I'm not familiar with "MkII"... the only reference I could find for "MkII" pertains to the hf-1300 tweeter, which was not used in the 66s.
Here's a list of the 66 variations--
Both my standard (blackies) and front-veneered models came with the T1600 woofer. My T2619 woofer (with a larger dust cap) was purchased later as a spare. It looks like either can be used--
(I have no idea about the "UL12" thing, except that it appears on a very early brochure. I doubt that it's something other than a T1600 !)
For the final version, the 662, all three drivers were re-designed.
Here's a list of the 66 variations--
Both my standard (blackies) and front-veneered models came with the T1600 woofer. My T2619 woofer (with a larger dust cap) was purchased later as a spare. It looks like either can be used--
(I have no idea about the "UL12" thing, except that it appears on a very early brochure. I doubt that it's something other than a T1600 !)
For the final version, the 662, all three drivers were re-designed.
The 1600 woof was in version one of the 66's. Mine are 2619's. I also not sure about UL but will search it.
SBA Attachment is pic of 1980's Ditton 66 MK 2. ABR is on the back side.
My 66's were built in Sept/77
Attachments
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moermusic, thanks for the info. I hadn't seen the series II before, but that's hardly surprising since they're so scarce and there's no brochures, specs, or published reviews. So it's believed that this model was introduced in the early 80s and followed the 662 ! Interestingly, the series II's ABR looks like it was made using leftover woofer chassis from the original 66. Perhaps that nasty recession of the early 80s put an end to the series II before it could take off. But it might be otherwise! I'm sort of curious about the midrange sound. The MF/MD mids are well-damped soft domes. The 662 mid is a hard dome... and I don't know about the series II below.
re-issued Dittons, and the Mk I and II matter
Hi sba and Doug,
in the 1980s, and maybe even later, there were issues of at least 2, and perhaps more, Celestion models with "Ditton" on them.
One is that 66 Series II you have found.
It is, as you seem to realize, not a true 66, and seems to be a reduced size 662.
The other was labelled "Ditton 88". I have never seen one, but only a photo and I forget where I saw that.
The 88 was larger than the Series II 66, if I'm remembering correctly.
What I do remember is that both were available in a few countries only,
there simply to meet a specific market demand which was different to what most UK buyers were buying then.
The final actual "Ditton" labelled model issued in the UK, and likely World-wide, was the 332 ... somewhat smaller than the 442 and 551.
There was no 552, seemingly because there had never been a 55 model.
If any readers have these, then unless they have some of the original 66 drivers in them,
please start a new Thread if you want to re-condition them,
because this thread is now very long, so lets keep it for original 66s.
As for the Mk I and Mk II matter, this I think simply is how some owners describe the two basic versions which sba has,
and which RWTomkins posted the printed information about in #162 on Page 17 - the T.B.C. and P.C.C. versions,
and as sba and at least one other owner have posted about, there are two different crossover capacitor versions of the T.B.C.
tonedef2 refered then to them as Mk I and Mk II, but neither seem to be labelled as such by Celestion,
nor were the Ditton 44s of that era even though each had a different version of the midrange cone driver.
T.B.C. seems to mean Tag Board Connected.
P.C.C. seems to mean Printed Circuit Connected.
Thankyou for the reminder about the woofer number alternates sba !
Hi sba and Doug,
in the 1980s, and maybe even later, there were issues of at least 2, and perhaps more, Celestion models with "Ditton" on them.
One is that 66 Series II you have found.
It is, as you seem to realize, not a true 66, and seems to be a reduced size 662.
The other was labelled "Ditton 88". I have never seen one, but only a photo and I forget where I saw that.
The 88 was larger than the Series II 66, if I'm remembering correctly.
What I do remember is that both were available in a few countries only,
there simply to meet a specific market demand which was different to what most UK buyers were buying then.
The final actual "Ditton" labelled model issued in the UK, and likely World-wide, was the 332 ... somewhat smaller than the 442 and 551.
There was no 552, seemingly because there had never been a 55 model.
If any readers have these, then unless they have some of the original 66 drivers in them,
please start a new Thread if you want to re-condition them,
because this thread is now very long, so lets keep it for original 66s.
