Ditton 15: Electronic Crossover
OK, so I got brave and pulled the crossover out the back... There are two coils... the large one has "732" written on it and the one large capacitor has a rating of 12uf... If I understand this correctly, this means that I have a crossover of somewhere between 16 and 1800 hz... since 1800 is the lowest my new tweeter can go, then if I want it to kick in at 2,000hz, then I need to change that capacitor to a 9.95uf and leave the coils alone?
2-Way Crossover Designer / Calculator
DittonFan
OK, so I got brave and pulled the crossover out the back... There are two coils... the large one has "732" written on it and the one large capacitor has a rating of 12uf... If I understand this correctly, this means that I have a crossover of somewhere between 16 and 1800 hz... since 1800 is the lowest my new tweeter can go, then if I want it to kick in at 2,000hz, then I need to change that capacitor to a 9.95uf and leave the coils alone?
2-Way Crossover Designer / Calculator
DittonFan
HeeHee, Brave is actually just what you do with old speakers. Have 'em in bits and check it all out. 
Presumably first order slope coil on the woofer and second order 12uF capacitor and coil on the tweeter. You're right it's crossing over quite low, maybe 1800Hz.
The Morel CAT 298/MDT 29 isn't going to like that too much and you'll lose some maximum power headroom. The old 12uF is probably due to be replaced by now with a new 50V electrolytic non-polar. This monacor HT-22/8 might be a good replacement too:
HT-22/8
Some good info on the CAT 298 here at Eltim:
ELTIM CA 620
Also a look at modelling 1800Hz 10uF first order crossover for a typical dome tweeter using 10W wirewound resistors:
http://www.diyaudio.com/forums/multi-way/206843-sreten-speakerman-go-series-xos-57.html#post3047689
Presumably first order slope coil on the woofer and second order 12uF capacitor and coil on the tweeter. You're right it's crossing over quite low, maybe 1800Hz.
The Morel CAT 298/MDT 29 isn't going to like that too much and you'll lose some maximum power headroom. The old 12uF is probably due to be replaced by now with a new 50V electrolytic non-polar. This monacor HT-22/8 might be a good replacement too:
HT-22/8
Some good info on the CAT 298 here at Eltim:
ELTIM CA 620
Also a look at modelling 1800Hz 10uF first order crossover for a typical dome tweeter using 10W wirewound resistors:
http://www.diyaudio.com/forums/multi-way/206843-sreten-speakerman-go-series-xos-57.html#post3047689
Ditton 15: Electronic Crossover
I have a midrange in a home-made 3-way system (5") that is similar to the HT-88s. In fact, I ordered a new pair at the same time I bought the Morels because the the paper finally tore on one of them from child-abuse (ah, the joys of parenting... the child was not abused but the speaker was). Cheapest midrange out there and yet it was/is the best-sounding. Looks like I'll be ok with a 10 uf capacitor ...2,000 hz... providing that coil is keeping the woofer at 2400hz, then I imagine the 400hz overlap is a good thing? Or should I run two caps in parallel to bring it closer to the 2400hz?
DittonFan
I have a midrange in a home-made 3-way system (5") that is similar to the HT-88s. In fact, I ordered a new pair at the same time I bought the Morels because the the paper finally tore on one of them from child-abuse (ah, the joys of parenting... the child was not abused but the speaker was). Cheapest midrange out there and yet it was/is the best-sounding. Looks like I'll be ok with a 10 uf capacitor ...2,000 hz... providing that coil is keeping the woofer at 2400hz, then I imagine the 400hz overlap is a good thing? Or should I run two caps in parallel to bring it closer to the 2400hz?
