the Falcon 33c crossover.
I tried to sketch the circuit you describe... did I get it right? Would be interesting to try in a Concerto.
The missing parallel resistor value in the Tweeter section should be 82 Ohms.
The missing parallel resistor value in the Tweeter section should be 82 Ohms.