As for the Mk I and Mk II matter, this I think simply is how some owners describe the two basic versions which sba has,
and which RWTomkins posted the printed information about in #162 on Page 17 - the T.B.C. and P.C.C. versions,
and as sba and at least one other owner have posted about, there are two different crossover capacitor versions of the T.B.C.
tonedef2 refered then to them as Mk I and Mk II, but neither seem to be labelled as such by Celestion,
nor were the Ditton 44s of that era even though each had a different version of the midrange cone driver.
T.B.C. seems to mean Tag Board Connected.
P.C.C. seems to mean Printed Circuit Connected.
Thankyou for the reminder about the woofer number alternates sba !
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and what to listen to ? ... plus multimeters
Hi Doug,
well if you have to move home and your children do not want your audio equipment ... but what are you going to listen to music through ?
Maybe it is good your 66s are being returned to you.
You will have to spend a lot of money to equal them,
and that cannot be achieved completely in a smaller sized loudspeaker.
About Multimeters:
First check the battery in each, because a low battery charge can cause faulty readings.
Also, meters are often inaccurate in their lowest Range for all or some of what they can measure.
If you have any of those Mills MRA-5 +/- 1% resistors spare, then use those to test both your meters,
OR, buy 2 of 10 ohm, +/- !% Tolerance metal film resistor from a local parts shop. 2 in case one is faulty.
The miniature 1/4 watt size is sufficient for testing your meters, but do buy in at least +/- 1% tolerance.
There are +/- 0.5% and +/- 0.25% Tolerance resistors available, but those are expensive and usually only available from Mail-Order suppliers.
I have to go now, but I do hope to eventually get to replying to other members current queries !
Have to eat a little crow & my girls are coming back home.
Have a spare MD5oo but 2 different meters showdifferent ohms. 2.5 vs 4.6 how to believe which?
Hi Doug,
well if you have to move home and your children do not want your audio equipment ... but what are you going to listen to music through ?
Maybe it is good your 66s are being returned to you.
You will have to spend a lot of money to equal them,
and that cannot be achieved completely in a smaller sized loudspeaker.
About Multimeters:
First check the battery in each, because a low battery charge can cause faulty readings.
Also, meters are often inaccurate in their lowest Range for all or some of what they can measure.
If you have any of those Mills MRA-5 +/- 1% resistors spare, then use those to test both your meters,
OR, buy 2 of 10 ohm, +/- !% Tolerance metal film resistor from a local parts shop. 2 in case one is faulty.
The miniature 1/4 watt size is sufficient for testing your meters, but do buy in at least +/- 1% tolerance.
There are +/- 0.5% and +/- 0.25% Tolerance resistors available, but those are expensive and usually only available from Mail-Order suppliers.
I have to go now, but I do hope to eventually get to replying to other members current queries !
Thanks Alan. Yeah, the tread has somewhat deteriated. Most everyone is *up to date*. I was going to listen to music thru my Yamaha S4115 H *PA* units. they sometimes end up on the deck, serenading cattle a mile away !
SBA: good pics, I never did find one of the back side of the now *infamous* Mk2.
SBA: good pics, I never did find one of the back side of the now *infamous* Mk2.
SPICE model of 66 crossovers - driver impedance
I'm doing a SPICE model of the crossovers to chart V across the drivers at the various frequencies and I am wondering what the appropriate impedance of the various driver should be to get a realistic result.
The actual driver impedance varies across the audible spectrum and I assume the impedance for the model should be related to frequency. Is this correct? Should the impedance be the impedance at the crossover point, DCR or something else?
I'm doing a SPICE model of the crossovers to chart V across the drivers at the various frequencies and I am wondering what the appropriate impedance of the various driver should be to get a realistic result.
The actual driver impedance varies across the audible spectrum and I assume the impedance for the model should be related to frequency. Is this correct? Should the impedance be the impedance at the crossover point, DCR or something else?
SPICE simulation of 66 xover with old and new mods
Hi Alan and anyone else interested,
After I did my, seemingly minor, modifications to the 66 crossovers by adding some resistors that resulted in a significant improvement in the sound quality I wanted to find an analytical explanation of the reasons for the improvements and perhaps explore it further.