DittonFan
Ditton 15: Electronic Crossover
Went to see a speaker driver expert. He sells refurbished speakers and drivers. He pointed out that although we do not know the actual value of the second coil ("733" stamped on it's collar) it was similar in size and stature to the 6.8mH coil that he was selling... combined with that coil, he calculated that a 6.8uF capacitor would give me the 2400hz cross-over that I needed... a big stretch from the 12uF capacitor that was found in my speaker! We then reasoned that since my coil might have a slightly higher value, that Celestion may have used whatever was handy in the heat of mass production and that since I probably would not notice the difference between 12 and 10uF, it would be a good safe bet to go ahead and use an 8uF capacitor... some times logic and science DO conflict! We also took into consideration that Morels might not consider the original planned change to be enough of an accomodation ... so I'm banking that a resulting (hoped-for) output of somewhere between 2400 and 3000hz will create the ideal sound (collectively) from both speakers. Overall gain should drop slightly with the 4uF change and the in-bred 89db sensitively of the Morel MDT29s. On the negative side, I could be full-of-it and be out 20 dollars for the capacitors. The unknown variable: the actual value of that 2nd, smaller coil... the other fly-in-the-ointment is that the coils are mounted parallel to each other, as opposed to at right angles or at least, beside each other... this too, apparently, can effect the performance of the coils....aaaarrrrrggghhh! It just gets better!
DittonFan
Went to see a speaker driver expert. He sells refurbished speakers and drivers. He pointed out that although we do not know the actual value of the second coil ("733" stamped on it's collar) it was similar in size and stature to the 6.8mH coil that he was selling... combined with that coil, he calculated that a 6.8uF capacitor would give me the 2400hz cross-over that I needed... a big stretch from the 12uF capacitor that was found in my speaker! We then reasoned that since my coil might have a slightly higher value, that Celestion may have used whatever was handy in the heat of mass production and that since I probably would not notice the difference between 12 and 10uF, it would be a good safe bet to go ahead and use an 8uF capacitor... some times logic and science DO conflict! We also took into consideration that Morels might not consider the original planned change to be enough of an accomodation ... so I'm banking that a resulting (hoped-for) output of somewhere between 2400 and 3000hz will create the ideal sound (collectively) from both speakers. Overall gain should drop slightly with the 4uF change and the in-bred 89db sensitively of the Morel MDT29s. On the negative side, I could be full-of-it and be out 20 dollars for the capacitors. The unknown variable: the actual value of that 2nd, smaller coil... the other fly-in-the-ointment is that the coils are mounted parallel to each other, as opposed to at right angles or at least, beside each other... this too, apparently, can effect the performance of the coils....aaaarrrrrggghhh! It just gets better!
DittonFan
Hi, went to the local charity shop yesterday and got two pairs of Celestion 15' they are the older ones not the xr's.
Both pairs work fine, can I mod these together to try to improve them? I was thinking of fitting one of the speakers into where the ABR is, effectively making it a 3way like the ditton 33. Is it worth it or should I restore as in and just update the internals, crossover etc?
Any thoughts appreciated!
Both pairs work fine, can I mod these together to try to improve them? I was thinking of fitting one of the speakers into where the ABR is, effectively making it a 3way like the ditton 33. Is it worth it or should I restore as in and just update the internals, crossover etc?
Any thoughts appreciated!
Hi, is there anybody out there who can help me? I have recently restored a pair of 15's, new binding posts etc, replacing the original 12uf 50v crossover capacitors like for like ( they were 41 years old! ), the difference was remarkable. Deciding to go a step further i replaced the hf1300 tweeters with Morel Cat 298 ( 94mm version fits the rebate perfectly, just a bit of shaving for the magnet ) however although more detailed they do sound somewhat "bright" to say the least. I have heard that by replacing the 12uf cap with a 8uf may solve the problem?
Idea's anybody.
Idea's anybody.
I think that what you are running into here, Louis, is the Ditton 15 used the Celestion HF 1300 Tweeter, and the later 15XR used a more regular soft dome.
The Ferrofluid Morel CAT 298 soft dome is a good replacement for most of the old tweeters, being available in 94mm, which can help.
BUT, the HF 1300 crossed over much lower than regular soft domes. Maybe 1800Hz as opposed to the sort of 3.5kHz that would suit the Morel better.
So the 15XR had a different crossover. 4.7uF rather than 12uF in the treble section. I can't comment on coil values unless you measure them.