I learnt and then used LTSpice to simulate the voltages across the drivers with both the old mods and with the new mods. I think the results of the simulations goes a long way in explaining the differences in the sound between the old and newer mods. And perhaps provides a starting point for further mods to better balance the treble.
The main question I guess is are my assumptions and methodology ok?
The results are attached.
Any comments would be more than welcome.
DG
Hi Alan and anyone else interested,
After I did my, seemingly minor, modifications to the 66 crossovers by adding some resistors that resulted in a significant improvement in the sound quality I wanted to find an analytical explanation of the reasons for the improvements and perhaps explore it further.
I learnt and then used LTSpice to simulate the voltages across the drivers with both the old mods and with the new mods. I think the results of the simulations goes a long way in explaining the differences in the sound between the old and newer mods. And perhaps provides a starting point for further mods to better balance the treble.
The main question I guess is are my assumptions and methodology ok?
The results are attached.
Any comments would be more than welcome.
DG
interim to DennyG
Hi Denny,
I haven't forgotten you !
I have no time today to comment on all your recent, but to keep you going with something to do,
remove the 82 ohm resistor from the MD installed 66,
but leave the 82 ohm in the MF installed 66.
Listen carefully to the upper mids with suitable music,
with or without female or high pitched male vocals,
both BEFORE you do the above, and AFTER.
Is the AFTER tonal balance between both 66s closer to same from each speaker than before the resistor removal ?
I will post the reason for resistor removal when I have time available,
plus about your measurements and calculations then also.
*** *** *** ***
The Spice plots are interesting, and useful if one knows how to interpret them,
but they are both a bit inaccurate because of some of the Presumptions used.
I will explain when I have time available.
Hi Denny,
I haven't forgotten you !
I have no time today to comment on all your recent, but to keep you going with something to do,
remove the 82 ohm resistor from the MD installed 66,
but leave the 82 ohm in the MF installed 66.
Listen carefully to the upper mids with suitable music,
with or without female or high pitched male vocals,
both BEFORE you do the above, and AFTER.
Is the AFTER tonal balance between both 66s closer to same from each speaker than before the resistor removal ?
I will post the reason for resistor removal when I have time available,
plus about your measurements and calculations then also.
*** *** *** ***
The Spice plots are interesting, and useful if one knows how to interpret them,
but they are both a bit inaccurate because of some of the Presumptions used.
I will explain when I have time available.
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Hi Alan,
The speaker with the MD (the RH speaker) is a bit louder than the one with the MF (the LH speaker) when listening to high pitched male vocals (countertenor).
I assume some of this due to the the imbalance in the mid of about 1db as indicated by the nearfield results in an earlier post. I've just done some farfield and onaxis experiments and they also show the MD equipped speaker (RH) is louder than the other by about 1 db from about 1kHz to 4kHz and about 6kHz to 8.5kHz.
I'll try what you suggest but shouldn't I remove the 82R in the least loud speaker ie the one with the MF rather than the louder speaker ie the one with the MD?
for Tone/Timbre
Hi DennyG,
The reason to remove 82r from Parallel with the MD is that it has significantly lower Impedance across its entire used bandwidth than the MF.
The MF when paralleled with 82r will have close to the same Impedance as the MD across its entire used bandwidth,
thus BOTH should then be seen as same from the equal components' crossovers, thus both mids should have same Tone/Timbre,
or close to same allowing for whatever internal differences between the two dome types that may affect the Tone that do not show in the current measurements.
Parallel connected resistors do not usually change the Volume level from the drivers, unless there are Series connected resistors in electrically adjacent parts of the circuit,
{or unless are a very low resistance to such degree as to affect the amplifier}.
Series connected resistors can change the Volume level regardless of whether any adjacent Parallel resistors or not.
The 6 <--> 8.5kHz region in your case may be a result of difference between the tweeters also.
I see each has a different DC resistance in your earlier post.
Let's see an Impedance versus Frequency plots for the tweeters.
We should examine Frequency SPL plots for the tweeters also,
but to do those even Nearfield with good results will require acoustic treatment of that top-of-cabinet overhang,
and a Post about that which I have been promising is going to take longer than I have time for today.
For now, roll up a pair of thick Woollen socks {preferably real wool, not synthetic} NOT too tightly or absorption will be reduced,
and secure them with double sided tape under the lip for while you measure each tweeter.
For the +1dB volume difference, move the Balance control of your amplifier a little to compensate, and then you will be able to assess the Tone/Timbre.
After we get the drivers assessed I'll try to think of a way to get equal output from each without causing one to have a different Tone to the other.
A Series connected resistor to one channel's driver only will cause it to have a different Tone to the other driver, unless very low resistance.
If the MD happens to sound more assertive in Tone than the MF, when both are heard at same volume, then a small Series connected resistor may get the MD closer tonally to the MF.
Hi DennyG,
The reason to remove 82r from Parallel with the MD is that it has significantly lower Impedance across its entire used bandwidth than the MF.
The MF when paralleled with 82r will have close to the same Impedance as the MD across its entire used bandwidth,
thus BOTH should then be seen as same from the equal components' crossovers, thus both mids should have same Tone/Timbre,
or close to same allowing for whatever internal differences between the two dome types that may affect the Tone that do not show in the current measurements.
Parallel connected resistors do not usually change the Volume level from the drivers, unless there are Series connected resistors in electrically adjacent parts of the circuit,
{or unless are a very low resistance to such degree as to affect the amplifier}.
Series connected resistors can change the Volume level regardless of whether any adjacent Parallel resistors or not.
The 6 <--> 8.5kHz region in your case may be a result of difference between the tweeters also.
I see each has a different DC resistance in your earlier post.
Let's see an Impedance versus Frequency plots for the tweeters.
We should examine Frequency SPL plots for the tweeters also,
but to do those even Nearfield with good results will require acoustic treatment of that top-of-cabinet overhang,
and a Post about that which I have been promising is going to take longer than I have time for today.
For now, roll up a pair of thick Woollen socks {preferably real wool, not synthetic} NOT too tightly or absorption will be reduced,
and secure them with double sided tape under the lip for while you measure each tweeter.
For the +1dB volume difference, move the Balance control of your amplifier a little to compensate, and then you will be able to assess the Tone/Timbre.
After we get the drivers assessed I'll try to think of a way to get equal output from each without causing one to have a different Tone to the other.
A Series connected resistor to one channel's driver only will cause it to have a different Tone to the other driver, unless very low resistance.
If the MD happens to sound more assertive in Tone than the MF, when both are heard at same volume, then a small Series connected resistor may get the MD closer tonally to the MF.
to Simon Gore
Hello Simon,
it seems you have not read all of our thread, unless you are reading it now,
and it is very long ...
I do not know how to Year date 66s from their serial numbers, however do look where moermusic advised,
AND whilst you are doing that have look at the crossovers in BOTH cabinets,
AND at the back of the mid-domes to see if are MF500 {in earliest 66}, or MD500 {in later 66s}.
In this thread on Page 5 in #47 is a photo of the PCB crossover of the final 66 model.
See the olive green capacitors in the tweeter filter's section.
On page 10 in #96 <---> #99 are photos of four variations of earlier crossovers.
All are hard wired.
See the red capacitors in the tweeter filter of the earliest 66s.
See the blue-green capacitors in the tweeter filter of the interim 66s.
The red capacitors were the best quality for sound when new, but those will now be leaky in existing 66s,
because those are almost certainly Paper-In-Oil {PIO} capacitors.
Both of the green types are not poor sound capacitors, but are not close to the best for sound quality.
Both green types will still be OK to play music through, because those are polyester film + metal foil caps,
and those do not normally deteriorate with age.
None of the other caps in any of the crossover versions are optimum for sound quality, and all will now be deteriorated to significant degree,
though the 24uF ones marked LL may not be as deteriorated as the others.
The Inductors -{the coils of wire}- in all versions are of the same quality,
and all will still be OK, {unless delibrately damaged}.
sba posted the Serial Numbers for all four of his 66s in #95 on Page 10.
If there are Dates stamped inside your cabinets, please do post those here,
along with which crossover and mid-dome types yours have.
Hello Simon,
it seems you have not read all of our thread, unless you are reading it now,
and it is very long ...