This is a very simple filter, and really not the last word in refinement. What you need to do is get a capacitor around 4.7uF on the treble section, then fit an attenuator to get level right. Say 7W wirewound or ceramic resistors.
Typical values:
1R/22R for 1dB.
2.2R/15R for 2dB.
3.3R/10R for 3dB.
41 year old bass units often sag and rub, sounding harsh, and turning them 90 degrees can help.
I include the sort of filter that I employ myself in this situation. A bit more sophisticated.
The Ferrofluid Morel CAT 298 soft dome is a good replacement for most of the old tweeters, being available in 94mm, which can help.
BUT, the HF 1300 crossed over much lower than regular soft domes. Maybe 1800Hz as opposed to the sort of 3.5kHz that would suit the Morel better.
So the 15XR had a different crossover. 4.7uF rather than 12uF in the treble section. I can't comment on coil values unless you measure them.
This is a very simple filter, and really not the last word in refinement. What you need to do is get a capacitor around 4.7uF on the treble section, then fit an attenuator to get level right. Say 7W wirewound or ceramic resistors.
Typical values:
1R/22R for 1dB.
2.2R/15R for 2dB.
3.3R/10R for 3dB.
41 year old bass units often sag and rub, sounding harsh, and turning them 90 degrees can help.
I include the sort of filter that I employ myself in this situation. A bit more sophisticated.
Attachments
. I have checked with my local branch of Maplins for the wirewound resistor, they have a few versions of the 7w at varying ohm ratings, which would you say would be the most suitable?
Ditton Dilemna
It's been over a year since I switched out my tweeters for the Morels and after changing the capacitors and redoing the internal wiring the brightness was overwhelming! I never got 'round to installing my resistors. Instead, I plugged in the little mic that came with my newsed DENON reciever and let it calibrate the remaining equing for me... it even detected one of my speakers as being wired out of phase!
When I rewired, the "pipe" sound disappeared. I redid the EQ sampling test with the mic. My DENON 688 detected the Celestions as a large speaker and crossed the signals over at 40hz. The end result was quite pleasing, without the over-bearing mid-highs.... they blended in seamlessly with the woofers; without the resistors! My only regret is that I wish there was a way to tell the DENON to cross over at 20Hz instead... setup right, ya just don't need sub-woofers with these puppies!
DittonFan
It's been over a year since I switched out my tweeters for the Morels and after changing the capacitors and redoing the internal wiring the brightness was overwhelming! I never got 'round to installing my resistors. Instead, I plugged in the little mic that came with my newsed DENON reciever and let it calibrate the remaining equing for me... it even detected one of my speakers as being wired out of phase!
When I rewired, the "pipe" sound disappeared. I redid the EQ sampling test with the mic. My DENON 688 detected the Celestions as a large speaker and crossed the signals over at 40hz. The end result was quite pleasing, without the over-bearing mid-highs.... they blended in seamlessly with the woofers; without the resistors! My only regret is that I wish there was a way to tell the DENON to cross over at 20Hz instead... setup right, ya just don't need sub-woofers with these puppies!
DittonFan
OK, been to see a guy locally yesterday who is selling a pair of 15XR. Some years ago this chap used to ran a second hand Hi-Fi shop and after closing it down apparently he had theses in dry storage and now have decided to sell them on.
Have to say they are in nice condition for the age only with a few small bruises here and there. The biggest fault would be a cracked grill on one of the speakers which has been stitched together with some aluminium plates and actually cannot be seen from the front so not a big deal really.
The guy had them hooked up to Rotel RA 921 amp and i listened a few different tracks from a CD and have to say i quite liked what i've heard. Music was a bit of mix and i had a go at Classical, Jazz & Pop.
It's the 1st time i actually encountered these speakers and quite liked the sound. The lower end wasn't really jumping at me but yet it sounded somehow good but what i really liked is the high end on these speakers and them tweeters were really selling them to me.
The guy explained that the speakers are not really suitable for bass heavy dance music and are best to be used for more relaxed genres like Classical, Jazz, ect and my understanding from what he said is that a bass heavy stuff is not mechanically healthy for these speakers.