I do not know how to Year date 66s from their serial numbers, however do look where moermusic advised,
AND whilst you are doing that have look at the crossovers in BOTH cabinets,
AND at the back of the mid-domes to see if are MF500 {in earliest 66}, or MD500 {in later 66s}.
In this thread on Page 5 in #47 is a photo of the PCB crossover of the final 66 model.
See the olive green capacitors in the tweeter filter's section.
On page 10 in #96 <---> #99 are photos of four variations of earlier crossovers.
All are hard wired.
See the red capacitors in the tweeter filter of the earliest 66s.
See the blue-green capacitors in the tweeter filter of the interim 66s.
The red capacitors were the best quality for sound when new, but those will now be leaky in existing 66s,
because those are almost certainly Paper-In-Oil {PIO} capacitors.
Both of the green types are not poor sound capacitors, but are not close to the best for sound quality.
Both green types will still be OK to play music through, because those are polyester film + metal foil caps,
and those do not normally deteriorate with age.
None of the other caps in any of the crossover versions are optimum for sound quality, and all will now be deteriorated to significant degree,
though the 24uF ones marked LL may not be as deteriorated as the others.
The Inductors -{the coils of wire}- in all versions are of the same quality,
and all will still be OK, {unless delibrately damaged}.
sba posted the Serial Numbers for all four of his 66s in #95 on Page 10.
If there are Dates stamped inside your cabinets, please do post those here,
along with which crossover and mid-dome types yours have.
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to moermusic
Hi Doug,
I see you are still reading here, thus maybe you are now intending to keep your 66s, and good if you do !
If you do decide to sell again, then I recommend that you:
- remove the SEAS tweeters and install the original Celestion tweeters, because most buyers will want those.
- remove the 10uF cap from the tweeter filter and install the 6uF cap, for the crossover to work optimally for the Celestion tweeters.
- remove the 82 ohm resistors from the mids' filters, because buyer will wonder what those are there for,
and likely will want to hear the closer to the original sound without them ... at least initially.
- leave in all the other resistors, because those are necessary to get close to the original 66 sound with the new caps,
but don't put any resistor in the tweeter circuit.
- keep your SEAS tweeters and sell separately to the 66s, because there will be at least a few other potential buyers interested in those.
Alternately, you could use the SEAS tweeters, and perhaps the 10uF caps, to make a small 2-way with a 6.5" SEAS mid/bass driver
- I'll advise one if you are interested,
or even a medium sized 3-way with a new mid-dome and a 10" bass driver.
Hi Doug,
I see you are still reading here, thus maybe you are now intending to keep your 66s, and good if you do !
If you do decide to sell again, then I recommend that you:
- remove the SEAS tweeters and install the original Celestion tweeters, because most buyers will want those.
- remove the 10uF cap from the tweeter filter and install the 6uF cap, for the crossover to work optimally for the Celestion tweeters.
- remove the 82 ohm resistors from the mids' filters, because buyer will wonder what those are there for,
and likely will want to hear the closer to the original sound without them ... at least initially.
- leave in all the other resistors, because those are necessary to get close to the original 66 sound with the new caps,
but don't put any resistor in the tweeter circuit.
- keep your SEAS tweeters and sell separately to the 66s, because there will be at least a few other potential buyers interested in those.
Alternately, you could use the SEAS tweeters, and perhaps the 10uF caps, to make a small 2-way with a 6.5" SEAS mid/bass driver
- I'll advise one if you are interested,
or even a medium sized 3-way with a new mid-dome and a 10" bass driver.
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Hi Alan: Yes, my babies are going to a new home this Sun for a listen. the fellow is well aware of updated xovers to enable my aged aural caviteis to hear higher freq's. The HF 2000's are in , with all the stuff still in place for the SEAS's. I included the SEAs in the deal. He can mix & match his own self. I will give him a printed version of your above post. I would love to build a spkr, but am running out of time for *hobbies*. THANK YOU SO VERY MUCH FOR YOUR TIME AND ADVICE !
I hope/trust the originators of this thread solved their problems, as well as many others.
Before asking more generic questions, STUDY each & every page here. I will keep reading, but try to resist posting, unless it is of something factual. Have fun & good luck.