I just would like to get some second opinions on these as no doubt there are some old owners around on these forums.
I like to listen to a variety genres of music, i like House music a lot but also listen to stuff like Pop, Jazz, Classical, Rock, Reggae, well basically a little bit of everything. He is asking £79 for them.
My ultimate question probably would be: are they worth the asking?
Have to say they are in nice condition for the age only with a few small bruises here and there. The biggest fault would be a cracked grill on one of the speakers which has been stitched together with some aluminium plates and actually cannot be seen from the front so not a big deal really.
The guy had them hooked up to Rotel RA 921 amp and i listened a few different tracks from a CD and have to say i quite liked what i've heard. Music was a bit of mix and i had a go at Classical, Jazz & Pop.
It's the 1st time i actually encountered these speakers and quite liked the sound. The lower end wasn't really jumping at me but yet it sounded somehow good but what i really liked is the high end on these speakers and them tweeters were really selling them to me.
The guy explained that the speakers are not really suitable for bass heavy dance music and are best to be used for more relaxed genres like Classical, Jazz, ect and my understanding from what he said is that a bass heavy stuff is not mechanically healthy for these speakers.
I just would like to get some second opinions on these as no doubt there are some old owners around on these forums.
I like to listen to a variety genres of music, i like House music a lot but also listen to stuff like Pop, Jazz, Classical, Rock, Reggae, well basically a little bit of everything. He is asking £79 for them.
My ultimate question probably would be: are they worth the asking?
Attachments
Last edited:
ditton xr
Hi, looking at your photo's i would say yes they are worth the asking price given what you see on ebay for more than that, so they are worth a punt.
If you are interested in improving them there are a few relatively straight forward things you can do to improve the sound: Firstly replace those nasty little brass terminals with something better, secondly replace the internal door bell type wire ( i used cat 5 ), the 4.7uf crossover capacitor must be the best part of 40 years old replace it with a modern electrolytic cap of the same value. I did all three of these things on the standard 15's and was amazed at the improvement in the sound.
Good luck.
Hi, looking at your photo's i would say yes they are worth the asking price given what you see on ebay for more than that, so they are worth a punt.
If you are interested in improving them there are a few relatively straight forward things you can do to improve the sound: Firstly replace those nasty little brass terminals with something better, secondly replace the internal door bell type wire ( i used cat 5 ), the 4.7uf crossover capacitor must be the best part of 40 years old replace it with a modern electrolytic cap of the same value. I did all three of these things on the standard 15's and was amazed at the improvement in the sound.
Good luck.
I was so close to commit buying these but then someone elsewhere pointed something out... Look at the 8" drivers in the pic i attached to my previous post and then look at the version i've attached to this post. The drivers in the speakers i'm looking at aren't originals.
Taking that into consideration i could still buy them and source the original drivers separately but then again what should i be paying for them butchered ones.
Taking that into consideration i could still buy them and source the original drivers separately but then again what should i be paying for them butchered ones.
Attachments
If those are replacement bass units, they look like Maplin's own cheapie £17 8" units!
80W 8in Shielded Bass Mid Range Speaker | Maplin
Which don't look bad at all, as it goes.
The Celestion 15XR was a decent speaker, if not an exceptional one. Build quality is excellent, and you can certainly upgrade the crossover and drive units down the road. So they could be a fun buy if you get the diyaudio hobby bug.
But £80 is too much. I'd pay £50-60 for them. My local second hand shop regularly has these type of 8" two way speakers, and he never charges more than £60.
80W 8in Shielded Bass Mid Range Speaker | Maplin
Which don't look bad at all, as it goes.
The Celestion 15XR was a decent speaker, if not an exceptional one. Build quality is excellent, and you can certainly upgrade the crossover and drive units down the road. So they could be a fun buy if you get the diyaudio hobby bug.
But £80 is too much. I'd pay £50-60 for them. My local second hand shop regularly has these type of 8" two way speakers, and he never charges more than £60.
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