I hope/trust the originators of this thread solved their problems, as well as many others.
Before asking more generic questions, STUDY each & every page here. I will keep reading, but try to resist posting, unless it is of something factual. Have fun & good luck.
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Tone / timbre & 82R on MD500
Hi Alan,
I’ve removed the 82 ohm from the speaker with the 6.3R MD500 (RH speaker) and listened to the tracks again (solo countertenor with lute). To my surprise the voice came from the centre or very close to it and both speakers sounded the same to me ie no noticeable tone/timbre differences. Well done! It looks as though the slightly different level (ie 1 db under test) of the MD equipped speaker is of no real consequence now ie not noticeable enough to require action at this time. Will, however, listen more and evaluate in more detail with a range of material.
I also checked balance with a “Denon Audio Technical CD” which has a male voice for the check and it also showed the balance to be now correct without any adjustment of the balance control.
I can now report on how these speakers sound with the modifications I’ve made so far. Well they sound better than they ever have sounded! These speakers have been returned to their musical roots and then some. By the way, the Sonicaps have proven to be a major step up from the Solens and were a relatively small investment for a major return and therefore well worth it.
I think these speakers are hard to drive and have had to resurrect an old integrated Sugden solid state amp to do them justice. I’ve another, more modern, solid state amp available to me to try later on but my valve power amp doesn’t perform well with the 66’s at all but will experiment a bit more with it, maybe there is a problem somewhere. Anyone else have problems with driving these speakers?
For the record the following is a list of the mods made so far:
Bass circuit (Solen caps were manufactured in about 1989)
Solen 68uF in series with 1.5R MRA5 (parallel to woofer)
(Solen 68uf // Solen 6uF) in series with 1.0R MRA5 (in other position)
Midrange Circuit
Sonicap 24uF in series with 1.8R MRA5
Sonicap 4uF inseries with 2.7R MRA5
82R MRA12 in parallel with midrange MD500
Tweeter Circuit
Sonicap 4uf
Sonicap 6.2uF
Will get together some of the acoustic measurement results and post these here for further discussion.
DG
Hi Alan,
I’ve removed the 82 ohm from the speaker with the 6.3R MD500 (RH speaker) and listened to the tracks again (solo countertenor with lute). To my surprise the voice came from the centre or very close to it and both speakers sounded the same to me ie no noticeable tone/timbre differences. Well done! It looks as though the slightly different level (ie 1 db under test) of the MD equipped speaker is of no real consequence now ie not noticeable enough to require action at this time. Will, however, listen more and evaluate in more detail with a range of material.
I also checked balance with a “Denon Audio Technical CD” which has a male voice for the check and it also showed the balance to be now correct without any adjustment of the balance control.
I can now report on how these speakers sound with the modifications I’ve made so far. Well they sound better than they ever have sounded! These speakers have been returned to their musical roots and then some. By the way, the Sonicaps have proven to be a major step up from the Solens and were a relatively small investment for a major return and therefore well worth it.
I think these speakers are hard to drive and have had to resurrect an old integrated Sugden solid state amp to do them justice. I’ve another, more modern, solid state amp available to me to try later on but my valve power amp doesn’t perform well with the 66’s at all but will experiment a bit more with it, maybe there is a problem somewhere. Anyone else have problems with driving these speakers?
For the record the following is a list of the mods made so far:
Bass circuit (Solen caps were manufactured in about 1989)
Solen 68uF in series with 1.5R MRA5 (parallel to woofer)
(Solen 68uf // Solen 6uF) in series with 1.0R MRA5 (in other position)
Midrange Circuit
Sonicap 24uF in series with 1.8R MRA5
Sonicap 4uF inseries with 2.7R MRA5
82R MRA12 in parallel with midrange MD500
Tweeter Circuit
Sonicap 4uf
Sonicap 6.2uF
Will get together some of the acoustic measurement results and post these here for further discussion.
DG
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Hi Alan,
Thanks for your knowledgeable and considered reply - much appreciated
I'll endeavour to do as you say and report back with my findings, once I've got a proper handle on what the speakers are doing in their unmodified state.
With the low serial number shown on mine, I feel pretty sure that they are very early ones, but I will look for any dates stamped on the cabinets and let you know.